Solar Thermal Power Plants

Published on May 2016 | Categories: Types, Creative Writing | Downloads: 35 | Comments: 0 | Views: 572
of 80
Download PDF   Embed   Report



Solar thermal power plants
Technology Fundamentals
published in Renewable Energy World 06/2003 pp. 109-113

Many people associate solar electricity generation directly with photovoltaics and not
with solar thermal power. Yet large, commercial, concentrating solar thermal power
plants have been generating electricity at reasonable costs for more than 15 years.
Volker Quaschning describes the basics of the most important types of solar thermal
power plants.

Most techniques for generating electricity from heat need high temperatures to achieve
reasonable efficiencies. The output temperatures of non-concentrating solar collectors
are limited to temperatures below 200°C. Therefore, concentrating systems must be
used to produce higher temperatures. Due to their high costs, lenses and burning
glasses are not usually used for large-scale power plants, and more cost-effective
alternatives are used, including reflecting concentrators.
The reflector, which concentrates the sunlight to a focal line or focal point, has a
parabolic shape; such a reflector must always be tracked. In general terms, a distinction
can be made between one-axis and two-axis tracking: one-axis tracking systems
concentrate the sunlight onto an absorber tube in the focal line, while two-axis tracking
systems do so onto a relatively small absorber surface near the focal point (see Figure

FIGURE 1. Concentration of sunlight using (a) parabolic trough collector (b) linear
Fresnel collector (c) central receiver system with dish collector and (d) central receiver
system with distributed reflectors

The theoretical maximum concentration factor is 46,211. It is finite because the sun is
not really a point radiation source. The maximum theoretical concentration temperature
that can be achieved is the sun’s surface temperature of 5500°C; if the concentration
ratio is lower, the maximum achievable temperature decreases. However, real systems
do not reach these theoretical maxima. This is because, on the one hand, it is not
possible to build an absolutely exact system, and on the other, the technical systems
which transport heat to the user also reduce the receiver temperatures. If the heat
transfer process stops, though, the receiver can reach critically high temperatures.

Parabolic Trough Power Plants

Parabolic trough power plants are the only type of solar thermal power plant technology
with existing commercial operating systems until 2008. In capacity terms, 354 MWe of
electrical power are installed in California, and a plenty of new plants are currently in the
planning process in other locations.
The parabolic trough collector consists of large curved mirrors, which concentrate the
sunlight by a factor of 80 or more to a focal line. Parallel collectors build up a 300–600
metre long collector row, and a multitude of parallel rows form the solar collector field.

The one-axis tracked collectors follow the sun.
The collector field can also be formed from very long rows of parallel Fresnel collectors.
In the focal line of these is a metal absorber tube, which is usually embedded in an
evacuated glass tube that reduces heat losses. A special high-temperature, resistive
selective coating additionally reduces radiation heat losses.
In the Californian systems, thermo oil flows through the absorber tube. This tube heats
up the oil to nearly 400°C, and a heat exchanger transfers the heat of the thermal oil to
a water steam cycle (also called Rankine cycle). A feedwater pump then puts the water
under pressure. Finally, an economizer, vaporizer and superheater together produce
superheated steam. This steam expands in a two-stage turbine; between the highpressure and low-pressure parts of this turbine is a reheater, which heats the steam
again. The turbine itself drives an electrical generator that converts the mechanical
energy into electrical energy; the condenser behind the turbine condenses the steam
back to water, which closes the cycle at the feedwater pump.
It is also possible to produce superheated steam directly using solar collectors. This
makes the thermo oil unnecessary, and also reduces costs because the relatively
expensive thermo oil and the heat exchangers are no longer needed. However, direct
solar steam generation is still in the prototype stage.

Guaranteed Capacity

In contrast to photovoltaic systems, solar thermal power plants can guarantee capacity
(see Figure 2). During periods of bad weather or during the night, a parallel, fossil fuel
burner can produce steam; this parallel burner can also be fired by climate-compatible
fuels such as biomass, or hydrogen produced by renewables. With thermal storage, the
solar thermal power plant can also generate electricity even if there is no solar energy

FIGURE 2. Typical output of a solar thermal power plant with two-hour thermal storage
and backup heater to guarantee capacity

A proven form of storage system operates with two tanks. The storage medium for hightemperature heat storage is molten salt. The excess heat of the solar collector field heats
up the molten salt, which is pumped from the cold to the hot tank. If the solar collector
field cannot produce enough heat to drive the turbine, the molten salt is pumped back
from the hot to the cold tank, and heats up the heat transfer fluid. Figure 3 shows the
principle of the parabolic trough power plant with thermal storage.

FIGURE 3. Schematic of a concentrated solar thermal trough power plant with thermal

Trough Power Plant Efficiencies

The efficiency of a solar thermal power plant is the product of the collector efficiency,
field efficiency and steam-cycle efficiency. The collector efficiency depends on the angle
of incidence of the sunlight and the temperature in the absorber tube, and can reach
values up to 75%. Field losses are usually below 10%. Altogether, solar thermal trough
power plants can reach annual efficiencies of about 15%; the steam-cycle efficiency of
about 35% has the most significant influence. Central receiver systems such as solar
thermal tower plants can reach higher temperatures and therefore achieve higher

Solar Thermal Tower Power Plants

In solar thermal tower power plants, hundreds or even thousands of large two-axis
tracked mirrors are installed around a tower. These slightly curved mirrors are also
called heliostats; a computer calculates the ideal position for each of these, and a motor
drive moves them into the sun. The system must be very precise in order to ensure that
sunlight is really focused on the top of the tower. It is here that the absorber is located,
and this is heated up to temperatures of 1000°C or more. Hot air or molten salt then
transports the heat from the absorber to a steam generator; superheated water steam is
produced there, which drives a turbine and electrical generator, as described above for
the parabolic trough power plants. Only two types of solar tower concepts will be
described here in greater detail.

Open Volumetric Air Receiver Concept

The first type of solar tower is the open volumetric receiver concept (see Figure 4a). A
blower transports ambient air through the receiver, which is heated up by the reflected
sunlight. The receiver consists of wire mesh or ceramic or metallic materials in a
honeycomb structure, and air is drawn through this and heated up to temperatures
between 650°C and 850°C. On the front side, cold, incoming air cools down the receiver
surface. Therefore, the volumetric structure produces the highest temperatures inside
the receiver material, reducing the heat radiation losses on the receiver surface. Next,
the air reaches the heat boiler, where steam is produced. A duct burner and thermal
storage can also guarantee capacity with this type of solar thermal power plant.

Pressurized Air Receiver Concept

The volumetric pressurized receiver concept (see Figure 4b) offers totally new
opportunities for solar thermal tower plants. A compressor pressurizes air to about 15
bar; a transparent glass dome covers the receiver and separates the absorber from the
environment. Inside the pressurized receiver, the air is heated to temperatures of up to
1100°C, and the hot air drives a gas turbine. This turbine is connected to the
compressor and a generator that produces electricity. The waste heat of the gas turbine
goes to a heat boiler and in addition to this drives a steam-cycle process. The combined
gas and steam turbine process can reach efficiencies of over 50%, whereas the efficiency
of a simple steam turbine cycle is only 35%. Therefore, solar system efficiencies of over
20% are possible.

FIGURE 4. Schematic of two types of solar thermal tower power plant, showing (a) an
open volumetric receiver with steam turbine cycle and (b) a pressurized receiver with
combined gas and steam turbine cycle

Comparing Trough and Tower

In contrast to the parabolic trough power plants, no commercial tower power plant exists
at present. However, prototype systems – in Almería, Spain, in Barstow, California, US,
and in Rehovot, Israel – have proven the functionality of various tower power plant
The minimum size of parabolic trough and solar tower power plants is in the range of 10
MWe. Below this capacity, installation and O&M costs increase and the system efficiency
decreases so much that smaller systems cannot usually operate economically. In terms
of costs, the optimal system size is in the range of 50–200 MWe.

Dish-Stirling Systems

So-called Dish–Stirling systems can be used to generate electricity in the kilowatts
range. A parabolic concave mirror (the dish) concentrates sunlight; the two-axis tracked
mirror must follow the sun with a high degree of accuracy in order to achieve high
efficiencies. In the focus is a receiver which is heated up to 650°C. The absorbed heat
drives a Stirling motor, which converts the heat into motive energy and drives a
generator to produce electricity. If sufficient sunlight is not available, combustion heat
from either fossil fuels or biofuels can also drive the Stirling engine and generate
electricity. The system efficiency of Dish–Stirling systems can reach 20% or more. Some
Dish–Stirling system prototypes have been successfully tested in a number of countries.
However, the electricity generation costs of these systems are much higher than those
for trough or tower power plants, and only series production can achieve further
significant cost reductions for Dish–Stirling systems.

Dish-Stirling prototype systems in Spain

Solar Chimney Power Plants

All three technologies described above can only use direct normal irradiance. However,
another solar thermal power plant concept – the solar chimney power plant – converts
global irradiance into electricity. Since chimneys are often associated negatively with
exhaust gases, this concept is also known as the solar power tower plant, although it is
totally different from the tower concepts described above. A solar chimney power plant
has a high chimney (tower), with a height of up to 1000 metres, and this is surrounded
by a large collector roof, up to 130 metres in diameter, that consists of glass or resistive
plastic supported on a framework (see artist’s impression). Towards its centre, the roof
curves upwards to join the chimney, creating a funnel.
The sun heats up the ground and the air underneath the collector roof, and the heated
air follows the upward incline of the roof until it reaches the chimney. There, it flows at
high speed through the chimney and drives wind generators at its bottom. The ground
under the collector roof behaves as a storage medium, and can even heat up the air for
a significant time after sunset. The efficiency of the solar chimney power plant is below

2%, and depends mainly on the height of the tower, and so these power plants can only
be constructed on land which is very cheap or free. Such areas are usually situated in
desert regions.
However, the whole power plant is not without other uses, as the outer area under the
collector roof can also be utilized as a greenhouse for agricultural purposes. As with
trough and tower plants, the minimum economical size of solar chimney power plants is
also in the multi-megawatt range.

Artist’s impression of a 5 MW solar chimney power plant SCHLAICH BERGERMANN

Electricity Generation Costs

Due to the poor part-load behaviour of solar thermal power, plants should be installed in
regions with a minimum of around 2000 full-load hours. This is the case in regions with a
direct normal irradiance of more than 2000 kWh/m2 or a global irradiance of more than
1800 kWh/m2. These irradiance values can be found in the earth’s sunbelt; however,
thermal storage can increase the number of full-load hours significantly.
The specific system costs are between €2000/kW and €5000/kW depending on the
system size, system concept and storage size. Hence, a 50 MWe solar thermal power
plant will cost €100–250 million. At very good sites, today’s solar thermal power plants
can generate electricity in the range of €0.15/kWh, and series production could soon
bring down these costs below €0.10/kWh.
The potential for solar thermal power plants is enormous: for instance, about 1% of the
area of the Sahara desert covered with solar thermal power plants would theoretically be
sufficient to meet the entire global electricity demand. Therefore, solar thermal power
systems will hopefully play an important role in the world’s future electricity supply.

U.S. DOI approves large solar power


Secretary of the Interior Sally Jewell has
announced the approval of two major solar energy
projects: the 350 MW Midland Solar Energy Project
in Nevada and the 100 MW Quartzsite
Concentrating Solar Power Project in Arizo

The Quartzsite Solar Project, located
in La Paz County, Ariz., was proposed
by Quartzsite Solar Energy LLC, a
subsidiary of California-based Solar
Reserve LLC. The proposed solar
facility is a concentrated solar power
design that would cover 1,600 acres
of Bureau of Land Management land.
As part of President Obama’s all-ofthe-above energy strategy to continue
production, Secretary of the Interior
Sally Jewell today announced the
approval of three major renewable
energy projects that, when built, are
expected to deliver up to 520
megawatts to the electricity grid –
enough to power nearly 200,000
homes – and to help support more
than 900 jobs through construction
and operations.
The 350-megawatt Midland Solar
Energy Project and the 70-megawatt
New York Canyon Geothermal Project
are located in Nevada, and the 100megawatt Quartzsite Solar Energy
Project is located in Arizona.
“These projects reflect the Obama

expand responsible domestic energy
production on our public lands and
portfolio,” Secretary Jewell said.
“Today’s approvals will help bolster
rural economies by generating good
jobs and reliable power and advance
our national energy security.”
Since 2009 Interior has approved 25
utility-scale solar facilities, 9 wind
farms and 11 geothermal plants, with
associated transmission corridors
and infrastructure to connect to
established power grids. When built,
these projects could provide more
than 12,500 megawatts of power, or
enough electricity to power more than
4.4 million homes, and support an
estimated 17,000 construction and
operations jobs.
Interior’s Bureau of Land Management
(BLM) has identified an additional 15
active renewable energy proposals
slated for review this year and next.
The BLM identified these projects
through a process that emphasizes
early consultation and collaboration
with its sister agencies at Interior –
the Bureau of Indian Affairs, the U.S.
Fish and Wildlife Service, and the
“The President has called for America
to continue taking bold steps on clean
energy,” said the BLM Principal
Deputy Director Neil Kornze. “Our
helped us do just that, paving the way
for responsible development of utilityscale renewable energy projects in
the right way and in the right places.”
extensive environmental review and
public comment. The companies
agreed to undertake significant
mitigation efforts to minimize impacts
to wildlife, water, historical, cultural

and other resources.
The Quartzsite Solar Project, located
in La Paz County, Arizona, about was
proposed by Quartzsite Solar Energy,
LLC, a subsidiary of Solar Reserve,
LLC (Santa Monica, CA). The 100megawatt
concentrating solar “power tower”
technology to drive steam turbine
generators with heliostats on 1,600
acres of BLM-managed lands.

The Quartzsite Solar Energy Project
will employ dry-cooling technology,
which requires a fraction of the water
needed for wet-cooling. The project is
expected to create 438 jobs during
peak construction and 47 full-time

operations and maintenance jobs.
When operational, the facility will
generate enough clean power to meet
the needs of an estimated 30,000
homes. Click here for a fact sheet on
and here for
The Midland Solar Project is a 350megawatt solar photovoltaic facility.
Proposed by Boulder Solar Power,
LLC, the project will be built on
private lands about 7 miles southwest
from Boulder City, Nevada and will
cross 76 acres of federal transmission
corridor. The project will provide
enough electricity to power about
105,000 homes and generate a peak
construction workforce of about 350
employees and up to 10 permanent
jobs. Boulder Solar Power, LLC
worked closely with the BLM, U.S.
Fish and Wildlife Service, and Nevada
Department of Wildlife to develop
measures that will avoid, minimize
and mitigate potential impacts.
The project’s infrastructure, for
example, was minimized to reduce
ground disturbance. Less than 6.7
acres of native plant communities,
which provide habitat to nesting
migratory birds, will be eliminated as
a result of the proposed facility. In
addition, the project will obtain water
from the existing Boulder City Public
Works Department main pipeline, so
that surface waters will not be
diverted from areas of perennial flow
or ephemeral washes, or from
downstream habitats that depend on
that water. Click here for a fact sheet
on the Midland Solar Project
and here for
The New York Canyon Geothermal
Project and electrical transmission
facility will be built on 15,135 acres of
land managed by the BLM about 25

miles east of Lovelock, Nevada in
Development Company, LLC, a
subsidiary of TerraGen Power, LLC,
will build the 70-megawatt project and
associated 230-kilovolt electrical line.
The project will provide enough
electricity to power about 60,000
homes and create an estimated 150
peak construction jobs and 16 fulland part-time operational jobs. The
BLM worked closely with its partners
environmental impacts. For example,
a Bird and Bat Conservation Strategy
was developed to assess the area’s
avian wildlife and reduce impacts on
these populations. In addition, there
are no listed, proposed or candidate
threatened or endangered species
Clickhere for a fact sheet on the New
York Canyon Geothermal Project
and here for a map.
For more information on BLM’s
approved and pending renewable
energy projects,visit the website.
Tags: concentrated solar energy, Concentrating Solar
Power, CSP, solar power, solar
energy,U.S., SolarReserve,

Careers in Solar Power
Sunlight is the most abundant source of potential energy on the planet. If harnessed properly,
sunlight could easily exceed current and future electricity demand. According to the U.S. Department
of Energy, every hour, enough energy from the sun reaches Earth to meet the world's energy usage
for an entire year.


Creating solar power by converting sunlight into electricity would lower

emissions from electricity generation and decrease long-term energy costs. As solar power becomes
more cost-effective, it has the potential to make up a larger share of growing U.S. energy needs. And
as it expands in usage, there will be a growing need for more workers—manufacturing workers to
make solar panels, construction workers to build power plants, solar photovoltaic installers to install
solar panels, and so on.
This article provides information on the process of generating solar power and details various
occupations in the solar industry. The first section details a brief history of solar power in the United
States, followed by an overview of how solar power is generated, which entities use it, and the
technology involved in supplying solar power.
The second section provides occupational information highlighting a brief job description of several
noteworthy occupations that are related to solar power; the credentials needed to work in the
occupation, such as education, training, certification, or licensure; and wage data. Occupations are
listed under relevant occupational categories such as manufacturing, construction, installation, etc.
Using the data from the U.S. Bureau of Labor Statistics (BLS), Occupational Employment Statistics
program and the Solar Foundation, this article represents the second publication in the Bureau's
green careers series.

Growth of solar power in the United States
Because of a growing interest in renewable energy and the increasingly competitive prices of
alternative energy sources, solar power has received a lot of attention over the past several years.
However, solar power generation itself is not new; it has been used for more than half a century,
mostly on a small scale or for specialized purposes, such as generating electricity for spacecraft and
satellites or for use in remote areas. Large scale solar generation was mostly developed in the 1970s
and 1980s, and is considered a clean energy because of its lack of emissions. Continued growth is
expected because solar power has many environmental benefits and is decreasing in price, which will
allow it to become increasingly competitive with fossil fuels.
The relatively steep cost of solar power compared with traditional sources of electricity generation is
caused by the high cost of manufacturing and installing solar panels. However, the cost of solar
power has been trending downward as technology has improved and manufacturers have learned
how to improve production efficiency. In addition, as solar power generation becomes more
widespread, the cost of installing solar-generation capacity will continue to fall. And as the price of
fossil fuels increases, solar power will become more cost effective relative to traditional sources of
The solar power industry has experienced rapid growth in the past decade. According to the Solar
Energy Industries Association (SEIA), total U.S. solar electric capacity surpassed 2,000 megawatts in

2009, enough to power over 350,000 homes. In 2009 alone, the residential market doubled in size
and three new concentrating solar power (CSP) plants opened in the United States, increasing the
solar electric market by 37 percent.[2] Despite this growth, solar power is still a minute portion of total
energy generated in the country. In 2009, solar power provided less than 1 percent of total electricity
generated in the United States.


The Bureau of Labor Statistics (BLS) does not currently have employment data for the solar power
industry.[4] However, the Solar Foundation, a nonprofit organization that promotes the use of solar
energy technologies to help meet the world's energy needs, estimates that in August 2010, 93,000
workers spent more than half of their work hours on projects related to solar power. [5] The solar
industry includes workers in science, engineering, manufacturing, construction, and installation.
Scientists, for example, are involved in the research and development of new and more efficient
materials, and engineers design new systems and improve existing technologies. Manufacturing
workers make the equipment used in solar power generation, such as mirrors and panels.
Construction workers build solar power plants. Electricians, plumbers, and solar photovoltaic installers
install residential and commercial solar projects. The Solar Foundation estimates that the largest
growth in the solar industry in 2011 will be in occupations in solar installation, including photovoltaic
installers and electricians and roofers with experience in solar installation.


Map 1. Available solar power energy in the United States

Solar power generation
Solar power is a versatile means of generating electricity. It can be used for such purposes as heating
water, heating and air conditioning homes and commercial buildings, and powering streetlights.
Because sunlight is readily available almost everywhere and doesn't require fuel or a connection to a
power grid (an interconnected network used to deliver electricity from suppliers to consumers), solar
power is particularly useful for supplying power to remote areas and to some portable devices.
Solar power is used to generate large amounts of power on a utility scale and to supply individual
residences and businesses with electricity. This report focuses mainly on utility-scale, commercial, and
residential solar power.

Utility-scale solar power plants supply large amounts of electricity to the power grid along with
traditional sources of power, such as coal and natural gas plants. Solar power plants typically
generate several megawatts of power, comparable to small or medium coal- or gas-fired plants.

Plants only now in the planning stages are expected to produce several hundred megawatts, [7] which
would be comparable to a medium to large coal plant or nuclear plant.

Commercial solar power is used by business establishments, such as office buildings, warehouses,
and retail stores, which are able to install large groups of solar panels known as photovoltaic (PV)
arrays, on unused land, rooftops, or parking structures. These panels supplement the building's
power supply, and, at times, may generate more electricity than the building consumes. Often, this
excess power can be sold back to the local utility company.

Residential solar power is generated by homeowners who have solar panels installed on their roofs in
order to provide power to their homes. This form of solar power is increasing in popularity.
Residential solar power usually must be supplemented by traditional electricity from the power grid to
provide additional electricity when the solar panels cannot meet energy needs, such as when it is
nighttime or extremely cloudy.
Although some areas of the United States are better suited for solar power than others, solar energy
can be harnessed in any geographic area because of the sun's vast reach. In 2009, California had by
far the most solar power capacity at 1102 megawatts, followed by New Jersey with 128
megawatts.[8] Nearly all states in the United States receive more sunlight per square mile than
Germany, the world's leading producer of solar energy.[9] Manufacturing of solar power equipment
and components is located throughout the United States, with large plants in Massachusetts,
Michigan, Ohio, Oregon, California, Wisconsin, Tennessee, New Mexico, Colorado, Georgia, and
Texas. Other large solar panel manufacturing facilities are planned to begin construction over the
next few years in many states.

Methods of solar power generation
There are two basic methods for generating electricity from solar power. The first method uses
photovoltaic (PV) solar panels to generate electricity directly from sunlight. The second method is
known as concentrating solar power (CSP) and converts sunlight into heat to produce steam, which is
then fed through conventional steam-turbine generators to generate electricity.
Photovoltaic panels have traditionally been used for smaller scale electricity generation, particularly
for residential or commercial use in individual buildings or complexes, while CSP is used for utilityscale electricity generation in solar power plants. However, photovoltaic solar plants recently started
generating electricity in California, Illinois, New Jersey, Nevada, and Florida. CSP is also being
adapted for smaller scale electricity generation.

Photovoltaic solar power
Modern photovoltaic solar cells were developed in the 1940s and 1950s, and the technology has
evolved rapidly over the past several decades. The space programs of the United States and the
Soviet Union first used photovoltaic cells as a source of energy to generate electricity for satellites
and spacecraft. Solar energy is still used to power the International Space Station and the vast
majority of satellites. Photovoltaic panels have also proven useful for providing electricity to remote
locations that are not supplied by a local electric utility.

Photovoltaic power uses solar cells that convert the energy of sunlight directly into electricity through
the photovoltaic effect. (See diagram 1.) The photovoltaic effect is a process by which light from the
sun hits a solar cell and is absorbed by a semiconducting material such as crystalline silicon. The
photons in the sunlight knock electrons loose from their atoms, allowing them to flow freely through
the material to produce direct electric current (DC) electricity. For household or utility use, an inverter
must be used to convert the electricity to alternating current (AC).
The individual solar cells are arranged onto a solar panel. The solar panel is coated in glass or
another laminate to protect the cells from damage. A new technology allows solar panels to be placed
on a thin strip of backing, usually aluminum, and covered with a plastic film, which decreases the
weight and cost of a solar panel. These thin-film solar panels are becoming more common, although
traditional glass- or laminate-coated panels continue to make up the majority of the solar panel

Usually, several panels are arranged into an array, which can be scaled to produce enough capacity
to generate the desired amount of power. A single cell can produce enough electricity to power a
small device, such as an emergency telephone, but larger arrays are required to power a house or
building. Utility-scale photovoltaic plants consisting of thousands of solar panels are a more recent

Concentrating solar power
The first large-scale solar power plants in
the United States were concentrating solar
power (CSP) plants. Built in the California
desert in the 1980s and 1990s, these
plants are still among the largest, most
powerful solar generating plants in the
world. Several plants have also been in
operation since the 1980s in the
southwestern United States, and many
more are currently in the planning and

construction stages. Although there are several different CSP technologies, they all involve reflecting
sunlight onto a focal point that contains a heat-transfer material. The heat-transfer material, usually
synthetic oil or molten salt, is collected in a heat storage unit and eventually used to create steam
that powers conventional generators. One advantage of CSP is that at night or on extremely cloudy
days, the conventional generators can be run on natural gas or petroleum, allowing the plant to
continue to generate power when the sun is not shining.
All CSP plants consist of arrays of mirrors. The first type of CSP technology (still used today) works
through the use of parabolic troughs, long, curved mirrors that move to follow the path of the sun,
and focus the sun's heat onto a tube in front of the mirror. This dramatically increases the
temperature of the heat-transfer material, which in turn boils water and creates steam that drives a
generator. (See diagram 2.)

Solar power towers, another type of CSP technology, were first used at experimental power plants in
the California desert during the 1980s and 1990s; improved solar power towers are currently being
developed for newer CSP plants. In these plants, a large array of flat mirrors (called heliostats) is
focused on a central tower that contains the heat-transfer material. The transfer material is pumped
into storage tanks that can contain the heat for up to a day. It is then passed through a heat
exchanger, where it produces steam that drives the generators. (See diagram 3.)

Engineers and scientists have recently developed a new form of CSP technology called the dish

system. In this system, the mirrors are arranged in a parabolic shape, similar to that of a satellite
dish, which focuses the heat onto a central receiver mounted above the center of the dish. (See
diagram 4.) The receiver contains an engine known as a Stirling engine that converts heat to
mechanical power by compressing a cold fluid, which could be water or synthetic oil. The heating of
the fluid causes it to expand through a turbine or a piston, which produces mechanical power. An
electric generator or alternator then converts the mechanical power into electricity. Large scale
electricity is produced by arranging several dishes into a larger array. New power plants using this
technology have recently been approved for construction in California.

The linear Fresnel system is one of the newest CSP technologies. This system is similar to the
parabolic trough system, but it uses multiple rows of flat mirrors to focus light onto a set of tubes,
increasing the temperature of the heat-transfer fluid. (See diagram 5.) The advantage of the linear
Fresnel system is that it is much less expensive to manufacture flat mirrors than curved ones.

Solar water heating
Solar power can be used for another important purpose: the heating of water for residential,
commercial, or industrial purposes. Residential solar water heaters generally consist of roof-mounted
solar water collectors that directly heat water using sunlight or indirectly heat water by using solar

collectors to increase the temperature of a heat-transfer material and pump it to a heat exchanger,
which creates the hot water. Solar water heating systems may be used to provide hot water to a
home, a swimming pool, or for commercial purposes.
Solar water heating systems are best suited to warm climates, but they can be effective in colder
climates as well. Most systems provide a majority of a home's hot water needs, but are backed up by
a conventional water heater for times when there is a lack of sunlight.
Usually, solar installers mount the thermal collectors for solar water heating using similar equipment
as used to install photovoltaic panels, but thermal collectors are used instead of panels. A plumber is
needed to connect water pipes to the plumbing system of the house, pool, or commercial building.

Occupations in solar power
The solar power industry employs a wide range of occupations in a number of major industry
segments: research and development, manufacturing of solar power materials, construction of solar
power plants, operation of solar power plants, and solar power installation and maintenance. Sales
occupations are also integral to the solar power products industry.
Following are descriptions of the most
common jobs in the solar power industry;
for each occupation, job duties are listed,
along with the credentials needed for the
occupation, including education, training,
certification, or
licensure. Certification demonstrates
competency in a skill or set of skills,
typically through work experience,
training, the passage of an examination,
or some combination of the
three. Licensing is done by individual
states, and typically requires the passage
of an examination in addition to fulfillment of eligibility requirements, such as a minimum level of
education, work experience, training, or the completion of an internship, residency, or apprenticeship.
In addition, wage data are included in the occupation descriptions. Although BLS does not have wage
data specifically for occupations in the solar industry, BLS is currently in the process of collecting data
to measure green jobs. This is expected to be available in 2012. The wages listed represent the larger
industry or industry group that would employ solar power workers, when applicable. Wage data do
not include benefits or other compensation.
The majority of the occupations listed here are not specific to the solar power industry—they exist in
many other industries as well. Although many of these occupations require special skills unique to
solar power, skills can be acquired in other industries in most cases. For many positions, experience
in other industries is desired by employers in the solar power industry. For example, solar
photovoltaic installers need to have specialized knowledge and training, but many installers have
previous experience as roofers, electricians, or construction workers.

Occupations in scientific research
Solar power is still gaining popularity and acceptance, so research and development are key aspects
of the industry. Continued research and increased returns to scale as production has increased have
led to many developments that have decreased costs while increasing efficiency, reliability, and
aesthetics. For example, new materials have been developed that allow for low-cost and lightweight
thin-film solar panels that are less expensive to produce and easier to transport than glass- or
laminate-coated solar panels.
Occupations in scientific research and development have become increasingly interdisciplinary, and as
a result, it is common for physicists, chemists, materials scientists, and engineers to work together as
part of a team. Most scientists in the solar industry work in an office or laboratory and also spend
some time in manufacturing facilities with engineers and processing specialists.

Job duties
Physicists observe, measure, interpret, and develop theories to explain physical phenomena using
mathematics. In the solar power industry, physicists work with chemists, materials scientists, and
engineers to improve the efficiency of solar panels. Physicists also find new materials to use for solar
panel generation, such as the thin-film photovoltaic solar panels.

Chemists investigate the properties, composition, and structure of matter and the laws that govern
the reactions of substances to each other. Using this knowledge, chemists in the solar power industry
are able to improve on solar cell design, develop new materials for making solar cells, or improve
existing materials. They typically focus on semiconducting materials, which are usually silicon-based
materials or organic compounds, because most solar panels are made of semiconducting materials
and some newer thin-film panels are made out of organic materials.

Materials scientists study the structures and chemical properties of various materials to develop new
products or enhance existing ones. Current research in the solar power field is focused on developing
new materials, especially thin-film cells, and decreasing the cost of photovoltaic panels. Materials
scientists are also seeking to increase solar panel efficiency. Efficiency refers to the percentage of
available energy that is actually harnessed by the solar cells. Most modern solar cells can only harvest
about 10 to 15 percent of solar energy, with some types of panels capable of 25 to 30 percent
efficiency. Finally, material scientists are seeking to create building-integrated solar energy
technologies that address common complaints about solar panels taking away the aesthetic appeal of
a building because of their large and bulky nature.

A doctoral degree is a necessity for scientists that conduct original research and develop new
products; however, some workers may enter the scientific fields with a bachelor's or master's degree.
Computer skills are essential for scientists to perform data analysis, integration, modeling, and
testing. Certification or licensure is not necessary for most of these scientists.

BLS does not currently have wage data specific to the solar power industry. The table that follows
shows wages for selected scientists for May 2010. The wages are median annual wages for the
United States as a whole; wages vary by employer and location.

Selected scientific occupations

Median annual wages, 2010(1)

Materials scientists
(1) The Occupational Employment Statistics data are available at The data do not include benefits.

Occupations in solar power engineering
Engineers apply the principles of science and mathematics to develop economical solutions to
technical problems. Their work is the link between scientific research and commercial applications.
Many engineers specify precise functional requirements, and then design, test, and integrate
components to produce designs for new products. After the design phase, engineers are responsible
for evaluating a design's effectiveness, cost, reliability, and safety. Engineers use computers
extensively to produce and analyze designs, and for simulating and testing solar energy systems.
Computers are also necessary for monitoring quality control processes. Computer software developers
design the software and other systems needed to manufacture solar components, manage the
production of solar panels, and control some solar generating systems.
Most engineers work in offices, laboratories, or industrial plants. Engineers are typically employed by
manufacturers of solar equipment and may travel frequently to different worksites, including to plants
in Asia and Europe.
Engineers are one of the most sought-after occupations by employers in the solar power industry.
According to the Solar Foundation, 53 percent of manufacturing firms reported difficulty in hiring
qualified engineers in 2010.

Job duties
Materials engineers are involved in the development, processing, and testing of the materials for use
in products that must meet specialized design and performance specifications. In the solar industry,
they work with semiconductors, metals, plastics, glass, and composites (mixtures of these materials)
to create new materials that meet electrical and chemical requirements of solar cells. They create and
study materials at an atomic level, using advanced processes to replicate the characteristics of those
materials and their components using computer modeling programs.

Chemical engineers apply the principles of chemistry to design or improve equipment or to devise
processes for manufacturing chemicals and products. In the solar power industry, they design
equipment and processes for large-scale manufacturing, plan and test methods of manufacturing
solar cells, and supervise the production of solar cells. Chemical engineers in the solar industry
typically focus on semiconductors or organic chemistry, since most solar panels are made of
semiconducting materials and some newer thin-film panels are made out of organic materials.

Electrical engineers design, develop, test, and supervise the manufacture of electrical components.
They are responsible for designing the electrical circuitry of solar panels and supporting devices for
panels, such as inverters and wiring systems.

Industrial engineers determine the most effective ways to use the basic factors of production—
people, machines, materials, information, and energy—to make a product or provide a service. In the
solar power industry, they are concerned primarily with increasing productivity through the
management of people, the use of technology, and the improvement of production methods of solar
cells or mirrors. To maximize efficiency, industrial engineers study the product requirements carefully
and design manufacturing and information systems with the help of mathematical models.

Mechanical engineers research, design, develop, manufacture, and test tools, engines, machines, and
other mechanical devices. Engineers in the solar power industry work on the machines used in the
manufacturing of solar panels. In the United States, solar photovoltaic manufacturing is highly
automated. Machines do the majority of work: cutting semiconducting materials, such as crystalline
silicon, into wafers, turning them into solar cells, and assembling the solar cells into solar panels.
Besides machines, mechanical engineers also design and test the electric generators and pumps that
are used in concentrating solar power plants.

Computer software developers are computer specialists who design and develop software used for a
variety of purposes. In the solar power industry, computer software is used in forecasting weather
and sunlight patterns to assess the feasibility and cost of generating solar power in a particular area.
In power plants, software is used to monitor the equipment and to adjust the direction of mirrors or
photovoltaic panels so that the maximum amount of energy is captured as the sun moves in the sky.
Software developers are responsible for updating, repairing, expanding, and modifying existing

Engineering technicians assist engineers with solving technical problems in research, development,
manufacturing, construction, inspection, and maintenance. Their work is more narrowly focused and
application-oriented than that of engineers or scientists. Engineering technicians who work in the
research and development of solar panels or machines will build or set up equipment, prepare and
conduct experiments, collect data, and calculate or record results. They may also help engineers or
scientists to make prototypes of newly designed equipment or assist with computer-aided design and
drafting (CADD) equipment.

Engineers typically enter the solar industry with a bachelor's degree in engineering. However,
because of the complexity of some systems, a significant number of jobs require a master's or
doctoral degree. Engineers are expected to complete continuing education and keep up with rapidly
changing technology.
Certifications are usually required and depend on the systems used by a particular manufacturer.
Licensure as a professional engineer (PE) is desirable and often required, depending on an engineer's
Entry-level engineers may be hired as interns or junior team members and work under the close
supervision of senior or supervisory engineers. As they gain experience, they are assigned more
complex tasks and are given greater independence and leadership responsibilities.
Software developers typically have at least a bachelor's degree in computer science or a related
discipline, combined with experience in computer programming and software design.

Engineering technicians typically have an associate's degree or certification from a community college
or technical school. Technicians participate in on-the-job training and are closely supervised by

BLS does not currently have wage data specific to the solar power industry. However, BLS does have
wage data for the Semiconductor and Other Electronic Component Manufacturing industry group,
which includes production of solar panels. The following table shows BLS data for selected
occupations in this industry group for May 2010. The wages shown are median annual wages for the
United States as a whole; wages vary by employer and location.
Selected engineering and computer occupations in the semiconductor and other electronic

Median annual

component manufacturing industry group
Materials engineers
Chemical engineers
Electrical engineers
Industrial engineers
Mechanical engineers
Software developers, applications
Electrical and electronics engineering technicians
(1) The Occupational Employment Statistics data are available at The data do not include benefits.

Occupations in manufacturing for solar power
Manufacturing in the solar industry focuses on three technologies: concentrating solar power (CSP),
photovoltaic solar power, and solar water heating. However, the vast majority of solar manufacturing
firms focus mainly on photovoltaic solar power and producing photovoltaic panels. The production
process for photovoltaic panels is more complex than for CSP components, and it involves
complicated electronics. Making photovoltaic panels requires the work of many skilled workers,
including semiconductor processors, computer-controlled machine tool operators, glaziers, and
coating and painting workers. The manufacture of CSP mirrors includes many of the same

Job duties
Semiconductor processors are workers who oversee the manufacturing process of solar cells.
Semiconductors are unique substances, which act as either conductors or insulators of electricity,
depending on the conditions. Semiconductor processors turn semiconductors into photovoltaic cells.
The process begins with the production of cylinders of silicon or other semiconducting materials,
which are called ingots. The ingots are sliced into thin wafers using automated equipment, and are


sometimes polished. The wafers are then connected to metal strips and placed into the cells. These
cells are then arranged into larger solar panels.
The electrical circuitry of solar cells is very small, and microscopic contamination can render the cell
useless. Because of this, most of the manufacturing processes are automated, and it is important to
have workers to monitor the equipment and make adjustments as necessary. They also perform
necessary maintenance and repairs on equipment. Semiconductor processors test completed cells and
perform diagnostic analyses. Workers are required to wear special lightweight outer garments known
as "bunny suits" and spend most of their day working in clean rooms to prevent contamination of the
cells and circuitry.

Computer-controlled machine tool operators are workers who run computer numerically controlled
(CNC) machines, a machine tool that forms and shapes solar mirror or panel components. Some of
the more highly trained CNC workers also program the machines to cut new pieces according to
design schematics. CNC operators use machines to mass-produce components that require highly
precise cutting. In the solar power industry, they manufacture precisely designed mirrors for CSP
plants and many of the components of photovoltaic panels.

Welding, soldering, and brazing workers apply heat to metal pieces during the manufacturing
process, melting and fusing them to form a permanent bond. Welders join two or more pieces of
metal by melting them together. Soldering and brazing workers use a metal with a lower melting
point than that of the original piece, so only the added metal is melted, preventing the piece from
warping or distorting. Solar panels are made up of many small cells that are soldered to electric
circuitry. This process may be automated,
with workers monitoring the machines.

Glaziers are responsible for selecting,
cutting, installing, replacing, and removing
glass or glass-like materials. Photovoltaic
panels are placed in an aluminum frame
and are typically encased in glass or
laminates to protect them from the
elements. The glaziers are responsible for
measuring and cutting the glass or
laminate to cover the panel; securing it in
place; and sealing it using rubber, vinyl, or silicone compounds. It is important to prevent the cover
from cracking or scratching thereby reducing the efficiency of the solar panel.
CSP plants are made up of many highly reflective mirrors manufactured to exact specifications. Many
of these plants use curved mirrors, which are challenging to produce. Glaziers are instrumental in the
manufacturing, installation, and maintenance of these mirrors. Glaziers ensure the mirrors maintain
maximum reflectivity in order to perform at desired levels. Because these mirrors are located
outdoors and are expensive to make, glaziers must often refinish and refurbish them. Mirrors also
break frequently, and glaziers produce the replacements.

Coating and painting machine setters, operators, and tenders apply coatings to solar panels, which
can be a complicated process that must be done with a high level of precision. Mirrors in CSP plants
are typically coated to protect them from the environment and to make them resistant to scratches
and corrosion. Solar photovoltaic panels are also covered in protective coatings, and these coatings

increase the efficiency of the panels. Special coatings, such as titanium oxide, make solar panels less
reflective and therefore able to absorb more sunlight (or lose less sunlight.)
Before painting or coating a mirror or panel, workers prepare the surface by sanding or grinding away
any imperfections. After preparing the surface, it is carefully cleaned to prevent any dust or dirt from
becoming trapped under the coating. The coating is then applied by spraying it onto the panel. Many
manufacturers apply coatings through an automated process. It is the workers' job to set up the
systems, add solvents, monitor the equipment, and feed the pieces through the machines.
Coating and painting workers may be exposed to dangerous fumes from paint and coating solutions
and other hazardous chemicals. Workers are usually required to wear masks and special suits to
protect them from the fumes produced by paint, solvents, and other chemicals.

Electrical and electronics installers and repairers work on a number of the complex electronic
equipment that the solar industry depends on for a variety of functions. Manufacturers use industrial
controls to automatically monitor and direct production processes on the factory floor.

Electrical and electronic equipment assemblers put together the final products and the components
that go into them. They are responsible for assembling the complex electrical circuitry in a
photovoltaic panel, as well as assembling the components, such as inverters or controls, that connect
to solar panels. Many of these assemblers operate automated systems to assemble small electronic
parts that are too small or fragile for human assembly.

Industrial production managers plan, direct, and coordinate work on the factory floor. They determine
which machines will be used, whether new machines need to be purchased, when overtime shifts are
necessary, and how to improve the production process. They keep production runs on schedule, and
are responsible for solving problems that could jeopardize the quality of the components.

The level and type of training necessary for occupations in the solar power manufacturing process
varies. Most production workers are trained on the job and gain expertise with experience. Workers in
more skilled positions, such as computer-controlled machine tool operators, may attend formal
training programs or apprenticeships. Experience working with electronics or semiconductors may be
helpful for some of these occupations. Industrial production managers are typically required to have
college degrees in business administration, management, industrial technology, or engineering.
Industrial production managers are typically required to have college degrees in business
administration, management, industrial technology, or engineering.

BLS does not track wage data specific to the solar power industry. However, BLS does track wage
data for the Semiconductor and Other Electronic Component Manufacturing industry group, which
includes production of solar panels. The following table shows BLS data for selected occupations in
this industry group for May 2010. The wages shown are median annual wages for the United States
as a whole; wages vary by employer and location.
Selected occupations in the semiconductor and other
electronic component manufacturing industry group

Median annual wages, 20

Selected occupations in the semiconductor and other
electronic component manufacturing industry group

Median annual wages, 20

Semiconductor processors
Computer-controlled machine tool operators, metal and plastic
Welders, cutters, solderers, and brazers
Coating, painting, and spraying machine setters, operators, and tenders
Electrical and electronics repairers, commercial and industrial equipment
Electrical and electronic equipment assemblers
Industrial production managers
(1) The Occupational Employment Statistics data are available at The data do not include benefits.
(2) Wage data are not available for the industry group specified. Wages listed are for the occupation as a whole.

Occupations in solar power plant development
Building a solar power plant is complex and site selection requires years of research and planning.
The proposed site must meet several criteria: large, relatively flat site, adequate sunlight, and
minimal environmental impact once built. Prior to beginning construction on a new solar plant, real
estate brokers and scientists must ensure the site is suitable and that the proper federal, state, and
local permits are obtained for construction of a power plant.

Job duties
Real estate brokers are instrumental in procuring land on which to build power plants. They are
responsible for obtaining the land by purchasing or leasing it from land owners. Real estate brokers
must work with local, state, and federal government agencies, community members and
organizations, utility companies, and others that have a stake in the proposed power plant. They
work alongside lawyers, accountants, and project managers. Real estate brokers also consult with
atmospheric scientists to determine if the land is suitable for a
solar power plant.
Real estate brokers in the solar industry must have specialized
knowledge of property specifications for solar power plants and
the regulations in place for obtaining the property. Currently,
many large solar plants in the United States have been built
on—or are proposed to be built on—federal lands, so brokers
have to work with the Bureau of Land Management to obtain
leases for these properties.

Atmospheric scientists (including meteorologists) study the
atmosphere and weather patterns. In the solar power industry,

they study particular areas being considered for development of a solar power plant. Because the
efficiency of solar panels and concentrating solar power plants is highly dependent on the weather of
a particular area, atmospheric scientists are needed to study atmospheric and weather conditions
prior to the development of plants or large commercial solar projects. They can help determine if
solar power will be a cost-effective way to generate energy in a particular area by studying past
weather patterns and using computers to create models of expected weather activity. Although many
atmospheric scientists work for companies that develop large-scale solar projects, some work for
smaller consulting firms that provide these services to individual customers who are considering
installing solar power in their homes or small businesses.

Environmental scientists ensure that environmental regulations and policies are followed and that
sensitive parts of the ecosystem are protected. Many solar power plants are built in desert areas that
have fragile ecosystems and numerous protected species. Construction and operation of plants must
have minimal impact on the surrounding environment. Environmental scientists use their knowledge
of the natural sciences to minimize hazards to the health of the environment and surrounding

Real estate brokers typically have a bachelor's degree or a higher degree in business, real estate, law,
engineering, or a related discipline. Experience with obtaining land permits and an understanding of
tax and accounting rules are necessary, as well as familiarity with local environmental and energy
regulations. Experience working with relevant government agencies, such as the Bureau of Land
Management, is also desirable. Companies typically hire people with experience in land acquisition
and management and train them to their specific needs.
Atmospheric and environmental scientists typically need a bachelor's degree, but scientists with a
master's or doctoral degree are preferred, depending on the scale of the projects they work on. Many
of these scientists are hired on for the length of specific projects, and more education and experience
makes them more attractive to hire full time. Atmospheric and environmental scientists may also need
to be licensed, depending on local regulations.

BLS does not currently have wage data specific to the solar power industry. The following table shows
BLS data for selected occupations for May 2010. The wages shown are median annual wages for the
United States as a whole; wages vary by employer and location.
Selected occupations in solar power plant development

Median annual wages, 2010

Real estate brokers
Atmospheric and space scientists
Environmental scientists and specialists, including health
(1) The Occupational Employment Statistics data are available at The data do not include benefits.

Occupations in solar power plant construction
Once a site has been selected, civil engineers are responsible for the design of the power plant and
related structures. When construction begins, workers are needed to build the actual plant. For a
concentrating solar power (CSP) plant, large mirrors are arranged to catch and focus sunlight for
power generation, therefore storage tanks, pipes, and generators must be installed before the plant is
connected to the electrical grid. Photovoltaic plants are less complex, requiring installation of arrays
of photovoltaic panels before they are connected to transformers and the grid. Construction
managers have the responsibility of managing the entire construction process.

Job duties
Construction managers oversee the construction of solar power plants, from site selection to the final
construction of the plant. They supervise a team of diverse occupations, including engineers,
scientists, construction workers, and heavy-equipment operators. Construction managers are
employed by large construction companies, energy companies, or utilities companies and work under
contract or as salaried employees. Because of the size of a power plant and the complexity of the
construction, a project manager will typically oversee several construction managers, who then
supervise individual aspects of the construction.
The construction manager's time is split between working at the construction site and an office, which
may be located onsite or offsite. Primary office responsibilities include management of permits,
contracts, and the budget. At the site, the construction manager monitors progress and performs
inspections for quality control. Construction managers oversee the contracting process and manage
various contractors and subcontractors. They are responsible for ensuring a safe work environment
where workers adhere to strict site safety policies.

Civil engineers design and supervise the construction of power plants. Solar power plants can take a
number of forms and sizes. CSP plants are more like typical power plants and require incorporating
large steam turbines and storage tanks, plus a large, flat area for the solar array. Photovoltaic plants
are less complex, but are a challenge for engineers to design because the panels are optimally
configured to efficiently harvest solar power. Engineers ensure that the land is graded properly and is
flat enough to support large arrays of mirrors or photovoltaic panels. Civil engineers are also
responsible for designing necessary infrastructure, including roadways, support structures,
foundations, and plumbing systems.

Construction laborers perform a wide range of construction-related tasks. Most construction laborers
specialize in one component of construction, such as metalworking, concrete pouring and setting,
assembly, or demolition. Laborers prepare the site for construction by removing trees and debris.
They are also responsible for monitoring and repairing compressors, pumps, and generators, and for
erecting scaffolding and other support structures, as well as loading, unloading, identifying, and
distributing building materials in accordance with project plans.

Construction equipment operators use machinery to move construction materials, earth, and other
heavy materials at a construction site. Many plants require flat, unobstructed ground in order to line
up the solar panels or mirrors, and equipment operators operate machinery to clear and grade the
land. They also operate cranes to lift and place heavy objects, such as photovoltaic arrays, large
mirrors, and turbine generators. They set up and inspect their equipment, make adjustments to the
equipment, and perform some maintenance and minor repairs.

Welders who work in solar power plant construction are important for both CSP and photovoltaic
plants. In CSP plants, the work of welders includes joining structural beams together when
constructing buildings, installing the structures that support the mirrors, and joining pipes together.
At photovoltaic plants, welders are instrumental in building the solar panel mounting systems. Panels
must be mounted on the ground or on a roof using metal beams, and welders are responsible for
attaching these beams together to form the mounts.

Structural iron and steel workers use blueprints to place and install iron or steel girders, columns, and
other structures to form the support structures for power plants. These workers also cut the
structures to proper size, drill bolts for holes, and number them for onsite assembly by construction
workers or solar photovoltaic installers. The structures are then shipped to worksites where they will
be erected by structural iron and steel workers on a construction site.

In most construction occupations, workers are trained on the job. Laborers typically work under
supervisors, who direct them to complete tasks. As laborers gain more experience and prove their
abilities, they may move up to become supervisors. Equipment operators often learn on the job or
complete a formal training program, or a combination be certified, which involves some training and
testing to ensure competence and safety.
Construction managers are typically educated in construction management, business management, or
engineering, and usually have experience working in construction. Experience is important for
construction managers, so it may be substituted for some educational requirements. Large, complex
projects such as power plants, however, require specialized education. Workers with a degree in
construction management or engineering, but without significant experience, may be hired as
assistants to construction managers.
Civil engineers have at least a bachelor's degree in civil or structural engineering. Lead engineers on
large projects, such as power plants, have specialized experience and typically have at least a
master's degree. Licensure as a professional engineer (PE) may be required.
Welders usually learn their trade through on-the-job training or a formal apprenticeship program, or
they may attend a formal training program at a trade school or community college. There are many
different techniques that welders may use that also require additional training. Structural steel and
iron workers are typically trained on the job and may complete additional specialized training.

BLS does not have wage data specific to the solar power industry. However, BLS does track the wage
of occupations in the Utility System Construction industry group, which includes construction of solar
power plants. The following table shows BLS data for selected occupations in this industry group for
May 2010. The wages shown are median annual wages for the United States as a whole; however,
wages do vary by employer and location.
Selected occupations in the utility system construction industry group
Construction managers

Median annual wages, 20

Selected occupations in the utility system construction industry group

Median annual wages, 20

Civil engineers
Construction laborers
Operating engineers and other construction equipment operators
Welders, cutters, solderers, and brazers
Structural iron and steel workers
(1) The Occupational Employment Statistics data are available at The data do not include benefits.

Occupations in solar power plant operations
Workers at solar power plants install, operate, and maintain equipment. They also monitor the
production process and correct any problems that arise during normal operation. Concentrating solar
power (CSP) plants require more workers than photovoltaic plants; photovoltaic plants can sometimes
even be run remotely.

Job duties
Power plant operators monitor power generation and distribution from control rooms at power plants.
They monitor the solar arrays and generators and regulate output from the generators, and they
monitor instruments to maintain voltage to regulate electricity flows from the plant. Power plant
operators communicate with distribution centers to ensure that the proper amount of electricity is
being generated based on demand. They also go on rounds through the plant to check that
everything is operating correctly, keeping records of switching operations and loads on generators,
lines, and transformers. Operators use computers to report unusual incidents or malfunctioning
equipment, and to record maintenance
performed during their shifts.
Some CSP plants have a secondary source
of power generation, such as natural-gas
powered turbines, that will generate
power at night or when the weather
doesn't allow for sufficient solar power
generation. Power plant operators are
responsible for monitoring this equipment
and deciding when to switch from solar
generation to the secondary source.

Pump operators tend, control, and operate
pump and manifold systems that transfer oil, water, and other materials throughout the CSP plant.
CSP plants use mirrors to heat fluids like molten salt or synthetic oil, which are pumped through the
solar heating devices and into a heat-transfer device to produce steam.
Pump operators maintain the equipment and regulate the flow of materials according to a schedule
set up by the plant engineers or production supervisors. The work tends to be repetitive and

physically demanding. Workers may lift and carry heavy objects and stoop, kneel, crouch, or crawl in
awkward positions. Some work at great heights, and most work is done outdoors.

Electricians are responsible for installing and maintaining the electrical equipment and wiring that
connects the plant to the electrical grid. Electricians in power plants work with heavy equipment,
including generators, inverters, and transformers. They must be familiar with computer systems that
regulate the flow of electricity, and they must be comfortable with high-voltage systems.

Plumbers, pipefitters, and steamfitters install, maintain, and repair pipe systems. Pipe systems in
power plants carry the heat-transfer material—synthetic oil or molten salt—throughout the plant and
into special heat containment units. Other pipes carry steam from the heaters to the turbines that
generate electricity. These pipes often carry materials at both high temperatures and high pressure.
The workers monitor, regulate, and control flow through the popes using automatic controls.
Plumbers, pipefitters, and steamfitters need physical strength and stamina. They must frequently lift
heavy pipes, stand for long periods of time, and work in uncomfortable and cramped positions. They
often must work outdoors and in inclement weather conditions. In addition, they are subject to
possible injuries brought on by falls from ladders, cuts from sharp objects, and burns from hot pipes
or soldering equipment.

Electrical and electronics installers and repairers use electronic power equipment to operate and
control generating plants, substations, and monitoring equipment. They install, maintain, and repair
these complex systems.

Electrical engineers are responsible for controlling electrical generation and monitoring transmission
devices used by electric utilities in power plants.

Power plant workers generally need a combination of education, on-the-job training, and experience.
Strong mechanical, technical, and computer skills are needed to operate a power plant. Certification
by the North American Energy Reliability Corporation (NERC) is necessary for positions that could
affect the power grid. Companies also require a strong math and science background for workers
seeking highly technical jobs. Knowledge of these subjects can be obtained through specialized
training courses.
Because of security concerns, many power plant operators are subject to background investigations
and must have a clean criminal record. They must also be willing to submit to random drug testing.
Electricians and pipefitters and steamfitters must be trained on the specific systems on which they
work. They attend specialized training programs and undergo extensive on-the-job training.

BLS does not have wage data specific to the solar power industry. However, BLS does have wage
data for occupations in the Electric Power Generation, Transmission and Distribution industry group,
which includes the distribution of electricity generated by solar power plants. The table that follows
shows BLS data for selected occupations in this industry group for May 2010. The wages shown are
median annual wages for the United States as a whole; wages vary by employer and location.

Selected occupations in the electric power generation,
transmission, and distribution industry group

Median annual wages, 20

Power plant operators
Pump operators, except wellhead pumpers
Plumbers, pipefitters, and steamfitters
Electrical and electronics repairers, powerhouse, substation, and relay
(1) The Occupational Employment Statistics data are available at The data do not include benefits.

Solar photovoltaic installers
Solar photovoltaic installers are key to the process of solar panel installation and maintenance. They
use specialized skills to install residential and commercial solar projects. They are responsible for
safely attaching the panels to the roofs of houses or other buildings and ensuring that the systems
work. Solar photovoltaic installers must be able to work with power tools and hand tools at great
heights, and possess in-depth knowledge of electrical wiring as well as basic math skills. When
necessary, installers must be problem solvers, able to repair damaged systems or replace
malfunctioning components. Safety is a priority when installing solar panels because installers run the
risk of falling from a roof or being electrocuted by high voltage.
Solar photovoltaic installers are often self-employed as general contractors or employed by solar
panel manufacturers or installation companies. Installation companies typically specialize in installing
certain types of panels and provide some maintenance and repair services. When a solar panel
system is purchased, manufacturers may provide the buyer with installation services or maintenance
and repair work. Self-employed installers typically have training and experience with installing solar
power systems and are hired directly by the property owners or by a construction firm.

Job duties
The main component of a solar installer's
job is the preparation of the installation
site. Before the installation process
begins, a full audit of a structure is
conducted, including a survey of the
existing electrical system and developing
safety procedures. The job is then
designed based on the characteristics of
the structure and the type of system
being installed. After the layout and
equipment are finalized, the permits are
obtained from the relevant governments (local, state, federal, or a combination). If the installers do

not do these preparations themselves, they must familiarize themselves with the site before they
begin working on it.
Once installation begins, the proper safety equipment, such as a rope and anchor system, must be
set up to prevent falls from the rooftop. Often, the building will have to be upgraded to support the
solar panels; this may involve reinforcing the roof, replacing rafters, or installing supports to handle
the added weight of the panels. The roof must be marked to show where the arrays will be placed,
and holes are drilled in the roof to attach the mounting system. After the mounting system is in place,
the solar panels can be installed. Workers use caution during installation because the panels are
fragile, expensive, and weigh at least 40 pounds each. If the panels are damaged during the
installation process, the company has to cover the cost of repair or replacement.

Solar photovoltaic installers typically have a background in construction or as electricians. There is no
formal training standard for installers, but courses are offered by a variety of institutions, such as
trade schools, apprenticeship programs, or by photovoltaic module manufacturers. Training programs
vary widely and can range from 1 day to several weeks. Many solar installers are licensed as general
contractors and many are licensed by the North American Board of Certified Energy Practitioners
(NABCEP). Certification, while not necessary, can improve the job prospects of installers, and many
larger projects require workers to be certified.
Solar installers may work alongside roofers, electricians, and plumbers in order to learn the variety of
skills needed to complete an installation. Many installers enter the field with previous experience in
one or more of these fields. Because of the high skill level required, clients may also ask that both
lead installers and those installers who work independently obtain a general contractor’s license,
depending on regulations of the localities and states where they work.

BLS does not currently publish wage data available for solar photovoltaic installers, but these data are
being collected. According to industry sources, solar installers usually have starting salaries between
$30,000 and $40,000 per year. Installers trained as electricians or those that are licensed as general
contractors can make significantly more. As with any occupation, wages and benefits vary by
employer and geographic location.

Other occupations in solar panel installation and maintenance
Other occupations in solar installation and maintenance are site assessors, electricians, plumbers, and
roofers. These workers are involved in the installation process but are not classified as solar
photovoltaic installers. However, solar photovoltaic installers posses many of the same skills as these
occupations and often have work experience in these fields.

Job duties
Site assessors determine how much energy can be harvested at a particular location and then make
recommendations based on that assessment. Site assessors help determine the best type, size, and
layout of solar panels, and help draw up plans for installation crews. Assessors may take readings of
sunlight at a proposed location, review weather patterns, and calculate potential costs and savings.

Site assessors are usually hired for commercial projects by companies that are making substantial
investments in solar power and therefore want to ensure maximum benefits from the project. Some
site assessors may consult with homeowners or solar
installation companies on residential projects.

Electricians install and maintain all of the electrical and
power systems in a home or business. They install and
maintain the wiring and control the equipment through
which electricity flows. Electricians are responsible for
connecting the solar panels, inverter, and other equipment
to a building's power supply. Electricians may or may not
specialize in solar installation; however, most electricians
that work with solar panels have some experience or training
on solar power equipment. If a new building or house is
being constructed with a solar power generating system,
electricians may be responsible for installing the solar power
system along with the electrical wiring system, or they may
be responsible for simply connecting the solar equipment.

Plumbers install solar water heating systems. These systems
replace or augment a conventional water heater and must be
connected to a house's or building's plumbing. To install
these systems, plumbers require specialized training to work
with solar water heater equipment.

Roofers install and repair roofs, and they ensure that any cuts or holes made in the roof during the
installation of solar panels and mounting racks are properly repaired and sealed. They may also assist
with the installation of mounting systems and structural supports. Roofers typically work with a
variety of materials including tar, asphalt, gravel, rubber, thermoplastic, metal, and shingles. Roofing
work is very strenuous. It requires workers to be on hot roofs for long periods of time, and it carries
the risk of falls and other injuries.

Site assessors generally have past experience with electrical or roofing work or experience as solar
photovoltaic installers. They receive on-the-job training as well as specialized training in the
equipment and techniques used to assess a site for a potential solar project. Some formal educational
programs are available that teach basic site assessment including how to gauge the feasibility of solar
generation, estimate costs, and determine
which products to use.
Plumbers and electricians receive training
through supervised apprenticeships
administered by technical schools or
community colleges. Apprenticeships usually
consist of 4 or 5 years of paid on-the-job
training and at least 144 hours of related
classroom instruction per year. Most states
require plumbers and electricians to be

licensed. Licensing requirements vary, but it is common for states to require between 2 and 5 years
of experience, followed by an examination that tests knowledge of trade and local codes. Applicants
for apprenticeships must be at least 18 years old and in good physical condition. Drug tests may be
required, and most apprenticeship programs ask that applicants have at least a high school diploma
or equivalent.
Plumbers and electricians working on solar installation projects must also have specialized training on
the systems that they will be installing, or they must work under the supervision of a qualified solar
photovoltaic installer. Certification by the North American Board of Certified Energy Practitioners
(NABCEP) is required for many jobs, particularly large commercial installations and residential
Roofers typically have on-the-job training and may participate in 3-year apprenticeship program.
Many roofers in the solar industry educate themselves through additional training, or they gain
experience to become solar photovoltaic installers.

The following table shows BLS data for selected occupations in the Construction of Buildings industry
group for May 2010. This industry group includes new residential and nonresidential construction and
remodeling. BLS does not publish data for site assessors. The wages shown are median annual wages
for the United States as a whole; wages vary by employer and location.
Selected occupations in the construction of buildings industry group

Median annual wages, 20

Plumbers, pipefitters, and steamfitters
(1) The Occupational Employment Statistics data are available at The data do not include benefits.

Occupations supporting the
solar power industry
The advancement of the solar power
industry has led to job creation in a
number of other occupations as well.
Many of these jobs do not concentrate on
solar power, but they provide support to
solar energy production and contribute to
the industry as a whole. For instance, the
solar power supply chain consists of many
different manufacturers of varying sizes.
Foundry workers are an important part of

this supply chain; they cast metal, plastics, and composites out of raw materials into individual
components for solar energy production.
Solar manufacturers need trained salespeople to sell their products to customers. Sales
representatives, sales engineers, and sales managers are instrumental in matching a company's
products to consumers' needs. They are responsible for making their products known and generating
interest in the products. Sales professionals may work directly for manufacturers, distributers,
installers, or consulting services. A salesperson must stay abreast of new products and the changing
needs of customers. They attend trade shows at which new products and technologies are

Clean energy such as solar power is expected to be a key piece of the growing "green economy," and
jobs in solar power show great potential for new employment opportunities. Jobs are expected to
grow in all the major sectors of the solar power industry: manufacturing, project development,
construction, operation and maintenance, and installation. This growth in the solar power industry is
evidenced by the rapid increase in solar capacity over the past several years, leading to the increased
the demand for skilled workers. Jobs in this industry are located in many states and cover a wide
variety of occupations. As solar technology evolves and new uses for solar power are discovered,
occupations in the industry will continue to grow and develop.
The author would like to thank Andrea Luecke and Samantha Jacoby of the Solar Foundation and
Justin Baca of the Solar Energy Industries Association for their support of this project and for
reviewing a draft of this report.


"Frequently Asked Questions about Solar Energy Technologies," SunShot Initiative (U.S.

Department of Energy, Office of Energy Efficiency and Renewable Energy,

"U.S. Solar Industry, Year in Review 2009" (Solar Energy Industries Association, 2010), p.


"Electric Power Industry 2009: Year in Review," Electric Power Annual (U.S. Energy Information

Administration, 2010),

The Bureau of Labor Statistics does not currently have employment data for the solar power

industry. BLS has begun collecting green jobs data and it is expected to be available in 2012. For
more information on the BLS green jobs initiatives please

"National Solar Jobs Census 2010: A Review of the U.S. Solar Workforce" (The Solar Foundation,

October 2010),

Ibid, p. 17.


"Large Solar Energy Projects" (California Energy Commission,



"U.S. Solar Industry, Year in Review 2009," (Solar Energies Industries Association), p. 5.


"Photovoltaic Solar Resource: United States and Germany" (U.S. Department of Energy, National

Renewable Energy Laboratory, 2008),

Concentrated solar power
From Wikipedia, the free encyclopedia

The PS10 Solar Power Plant concentrates sunlight from a field of heliostats onto a central solar power tower.

Part of the 354 MW SEGS solar complex in northern San Bernardino County, California.

Concentrated solar power (also called concentrating solar power, concentrated solar
thermal, and CSP) systems use mirrors or lenses to concentrate a large area of sunlight,
or solar thermal energy, onto a small area. Electrical power is produced when the concentrated
light is converted to heat, which drives a heat engine (usually a steam turbine) connected to an
electrical power generator or powers a thermochemical reaction (experimental as of 2013).[1][2][3]
CSP is being widely commercialized and the CSP market has seen about 740 MW of generating
capacity added between 2007 and the end of 2010. More than half of this (about 478 MW) was
installed during 2010, bringing the global total to 1095 MW. Spain added 400 MW in 2010, taking
the global lead with a total of 632 MW, while the US ended the year with 509 MW after adding 78
MW, including two fossil–CSP hybrid plants.[4] The Middle East is also ramping up their plans to
install CSP based projects and as a part of that Plan, Shams-I the largest CSP Project in the
world has been installed in Abu Dhabi, byMasdar.[5]
CSP growth is expected to continue at a fast pace. As of January 2014, Spain had a total
capacity of 2,204 MW making this country the world leader in CSP. Interest is also notable in
North Africa and the Middle East, as well as India and China. The global market has been
dominated by parabolic-trough plants, which account for 90% of CSP plants.[4]
CSP is not to be confused with concentrated photovoltaics (CPV). In CPV, the concentrated
sunlight is converted directly to electricity via the photovoltaic effect.


1 History
2 Current technology
o 2.1 Parabolic trough
 2.1.1 Enclosed trough
o 2.2 Fresnel reflectors
o 2.3 Dish Stirling
o 2.4 Solar power tower
3 Deployment around the world
4 Efficiency
5 Costs
6 Incentives
o 6.1 Spain
o 6.2 Australia
7 Future
8 Very large scale solar power plants
9 See also
10 References
11 External links

A legend has it that Archimedes used a "burning glass" to concentrate sunlight on the invading
Roman fleet and repel them from Syracuse. In 1973 a Greek scientist, Dr. Ioannis Sakkas,
curious about whether Archimedes could really have destroyed the Roman fleet in 212 BC, lined
up nearly 60 Greek sailors, each holding an oblong mirror tipped to catch the sun's rays and
direct them at a tar-covered plywood silhouette 160 feet away. The ship caught fire after a few
minutes; however, historians continue to doubt the Archimedes story.[6]
In 1866, Auguste Mouchout used a parabolic trough to produce steam for the first solar steam
engine. The first patent for a solar collector was obtained by the Italian Alessandro Battaglia in
Genoa, Italy, in 1886. Over the following years, inventors such as John Ericsson and Frank
Shuman developed concentrating solar-powered devices for irrigation, refrigeration, and
locomotion. In 1913 Shuman finished a 55 HP parabolic solar thermal energy station in Maadi,
Egypt for irrigation.[7][8][9][10] The first solar-power system using a mirror dish was built by Dr. R.H.
Goddard, who was already well known for his research on liquid-fueled rockets and wrote an
article in 1929 in which he asserted that all the previous obstacles had been addressed.[11]
Professor Giovanni Francia (1911–1980) designed and built the first concentrated-solar plant,
which entered into operation in Sant'Ilario, near Genoa, Italy in 1968. This plant had the
architecture of today's concentrated-solar plants with a solar receiver in the center of a field of
solar collectors. The plant was able to produce 1 MW with superheated steam at 100 bar and
500 °C.[12] The 10 MW Solar One power tower was developed in Southern California in 1981, but
the parabolic-trough technology of the nearby Solar Energy Generating Systems (SEGS), begun
in 1984, was more workable. The 354 MW SEGS is still the largest solar power plant in the
world, and will remain so until the 390 MW Ivanpah power tower project comes online.

Current technology[edit]
CSP is used to produce electricity (sometimes called solar thermoelectricity, usually generated
through steam). Concentrated-solar technology systems
use mirrors or lenses withtracking systems to focus a large area of sunlight onto a small area.
The concentrated light is then used as heat or as a heat source for a conventional power

plant (solar thermoelectricity). The solar concentrators used in CSP systems can often also be
used to provide industrial process heating or cooling, such as in solar air-conditioning.
Concentrating technologies exist in four common forms, namely parabolic trough, enclosed
trough, dish Stirlings, concentrating linear Fresnel reflector, and solar power tower.[13]Although
simple, these solar concentrators are quite far from the theoretical maximum
concentration.[14][15] For example, the parabolic-trough concentration gives about 1/3 of the
theoretical maximum for the design acceptance angle, that is, for the same overall tolerances for
the system. Approaching the theoretical maximum may be achieved by using more elaborate
concentrators based on nonimaging optics.
Different types of concentrators produce different peak temperatures and correspondingly
varying thermodynamic efficiencies, due to differences in the way that they track the sun and
focus light. New innovations in CSP technology are leading systems to become more and more

Parabolic trough[edit]
Main article: Parabolic trough
A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver
positioned along the reflector's focal line. The receiver is a tube positioned directly above the
middle of the parabolic mirror and filled with a working fluid. The reflector follows the sun during
the daylight hours by tracking along a single axis. A working fluid (e.g.molten salt[17]) is heated to
150–350 °C (423–623 K (302–662 °F)) as it flows through the receiver and is then used as a
heat source for a power generation system.[18] Trough systems are the most developed CSP
technology. The Solar Energy Generating Systems (SEGS) plants in California, the world's first
commercial parabolic trough plants, Acciona's Nevada Solar One near Boulder City, Nevada,
and Andasol, Europe's first commercial parabolic trough plant are representative, alongside
with Plataforma Solar de Almería's SSPS-DCS test facilities in Spain.[19]

Enclosed trough[edit]
Enclosed trough systems are used to produce process heat. The design encapsulates the solar
thermal system within a greenhouse-like glasshouse. The glasshouse creates a protected
environment to withstand the elements that can negatively impact reliability and efficiency of the
solar thermal system.[20] Lightweight curved solar-reflecting mirrors are suspended from the
ceiling of the glasshouse by wires. A single-axis tracking system positions the mirrors to retrieve
the optimal amount of sunlight. The mirrors concentrate the sunlight and focus it on a network of
stationary steel pipes, also suspended from the glasshouse structure.[21] Water is carried
throughout the length of the pipe, which is boiled to generate steam when intense sun radiation is
applied. Sheltering the mirrors from the wind allows them to achieve higher temperature rates
and prevents dust from building up on the mirrors.[20]

Fresnel reflectors[edit]
Main article: Compact Linear Fresnel Reflector
Fresnel reflectors are made of many thin, flat mirror strips to concentrate sunlight onto tubes
through which working fluid is pumped. Flat mirrors allow more reflective surface in the same
amount of space as a parabolic reflector, thus capturing more of the available sunlight, and they
are much cheaper than parabolic reflectors. Fresnel reflectors can be used in various size

Dish Stirling[edit]

A dish Stirling

Main article: Dish Stirling
A dish Stirling or dish engine system consists of a stand-alone parabolic reflector that
concentrates light onto a receiver positioned at the reflector's focal point. The reflector tracks the
Sun along two axes. The working fluid in the receiver is heated to 250–700 °C (523–973 K (482–
1,292 °F)) and then used by a Stirling engine to generate power.[18] Parabolic-dish systems
provide high solar-to-electric efficiency (between 31% and 32%), and their modular nature
provides scalability. The Stirling Energy Systems (SES), United Sun Systems (USS) and Science
Applications International Corporation (SAIC) dishes at UNLV, and Australian National
University's Big Dish in Canberra, Australia are representative of this technology. As of 2008,
The world record for solar to electric efficiency was set at 31.25% by SES dishes at the National
Solar Thermal Test Facility (NSTTF)[24] . The SES installation in Maricopa, Phoenix was the
largest Stirling Dish power installation in the world until it was sold to United Sun Systems.
Subsequently, larger parts of the installation have been moved to China as part of the huge
energy demand.

Solar power tower[edit]
Main article: Solar power tower
A solar power tower consists of an array of dual-axis tracking reflectors (heliostats) that
concentrate sunlight on a central receiver atop a tower; the receiver contains a fluid deposit,
which can consist of sea water. The working fluid in the receiver is heated to 500–1000 °C (773–
1,273 K (932–1,832 °F)) and then used as a heat source for a power generation or energy
storage system.[18] Power-tower development is less advanced than trough systems, but they
offer higher efficiency and better energy storage capability. The Solar Two in Daggett, California
and the CESA-1 in Plataforma Solar de Almeria Almeria, Spain, are the most representative
demonstration plants. The Planta Solar 10(PS10) in Sanlucar la Mayor, Spain, is the first
commercial utility-scale solar power tower in the world. eSolar's 5 MW Sierra SunTower, located
in Lancaster, California, is the only CSP tower facility operating in North America. The National
Solar Thermal Test Facility, NSTTF located in Albuquerque, NM, is an experimental solar
thermal test facility with a heliostat field capable of producing 6 MW.

Deployment around the world[edit]
Main article: List of solar thermal power stations
The commercial deployment of CSP plants started by 1984 in the US with the SEGS plants until
1990 when the last SEGS plant was completed. From 1991 to 2005 no CSP plants were built
anywhere in the world.

Concentrated Solar Power (MWp)


1984 1985 1989 1990 ... 2006 2007 2008 2009









200 80

Cumulative 14


274 354 354 355 429 484 662.5 969

2011 2012

178.50 306.50 628.5 802.5

1597.5 2553



total spectrum solar concentrator

To optimize the efficiency of solar power, a total spectrum solar concentrator is used. The suns
rays are first concentrated usingparabolic mirrors or a fresnel lens, and then spread out into
a light spectrum via a prism. Each different part of the spectrum is aimed at a solar
cell manufactured to operate most efficiently in that wavelength range. This technology has
multiple problems, most notably in that it results in only marginal gains in efficiency[citation needed].
For thermodynamic solar systems, the maximum solar-to-work (ex: electricity) efficiency can
be deduced by considering boththermal radiation properties and Carnot's principle.[27] Indeed,
solar irradiation must first be converted into heat via a solar receiver with an efficiency
; then this heat is converted into work with Carnot efficiency
. Hence, for a solar receiver
providing a heat source at temperature TH and a heat sink at temperature T° (e.g.: atmosphere at
T° = 300 K) :



are respectively the incoming solar flux and the fluxes
absorbed and lost by the system solar receiver.
For a solar flux I (e.g. I = 1000 W/m2) concentrated C times with an
on the system solar receiver with a collecting area A and
an absorptivity :
For simplicity's sake, one can assume that the losses are only radiative
ones (a fair assumption for high temperatures), thus for a reradiating
area A and an emissivity applying the Stefan-Boltzmann law yields:

Simplifying these equations by considering perfect optics (
1), collecting and reradiating areas equal and maximum absorptivity
and emissivity ( = 1, = 1) then substituting in the first equation

One sees that efficiency does not simply increase monotonically
with the receiver temperature. Indeed, the higher the
temperature, the higher the Carnot efficiency, but also the lower
the receiver efficiency. Hence, the maximum reachable
temperature (i.e.: when the receiver efficiency is null, blue curve

on the figure below) is:
There is a temperature Topt for which the efficiency is maximum,
i.e. when the efficiency derivative relative to the receiver
temperature is null:

Consequently, this leads us to the following equation:

Solving this equation numerically allows us to obtain
the optimum process temperature according to the
solar concentration ratio C (red curve on the figure


500 1000 5000 10000

45000 (max. for

Tmax 1720 2050 3060 3640


Topt 970 1100 1500 1720


As of 9 September 2009, the cost of building a CSP
station was typically about US$2.50 to $4 per
watt,[28] while the fuel (the sun's radiation) is free. Thus
a 250 MW CSP station would have cost $600–1000
million to build. That works out to $0.12 to 0.18
USD/kWh.[28] New CSP stations may be economically
competitive with fossil fuels. Nathaniel Bullard, a solar
analyst at Bloomberg New Energy Finance, has
calculated that the cost of electricity at the Ivanpah
Solar Power Facility, a project under construction in
Southern California, will be lower than that from
photovoltaic power and about the same as that from
natural gas.[29] However, in November 2011, Google
announced that they would not invest further in CSP
projects due to the rapid price decline of photovoltaics.
Google invested US$168 million on
BrightSource.[30][31] IRENA has published on June 2012
a series of studies titled: "Renewable Energy Cost
Analysis". The CSP study shows the cost of both
building and operation of CSP plants. Costs are
expected to decrease, but there are insufficient
installations to clearly establish the learning curve. As

of March 2012, there were 1.9 GW of CSP installed,
with 1.8 GW of that being parabolic trough.[32]

Solar-thermal electricity generation is eligible for feed-in
tariff payments (art. 2 RD 661/2007), if the system
capacity does not exceed the following limits: Systems
registered in the register of systems prior to 29
September 2008: 500 MW for solar-thermal systems.
Systems registered after 29 September 2008 (PV only).
The capacity limits for the different system types are redefined during the review of the application conditions
every quarter (art. 5 RD 1578/2008, Annex III RD
1578/2008). Prior to the end of an application period,
the market caps specified for each system type are
published on the website of the Ministry of Industry,
Tourism and Trade (art. 5 RD 1578/2008).[33]
Since 27 January 2012, Spain has halted acceptance
of new projects for the feed-in-tariff.[34][35] Projects
currently accepted are not affected, except that a 6%
tax on feed-in-tariffs has been adopted, effectively
reducing the feed-in-tariff.[36]

At the federal level, under the Large-scale Renewable
Energy Target (LRET), in operation under the
Renewable Energy Electricity Act 2000 (Cth), large
scale solar thermal electricity generation from
accredited RET power stations may be entitled to
create large-scale generation certificates (LGCs).
These certificates can then be sold and transferred to
liable entities (usually electricity retailers) to meet their
obligations under this tradeable certificates scheme.
However as this legislation is technology neutral in its
operation, it tends to favour more established RE
technologies with a lower levelised cost of generation,
such as large scale onshore wind, rather than solar
thermal and CSP.[37] At State level, renewable energy
feed-in laws typically are capped by maximum
generation capacity in kWp, and are open only to micro
or medium scale generation and in a number of
instances are only open to solar PV (photovoltaic)
generation. This means that larger scale CSP projects
would not be eligible for payment for feed-in incentives
in many of the State and Territory jurisdictions.

A study done by Greenpeace International, the
European Solar Thermal Electricity Association, and
the International Energy Agency's SolarPACES group
investigated the potential and future of concentrated
solar power. The study found that concentrated solar
power could account for up to 25% of the world's

energy needs by 2050. The increase in investment
would be from 2 billion euros worldwide to 92.5 billion
euros in that time period.[38] Spain is the leader in
concentrated solar power technology, with more than
50 government-approved projects in the works. Also, it
exports its technology, further increasing the
technology's stake in energy worldwide. Because the
technology works best with areas of
high insolation (solar radiation), experts predict the
biggest growth in places like Africa, Mexico, and the
southwest United States. It indicates that the thermal
storage systems based in nitrates (calcium, potassium,
sodium,...) will make the CSP plants more and more
profitable. The study examined three different
outcomes for this technology: no increases in CSP
technology, investment continuing as it has been in
Spain and the US, and finally the true potential of CSP
without any barriers on its growth. The findings of the
third part are shown in the table below:




2015 21 billion euros a year 420 megawatts

2050 174 billion euros a year 1500 gigawatts
Finally, the study acknowledged how technology for
CSP was improving and how this would result in a
drastic price decrease by 2050. It predicted a drop from
the current range of €0.23–0.15/kwh to €0.14–
0.10/kwh.[38] Recently the EU has begun to look into
developing a €400 billion ($774 billion) network of solar
power plants based in the Sahara region using CSP
technology known as Desertec, to create "a new
carbon-free network linking Europe, the Middle East
and North Africa". The plan is backed mainly by
German industrialists and predicts production of 15% of
Europe's power by 2050. Morocco is a major partner in
Desertec and as it has barely 1% of the electricity
consumption of the EU, it will produce more than
enough energy for the entire country with a large
energy surplus to deliver to Europe.[39]
Algeria has the biggest area of desert, and private
Algerian firm Cevital has signed up
for Desertec.[39] With its wide desert (the highest CSP
potential in the Mediterranean and Middle East regions
~ about 170 TWh/year) and its strategic geographical
location near Europe Algeria is one of the key countries
to ensure the success of Desertec project. Moreover,
with the abundant natural-gas reserve in the Algerian
desert, this will strengthen the technical potential of

Algeria in acquiring Solar-Gas Hybrid Power Plants for
24-hour electricity generation.
Other organizations expect CSP to cost $0.06(US)/kWh
by 2015 due to efficiency improvements and mass
production of equipment.[40] That would make CSP as
cheap as conventional power. Investors such
as venture capitalist Vinod Khosla expect CSP to
continuously reduce costs and actually be cheaper than
coal power after 2015.
On 9 September 2009; 4 years ago, Bill
Weihl,'s green-energy spokesperson said
that the firm was conducting research on the heliostat
mirrors and gas turbine technology, which he expects
will drop the cost of solar thermal electric power to less
than $0.05/kWh in 2 or 3 years.[28]
In 2009, scientists at the National Renewable Energy
Laboratory (NREL) and SkyFuel teamed to develop
large curved sheets of metal that have the potential to
be 30% less expensive than today's best collectors of
concentrated solar power by replacing glass-based
models with a silver polymer sheet that has the same
performance as the heavy glass mirrors, but at much
lower cost and weight. It also is much easier to deploy
and install. The glossy film uses several layers of
polymers, with an inner layer of pure silver.
Telescope designer Roger Angel (Univ. of Arizona) has
turned his attention to CPV, and is a partner in a
company called Rehnu. Angel utilizes a spherical
concentrating lens with large-telescope technologies,
but much cheaper materials and mechanisms, to create
efficient systems.[41]

Very large scale solar power
There are several proposals for gigawatt size, very
large scale solar power plants. They include the EuroMediterranean Desertec proposal, Project Helios in
Greece (10 gigawatt), and Ordos (2 gigawatt) in China.
A 2003 study concluded that the world could generate
2,357,840 TWh each year from very large scale solar
power plants using 1% of each of the world's deserts.
Total consumption worldwide was 15,223
TWh/year[42] (in 2003). The gigawatt size projects are
arrays of single plants. The largest single plant in
operation is 80 MW (SEGS VIII and SEGS IX) and the
largest single plant in construction is 370 MW (Ivanpah
Solar). In 2012, the BLM made available 97,921,069
acres of land in the southwestern United States for
solar projects, enough for between 10,000 and 20,000
gigawatts (GW).[43]

See also[edit]
Renewable energy portal

Energy portal
Sustainable development portal

List of solar thermal power stations
Concentrated photovoltaics (CPV)
Copper in concentrating solar thermal power
Clean Technology Fund
Luminescent solar concentrator
Photovoltaic thermal hybrid solar collector#PV/T
concentrator (CPVT) (CPVT)
Salt evaporation pond
Sandia National Laboratory
Solar air conditioning
Solar lighting
Solar thermal collector
Solar hot water
Thermochemical cycle
Total Spectrum Solar Concentrator

1. Jump up^ "Sunshine to Petrol". Sandia National
Laboratories. Retrieved 11 April 2013.
2. Jump up^ "Integrated Solar Thermochemical
Reaction System". U.S. Department of Energy.
Retrieved 11 April 2013.
3. Jump up^ Matthew L. Wald (10 April
2013). "New Solar Process Gets More Out of
Natural Gas". The New York Times. Retrieved 11
April 2013.
a b
4. ^ Jump up to: Janet L. Sawin and Eric Martinot
(29 September 2011). "Renewables Bounced
Back in 2010, Finds REN21 Global
Report". Renewable Energy World.
5. Jump up^ Largest CSP Project in the World
Inaugurated in Abu Dhabi – Renew India
Campaign – solar photovoltaic, Indian Solar
News, Indian Wind News, Indian Wind Market. (18 March 2013). Retrieved
on 22 April 2013.
6. Jump up^ Thomas W. Africa (1975).
"Archimedes through the Looking Glass". The
Classical World 68 (5): 305–
308. doi:10.2307/4348211. JSTOR 4348211.

7. Jump up^ Ken Butti, John Perlin (1980) A
Golden Thread: 2500 Years of Solar Architecture
and Technology, Cheshire Books, pp. 66–
100, ISBN 0442240058.
8. Jump up^ CM Meyer. From troughs to triumph:
SEGS and gas. Retrieved on
22 April 2013.
9. Jump up^ Cutler J. Cleveland (23 August
2008). Shuman, Frank. Encyclopedia of Earth.
10. Jump up^ Paul Collins (Spring 2002) The
Beautiful Possibility. Cabinet Magazine, Issue 6.
11. Jump up^ "A New Invention To Harness The
Sun" Popular Science, November 1929
12. Jump up^ Ken Butti, John Perlin (1980) A
Golden Thread: 2500 Years of Solar Architecture
and Technology, Cheshire Books, p. 68, ISBN
13. Jump up^ Types of solar thermal CSP plants. Retrieved on 22 April
14. Jump up^ Julio Chaves (2008) Introduction to
Nonimaging Optics, CRC Press, ISBN 9781420054293
15. Jump up^ Roland Winston, Juan C. Miñano,
Pablo G. Benitez (2004) Nonimaging Optics,
Academic Press, ISBN 978-0127597515.
16. Jump up^ New innovations in solar thermal. (1 November 2008).
Retrieved on 22 April 2013.
17. Jump up^ Molten salt as CSP plant working
fluid. (PDF) . Retrieved on 22 April 2013.
a b c
18. ^ Jump up to:
Christopher L. Martin; D. Yogi
Goswami (2005). Solar energy pocket reference.
Earthscan. p. 45. ISBN 978-1-84407-306-1.
19. Jump up^ "Linear-focusing Concentrator
Facilities: DCS, DISS, EUROTROUGH and LS3".
Plataforma Solar de Almería. Archived from the
original on 28 September 2007. Retrieved 29
September 2007.
a b
20. ^ Jump up to: Deloitte Touche Tohmatsu
Ltd, "Energy & Resources Predictions 2012", 2
November 2011
21. Jump up^ Helman, Christopher, "Oil from the
sun", "Forbes", 25 April 2011
22. Jump up^ Compact CLFR.
(12 June 2002). Retrieved on 22 April 2013.
23. Jump up^ Ausra's Compact Linear Fresnel
Reflector (CLFR) and Lower Temperature
24. Jump up^ Sandia, Stirling Energy Systems set
new world record for solar-to-grid conversion
efficienc. (12 February 2008).
Retrieved on 22 April 2013.
25. Jump up^ CSP Facts & Figures.
Retrieved on 22 April 2013.
26. Jump up^ Concentrating Solar Power.,
p. 11.

27. Jump up^ E. A. Fletcher (2001). "Solarthermal
processing: A review". Journal of Solar Energy
Engineering 123 (2): 63. doi:10.1115/1.1349552.
a b c
28. ^ Jump up to:
Poornima Gupta and Laura
Isensee (11 September 2009). Carol Bishopric,
ed."Google Plans New Mirror For Cheaper Solar
Power". Global Climate and Alternative Energy
Summit. San Francisco: Reuters
29. Jump up^ Robert Glennon and Andrew M.
Reeves (2010). "Solar Energy's Cloudy
Future".Arizona Journal of Environmental Law &
Policy 91: 106.
30. Jump up^ Google cans concentrated solar
power project, Reve, 24 November 2011.
31. Jump up^ Google Renewable Energy Cheaper
than Coal (RE<C). Retrieved on 22
April 2013.
32. Jump up^ Renewable Energy Cost Analysis –
Concentrating Solar Power.
33. Jump up^ Feed-in tariff (Régimen Especial). (12 December 2011).
34. Jump up^ Spanish government halts PV, CSP
feed-in tariffs. (30 January
2012). Retrieved on 22 April 2013.
35. Jump up^ Spain Halts Feed-in-Tariffs for
Renewable Energy. (9 April 2012).
Retrieved on 22 April 2013.
36. Jump up^ Spain introduces 6% energy tax. (14 September 2012). Retrieved on 22
April 2013.
37. Jump up^ A Dangerous Obsession with Least
Cost? Climate Change, Renewable Energy Law
and Emissions Trading Prest, J. (2009) in Climate
Change Law: Comparative, Contractual and
Regulatory Considerations, W. Gumley & T.
Daya-Winterbottom (eds.) Lawbook
Company, ISBN 0455226342
a b
38. ^ Jump up to: Concentrated solar power could
generate 'quarter of world's energy' Guardian
a b
39. ^ Jump up to: Tom Pfeiffer (23 August
2009) Europe's Saharan power plan: miracle or
40. Jump up^ CSP and photovoltaic solar
power, Reuters (23 August 2009).
41. Jump up^ "Video: Concentrating photovoltaics
inspired by telescope design". SPIE Newsroom.
2011. doi:10.1117/2.3201107.02.
42. Jump up^ A Study of Very Large Solar Desert
Systems with the Requirements and Benefits to
those Nations Having High Solar Irradiation
43. Jump up^ Solar Resource Data and Maps. Retrieved on 22 April 2013.

24/7 Concentrating Solar Power Plant
Gains Approval in Chile
Andrew Burger | Friday May 16th, 2014 | 1 Comment


Spanish sustainable energy
multinational Abengoa on May 9 announced that the Chilean Environmental Service’s
Evaluation and Review Committee unanimously approved its concentrating solar power
(CSP) andenergy storage project. The project is planned for the country’s northern
Atacama Desert region, which has the highest levels of solar radiation in the world, and will
produce 110 megawatts of energy.
Dubbed Cerro Dominador, Abengoa’s CSP project is ―groundbreaking‖ in more ways than
one. In addition to being the largest CSP facility announced in South America to date, it will
be ―the first to serve as a baseload power plant‖ — supplying electricity 24 hours a day,
seven days a week — thanks to a molten-salts energy storage system capable of storing the
equivalent of some 18 hours worth of electricity production, Abengoa explains in a press
Coming amid ongoing technological advances, the integration of grid-scale energy storage
capacity in CSP (also known as solar thermal power) plants is being touted as a potential
―game-changer‖ for the technology despite concerns and controversy regarding its
environmental impacts.

Concentrating solar power and the environment

Generating environmental concerns and controversy here in the U.S., the Ivanpah Solar

Electric Generating Station was commissioned this past February in California’s Mojave
Desert 140 miles southwest of Las Vegas.
The massive $1.6 billion, 392-MW (gross)/377-MW (net) plant, developed by BrightSource
Energy with financial backing from NRG and Google, was built on intact desert habitat.
Construction was temporarily called to a halt in the spring of 2011 due to concerns about its
impact on Mojave desert tortoises, which are classified as threatened by the International
Union for Conservation of Nature (IUCN).
Counterbalancing the environmental impacts of CSP plants, their triple bottom line benefits
are substantial. As Abengoa states in its press release:
―The Cerro Dominador project forms part of the Chilean Government’s national renewable
energy development program, intended to provide Chile with a clean energy future, while
also promoting economic development and reducing the country’s dependency on coal and
natural gas.‖
Abengoa expects designing, building and operating the Cerro Dominador CSP facility will
create 700 direct jobs and require up to 2,000 workers overall. Fifty long-term employees will
be required once commercial operation begins. ―Similarly, the development, commissioning
and operation of the plant will generate a high number of indirect jobs, as well as a network
of services and new industrial investments that will develop the local market, promoting
economic growth in the country,‖ Abengoa adds.
Emissions-free, CSP projects also go a long way when it comes to climate change
mitigation. Able to generate enough energy to power more than 140,000 California homes,
the solar electricity produced by Ivanpah is projected to avoid more than 400,000 tons of
carbon dioxide (CO2) emissions per year. Though its generation capacity is less than a third
of Ivanpah’s, Abengoa estimates the CSP at Cerro Dominador will avoid some 643,000 tons
of CO2 annually.
In addition to climate-warming carbon and greenhouse gas emissions, the amount of water
being used to generate electricity and produce transportation fuels has become an
increasingly pressing, and costly, issue in the U.S. and globally over the past decade.

CSP at the Water-Energy Nexus
Compared to fossil-fuel energy sources, particularly oil and gas extracted from shale
deposits by ―fracking,‖ wind and solar power generation make minimal use of, and have a
minimal impact on, water resources. As they produce electricity using conventional steam
generation, CSP systems do use more water than solar photovoltaic (PV) or wind power
systems. The water in CSP systems is recycled and used over and over again in a closedloop, however, which minimizes the water required in electricity generation.
CSP systems also make use of water for cooling. At Ivanpah, BrightSource is using a dry, air
cooling system. That results in Ivanpah using 90 percent less water than a conventional wetcooled CSP plant, according to BrightSource.

CSP and integrated grid-scale energy storage

Acknowledging concerns about the environmental impacts of CSP plants, Research &
Markets believes they will be assuaged, or at least overcome, and that the net benefits
utility-scale CSP plants afford as compared to conventional fossil-fuel power plants will win
Assessing the environmental impacts of Cerro Dominador, Chilean environmental experts
―took into account issues such as use of the land, water, air, emissions, and waste, as well
as any other aspect that could generate an environmental impact in the area where the plant
will be constructed,‖ Abengoa highlights.
Integrating grid-scale energy storage into utility-scale CSP plants is a milestone for the
technology and intermittent renewable energy systems more generally. Abengoa was the
first company to build and commercially launch a CSP-molten-salt power plant in the U.S.
Last October, Abengoa commissioned the world’s largest parabolic-trough-and-tower CSP
facility. With a rated generation capacity of 280 MW, the Solana CSP plant uses molten salt
to store the equivalent of six hours worth of the plant’s electricity output.
As Research & Markets sees it:
―Concentrating Solar Power (CSP) solar energy is the most promising and sustainable
renewable energy; rolling out CSP systems offers both performance and competitive energy
prices. CSP Solar provides a crucial energy solution that is utility scale and works 24×7 in
combination with back-up stationary fuel cells.‖
Whether making use of molten salts or hydrogen fuel cells, the integration of grid-scale
storage capacity in CSP plants is a game-changer, according to Research & Markets. ―A
step-change in system costs is being achieved, putting the industry on the cusp of a major
growth spurt,‖ the market research company asserts.
Image credits: 1) Abengoa, 2) BrightSource Energy; 3) Tractebel Engineering

Solar power
The sun’s energy can be turned into electrical power in two different ways. The first is
called “photovoltaic energy” and this is done by converting sunlight into an electric
current using the photoelectric effect. You can find out more about this here. The
second way is called “concentrated solar power”, and this is what we are focussing on in
our project.

Concentrated solar power
Move your mouse over the numbers in the image to find out about the different steps in
the process of harnessing solar power.

How does CSP work?
Sunlight is reflected from solar panels onto a solar receiver at the top of a solar tower.
The receiver gets extremely hot and heats up special thermal fluid that is being
continuously pumped up to it. The fluid reaches more than 500°C when it is heated by
the receiver, and the hot fluid is pumped down and out to a heat exchanger. In the heat
exchangeer the heat in the thermal fluid is transferred to water to generate steam. The
steam is then pumped to a turbine where it turns the turbine, creating electricity, which
is sent to the grid. The steam is converted back to water in a condenser, so that it can be


Concentrating Photovoltaics (CPV)

In Concentrating Photovoltaics (CPV), a large area of sunlight is focused onto the solar cell with the
help of an optical device. By concentrating sunlight onto a small area, this technology has three
competitive advantages:

Requires less photovoltaic material to capture the same sunlight as non-concentrating pv.
Makes the use of high-efficiency but expensive multi-junction cells economically viable due to
smaller space requirements.
The optical system comprises standard materials, manufactured in proven processes. Thus, it is less
dependant on the immature silicon supply chain. Moreover, optics are less expensive than cells.
Concentrating light, however, requires direct sunlight rather than diffuse light, limiting this technology
to clear, sunny locations. It also means that, in most instances, tracking is required.
Despite having been researched since the 1970s, it has only now entered the solar electricity sector
as a viable alternative. Being a young technology, there is no single dominant design.
The most common classification of CPV- modules is by the degree of concentration, which is
expressed in number of "suns". E.g. "3x" means that the intensity of the light that hits the photovoltaic
material is 3 times than it would be without concentration.

Low concentration
Degree of concentration

Medium concentration

High concentrat

2 - 10

10 - 100

> 100

No tracking necessary

1-axis tracking sufficient

Dual axis tracking required

No cooling required

Passive cooling sufficient

Active cooling reuqired in mos

Photovoltaic Material

High- quality silicon

Multi-junction cells

Here are some examples of concentrator technologies and examples for both line and point
concentrators. Although there might be differences in execution or materials used, most designs will
follow one of those concepts..

Fresnel Lens
A Fresnel lens, named after the French physicist, comprises several sections with different angles,
thus reducing weight and thickness in comparison to a standard lens. With a Fresnel lens, it is
possible to achieve short focal lenght and large aperture while keeping the lens leight.
Fresnel lenses can be constructed

in a shape of a circle to provide a point focus with concentration ratios of around 500, or
in cylindrical shape to provide line focus with lower concentration ratios.
With the high concentration ratio in a Fresnel point lens, it is possible to use a multi-junction
photovoltaic cell with maximum efficiency. In a line concentrator, it is more common to use high
efficiency silicon.

Parabolic Mirrors
Here, all incoming parallel light is reflected by the collector (the first mirror) through a focal point
onto a second mirror. This second mirror, which is much smaller, is also a parabolic mirror with the
same focal point. It reflects the light beams to the middle of the first parabolic mirror where it hits the
solar cell.
The advantage of this configuration is that it does not require any optical lenses. However, losses
will occur in both mirrors. SolFocus has achieved a concentration ratio of 500 in point concentratorshape with dual axis- tracking.

Low concentration photovoltaic modules use mirrors to concentrate sunlight onto a solar cell. Often,
these mirrors are manufactured with silicone-covered metal. This technique lowers the reflection
losses by effectively providing a second internal mirror.
The angle of the mirrors depends on the inclination angle and latitude as well as the module design,

but is typically fixed. The concentration ratios achieved range from 1.5 - 2.5.
Low concentration cells are usually made from monocrystalline silicon. No cooling is required.
The largest low-concentration photovoltaic plant in the world is Sevilla PV with modules from three
companies: Artesa, Isofoton and Solartec.

Luminescent Concentrators
In a luminescent concentrator, light is refracted in a luminescent film, and then being channelled
towards the photovoltaic material. This is a very promising technology, as it does not require optical
lenses or mirrors. Moreover, it also works with diffuse light and hence does not need tracking. The
concentration factor is around 3.
There are various developments going on. For instance, Covalent are using an organic material for
the film, whilst Prism Solar use holographic film.
Furthermore, this concentrator does not need any cooling, as the film could be constructed such that
wavelenghts that can not be converted by the solar cell would just pass thru. Hence, unwanted
wavelenghts would be removed.


Most concentrating pv systems require cooling.
Passive Cooling: Here, the cell is placed on a cladded cermaic substrate with high thermal
conductivity. The ceramic also provides electrical isolation.
Active Cooling: Typically, liquid metal is used as a cooling fluid, capable of cooling from 1,700°C to

Low-concentration modules

Low-concentration pv modules using
mirrors without further tracking.

Linear Fresnel concentrator devices
byEntech Solar.

High-concentration modules

High concentration 300x "Diamond Power"
series by EnFocus has been specifically
developed for rooftop installations,
including dual-axis tracking.

Parabolic mirrors achieve 500x
concentration in devices developed

Holographic concentrat
Solarachieving concentr
around 3.

Molten salt keeps solar
power flowing
BrightSource Energy will add molten salt storage to upcoming
concentrating solar power plants, touting the benefits of solar
thermal technology over low-cost solar photovoltaic technology.

by Martin LaMonica

November 30, 2011 7:59 AM PST

comme nts


face book








more +

BrightSource solar thermal power plants can be equipped with a two-tank molten salt
storage system, as shown on the right side of this image.BrightSource Energy

By storing solar energy in molten salt, BrightSource Energy can now build one
less solar power plant.
The company said today that it is adding energy storage to three planned
solar projects that will supply power to utility Southern California Edison.
Instead of building seven power plants to provide about 4 million megawatthours per year, BrightSource now expects to be able to meet that with six
concentrating solar plants to be built over the next six years, including three
that will have storage. It is now constructing its first project, the Ivanpah Solar
Electric Generating System, which will not have storage.
BrightSource's plants use a field of computer-controlled mirrors that
concentrate sunlight onto a tower. The heat creates steam, which is used to
generate electricity in a conventional turbine. The storage system keeps
molten salt in tanks and produces steam as needed.

By providing power to the grid after the sun goes down, BrightSource can earn
more money from its plant during peak demand times and generally lower the
cost of solar, the company said.

Related stories

BrightSource adds salt for solar power at night li>

Solar power plant switches to PV from thermal

Rooftop solar prices fall 'precipitously'
Storage also helps give solar thermal technologies an advantage compared
with solar phototoltaic panels, which have plummeted in cost over the past
three years because of lower silicon prices and high-volume manufacturing in
China. A number of large solar projects in the U.S. have abandoned
concentrating solar thermal technologies for flat-plate solar photoltaic
panels because of cost.
BrightSource said that its storage system will allow solar to replace fossil fuel
plants rather than supplement them and avoid the need for natural gas backup power. Earlier this year, California passed a law encouraging development
of grid storage, which helped bring the addition of storage to BrightSource's
plants, it said.


1 reddit3


Solar is happening right now, but maybe you didn’t hear? Somehow in all the hubbub of the GOP
(Good Ol’ Petroleum) takedown — and amid debate about how much Keystone XL focus is too
much Keystone XL focus — news about solar power infrastructure in the U.S. hasn’t reached
everyone’s front page.
So here’s a cheerful update from the American Southwest: two enormous solar thermal power
plants are coming online, step-by-step, right as you're reading this.
In California, BrightSource Energy’s Ivanpah Solar Electric Generating System is slated to be the
largest solar power plant in the world. At a cost of $2.2 billion (its investors include NRG and
Google, who are backed by a federal loan guarantee), Ivanpah took four years to develop and

uses concentrated solar power, or CSP, to generate up to 377 Megawatts an hour for the state
grid. The plant will be at full operating capacity by January.
Located on 4,000 acres of now-enclosed public land near the Mojave Desert, the facility features
three central towers surrounded by enormous rings of heliostat (sun-tracking) mirrors that direct
beams of sunlight onto the towers’ receivers. The receivers generate steam to power turbines,
producing energy. You can visit the solar site online to take a slightly nausea-inducing virtual tour
of the facility.
Second, in Gila Bend, Arizona, the Spanish corporation Abengoa Solar has recently completed
the Solana plant, a $2 billion, 280 Megawatt project. Solana is also thermal solar, but it uses
mirrored parabolic troughs to heat tubes of fluid that power a turbine. The plant also stores heat
in molten salt batteries that release power well into the night, offering a strong counter-example
to the common critique of solar as an intermittent energy source and, therefore, unreliable.
These projects will serve as a proof of concept for the viability of investment in large scale
thermal solar, which had lately been second banana to the no-fuss, cheaper photovoltaic (PV)
solar panels used on most businesses and homes.
Thermal Solar vs. Photovoltaic
Thermal solar technology requires a large, flat geographic footprint to generate power on a utility
scale. Due to this, there has been significant opposition to Ivanpah, as well as other large scale
solar projects, for thedisruption they cause to desert habitat. While it’s true that photovoltaic
technology is more modular — panels can be installed individually, more or less wherever there’s
sun — PV power plants would be equally disruptive when scaled up, and are less efficient at
generating electricity than thermal solar. Thermal solar is also less susceptible to the
interruptions of passing clouds, and can store and release power for hours after the sun is gone.
So if PV is less efficient and less consistent, why is thermal solar losing ground to it?
Here we get into the foggy area where environmental concerns meet the global market. A PV
power plant amounts to a lot of PV panels located in one place. The technology is known and the
outcome predictable, making PV a safe and reliable investment.
But in the warm glow of investor funds, Chinese manufacturers in recent years have slashed the
cost of production and flooded the international market with PV panels. The influx was so fast,
and the numbers so large, that U.S. and E.U. regulators imposed tariffs this summer on Chinese
renewables in support of their own renewable sectors, or in deference to the fossil fuel lobby —
or perhaps both.
It won’t do to slander photovoltaic as bad and praise thermal as the better choice. Both are
crucial pieces to our climate puzzle, serving distinct functions. But what particularly troubles me

about PV is its reliance on rare earth metals and the toxic environmental and political
processes used to extract them.
Typically, corporations operating mines do not embrace human rights alongside the rare
commodities they seek. And humans still have no good ideas about where to warehouse
hazardous materials after their utility is spent. So, in anticipation of a future shortage of the
necessary materials to produce PV panels, wouldn’t it be wise to cultivate a technology that
isn't restricted by materials availability?

A Little Perspective About the Size of Things
To that end, here are two nice, big projects right when we need them. If these plants continue to
produce reliable energy with minimal surprises, they may stimulate solar thermal technology to

evolve alongside photovoltaics. Jeff Holland, the media contact at Ivanpah’s NRG Corporation,
describes the project as “technologically agnostic."
"The price of PV has come down so drastically in the past two or three years, no one could have
predicted. But if the economics are right," he says, "we would absolutely do more solar thermal.
We’re a pretty diverse company, but [Ivanpah] is going to be our big stake in the ground. We
consider it our crown jewel.”
Referring to the molten salt storage technology that Solana is employing in neighboring Arizona,
Holland adds: “If we had been planning this a little later, we probably would have included some
storage.” Nonetheless, Ivanpah stands as the world's largest solar thermal power producer. To
put large in perspective, a word about watts:
A kilowatt is a thousand watts, and a Megawatt (MW) is a million watts. When a power plant is
rated in Megawatts, it is the unit of power that refers to its maximum possible output in one hour.
A typical American household in 2008 used energy at an average rate of 2 kilowatts per hour.
Arizona, with a population of 6.6 million, is 26th in U.S. energy consumption and 23rd in CO2
emissions. It generates its electricity from a mix of sources, led by natural gas, then nuclear,
coal, hydroelectric and mixed renewables, in a negligible 5th place. Challenging this, Solana will
serve the needs of 70,000 Arizona households. A nice start, though it still leaves about 1.5
million Arizona households powered by fossil fuels. A notable fact about Arizona: 25% of all
energy consumed in the state is from air conditioning (the national average is 6%).
California, meanwhile, is a bigger and more complicated beast. While its per capita energy
consumption ranks 47th in the nation, it is the second largest CO2 emitter behind Texas. While it
has nearly weaned itself off coal entirely, California is burning a stunning amount of natural gas,
and it does major business producing and refining crude oil. The state came up 2 percentage
points short of its goal in 2010 to meet 20% of its energy needs with renewables.
With Ivanpah, California’s total solar generation capacity is raised to approximately 3,300 MW.
By comparison, the Moss Landing Power Plant, a Monterey Bay plant that burns natural gas, has
a 2,560 MW capacity. Unless renewable initiatives like Ivanpah are met with the
decommissioning of fossil fuel plants and further emissions cuts, we’ll end up turning the indoor
temperature of Arizona down three degrees while California’s Teslas and Leafs simply idle longer
on the expressway, releasing less extreme but still steady amounts of carbon into the


- See more at:

Concentrating Solar Power (CSP) plants are an amazing, wonderful, renewable energy technology, as long as
the sun is shining. However solar power alone cannot provide on-demand power, especially in the case of off-grid
applications. Aora Solar, out of Yavne, Israel, is almost complete with the world’s first ever solar hybrid plant,
which will combine concentrated solar power with a hybrid-microturbine to generate power 24 hours a day. This
technology could help provide off-grid communities the necessary power without having to run miles of costly
transmission lines.

Installation of the new hybrid system is less than 10 days away from being completed at the Kibbutz Sammar
in Israel. Once up and running on June 24th, the plant will generate 100 kW of on-demand power plus 170 kW of
thermal power. The plant consists of 30 heliostats (mirrors) that track the sun and direct its rays up to the 30meter tall tower, where all the sunlight from the heliostats is concentrated. This concentrated sunlight heats
compressed air, which drives an electric turbine. The tower itself is a welcome change from other power
towers we have seen in the past – it actually looks good with its tulip flower shape.
The hybrid part of the plant allows for on-demand power due to its inline microturbine. When the sun has set for
the day or if it is cloudy, biodiesel, natural gas, or bio fuels can be used to run the microturbine, which then drives
the electric turbine. The hybrid system has the capacity to power 70 homes 24/7.
A hybrid system like this has the potential to provide distributed generation or off-grid power to communities,
companies or factories. As production of bio fuels becomes more efficient and sustainable, we’re hoping to see
more and more hybrid solar concentrating systems.
+ Aora Solar
Via Treehugger

printemail thisemailfacebook thisfacebook this

World's Largest Solar Tower Power Plant to Be Built in California

Concentrating solar power companies Abengoa and BrightSource Energy will soon team up to build the world’s largest
solar tower facility in Southern California. The new solar

Israel Announces Plans for 121 MW Solar Power Station in the Negev Desert
Israel is blessed with abundant sunshine and has long been a pioneer in solar energy. With construction starting in early
2014 on a 121 Megawatt

ZenithSolar Creates Solar Generator with Incredible 72% Efficiency
Israel-based energy company ZenithSolar has broken records with its 3rd generation CHP solar energy generator
(Solar Z20) that combines heat and power systems to create

Read more: World’s First Hybrid Solar Power Plant Opens in Israel | Inhabitat - Sustainable Design
Innovation, Eco Architecture, Green Building

"CSP may do for fossil fuels what DVD did for VHS" - Chris Mason

Enormous quantities of energy fall as sunlight on the world’s sunny deserts and
‘concentrating solar thermal power’ (CSTP) is a proven technology for tapping in
to it (see, for example, the website of the US Government's Department of Energy
at This is not some futuristic possibility like
fusion nuclear power. CSTP is a relatively simple, mature and practical technology
that, with the right political and financial impetus, can be brought into play very
CSTP comes in four main variants:
e it

'Power towers' use a large field of sun-tracking
mirrors to concentrate sunlight on to a receiver
on the top of a low tower, to raise steam and
generate electricity.

'Trough systems' use parabolic trough-shaped
mirrors, each one of which focuses light on to a
tube containing oil or similar fluid that takes the
heat to where it can be used to raise steam and
generate electricity.

Fresnel mirror systems are similar but use
long flat mirrors at different angles to
concentrate sunlight on to a tube containing
heat-collecting fluid. In some variants,
sunlight is concentrated on to PV panels. The
School of Physics, University of Sydney, has
published an article discussing some of the
advantages of this kind of system and aspects
of its design.

Click to enlarge
Each 'dish/engine' system uses a large suntracking mirror with a Stirling engine generator at
its focal point to convert heat energy into
electricity. Sometimes, photovoltaic (PV) panels
are used to convert the concentrated sunlight to
electricity (see "Solar technologies" and "Australia
plans major solar plant"). And sometimes Fresnel
lenses are used instead of mirrors to concentrate
sunlight onto PV panels.

On a separate page, there is a brief explanation of how the parabolic trough version
of CSP works.
In CSTP plants, the heat can be stored in melted salts (eg nitrates of sodium or
potassium), and gas or biofuels may be used as a backup source of heat, so
that electricity generation may continue at night or on cloudy days (see below).
Systems like these can be installed in large numbers as 'farms' in deserts and other
sunny areas. With economies of scale,concentrating solar power is likely to be
very competitive on cost (see How much will it cost?). There is a nice fit between
wind power in northern Europe, which is greatest in the winter, and solar or wind
power from North Africa and the Middle East, which is greatest in the summer.
A report from the German Aerospace Centre shows how, even allowing for
increases in demand, a combination of CSTP with other technologies can enable
Europe to cut CO2 emissions from electricity generation by 70% by the year 2050,
and phase out nuclear power at the same time. This 'TRANS-CSP' report (and the
associated AQUA-CSP and MED-CSP reports) can be downloaded via links

Every year, each square kilometre of desert receives solar energy equivalent to 1.5
million barrels of oil.Multiplying by the area of deserts world-wide, this is several
hundred times the entire current energy consumption of the world.
Using CSP, less than 1% of the world's deserts could generate as much electricity
as the world is now using. It has been calculated that 90% of the world's population
lives within 2700 km of a desert and could be supplied with solar electricity from
The cost of collecting solar thermal energy equivalent to one barrel of oil is about
US$65 right now and it is likely to come down to around US$26 in future.
New CSTP plants are now being planned, built or are up and running in many
places around the world. The ones we know about can be seen on Google Earth,
with links back to our News page.

Desertec power is clean, safe, plentiful, inexhaustible, globally distributed,
technologically proven, quick to build, dispatchable (available on demand),
not dependent on scarce materials or dwindling supplies of fuels, with a good
EROEI,note1 and likely to become one of the cheapest sources of
electricity.note2 Few other sources of power have so many positive features.

“Energy Return on Energy Invested.” The energy payback time for CSTP plants is about 6 months.


The TRANS-CSP report from the German Aerospace Centre (DLR) calculates that CSTP in desert regions
is likely to become one of the cheapest sources of electricity throughout Europe, including the cost of

Getting the energy to where it is needed (click for more information)

It is feasible and economic to transmit solar electricity to the whole of Europe, the
Middle East and North Africa using modern high-voltage DC (HVDC)
transmission lines. Solar power may also be transported as hydrogen.
Generating electricity without the sun (click for more information)

Solar heat can be stored so that electricity generation may continue through the
night and on cloudy days.

How much will it cost? (click for more information)

CSTP electricity is likely to become one of the cheapest sources of electricity,
including the cost of transmitting it over long distances.
CSP around the world (click for more information)

At least 90% of the world's population may be supplied with clean electricity from
CSP plants in deserts around the world. There is great potential for cutting
worldwide CO2 emissions from electricity generation.
Security of supply (PDF, 45 KB)

CSP can provide greater security of supply than our current main sources of
CSTP bonuses (click for more information)

CSTP can yield much more than plentiful, inexhaustible, and secure supplies of
pollution-free electricity. A major attraction of these benefits is that, unlike money
derived from oil, most of them are of a kind that will be a direct benefit for local
people and cannot easily be hijacked by others.
Desertec and industrial processes (click for more information)

CSP can, in principle, provide the large amounts of energy needed to produce
things like aluminium, steel, cement, or synthetic fuels.
How CSTP works (click for more information)
Click the title for a brief explanation of how CSTP works, as mentioned above.
How to minimise the use of water in CSP plants (click for more information)

CSTP works best in sunny deserts where there is not normally much water but
there are ways of minimising the use of water that is normally required for steam
generation, for cooling and for cleaning solar mirrors.
How clean solar power may replace dirty kinds of power (click for more information)

Given plentiful supplies of clean clean solar power, there is scope for replacing
dirty sources of energy in transport by rail and road, in the use of synthetic fuels,
and in space heating for buildings.

Other questions about CSP (click for more information)

This section provides brief answers to some other questions that are asked about
CSP, such as how CSP plants cope with sandstorms, the materials needed to build
CSP plants, their environmental impact, and more.
CSP resources
Click the heading for links to leaflets, a slide show, a display on Google Earth showing CSP
plants around the world, and other information.

Sponsor Documents

Or use your account on


Forgot your password?

Or register your new account on


Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in