Solar Energy

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What is solar energy?
Solar energy technologies harness the
suns rays to create energy. Every year,
the sun produces approximately 1,366
watts of power per square metre of the
earth’s surface.
Solar energy is a fast growing way to harness
power, and some experts think it will contribute
to 50% of the total world’s energy use by 2050.
What types of technology harnesses
solar energy?
There are two types of solar energy devices
available today:
s r e t r e v n o c l a m r e h t r a l o s •
s r e t r e v n o c c i a t l o v o t o h p r a l o s •
How is electricity generated from
solar energy?
Solar thermal converters: Solar thermal
converters are the oldest systems of collecting
energy from the sun. Thermal converters
use dark coloured panels and sometimes
reflector panels placed on areas such as
rooftops, to absorb the heat from the sun.
The panels collect heat which in turn heats
fluid, such as oil or water. As this heated fluid
travels through the panel, it absorbs the sun’s
heat energy and produces hot liquid, or even
steam. If steam is produced, the steam turns
a turbine, creating rotational energy that is
converted into electricity by a generator.
As thermal converters need heat to create
energy and require warmer temperatures,
they work best in areas closer to the equator.
Solar photovoltaic (PV) converters: Solar
PV converters convert sunlight energy into
electricity. A typical PV panel consists of
two or more thin layers of semi-conducting
material, which is commonly silicon. PV cells
are connected together and encapsulated,
to form a module or panel. Incoming solar
rays are captured by the solar panels.
When light strikes the silicon, it produces
electrons that are conducted away by a
metallic grid as direct current (DC). This is
then sent through an inverter and converted
into alternating current (AC) electricity for
use in the home, or at school.
AN EXAMPLE OF A SOLAR FARM IN CALIFORNIA.
SOURCE: PROMETHEUS.ORG
SOLAR
This work is copyright. The copying, adapting or issuing of this work to the public on a non-proft basis is welcome. No other use of this work is permitted without the prior consent of the
copyright holder. From ElectroCity www.electrocity.co.nz © Genesis Energy 2010.
What is solar energy?
Solar energy technologies transform the
energy in sunlight into electrical and thermal
(heat) energy. The earth’s surface receives
approximately 1000 watts of power from the
sun for every square metre facing the sun.
Solar energy is a rapidly growing way to
generate electricity, and it is estimated by the
International Energy Agency that solar energy
will produce nearly a quarter of the world’s
total energy use by 2050.
Solar energy devices available today can
be put into two major classes:
• solar thermal collectors
• solar electricity
How is energy collected from the sun?
Solar thermal collectors:
These are the oldest systems of collecting
energy from the sun and make use of the heat
or thermal energy in sunlight. Solar thermal
collectors use dark coloured panels placed on
areas such as rooftops to absorb the heat
from the sun. The panels collect heat, then
transfer this heat to fuids circulating through
the panel. This is a clean and efcient way to
heat hot water. Some solar thermal collectors
use the sun’s energy to boil water into steam.
The high pressure steam spins a turbine,
creating rotational energy that is then trans-
formed into electricity by a generator.
Solar Electricity
Solar electricity systems are usually called
photovoltaics (PV) because they transform
light energy into electricity. A typical PV panel
consists of two or more thin layers of
semi-conducting material, which is commonly
silicon. PV cells are connected together and
encapsulated to form a module or panel.
Incoming solar rays are captured by the solar
panels. When light strikes the silicon, it
produces electrons that are conducted away
by a metallic grid as direct current (DC). This is
then sent through an inverter and converted
into alternating current (AC) electricity for use
in the home, or at school. Cloudy weather will
limit the amount of energy collected.
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As PV converters converts light energy
into electricity, they can be used in cooler
climates. Cloudy weather will limit the
amount of energy collected.
What are the advantages of solar energy?
Solar energy is a renewable energy resource
that can work in many weather situations.
Obviously the more sunshine hours a place
receives, the more energy generated.
Solar PV converters are one of the most
environmentally-friendly ways to generate
power today because they are silent, produce
no emissions, and require no fuel to run them.
What are the disadvantages of solar energy?
Producing electricity using solar energy is
expensive compared to the more traditional
methods. This is because solar converters
have a limited generation output, which
means low electricity production. You need
to install solar panels over a very large area
in order to get as much heat and light as
possible. Also because solar uses the sun,
generating electricity is weather dependent
and output levels change from day to day
– so it’s not a very reliable energy source,
especially over the winter period when the
days are shorter.
How is solar energy used in New Zealand?
There are currently no large-scale
commercial solar farms in New Zealand.
There are however, many independent
examples around New Zealand, where
businesses and households use solar
energy to heat water or generate power.
New Zealand receives about 2000 hours of
bright sunshine every year. This is enough
sunlight to generate approximately 4kW
per square metre every day.
ACTIVITIES
ACTIVITY ONE
Look around your school. List examples
of items that might use solar energy,
e.g., a solar calculator, solar garden lights.
ACTIVITY TWO
Students research what photovoltaic stands
for and why photovoltaic converters don’t
need the sun’s heat energy to work.
SUPPORTING RESOURCES
What are the advantages of solar energy?
Solar energy is a renewable energy resource
that can do useful work in many situations.
Obviously, the more sunshine hours a place
receives, the more energy generated.
Photovoltaics are one of the most
environmentally-friendly ways to generate
power today because they are silent, produce
no emissions while in use and require no fuel
to run them.
What are the disadvantages of solar energy?
Producing electricity using solar energy is
currently more expensive when compared to
the more traditional methods. One reason for
this is because PV panels have a limited ability
to transform all the energy in sunlight into
electricity, which decreases the electricity
production. To compensate for this, panels
must cover a larger area to collect more
sunlight. Also because solar technologies use
the sun, generating electricity is weather
dependent and output levels change from day
to day – so it’s not a very reliable energy
source, especially over the winter period when
the days are shorter.
How is solar energy used in New Zealand?
There are currently no large-scale
commercial solar farms in New Zealand.
There are however, many independent
examples around New Zealand, where
businesses and households use solar energy
to heat water or generate electricity.
Through the Schoolgen programme
Genesis Energy has installed a 2kW PV
system in 42 schools across the North Island.
New Zealand receives about 2000 hours of
bright sunshine every year. This is enough
sunlight to generate nearly 4kWh of electri-
cal energy per kilowatt of panel every day.
ACTIVITIES
ACTIVITY ONE
Look around your school. List examples of
items that might use solar energy, e.g., a
solar calculator, solar garden lights.
ACTIVITY TWO
Students research what photovoltaic stands
for and why photovoltaics don’t need the
sun’s heat energy to work.
- Australia and New Zealand Solar Energy Society: www.anzses.org/
- Energy Efciency and Conservation Authority: www.eeca.govt.nz
- Schoolgen Teacher Resources: www.schoolgen.co.nz

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