Solar Energy It is environment friendly technology...
Power System Reliability
Solar Energy Technology
Sir. Prof: M. Zahir Khan
1. 2. 3. 4. Engr. Muhammad Zafran Engr. Atiq Ur Rehman Engr. Muhammad Bashir Engr. Naveed Khan
Department of Electrical Engineering University of Engineering & Technology Peshawar, Pakistan
1 The Sun……………………………………………………………….1
History of Sun..............................................................................................1 Development of Scientific understandings………………………………...3 Observation and effects…………………………………………………….5 Characteristics……………………………………………………………...6 Internal structure of the Sun………………………………………………..8 1.5.1 Core………………………………………………………………8 1.5.2 Radiative zone……………………………………………………10 1.5.3 Convective zone………………………………………………….11 1.5.4 Photosphere………………………………………………………11 1.5.5 Atmosphere………………………………………………………12 2 What is Solar Cell?………………………………………………………….15 2.1 History of Solar cells ……………………………………………………...16 2.2 Applications………………………………………………………………..16 2.4 Theory…………………………………………….………………............. 17 2.5 Efficiency…………………………………………………………..............17 2.6 Cost………………………………………………………………………...18 2.7 Materials for Solar cel……………………………………………..............19 2.7.1 Crystalline silicon………………………………………………..19 2.7.2 Thin films………………………………………………………...20 2.7.3 Cadmium telluride solar cells…………………………………...20 2.7.4 Copper indium selenide…………………………………………21 2.7.5 Gallium arsenide multi junction………………………………...21 2.7.6 Light absorbing dyes……………………………………………22 2.8 Manufacturing techniques………………………………………………...22 2.9 Life span…………………………………………………………………..23 2.10 Manufacturers and certification…………………………………………..23 2.10.1 China……………………………………………………………24 2.10.2 United States……………………………………………………24 3 The History of Solar Energy……………………………………………....25 3.1 Timeline from 7th Century B.C.to 1200 A.D.………………………….....25 3.2 Timeline from 1767 to 1891……………………………………………...26 3.3 Timeline of solar technology in 1900s…………………………………...27 3.4 Timeline of solar technology in 2000s…………………………………...33 3.5 Recent developments in Solar technology………………………………..35 3.6 Expected future direction of solar technology……………………………36 4 Solar Energy………………………………………………………………..37 1.1 1.2 1.3 1.4 1.5
4.1 What is Solar Energy?………………………………………………….....37 4.2 The Sun is our source……………………………………………………..38 4.3 Solar energy basics………………………………………………………..39 4.3.1 Latitude and longitude…………………………………………...41 4.4 Solar thermal Vs Photovoltaic…………………………………………....42 4.5 Competing with fossil fuels………………………………………………43 4.6 Solar thermal power plant………………………………………………...44 4.6.1 ‘Solar power tower’ power plant…………………………………45 4.6.2 ‘Distributed collector system’ power plant……………………...46 4.6.3 ‘Solar chimney’ power plant…………………………………….46 4.7 Solar energy storage………………………………………………………47 4.8 Space heating……………………………………………………………...48 4.9 Space cooling……………………………………………………………...49 4.10 Land requirements…………………………………………………………49 5 Solar energy and Pakistan…………………………………………………..50 5.1 The Solar energy future……………………………………………………50 5.1.1 Methodology and assumptions…………………………………...50 5.1.2 Power generation…………………………………………………51 5.1.3 Employment……………………………………………………...52 5.2 Solar energy and Pakistan: An overview…………………………………..52 5.3 Pakistan is most suitable for solar power…………………………………..52 5.4 Pakistan’s indulgence in solar power………………………………………53 5.5 Solar activity in Pakistan…………………………………………………...54 5.6 Activities of PCRET………………………………………………………..55 5.7 Pakistan’s Solar energy development plans………………………………...56 5.8 Conclusion…………………………………………………………………..60
LIST OF FIGURES
Figure-1.1: Our galaxy system………………...……………………..………............1 Figure-1.2: Cooler stars………………........................................................................2 Figure-1.3: Sun as it appear from the surface of earth…….…………………............5 Figure-1.4: Sun’s internal structure.……………………………………….................8 Figure-1.5: Cross section of a solar type star…………………………………………9 Figure-1.6: Solar atmosphere………………………………………………………..12 Figure-1.7: Nature of plasma………………………………………………………..13 Figure-2.1: Solar cell made from mono crystalline silicon wafer…………………...15 Figure-2.2: Polycrystalline photovoltaic cells laminate……………………………..16 Figure-2.3: Polycrystalline photovoltaic cells……………………………………….17 Figure-2.4: Basic structure of silicon based solar cell and its working mech……….19 Figure-3.1: Mesa Verde Cliff dwelling………………………………………………25 Figure-3.2: An eSolar project in California and spain……………………………….35 Figure-4.1: Direct and diffuse solar radiations……………………………………....38 Figure-4.2: Brightness Vs Wavelength for various temperatures…………………...40 Figure-4.3: Sunlight transmitted through atmosphere Vs wavelength……………....41 Figure-4.4: Diagram of the Sun’s path in the sky on different ways………………..42 Figure-4.5: Parabolic dish…………………………………………………………...43 Figure-4.6: Coal reservoir…………………………………………………………...44 Figure-4.7: A central receiver solar power plant…………………………………....45 Figure-4.8: Parabolic solar collector………………………………………………...46 Figure-4.9: Parabolic trough solar power plant……………………………………...46 Figure-4.10: Chimney solar power plant……………………………………………....47 Figure-4.11: eSolar unique approach to minimize land requirements………………...49 Figure-5.1: Solar energy and Pakistan……………………………………………….50
1.1 History of Sun
Less than 5 billion years ago, in a distant spiral arm of our galaxy, called the Milky Way, a small cloud of gas and dust began to compress under its own weight. Particles within the cloud's center (core) became so densely packed that they often collided and stuck (fused) together. The fusion process released tremendous amounts of heat and light which could then combat the compressing force of gravity; eventually, the two forces reached equilibrium. The balance of fusion reactions versus gravitational collapse which occurred in this little cloud is fondly referred to as a star, and this story is about the birth and life of the closest star to Earth, the Sun.
Figure-1.1: Our galaxy system Our Sun is one of at least four hundred billion stars in the Milky Way galaxy, and it lives 8 kilo parsecs (2.5 billion miles) from the center of the galaxy. All stars in our galaxy and other galaxies come in different sizes and colors, and our sun is a medium sized star known as a yellow dwarf. The cloud from which it formed, fortunately for us, did not use all of its gas and dust to 1
make the Sun; that which was left over, less than one percent of the original material, formed the 9 planets. The Sun has been fusing hydrogen into helium and hence providing us with its radiant energy for 4.5 billion years, and it is expected to continue to do so for another 3 to 4 billion years more. And then what? As the sun gets older, it will fuse more and more hydrogen in its core. Once all of the hydrogen is turned into helium, the star stops fusing hydrogen and loses its ability to combat gravity. Then gravity begins to compress the Sun under its own weight again. The introduction of more compression causes the new helium particles inside of the core to collide hard enough so that they can stick together and fuse. The core thus begins to fuse helium into carbon to make enough energy to maintain its balance with the crushing force of gravity. The making of carbon, however, gives off more energy than did the making of helium. The energy being pumped out of the core radiates through the outer layers of the sun called the envelope. The introduction of too much energy into the envelope heats up the envelope particles so much that the envelope expands (for the same reasons that steam rises). At this point in its life, the Sun's envelope will expand to engulf all of the inner solar system out to Mars. The temperature will drop in the envelope as well, as the particles become so spread out that they no longer are colliding enough to create tremendous heat. A drop in temperature in a star can be seen in the change in the color of a star; cooler stars are redder than hotter, bluer stars. Thus, at this stage of its life, the Sun will be called a red giant.
Figure-1.2: Cooler Stars When the envelope expands too far away from the Sun's core, the envelope will begin to float off of the core and into space. This floated-off envelope material is known as a planetary nebula. Since the bulk of the Sun is envelope material, when this material floats off, gravity does not work as hard to crush the remaining core, and the core stops fusing. The particles of carbon in the core are still very densely packed, however, and so the core is very hot, but tiny about the size of the Earth. This leftover hot and tiny core will be called a white dwarf.
But for now, the Sun maintains itself as a yellow dwarf star, giving off radiation in all wavelengths of light including light we can and cannot see. It is the largest object in the solar system, yet is one of hundreds of billions of stars in our enormous galaxy.
1.2 Development of scientific understanding
In the early first millennium B.C.E., Babylonian astronomers observed that the Sun's motion along the ecliptic was not uniform, though they were unaware of why this was; it is today known that this is due to the Earth moving in an elliptic orbit around the Sun, with the Earth moving faster when it is nearer to the Sun at perihelion and moving slower when it is farther away at aphelion. One of the first people to offer a scientific or philosophical explanation for the Sun was the Greek philosopher Anaxagoras, who reasoned that it was a giant flaming ball of metal even larger than the Peloponnesus rather than the chariot of Helios, and that the Moon reflected the light of the Sun. For teaching this heresy, he was imprisoned by the authorities and sentenced to death, though he was later released through the intervention of Pericles. Eratosthenes estimated the distance between the Earth and the Sun in the 3rd century BCE as "of stadia myriads 400 and 80000", the translation of which is ambiguous, implying either 4,080,000 stadia (755,000 km) or 804,000,000 stadia (148 to 153 million kilometers); the latter value is correct to within a few percent. In the 1st century CE, Ptolemy estimated the distance as 1,210 times the Earth radius. The theory that the Sun is the center around which the planets move was first proposed by the ancient Greek Aristarchus of Samos in the 3rd century BCE, and later adopted by Seleucus of Seleucia. This largely philosophical view was developed into fully predictive mathematical model of a heliocentric system in the 16th century by Nicolaus Copernicus. In the early 17th century, the invention of the telescope permitted detailed observations of sunspots by Thomas Harriot, Galileo Galilei and other astronomers. Galileo made some of the first known telescopic observations of sunspots and posited that they were on the surface of the Sun rather than small objects passing between the Earth and the Sun. Sunspots were also observed since the Han Dynasty (206 BCE – 220 CE) by Chinese astronomers who maintained records of these observations for centuries. Averroes also provided a description of sunspots in the 12th century. Arabic astronomical contributions include Albatenius discovering that the direction of the Sun's eccentric is changing, and Ibn Yunus observing more than 10,000 entries for the Sun's position for many years using a large astrolabe. The transit of Venus was first observed in 1032 by Avicenna, who concluded that Venus is closer to the Earth than the
Sun, while one of the first observations of the transit of Mercury was conducted by Ibn Bajjah in the 12th century. In 1672 Giovanni Cassini and Jean Richer determined the distance to Mars and were thereby able to calculate the distance to the Sun. Isaac Newton observed the Sun's light using a prism, and showed that it was made up of light of many colors, while in 1800 William Herschel discovered infrared radiation beyond the red part of the solar spectrum. The 1800s saw spectroscopic studies of the Sun advance, and Joseph von Fraunhofer made the first observations of absorption lines in the spectrum, the strongest of which are still often referred to as Fraunhofer lines. When expanding the spectrum of light from the Sun, a large number of missing colors can be found. In the early years of the modern scientific era, the source of the Sun's energy was a significant puzzle. Lord Kelvin suggested that the Sun was a gradually cooling liquid body that was radiating an internal store of heat. Kelvin and Hermann von Helmholtz then proposed a gravitational contraction mechanism to explain the energy output. Unfortunately the resulting age estimate was only 20 million years, well short of the time span of at least 300 million years suggested by some geological discoveries of that time. In 1890 Joseph Lockyer, who discovered helium in the solar spectrum, proposed a meteoritic hypothesis for the formation and evolution of the Sun. Not until 1904 was a documented solution offered. Ernest Rutherford suggested that the Sun's output could be maintained by an internal source of heat, and suggested radioactive decay as the source. However, it would be Albert Einstein who would provide the essential clue to the source of the Sun's energy output with his mass-energy equivalence relation E = mc2. In 1920, Sir Arthur Eddington proposed that the pressures and temperatures at the core of the Sun could produce a nuclear fusion reaction that merged hydrogen (protons) into helium nuclei, resulting in a production of energy from the net change in mass. The preponderance of hydrogen in the Sun was confirmed in 1925 by Cecilia Payne. The theoretical concept of fusion was developed in the 1930s by the astrophysicists Subrahmanyan Chandrasekhar and Hans Bethe. Hans Bethe calculated the details of the two main energy-producing nuclear reactions that power the Sun. Finally, a seminal paper was published in 1957 by Margaret Burbidge, entitled "Synthesis of the Elements in Stars". The paper demonstrated convincingly that most of the elements in the universe had been synthesized by nuclear reactions inside stars, some like our Sun.
1.3 Observation and effects
Sunlight is very bright, and looking directly at the Sun with the naked eye for brief periods can be painful, but is not particularly hazardous for normal, non-dilated eyes. Looking directly at the Sun causes phosphene visual artifacts and temporary partial blindness. It also delivers about 4 mill watts of sunlight to the retina, slightly heating it and potentially causing damage in eyes that cannot respond properly to the brightness. UV exposure gradually yellows the lens of the eye over a period of years and is thought to contribute to the formation of cataracts, but this depends on general exposure to solar UV, not on whether one looks directly at the Sun. Long-duration viewing of the direct Sun with the naked eye can begin to cause UV-induced, sunburn-like lesions on the retina after about 100 seconds, particularly under conditions where the UV light from the Sun is intense and well focused; conditions are worsened by young eyes or new lens implants (which admit more UV than aging natural eyes), Sun angles near the zenith, and observing locations at high altitude.
Figure-1.3: The Sun as it appears from the surface of Earth
Viewing the Sun through light-concentrating optics such as binoculars is very hazardous without an appropriate filter that blocks UV and substantially dims the sunlight. An attenuating (ND) filter might not filter UV and so is still dangerous. Attenuating filters to view the Sun should be specifically designed for that use: some improvised filters pass UV or IR rays that can harm the eye at high brightness levels. Unfiltered binoculars can deliver over 500 times as much energy to the retina as using the naked eye, killing retinal cells almost instantly (even though the power per unit area of image on the retina is the same, the heat cannot dissipate fast enough because the image is larger). Even brief glances at the midday Sun through unfiltered binoculars can cause permanent blindness. Partial solar eclipses are hazardous to view because the eye's pupil is not adapted to the unusually high visual contrast: the pupil dilates according to the total amount of light in the field of view, not by the brightest object in the field. During partial eclipses most
sunlight is blocked by the Moon passing in front of the Sun, but the uncovered parts of the photosphere have the same surface brightness as during a normal day. In the overall gloom, the pupil expands from ~2 mm to ~6 mm, and each retinal cell exposed to the solar image receives about ten times more light than it would looking at the non-eclipsed Sun. This can damage or kill those cells, resulting in small permanent blind spots for the viewer. The hazard is insidious for inexperienced observers and for children, because there is no perception of pain: it is not immediately obvious that one's vision is being destroyed. During sunrise and sunset sunlight is attenuated due to Rayleigh scattering and Mie scattering from a particularly long passage through Earth's atmosphere, and the Sun is sometimes faint enough to be viewed comfortably with the naked eye or safely with optics (provided there is no risk of bright sunlight suddenly appearing through a break between clouds). Hazy conditions, atmospheric dust, and high humidity contribute to this atmospheric attenuation. A rare optical phenomenon may occur shortly after sunset or before sunrise, known as a green flash. The flash is caused by light from the Sun just below the horizon being bent (usually through a temperature inversion) towards the observer. Light of shorter wavelengths (violet, blue, green) is bent more than that of longer wavelengths (yellow, orange, red) but the violet and blue light is scattered more, leaving light that is perceived as green. Ultraviolet light from the Sun has antiseptic properties and can be used to sanitize tools and water. It also causes sunburn, and has other medical effects such as the production of vitamin D. Ultraviolet light is strongly attenuated by Earth's ozone layer, so that the amount of UV varies greatly with latitude and has been partially responsible for many biological adaptations, including variations in human skin color in different regions of the globe.
The Sun is the star at the center of the Solar System. It has a diameter of about 1,392,000 km, about 109 times that of Earth, and its mass (about 2×1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. About three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. Less than 2% consists of heavier elements, including oxygen, carbon, neon, iron, and others.
The Sun's stellar classification, based on spectral class, is G2V, and is informally designated as a yellow dwarf, because its visible radiation is most intense in the yellowgreen portion of the spectrum and although its color is white, from the surface of the Earth it may appear yellow because of atmospheric scattering of blue light. In the spectral class label, G2 indicates its surface temperature of approximately 5778 K (5505 °C), and V indicates that the Sun, like most stars, is a main sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 620 million metric tons of hydrogen each second. Once regarded by astronomers as a small and relatively insignificant star, the Sun is now thought to be brighter than about 85% of the stars in the Milky Way galaxy, most of which are red dwarfs. The absolute magnitude of the Sun is +4.83; however, as the star closest to Earth, the Sun is the brightest object in the sky with an apparent magnitude of −26.74. The Sun's hot corona continuously expands in space creating the solar wind, a stream of charged particles that extends to the heliopause at roughly 100 astronomical units. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System. The Sun is currently traveling through the Local Interstellar Cloud in the Local Bubble zone, within the inner rim of the Orion Arm of the Milky Way galaxy. Of the 50 nearest stellar systems within 17 light-years from Earth (the closest being a red dwarf named Proxima Centauri at approximately 4.2 light years away), the Sun ranks 4th in mass. The Sun orbits the center of the Milky Way at a distance of approximately 24,000–26,000 light years from the galactic center, completing one clockwise orbit, as viewed from the galactic north pole, in about 225–250 million years. Since our galaxy is moving with respect to the cosmic microwave background radiation (CMB) in the direction of constellation Hydra with a speed of 550 km/s, the sun's resultant velocity with respect to the CMB is about 370 km/s in the direction of Crater or Leo. The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (1 AU), though the distance varies as the Earth moves from perihelion in January to aphelion in July. At this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The energy of this sunlight supports almost all life on Earth by photosynthesis, and drives Earth's climate and weather. The enormous effect of the Sun on the Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. An accurate scientific understanding of the Sun developed slowly, and as recently as the 19th century prominent scientists had little knowledge of the Sun's physical composition and source of energy. This understanding is still developing; there are a number of present-day anomalies in the Sun's behavior that remain unexplained.
1.5 Internal structure of the Sun
The solar interior is not directly observable, and the Sun itself is opaque to electromagnetic radiation. However, just as seismology uses waves generated by earthquakes to reveal the interior structure of the Earth, the discipline of helioseismology makes use of pressure waves (infrasound) traversing the Sun's interior to measure and visualize the star's inner structure. Computer modeling of the Sun is also used as a theoretical tool to investigate its deeper layers.
Figure-1.4: Sun’s internal structure
An illustration of the structure of the Sun: 1. 2. 3. 4. 5. 6. 7. 8. 9. Core Radiative zone Convective zone Photosphere Chromosphere Corona Sunspot Granules Prominence
The core of the Sun is considered to extend from the center to about 20–25% of the solar radius. It has a density of up to 150 g/cm3 (about 150 times the density of water) and
a temperature of close to 13.6 million kelvin (K). By contrast, the Sun's surface temperature is approximately 5,800 K. Recent analysis of SOHO mission data favors a faster rotation rate in the core than in the rest of the radiative zone. Through most of the Sun's life, energy is produced by nuclear fusion through a series of steps called the p–p (proton–proton) chain; this process converts hydrogen into helium. Less than 2% of the helium generated in the Sun comes from the CNO cycle. The core is the only region in the Sun that produces an appreciable amount of thermal energy through fusion; inside 24% of the Sun's radius, 99% of the power has been generated, and by 30% of the radius, fusion has stopped nearly entirely. The rest of the star is heated by energy that is transferred outward from the core and the layers just outside. The energy produced by fusion in the core must then travel through many successive layers to the solar photosphere before it escapes into space as sunlight or kinetic energy of particles.
Figure-1.5: Cross-section of a solar-type star (NASA)
The proton–proton chain occurs around 9.2×1037 times each second in the core of the Sun. Since this reaction uses four free protons (hydrogen nuclei), it converts about 3.7×1038 protons to alpha particles (helium nuclei) every second (out of a total of ~8.9×1056 free protons in the Sun), or about 6.2×1011 kg per second. Since fusing hydrogen into helium releases around 0.7% of the fused mass as energy, the Sun releases energy at the mass-energy conversion rate of 4.26 million metric tons per second, 384.6 yottawatts (3.846×1026  10 W), or 9.192×10 megatons of TNT per second. This mass is not destroyed to create the energy; rather, the mass is carried away in the radiated energy, as described by the concept of mass-energy equivalence.
The power production by fusion in the core varies with distance from the solar center. At the center of the Sun, theoretical models estimate it to be approximately 276.5 watts/m3, a power production density that more nearly approximates reptile metabolism than a thermonuclear bomb. Peak power production in the Sun has been compared to the volumetric heats generated in an active compost heap. The tremendous power output of the Sun is not due to its high power per volume, but instead due to its large size. The fusion rate in the core is in a self-correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and expand slightly against the weight of the outer layers, reducing the fusion rate and correcting the perturbation; and a slightly lower rate would cause the core to cool and shrink slightly, increasing the fusion rate and again reverting it to its present level. The gamma rays (high-energy photons) released in fusion reactions are absorbed in only a few millimeters of solar plasma and then re-emitted again in random direction and at slightly lower energy. Therefore it takes a long time for radiation to reach the Sun's surface. Estimates of the photon travel time range between 10,000 and 170,000 years. After a final trip through the convective outer layer to the transparent surface of the photosphere, the photons escape as visible light. Each gamma ray in the Sun's core is converted into several million photons of visible light before escaping into space. Neutrinos are also released by the fusion reactions in the core, but unlike photons they rarely interact with matter, so almost all are able to escape the Sun immediately. For many years measurements of the number of neutrinos produced in the Sun were lower than theories predicted by a factor of 3. This discrepancy was resolved in 2001 through the discovery of the effects of neutrino oscillation: the Sun emits the number of neutrinos predicted by the theory, but neutrino detectors were missing 2⁄3 of them because the neutrinos had changed flavor by the time they were detected.
1.5.2 Radiative zone
From about 0.25 to about 0.7 solar radii, solar material is hot and dense enough that thermal radiation is sufficient to transfer the intense heat of the core outward. This zone is free of thermal convection; while the material gets cooler from 7 to about 2 million kelvin with increasing altitude, this temperature gradient is less than the value of the adiabatic lapse rate and hence cannot drive convection. Energy is transferred by radiation—ions of hydrogen and helium emit photons, which travel only a brief distance before being reabsorbed by other ions. The density drops a hundredfold (from 20 g/cm3 to only 0.2 g/cm3) from the bottom to the top of the radiative zone.
The radiative zone and the convection form a transition layer, the tachocline. This is a region where the sharp regime change between the uniform rotation of the radiative zone and the differential rotation of the convection zone results in a large shear—a condition where successive horizontal layers slide past one another. The fluid motions found in the convection zone above, slowly disappear from the top of this layer to its bottom, matching the calm characteristics of the radiative zone on the bottom. Presently, it is hypothesized (see Solar dynamo), that a magnetic dynamo within this layer generates the Sun's magnetic field.
1.5.3 Convective zone
In the Sun's outer layer, from its surface down to approximately 200,000 km (or 70% of the solar radius), the solar plasma is not dense enough or hot enough to transfer the thermal energy of the interior outward through radiation; in other words it is opaque enough. As a result, thermal convection occurs as thermal columns carry hot material to the surface (photosphere) of the Sun. Once the material cools off at the surface, it plunges downward to the base of the convection zone, to receive more heat from the top of the radiative zone. At the visible surface of the Sun, the temperature has dropped to 5,700 K and the density to only 0.2 g/m3 (about 1/6,000th the density of air at sea level). The thermal columns in the convection zone form an imprint on the surface of the Sun as the solar granulation and super granulation. The turbulent convection of this outer part of the solar interior causes a "small-scale" dynamo that produces magnetic north and south poles all over the surface of the Sun. The Sun's thermal columns are Benard cells and therefore tend to be hexagonal prisms.
The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Above the photosphere visible sunlight is free to propagate into space, and its energy escapes the Sun entirely. The change in opacity is due to the decreasing amount of H− ions, which absorb visible light easily. Conversely, the visible light we see is produced as electrons react with hydrogen atoms to produce H− ions. The photosphere is tens to hundreds of kilometers thick, being slightly less opaque than air on Earth. Because the upper part of the photosphere is cooler than the lower part, an image of the Sun appears brighter in the center than on the edge or limb of the solar disk, in a phenomenon known as limb darkening. Sunlight has approximately a blackbody spectrum that indicates its temperature is about 6,000 K, interspersed with atomic absorption lines from the tenuous layers above the photosphere. The photosphere has a particle density of ~1023 m−3 (this is about 0.37% of the particle number per volume of
Earth's atmosphere at sea level; however, photosphere particles are electrons and protons, so the average particle in air is 58 times as heavy). During early studies of the optical spectrum of the photosphere, some absorption lines were found that did not correspond to any chemical elements then known on Earth. In 1868, Norman Lockyer hypothesized that these absorption lines were because of a new element which he dubbed helium, after the Greek Sun god Helios. It was not until 25 years later that helium was isolated on Earth.
The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They can be viewed with telescopes operating across the electromagnetic spectrum, from radio through visible light to gamma rays, and comprise five principal zones: the temperature minimum, the chromosphere, the transition region, the corona, and the heliosphere. The heliosphere, which may be considered the tenuous outer atmosphere of the Sun, extends outward past the orbit of Pluto to the heliopause, where it forms a sharp shock front boundary with the interstellar medium. The chromosphere, transition region, and corona are much hotter than the surface of the Sun. The reason has not been conclusively proven; evidence suggests that Alfven waves may have enough energy to heat the corona.
Figure-1.6: Solar atmosphere During a total solar eclipse, the solar corona can be seen with the naked eye, during the brief period of totality.
The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere, with a temperature of about 4,100 K. This part of the Sun is cool enough to
support simple molecules such as carbon monoxide and water, which can be detected by their absorption spectra. Above the temperature minimum layer is a layer about 2,000 km thick, dominated by a spectrum of emission and absorption lines. It is called the chromosphere from the Greek root chroma, meaning color, because the chromosphere is visible as a colored flash at the beginning and end of total eclipses of the Sun. The temperature in the chromosphere increases gradually with altitude, ranging up to around 20,000 K near the top. In the upper part of chromosphere helium becomes partially ionized.
Figure-1.7: Nature of Plasma
(Taken by Hinode's Solar Optical Telescope, this image of the Sun reveals the filamentary nature of the plasma connecting regions of different magnetic polarity.)
Above the chromosphere, in a thin (about 200 km) transition region, the temperature rises rapidly from around 20,000 K in the upper chromosphere to coronal temperatures closer to 1,000,000 K. The temperature increase is facilitated by the full ionization of helium in the transition region, which significantly reduces radiative cooling of the plasma. The transition region does not occur at a well-defined altitude. Rather, it forms a kind of nimbus around chromospheric features such as spicules and filaments, and is in constant, chaotic motion. The transition region is not easily visible from Earth's surface, but is readily observable from space by instruments sensitive to the extreme ultraviolet portion of the spectrum. The corona is the extended outer atmosphere of the Sun, which is much larger in volume than the Sun itself. The corona continuously expands into space forming the solar wind, which fills all the Solar System. The low corona, which is very near the surface of
the Sun, has a particle density around 1015–1016 m−3. The average temperature of the corona and solar wind is about 1,000,000–2,000,000 K; however, in the hottest regions it is 8,000,000–20,000,000 K. While no complete theory yet exists to account for the temperature of the corona, at least some of its heat is known to be from magnetic reconnection. The heliosphere, which is the cavity around the Sun filled with the solar wind plasma, extends from approximately 20 solar radii (0.1 AU) to the outer fringes of the Solar System. Its inner boundary is defined as the layer in which the flow of the solar wind becomes superalfvenic, that is, where the flow becomes faster than the speed of Alfven waves. Turbulence and dynamic forces outside this boundary cannot affect the shape of the solar corona within, because the information can only travel at the speed of Alfven waves. The solar wind travels outward continuously through the heliosphere, forming the solar magnetic field into a spiral shape, until it impacts the heliopause more than 50 AU from the Sun. In December 2004, the Voyager 1 probe passed through a shock front that is thought to be part of the heliopause. Both of the Voyager probes have recorded higher levels of energetic particles as they approach the boundary.
2.1 What is Solar Cell?
A solar cell (also called photovoltaic cell) is a solid state device that converts the energy of sunlight directly into electricity by the photovoltaic effect. Assemblies of cells are used to make solar modules, also known as solar panels. The energy generated from these solar modules, referred to as solar power, is an example of solar energy.
Figure-2.1: A solar cell made from a mono crystalline silicon wafer Photovoltaic is the field of technology and research related to the practical application of photovoltaic cells in producing electricity from light, though it is often used specifically to refer to the generation of electricity from sunlight. Cells are described as photovoltaic cells when the light source is not necessarily sunlight. These are used for detecting light or other electromagnetic radiation near the visible range, for example infrared detectors, or measurement of light intensity.
2.2 History of solar cells
The term "photovoltaic" comes from the Greek φῶς (phōs) meaning "light", and "voltaic", meaning electric, from the name of the Italian physicist Volta, after whom a unit of electro-motive force, the volt, is named. The term "photo-voltaic" has been in use in English since 1849. The photovoltaic effect was first recognized in 1839 by French physicist A. E. Becquerel. However, it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only around 1% efficient. In 1888 Russian physicist Aleksandr Stoletov built the first photoelectric cell (based on the outer photoelectric effect discovered by Heinrich Hertz earlier in 1887). Albert Einstein explained the photoelectric effect in 1905 for which he received the Nobel prize in Physics in 1921. Russell Ohl patented the modern junction semiconductor solar cell in 1946, which was discovered while working on the series of advances that would lead to the transistor. The photovoltaic cell was developed in 1954 at Bell Laboratories. The highly efficient solar cell was first developed by Daryl Chapin, Calvin Souther Fuller and Gerald Pearson in 1954 using a diffused silicon p-n junction. In the past four decades, remarkable progress has been made, with Megawatt solar power generating plants having now been built.
Solar cells are often electrically connected and encapsulated as a module. Photovoltaic modules often have a sheet of glass on the front (sun up) side, allowing light to pass while protecting the semiconductor wafers from abrasion and impact due to wind-driven debris, rain, hail, et cetera. Solar cells are also usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will yield a higher current. Modules are then interconnected, in series or parallel, or both, to create an array with the desired peak DC voltage and current.
Figure-2.2: Polycrystalline photovoltaic cells laminated to backing material in a module
To make practical use of the solar-generated energy, the electricity is most often fed into the electricity grid using inverters (grid-connected photovoltaic systems); in stand-alone systems, batteries are used to store the energy that is not needed immediately. Solar panels can be used to power or recharge portable devices.
Figure-2.3: Polycrystalline photovoltaic cells
The solar cell works in three steps: 1. Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon. 2. Electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity. Due to the special composition of solar cells, the electrons are only allowed to move in a single direction. 3. An array of solar cells converts solar energy into a usable amount of direct current (DC) electricity.
The efficiency of a solar cell may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. The overall efficiency is the product of each of these individual efficiencies. Due to the difficulty in measuring these parameters directly, other parameters are measured instead: thermodynamic efficiency, quantum efficiency, VOC ratio, and fill factor. Reflectance losses are a portion of the quantum efficiency under "external quantum efficiency". Recombination losses make up a portion of the quantum efficiency, VOC ratio, and fill factor. Resistive losses are predominantly categorized under fill factor, but also make up minor portions of the quantum efficiency, VOC ratio. 17
Crystalline silicon devices are now approaching the theoretical limiting efficiency of 29%.
The cost of a solar cell is given per unit of peak electrical power. Manufacturing costs necessarily including the cost of energy required for manufacture. Solar-specific feed in tariffs vary worldwide, and even state by state within various countries. Such feed-in tariffs can be highly effective in encouraging the development of solar power projects. High-efficiency solar cells are of interest to decrease the cost of solar energy. Many of the costs of a solar power plant are proportional to the area of the plant; a higher efficiency cell may reduce area and plant cost, even if the cells themselves are more costly. Efficiencies of bare cells, to be useful in evaluating solar power plant economics, must be evaluated under realistic conditions. The basic parameters that need to be evaluated are the short circuit current, open circuit voltage. The chart at the right illustrates the best laboratory efficiencies obtained for various materials and technologies, generally this is done on very small, i.e. one square cm, cells. Commercial efficiencies are significantly lower. A low-cost photovoltaic cell is a thin-film cell intended to produce electrical energy at a price competitive with traditional (fossil fuels and nuclear power) energy sources. This includes second and third generation photovoltaic cells, that is cheaper than first generation (crystalline silicon cells, also called wafer or bulk cells). Grid parity, the point at which photovoltaic electricity is equal to or cheaper than grid power, can be reached using low cost solar cells. It is achieved first in areas with abundant sun and high costs for electricity such as in California and Japan. Grid parity has been reached in Hawaii and other islands that otherwise use diesel fuel to produce electricity. George W. Bush had set 2015 as the date for grid parity in the USA. Speaking at a conference in 2007, General Electric's Chief Engineer predicted grid parity without subsidies in sunny parts of the United States by around 2015. The price of solar panels fell steadily for 40 years, until 2004 when high subsidies in Germany drastically increased demand there and greatly increased the price of purified silicon (which is used in computer chips as well as solar panels). One research firm predicted that new manufacturing capacity began coming on-line in 2008 (projected to double by 2009) which was expected to lower prices by 70% in 2015. Other analysts warned that capacity may be slowed by economic issues, but that demand may fall because of lessening subsidies. Other potential bottlenecks which have been suggested are the capacity of ingot shaping and wafer slicing industries, and the supply of specialist chemicals used to coat the cells.
2.7 Materials for Solar Cell
Different materials display different efficiencies and have different costs. Materials for efficient solar cells must have characteristics matched to the spectrum of available light. Some cells are designed to efficiently convert wavelengths of solar light that reach the Earth surface. However, some solar cells are optimized for light absorption beyond Earth's atmosphere as well. Light absorbing materials can often be used in multiple physical configurations to take advantage of different light absorption and charge separation mechanisms. Materials presently used for photovoltaic solar cells include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium selenide/sulfide. Many currently available solar cells are made from bulk material that are cut into wafers between 180 to 240 micrometers thick that are then processed like other semiconductors. Other materials are made as thin-films layers, organic dyes, and organic polymers that are deposited on supporting substrates. A third group are made from nano crystals and used as quantum dots (electron-confined nano particles). Silicon remains the only material that is wellresearched in both bulk and thin-film forms.
2.7.1 Crystalline silicon
By far, the most prevalent bulk material for solar cells is crystalline silicon (abbreviated as a group as c-Si), also known as "solar grade silicon". Bulk silicon is separated into multiple categories according to crystallinity and crystal size in the resulting ingot, ribbon, or wafer.
Figure-2.4: Basic structure of a silicon based solar cell and its working mechanism. 19
Monocrystalline silicon (c-Si): Often made using the Czochralski process. Singlecrystal wafer cells tend to be expensive, and because they are cut from cylindrical ingots, do not completely cover a square solar cell module without a substantial waste of refined silicon. Hence most c-Si panels have uncovered gaps at the four corners of the cells. 2. Poly- or multi crystalline silicon (poly-Si or mc-Si): Made from cast square ingots — large blocks of molten silicon carefully cooled and solidified. Poly-Si cells are less expensive to produce than single crystal silicon cells, but are less efficient. US DOE data shows that there were a higher number of multi crystalline sales than mono crystalline silicon sales. 3. Ribbon silicon] is a type of multi crystalline silicon: It is formed by drawing flat thin films from molten silicon and results in a multi crystalline structure. These cells have lower efficiencies than poly-Si, but save on production costs due to a great reduction in silicon waste, as this approach does not require sawing from ingots. Analysts have predicted that prices of polycrystalline silicon will drop as companies build additional polysilicon capacity quicker than the industry’s projected demand. On the other hand, the cost of producing upgraded metallurgical-grade silicon, also known as UMG Si, can potentially be one-sixth that of making polysilicon. Manufacturers of wafer-based cells have responded to thin-film lower prices with rapid reductions in silicon consumption. According to Jef Poortmans, director of IMEC's organic and solar department, current cells use between eight and nine grams of silicon per watt of power generation, with wafer thicknesses in the neighborhood of 0.200 mm. At 2008 spring's IEEE Photovoltaic Specialists' Conference (PVS'08), John Wohlgemuth, staff scientist at BP Solar, reported that his company has qualified modules based on 0.180 mm thick wafers and is testing processes for 0.16 mm wafers cut with 0.1 mm wire. IMEC's roadmap, presented at the organization's recent annual research review meeting, envisions use of 0.08 mm wafers by 2015.
2.7.2 Thin films
Thin-film technologies reduce the amount of material required in creating a solar cell. Though this reduces material cost, it may also reduce energy conversion efficiency. Thin-film silicon cells have become popular due to cost, flexibility, lighter weight, and ease of integration, compared to wafer silicon cells.
2.7.3 Cadmium telluride solar cell
A cadmium telluride solar cell use a cadmium telluride (CdTe) thin film, a semiconductor layer to absorb and convert sunlight into electricity. Solarbuzz has reported that the lowest quoted thin-film module price stands at US$1.76 per watt-peak, with the lowest crystalline silicon (c-Si) module at $2.48 per watt-peak. 20
The cadmium present in the cells would be toxic if released. However, release is impossible during normal operation of the cells and is unlikely during ﬁres in residential roofs. A square meter of CdTe contains approximately the same amount of Cd as a single C cell Nickel-cadmium battery, in a more stable and less soluble form.
2.7.4 Copper-Indium Selenide
Copper indium gallium selenide (CIGS) is a direct-bandgap material. It has the highest efficiency (~20%) among thin film materials (see CIGS solar cells). Traditional methods of fabrication involve vacuum processes including co-evaporation and sputtering. Recent developments at IBM and Nanosolar have been targeting to lower the cost by using non-vacuum solution processes.
2.7.5 Gallium arsenide multi junction
High-efficiency multijunction cells were originally developed for special applications such as satellites and space exploration, but at present, their use in terrestrial concentrators might be the lowest cost alternative in terms of $/kWh and $/W. These multijunction cells consist of multiple thin films produced using metalorganic vapour phase epitaxy. A triple-junction cell, for example, may consist of the semiconductors: GaAs, Ge, and GaInP2. Each type of semiconductor will have a characteristic band gap energy which, loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorb electromagnetic radiation over a portion of the spectrum. The semiconductors are carefully chosen to absorb nearly all of the solar spectrum, thus generating electricity from as much of the solar energy as possible. GaAs based multijunction devices are the most efficient solar cells to date, reaching a record high of 40.7% efficiency under "500-sun" solar concentration and laboratory conditions. This was surpassed in October 2010 with a 42.3% triple junction metamorphic cell. This technology is currently being utilized in the Mars Exploration Rover missions which have run far past their 90 day design life. Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and germanium Ge pn junctions, are seeing demand rapidly rise. In just the past 12 months (12/2006 - 12/2007), the cost of 4N gallium metal has risen from about $350 per kg to $680 per kg. Additionally, germanium metal prices have risen substantially to $1000– $1200 per kg this year. Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N, 6N and 7N) and germanium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and boron oxide, these products are critical to the entire substrate manufacturing industry. Triple-junction GaAs solar cells were also being used as the power source of the Dutch fourtime World Solar Challenge winners Nuna in 2003, 2005 and 2007, and also by the Dutch solar cars Solutra (2005), Twente One (2007) and 21Revolution (2009). 21
The Dutch Radboud University Nijmegen set the record for thin film solar cell efficiency using a single junction GaAs to 25.8% in August 2008 using only 4 µm thick GaAs layer which can be transferred from a wafer base to glass or plastic film.
2.7.6 Light-absorbing dyes (DSSC)
Dye-sensitized solar cells (DSSCs) are made of low-cost materials and do not need elaborate equipment to manufacture, so they can be made in a DIY fashion, possibly allowing players to produce more of this type of solar cell than others. In bulk it should be significantly less expensive than older solid-state cell designs. DSSC's can be engineered into flexible sheets, and although its conversion efficiency is less than the best thin film cells, its price/performance ratio should be high enough to allow them to compete with fossil fuel electrical generation. The DSSC has been developed by Prof. Michael Gratzel in 1991 at the Swiss Federal Institute of Technology (EPFL) in Lausanne (CH). Typically a ruthenium metalorganic dye (Ru-centered) is used as a monolayer of lightabsorbing material. The dye-sensitized solar cell depends on a mesoporous layer of nanoparticulate titanium dioxide to greatly amplify the surface area (200–300 m2/g TiO2, as compared to approximately 10 m2/g of flat single crystal). The photogenerated electrons from the light absorbing dye are passed on to the n-type TiO2, and the holes are absorbed by an electrolyte on the other side of the dye. The circuit is completed by a redox couple in the electrolyte, which can be liquid or solid. This type of cell allows a more flexible use of materials, and is typically manufactured by screen printing and/or use of Ultrasonic Nozzles, with the potential for lower processing costs than those used for bulk solar cells. However, the dyes in these cells also suffer from degradation under heat and UV light, and the cell casing is difficult to seal due to the solvents used in assembly. In spite of the above, this is a popular emerging technology with some commercial impact forecast within this decade. The first commercial shipment of DSSC solar modules occurred in July 2009 from G24i Innovations (www.g24i.com).
2.8 Manufacturing techniques
Because solar cells are semiconductor devices, they share many of the same processing and manufacturing techniques as other semiconductor devices such as computer and memory chips. However, the stringent requirements for cleanliness and quality control of semiconductor fabrication are a little more relaxed for solar cells. Most large-scale commercial solar cell factories today make screen printed poly-crystalline silicon solar cells. Single crystalline wafers which are used in the semiconductor industry can be made into excellent high efficiency solar cells, but they are generally considered to be too expensive for large-scale mass production. Poly-crystalline silicon wafers are made by wire-sawing block-cast silicon ingots into very thin (180 to 350 micrometer) slices or wafers. The wafers are usually lightly p-type doped. To make a solar cell from the wafer, a surface diffusion of n-type dopants is performed on the front side of the wafer. This forms a p-n junction a few hundred nanometers below the surface. 22
Antireflection coatings, to increase the amount of light coupled into the solar cell, are typically next applied. Silicon nitride has gradually replaced titanium dioxide as the antireflection coating because of its excellent surface passivation qualities. It prevents carrier recombination at the surface of the solar cell. It is typically applied in a layer several hundred nanometers thick using plasma-enhanced chemical vapor deposition (PECVD). Some solar cells have textured front surfaces that, like antireflection coatings, serve to increase the amount of light coupled into the cell. Such surfaces can usually only be formed on single-crystal silicon, though in recent years methods of forming them on multicrystalline silicon have been developed. The wafer then has a full area metal contact made on the back surface, and a grid-like metal contact made up of fine "fingers" and larger "busbars" are screen-printed onto the front surface using a silver paste. The rear contact is also formed by screen-printing a metal paste, typically aluminium. Usually this contact covers the entire rear side of the cell, though in some cell designs it is printed in a grid pattern. The paste is then fired at several hundred degrees Celsius to form metal electrodes in ohmic contact with the silicon. Some companies use an additional electroplating step to increase the cell efficiency. After the metal contacts are made, the solar cells are interconnected in series (and/or parallel) by flat wires or metal ribbons, and assembled into modules or "solar panels". Solar panels have a sheet of tempered glass on the front, and a polymer encapsulation on the back.
Most commercially available solar cells are capable of producing electricity for at least twenty years without a significant decrease in efficiency. The typical warranty given by panel manufacturers is for a period of 25 – 30 years, wherein the output shall not fall below a specified percentage (around 80%) of the rated capacity.
2.10 Manufacturers and certification
Solar cells are manufactured primarily in Japan, Germany, Mainland China, Taiwan and United States, though numerous other nations have or are acquiring significant solar cell production capacity. While technologies are constantly evolving toward higher efficiencies, the most effective cells for low cost electrical production are not necessarily those with the highest efficiency, but those with a balance between low-cost production and efficiency high enough to minimize area-related balance of systems cost. Those companies with large scale manufacturing technology for coating inexpensive substrates may, in fact, ultimately be the lowest cost net electricity producers, even with cell efficiencies that are lower than those of single-crystal technologies.
Backed by Chinese government's unprecedented plan to offer subsidies for utility-scale solar power projects that is likely to spark a new round of investment from Chinese solar panel makers. Chinese companies have already played a more important role in solar panels manufacturing in recent years. China produced solar cells/modules with an output of 1,180 MW in 2007 making it the largest producer in the world, according to statistics from China Photovoltaic Association. Some Chinese companies such as Suntech Power, Yingli, LDK Solar Co, JA Solar and ReneSola have already announced projects in cooperation with regional governments with hundreds of megawatts each after the ‘Golden Sun’ incentive program was announced by the government. The new development of solar module manufacturers with thin-film technology such as Veeco and Anwell Technologies Limited will further help to boost the domestic solar industry.
2.10.2 United States
New manufacturing facilities for solar cells and modules in Massachusetts, Michigan, New York, Ohio, Oregon, and Texas promise to add enough capacity to produce thousands of megawatts of solar devices per year within the next few years from 2008. In late September 2008, Sanyo Electric Company, Ltd. announced its decision to build a manufacturing plant for solar ingots and wafers in Salem, Oregon. The plant will begin operating in October 2009 and will reach its full production capacity of 70 megawatts (MW) of solar wafers per year by April 2010. In early October 2008, First Solar, Inc. broke ground on an expansion of its Perrysburg, Ohio, facility that will add enough capacity to produce another 57 MW per year of solar modules at the facility, bringing its total capacity to roughly 192 MW per year. The company expects to complete construction early next year and reach full production by mid-2010. In mid-October 2008, SolarWorld AG opened a manufacturing plant in Hillsboro, Oregon, that is expected to produce 500 MW of solar cells per year when it reaches full production in 2011. In March 2010, SpectraWatt, Inc. began production at its manufacturing plant in Hopewell Junction, NY, which is expected to produce 120 MW of solar cells per year when it reaches full production in 2011.
The History of Solar Energy
Solar technology isn’t new. Its history spans from the 7th Century B.C. to today. We started out concentrating the sun’s heat with glass and mirrors to light fires. Today, we have everything from solar-powered buildings to solar powered vehicles. Here is about the milestones in the historical development of solar technology, century by century, and year by year.
Figure-3.1: Mesa Verde cliff dwellings
3.1 Timeline from 7th Century B.C. to 1200 A.D.
7th Century B.C.
Magnifying glass used to concentrate sun’s rays to make fire and to burn ants.
3rd Century B.C.
Magnifying glass used to concentrate sun’s rays to make fire and to burn ants.Greeks and Romans use burning mirrors to light torches for religious purposes.
2nd Century B.C.
Magnifying glass used to concentrate sun’s rays to make fire and to burn ants. Greeks and Romans use burning mirrors to light torches for religious purposes. As early as 212 BC, the Greek 25
scientist, Archimedes, used the reflective properties of bronze shields to focus sunlight and to set fire to wooden ships from the Roman Empire which were besieging Syracuse. (Although no proof of such a feat exists, the Greek navy recreated the experiment in 1973 and successfully set fire to a wooden boat at a distance of 50 meters.)
Chinese document use of burning mirrors to light torches for religious purposes.
1st to 4th Century A.D.
The famous Roman bathhouses in the first to fourth centuries A.D. had large south facing windows to let in the sun’s warmth.
6th Century A.D.
Sunrooms on houses and public buildings were so common that the Justinian Code initiated “sun rights” to ensure individual access to the sun.
Ancestors of Pueblo people called Anasazi in North America live in south-facing cliff dwellings that capture the winter sun.
3.2 Timeline from 1767 to 1891.
Swiss scientist Horace de Saussure was credited with building the world’s firstsolar collector, later used by Sir John Herschel to cook food during his South Africa expedition in the 1830s.
On September 27, 1816, Robert Stirling applied for a patent for his economizer at the Chancery in Edinburgh, Scotland. By trade, Robert Stirling was actually a minister in the Church of Scotland and he continued to give services until he was eighty-six years old! But, in his spare time, he built heat engines in his home workshop. Lord Kelvin used one of the working models during some of his university classes. This engine was later used in the dish/Stirling system, a solar thermal electric technology that concentrates the sun’s thermal energy in order to produce power.
French scientist Edmond Becquerel discovers the photovoltaic effect while experimenting with an electrolytic cell made up of two metal electrodes placed in an electricity-conducting solution, electricity-generation increased when exposed to light.
French mathematician August Mouchet proposed an idea for solar-powered steam engines. In the following two decades, he and his assistant, Abel Pifre, constructed the first solar powered engines and used them for a variety of applications. These engines became the predecessors of modern parabolic dish collectors.
Willoughby Smith discovered the photoconductivity of selenium.
1876 William Grylls Adams and Richard Evans Day discover that selenium produces electricity when exposed to light. Although selenium solar cells failed to convert enough sunlight to power electrical equipment, they proved that asolid material could change light into electricity without heat or moving parts.
Samuel P. Langley, invents the bolometer, which is used to measure light from the faintest stars and the sun’s heat rays. It consists of a fine wire connected to an electric circuit. When radiation falls on the wire, it becomes very slightly warmer. This increases the electrical resistance of the wire.
Charles Fritts, an American inventor, described the first solar cells made from selenium wafers.
Heinrich Hertz discovered that ultraviolet light altered the lowest voltage capable of causing a spark to jump between two metal electrodes.
Baltimore inventor Clarence Kemp patented the first commercial solar water heater.
3.3 Timeline of solar technology in the 1900s.
Wilhelm Hallwachs discovered that a combination of copper and cuprous oxide is photosensitive.
Albert Einstein published his paper on the photoelectric effect (along with a paper on his theory of relativity).
1908 William J. Bailley of the Carnegie Steel Company invents a solar collector with copper coils and an insulated box—roughly, it’s present design.
The existence of a barrier layer in photovoltaic devices was noted.
Robert Millikan provided experimental proof of the photoelectric effect.
Polish scientist Jan Czochralski developed a way to grow single-crystal silicon.
Albert Einstein wins the Nobel Prize for his theories (1904 research and technical paper) explaining the photoelectric effect.
Audobert and Stora discover the photovoltaic effect in cadmium sulfide (CdS). 27
1947 Passive solar buildings in the United States were in such demand, as a result of scarce energy during the prolonged W.W.II, that Libbey-Owens-Ford Glass Company published a book entitled Your Solar House, which profiled forty-nine of the nation’s greatest solar architects.
Dr. Dan Trivich, Wayne State University, makes the first theoretical calculations of the efficiencies of various materials of different band gap widths based on the spectrum of the sun.
1954 Photovoltaic technology is born in the United States when Daryl Chapin, Calvin Fuller, and Gerald Pearson develop the silicon photovoltaic (PV) cell at Bell Labs—the first solar cell capable of converting enough of the sun’s energy into power to run everyday electrical equipment. Bell Telephone Laboratories produced a silicon solar cell with 4% efficiency and later achieved 11% efficiency.
Western Electric began to sell commercial licenses for silicon photovoltaic (PV) technologies. Early successful products included PV-powered dollar bill changers and devices that decoded computer punch cards and tape.
Architect Frank Bridgers designed the world’s first commercial office building using solar water heating and passive design. This solar system has been continuously operating since that time and the Bridgers-Paxton Building, is now in the National Historic Register as the world’s first solar heated office building.
William Cherry, U.S. Signal Corps Laboratories, approaches RCA Labs’ Paul Rappaport and Joseph Loferski about developing photovoltaic cells for proposed orbiting Earth satellites.
1. T. Mandelkorn, U.S. Signal Corps Laboratories, fabricates n-on-p silicon photovoltaic cells (critically important for space cells; more resistant to radiation). 2. Hoffman Electronics achieves 9% efficient photovoltaic cells. 3. The Vanguard I space satellite used a small (less than one watt) array to power its radios. Later that year, Explorer III, Vanguard II, and Sputnik-3 were launched with PV-powered systems on board. Despite faltering attempts to commercialize the silicon solar cell in the 1950s and 60s, it was used successfully in powering satellites. It became the accepted energy source for space applications and remains so today.
1. Hoffman Electronics achieves 10% efficient, commercially available photovoltaic cells. Hoffman also learns to use a grid contact, reducing the series resistance significantly. 2. On August 7, the Explorer VI satellite is launched with a photovoltaic array of 9600 cells (1 cm x 2 cm each). Then, on October 13, the Explorer VII satellite is launched.
1. Hoffman Electronics achieves 14% efficient photovoltaic cells. 2. Silicon Sensors, Inc., of Dodgeville, Wisconsin, is founded. It starts producing selenium and silicon photovoltaic cells.
Bell Telephone Laboratories launches the first telecommunications satellite, the Telstar (initial power 14 watts).
1. Sharp Corporation succeeds in producing practical silicon photovoltaic modules. 2. Japan installs a 242-watt, photovoltaic array on a lighthouse, the world’s largest array at that time.
NASA launches the first Nimbus spacecraft—a satellite powered by a 470-watt photovoltaic array.
Peter Glaser conceives the idea of the satellite solar power station.
NASA launches the first Orbiting Astronomical Observatory, powered by a 1-kilowatt photovoltaic array, to provide astronomical data in the ultraviolet and X-ray wavelengths filtered out by the earth’s atmosphere.
The Odeillo solar furnace, located in Odeillo, France was constructed. story parabolic mirror. This featured an 8-
Dr. Elliot Berman, with help from Exxon Corporation, designs a significantly less costly solar cell, bringing price down from $100 a watt to $20 a watt. Solar cells begin to power navigation warning lights and horns on many offshore gas and oil rigs, lighthouses, railroad crossings and domestic solar applications began to be viewed as sensible applications in remote locations where grid connected utilities could not exist affordably.
1. The French install a cadmium sulfide (CdS) photovoltaic system to operate an educational television at a village school in Niger.
2. The Institute of Energy Conversion is established at the University of Delaware to perform research and development on thin-film photovoltaic (PV) and solar thermal systems, becoming the world’s first laboratory dedicated to PV research and development.
The University of Delaware builds “Solar One,” one of the world’s first photovoltaic (PV) powered residences. The system is a PV/thermal hybrid. The roof-integrated arrays fed surplus power through a special meter to the utility during the day and purchased power from the utility at night. In addition to electricity, the arrays acted as flat-plate thermal collectors, with fans blowing the warm air from over the array to phase-change heat-storage bins.
1. The NASA Lewis Research Center starts installing 83 photovoltaic power systems on every continent except Australia. These systems provide such diverse applications as vaccine refrigeration, room lighting, medical clinic lighting, telecommunications, water pumping, grain milling, and classroom television. The Center completed the project in 1995, working on it from 1976-1985 and then again from 1992-1995. 2. David Carlson and Christopher Wronski, RCA Laboratories, fabricate first amorphous silicon photovoltaic cells.
1. The U.S. Department of Energy launches the Solar Energy Research Institute http://www.nrel.gov/ “National Renewable Energy Laboratory”, a federal facility dedicated to harnessing power from the sun. 2. Total photovoltaic manufacturing production exceeds 500 kilowatts.
1978 NASA’s Lewis Research Center dedicates a 3.5-kilowatt photovoltaic (PV) system it installed on the Papago Indian Reservation located in southern Arizona—the world’s first village PV system. The system is used to provide for water pumping and residential electricity in 15 homes until 1983, when grid power reached the village. The PV system was then dedicated to pumping water from a community well.
1. ARCO Solar becomes the first company to produce more than 1 megawatt of photovoltaic modules in one year. 2. At the University of Delaware, the first thin-film solar cell exceeds 10% efficiency using copper sulfide/cadmium sulfide.
Paul MacCready builds the first solar-powered aircraft—the Solar Challenger—and flies it from France to England across the English Channel. The aircraft had over 16,000 solar cells mounted on its wings, which produced 3,000 watts of power. The Smithsonian Institute National Air and Space Museum has a photo of the http://www.nasm.edu/nasm/aero/aircraft/maccread.htm “Solar Challenger” in flight.
1. The first, photovoltaic megawatt-scale power station goes on-line in Hisperia, California. It has a 1-megawatt capacity system, developed by ARCO Solar, with modules on 108 dual-axis trackers. 2. Australian Hans Tholstrup drives the first solar-powered car—the Quiet Achiever— almost 2,800 miles between Sydney and Perth in 20 days—10 days faster than the first gasoline-powered car to do so. Tholstrup is the founder of the http://www.wsc.org.au/2003/home.solar “World Solar Challenge” in Australia, considered the world championship of solar car racing. 3. The U.S. Department of Energy, along with an industry consortium, begins operating Solar One, a 10-megawatt central-receiver demonstration project. The project established the feasibility of power-tower systems, a solar-thermal electric or concentrating solar power technology. In 1988, the final year of operation, the system could be dispatched 96% of the time. 4. Volkswagen of Germany begins testing photovoltaic arrays mounted on the roofs of Dasher station wagons, generating 160 watts for the ignition system. 5. The Florida Solar Energy Center’s http://www.fsec.ucf.edu/About/quals/index.htm#recentcon “Southeast Residential Experiment Station” begins supporting the U.S. Department ofEnergy’s photovoltaics program in the application of systems engineering. 6. Worldwide photovoltaic production exceeds 9.3 megawatts.
1. ARCO Solar dedicates a 6-megawatt photovoltaic substation in central California. The 120-acre, unmanned facility supplies the Pacific Gas & Electric Company’s utility grid with enough power for 2,000-2,500 homes. 2. Solar Design Associates completes a stand-alone, 4-kilowatt powered home in the Hudson River Valley. 3. Worldwide photovoltaic production exceeds 21.3 megawatts, with sales of more than $250 million.
The Sacramento Municipal Utility District commissions its first 1-megawatt photovoltaic electricity generating facility.
The University of South Wales breaks the 20% efficiency barrier for silicon solar cells under 1-sun conditions.
1. 1986 The world’s largest solar thermal facility, located in Kramer Junction, California, was commissioned. The solar field contained rows of mirrors that concentrated the sun’s energy onto a system of pipes circulating a heat transfer fluid. The heat transfer fluid was used to produce steam, which powered a conventional turbine to generate electricity. 2. ARCO Solar releases the G-4000—the world’s first commercial thin-film power module.
Dr. Alvin Marks receives patents for two solar power technologies he developed: Lepcon and Lumeloid. Lepcon consists of glass panels covered with a vast array of millions of aluminum or copper strips, each less than a micron or thousandth of a millimeter wide. As sunlight hits the metal strips, the energy in the light is transferred to electrons in the metal, which escape at one end in the form of electricity. Lumeloid uses a similar approach but substitutes cheaper, film-like sheets of plastic for the glass panels and covers the plastic with conductive polymers, long chains of molecular plastic units.
1. 1992 University of South Florida develops a 15.9% efficient thin-film photovoltaic cell made of cadmium telluride, breaking the 15% barrier for the first time for this technology. 2. A 7.5-kilowatt prototype dish system using an advanced stretched-membrane concentrator becomes operational.
1993 Pacific Gas & Electric completes installation of the first grid-supported photovoltaic system in Kerman, California. The 500-kilowatt system was the first “distributed power” effort.
1. First solar dish generator using a free-piston Stirling engine is tied to a utility grid. 2. The National Renewable Energy Laboratory develops a solar cell—made from gallium indium phosphide and gallium arsenide—that becomes the first one to exceed 30% conversion efficiency.
1. The world’s most advanced solar-powered airplane, the Icare, flew over Germany. The wings and tail surfaces of the Icare are covered by 3,000 super-efficient solar cells, with a total area of 21 m2. 2. The U.S. Department of Energy, along with an industry consortium, begins operating Solar Two—an upgrade of its Solar One concentrating solar powertower project. Operated until 1999, Solar Two demonstrated how solar energy can be stored efficiently and economically so that power can be produced even when the sun isn’t shining. It also fostered commercial interest in power towers.
1. The remote-controlled, solar-powered aircraft, “Pathfinder” sets an altitude record, 80,000 feet, on its 39th consecutive flight on August 6, in Monrovia, California. This altitude is higher than any prop-driven aircraft thus far. 2. Subhendu Guha, a noted scientist for his pioneering work in amorphous silicon, led the invention of flexible solar shingles, a roofing material and state-of-the-art technology for converting sunlight to electricity.
1. 1999 Construction was completed on 4 Times Square, the tallest skyscraper built in the 1990s in New York City. It incorporates more energy-efficient building techniques than any other commercial skyscraper and also includes building-integrated photovoltaic 32
(BIPV) panels on the 37th through 43rd floors on the southand west-facing facades that produce a portion of the buildings power. 2. Spectrolab, Inc. and the National Renewable Energy Laboratory develop a photovoltaic solar cell that converts 32.3 percent of the sunlight that hits it into electricity. The high conversion efficiency was achieved by combining three layers of photovoltaic materials into a single solar cell. The cell performed most efficiently when it received sunlight concentrated to 50 times normal. To use such cells in practical applications, the cell is mounted in a device that uses lenses or mirrors to concentrate sunlight onto the cell. Such “concentrator” systems are mounted on tracking systems that keep them pointed toward the sun. 3. The National Renewable Energy Laboratory of US achieves a new efficiency record for thin-film photovoltaic solar cells. The measurement of 18.8 percent efficiency for the prototype solar cell topped the previous record by more than 1 percent. 4. Cumulative worldwide installed photovoltaic capacity reaches 1000 megawatts.
3.4 Timeline solar technology in the 2000s.
1. First Solar begins production in Perrysburg, Ohio, at the world’s largest photovoltaic manufacturing plant with an estimated capacity of producing enough solar panels each year to generate 100 megawatts of power. 2. At the International Space Station, astronauts begin installing solar panels on what will be the largest solar power array deployed in space. Each “wing” of the array consists of 32,800 solar cells. 3. Sandia National Laboratories develops a new inverter for solar electric systems that will increase the safety of the systems during a power outage. Inverters convert the direct current (DC) electrical output from solar systems into alternating current (AC), which is the standard current for household wiring and for the power lines that supply electricity to homes. 4. Two new thin-film solar modules, developed by BP Solarex, break previous performance records. The company’s 0.5-square-meter module achieves 10.8 % conversion efficiency—the highest in the world for thin-film modules of its kind. And its 0.9-squaremeter module achieved 10.6% conversion efficiency and a power output of 91.5 watts — the highest power output for any thin-film module in the world. 5. A family in Morrison, Colorado, installs a 12-kilowatt solar electric system on its home— the largest residential installation in the United States to be registered with the U.S. Department of Energy’s http://www.millionsolarroofs.com/ “Million Solar Roofs” program. The system provides most of the electricity for the 6,000- square-foot home and family of eight.
1. Home Depot begins selling residential solar power systems in three of its stores in San Diego, California. A year later it expands sales to include 61 stores nationwide. 33
2. NASA’s solar-powered aircraft—Helios sets a new world record for non-rocketpowered aircraft: 96,863 feet, more than 18 miles high. 3. The National Space Development Agency of Japan, or NASDA, announces plans to develop a satellite-based solar power system that would beam energy back to Earth. A satellite carrying large solar panels would use a laser to transmit the power to an airship at an altitude of about 12 miles, which would then transmit the power to Earth. 4. TerraSun LLC develops a unique method of using holographic films to concentrate sunlight onto a solar cell. Concentrating solar cells typically use Fresnel lenses or mirrors to concentrate sunlight. TerraSun claims that the use of holographic optics allows more selective use of the sunlight, allowing light not needed for power production to pass through the transparent modules. This capability allows the modules to be integrated into buildings as skylights. 5. PowerLight Corporation places online in Hawaii the world’s largest hybrid system that combines the power from both wind and solar energy. The gridconnected system is unusual in that its solar energy capacity—175 kilowatts— is actually larger than its wind energy capacity of 50 kilowatts. Such hybrid power systems combine the strengths of both energy systems to maximize the available power. 6. British Petroleum (BP) and BP Solar announce the opening of a service station in Indianapolis that features a solar-electric canopy. The Indianapolis station is the first U.S. “BP Connect” store, a model that BP intends to use for all new or significantly revamped BP service stations. The canopy is built using translucent photovoltaic modules made of thin films of silicon deposited onto glass.
1. NASA successfully conducts two tests of a solar-powered, remote-controlled aircraft called Pathfinder Plus. In the first test in July, researchers demonstrated the aircraft’s use as a high-altitude platform for telecommunications technologies. Then, in September, a test demonstrated its use as an aerial imaging system for coffee growers. 2. Union Pacific Railroad installs 350 blue-signal rail yard lanterns, which incorporate energy saving light-emitting diode (LED) technology with solar cells, at its North Platt, Nebraska, rail yard—the largest rail yard in the United States. 3. ATS Automation Tooling Systems Inc. in Canada starts to commercialize an innovative method of producing solar cells, called Spheral Solar technology. The technology—based on tiny silicon beads bonded between two sheets of aluminum foil—promises lower costs due to its greatly reduced use of silicon relative to conventional multicrystalline silicon solar cells. The technology is not new. It was championed by Texas Instruments (TI) in the early 1990s. But despite U.S. Department of Energy (DOE) funding, TI dropped the initiative. 4. The largest solar power facility in the Northwest—the 38.7-kilowatt White Bluffs Solar Station—goes online in Richland, Washington.
Powerlight Corporation installs the largest rooftop solar power system in the United States—a 1.18 megawatt system—at the Santa Rita Jail in Dublin, California. 34
3.5 Recent developments in Solar technology (2001-2010)
Between 1970 and 1983 photovoltaic installations grew rapidly, but falling oil prices in the early 1980s moderated the growth of PV from 1984 to 1996. Since 1997, PV development has accelerated due to supply issues with oil and natural gas, global warming concerns, and the improving economic position of PV relative to other energy technologies. Photovoltaic production growth has averaged 40% per year since 2000 and installed capacity reached 10.6 GW at the end of 2007, and 14.73 GW in 2008. Since 2006 it has been economical for investors to install photovoltaics for free in return for a long term power purchase agreement. 50% of commercial systems were installed in this manner in 2007 and it is expected that 90% will by 2009. Nellis Air Force Base is receiving photoelectric power for about 2.2 ¢/kWh and grid power for 9 ¢/kWh. Commercial concentrating solar thermal power (CSP) plants were first developed in the 1980s. CSP plants such as SEGS project in the United States have a balanced energy cost (LEC) of 12–14 ¢/kWh. The 11 MW PS10 power tower in Spain, completed in late 2005, is Europe's first commercial CSP system, and a total capacity of 300 MW is expected to be installed in the same area by 2013. Solar installations in recent years have also largely begun to expand into residential areas, with governments offering incentive programs to make "green" energy a more economically viable option. In Canada the RESOP (Renewable Energy Standard Offer Program), introduced in 2006, and updated in 2009 with the passage of the Green Energy Act, allows residential homeowners in Ontario with solar panel installations to sell the energy they produce back to the grid (i.e., the government) at 42¢/kWh, while drawing power from the grid at an average rate of 6¢/kWh. The program is designed to help promote the government's green agenda and lower the strain often placed on the energy grid at peak hours. In March, 2009 the proposed FIT was increased to 80¢/kWh for small, roof-top systems (≤10 kW). As of November 2010, the largest photovoltaic (PV) power plants in the world are the Finsterwalde Solar Park (Germany, 80.7 MW), Sarnia Photovoltaic Power Plant (Canada, 80 MW),Olmedilla Photovoltaic Park (Spain, 60 MW), the Strasskirchen Solar Park (Germany, 54 MW), the Lieberose Photovoltaic Park (Germany, 53 MW), and the Puertollano Photovoltaic Park (Spain, 50 MW).
Figure-3.2: An eSolar project in California and Abengoa’s PS10 project in Seville, Spain.
3.6 Expected future direction of solar technology
All buildings will be built to combine energy-efficient design and construction practices and renewable energy technologies for a net-zero energy building. In effect, the building will conserve enough and produce its own energy supply to create a new generation of cost-effective buildings that have zero net annual need for non-renewable energy. Photovoltaic’s research and development will continue intense interest in new materials, cell designs, and novel approaches to solar material and product development. It is a future where the clothes you wear and your mode of transportation can produce power that is clean and safe. Technology roadmaps for the future outline the research and development path to full competitiveness of concentrating solar power (CSP) with conventional power generation technologies within a decade. The potential of solar power in the Southwest United States is comparable in scale to the hydropower resource of the Northwest. A desert area 10 miles by 15 miles could provide 20,000 megawatts of power, while the electricity needs of the entire United States could theoretically be met by a photovoltaic array within an area 100 miles on a side. Concentrating solar power, or solar thermal electricity, could harness the sun’s heat energy to provide large-scale, domestically secure, and environmentally friendly electricity. The price of photovoltaic power will be competitive with traditional sources of electricity within 10 years. Solar electricity will be used to electrolyze water, producing hydrogen for fuel cells for transportation and buildings.
4.1 What Is Solar Energy?
Solar energy is radiant energy that is produced by the sun. Every day the sun radiates, or sends out, an enormous amount of energy. The sun radiates more energy in one second than people have used since the beginning of time! Where does the energy come from that constantly radiates from the sun? It comes from within the sun itself. Like other stars, the sun is a big ball of gases—mostly hydrogen and helium atoms. The hydrogen atoms in the sun’s core combine to form helium and generate energy in a process called nuclear fusion. During nuclear fusion, the sun’s extremely high pressure and temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Four hydrogen nuclei fuse to become one helium atom. But the helium atom contains less mass than the four hydrogen atoms that fused. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy It takes millions of years for the energy in the sun’s core to make its way to the solar surface, and then just a little over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light. Only a small portion of the energy radiated by the sun into space strikes the earth, one part in two billion. Yet this amount of energy is enormous. Every day enough energy strikes the United States to supply the nation’s energy needs for one and a half years! Where does all this energy go? About 15 percent of the sun’s energy that hits the earth is reflected back into space. Another 30 percent is used to evaporate water, which, lifted into the atmosphere, produces rainfall. Solar energy also is absorbed by plants, the land, and the oceans. The rest could be used to supply our energy needs.
4.2 The Sun is Our Source
Our sun produces 400,000,000,000,000,000,000,000,000 watts of energy every second and the belief is that it will last for another 5 billion years. The United States reached peak oil production in 1970, and there is no telling when global oil production will peak, but it is accepted that when it is gone the party is over. The sun, however, is the most reliable and abundant source of energy. Most of the energy we use has undergone various transformations before it is finally utilized, but it is also possible to tap this source of solar energy as it arrives on the earth’s surface. There are many applications for the direct use of solar thermal energy, space heating and cooling, water heating, crop drying and solar cooking. It is a technology, which is well understood and widely used in many countries throughout the world. Most Solar thermal technologies have been in existence in one form or another for centuries and have a well established manufacturing base in most sun-rich developed countries. The most common use for solar thermal technology is for domestic water heating. Hundreds of thousands of domestic hot water systems are in use throughout the world, especially in areas such as the Mediterranean and Australia where there is high solar insulation (the total energy per unit area received from the sun). As world oil prices vary, it is a technology, which is rapidly gaining acceptance as an energy saving measure in both domestic and commercial water heating applications. Presently, domestic water heaters are usually only found amongst wealthier sections of the community in developing countries. Other technologies exist which take advantage of the free energy provided by the sun. Water heating technologies are usually referred to as active solar technologies, whereas other technologies, such as space heating or cooling, which passively absorb the energy of the sun and have no moving components, are referred to as passive solar technologies. More sophisticated solar technologies exist for providing power for electricity generation. We will look at these briefly later in this fact sheet.
Figure-4.1: Direct and diffuse solar radiations 38
Sun is the source of many forms of energy available to us. The most abundant element in sun is hydrogen. It is in a plasma state. This hydrogen at high temperature, high pressure and high density undergoes nuclear fusion and hence releases an enormous amount of energy. This energy is emitted as radiations of different forms in the electromagnetic spectrum. Out of these X-rays, gamma rays and most of ultraviolet rays do not pass through the earth’s atmosphere. But heat energy and light energy are the main radiations that reach the earth. This energy is the basis for the existence of life on earth. Sun is a sphere of intensely hot gaseous matter with a diameter of 1.39e9 m and 1.5e11 m away from earth. Sun has an effective black body temperature of 5762 K and has a temperature of 8e6 K to 40e6 K. The sun is a continuous fusion reactor in which hydrogen (4 protons) combines to form helium (one He nucleus). The mass of the He nucleus is less than that of the four protons, mass having been lost in the reaction and converted to energy. The energy received from the sun on a unit area perpendicular to the direction of propagation of radiation outside atmosphere is called solar constant, and has a value 1353 Wm– 2. This radiation when received on the earth has a typical value of 1100 Wm– 2 and is variable. The wavelength range is 0.29 to 2.5 micro meters. This energy is typically converted into usual energy form through natural and man-made processes. Natural processes include wind and biomass. Man-made processes include conversion into heat and electricity.
4.3 Solar Energy Basics
At its core, solar energy is actually nuclear energy. In the inner 25% of the Sun, hydrogen is fusing into helium at a rate of about 7 x 10 kg of hydrogen every second. If this sounds like a lot, it is because it is: this is equivalent to the amount of mass that can be carried by 10 million railroad cars. There is no need to fear, though, that we are going to run out of fuel anytime soon, as the Sun has enough hydrogen in the core to continue at this rate for another 5 billion years. This energy production, coupled with gravitational compression, keeps the Sun’s center near a sweltering 16 million K, which is about 29 million F. Heat from the core is first primarily radiated, and then primarily convected, to the Sun’s surface, where it maintains at a temperature of 5800 K
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From the surface of the Sun, the primary method of energy transport is electromagnetic radiation. This form of heat transport depends greatly upon the surface temperature of an object for the amount and type of energy. Stefan-Boltzmann’s Law tells us that the amount of energy that is radiated per unit area of surface depends upon the temperature of the object to the fourth power, i.e. energy/area is proportional to T . This means that the amount of energy that is emitted by the Sun, and therefore, the amount of solar energy that we receive here on Earth, is critically dependent upon this surface temperature. A change of 1% in the temperature of the Sun (58 K) can result in a change of 4% in the amount of energy per unit area that we receive here. While this might not sound like a lot, it is more than enough to plunge us into brutal ice age or hellish global warming.
The type of radiation coming from the Sun also depends on temperature. The Sun is emitting electromagnetic radiation in wide variety of wavelengths. However, most of the radiation is being sent out in the visible spectrum due to its surface temperature. Wien’s Law states that the wavelength at which the most energy will be radiated depends inversely upon the temperature of an object. Thus, as an object gets hotter, the peak radiation will come from shorter wavelengths, and vice-versa. Figure 2 shows a theoretical plot of the energy emitted by three perfect blackbody radiators of different temperature. An object that has a temperature of 4000 K has its peak energy being radiated at about 750 nanometers, which is in the near infrared. An object that has a surface temperature of 6000 K, though, has its peak energy being radiated at about 500 nanometers, which is in the green region of the visible spectrum. How these objects will appear to the human eye is determined by just how much energy is in each of the visible wavelengths. The first object will appear a very dim red, while the second (which is close to our Sun’s temperature of 5800 K) will appear a bright white that has a hint of yellow.
Figure-4.2: Brightness vs. wavelength for various temperatures
While our Sun is not a perfect blackbody radiator, its output is fairly close to that described above. It radiates 1.6 x 10 watts of power per square meter from its surface at all wavelengths. However, by the time that it has reached the Earth’s surface, this value is vastly reduced. Between the Sun’s and the Earth’s surfaces, the energy density of the radiation is lessened by spreading and absorption. Light travelling from a spherical object such as the Sun must spread to fill all available space. While the total amount of energy of the radiation will remain the same, the amount of energy crossing any square meter of space will be reduced by the square of the distance between the object and the area in question. Since the Sun is almost 150 million kilometers from the Earth, the energy density per unit time of the sunlight reaching the upper atmosphere of the Earth is only 1340 W/m . 40
Travelling through the almost perfect vacuum of space, there is almost nothing to absorb or reflect any of this energy. Most of the absorption of the Sun’s light occurs after it enters the Earth’s atmosphere. The vast majority of the visible part of the spectrum gets through the atmosphere with little attenuation. What little doesn’t get through is due to scattering by nitrogen and oxygen (blue appearance of the sky is due to this) and by absorption and reflection from clouds. Large portions of the non-visible part of the spectrum do not get through the atmosphere, though. Chemical species such as ozone, water vapor, and carbon dioxide all absorb wavelengths of light in the infrared and ultraviolet portion of the spectrum. Figure 3 shows a plot of the percentage of the Sun’s energy that gets transmitted through the atmosphere versus wavelength on a cloudless day. As you can see, outside of the visible and radio parts of the spectrum, there are only a few small sections in the infrared through which the energy gets transmitted. On average, only about 50% of the Sun’s energy that makes it to the top of the atmosphere actually gets down to the surface.
Figure-4.3: Sunlight transmitted through the atmosphere versus wavelength
4.3.1 Latitude and Longitude
These are not the only factors that affect the total amount of energy that a solar system receives. One factor that seriously impacts it is the number of hours of sunlight a location receives in a day. If sunlight is striking a spot for more time during a day, then more total energy will be delivered, and vice versa. The amount of time that sunlight is shining during the day depends both on the location and the time of year. This is due to the fact that the Earth is a sphere that is spinning with its axis at an angle of 23.5 with respect to the vertical to the plane of its orbit around the Sun. This means that the path that the Sun will take in the sky on a given day changes. Figure 4 shows a diagram of a typical situation found in Pakistan. As you can see, the length of the path that the Sun follows on these four different days varies, as does the noonday angle of the Sun. These different lengths correspond to different travel times, which means different amounts of daylight.
Figure-4.4: Diagram of the Sun’s path in the sky on different days In Pakistan, there are about 8-10 hours of sunlight on the Winter Solstice (Dec. 22 ) and 14-16 hours of sunlight on the Summer Solstice (Jun. 21 ), depending upon at what degree of latitude you live. Sites that are further north have shorter days in the winter and longer days in the summer. If one were to live at the equator, the length of the path across the sky would not vary, which results in 12 hours of daylight everyday. At the Poles, the situation is even stranger. There, the Sun is up for 6 months at a time, followed by 6 months of darkness. The noonday angle of the Sun in the sky can also have an effect on a solar energy system unless it has a way to track the Sun. A system that can do this can always keep its collecting surface perpendicular to the Sun’s rays, thereby allowing the most energy to strike it. If it cannot do this, then sunlight will always strike the system’s collecting surface at some angle, thereby spreading the energy over a greater area and reducing the amount that actually strikes the surface. As we see from Figure-4.4, the angle of the Sun’s rays changes throughout the year, as well as throughout the day. As previously stated, these angles will depend upon the location of the system on the Earth’s surface.
4.4 Solar Thermal vs. Photovoltaic
It is important to understand that solar thermal technology is not the same as solar panel, or photovoltaic, technology. Solar thermal electric energy generation concentrates the light from the sun to create heat, and that heat is used to run a heat engine, which turns a generator to make electricity. The working fluid that is heated by the concentrated sunlight can be a liquid or a gas. Different working fluids include water, oil, salts, air, nitrogen, helium, etc. Different engine types include steam engines, gas turbines, Stirling engines, etc. 42
All of these engines can be quite efficient, often between 30% and 40%, and are capable of producing 10’s to 100’s of megawatts of power. Photovoltaic, or PV energy conversion, on the other hand, directly converts the sun’s light into electricity. This means that solar panels are only effective during daylight hours because storing electricity is not a particularly efficient process. Heat storage is a far easier and efficient method, which is what makes solar thermal so attractive for large-scale energy production. Heat can be stored during the day and then converted into electricity at night. Solar thermal plants that have storage capacities can drastically improve both the economics and the dispatchability of solar electricity.
Figure-4.5: Parabolic dish that collects and concentrates the sun into a heat source to run the engine and produce power.
4.5 Competing with Fossil Fuels
Solar thermal power currently leads the way as the most cost-effective solar technology on a large scale. It currently beats other PV systems, and it also can beat the cost of electricity from fossil fuels such as natural gas. In terms of low-cost and high negative environmental impact, nothing competes with coal. But major solar thermal industry players such as eSolar, Brightsource, or Abengoa, have already beaten the price of photovoltaic and natural gas, and they have plans to beat the price of coal in the near future. With an increasingly industrializing planet, the leaders in solar thermal technology have an ever-growing market. The issue is, and will always be, how to make solar thermal technology more economical. There are currently two methods for solar thermal collection. The first is line focus collection. The second is point focus collection. Line focus is less expensive, technically less difficult, but not as efficient as point focus. The basis for this technology is a parabola-shaped mirror, which rotates on a single axis throughout the day tracking the sun. Point focus technique requires a series of mirrors surrounding a central tower, also known as a power tower. The mirrors 43
focus the sun’s rays onto a point on the tower, which then transfers the heat into more usable energy. Point focus, though initially costlier and technically more nuanced, outshines line focus when results are concerned. The point of focus in a line focus mirror array can only reach temperatures around 250° C. That is a sufficient temperature to run a steam turbine, but when compared to the 500° C and higher temperatures that point focus can reach, the extra effort and cost is balanced out by its greater efficiency capability. High efficiency matters because it drives down both the land usage, and the effective cost per kWhr of the plant.
Figure-4.6: Coal Reservoir
4.6 Solar Thermal Power plant
In the solar power plant, solar energy is used to generate electricity. Sunrays are focused using concave reflectors on to copper tubes filled with water and painted black outside. The water in the tubes then boils and become steam. This steam is used to drive steam turbine, which in turn causes the generator to work. Many power plants today use fossil fuels as a heat source to boil water. The steam from the boiling water rotates a large turbine, which activates a generator that produces electricity. However, a new generation of power plants, with concentrating solar power systems, uses the sun as a heat source. There are three main types of concentrating solar power systems: parabolic-trough, dish/engine, and power tower.
Parabolic-trough systems: Concentrate the sun’s energy through long rectangular, curved (Ushaped) mirrors. The mirrors are tilted toward the sun, focusing sunlight on a pipe that runs down the center of the trough. This heats the oil flowing through the pipe. The hot oil then is used to boil water in a conventional steam generator to produce electricity.
A dish/engine system: uses a mirrored dish (similar to a very large satellite dish). The dish
shaped surface collects and concentrates the sun's heat onto a receiver, which absorbs the heat and transfers it to fluid within the engine. The heat causes the fluid to expand against a piston or turbine to produce mechanical power. The mechanical power is then used to run a generator or alternator to produce electricity.
A power tower system: uses a large field of mirrors to concentrate sunlight onto the top of a
tower, where a receiver sits. This heats molten salt flowing through the receiver. Then, the salt’s heat is used to generate electricity through a conventional steam generator. Molten salt retains heat efficiently, so it can be stored for days before being converted into electricity. That means electricity can be produced on cloudy days or even several hours after sunset.
4.6.1 ‘Solar Power Tower’ Power Plant
The first is the 'Solar Power Tower' design which uses thousands of sun-tracking reflectors or heliostats to direct and concentrate solar radiation onto a boiler located atop a tower. The temperature in the boiler rises to 500 – 7000°C and the steam raised can be used to drive a turbine, which in turn drives an electricity producing turbine. There are also called central Receiver Solar Power Plants. It can be divided into solar plant and conventional steam power plant. The flow diagram is given in Figure-4.7.
Figure-4.7: A central receiver solar power plant A heliostat field consists of a large number of flat mirrors of 25 to 150 m2 area which reflects the beam radiations onto a central receiver mounted on a tower. Each mirror is tracked on two axis. The absorber surface temperature may be 400 to 1000°C. The concentration ratio (total mirror area divided by receiver area) may be 1500. Steam, air or liquid metal may be used as working fluid. Steam is raised for the conventional steam power plant.
4.6.2 ‘Distributed (Parabolic) Collector System’ Power Plant
The second type is the distributed collector system. It is also called solar farm power plant as a number of solar modules consisting of parabolic trough solar collectors are interconnected. This system uses a series of specially designed ‘Trough’ collectors which have an absorber tube running along their length. Large arrays of the collectors are coupled to provide high temperature water for driving a steam turbine. Such power stations can produce many megawatts (mW) of electricity, but are confined to areas where there is ample solar insulation. Every module consists of a collector as shown in Figs. 4.8 and 4.9. It is rotated about one axis by a sun tracking mechanism. Thermo-oil is mostly used as heating fluid as it has very high boiling point.
Figure-4.8: Parabolic Solar collector
Figure-4.9: Parabolic trough solar power plant
Water/steam working fluid can also be used. The tubes have evacuated glass enclosure to reduce the losses. The concentration ratio is between 40 and 100. The maximum oil temperature is limited to400°C as oil degrades above this temperature. Alternately steam at 550°C can be directly generated in the absorber tube. These are commercially under operation. Fig. 4.9. shows a flow diagram of parabolic trough solar power plant. The working fluid is heated in collectors and collected in hot storage tank (2). The hot thermo-oil is used in boiler (5) to raise steam for the steam power plant. The boiler also is providedwith a back-up unit (6) fired with natural gas. The cooled oil is stored in tank (3) and pumped (4) backto collector (1). Solar thermal power plants with a generating capacity of 80 MW are functioning in the USA.
4.6.3 Solar Chimney Power Plant
The air stream is heated by solar radiation absorbed by the ground and covered by a transparent cover. The hot air flow through or chimney which gives the air a certain velocity due to pressure drop caused by the chimney effect. The hot air flows through an air turbine to generate power.
Figure-4.10: Chimney solar power plant
4.7 Solar Energy Storage
It is well known that human beings have been using solar energy for different uses, from ancient days. Find examples of these uses and add to the list given below. 1. To get salt from sea water. 2. To dry wet clothes. 3. To dry firewood. 4. To dry cereals. 5. To dry fish. 6. To dry leather. We now use several appliances which work using solar energy. Appliances like solar cooker and solar heater absorb solar radiations and convert it into heat. Then what about a solar cell? Solar energy is converted into electrical energy and it is directly used or stored in a battery. There are eight possible pathways for conversion of solar radiation to useful energy. Solar thermal conversion method converts radiation to heat using solar flat collectors. Solar thermo chemical conversion method converts radiation to heat and produce steam then to kinetic energy using a pump or turbine. Solar thermal electric conversion method converts radiation to steam and to kinetic and electrical energy through a turbine and generator to electrical energy. The above route through a further electrolysis process gives chemical energy (H2 fuel). A high temperature catalytic conversion process produces chemical energy (H2 fuel) directly. Photovoltaic conversion of solar radiation gives direct electrical energy. Photosynthesis process produces chemical energy directly from radiation. Chemical energy (H2 fuel) is directly produced from solar radiation using the electricity produced by the photovoltaic method. A few of these methods are dealt in detail further. Commercial and industrial buildings may use the same solar technologies photovoltaic, passive heating, day lighting, and water heating that are used for residential buildings. These nonresidential buildings can also use solar energy technologies that would be impractical for a home. These technologies include ventilation air preheating, solar process heating and solar cooling. Many large buildings need ventilated air to maintain indoor air quality. In cold climates, heating this air can use large amounts of energy. A solar ventilation system can preheat the air, 47
saving both energy and money. This type of system typically uses a transpired collector, which consists of a thin, black metal panel mounted on a south-facing wall to absorb the sun’s heat. Air passes through the many small holes in the panel. A space behind the perforated wall allows the air streams from the holes to mix together. The heated air is then sucked out from the top of the space into the ventilation system. Solar process heating systems are designed to provide large quantities of hot water or space heating for nonresidential buildings. A typical system includes solar collectors that work along with a pump, a heat exchanger, and/or one or more large storage tanks. The two main types of solar collectors used an evacuated tube collector and a parabolic trough collector can operate at high temperatures with high efficiency. An evacuated-tube collector is a shallow box full of many glass, double-walled tubes and reflectors to heat the fluid inside the tubes. A vacuum between the two walls insulates the inner tube, holding in the heat. Parabolic troughs are long, rectangular, curved (U-shaped) mirrors tilted to focus sunlight on a tube, which runs down the center of the trough. This heats the fluid within the tube. The heat from a solar collector can also be used to cool a building. It may seem impossible to use heat to cool a building, but it makes more sense if you just think of the solar heat as an energy source. Your familiar home air conditioner uses an energy source, electricity, to create cool air. Solar absorption coolers use a similar approach, combined with some very complex chemistry tricks, to create cool air from solar energy. Solar energy can also be used with evaporative coolers (also called “swamp coolers”) to extend their usefulness to more humid climates, using another chemistry trick called desiccant cooling.
4.8 Space Heating
In colder areas of the world (including high altitude areas within the tropics) space heating is often required during the winter months. Vast quantities of energy can be used to achieve this. If buildings are carefully designed to take full advantage of the solar insulation which they receive then much of the heating requirement can be met by solar gain alone. By incorporating certain simple design principles a new dwelling can be made to be fuel efficient and comfortable for habitation. The bulk of these technologies are architecture based and passive in nature. The use of building materials with a high thermal mass (which stores heat), good insulation and large glazed areas can increase a buildings capacity to capture and store heat from the sun. Many technologies exist to assist with diurnal heating needs but seasonal storage is more difficult and costly. For passive solar design to be effective certain guidelines should be followed: 1. A building should have large areas of glazing facing the sun to maximize solar gain. 2. Features should be included to regulate heat intake to prevent the building from overheating. 3. A building should be of sufficient mass to allow heat storage for the required period. 4. Contain features which promote the even distribution of heat throughout the building. One example of a simple passive space heating technology is the Trombe wall. A massive black painted wall has a double glazed skin to prevent captured heat from escaping. The wall is vented to allow the warm air to enter the room at high level and cool air to enter the cavity between the wall and the glazing. Heat stored during the wall during the day is radiated into the 48
room during the night. This type of technology is useful in areas where the nights are cold but the days are warm and sunny.
4.9 Space Cooling
The majority of the worlds developing countries, however, lie within the tropics and have little need of space heating. There is a demand, however, for space cooling. The majority of the worlds warm-climate cultures have again developed traditional, simple, elegant techniques for cooling their dwellings, often using effects promoted by passive solar phenomenon. There are many methods for minimizing heat gain. These include sitting a building in shade or near water, using vegetation or landscaping to direct wind into the building, good town planning to optimise the prevailing wind and available shade. Buildings can be designed for a given climate domed roofs and thermally massive structures in hot arid climates, shuttered and shaded windows to prevent heat gain, open structure bamboo housing in warm, humid areas. In some countries dwellings are constructed underground and take advantage of the relatively low and stable temperature of the surrounding ground. There are as many options as there are people.
4.10 Land Requirements
Another challenge for solar thermal is the amount of space required for efficient production of energy. Not only space, but space that gets a consistent amount of direct sunlight. Solar thermal power plants typically require 1/4 to 1 square mile or more of land. One silver lining of global climate change and human impact on the land is that more and more farmland is becoming unsuitable for agricultural production. This land, presumably originally chosen for its sun exposure, begs to be used for solar thermal energy production. Utilization of desertification can prove to be a boon for solar thermal real estate procurement and growth. With solar thermal technologies being developed and advanced by companies such as eSolar, Brightsource, Abengoa, Acciona, Ausra and Schott Solar, the world has a new alternative. The benefits of eliminating coal from our energy diet are many. By not burning fossil fuels, countries can be truly energy independent. Also, by limiting, and hopefully eliminating, carbon emissions, a nation’s pollution will not be windswept into another nation’s territories, further cementing the concept of independence. Solar thermal plants are being built around the world, and many new planned plants are in the works. Solar thermal is the current solar electricity cost champion, but more improvements are needed to beat the cost of the lowest-cost fossil fuels in a legislative climate without subsidies or carbon taxes.
Figure-4.11: eSolar’s unique approach to minimize land requirements 49
Solar Energy and Pakistan
Figure-5.1: Solar energy and Pakistan
5.1 The solar energy future
5.1.1 Methodology and assumptions
If PV is to have a promising future as a major energy source it must build on the experiences of those countries that have already led the way in stimulating the solar energy market. In this section we look forward to what solar power could achieve - given the right market conditions and an anticipated fall in costs - over the first two decades of the twenty-first century. As well as projections for installed capacity and energy output we also make assessments of the 50
level of investment required, the number of jobs that would be created and the crucial effect that an increased input from solar electricity will have on greenhouse gas emissions. This scenario for 2025, together with an extended projection forwards to 2040, is based on the following core inputs. 1. PV market development over recent years both globally and in specific regions. 2. National and regional market support programmers. 3. National targets for PV installations and manufacturing capacity. 4. The potential for PV in terms of solar irradiation, the availability of suitable roof space and the demand for electricity in areas not connected to the grid.
5.1.2 Power generation
The global installed capacity of solar power systems would reach 433 GWp by 2025. About two thirds of this would be in the grid-connected market, mainly in industrialized countries. Assuming that 80% of these systems are installed on residential buildings, and their average size is 3 kWp, each serving the needs of three people, the total number of people by then generating their own electricity from a grid-connected solar system would reach 290 million. In Europe alone there would be roughly 41 million people receiving their supply from grid-connected solar electricity. In the non-industrialized world approximately 40 GWp of solar capacity is expected to have been installed by 2020 in the rural electrification sector. Here the assumption is that on average a 100 Wp stand-alone system will cover the basic electricity needs of 3-4 persons per dwelling. Since system sizes are much smaller and the population density greater, this means that up to 950 million people in the developing countries would by then be using solar electricity. By 2025, more than 1.6 billion people could get electricity from off grid photovoltaic systems. This would represent a major breakthrough for the technology from its present emerging status
More jobs are created in the installation and servicing of PV systems than in their manufacture. Based on information provided by the industry, it has been assumed that, up to 2010, 20 jobs will be created per MW of capacity during manufacture, decreasing to 10 jobs per MW between 2010 and 2020. About 30 jobs per MW will be created during the process of installation, retailing and providing other local services up to 2010, reducing to 27 jobs per MW between 2010 and 2020. As far as maintenance is concerned it is assumed that with the more efficient business structures and larger systems in the industrialized world, about one job will be created per installed MW. Since developing world markets will play a more significant role beyond 2010, however, the proportion of maintenance work is assumed to steadily increase up to two jobs per MW by 2020. The result is that by 2025, an estimated 3.2 million full-time jobs would have been created by the development of solar power around the world. Over half of those would be in the installation and marketing of systems.
5.2 Solar Energy and Pakistan: An Over View
As solar power does not make sense for all locations in the world. The initial cost of installing solar panels or other sources of solar energy is high, and that is not easy for most people to get around. No matter how much some people would like to get involved in the movement to independent energy, it is cost prohibitive. To achieve the highest level of efficiency, which is the entire point of going solar in the first place, we need the proper amount of roof space to support the panels your house may require. Not only how much space is available, but also the location of your home is also relevant to whether or not you can maintain solar energy. Some houses simply do not receive enough sunlight to produce substantial energy. This could mean that either your house is not positioned favorably in relation to a tree or other house.
5.3 Pakistan is most suitable for solar power
As we can see, the cons of implementing solar power in our home are primarily cost and location related, but if those two items do not pose issues for us, the good news is that, If solarpower is looked at through a long-term lens, we will eventually make back what you originally spent, and possibly start saving money on your investment.
Let’s not forget that solar energy increases the value of our home too. Solar power is not subject supply and demand fluctuations in the way that gas is. Silicon, the primary component of solar panels, is also being more widely produced, therefore, less and less expensive with each passing year. Solar power is independent, or semi-independent. This is great because you can supply your home with electricity during a power outage. Solar power can also be used in remote locations, places where conventional power can’t be reached. On a larger scale, solar power also reduces our need to rely on foreign sources for power. And last, but certainly not least, it’s good for our planet! Solar energy is clean, renewable and sustainable. It does not fill our atmosphere with carbon dioxide, nitrogen oxide, mercury or any other pollutants. It is a free and unlimited source of power, unlike expensive and damaging fossil fuels.
5.4 Pakistan’s indulgence in solar energy
ISLAMABAD, April 29-2010 - President Asif Ali Zardari has asked for an early adoption and utilization of modern solar and geothermal technologies including solar cookers, geothermal heat pumps, solar water heaters and solar water pumping etc. to take full advantage of the available natural energy resources, on one hand and to meet the energy requirements of the country, on the other. “The energy crisis has forced upon a vigorous search for out of box, imaginative and bold solutions,” the President said during a briefing given to him on alternate Pakistan on industrial grid linked electricity production program, the Government of Pakistan has determined to establish 100 MW Solar Power Farm by June 2011. This program initiated by the Alternative Energy Development Board (AEDB), involves financing through private sector, land from Government of Sindh and power purchase by NTDC for HESCO. The Government of Pakistan guarantees are backed through NEPRA. The Board has recently issued LOIs to 30 national and international companies for generation of 1500 MW power through solar energy.
5.5 Solar activity in Pakistan
(2x50) MW Solar Power Generation Project at Gharo, Sindh: A solar corridor at Gharo-Keti Bandar, Sindh has been identified with an actual potential of 50,000 MW. The pre-feasibility study of the site has been done by AEDB. AEDB drafted the Power Purchase Agreement (PPA) and the Implementation Agreement. 8 companies with financial and technical viability have been short-listed. OEMs/Suppliers like GE, VESTAS and GAMESA have been short-listed for the project. Three companies have submitted applications to NEPRA for obtaining Generation License. NTDC has submitted the request for Power Acquisition Permission to NEPRA for procuring power from the proposed solar plants. HESCO has agreed to purchase the initial 100 MW Solar Power generated through this project. Private investors have entered the PPA negotiations with NTDC/WAPDA. Sindh Government has leased out approximately 5000 Acres of land for the project. AEDB has allocated 1000 acres of land each to five (5) investors, namely M/s New Park Energy Ltd., M/s Green Power, M/s Zephyr Ltd., M/s Win Power Ltd. and M/s Tenaga. Tariff would be determined by NEPRA in consultation with the IPP and the Power Purchaser i.e. NTDC, as per Government of Pakistan’s Policy for Power Generation 2002. Once the initial target of generating 100 MW through Solar Energy is achieved, it will be upgraded to 700 MW by the year 2010 and 9700 MW by the year 2030. 100 Solar Homes Program Narian Khorian, Islamabad The project was successfully executed and implemented by AEDB. The Honorable Prime Minister of Pakistan inaugurated it on 19th June 2005. Each of the 100 households has been provided with 88-Watt Solar Panels, 4 LED lights, a 12 Volt DC fan and a TV socket. In addition, a Solar Geyser and a Solar Cooker have also been provided to each household. As part of the community welfare, a Solar Water Desalination Plant has also been installed and commissioned at the village ensuring the availability of clean drinking water to the villagers. A Children’s Playground with Solar Powered Lights has also been developed at the Village. Two Solar Powered Computers have been provided to the village Mosque/Community Center, which has been air-conditioned using Solar Energy as well. In addition, an electric vehicle has also been developed which will act as the first ever Electric Rickshaw in Pakistan. The batteries of this vehicle are charged with Solar Energy. 100 Solar Homes Program per Province: The project was executed and implemented in the following villages: 1. 2. 3. 4. Allah Baksh Bazar Dandar, District Kech, Balochistan, Bharo Mal, District Thar, Sindh, Janak, District Kohat, Khyber Pakhtunkhwa., Lakhi Bher, Distrcit D.G. Khan, Punjab. 54
Each of the 100 households in each village has been provided with 88-Watt Solar Panels, 4 LED lights, a 12 Volt DC fan and a TV socket. In addition, a Solar Disinfecting Unit and a Solar Cooker have also been provided to each household. Pilot Project for Development and Installation of 02 Micro Hydro Kaplan Pannel: A 40 kW Kaplan type micro hydel Turbine has been imported from China to reverse engineer the technology. An R&D lab is being setup for this purpose. Another 40 kW Kaplan type micro hydel turbine has been indigenously manufactured and installed at the Khanpur Dam Canal near the village of Mohra Morado, Taxila. This turbine is being used to provide electricity to the village Pilot Project for Installation of Indigenously Developed Micro Solar Panel: A total of 140 Micro Solar Pannel have been installed at various sites within Sindh and Balochistan, for providing electricity to the rural households, Innovative Lighting Systems: LED Lights, Solar Lanterns, Pedal Generators, Hand Generators and Solar Mobile Phone Chargers have been indigenously developed by the private sector with AEDB’s facilitation. These products have also been provided to the rural areas that have been electrified with Solar Energy.
5.6 Activities of Pakistan Council for Renewable Energy Technologies (PCRET)
Photovoltaic (PV) Technology 1. Solar-Solar-Diesel High hybrid system installed to provide electricity to two villages in Balochistan through M/s Empower International, New Zealand. 2. Two other villages in Balochistan were electrified using PV system. 3. 3000 Laser Detectors were designed and fabricated for incorporating in the laser land leveling system of Pakistan Atomic Energy Commission (PAEC). 4. 4000 Solar Cells and 300 Solar Modules of different sizes were fabricated indigenously. Solar Thermal Appliances A number of appliances including solar water heaters, solar fruit and vegetable dryers, solar distillation stills for producing clean water, solar room heating systems and solar cookers have been developed and disseminated for domestic and commercial applications. Electrification through Micro Solar Panel: 1. 600 houses have been electrified in the remote coastal areas of Sindh and Balochistan through installation of small solar panel (stand alone) systems. 55
2. 4 Coast Guard Check Posts at Lasbela have been electrified. 3. 5 villages have been provided with battery charging facilities through a solar-powered battery-charging center. 4. 500-Watts Solar Turbine has been manufactured locally. The second (improved) model is under field test. 5. A reverse osmosis unit is being installed near village Mubarak, Kemari Town, Karachi for desalination of brackish water.
5.7 Pakistan’s Solar Energy Development Plans
MEDIUM TERM SOLAR ENERGY DEVELOPMENT PLAN 2011-2020
Year Capacity Installed (MW) 700 Cumulative MW of Solar Energy Installed by Year End Short Term Plan (2005-2010) 700
Source: Board of Investment, Government of Pakistan
DETAILS OF MICRO SOLAR PANNEL INSTALLED IN SINDH & BALOCHISTAN SINDH - District Thatta
S.No Name of Village Homes Electrified Khaskheli – 16 04 Pannel Installed
Goth Gul Muhammad Thakani, Mirpur Sakro
Goth Haji Jumo Khaskheli – Thakani, Mirpur Sakro Goth Ismail Khaskheli 1 – Thakani Goth Ismail Khaskheli 2 – Thakani Goth Mohd Hasan Khaskheli – Thakani, Mirpur Sakro Goth Haji Abdullah Channo – Thakani, Mirpur Sakro Goth Jamot Hussain Khaskheli – Thakani, Mirpur Sakro Goth Baboo Pahwar – Thakani, Mirpur Sakro Goth Sher Muhammad Hamaiti – Gujjo Goth Daandaari – Ghorabari, U.C. Udaasi Goth Lukman – Ghorabari, U.C. Udaasi Goth Sammo – Ghorabari, U.C. Udaasi Total
3 4 5
15 05 18
04 01 05
9 10 11 12
40 250 16 14 356
10 40 04 03 85
Daandaari – Ghorabari, U.C. Udaasi
01 (10 kilo Watts) – Water Pumping
Source: Board of Investment, Government of Pakistan
BALOCHISTAN - Kund Malir, District Lasbela
S.No Name of Village Homes Electrified 03 15 35 Pannel Installed 01 02 05
1 2 3
Goth Meer Isa – Kund Malir, Lasbela Goth Ramzan – Kund Malir, Lasbela Goth Haji Sher Muhammad – Kund Malir, Lasbela Goth Yaaqoob – Kund Malir, Lasbela Goth Mir Abdullah – Kund Malir, Lasbela Goth Haji Washi / Daghari – Kund Malir, Lasbela Totals
Source: Board of Investment, Government of Pakistan BALOCHISTAN - Quetta
N S.No 7 Name of Recipient Governor Balochistan on behalf of the Government of Balochistan Location F.C. Warehouse Quetta Panel 39 Current Status To be installed as per the direction and advice of the Irrigation & Power Department Balochistan
Source: Board of Investment, Government of Pakistan VILLAGES ELECTRIFIED THROUGH SOLAR PHTOVOLTAIC DURING 2004-05 Village Name Narian Khorian Allah Baksh Bazar Dandar Lakhi Bhair Bharomal Jhanak District Rawalpindi Rawalpindi Turbat D.G. Khan Chachro Kohat Province No. of Houses 53 57 121 135 115 120 601
Punjab Punjab Balochistan Punjab Sindh K.P.K Total Source: Board of Investment, Government of Pakistan
VILLAGES TO BE ELECTRIFIED THROUGH SOLAR PHTOVOLTAIC DURING 2005-06 Village name Khirzaan Basti Bugha Pinpario Shnow Garri District Khuzdar D.G. Khan Chachro Kohat Province Balochistan Punjab Sindh K.P.K Total No. of Houses 100 100 100 100 400
RENEWABLE ENERGY PROJECTS FOR 2005-06
No. 1. Project Title Roshan Pakistan: National Rural Electrification Programe through Alternative / Renewable Energy Technologies Solar Homes Project in Each Province Development of Supply Chain Mechanism for Pedal Generators, Hand Generators and LED Lanterns Pilot Project of Production Plant of Bio-Diesel Research on Development of 1 kW Fuel Cell Electric Vehicle in Pakistan using Existing Fuel Cell Solar Water Pumping & Desalination Solar Thermal Power Plant Technologies (Demonstration Units) Electrification of Villages through Micro Solar Pannel Pilot project for Development and Installation of 02 Micro Hydro Kaplan Pannel Pilot project for Emerging Demonstration in Pakistan Alternative Energy Technologies
6. 7. 8. 9.
Reports are a helpful channel, but it is people’s behavior that really changes things. We encourage politicians and policymakers, global citizens, energy officials, companies, investors and other interested parties to support solar power. Solar energy is very useful, particularly in a time when we are concerned about greenhouse gas emissions from other energy sources. By taking the crucial steps to help ensure that more than a billion people obtain electricity from the sun in the future we can harness the full potential of solar power for our common good.