Technical Report

Chapter 1 INTRODUCTION Historical Background A Brief History of Solar Energy Ancient Greeks and Romans saw great benefit in what we now refer to as passive solar design—the use of architecture to make use of the sun’s capacity to light and heat indoor spaces. The Greek philosopher Socrates wrote, “In houses that look toward the south, the sun penetrates the portico in winter.” Romans advanced the art by covering south facing building openings with glass or mica to hold in the heat of the winter sun. Through calculated use of the sun’s energy, Greeks and Romans offset the need to burn wood that was often in short supply. Auguste Mouchout, inventor of the first active solar motor, questioned the widespread belief that the fossil fuels powering the Industrial Revolution in the 19th century would never run out. “Eventually industry will no longer find in Europe the resources to satisfy its prodigious expansion. Coal will undoubtedly be used up. What will industry do then?” Mouchout asked prophetically.

2 In 1861, Mouchout developed a steam engine powered entirely by the sun. But its high costs coupled with the falling price of English coal doomed his invention to become a footnote in energy history. Nevertheless, solar energy continued to intrigue and attract European scientists through the 19th century. Scientists developed large cone-shaped collectors that could boil ammonia to perform work like locomotion and refrigeration. France and England briefly hoped that solar energy could power their growing operations in the sunny colonies of Africa and East Asia. In the United States, Swedish-born John Ericsson led efforts to harness solar power. He designed the “parabolic trough collector,” a technology which functions more than a hundred years later on the same basic design. Ericsson is best known for having conceived the USS Monitor, the armored ship integral to the U.S. Civil War. Solar power could boast few major gains through the first half of the 20th century, though interest in a solar-powered civilization never completely disappeared. In fact, Albert Einstein was awarded the 1921 Nobel Prize in physics for his research on the photoelectric effect—a phenomenon central to the generation of electricity through solar cells. Some 50 years prior, William Grylls Adams had discovered that when light was shined upon selenium, the material shed electrons, thereby creating electricity.

3 In 1953, Bell Laboratories (now AT&T labs) scientists Gerald Pearson, Daryl Chapin and Calvin Fuller developed the first silicon solar cell capable of generating a measurable electric current. The New York Times reported the discovery as “the beginning of a new era, leading eventually to the realization of harnessing the almost limitless energy of the sun for the uses of civilization.” In 1956, solar photovoltaic (PV) cells were far from economically practical. Electricity from solar cells ran about $300 per watt. (For comparison, current market rates for a watt of solar PV hover around $5.) The “Space Race” of the 1950s and 60s gave modest opportunity for progress in solar, as satellites and crafts used solar paneling for electricity. It was not until October 17, 1973 that solar leapt to prominence in energy research. The Arab Oil Embargo demonstrated the degree to which the Western economy depended upon a cheap and reliable flow of oil. As oil prices nearly doubled over night, leaders became desperate to find a means of reducing this dependence. In addition to increasing automobile fuel economy standards and diversifying energy sources, the U.S. government invested heavily in the solar electric cell that Bell Laboratories had produced with such promise in 1953. The hope in the 1970s was that through massive investment in subsidies and research, solar photovoltaic costs could drop precipitously and eventually become competitive with fossil fuels.

4 By the 1990s, the reality was that costs of solar energy had dropped as predicted, but costs of fossil fuels had also dropped—solar was competing with a falling baseline. However, huge PV market growth in Japan and Germany from the 1990s to the present has reenergized the solar industry. In 2002 Japan installed 25,000 solar rooftops. Such large PV orders are creating economies of scale, thus steadily lowering costs. The PV market is currently growing at a blistering 30 percent per year, with the promise of continually decreasing costs. Meanwhile, solar thermal water heating is an increasingly cost-effective means of lowering gas and electricity demand. As you’ve seen, technologies have changed and improved for decades. Still, the basics of solar thermal and photovoltaics have remained the same. The model for the fusion power plant, the sun, is a source of practically unlimited energy, most of which is wasted but nevertheless provides us with millions of kilowatts of power, keeps us warm, and grows all our food. To top it off, solar energy is safe, pollution-free energy on and in which living things have thrived since they first appeared on earth. Every day the sun showers Earth with several thousand times as much energy as we use. Even the small amount that strikes our roof is many times as much as all the energy that comes in through electric wires. With the sun straight overhead, a single acre of land receives some four thousand

5 horsepower, about equivalent to a large railroad locomotive. In less than three days the solar energy reaching Earth more than matches the estimated total of all the fossil fuels on Earth! The logical question at this point is, Why are we not making use of this incredible bonanza in the form of solar energy? The answer, of course, is that we are using it, and have been from the beginning. All our energy-except nuclear- comes originally from the sun. A solar-powered radio draws on the sun directly, but a gasoline fueled automobile also uses solar energy-stored solar energy, in which the sunshine of ages ago was trapped in the earth until reclaimed by oil drillers. The challenge is to make use of solar energy directly and in a non-polluting fashion. The Russian philosopher, Kuzma Prutkov, decided that the moon is more useful than the sun, since it shines at night when light is needed; while the sun is of little use in the daytime since it is light anyway! In such a fashion we, too, have dismissed the importance and potential of the sun. It appears that the fruitful application of solar energy is destined to wait until the bottom of the energy stockpile the sun has willed us is depleted. Now is the time to make realistic goals and strategies to harness the power of the sun. The harnessing of solar energy is not new in fact, development of solar energy dates back more than 100 years, to the middle of the industrial

6 revolution. Several pioneering solar power plants were constructed to produce steam from the heat of the sun, which was used to drive the machinery of the time. At the same time, Henri Becquerel discovered the photovoltaic effect; that is, the production of electricity directly from the sun. Becquerel's research was investigated and extended by, among others, Werner Siemens. Photovoltaic power remained a curiosity for many years, since it was very inefficient at turning sunlight into electricity. Early photovoltaic applications were geared more towards sensing and measuring light (such as a camera's light meter) than towards producing power. With the advent of the transistor and accompanying semiconductor technology, however, the efficiency of photovoltaic power increased dramatically. Photovoltaic power became more practical. Over the years, many companies, including Siemens Solar, have worked to increase the efficiency of photovoltaic power. Today, commonly available solar panels are 12% efficient, which is four times greater than only a few years ago. Today, solar power is still used in two primary forms: thermal solar, where the heat of the sun is used to heat water or another working fluid, which drives turbines or other machinery to create electricity; and photovoltaic, where electricity is produced directly from the sun with no moving parts. Siemens Solar manufactures photovoltaic panels which produce electricity directly from the sun.

7 The History of Solar Energy in the Industrial Age The next major advancements occurred in the 17th century, and were of a more technical nature. This is where solar energy technology really came into existence. The book, Alternative Energy Resources: The Quest for Sustainable Energy , covers the history of solar energy from the Industrial Age into the present day. This book also discusses the various available sources of renewable energy sources available, such as hydroelectric energy, wind energy, biomass, and geothermal energy. It also discusses other forms of alternative energy nuclear energy, and the use of hydrogen. This book evaluates the advantages and disadvantages of each source of energy. The author takes into account our energy requirements, environmental impact, and the availability of different forms of alternative energy, and he proposes his own suggestion as to what he thinks would be the most viable and feasible energy source for us in the modern day.

8 Statement of the Problem This study deals with the solar power as an alternative source of electricity. More specifically, it tries to answer the following questions: 1. What is solar power? 2. How important is solar power in our environment, industry and science and technology? 3. What are the multiple components on Photovoltaic (solar cells) system? 4. What are the advantages and disadvantages of solar power? 5. How are photovoltaic or solar cells used? Objective of the Problem This technical report is written with the following objectives. 1. To know the benefits of using solar power as an alternative source of electricity. 2. To update people that solar power is one of the best sources of electricity. 3. To know the more about the components of Photovoltaic (solar cell) System. 4. To internalize the procedures to be followed in using solar or photovoltaic cells. 5. To put into application the use of solar cells to produce electricity for practical use.

9 Importance of the Problem We are indeed fortunate to live in a world of modern technology which has provided us the convenience of electricity at the flip of the switch. Most of our modern gadgets run on electricity and sudden power outages frustrate us no end. We take all this for granted and therefore cannot imagine a world without electricity or fuel for our vehicles. Neither do we stop to think that conventional energy which is obtained from natural resources like fossil fuels will not last forever. In the present scenario of global warming and ozone layer depletion, the world needs to make a lifestyle change to protect the environment for the future generations. We have to seriously look towards alternative energy and alternative fuels to take care of our needs. Nature has provided us with an unlimited source of energy in the form of solar power. This is a natural resource, freely available and will be replenished as long as the Sun shines. Solar power is the energy obtained from the heat and rays of the sun. Solar power has many uses. It can be used to generate electricity using photovoltaic solar cells and concentrated solar power. It can be used to heat buildings directly by passive solar building designs, or cooking and heating food with the help of solar ovens. Solar Chimneys can be used to heat

and

cool

air.

Alternative energy is the future trend and most of the technologies pertaining to alternative energy depend directly or indirectly on the sun. Solar energy drives the atmosphere and virtually supports all life on Earth. Heat and light from the sun along with hydropower, geothermal power and wind energy

10 account for most of the flow of renewable energy. Solar Power refers to the process of conversion of sunlight into electricity. The electricity can then be used to power up our homes, businesses and industries to continue the cycle of life. Agriculture

depends

on

solar

energy.

Plants

use

sunlight

for

photosynthesis and thus produce food. Heating, ventilation and air conditioning systems are closely related and use solar power as their source of energy. Solar water heaters were the earliest use of solar power and continue to be used even today. Solar cookers used for cooking and drying foodstuffs offset fuel costs, reduce demand for firewood and improve air quality due to reduction of smoke. Domestic use of solar power is the best way to conserve our natural resources.

There are many technologies which are being used to harness solar energy. Applications span through the residential, commercial, industrial, agricultural and transportation sectors. Solar energy can be used to produce food, heat, light and electricity. The flexibility of solar energy is manifest in a wide variety of technologies from cars and calculators to huge photovoltaic plants. Recent price hikes and erratic availability of conventional fuels are factors that are renewing interest in solar heating technologies. Thus solar power is important to the very existence of the world as a whole.

11 Definition of Terms > Solar Power

- the result of converting sunlight into electricity.

>Photovoltaic system - the field of technology and research related to the application

of solar cells for energy by converting solar energy (sunlight,

including ultra violet radiation) directly into electricity. >Solar

Cells

-

a

device

that

converts light directly

into electricity by

the photovoltaic effect. >Photovoltaic Effect - involves the creation of a voltage (or a corresponding electric current) in a material upon exposure to electro-magnetic radiation. >Photovoltaic Cell - is a type of Photoelectric cell that uses the photovoltaic effect to generate electrical energy using the potential difference that arises between materials when the surface of the cell is exposed to electromagnetic radiation. >Photovoltaic Array - is a linked collection of photovoltaic modules, which are in turn made of multiple interconnected solar cells. >Energy - is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law. >Ultraviolet (UV) Light - is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV.

12 >Grid-tied Electrical System - is a semi-autonomous electrical generation or grid energy storage system which links to the mains to feed excess capacity back to the local mains electrical grid. >Building-integrated Photovoltaic - are photovoltaic materials that are used to replace conventional building materials in parts of the building envelope such as the roof, skylights, or facades. >Photodiode - is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation. >Photovoltaic Module - is a packaged interconnected assembly of photovoltaic cells, also known as solar cells.

13 Chapter 2 SOLAR POWER Solar power is the result of converting sunlight into electricity. Sunlight can be converted directly into electricity using photovoltaics (PV), or indirectly with concentrating solar power (CSP), which normally focuses the sun's energy to boil water which is then used to provide power. The largest solar power plants, like the 354 MW SEGS, are concentrating solar thermal plants, but recently multi-megawatt photovoltaic plants have been built. Completed in 2008, the 46 MW Moura photovoltaic power station in Portugal and the 40 MW Waldpolenz Solar Park in Germany are characteristic of the trend toward larger photovoltaic power stations. Much larger ones are proposed, such as the 550 MW Topaz Solar Farm, and the 600 MW Rancho Cielo Solar Farm. Some technologies, such as solar thermal concentrators have an element of thermal storage, such as molten salts. These store spare solar energy in the form of heat which is made available overnight or during periods that solar power is not available to produce electricity. Applications Solar power is the conversion of sunlight into electricity. Sunlight can be converted directly into electricity using photovoltaics (PV), or indirectly with concentrating solar power (CSP), which normally focuses the sun's energy to boil water which is then used to provide power, and technologies such as the

14 Stirling engine dishes which use a Stirling cycle engine to power a generator. Photovoltaics

were

initially

used

to

power

small

and

medium-sized

applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array. Solar power plants can face high installation costs, although this has been decreasing due to the learning curve. Developing countries have started to build solar power plants, replacing other sources of energy generation. Since solar radiation is intermittent, solar power generation is usually combined either with storage or other energy sources to provide continuous power, although for small distributed producer/consumers, net metering makes this transparent to the consumer. On a slightly larger scale, in Germany, a combined power plant has been demonstrated, using a mix of wind, biomass, hydro-, and solar power generation, resulting in 100% renewable energy. Concentrating solar power A legend claims that Archimedes used polished shields to concentrate sunlight on the invading Roman fleet and repel them from Syracuse.[7] Auguste Mouchout used a parabolic trough to produce steam for the first solar steam engine in 1866. Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power

15 plant. A wide range of concentrating technologies exists; the most developed are the parabolic trough, the concentrating linear fresnel reflector, the Stirling dish and the solar power tower. Various techniques are used to track the Sun and focus light. In all of these systems a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage. A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line. The receiver is a tube positioned right above the middle of the parabolic mirror and is filled with a working fluid. The reflector is made to follow the Sun during the daylight hours by tracking along a single axis. Parabolic trough systems provide the best land-use factor of any solar technology.[10] The SEGS plants in California and Acciona's Nevada Solar One near Boulder City, Nevada are representatives of this technology.[11][12] The Suntrof-Mulk parabolic trough, developed by Melvin Prueitt, uses a technique inspired by Archimedes' principle to rotate the mirrors. Concentrating linear fresnel reflectors are CSP-plants which use many thin mirror strips instead of parabolic mirrors to concentrate sunlight onto two tubes with working fluid. This has the advantage that flat mirrors can be used which are much cheaper than parabolic mirrors, and that more reflectors can be placed in the same amount of space, allowing more of the available sunlight

16 to be used. Concentrating linear fresnel reflectors can be used in either large or more compact plants. A stirling solar dish, or dish engine system, consists of a stand-alone parabolic reflector that concentrates light onto a receiver positioned at the reflector's focal point. The reflector tracks the Sun along two axes. Parabolic dish systems give the highest efficiency among CSP technologies. The 50 kW Big Dish in Canberra, Australia is an example of this technology. The stirling solar dish combines a parabolic concentrating dish with a stirling heat engine which normally drives an electric generator. The advantages of stirling solar over photovoltaic cells are higher efficiency of converting sunlight into electricity and longer lifetime. A solar power tower uses an array of tracking reflectors (heliostats) to concentrate light on a central receiver atop a tower. Power towers are more cost effective, offer higher efficiency and better energy storage capability among CSP technologies. The Solar Two in Barstow, California and the Planta Solar 10 in Sanlucar la Mayor, Spain are representatives of this technology. A solar bowl is a spherical dish mirror that is fixed in place. The reciever follows the line focus created by the dish (as opposed to a point focus with tracking parabolic mirrors). The design was first build in Crosbyton Texas and more recently in Auroville, India. It is one of the simplest and easiest to maintin design with low initial cost.

17

Uses of Solar Power These days, it's pretty practical, especially for remote homes. Until solar power came along, people who wanted to live in remote areas frequently had to pay large fees to have a power cable run to their house. Now, a remote home can be virtually self-sufficient with solar power. Even in areas where power lines are nearby, solar may be a viable alternative to being connected to a power company. An average home has more than enough roof area to produce enough solar electricrity to supply all of its power needs. With an inverter, which converts direct current (DC) power from the solar cells to alternating current (AC), which is what most home appliances run on, a solar home can look and operate very much like a home that is connected to a power line. For recreational vehicles, solar power provides the freedom to go to more remote locations, without relying on a plug-in power source or a noisy electric generator. Systems for RVs can be small for charging batteries only or large enough to power the entire vehicle for a period of time. Similarly, boats can use solar power for many of their power needs, rather than a generator or engine.

18

Illustration I

Illustration II

19

CHAPTER 3 PHOTOVOLTAIC (SOLAR CELL) SYSTEM A photovoltaic system is a system which uses solar cells to convert light into electricity. A photovoltaic system consists of multiple components, including cells, mechanical and electrical connections and mountings and means of regulating and/or modifying the electrical output. Due to the low voltage of an individual solar cell (typically ca. 0.5V), several cells are combined into photovoltaic modules, which are in turn connected together into an array. The electricity generated can be either stored, used directly (island/standalone plant)or fed into a large electricity grid powered by central generation plants (grid-connected/grid-tied plant) or combined with one or many domestic electricity generators to feed into a small grid (hybrid plant)

[1]

. Depending on the type of application, the rest of the

system ("balance of system" or "BOS") consists of different components. The BOS depends on the load profile and the system type. Systems are generally designed in order to ensure the highest energy yield for a given investment. Standalone systems A standalone system does not have a connection to the electricity mains. Standalone systems vary in size from watches or calculators to remote buildings

20 or spacecraft. If the load is to be supplied independently of insolation, the generated power needs to be buffered with a battery. Where weight is not an issue (e.g. buildings) lead acid batteries are used. A charge controller may be incorporated in the system to a) avoid battery damage by excessive charging or discharging and b) optimizing the production of the cells or modules by maximum power point tracking(MPPT). In small devices (e.g. calculators, parking meters) only DC is consumed. In larger systems (e.g. buildings, remote water pumps) AC is usually required. To convert the DC from the modules or batteries into AC, an inverter is used. Hybrid system A hybrid system combines PV with other forms of generation, usually a diesel generator. Biogas is also used. The other form of generation may be a type able to modulate power output as a function of demand. However more than one renewable form of energy may be used e.g. wind. The photovoltaic power generation serves to reduce the consumption of non renewable fuel. Hybrid systems are most often found on islands. Pellworm island in Germany and Kynthos island are notable examples (both are combined with wind)

[2] [3]

.

The Kynthos plant has reduced diesel consumption by 11.2% Grid-connected/Grid-tied System A grid connected system is connected to a large independent grid (typically the public electricity grid) and feeds power into the grid. Grid

21 connected systems vary in size from residential (2-10kWp) to solar power stations (up to 10s of GWp). This is a form of decentralized electricity generation. In the case of residential or building mounted grid connected PV systems, the electricity demand of the building is met by the PV system. Only the excess is fed into the grid when there is an excess. The feeding of electricity into the grid requires the transformation of DC into AC by a special, grid-controlled inverter. In kW sized installations the DC side system voltage is as high as permitted (typically 1000V except US residential 600V) to limit ohmic losses. Most modules (72 crystalline silicon cells) generate about 160W at 36 volts. It is sometimes necessary or desirable to connect the modules partially in parallel rather than all in series. One set of modules connected in series is known as a 'string'. Grid connected inverters On the AC side, these inverters must supply electricity in sinusoidal form, synchronized to the grid frequency, limit feed in voltage to no higher than the grid voltage including disconnecting from the grid if the grid voltage is turned off. On the DC side, the power output of a module varies as a function of the voltage in a way that power generation can be optimized by varying the system

22 voltage to find the 'maximum power point'. Most inverters therefore incorporate 'maximum power point tracking'. The inverters are designed to connect to one or more strings. For safety reasons a circuit breaker is provided both on the AC and DC side to enable maintenance. The AC output usually goes through across an electricity meter into the public grid. The meter must be able to run in both directions. In some countries, for installations over 30kWp a frequency and a voltage monitor with disconnection of all phases is required. Connection to a DC grid DC grids are only to be found in electric powered transport: railways trams and trolleybuses. A few pilot plants for such applications have been built, such as the tram depots in Hannover Leinhausen

and Geneva (Bachet de

Pesay).

DC

The

150kWp

Geneva

site

feeds

600V

directly

into

the

tram/trolleybus electricity network provided about 15% of the electricity at its opening in 1999.

23 Small-scale PV solar systems Small scale DIY solar systems With

a

growing

DIY-community

and

an

increasing

interest

in

environmentally friendly "green energy", some hobbyists have endeavored to build their own PV solar systems from kits

or partly diy. Usually, the DIY-

community uses inexpensive and/or high efficiency systems (such as those with solar tracking) to generate their own power. As a result, the DIY-systems often end up cheaper than their commercial counterparts. Often, the system is also hooked up unto the regular power grid to repay part of the investment via net metering. These systems usually generate power amount of ~2kW or less. Through the internet, the community is now able to obtain plans to construct the system (at least partly DIY) and there is a growing trend toward building them for domestic requirements. The DIY-PV solar systems are now also being used both in developed countries and in developing countries, to power residences and small businesses. Mounting systems Modules are assembled into arrays on some kind of mounting system. For solar parks a large rack is mounted on the ground, and the modules mounted on the rack. For buildings, many different racks have been devised for pitched roofs. For flat roofs, racks, bins and building integrated solutions are used.

24 Trackers A solar tracker can substantially improve the amount of power produced by a system by enhancing morning and afternoon performance. It is only worth installing trackers for non-concentrating applications in regions with mostly direct sunlight. In diffuse light (ie under cloud or fog), tracking has no value. For concentrated photovoltaic systems a tracker is necessary. System performance At high noon on a cloudless day at the equator, the power of the sun is about 1 kW/m², on the Earth's surface, to a plane that is perpendicular to the sun's rays. As such, PV arrays can track the sun through each day to greatly enhance energy collection. However, tracking devices add cost, and require maintenance, so it is more common for PV arrays to have fixed mounts that tilt the array and face due South in the Northern Hemisphere (in the Southern Hemisphere, they should point due North). The tilt angle, from horizontal, can be varied for season, but if fixed, should be set to give optimal array output during the peak electrical demand portion of a typical year. For large systems, the energy gained by using tracking systems outweighs the added complexity (trackers can increase efficiency by 30% or more). PV arrays that approach or exceed one megawatt often use solar trackers. Accounting for clouds, and the fact that most of the world is not on the equator, and that the sun sets in the evening, the correct measure of solar

25 power is insolation – the average number of kilowatt-hours per square meter per day. For the weather and latitudes of the United States and Europe, typical insolation ranges from 4 kWh/m²/day in northern climes to 6.5 kWh/m²/day in the sunniest regions. Typical solar panels have an average efficiency of 12%, with the best commercially available panels at 20%. Thus, a photovoltaic installation in the southern latitudes of Europe or the United States may expect to produce 1 kWh/m²/day. A typical "150 watt" solar panel is about a square meter in size. Such a panel may be expected to produce 1 kWh every day, on average, after taking into account the weather and the latitude. In the Sahara desert, with less cloud cover and a better solar angle, one could ideally obtain closer to 8.3 kWh/m²/day provided the nearly ever present wind would not blow sand on the units. The unpopulated area of the Sahara desert is over 9 million km², which if covered with solar panels would provide 630 terawatts total power. The Earth's current energy consumption rate is around 13.5 TW at any given moment (including oil, gas, coal, nuclear, and hydroelectric). Photovoltaic cells' electrical output is extremely sensitive to shading. When even a small portion of a cell, module, or array is shaded, while the remainder is in sunlight, the output falls dramatically due to internal 'shortcircuiting' (the electrons reversing course through the shaded portion of the p-n junction). Therefore it is extremely important that a PV installation is not

26 shaded at all by trees, architectural features, flag poles, or other obstructions. Sunlight can be absorbed by dust, fallout, or other impurities at the surface of the module. This can cut down the amount of light that actually strikes the cells by as much as half. Maintaining a clean module surface will increase output performance over the life of the module. Module output and life are also degraded by increased temperature. Allowing ambient air to flow over, and if possible behind, PV modules reduces this problem. However, effective module lives are typically 25 years or more [13]

, so replacement costs should be considered as well.

Standardization Increasing use of photovoltaic systems and integration of photovoltaic power into existing structures and techniques of supply and distribution increases the value of general standards and definitions for photovoltaic components and systems. The standards are compiled at the International Electrotechnical Commission (IEC)and apply to efficiency, durability and safety of cells, modules, simulation programs, plug connectors and cables, mounting systems, overall efficiency of inverters etc.

27 CHAPTER 4 USE OF SOLAR CELLS A solar cell or photovoltaic cell is a device that converts light directly into electricity by the photovoltaic effect. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the light source is unspecified. Assemblies of cells are used to make solar panels, solar modules, or photovoltaic arrays. Photovoltaics is the field of technology and research related to the application of solar cells in producing electricity for practical use. The energy generated this way is an example of solar energy. Solar Power System - How to Use it for Your Own Benefit You must have noticed the sparkling, color-filled rooftops that many buildings have these days, haven't you? These rooftops seem to dazzle with colors of various shades as soon as the sunlight falls on them. However, these are not at all mere fancy items that only enhance the beauty of a home. In fact, they are solar panels, which serve a very important purpose, viz., the generation of electricity, which can be used by the householders for domestic purposes. Over 10,000 residences in the United States of America are found to possess domestic solar power systems, according to a survey that was held recently. Solar photovoltaic cells are found to be present in more than 200,000 blocks of houses (in the major American cities). These solar cells generate

28 power in the AC form. Also, far from being only a local phenomenon of the United States, the growing popularity of solar power is, in fact a global trend. All over the world, a greater number of users are switching over to solar power systems with time. Know the intricacies of a solar power system A typical solar power system has certain specified components. Firstly, an inverter needs to be present, which would be able to generate usable 120 volt AC electric power, when DC current is passed through it. The DC current, in turn, is produced by harnessing the solar energy that is captured by the photovoltaic panels. Wires are required to keep the parts of the system together, and different poles and clamps are used to set up the solar power system on the top of roofs and/or in areas which receive abundant sunlight for the majority of the day. In addition, the system might also be provided with a battery backup too. For practical purposes, a certain number of photovoltaic (PV) cells are clustered together to form a module. Several such modules can then be combined to get a solar panel. Let us now try to understand what the necessity of using these systems is, and who actually uses them. Two basic reasons become immediately apparent, due to which solar power systems are becoming popular in both grid areas as well as non-grid localities (where utility power remains inaccessible for people).

29 Normally, power is generated by the systems only during the day time, as long as sunlight remains available. This is because, these systems stop working at night. This factor worked against the solar power units, and prevented them from becoming popular earlier. As a result, solar power could not be used much at that time. However, the situation has completely undergone a change owing to the tremendous technological advances that have taken place. Now, extra amounts of electricity, produced during the day, can be stored and later on, retrieved and used during the night. The storage of electric power is also useful on days that remain cloud-covered. Indeed, technological progresses have made the modern solar power system extremely useful. There are several other factors that are also worth a mention. For example, those who have grid-tied solar power systems can supply electricity to the grid. The extra electric power can be sold off in exchange of money of course. For this, the solar power system only has to be kept connected with the grid. In fact, there are many people who are using the solar power systems in precisely this way - generating the electricity that they require to meet their needs, and selling off the surplus to earn some extra cash in the bargain. The headquarters of Google, at California, is one of many busy cosmopolitan urban regions where this type of setup can be commonly seen. Getting into the details, it is indeed a fact that, when the power grids are situated at a certain distance (generally, around a couple of miles) from

30 the residential locations, economic benefits from the solar power systems is the maximum. This is in view of the observation that, a significant amount of money needs to be spent for installing the poles, and then for extending the power cords through the poles right to the home. Having the solar power system at the residential structure itself offers a much more cost-effective option. The raw material used here is just sunlight, which is freely available. Hence, after installation, the question of paying hefty electricity bills every month does not arise, if solar power systems are used. The government and other local bodies are also trying to encourage more and more citizens to start using solar power. And so that this can happen, they offer many incentive schemes, rebates and attractive discounts. Once you install a home solar energy system, you shall be able to generate electricity in a totally environment-preserving manner, and will also be able to cut down on your power bills. Surplus amounts of power generated can be easily saved, stored or sold off in exchange of money as well. You should ideally be following a training manual that has detailed discussions on how to install the system, the place where you should do so for the best outputs, how to complete the wiring and also the safety measures that you should be following.

31 CHAPTER 5 UNDERSTANDING THE ADVANTAGES AND DISADVANTAGES OF SOLAR POWER Solar power is a renewable source of electricity, which is available in any part of the world. Learning the advantages and disadvantages of solar power can help you in making an informed decision on whether to switch to solar or stay

with

utility-purchased

electricity.

Since the physics behind solar power can be confusing to many people, understanding the advantages and disadvantages of solar power can provide you with a clearer perception on how a system works to keep utility bills low, preserve

natural

Financial

And

energy

and

Environmental

save

the

Benefits

earth Of

from Solar

pollution. Power

When you choose to buy a solar power system, the initial investment can be a large amount of money. However, since many companies and government departments offer incentives and rebates by spreading the costs of your solar power system, then you save money in the long run because energy production from

the

sun

is

practically

without

costs.

Since solar energy does not require any fuel, you will not be affected by the demands and possible rate increases of gasoline. As a result, you can immediately save money for both utility-based and fuel-based costs. Although many people weigh the advantages and disadvantages of solar power before opting to buy a system, some consumers instantly find the eco-friendly benefits of solar power to be beneficial. Because solar energy is clean,

32 sustainable and renewable, you are helping to preserve the environment by preventing air pollution from nitrogen oxide, carbon dioxide, mercury or sulphur dioxide - the common elements found in traditional energy resources. Advantages Infinite energy source There is a never-ending supply of solar energy because it is produced by the sun all the time. Every day, all year the sun is producing energy. While fossil fuels like natural gas and oil will eventually run out, solar energy will continue to be available until the sun disappears and at that point we'll have a lot bigger problems to be worried about than how to power our air conditioners. As fossil fuels become more and more scarce, the cost will continue to increase. The opposite is true of solar electricity! It will never run out and the cost will continue to go down as technology gets better and better. Free energy Power from the sun will continue to be free as long as the sun is shining. Aside from battery replacement, if batteries are used in the solar power system, there is virtually no ongoing cost for solar power. If you install enough solar panels, you can disconnect from the power company and never pay an electric bill again. This is called living off grid. If you can generate more energy than you need, you can stay connected to the grid and actually sell the extra electricity to the power company!

33 No greenhouse gasses For people who are concerned about global warming, solar energy is the answer! Fossil fuels like oil and natural gas produce a lot of greenhouse gasses, but solar power produces none at all. If you wish to lower your carbon footprint, solar electricity is a great way to do it. There are no emissions of any kind produced by solar power. Lower dependence on foreign oil Dependence on foreign oil is widely considered one of the biggest security threats today. Using solar power will reduce dependence on foreign oil. Any power that is currently produced with foreign oil can be directly replaced by domestically produced solar electricity. Disadvantages Initial cost Most people consider initial cost to be the biggest disadvantages to solar electricity. The initial cost of solar panels can be quite high, while the ongoing costs of solar electricity are very small. With the required know-how, the initial cost can be reduced a great deal by building solar panels yourself.

34 Required space Solar panels must be oriented so they point to the south and also need enough space for all the panels. Solar panels work best in areas that get a lot of sun. There are solar maps available that show the average sun in different areas. A larger score means that a solar panel of the same size will produce more electricity than a solar panel in an area with a smaller score. You will need more solar panels to generate sufficient electricity to power your house if you live in an area with a lower score. As you can see, there are advantages and disadvantages to solar electricity.

The

advantages

of

solar

power,

however,

outweigh

the

disadvantages and you can avoid most of the disadvantages by building your own solar panels.

35 Chapter 7 CONCLUSION AND RECOMMENDATIONS Conclusion Based on the result of the researcher’s investigation, the following conclusions are given: 1. Solar power is one of the best ways to generate electricity in a totally environment-preserving manner and cuts down our daily power bills. 2. Photovoltaic (solar cells) system has multiple components on how to harness energy from the sun. 3. Solar / Photovoltaic cells are devised used to convert light directly into electricity by the photovoltaic effect. 4. Solar power is an eco-friendly source of energy because it does not produce any greenhouse gasses. Recommendations In the light of the conclusion mentioned, the following recommendations are offered: 1. One should have a sound knowledge on solar power system to use it for his own benefit. 2. One must learn about the different components on Photovoltaic (solar cells) system.

36 3. One should encourage the use of solar power as an alternative source of electricity for it is environment-friendly. 4. One must learn more about solar cells and how they are used. 5. Science teachers must inform their students about the existence of solar power and its importance.

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