1. ELECTRICITY GENERATION

2. Electricity generation is the process of creating electricity from other forms of energy. The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of a loop of wire, or disc of copper between the poles of a magnet. For electric utilities, it is the first process in the delivery of electricity to consumers. The other processes, electric power transmission, electricity distribution, and electrical power storage and recovery using pumped storage methods are normally carried out by the electrical power industry. Electricity is most often generated at a power station by electromechanical generators, primarily driven by heat engines fueled by chemical combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind. There are many other technologies that can be and are used to generate electricity such as solar photovoltaics and geothermal power.

3. 2)Relative cost of electricity by generation source 3)ENVIRONMENTAL CONCERNS 1)HISTORY INDEX 4)METHODS OF GENERATING ELECTRICITY

4. Centralised power generation became possible when it was recognized that alternating current power lines can transport electricity at very low costs across great distances by taking advantage of the ability to raise and lower the voltage using power transformers. Electricity has been generated at central stations since 1881. The first power plants were run on water power or coal, and today we rely mainly on coal, nuclear, natural gas, hydroelectric, and petroleum with a small amount from solar energy, tidal harnesses, wind generators, and geothermal sources HISTORY

5. Relative cost of electricity by generation source when attempting to state the costs of electric power, then to have any real meaning, the competing sources costs need to be compared on a similar basis of calculation (discount rate, lifetime etc) with the same assumptions applied to each source - typically this means looking at a number of single studies that each covers all the various sources - wind, nuclear, fossil etc and treats them all on the same bases.[ citation needed ] Simply quoting the price of one source can be very misleading, as can quoting the cost of say wind from one study, and comparing it with the cost of say nuclear from another study, since these may be based on different assumptions. It also needs to be made clear if the calculation is simply of the raw cost at the generator terminals, or have allowances been made for say intermittency, unreliability, variability, all of which factors apply to all sources to a greater or lesser degree.

6. ENVIRONMENTAL CONCERNS Most scientists agree that emissions of pollutants and greenhouse gases from electricity generation account for a significant portion of world greenhouse gas emissions; in the United States, electricity generation accounts for nearly 40 percent of emissions, the largest of any source. Transportation emissions are close behind, contributing about one-third of U.S. production of carbon dioxide.

7. METHODS OF GENERATING ELECTRICITY 1)HYDROELECTRICITY 2)SOLAR POWER 3)GEOTHERMAL POWER

8. HYDROELECTRICITY

9. Hydroelectricity is electricity generated by hydropower, i.e., the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO2) than fossil fuel powered energy plants. Worldwide, an installed capacity of 777 GWe supplied 2998 TWh of hydroelectricity in 2006. This was approximately 20% of the world's electricity, and accounted for about 88% of electricity from renewable sources.

10. ELECTRICITY GENERATION Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. In this case the energy extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This heig ht difference is called the head. The amount of potential energy in water is proportional to the head. To obtain very high head, water for a hydraulic turbine may be run through a large pipe called a penstock.

11. INDUSTRIAL HYDROELECTRIC PLANTS While many hydroelectric projects supply public electricity networks, some are created to serve specific industrial enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium electrolytic plants, for example. In the Scottish Highlands of United Kingdom, there are examples at Kinlochleven and Lochaber, constructed during the early years of the 20th century. The Grand Coulee Dam, long the world's largest, switched to support Alcoa aluminum in Bellingham, Washington, United States for American World War II airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminum power) after the war. In Suriname, the Brokopondo Reservoir was constructed to provide electricity for the Alcoa aluminium industry. New Zealand's Manapouri Power Station was constructed to supply electricity to the aluminium smelter at Tiwai Point.

12. SMALL-SCALE HYDRO-ELECTRIC PLANTS Small hydro schemes are particularly popular in China, which has over 50% of world small hydro capacity. Small hydro units in the range 1 MW to about 30 MW are often available from multiple manufacturers using standardized "water to wire" packages; a single contractor can provide all the major mechanical and electrical equipment (turbine, generator, controls, switchgear), selecting from several standard designs to fit the site conditions. Micro hydro projects use a diverse range of equipment; in the smaller sizes industrial centrifugal pumps can be used as turbines, with comparatively low purchase cost compared to purpose-built turbines.

13. COUNTRIES WITH MOST HYDRO-ELECTRIC POWER The top six dams, in descending order of their annual electricity generation, are: the Three Gorges Dam in China, the Itaipu Dam on the border of Paraguay and Brazil, the Guri Dam in Venezuela, the Tucurui dam in Brazil, the Sayano-Shushenskaya Dam in Russia and the Krasnoyarsk hydroelectric dam , also in Russia. Brazil, Canada, Norway, Switzerland and Venezuela are the only countries in the world where the majority of the internal electric energy production is from hydroelectric power, while Paraguay not only produces 100% its electricity from hydroelectric dams, but exports 90% of its production to Brazil and to the Argentine. Norway produces 98–99% of its electricity from hydroelectric sources.

14. SOLAR POWER

15. Solar power is the genera tion of electricity from sunlight. This can be direct as with photovoltaics (PV), or indirect as with concentrating solar power (CSP), where the sun's energy is focused to boil water which is then used to provide power. The solar power gained from photovoltaics can be used to eliminate the need for purchased electricity (usually electricity gained from burning fossil fuels) or, if energy gained from photovoltaics exceeds the home's requirements, the extra electricity can be sold back to the home's supplier of energy, typically for credit. 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 100 MW Fort Peck Solar Farm, the 550 MW Topaz Solar Farm, and the 600 MW Rancho Cielo Solar Farm. Solar power is a predictably intermittent energy source, meaning that whilst solar power is not available at all times, we can predict with a very good degree of accuracy when it will and will not be available. 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.

16. APPLICATIONS Solar power is the conversion of sunlight to 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 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 .

17. CONCENTRATING SOLAR POWER A legend claims that Archimedes used polished shields to concentrate sunlight on the invading Roman fleet and repel them from Syracuse. 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 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.

18. PHOTOVOLTAICS A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photoelectric effect. This is based on the discovery by Alexandre-Edmond Becquerel who noticed that some materials release electrons when hit with rays of photons from light, which produces an electrical current. The first solar cell was constructed by Charles Fritts in the 1880s. Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discovery. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.

19. ENERGY STORAGE METHODS Solar energy is not available at night, making energy storage an important issue in order to provide the continuous availability of energy. Both wind power and solar power are intermittent energy sources, meaning that all available output must be taken when it is available and either stored for when it can be used , or transported, over transmission lines, to where it can be used. Wind power and solar power can be complementary , in locations that experience more wind in the winter and more sun in the summer, b ut on days with no sun and no wind the difference nee ds to be made up in some manner.

20. GEOTHERMAL POWER

21. Geothermal power (from the Greek roots geo , meaning earth, and thermos , meaning heat) is power extracted from heat stored in the earth. This geothermal energy originates from the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface. It has been used for bathing since Paleolithic times and for space heating since ancient Roman times, but is now better known for generating electricity. Worldwide, geothermal plants have the capacity to generate about 10 gigawatts of electricity as of 2007, and in practice supply 0.3% of global electricity demand. An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating, space heating, spas, industrial processes, desalination and agricultural applications . Geothermal power is cost effective , reliable, sustainable, and environmentally friendly, but has historically been limited to areas near tectonic plate boundaries . Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.

22. ELECTRICITY Twenty-four countries generated a total of 56,786 gigawatt-hours (GW·h) (204 PJ) of electricity from geothermal power in 2005, accounting for 0.3% of worldwide electricity consumption. Output is growing by 3% annually, because of a growing number of plants and improvements in their capacity factors. Because geothermal power does not rely on variable sources of energy, unlike, for example, wind or solar, its capacity factor can be quite large—up to 96% has been demonstrated. The global average was 73% in 2005. The global installed capacity was 10 gigawatts (GW) in 2007. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California, United States. As of 2004, five countries (El Salvador, Kenya, the Philippines, Iceland, and Costa Rica) generate more than 15% of their electricity from geothermal sources.

23. ENVIRONMENTAL IMPACT Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide (CO2), hydrogen sulfide (H2S), methane (CH4) and ammonia (NH3). These pollutants contribute to global warming, acid rain, and noxious smells if released. Existing geothermal electric plants emit an average of 122 kg of CO2 per megawatt-hour (MW·h) of electricity, a small fraction of the emission intensity of conventional fossil fuel plants. Plants that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust. Geothermal plants could theoretically inject these gases back into the earth, as a form of carbon capture and storage.

24. RESOURCES Enhanced geothermal system 1:Reservoir 2:Pump house 3:Heat exchanger 4:Turbine hall 5:Production well 6:Injection well 7:Hot water to district heating 8:Porous sediments 9:Observation well 10:Crystalline bedrock The Earth's internal heat naturally flows to the surface by conduction at a rate of 44.2 terawatts, (TW,) and is replenished by radioactive decay of minerals at a rate of 30 TW. These power rates are more than double humanity’s current energy consumption from all primary sources, but most of it is not recoverable. In addition to heat emanating from deep within the Earth, the top ten metres of the ground accumulates solar energy (warms up) during the summer, and releases that energy (cools down) during the winter.

25. SUSTAINABILITY Geothermal power is considered to be sustainable because the heat extraction is small compared to the Earth's heat content. The Earth has an internal heat content of 1031 joules (3·1015 TW·hr). About 20% of this is residual heat from planetary accretion, and the remainder is attributed to higher radioactive decay rates that existed in the past. Natural heat flows are not in equilibrium, and the planet is slowly cooling down on geologic timescales. Human extraction taps a minute fraction of the natural outflow, often without accelerating it.

26. EFFORTS BY: PARAS GARG IX-A