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Abstract:
The oil shocks of 1970s led to spiraling crude oil prices in the world market which prompted planners to view energy security as an issue of national strategic importance. Energy security has an important bearing on achieving national economic development goals and improving the quality of life of the people. World’s dependence on crude oil will continue for most part of the 21st century but the continued dependence on crude oil is loaded against it with inherent price volatility linked to finite global reserves. In addition, global warming, caused largely by greenhouse gas emissions from fossil fuel energy generating systems, is also a major concern. So, there is a need to develop alternate fuels like non-conventional sources, considering the aforesaid two concerns.
This paper describes about the solar energy, one of the non-conventional sources and different ways of using it to convert to electric energy.
Introduction:
As the power demand is going on increasing day-by-day, it is responsible for our engineers to make it available as per the demand. Many of the power generating plant are using non-renewable sources as their primary source. But these may become extinct at any time and before facing the situation we have to choose an alternative to avoid the power crisis. One of the best alternatives is choosing Non-conventional sources like Solar energy, Wind Energy, Tidal energy, Bio-mass energy etc as the primary sources for power generation in power stations. The power from these sources is several times greater than the one, which we are using at the present. Out of these energy sources, the best one which suits for our country is the Solar energy.
The power from the sun intercepted by the earth is approximately 1.8*1011 MW, which is many thousands of times larger than the present consumption rate on the earth of all commercial energy sources. Thus if we convert this to other forms of energy, it may be one of the most promising of the non- conventional energy resources.
As we know that the tropic of cancer passes midway through the earth, our country is one of hottest country in the world after the continent Africa. There are some places in the country where the mercury level raises upto 500c during summer. So, if we use this energy as the primary source for generation almost every house in our country can have power supply and is available at very reasonable cost.
Sun:
As far back as 5,000 years ago, people "worshipped" the sun. Ra, the sun-god, who was considered the first king of Egypt. In Mesopotamia, the sun-god Shamash was a major deity and was equated with justice. In Greece there were two sun deities, Apollo and Helios. The influence of the sun also appears in other religions - Zoroastrianism, Mithraism, Roman religion, Hinduism, Buddhism, the Druids of England, the Aztecs of Mexico, the Incas of Peru, and many Native American tribes.
We know today, that the sun is simply our nearest star. Without it, life would not exist on our planet. We use the sun's energy every day in many different ways.
When we hang laundry outside to dry in the sun, we are using the sun's heat to do work -- drying our clothes. Plants use the sun's light to make food. Animals eat plants for food. And decaying plants hundreds of millions of years ago produced the coal, oil and natural gas that we use today. So, fossil fuels is actually sunlight stored millions and millions of years ago.
Indirectly, the sun or other stars are responsible for ALL our energy. Even nuclear energy comes from a star because the uranium atoms used in nuclear energy were created in the fury of a nova - a star exploding.
Let's look at ways in which we can use the sun's energy which is also called Solar Energy.
What is solar energy?
Solar energy can be converted into other forms of energy, such as heat and electricity. In the 1830s, the British astronomer John Herschel used a solar thermal collector box (a device that absorbs sunlight to collect heat) to cook food during an expedition to Africa. Today, people use the sun's energy for lots of things.
How is solar energy collected?
Solar energy can be used to heat a fluid such as water in solar collector panels. Simple types use flat collector panels mounted on a south-facing roof or wall, each with transparent cover to admit sunlight. Water circulates through channels or pipes inside each panel. The inside is usually painted black, because black surfaces readily absorb heat. The water is heated, and then the hot water is pumped to a heat exchanger that extracts the heat for use within the house.
Solar energy can also be used to generate electricity in photovoltaic (PV) cells. A PV cell may power your calculator. Photovoltaic cells are made of semiconductors, similar to those used to make computer chips.
Until recently these cells were very costly to produce. However, they are still only about 10-15 per cent efficient.
Energy Derivations from Solar Energy:
Solar energy can be converted to thermal (or heat) energy and used to:
• Heat water – for use in homes, buildings, or swimming pools.
• Heat spaces – inside greenhouses, homes, and other buildings.
Solar energy can be converted to electricity in two ways:
• Photovoltaic (PV devices) or “solar cells”
This change sunlight directly into electricity. PV systems are often used in remote locations that are not connected to the electric grid. They are also used to power watches, calculators, and lighted road signs.
• Solar Power Plants -
In this sunlight is converted to electricity indirectly. It is first converted to mechanic energy and later to electric energy. When the heat from solar thermal collectors is used to heat a fluid which produces steam that is used to power generator. Out of the 15 known solar electric generating units operating in the United States at the end of 2006, 10 of these are in California, and 5 in Arizona. No statistics are being collected on solar plants that produce less than 1 megawatt of electricity, so there may be smaller solar plants in a number of other states.