| Energy from the Sun |
| Tuesday, 19 August 2008 23:55 |
 The renewable energy sources, derived principally from the enormous power of the sun’s radiation, are at once the most ancient and the most modern forms of energy used by humanity. We've used the Sun for drying clothes and food for thousands of years, but only recently have we been able to use it for generating power. In fact, solar power both in the form of direct solar radiation and in indirect forms such as bio energy, water or wind power was the energy source upon which early human societies were based. When our ancestors first used fire, they were harnessing the power of photosynthesis, the solar-driven process by which plants are created from water and atmospheric carbon dioxide. Most energy sources on Earth are forms of indirect solar energy, although we usually don’t think of them in that way. Coal, oil and natural gas derive from ancient biological material which took its energy from the sun (via plant photosynthesis) millions of years ago. All the energy in wood and foodstuffs also comes from the sun. Movement of the wind (which causes waves at sea), and the evaporation of water to form rainfall which accumulates in rivers and lakes, are also powered by the sun. Therefore, hydroelectric power and wind and wave power are forms of indirect solar energy. Direct solar energy is what we usually mean when we speak of solar power – it is the use of sunlight for heating or generating electricity.
Solar energy can be converted to thermal (or heat) energy and used to heat water – for use in homes, buildings, or swimming pools. It can also be used to heat spaces, for example inside greenhouses, homes, and other buildings. Solar energy can be converted to electricity in two ways. These include Photovoltaic (PV devices) that change sunlight directly into electricity and in Solar Power Plants where electricity is generated when the heat from solar thermal collectors is used to heat a fluid which produces steam that is used to power generator. The Sun is 150 million kilometres away, and amazingly powerful. Just the tiny fraction of the Sun's energy that hits the Earth (around a hundredth of a millionth of a percent) is enough to meet all our power needs many times over. In fact, every minute, enough energy arrives at the Earth to meet our demands for a whole year - if only we could harness it properly. The major disadvantages of solar energy include the fact that the amount of sunlight that arrives at the earth's surface is not constant. It depends on location, time of day, time of year, and weather conditions. One also has to take into account that the sun doesn't deliver that much energy to any one place at any one time; hence a large surface area is required to collect the energy at a useful rate. The great feature of solar energy is the fact that it is likely to continue to exist so far into the future that we can think of it as being unending. It is, therefore, a form of renewable energy. This is a big contrast with non-renewable energy sources, most of which are running out as we use them. In addition, using solar energy doesn’t cause air pollution or involve damaging the Earth’s surface. It requires no difficult and expensive extraction procedures. |
