Solar Energy
When we think of energy, it is often in terms of coal, oil and gas. Yet the earth receives as much energy from sunlight in twenty days as is believed to be stored in this planet’s entire reserves of fossil fuels. Although the sun releases ninety five per cent of its energy as visible light, it also produces infra-red and ultra-violet rays. Each part of the solar spectrum is associated with a different energy. Within the visible portion of the solar spectrum, for example, red light is at the low-energy end and violet light is at the high-energy end, with fifty per cent more energy than red light. Scientists often think of light as travelling in small packets, called “photons”, rather in the same way that water is transported by passing full buckets along a chain of people. Photons in the invisible ultra-violet region have more energy than those in the visible region. Likewise photons in the infra-red region, which we feel as heat, have less energy than those in the visible region.
Most forms of life on earth have actively used the energy from the sun for millions of years. Humans have long sought to harness solar power. Some 2,000 years ago the Greeks used mirrors to focus the sun’s rays on Roman ships, causing them to catch fire. More recently, scientists and engineers have searched for ways to convert the sun’s energy into electricity. It has long been used to be assumed that much land was needed to gather solar energy. In reality small-scale applications – such as unused space on the roofs of buildings in urban and industrial areas – can be used very effectively. Other areas of exploration include sea solar power, or setting a solar collector in space to store the sun’s energy and beam it down to earth to be converted to electricity. There is still much to learn, but hopefully it is only a matter of time before our understanding of solar power matches our need to harness it.
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