About 47% of solar radiation is absorbed and converted into heat energy or internal energy. During the day the earth’s surface is warmed up, and during the night this energy is radiated back into space as radiant heat energy.
About 23% of solar radiation is absorbed causing evaporation of water from the oceans and lakes and from the land and plants. The high latent heat of vaporization of water means that a lot of absorbed radiant heat energy is used to convert liquid water into the atmosphere where it forms clouds. Much of this energy then becomes stored as a potential energy in glaciers and rivers. As the water runs back to the sea, the potential energy is eventually converted into heat energy.
A small amount of energy, about 0.2% of the total, drives convection currents in the oceans and the atmosphere. Some of this energy appears as wind power and wave power, which are forms of kinetic energy or mechanical energy.
An even smaller amount of energy, only 0.02% of the total, is absorbed by growing plants via a chemical process called photosynthesis. This energy is converted into heat energy when humans and the animals do work; some is converted into heat as the plants decay and some is converted and stored as fossil fuels (coal, oil and gas), which may also eventually be burnt and converted finally into heat energy.
Solar energy can be used to heat water in solar panels. In some hot countries mirrors have been used to focus enough energy into one place to create a solar furnace. The energy can also be used to produce a small electric current from a solar cell. Banks of these solar cells can then be used to charge batteries and provide electrical energy. The energy in colder countries is not sufficient to make large scale use practical and the weather makes it unreliable but it does have some applications in electronics where the energy required is small- calculators and radios work well on solar power with a storage or back-up battery. Solar energy is used to power satellites and a 50cm square panel should produce enough energy to run a light.
The advantages of solar energy are that the energy from collector panels is produced quite cheaply. Solar cells are made from silicon. The disadvantages are that they are very expensive and it only works when the sun shines.
