Solar energy in progress and future research trends

Solar energy alternatives

The nuclear fusion reactions in the sun yield a huge amount of energy, which is estimated at 3.47 X 1024 kJ per unit time. Only a small part of about 5 X 10_11 of this huge energy is irradiated onto the earth’s surface. The incident solar energy is distributed into many branches as shown in Fig. 4. Solar energy is both clean, inexhaustive and harmless to living organisms on the earth because the harmful short wavelength ultra-violet rays are absorbed before reaching the troposphere by the stratospheric ozone layers and weakened by the air composition and moisture in the troposphere. Solar energy activates the atmosphere thus generates climatic phenomena, but the balance of the energy is absorbed by molecules of the materials on the earth and converted into heat at low temperatures. This is an example of the entropy increasing process of nature. It is, therefore, necessary to plan actively to utilize sun’s photon and high temperature heat-energies before they decay to produce entropy. The artificial utilization of solar energy is also shown in Fig. 4. Two classifications are apparent from this figure and the photon energy has better quality and quantity, which are much higher than that of heat.

The most advanced photon utilization technology is the solar cell to which the photovoltaic effects of semiconduc­tors are applied. They are the standard bearer of new energy technologies because they have a bright future to match these high technologies. Their fruitful development is dependent on cost reduction of power generating systems, which include solar cells.

In fact, all energy sources with the exception of atomic energy have solar energy origin. A sweeping statement yet true to the extent that even coal, oil and natural gas are forms

of solar energy. In order to separate the various forms of solar energy the following three categories are adopted:

1. heat from the sun’s rays which is possible when there is little or no cloud cover. This type of energy is dependent on heat from the sun’s rays and dominated by the multiplicity of methods designed to heat water,

2. power from the sun’s light, any time except at night, cloudy or clear, and finally,

3. power from air or water movement, any time day or night, cloudy or clear.