**1.1 The uncertainty of fossil fuel energy sources to meet world's energy demand**

Before we go to the specifics of solar radiation and solar energy applications, we will discuss the inadequacy of the fossil fuels to meet the energy demands of the world now and in future and the potential dangers inherent in continue to use them.

The known conventional energy sources are: fossil fuels, which include coal,oil,natural gas and nuclear. Among the conventional energy sources, fossil fuels are the chief and the world's current main sources of energy .

The fossil fuels are unfortunately depleting fast to a point where it is unlikely to be able to sustain the great rate of the world energy consumption within the next 200 years. It is in fact understood that about 80% of the world's oil reserves have been consumed by 1980 at the rate of the world energy consumption in 1975 (Meinel and Meinel 1975) The remaining reserves of coal in the world is estimated to last for about 25 years, while the life expectancy of the oil and gas reserves in the world is not positively known.

As of now oil remains the chief source of energy of the world. According to Eden (1983) the projected world total energy demand, if oil were only the source, is 130 106 barrels per day by the year 2000 whereas at that time the possible production of it is put at about 53 106

barrels per day. This would represent about 38.5% of demand. This indicates the incapability of oil to continue to meet the energy demand of the world.

As the world population increases and the economic standard of third world countries improves, there is an expectation of an unprecedented rise in the global energy demands. To allow the traditional energy sources, that is, fossil, nuclear, or hydro fuel to meet these increasing energy demands now and for too long in the future will be unwise and suicidal. The reasons for this strong opinion being:


It has also been recognized that the heavy reliance on fossil fuel has had an adverse impact on the environment. For example, gasoline engines and steam-turbine power plants that burn coal or natural gas send substantial amount of sulphurdioxide (SO2) and nitrogen oxides (NO2) into the atmosphere. When these gases combine with atmospheric water vapor, they form sulphuric and nitric acids, giving rise to highly acidic precipitations which are very dangerous to plants and human beings. Further more, the combustion of fossil fuels also releases carbon dioxide into the atmosphere; the amount of this gas in the atmosphere has been observed to have steadily risen since the mid 1800, largely as a result of the growing consumption of coal, oil and natural gas. More and more scientists believe that the atmospheric built up of carbon dioxide (along with that of other industrial gases such as methane and chlorofluorocarbon) may induce a green house effect, causing the rising of the surface temperature of the earth by increasing the amount of heat trapped in the lower atmosphere. This condition could bring about climate changes with serious repercussions for natural and agricultural ecosystems.

Similarly, nuclear power generation as a source of alternative energy faces lots of social objections due to the possible radiation hazard that it may cause during production. Scientists cannot estimate the extent and gravity of destruction, both immediate and long term, that nuclear radiation hazard can cause when nuclear power reactor accident occurs such as the case of the Russian's Chernobyl nuclear power plant accident in 1987, and the recent nuclear energy plants accident(tsunamis) in Japan, which gravity and extent of damage to life and properties cannot now be estimated and for how long the damaging radiation will be absolutely controlled. By this many countries are signing off nuclear energy utilization.

Moreover the nuclear power material if inappropriately stored could end up in wrong hands and get turned into weapon of mass destruction that will make terrorism assume a much more dangerous dimension.

However, nuclear energy is hoped to be potentially capable of at least deferring the world energy starvation for a long time. In fact it may be capable of taking over the bulk of energy supply as the fossil fuels become exhausted.
