0191-9067/85 $3.00 + .00 Copyright ® 1985 SUN SAT Energy Council SOLAR ENERGY — DREAMS AND REALITY* H. TABOR Scientific Research Foundation Hebrew University Campus P.O.B. 3745 Jerusalem, Israel Abstract — Fossil fuel reserves will last decades, not centuries. The options are: reduced rate of energy consumption, nuclear and renewables. Concentrating on the last, in particular solar energy, this paper shows both the possibilities and the limitations, in particular that the income of solar radiation is limited. This highlights the importance of the solar space-satellite concept. A pre-requisite to understanding the part that solar energy can play in the total world energy picture is an examination of fossil fuel reserves and other potential sources of energy. Additionally, we must know the present and estimated future consumption of energy on a global scale. Until 1970, world energy consumption was rising at about 5% a year, i.e., consumption doubled in about 14 years. One effect of the energy crisis of the mid-70s was that the annual rate of growth of consumption has dropped to about 2% — or a doubling time of 35 years. Table 1 shows the best estimates of reserves of the three major fossil fuels — oil, gas and coal — with the ultimate reserves including sources not considered exploitable at present. Table 2 shows how long these reserves would last on the basis of a 2% or 5% annual increase in consumption. (The bottom line of this table assumes that most users will have switched to coal, as this represents the major reserves.) The startling result is that the reserves are adequate for decades, not centuries as often claimed. Table 2 is mathematically correct but will, in practice, be modified by economic and social factors. The major economic factor is that as the reserves dwindle, the cost of ‘winning’ them will go up and this could result in a reduced consumption rate. Against this is the social factor resulting from the difference between the developed (industrialized) countries and the developing world. At the present time the industrial world comprising 20% of the world’s population consumes 80% of the world’s energy with the figures reversed for the developing world: on a per capita basis, the energy consumption in the industrialized countries is 16 times that in the developing world. *Lecture to the IEA workshop on “Large Thermal Solar Systems" held in San Diego, California, June 1984.
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