person in OECD remained at the same level as now. If newly industrialized countries also used this same amount of energy, the total annual requirements would increase by about five times the current amount by 2100. More optimistic scenario predicts that industrialized countries and newly industrialized countries halve their per capita energy usage by the end of the next century, whereas the developing countries increase their energy consumption. These calculations lead to an usage less than 2.5 times the current level, a detailed description of these different assumptions will follow in section 2.1.3. The total world energy demand for the year 2100 will be, depending on the model, 2.5-5 times the current value, but the large predicted population increase over the period would result in a minor fall in worldwide per capita energy use over the period. With economic growth much stronger in the developing world than the developed world, much of this reduction in per capita usage must be met in the developed world. Current trends suggest that the increase in energy demand could be much larger than the available supply. Extra demand for energy does not mean that extra supply will become available. Thus energy supply limits economic growth. There was no net per capita decrease in world energy usage between 1980 and 1987. If this trend continues for the developed world there would be a large gap between available energy and required energy by 2100. The gap would be even larger if it is assumed that the per capita energy use in the developed world continued to grow even at a moderate rate. In the case of such an ‘energy gap' appearing, it would become necessary to fill it with new sources of energy. These could be anything from nuclear fusion to safer second-generation fission plants, solar terrestrial power and space solar power. Even if there is only a small increase in energy needs, a cheaper and cleaner energy supply is economically helpful and makes the world's standard of living increase. The main criteria for selecting new sources will be based on cost, reliability and public acceptance of these new solutions. 2.1.3 Population Growth and Energy Demand Models The first step in estimating future energy needs of the world is to estimate world population levels. The historical record shows that population growth is intimately related to patterns of energy use and advances in technology and by extension to patterns of environmental degradation. Population variables and projections are used as inputs in energy models and, more recently, in models of CO2 emissions. There will be a description of four models in this section: • UN Population Growth Model with Extended Version of the World Bank. • Future Energy Usage Projection Model by Lomer • New Options for Energy Model by Dessus and Pharabod • Oak Ridge Long Term Global Energy CO2 Model by Emonds and Reilly. UN Population Growth Model with Extended World Bank Version The United Nations carried out a demographic analysis for the world population growth until the year 2020. [UN population study, 1986] The actual world population now is about 5.0-5.4 billion people, 75% living in developing countries. In numbers that is 1.25-1.35 billion people in developed countries and 4.75-4.05 billion in developing countries. Since the history rate of population growth in the developing countries is higher than in developed countries the assumptions for the future were: • 3-4% growth rate per year in developing countries, with population doubling times of 20 -40 years. • Less than 1 % growth rate per year in developed countries. The growth rates from the beginning of this century until now were taken for the computations. In the years 1965 70 the world population peak annual growth rate was 2.04% per year, whereas in 1985 the growth rate went down to 1.65%. This number was taken for the High Growth Model, indicating a population of 10 billion people in 2020. The next UN projection was a Medium Growth Model, with a growth rate of 1% per year, resulting in a population of 7.8 billion by 2020. A Low Growth Model was calculated with a growth rate of 0.5% per year, estimating 5.5 billion people in 2020. The most reasonable view seems to be a world population of 7.8 billion, with 1.4 billion living in the developed countries and 6.4 billion living in the developing countries. A further demographical analysis was carried out until 2075 and 2100 from the UN and the World Bank. [Choucri, 1990] The medium growth rate model was again taken for the projection until 2020.
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