newly industrialized countries will also use the same amount. These are the assumptions for the third scenario showing a five fold increase of the current energy need until 2100. [Martin, 1991] It is clear that the sources of energy are inadequate to meet these future energy needs, even if we look at the assumption made for scenario 1 and scenario 2 of halving the energy consumption in the industrialized countries and in developing countries staying at the present low level of consumption. Unless all energy conservation policies will be effective to have less than the double energy usage of the current rate, these projections seem to constrain the development of the non industrialized countries. The third scenario, predicting a stabilized energy consumption in the developed countries at the current level and an increase of consumption to the same level in the developing countries, seems to be realistic. New Options for Energy Model by Dessus and Pharabod This model examines a possible evolution for energy demand assuming no sudden shifts in energy production or introduction of new energy sources. It reflects the major environmental concern facing the world while allowing for the structure of developed societies to reach a per capita energy usage approximately half of that in the currently developed countries by 2050. [Dessus, Pharabod, 1991] It is also a low economic growth model with emphasis on sustainibility in economic and environmental terms. The increasing importance of environmental impact into energy costs leads to the need for alternative sources which should be also more economically attractive. According to most environmental forecasts continuation of the current emphasis on worldwide economic growth and ever-increasing industrial output levels would lead to an unsustainable buildup in greenhouse gas levels and depletion of fossil energy stocks. Thus the assumptions are the following: • Stabilization of CO2 emissions by 2100 to levels that the atmosphere can absorb. • Population growth to 11 billion, taken from the UN estimates (UN Pop. Bull. 1982). • Reduction in per capita energy demand of 50% in the developed world by 2050. • No nuclear fission power beyond 2100, and no new capacity beyond 2070. • Evolutionary development of currently-existing alternative energy sources. • Renewable energy sources in substitution for fossil fuel resources. This model comes up with a very small increase of future energy needs in 2100 which are far behind the estimated values in the other models. It seems to be too restrictive in terms of environmental issues and economic growth. Oak Ridge Long Term Global Energy CO2 Model by Edmonds and Reilly The Oak Ridge Long Term Global Energy CO2 model was developed by Edmonds and Reilly 1983- 85 and provides future energy demand and CO2 balances to 2100. [Edmonds, Reilly, 1985] This model calculates the change in atmospheric CO2 concentration that results from the emission of CO2 into the atmosphere from fossil fuel combustion. By imposing the greenhouse constraint a limit is set on the allowable fossil fuel use for energy production. Out of this model it is possible to determine to which extent fossil fuel alternatives should be developed and deployed. The energy demand was calculated out of information as population growth and technology improvement parameters, to forecast the regional and global gross national product and therefore energy demand, using the correlation between energy consumption per capita and GNP per capita. The allowable energy production from fossil fuel was determined by the need to prevent the global greenhouse warming and is shown in Figure 2.5. A shortfall in energy becomes apparent and this shortfall will be the reason for using non fossil fuel energy sources. In order to hold the globally averaged temperature to its 1990 value, fossil fuel energy production must be cut down immediately by two thirds. If we allow a 1 degree Celsius per century global warming the fossil fuel energy production must be reduced by one third. [Hoffert, 1991] This figure shows a projected world energy shortfall, determined by subtracting allowable fossil fuel energy production (based on a 1% annual decrease in fossil fuel energy production from 1990 on) from the projected annual fossil fuel energy demand. The allowable production was determined by the need to prevent the global greenhouse warming. [Hoffert, Potter, 91] The energy demand for 2100 in this model is also predicted to be at the same level like in the third scenario given in the model of Lomer. Note that le+12 Gigajoules /year = 32 TWy/year.
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