IQi-Ihin-Film SPS and Global Energy Requirements If the power level and specific power of an SPS are known, then an assessment of global energy requirements can lead to an estimate of the number of SPS's that need to be deployed and thus the mass of terrestrial or lunar material that needs to be placed in geostationary orbit. An assessment of global energy requirements for the next century is given in Reference 27. The assessment was done by combining the results of a carbon cycle model with an atmospheric carbon dioxide/temperature relationship and an energy/economics model. The latter model analyzed market forces and projected the growth in use in fossil fuel and non-fossil fuel energy sources. The carbon cycle model led to a conclusion that a 1% annual decrease in the use of fossil fuels is necessary to avoid a global greenhouse warming. When this decrease in fossil fuel use is subtracted from the projected increase, an energy shortfall emerges. The results are shown in Figure 6, which is based on Figure 8 from Reference 27. The curves in this figure interpolate between energy values calculated for 25 year intervals. The values for the shortfall curve fall very near a straight line whose slope is 0.45 terawatts (0.45 x 1012 watts) per year, with the rate being slightly less at present and somewhat more in the future. It may be argued that the global warming constraint used was overly strict, leading to a rather pessimistic figure for the shortfall. However, if the SPS’s have a lifetime of a few decades, then future nonfossil fuel production capacity will have to increase at faster and faster rates as the world requires more energy and aging power plants need to be replaced. The total energy demand is from 9 to 35% higher than the fossil fuel energy demand over the time interval shown. Furthermore, the present annual increase in world energy demand is 2.6%; if this continues, then the world will use 192 terawatts, with an additional 5 terawatts of generating capacity needed per year by the year 2100 [based on Ref. 28], Thus, a figure of 0.45 TW of additional non-fossil fuel power generating capacity needed per year may be rather conservative. If half of this capacity consists of SPS’s (with the other half, perhaps, being ground-based solar collectors, wind power, etc.), then 0.23 TW or 230 GW of SPS generating capacity must be added annually. Since the bicycle wheel with mirror appears to be the most promising design, it will serve as the basis for further calculations. The 10 GHz version (Table 2, row 2) supplies 130 MW to consumers, resulting in an annual deployment of:
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