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This analysis assumes that the funding organization is American as compared to international, and that the only benefits tallied are those which occur to Americans who remain on Earth.


The price of electricity is approximately equal to its cost plus a normal rate of profit. Busbar costs are the costs of power at the generation station; for SSPS's, the receiving antenna. They do not indude the costs of distributing the power through the electrical grid to consumers. In 1974 the cost of electricity produced by nuclear (light water reactor) plants was 15 mils/kW-hr, by coal 17 mils, and by oil considerably more (refs. 3 and 7). The cost of electricity today is not as important as what it will be in the future. An optimistic projection is a constant price until 2045 of 14.1 mils (ref.7).

There are several terrestrial-based technologies such as the fast breeder reactor, fusion, and central station solar which might be developed during the period under consideration. The least expensive of these will probably be able to produce electricity at 11.6 mils, not including a charge for development costs. When the latter cost is taken into consideration as well, it is reasonable to take 14.1 mils as the price which space colonization power must meet to be competitive (Manne, A., personal communication, June 24,1975).

The market for electricity can be divided into two types, baseload and peakload. The baseload market is where the sources which generate electrical power are run until maintenance requires a shut-down. Peakload plants are run for much less time to satisfy fluctuating demands for electricity with the hour of the day and the time of year.

All of the costs given in appendix D assume that the electricity produced is used in the baseload market. Since space colony power is cheaper than its competitors, all new baseload plants are likely to be SSPS's.

Manne and Yu (ref. 7) project a fixed cost of a constant 7.2 mils for coal and 9.6 mils for nuclear, while the variable costs are 12.0 mils for coal and 4.5 rnils for nuclear. The costs of peakload power are the fixed costs plus a fraction of the variable costs which depends on the amount of plant utilization. In the absence of space colonization, coal will dominate the peakload market, as well as be important in the baseload market. The fxed cost of 7.2 mils for coal suggests that space colonization power will not compete in much of the peakload market. When new plants are needed for the peakload market, rather than build new coal plants, it would be more economical to convert some of the coal plants from the baseload to the peakload market and replace the loss in the baseload market with SSPS's.

For the foreign market it was assumed that no power would be sold to other nations for the first 2 years after the introduction of the first power plant. Afterward, one-third of the power produced would be sold abroad. This level of exports is consistent with past experience of building and selling nuclear, central-station electric power reactors (ref. 1).

The growth rate of electricity demand is assumed to be 5 percent per year. The Energy Research and Development Administration's scenarios, for 1975-2000 (ref. 2), involve a growth rate of 5.7 percent for intensive electrification. Since space colonization could lead to a large supply of low-cost electricity, it would imply that a 5 percent growth rate appears reasonable. The 5 percent growth rate was chosen to be consistent with a price of 14.1 mils. The consistency of a 14.1 mil price and a 5 percent growth rate is supported by Manne and Yu (ref. 7) and Hudson and Jorgenson (ref. 8).

The fact that new technology offers more risks than established technology results in fewer sales than the market size indicates. This occurs, even though the new technology is cheaper, because some potential customers who would otherwise be buying hold back, waiting to see if the new technology actually works. The percentage of the U.S. market size assumed obtainable for each of the first 10 years after the initial terrestrial SSPS is operational is: 10, 12, 16, 20, 25, 32, 40, 45, 50, 60. From then on it is 100 percent.

A 30-year lifetime is assumed for an SSPS. This is the typical lifetime of Earth-based electric power plants. At a 5-percent growth rate for 30 years, the market grows by a factor of 4.3. Therefore, the market for new plants due to growth is taken as 4.3 times as large as the market for replacement.

The number of new terrestrial SSPS's that can be sold per year and the ways in which this changes over time is calculated and given in column 3 of table 6-12. An example is to calculate the number for year 20. In 1975 the U.S. consumed 224 GW of electricity. At a 5 percent growth rate this will be 594.34 GW by year 20. The additional power needed for growth in year 20 is 5 percent of this. In addition, there is the replacement market which is such that the growth market is 4.3219 times as large. To take into account the foreign market, multiply by 1.5. Finally, since this is only the sixth year in which terrestrial SSPS's have been produced, take 40 percent of the foregoing to correct for market penetration. This gives 21.96 GW. SSPS's are assumed to be utilized 95 percent of the time, with the remainder being required for maintenance. Thus, to provide this level of power, 2.31 power stations of 10 GW are needed.

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