SRC-212

A process-based life cycle sustainability assessment of the space-based solar power concept. IAC-20,C3,1,5,x58791, 71st International Astronautical Congress.

Published claims resting on this source

• CLM-0316 In 2009 three researchers guessed that, once the energy to deliver and use it is counted, an oil-based fuel must return at least about 3 times the energy put into it, and a society's main fuels about 5 times, to support modern life; a search found no open, peer-reviewed calculation of where space solar power sits against such thresholds.
• CLM-0810 A 2020 modelling study estimated that, across its whole operating life from 2040 to 2100, the 1978 NASA/DOE space solar power design would produce about 112 grams of CO2-equivalent per kilowatt-hour for the silicon version and about 123 grams for the gallium-arsenide version, counting emissions from the rocket launches.
• CLM-0811 In a 2020 modelling study of the 1978 NASA/DOE space solar power design, the carbon per kilowatt-hour fell the longer the satellites were assumed to keep running, because the fixed launch and manufacturing emissions spread over more electricity; but the paper says it would take 67 to 77 extra years beyond the 30-year base case before that design matched ground solar panels, which it calls hard to envision.
• CLM-0812 A 2020 modelling study of the 1978 NASA/DOE design estimated that its ozone-depleting emissions, almost all from burning rocket fuel at launch and averaged per year over the 60-satellite programme, would be several times the yearly ozone-depleting impact of all human activity in the reference figures it used, and would exceed the planetary safe limit for ozone for the silicon version and come close to it for the gallium-arsenide version.
• CLM-0813 The paper's detailed component-by-component calculation gives a carbon figure five to six times higher than an older top-down calculation of the same 1978 design, and the paper is itself inconsistent about whether that older figure counted carbon dioxide only or all greenhouse gases.
• CLM-0814 A 2020 conference paper's own cost model put the whole 60-satellite programme of the 1978 US reference design at about 3.86 trillion US dollars in present-value terms for either version, and the cost of launching each kilogram of hardware at about 407 dollars for the silicon version and 375 for the gallium-arsenide version. The paper never says which year's dollars these are, although it gives its cost per kilowatt-hour for the same system in 2015 dollars.
• CLM-0815 The 2020 study of the 1978 NASA/DOE design did not count any warming from the microwave beams themselves, saying that is too hard to express as a CO2 figure and, on an outside estimate it quotes, would warm the planet by only about six thousandths of a degree even with thousands of satellites; it also assumed that at end of life the ground receivers are dismantled and the satellites recycled in orbit, an assumption the authors added because the original 1978 design never specified one.
• CLM-0816 In their 2020 study of the 1978 NASA/DOE design, the authors list their own weak points: only whole-system detail rather than part-by-part, a background database built mainly on European data and patched with substitutes, social impacts assessed only for supply-chain actors and workers because organisations would not share data, and seven impact categories that lacked weighting factors and could not be checked against any global or planetary-limit yardstick because none had then been defined for them.
• CLM-0817 The authors state openly that a space-solar-power advocacy non-profit paid for this study, that part of the reason was to test or support the environmental marketing claims made for the technology and potentially justify funding future missions, and that the lead researcher says the work was kept rigorous regardless; two of the four authors work for that funder.
• CLM-0852 Checking the study's own sums, its headline carbon-per-kilowatt-hour figures are averages across all sixty satellites over the whole programme's life, not the figure for one satellite, and the numbers add up correctly.
• CLM-0853 The wide range of published carbon figures for space solar power is not simply disagreement: most of it separates into two causes, which calculation method was used and which satellite design was assessed, and the method effect does not even point the same way in every case. The lowest published figure also counts carbon dioxide alone, while the others count all greenhouse gases, so part of the spread is a difference in what was counted.
• CLM-0824 This is a 2002 discussion paper that says it summarises two 1998 discussion papers by an overlapping group of authors, does not point to any later peer-reviewed version of itself, and cites none of the later UK-led work, which it predates, that redid the analysis by a different method, counting other greenhouse gases as well as carbon dioxide, and got a much higher figure.
• CLM-1462 (low confidence) A 2020 paper's finding that its detailed method gave five to six times the carbon of an earlier, simpler study of the same 1978 design compares a carbon-dioxide-only figure with a figure that also counts other greenhouse gases, and the paper labels the earlier figure two different ways in two places.

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