Value chain · CLM-0182
In plain terms
When two different research teams assessed the exact same 1978 space solar power design, the older accounting method (which spreads emissions across whole economic sectors) found about 20 grams of CO2 per kWh, while a newer, more detailed method that traces actual physical processes found 5 to 6 times more - showing that the choice of carbon-accounting method and what it covers can swing a headline SBSP carbon number by a factor of five or six.
The claim as recorded
For the identical 1978 NASA/DOE SPS Reference System design, an environmentally-extended input-output (EEIO) analysis (Asakura et al. 2000, expanded by Hayami et al. 2005, using 1990 Japanese input-output tables and covering CO2 only) found approximately 20 gCO2/kWh (falling to about 11 gCO2/kWh in a "breeder" self-replication scenario), whereas a later process-based re-analysis of the same reference design using the Strathclyde Space Systems Database (Wilson et al. 2020) found 112 gCO2e/kWh for the silicon implementation and 123 gCO2e/kWh for the gallium arsenide implementation - a roughly 5-6x difference that the paper attributes to the later study's higher coverage, not to any design change; the earlier figure also counts CO2 only and the later CO2e.
Scope and limits
This does NOT show that all EEIO results understate all process-based results by this ratio in general - the same paper (see CLM-0183) also notes ESA guidance that EEIO can "overestimate" impacts in other contexts. It is one paired case study, on one old reference design, from a research group that also developed the process-based tool used in the comparison (a potential source of bias in favour of finding process-based results "more complete").
What it assumes
Both studies model the same physical NASA/DOE 1978 Reference System (a 1960s/70s-style bulky architecture per the paper's own description), so the difference is attributable to method, not design.
Where it comes from
"the results suggest that the CO2 emissions produced by the system per unit of energy generated would be around 20 gCO2/kWh. This value falls to about 11 gCO2/kWh through a breeder scenario... The analysis was based on an EEIO model which focused exclusively on CO2 (and not other GHGs) using 1990 Japanese input-output tables." "Wilson, et al. (2020) attempted to reproduce these two studies using the Strathclyde Space Systems Database (SSSD)... This study produced considerably higher results due to a higher coverage, notably 112 gCO2e/kWh for the silicon implementation and 123 gCO2e/kWh for the gallium arsenide implementation." (p.5).
Basis: gCO2e/kWh, same underlying 1978 NASA/DOE SPS Reference System design in both cases, cradle-to-grave scope claimed by the later study
Related records
Cite this
energyaperture.com/c/clm-0182
CLM-0182, Energy Aperture, as of 2024-10.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-009
- CLM-0825The authors argue that the cost-based way of estimating carbon is too coarse for a custom-built industry like spacecraft, and they conclude...CLM-0826When the authors redid NASA's own 2024 figures for two satellite designs using their materials-based method instead of NASA's cost-based...CLM-0827The authors say NASA's 2024 carbon figures for two satellite designs came out of a model built on NASA's own cost estimates, and that NASA...CLM-0828The authors say ESA's own space life-cycle guidance advises against the cost-based method because it tends to overstate environmental...CLM-0829The authors leave alumina, black carbon and water vapour from rocket exhaust out of their own carbon study because the atmospheric effects...CLM-0830The authors say an environmental claim about a space technology counts for nothing unless a proper standardised life-cycle study backs it...CLM-0831This is a conference paper from October 2024 that does not claim to have been independently peer reviewed, states that it calculated no...CLM-0849The range of 13 to 43 grams that NASA compares its satellites against comes from one US laboratory's dataset, and the two ends are the...More on the source page.
- Also from SRC-085
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- Contradicted by
- CLM-0824This is a 2002 discussion paper that says it summarises two 1998 discussion papers by an overlapping group of authors, does not point to...CLM-0826When the authors redid NASA's own 2024 figures for two satellite designs using their materials-based method instead of NASA's cost-based...