viii The baseline lifecycle GHG emissions intensity for RD1 is 26 gCO2eq./kWh and for RD2 is 40 gCO2eq./kWh. For comparison, the U.S. electric grid in 2021 produced an average of 385 gCO2/kWh. 10 Launch is the largest driver and leads to 64% and 72% of the GHG emissions for RD1 and RD2, respectively. GHG emissions intensity for both RD1 and RD2 fall within the range of GHG emissions intensities (13-43 gCO2eq./kWh) for terrestrial renewable electricity production technologies. For comparison, the GHG emissions intensities of coal and natural gas are 486 gCO2eq./kWh and 1001 gCO2eq./kWh, respectively. 11 RD1 and RD2 emissions intensities do not include upper atmosphere effects of launch emissions, which are assumed to be worse than producing the same emissions on the surface of the Earth, and still under study by NASA and the academic community.12 Our baseline analysis indicates our SBSP designs may have similar lifecycle GHG emissions intensities to those of terrestrial alternatives, pending further studies launch emission effects in the upper atmosphere. Sensitivity Analyses We conducted sensitivity analyses on the assumptions that drive the lifecycle cost and GHG emissions intensity to evaluate what conditions could allow RD1 and RD2 to be cost competitive (Figure 3). We varied the following input parameters one at a time to assess their individual impact on lifecycle cost and emissions: launch costs, first unit manufacturing costs, manufacturing learning curves, hardware lifetime, solar cell efficiency, and orbital transfer methods. Lower launch costs or use of electric propulsion to transfer mass from LEO to GEO each resulted in the most significant reduction of LCOE to about 0.20 $/kWh for RD1 and to about 0.50 $/kWh for RD2. This decrease is not enough to make the representative designs cost competitive with terrestrial alternatives. Cost competitiveness can be achieved by varying multiple assumptions (Table 1) at the same time to provide a combination of cost and capability improvements beyond the advances already assumed in the baseline assessment. This favorable combination reduces the LCOE to 0.03 $/kWh for RD1 and 0.08 $/kWh for RD2, figures that are competitive with terrestrial alternatives. This combination also reduces the GHG emissions intensities (3.78 gCO2eq./kWh for RD1 and 4.33 gCO2eq./kWh for RD2) to values less than nuclear and wind-without-storage technologies. 10 EIA, (2022, November 25), How much carbon dioxide is produced per kilowatthour of U.S. electricity generation? https://www.eia.gov/tools/faqs/faq.php?id=74&t=11. 11 Ibid. 12 National Oceanic and Atmospheric Administration (2022, June 22), Projected increase in space travel may damage ozone layer, https://research.noaa.gov/2022/06/21/projected-increase-in-space-travel-may-damageozone-layer/.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==