1 1.0 Introduction This report describes for NASA senior-level consideration the relative costs and greenhouse gas (GHG) emissions of space-based solar power (SBSP) systems to assess whether SBSP is a feasible option for achieving net-zero GHG emissions compared to alternative renewable sources of electricity production. Our assessment considered two reference SBSP system designs operating in geostationary orbit (GEO) – the lower technology readiness level (TRL) Innovative Heliostat Swarm, (hereafter referred to as Representative Design One, or RD1) and the higher TRL Mature Planar Array (Representative Design Two, or RD2) – and compared costs for their development, assembly, operation, maintenance, and disposal. We also compared the relative GHG emissions of each system by conducting material decompositions for an Economic Input Output – Life Cycle Assessment (EIO-LCA). 1.1 Background In response to climate change, organizations around the world are pursuing a range of policies called net zero. According to the United Nations (UN), “net zero means cutting greenhouse gas emissions to as close to zero as possible, with any remaining emissions re-absorbed from the atmosphere, by oceans and forests for instance.” There is growing U.S. and international policy and legislation on net zero. As of 2021 over 70 countries had set net-zero targets (United Nations, 2023). The U.S. submitted a long-term strategy to the UN in November 2021, officially committing to net zero emissions by 2050 at the latest (United States Department of State and the United States Executive Office of the President, 2021). The electric power sector accounted for 25% of U.S. GHG emissions in 2020, according to the U.S. Environmental Protection Agency (EPA), as shown in Figure 2 (EPA, 2023). The sector encompasses the generation, transmission, and distribution of electricity. Carbon dioxide (CO2) makes up 80% of GHG from the U.S. electricity sector. According to the U.S. Energy Information Administration (EIA), CO2 emissions by the U.S. electric power sector in 2021 were about 1,545 million metric tons (MMmt), or about 31% of the 4,970 MMmt of total U.S. energy-related CO2- emissions (EIA, 2023). These emissions primarily result from electricity generation using coal and natural gas, which are non-renewable energy sources (see Figure 2 inset). In 2021, 40% of U.S. electricity production came from renewable and nuclear sources as shown in Figure 3. The International Energy Agency estimates that to reach net-zero, the world will need to reduce its use of fossil fuels from 80% of the total today to slightly over 20% by 2050 (Bouckaert, et al., 2021). However, the EIA projects that by 2050, 44% of U.S. electricity will still come from fossil fuels (EIA, 2022).
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