SRC-023

Space Based Solar Power: De-risking the pathway to Net Zero

Published claims resting on this source

• CLM-0002 The summary report says the beam is strongest at the middle of the receiving site, at about 240 watts per square metre, and argues that this makes it safe because sunlight is stronger.
• CLM-0003 The report gives the receiving site as an ellipse roughly 7 km by 13 km, and states a beam strength of 245 watts per square metre.
• CLM-0005 A second figure of 29 watts per square metre appears in the same report, but it measures electricity produced per unit of land, not beam strength. The two are different things and must not be compared.
• CLM-0006 None of the five main studies mentions the international radio-frequency exposure limits, or any safety standard, or a restricted area around the receiving site.
• CLM-1436 A UK study says that one space solar power system would typically deliver about 2 gigawatts to the grid, and it compares this with the output of a nuclear power station.
• CLM-1441 Documents give the size of the CASSIOPeiA satellite design as anything from 1 to 2 km across. For a full-size version delivering 2 gigawatts from geostationary orbit, the best supported figure is about 1.7 km, from a 2021 study for the UK government. A 2020 report gives 1.6 km and credits the designer's 2019 paper, but that paper gives 1.6 km only as a general minimum for any such antenna at one radio frequency, not as this design's size. None of these is a measured size: the satellite has not been built.
• CLM-1442 A 2021 study for the UK government shows one design, CASSIOPeiA, as about 1.7 km across and 2,000 tonnes, sending 2 gigawatts to the grid from 35,786 km up. Its scale drawing puts it beside the world's tallest building, the 830 m Burj Khalifa, and the satellite is about twice that height. It is a design, not a built satellite.
• CLM-1443 The 2021 study for the UK government says the leading designs need no new materials, but that building them at a sensible cost needs two things that are not yet mature: robots that assemble large structures in orbit, and cheap reusable rockets. It says both are developing fast, that the whole system is at an early stage with considerable engineering risk, and that a programme of design and technology demonstration could address that risk.
• CLM-1444 The 2021 study for the UK government concluded that space-based solar power is technically feasible, affordable at a competitive cost per unit of electricity, and good for the UK economy, and recommended a staged programme of development and demonstration. This is the study's own conclusion; no such system has been built or tested at scale.
• CLM-1445 The 2021 study for the UK government reports that supporters of space solar power say it has become workable and affordable in the last ten years, after long being seen as attractive but too expensive. The study lists five reasons for the renewed interest: the push to Net Zero, launch costs that have fallen sharply and are expected to keep falling, modular designs built for mass production, maturing solar cells, wireless power and space robots, and other countries' strategic interest. It gives no figures for these on that page.
• CLM-1452 By our rough arithmetic, the beam of the UK's full-size reference design would carry about a million times more power than the power-beaming tests checked here that have a stated power: a Chinese ground test in 2022 that sent about 2 kilowatts across 55 metres, and two figures of about a kilowatt reported in the press in 2026, one for a Japanese satellite that is planned and not shown to have flown (a Japanese space agency researcher's 2025 lecture shows the same plan) and one for another Chinese ground test. At the design's peak beam strength, such a test could cover less than ten square metres, against tens of square kilometres for the design, so none of these tests comes close to the full-size beam that the worry about disturbing the upper atmosphere concerns. No output power is stated in the documents held here for a third test, a US Air Force flight test that nothing held shows has launched.

Cite this