Imagine a power source that never runs out, isn’t affected by cloudy days or the darkness of night, and could beam clean energy anywhere on Earth. This might sound like something from your favourite science fiction film, but it’s a concept scientists and engineers are working on right now: space-based solar power. The idea is to collect the Sun’s immense energy in space and send it wirelessly to Earth, offering a potentially revolutionary solution to our planet’s growing energy needs and the urgent challenge of climate change. This technology holds the promise of a constant and massive supply of clean energy, potentially dwarfing all other energy sources combined.

The dream of harnessing solar power from space isn’t new. Way back in 1923, Russian theorist Konstantin Tsiolkovsky, considered one of the fathers of space travel, imagined using giant mirrors in orbit to reflect sunlight to Earth. Then, in 1941, the famous science fiction writer Isaac Asimov wrote a short story called “Reason,” where a space station collects solar energy and transmits it to planets using microwave beams. These early ideas laid the groundwork for more concrete proposals. The first engineering design for a solar power satellite was developed by Peter Glaser, a Czech-born American engineer, in 1968. He was granted a U.S. patent in 1973 for his method of transmitting power over long distances using microwaves. Throughout the 1970s, NASA and the US Department of Energy extensively researched the concept, and even the European Space Agency (ESA) conducted its first study on the topic in 1979. However, a major hurdle consistently emerged: the high cost of launching materials into space made these ambitious projects seem economically unviable for many years. Solar panels have, of course, been used on spacecraft since 1958, starting with Vanguard I, but the idea of large-scale power transmission to Earth is a more recent and complex endeavour.

So, how would it actually work? The basic concept of space-based solar power (SBSP) involves three main steps. First, large satellites equipped with solar panels, possibly enhanced by reflectors or inflatable mirrors, would collect solar energy in space. These satellites would ideally be in a geostationary orbit (GEO), about 36,000 kilometres above the Earth, or potentially in a medium Earth orbit (MEO). In space, sunlight is more intense and almost continuously available, unlike on Earth where we have night, cloud cover, and atmospheric absorption that can reduce the amount of energy we can collect. A satellite in GEO could be illuminated over 99% of the time. This means a solar panel in space could generate significantly more energy — perhaps 13 times more — than the same panel on Earth, especially in a country like the UK.

The second step is to convert this solar energy into a form that can be sent to Earth. Most designs propose converting the electricity generated by the solar panels into high-frequency radio waves, specifically microwaves, or potentially lasers. This energy would then be beamed wirelessly towards Earth. The third crucial element is a receiving station on Earth, often called a ‘rectenna’ (rectifying antenna). This large array, potentially several kilometres in diameter, would capture the microwave or laser energy and convert it back into electricity, which could then be fed into the existing power grid. Importantly, most designs propose beam energy densities that would not be harmful if people were inadvertently exposed.

Recent years have seen a surge in interest and activity in the field of SBSP, driven by several factors. The urgent need for clean and secure energy to combat climate change and achieve ‘Net Zero’ carbon emissions by 2050 is a major catalyst. Unlike fossil fuels, SBSP would not emit greenhouse gases during operation. Furthermore, the dramatic reduction in space launch costs, largely thanks to reusable rocket technology pioneered by companies like SpaceX, has made the economics of SBSP look much more promising. What once cost around $10,000 per kilogram to launch into Earth orbit has fallen to about $1,000, with potential future reductions to $200 per kilogram.

Several countries and private companies are now actively pursuing SBSP. The UK government and the European Space Agency are investing in research and development. The UK’s Space Energy Initiative, involving over 50 British technology organisations including Airbus and Cambridge University, aims to have a demonstrator power plant in orbit by 2035. They are exploring a modular concept called CASSIOPeiA, developed by the British engineering firm International Electric Company, which could be assembled by robots in orbit. The European Space Agency’s SOLARIS initiative is also assessing the feasibility of SBSP, with a decision on further development expected around 2025. Dr. Nicol Caplin from ESA stated, “The primary driver for space-based solar power (SBSP) is the pressing and immediate need to find an alternative energy source that could wean humanity from its dependency on fossil fuels.”

Across the globe, other nations are also making strides. China has ambitious plans, announcing a test base and a goal to launch a megawatt-grade SBSP station by 2035. Japan has consistently been a key player, with JAXA (Japan Aerospace Exploration Agency) having a roadmap for commercial SBSP and planning to test beaming energy from space to Earth in 2025. In the United States, the US Naval Research Laboratory conducted its first test of solar power generation in a satellite in May 2020, and the Air Force Research Laboratory (AFRL) is developing an in-space power beaming experiment called Arachne, expected to launch around 2025. A significant milestone was achieved in 2023 when a team from the California Institute of Technology (Caltech) successfully demonstrated beaming detectable amounts of power from their Space Solar Power Demonstrator (SSPD-1) satellite to Earth. This experiment, part of the Space-based Solar Power Project funded by over $100 million in donations, used a microwave array called MAPLE to transmit energy that lit up a pair of LEDs on the ground. As John Mankins, a former NASA program executive, commented on the Caltech achievement, “it was a terrific demonstration of technology,” and he believes “we are dramatically closer” than ever before to having an operational solar power station in space.

Despite the immense potential and recent progress, there are still significant hurdles to overcome. The sheer scale of the projects means that the initial investment costs will be substantial, potentially running into hundreds of billions of dollars for gigawatt-scale systems. The satellites themselves would need to be enormous — some concepts imagine structures kilometres across, many times more massive than the International Space Station. Assembling and maintaining these colossal structures in orbit presents a major logistical and engineering challenge, likely requiring advanced robotics. Paul Febvre, CTO at Satellite Applications Catapult, noted that a 2GW power station would likely have a mass of 2,000 to 5,000 metric tonnes, requiring over 100 launches even with heavy-lift rockets like SpaceX’s Starship.

Energy transmission efficiency and safety are also key considerations. While wireless power transmission has been demonstrated, doing so efficiently over tens of thousands of kilometres from GEO with gigawatts of power is a different order of magnitude. The rectennas on Earth would also need to be very large, covering many square kilometres, raising land-use concerns. There are also concerns about the long-term durability of solar panels in the harsh space environment, where they are exposed to high levels of radiation and the risk of damage from micrometeoroids and space debris. Indeed, solar panels in space can degrade up to eight times faster than those on Earth. The increasing amount of space debris is a general problem for all space activities, and large SBSP constellations could potentially exacerbate this issue if not managed responsibly.

Environmental and ethical considerations also need careful attention. While operational SBSP systems would be clean energy sources, the environmental impact of manufacturing the components and launching numerous heavy rockets needs to be assessed. The potential effects of low-intensity microwave beams on the atmosphere, or on flora and fauna, although generally considered safe in current designs, require ongoing study and validation. The European Space Agency is actively soliciting research on these aspects, including risks to human health, wildlife, and impacts on the atmosphere and aviation. Furthermore, the governance of space and the equitable allocation of resources and energy transmission rights will require international cooperation and robust regulatory frameworks to prevent a “Wild West” scenario or the militarisation of this technology.

Proponents argue that the advantages of SBSP are compelling enough to warrant the significant investment and effort required to overcome these challenges. The ability to provide a continuous, baseload power supply, 24 hours a day, regardless of weather or season, is a major selling point. This could make it a reliable partner for intermittent terrestrial renewables like wind and ground-based solar, helping to stabilise energy grids. Sam Adlen, Co-CEO of Space Solar, highlights the economic potential, suggesting that the levelised cost of electricity from SBSP could be competitive with, or even cheaper than, other baseload power sources like nuclear fission. He states, “SBSP offers highly desirable characteristics and favourable economics…The compelling economics is driven by the fact the solar panels in space receive about 13 times more incident energy in space then they do on the ground for a country like the UK.” Another significant advantage is the ability to redirect power relatively quickly to areas in need, such as those affected by natural disasters or in remote locations without established grid infrastructure. The National Space Society also points out that if materials for SBSP systems could eventually be sourced from the Moon or near-Earth asteroids and manufactured in space, the terrestrial environmental impact would be virtually zero.

The future outlook for SBSP seems brighter than ever, with predictions that the first commercial systems could be operational in the 2030s, contributing significantly to the global energy mix by the mid-century. The UK’s Space Energy Initiative aims for an operational system delivering power to the grid by 2040, with a constellation of solar power satellites by the mid-2040s. Companies like Space Solar in the UK are working on designs like CASSIOPeiA, aiming for a commercial product by 2029 and to power over a million homes by the 2030s. Martin Soltau, chairman of the U.K. Space Energy Initiative, confidently stated that all the necessary technology “already exists; the challenge is the scope and size of such a project.”

In conclusion, the journey towards harnessing solar power from space is a monumental undertaking, filled with complex scientific, engineering, economic, and ethical questions. However, the potential payoff — a virtually limitless, continuous, and clean source of energy for our planet — is an incredibly powerful motivator. As research accelerates, international collaborations form, and technological hurdles are incrementally overcome, the science fiction dream of drawing down power from the stars is moving ever closer to becoming a tangible reality. Will space-based solar power indeed become a cornerstone of our future energy infrastructure, helping to power a sustainable world for generations to come? The coming decades will be crucial in determining whether this ambitious vision can truly take flight.

References and Further Reading:

1.  Space-based solar power – Wikipedia.

2.  ESA – Space-Based Solar Power overview – European Space Agency.

3.  Space-Based Solar Power – NASA.

4.  Is Space-Based Solar Power Our Future? (May 2025) – GreenMatch.

5.  The Pros and Cons of Space-Based Solar Power – Renewable energy magazine.

6.  Space Solar Study Advances Commercial Space-Based Solar Power – Space Solar.

7.  Space Solar Power Info: Limitless clean energy from space – National Space Society.

8.  Space-based solar power | Definition, History, Advantages, & Facts | Britannica.

9.  Space Based Solar Power – Space Energy Initiative.

10. ESA – SBSP history – European Space Agency.

11. Can We Put Solar Panels In Space? – The Eco Experts.

12. Solar from Space? New Advancements and How it Might Happen – PowerMarket.

13. Generating electricity in space to power our future generations – Sia Partners.

14. Space Energy Initiative, Space-Based Energy solutions to address global energy challenges.

15. Space-Based Solar Power: A Sci-fi Concept or Reality? – Green.org.

16. Top Companies List of Space-Based Solar Power Industry – MarketsandMarkets.

17. Solar panels on spacecraft – Wikipedia.

18. SPACE POWER BEAMING – Air Force Research Laboratory.

19. Space-Based Solar Power Enablers – Satellite Applications Catapult.

20. Space-Based Solar Power: A Near-Term Investment Decision – The Aerospace Corporation.

21. Space-Based Solar Power – EVONA.

22. Beam us down, Scotty: space solar power straight to Earth – Nesta.

23. Space Based Solar Power — Second Generation Green Energy – techUK.

24. Breakthrough coming? Iceland could get solar power from space in 2030 – Space.com.

25. How Does Space-Based Solar Power Compare to Other Renewable Energy Sources in the Context of Environmental Impact? – Medium.

26. Are space-based solar farms the future of clean energy? – HSBC Global Private Banking.

27. Advantages and Disadvantages of Space-Based Solar Power – TS2.space.

28. A solar power plant in space? The UK wants to build one by 2035. – Space.com.

29. Is There a Bright Future for Solar Power from Space? – Engineering.

30. Top 10 Companies in Space-Based Solar Power Market in 2024 – Emergen Research.

31. Space-Based Solar Power Market Size, Share & Trends — 2034 – Global Market Insights.

32. Help ESA research key space-based solar power challenges – European Space Agency.

33. Space-Based Solar Power: The Pros and Cons – Shanghai YIM Machinery and Equipment Co.ltd.

34. Space-based solar power: ‘We have nothing to lose and everything to gain’ – Physics World.

35. Exploring the Promise of Space-Based Solar Power: ESA’s SOLARIS Initiative – TRL11.

36. Expert Q&A: space based solar power – The Engineer.

37. The Case for Solar Power From Space – National Space Society Ad Astra Magazine.

38. Space-based Solar Energy Market Report 2024-35 – Juniper Research.

---