Clean energy from space

Collecting solar power in space and transmitting the energy wirelessly to Earth through microwaves enables terrestrial power availability unaffected by weather or time of day. Solar power could be continuously available anywhere on Earth. Credit: Caltech

“Technology capable of collecting solar power in space and beaming it to Earth to provide a global supply of clean and affordable energy was once considered science fiction. Now it is moving closer to reality. Through the Space-based Solar Power Project (SSPP), a team of California Institute of Technology (Caltech) researchers is working to deploy a constellation of modular spacecraft that collect sunlight, transform it into electricity, then wirelessly transmit that electricity wherever it is needed. They could even send it to places that currently have no access to reliable power.

“This is an extraordinary and unprecedented project,” says Harry Atwater, an SSPP researcher and Otis Booth Leadership Chair of Caltech’s Division of Engineering and Applied Science. “It exemplifies the boldness and ambition needed to address one of the most significant challenges of our time, providing clean and affordable energy to the world.”

Atwater, who is also the Howard Hughes Professor of Applied Physics and Materials Science, leads the project jointly with two other researchers: Ali Hajimiri, Bren Professor of Electrical Engineering and co-director of SSPP; and Sergio Pellegrino, Joyce and Kent Kresa Professor of Aerospace and Civil Engineering, co-director of SSPP, and a senior research scientist at the Jet Propulsion Laboratory (JPL).”

Comment: My! My! These are some heavy hitters. Should we find this likely? pl

Beaming Clean Energy from Space – Caltech’s “Extraordinary and Unprecedented Project” (

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21 Responses to Clean energy from space

  1. Leith says:

    Can’t happen soon enough for me. I’ll never see it, but maybe my great-grandbabies will, or their great-grandbabies.

  2. Fourth and Long says:

    You might have better luck using the solar panels to charge up orbiting battery modules and then landing the battery modules somewhere where the stored charge can be utilized. Possibly earth.

    • Peter Hug says:

      I’m not sure that would work on an economic basis – once the battery module is discharged, it would need to be relaunched to be charged once more, and that would not be cheap, even if Musk gets his Starship working (I think he will). Far better to beam the energy down to a rectenna on the ground that can convert it to electricity efficiently. (What you do with the electricity after that is up to you.)

  3. A. Pols says:

    Puff pieces like this were appearing in magazines of the ilk of Popular Mechanics back in the fifties when I was a lad. “Proposals” of this sort were put out as entertaining thought experiments along the lines of “This could work”, because they could indeed work given preconditions of limitless resources to devote to their achievements. It was always the problem of limitless resources that resulted in none of these things ever coming to fruition.
    It brings to mind Mad Magazine’s tongue in cheek proposal for solving NY former Mayor Lindsay’s problems, which were caused by fumbling the ball on snow removal after a big snowstorm. Mad’s illustrated solution was to fill all NY streets with empty dump trucks, allow them to fill up with snow and then simply drive them away when the storm was done with. No problemo…

  4. borko says:

    Maybe one day in a galaxy far far away.
    Doing it on a small scale is one thing, practical application is another.
    Tesla did it in 1890 and plunged Colorado Springs into darkness, New Zealanders are trying some commercial application but has not come to much as of yet.

  5. William says:

    Whether it is possible or not there are much better options for the generation of clean power. Reverse engineering of UFO craft, which logically must run on some kind of massive power source would be a better option.

    In this discussion between Hal Puthoff and Eric Weinstein, Puthoff basically says that such advances have already been made secretly within the private defense community.

    What on earth is the point of dragging bulky solar panels into space if you already can power the planet with anti-gravity engines.

  6. Peter Hug says:

    I see no reason this shouldn’t be possible, in particular if SpaceX gets their Starship running. The major question would be whether it can generate power more cheaply than wind or ground-based PV – and that won’t be an easy goal to meet.

  7. Rob Waddell says:


    It’s an academic exercise that’s worth examining for space exploration or similar but not usable for commercial use on earth. The main reason is that the total efficiency of a power transfer system is the product of all the efficiencies that make up that system. For example (try this on your calculator) Solar cell (50% =0.5), conversion to microwave (0.75), tx antenna (.95), rx antenna (.95) microwave to a.c. conversion (.8). If the the received power required is 50kW then the solar p0wer collected would need to be 185kW. Readers may want to compare that efficiency with a hydro scheme which converts solar power to electric power via gravity (approx 85-90%).
    The above does not include aperture efficiency loss, the loss between the tx and rx antennae due to beam spreading, which as a rough guess could be has low as 5%. With that figure, to get 50kW on earth the solar-satellite would need to collect and transmit nearly 3.7MW.

    I agree that projects like this are examined and prototypes built; on earth first.

    • Barbara Ann says:

      Rob Waddell

      Setting aside cost, you zeroed in on the single most important factor for comparing different power generating technologies – efficiency. I just found this article on recent developments in microwave power beaming. The Naval Research Laboratory claims less than 5% loss beaming 1.6kW over 1km, even in heavy rain. Maybe space-based beaming will become feasible.

      The military uses are obvious if you can beam power to forces located anywhere on Earth. Ukrainian civilians could do with this kind of technology right now.

  8. Barbara Ann says:

    “The basic unit of the system the researchers envision is a 4-inch-by-4-inch tile that weighs less than a tenth of an ounce. Hundreds of thousands of these tiles would combine into a system of flying carpet-like satellites that, once unfurled, would create a sunlight-gathering surface that measures 3.5 square miles”

    Hmmm. 3.5 square miles is actually 878 million 16 square inch tiles, weighing in at 2,744 tons at the 1/10 oz quoted per tile – or about 6.5x the mass of the ISS, without counting the weight of any superstructure or other apparatus required. I read somewhere that you need around 4 acres of PV cells to generate 1MW (at the Earth’s surface). That equates to around 560MW for 3.5 sq miles. The article says you get around 8 times more power from space-based PV cells so let’s call this a 4.5 gigawatt power station.

    Frustratingly the article is missing many of the other details required for a basic feasibility analysis. What is the expected power loss in microwave transmission and conversion to usable power on Earth? Does it have to be in geostationary orbit to focus the energy beam on one location? This would be capable of optimum power generation 24/7, so an obvious huge advantage over terrestrial solar arrays – but no different to a decent sized nuclear power station, for example.

    Northrup Grumman’s funding is interesting, didn’t one of the James Bond movies feature a space-based energy weapon that focused the Sun’s rays?

    • blue peacock says:

      Barbara Ann

      I’m sure the analysis has been done on initial feasibility. I’m glad the engineers and technologists are looking at these multi-decade projects that require multiple steps from feasibility demonstration to prototypes to commercial system.

      It took many years and many billions to build Webb. Many innovations were pioneered in its construction. Today we see the stunning images from deep space. The astronomers and astro-physicists will be digging into the data for new insights into the nature of our universe. We should applaud these dreamers & doers for their vision, ingenuity, tenacity and perseverance.

      Compared to the trillions loaded on future generations to bailout Wall St speculative losses that only benefited the top 0.1%, these are worthwhile endeavors to fund, IMO.

  9. mcohen says:

    Looks like moa are down and out.could use some space power

  10. Lars says:

    I have no idea if it would work, but I remember that they used to laugh at Dick Tracy talking to his watch and also remember what Cristobal Colombo found with his navigational error. On the other hand, I am still looking for my Ford Edsel.

    Time will tell, but I am glad somebody is thinking about it.

  11. jerseycityjoan says:

    I don’t understand these things but what I noticed was completely absent was any discussion of this supplying power to millions of people, much less billions. There were several references to targeting power to a specific area which in emergencies might be good but what we need is power for our whole planet.

    Maybe all ways will not have that potential. But how many households are they thinking they can reach? Is this something that after billions and much work would at best involve much effort and money just for power for a tiny number?

    I also wonder about putting a stuff into space on a massive scale. Musk’s satellites are already getting complaints, aren’t they?

    It does seem like they are having a valuable learning experience which is good. Who knows where it might lead?

  12. KjHeart says:

    Something the size of the projectile used in NASA’s recent DART project could effectively knock askew the orbit of this ‘giant solar panel’ – how much a (degree) change would turn this from a solar collecting to a solar ‘redirecting’ and start some fires on Planet Earth? (just thinking out loud here – eeek!)

    Personally, I like the idea of the Dyson Sphere – plus it just makes great Sci Fi –

    Great comments from everyone – I always learn something =)


  13. d74 says:

    Rob Waddell and Barbara Ann,

    IMO, your calculations (efficiency and mass) make it clear that it’s not a given. However, if the power is not there, the solar power interception starts to be significant. So much less to heat the Earth.

    Don’t shoot me, I’m trying to be positive!

  14. Keenan says:

    Peter Glaser et. al. of Arthur D Little Inc. pioneered this concept as detailed in their engineering analysis & report dated February 1974 linked here:

    • Barbara Ann says:


      Very helpful, thanks. I noted this on p12:

      “Including microwave attenuation, the overall efficiency of microwave transmission from dc in the SSPS to dc on the ground is projected to be about 70%”

      I guess that figure can only have gone up in that last nearly 50 years.

  15. different clue says:

    If this ends up working and is built and deployed, it will need enough security to make sure no evil hacker can ever redirect the beam onto towns or cities or national parks or other targets of choice for a James Bond villain.

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