Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

New York Times, NPR, and EDN Debate Space-Based Solar Power

Posted by Coyote on August 6, 2008

One of our heroes, O Glenn Smith, has picked up the torch for space-based solar power and is doing all he can to get the word out and to stimulate research and development. He hit two very major news outlets in the same week!

On 23 July 2008, he published an op-ed piece titled “Harvest the Sun – From Space” in the New York times.

Then on 29 July 2008, he was interviewed on NPR (National Public Radio) in a piece titled, “Can We Run the World Off the Sun?”

He an I have enjoyed a couple of very interesting discussions about various opportunities to use the International Space Station for some bits and pieces of the research. I think thats a great idea; every little bit helps.

To provide a sort of balance to the discussion, on 25 July 2008, Paul Rako, the Technical Editor for EDN (Electronics, Design, Strategy, News) wrote a piece titled “Solar Power in Space, A Really Stupid Idea” in response to Glenn’s NY Times article. It is the most scathing review of the concept of space-based solar power I’ve ever seen. In a nutshell, he thinks it’s a veiled attempt to build some sort of weapon. Fair enough. He’s just now learning about the concept and spent only a few hours browsing before writing his article.

Don’t miss the opportunity to read the comments from the bloggers that appear below the article. Some are precious. By the way, keep in mind that a simple inspection of the transmitting antenna can quickly verify that the energy beam cannot be narrowed into a weaponizable configuration.

Let’s be clear on this point; we are pushing for the production of all forms of safe, clean energy in order to prevent energy wars in the future. We’re a bunch of space savvy citizens from many different sectors, but we’re trying to do our part to solve the energy and environmental problems we face while trying to give direction to our space policy and provide real goals to our educational programs. Space-based solar power is one of the things we can do that addresses all of that. We also want these systems to be owned and operated by companies, not governments. That way space becomes an even larger part of our normal, everyday economic environment.

What are your thoughts about these two authors and their opinions? (keep it clean and impersonal)




10 Responses to “New York Times, NPR, and EDN Debate Space-Based Solar Power”

  1. jmurphy said

    The sooner the Pournelle Powerplant sees widespread usage, the better!

  2. Neil Cox said

    The New York Times has an article about solar power satellites (SSP). This is where you put a few square mile of solar panels up in space and then just beam the power down to earth with microwaves. Paul Rako then rants a dozen generalities, if even that relevant “What would it hurt to spend about 100 million on further research?”
    “Energy from space really is one of the crucial ‘three pillars’ of renewable electricity, along with wind and thermal solar farms.” Dr. Paul J. Werbos, Arlington, Va.

    As we face $4 a gallon gas, we also know that alternative energy sources — coal, oil shale, ethanol, wind and ground-based solar — are either of limited potential, very expensive, require huge energy storage systems or harm the environment. There is, however, one potential future energy source that is environmentally friendly, has essentially unlimited potential and can be cost competitive with any renewable source: space solar power.
    Sweeping all the alternative energy sources under the rug, without looking at the complex analog tradeoffs involved is an affront to reason and decency. Pointed out that the technology of this proposal did not matter. This space-panel microwave gizmo was also a weapon and it would be politically impossible to deploy it.
    Make a death machine under the cover of alternative energy.
    Trust me on this one; this solar power in space stuff is a military research project to make a death machine. With 1.37 kW/m2 solar flux I see it as a million square meters, a solar panel 1 km on a side. The 1375 megawatts is reduced to 96 megawatts by the 7% system efficiency they describe.This paper has references, both pro and con. One good resource is S. Fetter, “Space Solar Power: An Idea Whose Time Will Never Come?,” (pdf).
    SPS Pro
    Solar flux density in space is 1.37 kW/m2 as opposed to 1 kW/m2 in Arizona at noon. Rarely, average is about 0.4 kW/m2
    The solar collector can work all day since a geostationary orbit is 24,000 miles up, directly over the equator, and the earth does not shadow the collector. There are no clouds in space.
    SPS Con
    Economics. Launch costs, maintenance costs, safety costs are, literally, astronomical.
    Politics. Like the commentator said, this is a weapon, and by the time we develop it China will have the technology and international standing to nuke Cape Canaveral to keep us from putting it in space.
    Technology. The end-to-end efficiency is 7%. The URSI used 13% solar panels, and Sunpower’s are 17% and they promise 22%, but the URSI article points out you would want to use amorphous silicon for the weight advantage and there’s your 13%. The inefficiency of the radio beam means the microwave inefficiency, easily another 20% loss on a one Gigawatt = 1000 megawatts installation. The solar wind damages the panels; they will have to be replaced about once per decade. One commenter to the article worked on a study and pointed out we would have to launch every two weeks for years just to get one in space. Making the phased array antenna and receiver is a huge technological challenge. Since it is too big to prototype on earth you have to count on computer simulations. Yeah, this should end well.
    Safety. You are trying to aim a microwave beam at a 4-kilometer spot from 24,000 miles up.
    Security. The installation has to be in geostationary orbit. That is directly above the equator. So if you beam the power straight down the receiver has to be on the equator as well. Loses are typicaly minor as far from the equator as 45 degrees = 3100 miles.
    Interference. Pumping gigawatts of RF into our atmosphere is sure to ruin a lot of radio communications that operate at nine orders of magnitude lower power levels or more. The URSI report points out that radio telescopes would be unusable. In addition all you RF folks know that there will be side-lobes and spurs and harmonics on 5.8 GHz so there will be huge swaths of higher frequencies that will now be unusable for radio communications since the gigawatt space power stations are blasting them out of the air. The swaths are narrow if the beam is un modulated from Klysitrons instead of magnetrons.
    One last thing. I hope nobody thinks I am against solar power.
    Meanwhile I do have a couple of ideas. One is for a solar installation that is not grid-tied. I wonder if any one makes a system where the panels just power a dc motor that runs a heat-pump. Then I can have air-conditioning (or heat) and not have to use PG&E. The other idea is to have the panels hinged down the middle on the peak of my roofline, which runs north-south. That way I can get some benefit of tracking in a gross way. In the morning a servo or timer can plop the panels on the east-facing roof, then maybe track the sun till noon, where the panel will look “balanced” on the roof peak, and then follow the sun down so that the panels end up lying against the west-facing roof.
    All power systems are subsidized at some point by the government. Who pays for the right of way of the transmission lines, or suffers eminent domain when land is taken for rectenas?
    Just look at the cumulative negative impact of $700B annual outflows for oil vs. giving every man, woman, and child a free 2kw solar plant. The 2kw plant looks cheap by any measure. Unfortunately 80% (perhaps 95%) of the population does not have a practical place to instal 2 kilowatts of solar panel.
    Your solar panel, microwave death ray: Do you really need all those solar cells or do you just need a small nuclear reactor? Remember the strange lights hovering over Phoenix? The light spectrum was so narrow that some people thought they had to be extra terrestial. No, just testing a new night vision system in an urban environment.
    This is perhaps one of the most maddeningly confused articles that I’ve read on the topic of space solar power.
    Regarding solar, I’m happy to hear that you are all for it when the economics make sense (which is when if all subsidies were equalized on all forms of electric generation, it would be at parity for the power it generates. As for your own roof, what you are describing is a one-axis tracker with your roof ridge-line as the pivot. That’s actually fairly easy to do, as the weight is modest. The real key is to preemptively lock the puppy down to the roof when it STARTS getting windy!

    So what if 40% of the power heats the atmosphere – in a coal-fired power plant 60% goes directly into heating the atmosphere, and then the CO2 emitted traps that much heat again every year for hundreds of years.
    On the launch costs. On that you are currently correct, at today’s launch costs there is no way the economics fly. As for the government and weapons, there are a lot easier ways to fry someone than to launch huge weapons into space and maintain them for decades, all for a weapon that can only focus down to a mile or so with an ground-intensity less than that of sunlight. Big space solar panels to power a big laser might be a weapon, but the microwave beam part would barely keep you warm on a cold night!
    Send up an huge inflatable solar reflector to beam and concentrate the energy down to earth… I still wouldn’t want to live on the same side of the earth with such a powerful accident ready to happen even if it was never used as a weapon although it will be used as one, terroist or otherwise! Since the sun is not a point source the illuminated spot from even a concave mirror is too big, if the miror is more than about 200 kilometers away from the solar site. Free flying balloon suported mirrors may be a good idea.
    Space-Based Microwave Power. It will happen, if not in the USA then in Japan, China, Russia, or Europe.
    Solar panels with an integrated klystron on their back. A ground receiving antenna (called rectenna) over a 7 km square = 49 square kilometers to collect energy.
    I would find such a device more useful for driving ion-beam or passive propellent spacecraft than for powering earth. Aim one at a Mars probe as a power booster, so that it could get there in a matter of weeks instead of years. Or situate one in Mars orbit to power a Martian base. If a weapon can be developed, it almost certainly will be. If we don’t, someone else will. I’d rather that WE have it first: Even if I’m not always too thrilled about the US gov’t, I am thrilled less about almost all the others. I’d also point out that this is merely a stepping stone in humankind moving into space, in a significant way, which we need to PUSH.
    Why not look for a collection of small solutions that collectively solve the problem? A solar system that is just large enough to run your furnace, refrigerator, and 1 light for use when power lines break.
    Radiation levels are about 1/5 the beam intensity under the rectenna (rectifying antenna receiver) since the concept was to have the rectenna mounted above ground, and the land below could be used for farming and ranching, since sunlight and rain would penetrate the rectenna mesh.
    The microwave beam from an SSP can power a high energy laser or colony in low earth orbit.
    I shortened the above and added a few comments. Neil

  3. Coyote said

    JMurphy: What is a “Pournelle Powerplant?”

    Neil Cox: Congrats! I think that’s the longest comment to date!

  4. jmurphy said


    Dr. Jerry Pournelle, PhD, first suggested space-based solar power sats back in the late sixties. He has been a proponent ever since. The concept is his, and is not (very) new.

  5. Coyote said

    Jmurphy: Wow. Are you claiming that Jerry Pournelle preceded Peter Glaser in developing the concept of space-based solar power? Glaser first went public with his work on space-based solar power in 1968. When did Pournelle arrive?



  6. jmurphy said

    I was. I’m not, anymore. But I’ve been following Pournelle’s writings on the subject forever, and I’ve never heard of Glaser before today. My bad.

  7. Coyote said

    Jmurphy: Cool. I’d never heard of Pournelle and you’d never heard of Glaser. We’re in the same boat! (Chuckle) There is still so much to learn about all of this.

  8. constitutionalism said

    Perhaps I have missed them but I don’t find much recent discussion of mining the moon or asteroids to get the materials, or other such methods of reducing lift costs. I also don’t see evaluations of recent advances in photovoltaic technology, and how that might affect project designs.

    I have created a web page for this topic at . Comments are welcome.

  9. Coyote said

    constitutionalism: We’ve discussed that, but decided that we need to build the early generations of space-based solar power satellites here on Earth so we can determine what types of industries we’ll need to re-invent on the Moon. We have much to learn about such fabrication here on Earth before we attempt it in the challenging environment we face on the Moon. That said, I am 100% in favour of developing the Moon, harvesting its resources, and doing satellite construction from there! I suspect that space-based solar power satellites built here on Earth will be set in orbit around the Moon as the first large power stations broadcasting energy to the Lunar surface to drive that development. So, yes, the Moon is clearly the long term goal for such manufacturing.



  10. Neil Cox said

    We can’t mine nearly enough material to make a one gigawatt SSP on the moon until we install a trillion dollars worth of infrastructure on the moon. With present technology, even a crash program would take until 2030, as Earth is also short of infrastructure for a massive moon effort.
    How to do it, is known in considerable detail, but tested by computer simulations and other conditions not exactly like the moon. Many surprises are likely when we actually deliver mining equipment to the moon.
    We will pay about 700 billion for foreign oil in 2008, perhaps a trillion dollars in 2009, unless Pickens plan takes off faster than anyone thinks possible. It is unlikely The USA can avoid 3d world status until 2030 unless we install an SSP of significant power by 2020. So the conclusion is we will run out of time = bankrupt before we can make a significant start on moon or asteroid mining.
    While a man on an asteroid can easily move many tons, due to almost no gravity (that means less mining equipment and lighter mining equipment) typical earth grazing asteroids are about 100 million kilometers from Earth on the average. That is to say they flash past Earth a few times per century and are about as far as Venus on the average. We are not even close to being able to move asteroids into a low Earth orbit, nor would we want to, as an error could total a large city on Earth’s surface. Neil

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