Solar energy from space

When I was an undergraduate in electrical engineering at the University of Idaho I wrote a paper reviewing the use of microwaves to beam energy from space to the surface of earth. In 1973 Peter Glaser, vice president of Arthur D. Little, Inc was granted a patent for certain aspects of this concept.

I was quite enthralled by the concept. The critics claimed things like:

  • Bird will be cooked by the microwave beams mid flight.
  • Planes which accidently get in the path of the microwave beam will drop out of the sky.
  • The losses will be so great that on earth you wouldn’t be able to power anything bigger than a toaster.

Most of the critics were, to electrical engineers, laughable wrong.

In regards to cooking the birds the frequency of the microwaves would different from your microwave oven. A frequency that was not absorbed by rain and water vapor would be chosen to decrease transmission losses.

The energy density of the microwave beam would be little different than a microwave communications tower. The beam width was quite large and hence large amounts of energy could be transmitted without frying the electronics of anything blocking a small portion of the beam.

There are few things more well known that how to calculate the power loss of electromagnetic radiation in free space. You could power small cities from a single satellite.

There was one problem which did not have a good response. That was the cost to get the materials into orbit and to assemble it in space. If I recall correctly, Little’s study claimed the cost to orbit needed to get down to $30/pound for it to match earth based systems. Again, IIRC, the price at the time was well over $100/pound.

When the Space Shuttle went operation I thought perhaps the costs would be low enough that the concept would be practical. Nope.

It turns out that people are working on the concept again:

Scientists working for the Pentagon have successfully tested a solar panel the size of a pizza box in space, designed as a prototype for a future system to send electricity from space back to any point on Earth.

The panel — known as a Photovoltaic Radiofrequency Antenna Module (PRAM) — was first launched in May 2020, attached to the Pentagon’s X-37B unmanned drone, to harness light from the sun to convert to electricity. The drone is looping Earth every 90 minutes.

An important difference from Little’s plan is that these satellites would be be in low orbit rather than in geosynchronous orbit. This allows a handoff from one satellite to another when a satellite goes into the earth’s shadow.

It’s clean power. And more importantly, in contrast to earth based solar power, it’s 24/7/365.

I wish them luck.

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18 thoughts on “Solar energy from space

  1. I remember that the power sats were part of the rationale for building the L5 colony: To build them in orbit using lunar material (or from an asteroid towed into proximity of the L5 point)

    A similar argument was made for building a lunar base and orbital facility: Build the initial production from units launched from Earth, and then bootstrap to expand production and build the sats without the expense of sending resources from the bottom of the gravity well.

    Of course the launch vehicle designed by congressional committee to maximize pork and PR was never going to be capable of supporting such an operation. Certainly not with NASA running the operation.

    Maybe this time?

  2. LEO satellites have a problem with drag. Every once in a while, they need to boost themselves back up or they come down. Good from a “clean up your space junk” point of view, but it means a steady replacement schedule or a plan for in-orbit refueling.

    Also, the best you’re going to get out of LEO powersats is 18/7/365. Eventually, a city’s receivers will be out of line-of-sight of any satellites that are in sunshine, right in the middle of the night. Not so bad if your need for power is for cooling, but a bit of a problem if you need the juice for heating. Now, if you’re getting regular deliveries of power from space, unlike wind and terrestrial solar, you can just plan for spinning up the nukes or natgas plants from 20% power to full base load for that period. I don’t have a lot of expectations of quantum leaps in municipal power capacitance… energy storage isn’t enjoying an equivalent of Moore’s Law.

    • Nearly all satellites save for small cubesats have thrusters on them for doing orbital station keeping.

      Ion thrusters and Hall Effect Thrusters use electricity and an inert gas like Argon to generate thrust. Satellites are capable of generating enough electricity to power these, and they don’t require large amounts of material; a lot of satellites that use them can maintain orbit for years.

      Also, within the next five years there will be companies capable of giving additional life to orbital assets, either by refueling them directly or clamping a secondary thruster to the outside of the space vehicle that can be used for station keeping.

      I can’t speak at all to whether a space-based power generation system would work, but your claim of coverage doesn’t ring completely true. Starlink has put over 1,000 satellites into orbit, with a plan for an eventual constellation of around 4,000 craft with the intention of providing uninterrupted data service nearly anywhere on the planet.

      • Oh, you’ll certainly have a satellite overhead. Could have dozens overhead at any moment.

        But in LEO, there will be a significant number of them in the Earth’s shadow. Powersats can’t transmit power they don’t get from the Sun, and they don’t store industrial levels of power because batteries are frickin’ heavy.

        LEO polar-orbitting communication satellites can work in the shadow because they’re never more than a few minutes away from getting another top up to their small battery capacity from that fusion ball eight light-minutes away.

        That’s two very different use cases.

    • Tirno, the drag depends on how low the LEO is. If it’s as low as you can reasonable get, yes, drag is an issue. Go up another 50 or 100 miles and it stops being a problem.
      And yes, LEO satellites are in shadow part time. That makes them less efficient. On the other hand, the free space path loss is a lot lower, and the launch costs are dramatically lower.
      A nice optimization exercise would be to figure the launch cost and power budget vs. fraction of time the sun is out, for various altitudes. It may be that a middling altitude, say 1000 miles, works better than “low”. Not so many satellites live in the middle altitudes, but some do like GPS.

  3. The current price per pound to put something in orbit varies…..it starts at about $4500 per lb and goes up. The AVERAGE is about $10K per pound. So it’s going to take a major breakthrough in propulsion technology to get the cost per pound down to a reasonable level that can compete…..or else the cost for power created on earth must rise tremendously. Now if these devices have a MUCH longer lifespan than the current technology used to generate power then the cost per watt over time would eventually make them competitive. But like a LOT of things involving space the BIG hurdle is the obvious one. Climbing out of the massive gravity well that we live in and taking enough cargo with us to make the trip worth while. Current technology is basically building a BIG OLE FIRE under the cargo vessel. Complicated engineering but not a particularly complicated idea. And we are using the rocket fuel that has the MOST energy per unit of mass possible. So more efficient rockets aren’t going to happen. Unless/until
    some other technology is discovered and made practical that provided more power per unit of mass than our current rocket fuel technology space travel is a pipe dream and the use of space will continue to be limited to pretty much the very near neighborhood of Earth.

    • SpaceX broke the $1,000/lb cost to orbit several years ago, and as they continue to get additional launches out of their Falcon 9 boosters, those costs will continue to drop.

      And then there’s Starship…

  4. Always wondered how Skynet would get a power source we couldn’t turn off. Now I know! Very cool!
    The biggest power problems on earth are the way we look at the problem. We’ve been lied to about renewability of carbon based fuels. And the facts are we have all the tech we need to make carbon-based energy as long as the sun is shining.
    The problem is doing so won’t feed the meglo-mania of the controlling class.
    The CO2-sun light-02 cycle, is the basis of all life. And the formulas for expanding it into industrial use have been around since the 1900’s.
    (Just ask Al Gore or John Kerry about carbon offsets?)
    Joe, could terrestrial based capacitors be used to deliver power when we go around to the dark side?

      • And typically have lower energy storage density.

        Caps are great for fast charge /discharge, other approaches (batteries, hydro, etc) are better for storage with extended charge / discharge times.

      • Ya, I have no clue what the best storage system would be. It just seems that capacitors are rock solid. That would be very easy to maintain.
        Upper/lower lake hydro would work. Minus mechanical losses.
        I guess storage would be the second order tech problem.

    • Funny you should mention Skynet.

      In the T3 novel, the Continuum Transporter (T3’s Time Displacement Equipment), IIRC was powered by some form of orbital solar energy source.

      Sorry, just thought it was worth mentioning. :The concept of space-based solar energy always sounded a bit sci-fi (with the exception of SimCity).

      Given SpaceX and similar private space ventures, do you think we could see power producers looking at this as feasible project?

  5. “Little’s study claimed the cost to orbit needed to get down to $30/pound for it to match earth based systems. Again, IIRC, the price at the time was well over $100/pound.”

    Cost to put something into orbit with the Space Shuttle was on the order of $10,000/kg.

    With Elon Musk driving the cost of access to space down to record lows (now in the hundreds of dollars per pound) the ability to build large-scale orbital systems becomes much more possible.

    Starlink is a first gen example of this.

  6. And you think we have a space junk problem now.

    Sadly, we can’t seem to help ourselves. If it is doable, then we’re going to do it. And the time is ripe, especially given the focus on Green Energy. It’s built into our DNA.

    PS. I’d like to know how you’re going to get a payload into space using renewable energy? Railgun? Space Elevator?

  7. Sounds like a plausible argument for massive funding and job creation via coercive redistribution. Any material benefit is somewhat less sure however, as is using a sledgehammer to kill a fly.

    Some will be enthusiastic about it simply because it involves a combination of high tech and space, and that alone will be seen as justification.

    Then there’s the “trophy in the sky” aspect, the “look at what we did” star, dominating the night sky from time to time, showing everyone on the planet who’s in charge and therefore who has the power to do what to whom.

    And that brings up the necessarily gigantic surface area of the satellite, and that means, if it’s in low orbit, several orders of magnitude higher drag than anything ever orbited by Man.

    I’d point out that it’s probably not really feasible by the standard of private enterprise. That simple and rather obvious question has of course never stopped the process of increasingly gigantic public works projects. The justification will not come by way of return on investment in the classic sense, but as a way of “saving the planet” from imaginary dangers.

    A plausible argument can be made that since we’re in something of a CO2 famine right now, the environment would benefit from more coal and natural gas plants. Thus more of the carbon that was once in the atmosphere could be restored back to it. But the idea that Man could ever actually have any positive effect on the environment has been washed from our brains over the course of the last several generations. You know; Mankind has to be bad, because…we just are so shut up.

    • Interesting. It never occurred to me that in this day and age of space travel a government entity would consider putting a power utility into orbit and try to compete with earth based utilities. Who would imagine that might turn out well? I’m surprised you thought it was even plausible.

  8. So, not only does the beam kill anything that passes through it as the satellites orbit, the beams nullify the laws of physics, and nothing that draws more power than a toaster (a – What?) could be powered by this system.
    The global warming true believers are working towards that last one at this very moment.

  9. Gee! If all that mental and chemical energy was directed at producing efficient Earth-Based power generation, then “They” would have control. The gravity well is huge and repairs would be a b__ch. Plus there is still no way to store reasonable amounts of electrical power which we’d be dependent on an intermittent, expensive power source. By the by, are there microwave frequencies that don’t cook birds & humans, aren’t absorbed by water vapor in clouds, and that are not reflected by ice or particulates? Sounds like one volcano puts the lights (and toasters) out. Sort of like Texas with groovey pictures. Makes “storing” electricity as hydrogen sound reasonable. And don’t worry your little head about the destruction from mining the raws and disposing of the toxic trash.

    Factories on the moon or Mars sounds cute, when we can’t get trivial “stuff” made in our own cities. That’s: Lost Opportunity. The guys (persons) making the rockety stuff will not be making the toasters or the water purification hardware. Or toilet paper. Etc.

    With all due respects to Die-Versa-Tee (i.e. NONE), there are lots of people who might monitor and maintain an efficient boiler, but not so many to drive rocketships. Maybe something “simple”like baloon supported antennae to suck electricity out of the big spinning dynamo under our feet? [I can’t see the Northern (or Southern) Lights but I’d bet that they’d make my toaster happy. ]

    Even one time, “disposable”, SciFi has to sound plausable so as to not disturb the “flow”.

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