Clean Power space solar power

Published on April 22nd, 2015 | by Tina Casey


Race For Space Solar Power Heats Up With Northrop Grumman, Caltech Partnership

April 22nd, 2015 by  

My, the space solar power field is getting interesting. Just last year the US Navy threw its hat into the ring, and now here comes aerospace powerhouse Northrop Grumman elbowing in. The company has just thrown down a cool $17.5 million to fund the new Space Solar Power Initiative at the California Institute of Technology, with the goal of developing a space-based solar array that can generate electricity as cheaply as fossil fuels.

That’s all well and good, but considering that the cost of wind and solar energy is sinking like a stone down here on Earth, you might be wondering if the new Northrop Grumman–Caltech venture is shooting at the wrong target.

space solar power

Space Solar Power Races Against Fossil Fuels…And Renewable Energy

Actually, both the Navy and Northrop Grumman are on to something. Space-based solar power does have some significant advantages over terrestrial solar and wind farms as well as fossil fuels.

Real estate is the first thing that comes to mind. We’re huge fans of solar arrays that take advantage of rooftops, parking lots, brownfields, and other pre-developed sites, but there are also many solar farms being built on valuable real estate, including former farmland, but that has already given rise to tension with agriculture and habitat preservation.

Wind turbines have a bit more leeway when it comes to an open space footprint, but their sheer size limits site options.

The other main advantage of space solar power has to do with the cost of transmitting solar and wind-generated electricity. Some of the prime open space for solar development on Earth is located in desert regions and offshore ocean sites far from population centers. That means long transmission lines, which, aside from piling on the expense, also pose risks in terms of vulnerability to natural disasters and human intervention.

With space solar power, you don’t get all of those potential headaches — just beam it down and Bob’s your uncle.

To ice the cake, a network of space-based solar power arrays would provide a steady stream of solar power day and night, regardless of weather on Earth, reducing the need for expensive energy storage facilities.

If you want to see a really, really long list of benefits, head on over to the National Space Society.

Okay, So What’s Stopping Space Solar Power?

The new Northrop Grumman Space Solar Power Initiative at Caltech is going to address three main challenges than stand between you, me, and cost-competitive space-based solar arrays.

One is the weight of the photovoltaic cells. They have to be super lightweight to cut down on the expense of deployment, but they also have to be ultra-efficient.

Relatedly, another challenge is the weight of the structure upon which the solar cells will be arrayed.

The third challenge is how to get the solar-generated electricity down here from up there.

Since Caltech happens to run the Jet Propulsion Laboratory for NASA, we’re guessing the institution has a leg up on things. Also of interest is Caltech’s long history of collaboration with Northrop Grumman, dating back to the 1930s.

The plan is to build the Space Solar Power Initiative up to include 50 researchers at Caltech, who will work with Northrop Grumman’s team to carry the project through from foundational research and validation of concepts, to building prototypes.

As for Northrop Grumman, the company is not particularly well known for prowess in the solar energy field, but that could be about to change. Just last year, ARPA-E, the Energy Department’s cutting edge funding agency, took Northrop Grumman under its wing to develop a new hybrid concentrating solar system that deploys a thermo-acoustic engine to generate electricity directly from solar-derived heat.

Group Hug For Space Solar Power

If this space solar power thing really does take off, we’re going to get ready for a giant group hug for US taxpayers.

That’s partly because we’re assuming that Caltech’s work with NASA, the National Aeronautics and Space Agency, will at least indirectly play into the new Space Solar Power Initiative.

We’re also feeling huggy because of the aforementioned US Navy space solar power project. According to the folks over at the Naval Research Laboratory, the transmission of solar generated electricity from space to earth is something of a no-brainer (here’s another take on that topic), so the main stumbling block is just the weight issue.

The Navy is also anticipating that the space array would be assembled robotically, which practically eliminates the need to send solar workers into space.

Follow me on Twitter and Google+.

Image Credit: Courtesy of Naval Research Laboratory.

Tags: , , , ,

About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • nathan

    if the world governments wanted to electricity would be free. a couple of 500 mile wide solar cloth’s stretched out in space along with wireless electricity tech could feed the planet with no need of a pick up station. what will happen is people will have to upgrade there tech with copper wire receivers inside or install one on the roof of homes to feed the entire house.

  • quickstop

    Perhaps if we built a large wooden badger 🙂

  • TinaCasey
  • TinaCasey

    Thank you all as always for a lively discussion. Has anybody had a chance to check into the US Navy’s space solar power research project? Take a look and let us know what you think:

  • Jim Seko

    How could anyone with half a brain take this seriously?

  • Wolf Larson

    If we’re talking about energy that wouldn’t normally be usable terrestrially, either due to a portion of the light captured not being normally incident with the Earth or because it represents a change the balance of reflected light (albedo), would the issue of waste heat build-up and its climate change potential be a concern?

    • sault

      I don’t know how space solar power (SSP) would change the Earth’s albedo. However, waste heat from even 100’s of GW of SSP wouldn’t be an issue. We already have TWs of waste heat coming off the world’s thermal power plants and it hasn’t caused a major problem. And if SSP is used to displace these thermal power plants, waste heat would go down dramatically since the microwave to electricity conversion process and power distribution is so efficient. Not to mention the long-term reduction in global warming from reducing CO2 emissions.

      No, SSP won’t work for a variety of reasons. Changing the climate’s energy balance isn’t one of them.

  • Frank_Truth

    It would also add to global warming.

    • TheAnsible

      How do you figure that?

      • Joseph Dubeau

        The man with the Golden Gun would point it at the polar ice caps.

        • TheAnsible

          Legitimate fear…

      • Frank_Truth

        You are adding energy to Earth that otherwise would escape into space.

        • TheAnsible

          You don’t science so good do you

          • Frank_Truth

            Actually, I do. My field is thermodynamics. What is yours? You don’t do English, logic, or science so good, do you?

          • sault

            Just like my comment above, we already have TWs of waste heat coming off the world’s thermal power plants and it hasn’t really changed anything. If you replace 1 GW of nuclear power with SSP, you’d get maybe 100 – 200MW of waste heat from converting the microwaves to electricity, transmitting the electricity and then using it. However, you’d be eliminating 2GW of waste heat coming out of the cooling towers of the nuke plant, so there would be a huge net decrease in waste heat. Displace a coal power plant with SSP and you get rid of the black soot and the CO2 that warms the climate even more.

          • TheAnsible

            Wow that is pretty impressive. Your comments seemed like a troll. But you are obviously employed by NASA. So I would like to ask you how using PV outside our atmosphere to meet our energy needs would cause greater emissions than say burning coal to meet those energy needs?

          • Frank_Truth

            I am not employed by NASA. And rocket science is outside my purview of expertise. After I read sault’s comment below, I realized I was most likely wrong. That is the difference between an informative rebuttal, and one that was simply an ill mannered, ad hominem attack. This is not a subject I have given much thought to in the past. The issue I alluded to had nothing to do with emissions, but to directly heating our planet. But sault is right, all the exergy we consume heats our planet, and burning fossil fuels might heat our planet more than using a PV. Even though PVs are outside atmosphere they would still heat hour planet.

          • Bob_Wallace

            Consider the waste heat created by the use of fossil fuels, the inefficiency of ICEs and fossil fuel electricity plants.

            We would need to “import from space” 0.3 kWh per mile to drive an EV.

            The EPA estimates that one gallon of gasoline is equal to 33.7 kWh. With a 30 MPG ICEV that is 1.12 kWh per mile. Four times as much “stored” energy is being extracted from below the Earth’s surface and released as heat than we’d import from space.

            Add in the energy it takes to extract, refine and distribute fuel and the amount of released energy is greater.

            And if the collection system was located between the Earth and Sun then the difference would be even greater. Energy would arrive as beamed electricity rather than sunlight.

            (I’m not ready to say the idea would work. But it is interesting….)

          • TheAnsible

            Well Frank I’m sorry for attacking you but this is a subject that I have put quite a bit of thought into it was my minor. So I’m no expert on the subject but I have got my feet wet.

            My comment “You don’t science so good…” was ment in a joking fashion. But you have to understand as far as informative rebuttals go your original comment “It would also add to global warming.” seemed like you were trolling. Being either a proponent for oil and coal or someone who was being sarcastic towards alternative energy.

            Being a huge proponent of alternative energies PV in particular maybe I took your comment a bit too personal and in trying to get you to defend your stance was a bit aggressive.

            I see now that this was miscommunication. But there is no question in my mind that PV is a much cleaner energy than fossil fuels. And the potential for capturing that energy is far greater outside of our atmosphere.

            According to most of the science that I trust climate change is being driven by the increased amount of CO2 in our atmosphere which has been steadily rising since the industrial revolution. To me any technology that combats this should be embraced.

            The article alludes to some of the difficulties of implementing a system such as this so I understand why people question its feasibility. It is no easy task and it is something that has been discussed long ago. And although the technologies that make this feat of engineering more feasible have grown in leaps and bounds and continue to grow many of the arguments against it have not changed.

            It just really gets me going when I see people advocating against alternative energies without taking the time to developed a more informed opinion on the subject. I think back to the days of the space race and how everyone was behind it. It was a badge of pride and I wish more people could get behind alternative energy like we did for putting a man on the moon. [End of rant]

  • Frank_Truth

    I don’t see this this as feasible. First there is the huge cost of transporting materials to outer space. Second is the fragility of objects in space to space debris, and solar flares, and such. The transmission of the energy back to Earth. Light energy would be absorbed by the atmosphere. If it was really hot, it would ionize the atmosphere. The transmission of energy back to the wrong place on Earth could kill thousands of people. This idea seems to me like pie in the sky.

    • sault

      Combining both your comments, you are correct that launching the solar arrays into orbit would be prohibitively expensive. In addition, the main deal-breaker for space solar power is that, even discounting space debris and solar flares, it is very difficult to make rigid arrays much bigger than 20 – 40kW. The fuel required to keep something much larger pointed at the Sun and aligned with the receiver station on the ground would be immense and we have no practical designs to build very large solar arrays with any sort of structural integrity. Exotic nano materials might solve this problem somewhat, but we can hardly get to 100kW right now, let alone the hundreds of MW to even GW-class arrays that would be required to make space solar power feasible.

      Your concerns about this technology worsening global warming or ionizing the atmosphere are misplaced, however. The energy would be beamed back to the ground in the form of microwaves and the Earth’s atmosphere has a nice, big window of transparency to microwaves that gives engineers plenty of frequencies to choose from. And contrary to popular belief, the microwave beam wouldn’t be a “death laser” if it ever went off-track from the receiver station.

      However, the longer the wavelength of microwaves, the larger the ground receiver must be. In some designs, a square km of solar cells in orbit would need a ground receiver for the microwaves of nearly a square km in area, negating any advantages in land use for space solar power. And we’d need to make sure no satellites, manned missions or airplanes got in the way of the beam just to be sure.

      • Frank_Truth

        All the plans I have examined transmit energy to earth that otherwise would have bypassed Earth and escaped into space or would have been reflected back into space. All energy transmitted to the Earth’s surface eventually becomes heat and warms the planet.

        Many of the plans I’ve seen entail sending concentrated light or heat back to Earth that pose that danger I mentioned.

        I would think there would be many reasons for engineers to choose high frequency microwave radiation. I would think it would be more efficient all the way around to use the highest frequency microwave radiation possible. Think about it.

        • sault

          Yeah, the design I’ve been critiquing all this time incorporates microwave energy transfer to the ground.

      • quickstop

        space elevator with graphene based superconductor core
        earth tethered Fibonacci styled self unfolding array
        next gen solar cell

        terahertz radiation beaming/ high altitude articulated energy receivers (shoot the tangent rather than direct to earth…avoid beam of death)

        • sault

          Yeah, and we can make the whole thing out of Unicorn horns!

      • Jenny Sommer

        1GW /24h solar array with more efficient cells and cooling on earth would require the same footprint…
        It wouldn’t be 24/7 on earth though.

    • Brooks Bridges

      Elon Musk is confident he’s going to be able to make rockets that can land, be refueled and take off again – many times. This will lower cost of putting things in orbit by a factor of 100 or more. His rockets are already 1/4 Boeing and Lockheed. He’s estimating a few years. That said, I agree solar from orbit sounds as practical as Regan’s Star Wars.

      • Frank_Truth

        Refoolable rockets will not lower the cost of putting things in orbit by any amount. The cost of putting things in orbit comes from the fuel required to so. It is the fuel that is expensive, and the fuel that cannot be reused. Basically a the laws of physics determine that a certain amount of energy is needed to exceed the escape velocity of Earth. 95% of the weight of every rocket is engine and fuel. The payload must be very light, and therefore the laws of physics dictate it will costs a fortune to lift any payload into orbit unless there is some major breakthrough in propulsion or mode of travel. The fastest way to travel is to shorten distances and to slow time down. If there was some way to shorten the distance between Earth and a distant galaxy to a few thousand miles, it wouldn’t take you long to get there at all.

        • Bob_Wallace

          “The Falcon 9 burns through 29,600 gallons of highly refined kerosene during its trip to orbit.”

          Wholesale cost of kerosene in January 2015 = $1.91. $56,500 per launch. “Highly refined” probably means some filtering cost.

          Payload is 4,850. $11.65 per pound of non-refined kerosene.

          And there’s some liquid oxygen used. I didn’t find an amount per launch.

          I don’t have time to flesh this out at the moment – perhaps someone else can complete the fuel cost per launch.

          • Frank_Truth

            The Falcon 9 costs $1000/lb to launch material in low orbit. I would say that is expensive.

          • Brooks Bridges

            Your reply is irrelevant to Bob’s response which agrees with what Musk says – that to refuel one of his (future, reusable) rockets would cost about the same as refueling a 747 for a long flight. What ever their expense now they’re 1/4 the cost of Boeing and Lockheed offerings.

          • Frank_Truth

            The Falcon 9 also uses LOX. But the only thing that is really important is the cost per pound to launch material into orbit. Nothing else really has any practical consideration.

          • Bob_Wallace

            I stated that the Falcon uses liquid oxygen.

            Lift cost is driven by the cost of the first stage more than fuel. SpaceX is attempting to recover and reuse the first stage which would greatly cut cost to place in orbit.

          • Frank_Truth

            I’ll buy that.

          • Frank_Truth

            I think the laws of physics dictate the energy required to reach escape velocity requires considerable amount of fuel using the type of rocket engines, propulsion systems, and chemical fuels used today. The cost may be cheaper than they used to be, but at $1,000/lb they are still costly. At 200lbs, it costs $200,000 to lift the average human into low Earth orbit. I have an open mind. Let’s see what Musk can do. I like the guy, and like what he is trying to do. I am on the side of encouraging experimentation, and increasing efficiency, I am never the one who discourages anyone from trying to accomplish anything. It is easy to be negative and critical, and humans have often accomplished things once thought impossible. I tend to be very open-minded, but I temper that open-mindedness with a touch of realism, and making some attempt to adhere to known theoretical limitations. I support Musk and hope he succeeds. I am on his side. He is my kind of guy. My intuition and gut feelings in science and technology tend to be accurate. If Musk can bring the cost of payloads down much lower than $1000/lb, I will be happy, and also pleasantly surprised. I would have to see much more peer reviewed objective support for this view before I believed it was a likely possibility in the next 25 years.

          • Bob_Wallace

            IIRC SpaceX has already landed and reused first stage rockets which were lifted only a short distance from the ground.

            Their first recovery failure was weather related, IIRC. The landing target (barge) was being tossed around by weather.

            (I should have looked this up but I’m pushed for time.)

          • sault

            And $1000/lb into LEO is already a considerable reduction in launch costs. What you fail to realize is that most of the launch costs are due to the insane amount of engineering and integration work it takes to design / build the rocket, mount the payload on it, build and staff a launch facility and then actually launch the thing. Fuel costs are inconsequential.

          • Frank_Truth

            If you say so. Everything is relative.

          • Ronald Brakels

            I couldn’t be bothered to work it out properly, but very roughly LOX is going to cost about the same as kerosene, so the fuel cost will be maybe $25 per pound put in orbit or say $60 a kilogram. Since the cheapest launchers cost about $2,500 to put a kilogram of payload in low earth orbit, clearly satellite launching is clearly one of the largest rip-off industries in the world if fuel is the main cost. Or just maybe fuel isn’t actually the main cost.

      • quickstop

        star wars was extremely practical for the time…huge destruction without nuclear fallout or maintenance of nuclear stockpile. smite your enemies without sending toxic clouds over their neighbors your allies or yourself.

        as to the practicality of solar from orbit, depending on the cloud cover that may or may not increase in the decades to come and possible loss in generation from ground based systems, at least having alternative planned out in advance isn’t exactly a bad thing.

        • Brooks Bridges

          I’m respectfully disagree. I was, regretfully in a related business at the time and it was clearly a pipe dream from beginning to end and just a way for “defense” industry to make more money. It needed to be 100% perfect; 99% would mean a large number got through. But the threat that it just might work prolonged that terrible period. If we had taken that money and built 10’s of thousands of schools around the world, we’d have all been a lot safer today.

  • Offgridman

    While this is an interesting idea, like with the space based solar will the costs be worth it for the power generated, and is it needed there or would there need to be a grid to take it where needed.
    Another question is will shade help the glaciers enough. Isn’t increasing ocean temperatures and more rainfall causing as much of their degradation as any actual melting from the sun?

    • sault

      Rising ocean temps chomp at the edges of ice sheets but any sort of shading by high-altitude balloons would mostly slow melting in the interiors of ice sheets. There is a big problem of soot landing on the white ice and lowering its abledo a great deal, leading to a lot of melting. Shading the ice would diminish this effect and could even lead to more snow and ice falling on them compared to rain. I don’t know if shading ice sheets is even feasible, but if it is, it could be one of the more benign tools in our geoengineering toolbox when we discover that even 400ppm CO2 is too dangerous to stay above for long.

    • Hi Offgridman…thanks for your feedback, etc.
      I haven’t done enough calculations yet to know if such an idea is practical or feasible; economically or otherwise. My thinking is mostly to take advantage of more ‘constant’ sun exposure to the solar collectors, by being above the cloud layer of the atmosphere.

      One of today’s biggest challenges in the solar energy industry is to be able to have greatest exposure to the sun’s abundant energy. Weather conditions significantly impact how much solar energy can be generated, when standard roof-top or other ground-based arrays are used. Getting above the weather layer eliminates that challenge, though it is likely some pretty fancy engineering will be needed for this concept to become reality.

      I’m not sure the idea of ‘shading’ the glaciers is feasible either, except that, in theory, blocking out portions of the sun’s rays should have some impact on the temperature of the areas where the rays are being blocked. How to ensure the ‘blockage’ being set up with such ‘mega-balloons’ would remain in the proper strategically crucial position could pose another challenge, but it’s probably doable, y’know?

      Anyway, thanks again…fun to think about some of this stuff.
      Just sayin’…

      • Offgridman

        That’s okay, wasn’t trying to ‘rain on your parade’ (or glacier?) 🙂
        Daydreaming about the possibilities of the future and figuring out new ways of mixing new tech and or old is something that I enjoy doing also.
        Some of my negativity probably comes from concern about addressing the situation we are in now Re: the climate, energy poverty for the majority, pollution, etc.
        Having been producing all of our electricity for about ten years now, in part with old thin film panels that are only about 12% efficient, it has become obvious that weather and seasons aren’t that much of an issue with some planning. So I take quite seriously all of the studies saying we can replace all of our energy needs with current renewable technology in a short period of time with sufficient political and social willingness. So once we are off from the fossil fuel teat and make sure that we are leaving (or living in) a world that isn’t being destroyed for our kids, I look forward to newer ways of doing things, like the satellites or your giant balloons.
        It is just that we need to deal with the situation as it is now and not be waiting for some new tech to fix the mess we have gotten ourselves into, because we can do it if we try.
        Yes new ideas and methods will always come along and they should be used, and experimentation should continue, but for right now I would prefer most of the money go into making sure my kids won’t have to deal with drastic climate change in 25-50 years. Maybe in part because of being old enough to feel that this is our mess to clean up and it shouldn’t be left for the next generation to do.
        So keep on thinking and dreaming, new ideas are important, and let’s hope that we can address the situation as it is now so that your giant balloons are only needed for more regular power generation and not to keep the glaciers from melting away.

        • Heh…thanks again…enjoy your slant, as it mirrors my own somewhat. I’m ‘older’ too, so my hope is that our kids and grandkids have a better, cleaner world.

          Maybe we should tax the fossil-fuel (etc.) industry billionaire investors more so we can afford to pay for cleaning things up, without taking all the funds from the lowly taxpayers, y’know?

          Just sayin’…

          Thanks again.

          • Offgridman

            Your welcome, but it is no problem too, I hang out around this site a lot because in general the news on here is a lot more positive than what is your seen in the regular mass media and thanks to some good moderation and very knowledgeable commentors there is usually a good conversation going on after the different pieces.
            As to the idea of taxing the investors or fossil fuel companies more heavily I personally approve of it, but don’t think it is to likely to happen, and in a way it would just encourage the cycle of trying to get more profits from fossil fuels.
            This came up the other day with companies and people being concerned about extending the production and investment tax credits on renewable energy when actually their costs have come down so far and will do so even more in the future that they aren’t necessary to be competitive.
            I wonder if instead we shouldn’t be pushing for some type of agreement between all countries at the Paris Accord at the end of the year to just stop funding the subsidies for fossil fuels. This would be a savings in the multiple billions for some countries, plus would make the development, production and sales of fossil fuels reflect their actual costs a lot more accurately. So rather than tax all the little people subsidize the fossil companies, and then tax their and the investors profits, just cut it all off right at the beginning. It would save a heck of a lot of paperwork (or computer storage ha ha) and really help to level the playing field amongst the various energy types.
            Of course implementation will be hard especially with the fight the old guard will try to put up, but it is the basic tax and spending reduction that the republicans claim to want so might be possible to get passed in the US after an international agreement if they don’t want to end up looking like total hypocrites.
            Anyways just my take on things, nice talking with you again and have a great weekend.

  • vensonata

    There is a beautiful pdf from Agora Energewiende the German solar plan available on line. It details expected solar prices up to 2050. We are talking about 2 cents kwh! That is impossible to compete with in space tech. ( The only thing which could compete is Nuclear power from the 1950’s which, of course, was too cheap to meter!)

    • Jenny Sommer

      Isn’t nuclear power more like 45-56€c/kWh even for old plants when counting in all the cost (excluding insurance though)?

  • gamma57721

    And it’s all brought to you by the same people who harvested a pile of taxpayers dollars to work on Ronnie Reagan’s Star Wars. Equally irrational. Equally pointless.

    There is no shortage of solar energy down here at the bottom of the gravity well and no shortage of places to install PV modules. As to transmission, would you care to stand in the microwave flux from one of these? Uncle Bob get’s toasted.

  • Ronald Brakels

    We already have satellites in space gathering solar power and beaming it to earth in the form of microwaves, and trust me, they are nowhere near paying for themselves when it comes to providing electricity down here. Currently the microwaves are only used for communication, not power, since that would be crazy. If you want to read about powering satellites, here is an interesting page, although note that power satellites would always be angled at the sun and wouldn’t vary in “solar angle efficiency”:

  • Matt

    This is Northrop Grumman greasing the wheels in the hope they get a cut of this pie in the sky. The transmission issue does NOT go away. You have to build a big receiver and then long transmission wire to town. Since you don’t want that down town baking people. Maybe someday, but this 2100 or so. Think of all the CO2 from the heavy life to get it all in space. Not until we do robotic mining on the moon and use that material, or maybe space elevator.

    • Kevin McKinney

      “Think of all the CO2 from the heavy lift…”

      That’s probably not the biggest potential environmental impact–launches are so much rarer than the ‘normal’ sources of CO2 that the total emissions are dwarfed. (And some rocket fuels–notably liquid oxygen/liquid hydrogen–don’t actually produce any CO2 at all.) But that’s not to say all is good. Here’s a discussion of some of the issues:

  • mike_dyke

    There’s two major concerns I have with these sorts of projects. The first is the getting of the electricity down through the atmosphere to Earth – Will the beams affect the atmosphere as they pass through and hence the weather and the second is what happens if the beam moves from it’s receptor e.g. if a spacecraft/satelite/meteor crashes into the generator?

    As a seperate issue, will putting something that big affect the earth bound telescopes as they won’t be able to see through the generators?

    • Kevin McKinney

      I don’t think that the beams would affect weather; you’d inherently need to use frequencies that have little interaction with atmospheric gases in order to keep your losses low. But solid objects like birds or aircraft passing through the beams would, I think, be a serious issue. And yes, there’d need to be very serious safeties to prevent the beams from ‘wandering.’ They’d have to be fail-safe to a very, very high degree of security, I would think.

      As to the astronomy issue, that really depends on the size of the array deployed (obviously, I guess). The ultimate is the concept of the “Dyson sphere”, in which a sufficiently technologically advanced society could theoretically build a sphere enclosing their entire sun, and collect almost all of its energy output for industrial use. Clearly, all astronomy would then have to take place from outside the sphere!

      But for realistic sizes in the medium term, I doubt it’s a big deal: if my efforts with an online arctan calculator may be trusted (and I’d verify, if I were you–I’m not exactly a math whiz), an array a kilometer across in a sun-synchronous orbit around 700 kilometers up would occupy only about .08 degrees. That’s about 1/6 apparent size of the Sun. And these orbits result in fairly quick apparent motion across the sky, since an orbit takes an hour and a half or so. That means you’d find your object of interest obstructed for only a few seconds.

      Formula for apparent size:

      Arctan calculator:

      • mike_dyke

        Thanks for a detailed reply – I also make it about .08 degrees but it would probably be a square rather than a line…

        On the beaming front, kitchen microwaves can heat up water quite easily, so is there a frequency that won’t?

        I also like dyson spheres (and have read Colin Kapp’s “cageworld” series about them), but solar astronomy would have to be on the inside not outside of the sphere.

        • Kevin McKinney

          “…is there a frequency that won’t?”

          Yes, I’d think so–probably mostly optical, meaning that lasers would be required. (Though I defer to the more spectrally knowledgeable here.) But then you get into clouds blocking them, so it’s not an elegant solution by any means.

          • quickstop

            Terahertz radiation.

          • Kevin McKinney

            Thanks for that–for future readers: “Terahertz radiation occupies a middle ground between microwaves and infrared light waves known as the terahertz gap, where technology for its generation and manipulation is in its infancy. It represents the region in the electromagnetic spectrum where the frequency of electromagnetic radiation becomes too high to be measured digitally via electronic counters, so must be measured by proxy using the properties of wavelength and energy. Similarly, the generation and modulation of coherent electromagnetic signals in this frequency range ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, requiring the development of new devices and techniques.”


          • Kevin McKinney

            Reading further, I find: “Communication:
            Potential uses exist in high-altitude telecommunications, above altitudes where water vapor causes signal absorption: aircraft to satellite, or satellite to satellite.”
            So THR doesn’t solve the cloud issue, perhaps?

      • sault

        The most feasible orbit for a solar power satellite would be geostationary since you’d only need to build one receiver station on the ground and its up-time would ideally be 97% (to account for eclipse season).

        An orbit of 700km altitude would mean that you would need several ground receivers all over the globe and their up-time would be affected by several factors. First of all, at 700km altitude, the solar power satellite would spend about 60 minutes in sunlight and 30 minutes in the shadow of the Earth each orbit. So right off the bat, the system would have a max capacity factor of 66%. Then, the satellite’s ability to beam power to the ground stations would be random and intermittent since these shade / sunlight periods might or might not coincide with the satellite’s overhead passes of the ground receivers. And since scattering and the risk of frying stuff in the path of the beam increases with departure from a 90 degree incidence angle, the windows of opportunity to beam power to the ground receivers would be extremely short anyway.

        • Kevin McKinney

          You are correct. And you didn’t even mention the fact that much of the time satellites would be over oceans. Building a global scale receiving/power grid would clearly be, er, ‘economically ineffective.’

          • sault

            Yeah, the Pacific Ocean alone would reduce the system’s capacity factor by 30 – 40%! And that’s only if small islands like Vanuatu, Fiji and others would build receiver antennas for a scant 10 minutes of energy per day.

        • Radical Ignorant

          Thatis simply worst possible orbit because it’s simply most expensive one. And why can one satellite not transfer energy to other one which is over the receiver at the moment? Adding best ever mirrors to sattelites is still way cheaper than sending them to GEO

  • JamesWimberley

    Entertaining fantasy.
    “.. a network of space-based solar power arrays would provide a steady stream of solar power day and night ..”
    Half the earth is in shadow at any time. Satellites above that half will also be in the Earth’s shadow, with a little leeway at the margins. So space solar stations are not 24-hour. You also need your world-spanning superconducting grid, which other teams of blue-sky types are no doubt also working on.

    • Kevin McKinney

      There are such things as solar-synchronous orbits, which keep the satellite permanently in (or, for some other applications, out of) sunlight. These orbits are currently used for the satellites feeding the familiar (well, to climate wonks, anyway) UAH and RSS satellite temperature sensors–for data homogeneity consistent solar illumination is desirable. So it would be nothing new or exotic to use such orbits for power sats. See:

      • Oil4AsphaltOnly

        solar-synchronous will mean your orbit is out of synch with the power receiving station on the ground, since it will essentially be flying north-south, while the ground station moves east-west.

        geo-synchronous will stay over the same spot on earth (where your power receiving station might be), but will be ~22,000 miles away. That makes the transmission issue even greater than it sounds.

        This is government welfare for the researcher types.

        • Kevin McKinney


          You are right, of course. OTOH, a geosynchronous orbit means much less of a shading problem (as I see James has now pointed out, above.) Yeah, beam dispersal would be a problem… huge power lasers, anyone? Just imagine how welcome that would be on safety grounds!

      • sault

        A solar-synchronous orbit just means that the satellite passes over the same spot on the ground at the same “solar time” (different from “clock time”) every day. They’re useful for imaging, taking intelligence, etc., but have similar problems to low earth orbits for generating power since they are in the shadow of the Earth for about 1/3 of the time. If a satellite was kept permanently out of sunlight, it wouldn’t last long as a satellite.

        • Kevin McKinney

          Doesn’t matter, since the problem with synching to ground stations is fatal anyway. Sigh.

    • Ronald Brakels

      The normal place considered for solar power satellites is geosynchronous (geostationary) orbit. Because it’s 37,800 kilometers away and the earth is tilted statellites there stay out of the earth’s shadow most of the time, but there are still two seven week periods a year where the satellite will be shaded for up to 70 minutes a day. Technically another power satellite could take over during these periods, or every ground receiver could always have several satellites feeding it, but yeah, even if there were no shadow at all, that’s still not going to come close to making this baby economical.

      • Radical Ignorant

        If beaming is no brainer. I don’t believe this piece, but can be wrong. Then what’s the problem with beaming power between satellites? So they always have power. There is another issue. GEO is much more expensive to get things there than LEO. So if beaming is no problem it’s not big deal to create network. One satellite doesn’t have to be connected to particular receiver.

        • Ronald Brakels

          I wouldn’t say beaming is a no brainer, just that we already beam mircrowaves to earth at high cost for communications purposes so we know it can be done. Beaming power directly to the ground should be much easier than from satellite to satellite because of the size of the receivers that would be needed and the loss of efficiency. Trying to supply electricity at midnight to Tokyo using low earth orbit satelites would be very difficult.

          • Radical Ignorant

            “According to the folks over at the Naval Research Laboratory, the transmission of solar generated electricity from space to earth is something of a no-brainer” – from the article.
            And no – no need for sattelites to have receivers, just mirrors with some control mechanism.

          • Ronald Brakels

            The sun is not a point source of light, so unfortunately mirrors aren’t very good at focusing light over long distances. For example, the Znamya space mirror was 20 meters across and from an altitude of 400 kilometers produced a bright spot of reflected sunlight on earth 5 kilometers wide.

          • Radical Ignorant

            Ehmm… I was under impression that we were talking about redirecting beams produced by other sattelites, not sunlight. I was saying that assuming all troubles with creating beams of energy are resolved it’s not big deal to redirect them using other sattelites and deliver where apporopriate. And other sattelite should be quite close to point.

Back to Top ↑