31 thoughts on “Space Solar Power”

  1. I was watching a TV show yesterday which showed some of the massive highway building program in China, and thinking ‘just imagine where the West would be if we didn’t have to waste ten years on environmental assessments before we built stuff’.

    Yet we get lefties here talking about how wonderful China is because they do all this stuff… while pushing the very regulations that prevent us from doing it.

  2. The economics of space solar was studied in depth in the 1980’s and the case came up extremely lacking. Of course that was with 1980’s rocket technology. Another review might be in order given BFR/BFS or it’s equivalent. I’d be interested in the results.

    1. Technology has advanced across many fronts since the 1980s, with launch costs being just one. Launching an SPS into LEO or GTO and use electric propulsion to take it to GEO wasn’t an option back then. Solar cells today are much more efficient. Modern materials allow for lower structural weight. Modern electronics are more powerful and efficient. I agree with you that someone needs to do an analysis using today’s technology, and also projecting new launch technology that’s on the near term horizon. Those 1980s numbers are way out of date.

      1. If I remember correctly, O’Neill and co weren’t planning to use solar cells in the 70s, they wanted to use mirrors to focus the light on boilers and generate electricity the traditional way with steam (or some other working fluid better suited to space use).

        1. I believe that is also the strategy Colonel Smith was proposing on his SpaceSolarPower blog. It makes sense, as the mirrors can be arbitrarily large, perhaps aluminized Mylar. The drawback is that there is a moving part (the turbine) that would require periodic maintenance. However, if the cold trap is the blackness of space in the shade of the collector, then the hot side only needs to be above 300 Kelvin for the Carnot efficiency to exceed 99%. Even losing half to friction in the turbine and working fluid going through the pipes, plus transmission losses, that’s still way better efficiency than is possible on the ground (IIRC the best solar thermal efficiency so far was 32%, by Sandia labs in New Mexico on a very cold January day about 14 or 15 years ago).

  4. For SPS you have to launch cost.
    But you can ignore launch costs. One spend a lot money and get electrical power from space.
    For a country that makes Ghost cities, it could be improvement.
    But I tend to think, SPS are about 50 years in the future. And it require lunar mining and perhaps Mars settlements.
    And that first requires lunar exploration.
    Or if continue not exploring the Moon, it will require more than 50 years.

  5. I was struck by the plan to launch prototypes into the stratosphere, with no mention of how to keep them there.

    If this Chinese plan is in any way real, I suspect its method for transmitting power to Earth will be high-energy lasers. And it won’t be for electricity generation – that’s just a cover.

    2. My guess was that it was referring to representative systems launched on balloons for testing purposes prior to committing to full-up space systems. But I’m just spit-balling here.

  7. When PV cells were expensive, it may have made sense to put them in space, to get the most out of them.

    But they’ve become quite cheap now. Just build more on the ground. You may need to transmit the energy in time rather than in space, but at the efficiency of microwave transmission there should be many options, including possibly just storing the energy thermally.

    If the Chinese are serious about space solar, rather than serious about making slides, I expect they’d look at laser transmission rather than microwaves.

    1. OTOH, more efficient panels mean you need less of them to generate the same power in orbit. And no cloud cover(or even nighttime in GEO) means they’re running near 100% capacity all the time so again you need less of them. So without redoing the analysis with current launch costs and current efficiency we don’t know which is better. IMHO major downside is orbital power stations could become a fat target in wartime.

  8. I like the integrated module idea. Solar cell one side, microwave emitter the other and the capability to electronically steer the beam.
    This should mass a lot less than any other method. Maybe the Moon miners and mass drivers, catchers etc won’t be needed. Starship and Booster will likely also change the economics. I’d still back this over ground based solar any day. At least solar panels in space don’t get dust and dirt on them. Ground based solar was lots of other problems than expense. Area of land used, dirt, hail, expensive and heavy construction to stand up to the rigors of terrestrial use and unavailability guaranteed for an average of 12 hours out of 24 plus reduced output on cloudy days. Nuts.

    1. Solar cells have to stay pointed at the sun to work. At GEO, solar panels rotate through 360 degrees per day. You’d have a hard time keeping the antenna pointed at the ground if it’s on the other side of your solar cells. Even phased array antennas typically can’t aim a beam more than 60-70 degrees off boarsight.

      I think a modular approach would work but not necessarily how you describe it. Create a solar power module as large as would fit in your largest available booster. You could launch it into LEO or more likely a low GTO then use electric propulsion to boost it to GEO. Once there, it could either be colocated with earlier modules or perhaps dock them together.

  9. I say build the power plants on the Moon. The resources exist on the Moon, and you don’t have to launch the resources. I think Jeff Bezos has enough money to build lunar solar power. What he should do next, is to buy stock in a few electric companies. Then using his money, the power companies money, build LSP. He could build it on the Moon’s north pole, and then beam the power to relay satellites in Earth orbit.
    Then beam that power to Earth.

    1. The Earth rotates, so a lunar based system couldn’t keep the beams aimed at the ground-based rectennas most of the time. A GEO based system would be in sunlight about 99% of the time, would always be in sight of the ground station, and would have lower link losses.

    2. The Moon needs reliable power a lot more than Earth does. Do what you say, but for lunar consumption. Forget the bank shot to Earth.

      1. I agree with this. I’m not a fan of these things for Earth. I may question AGW, but there would be no question that a functioning solar collector in space, collecting power and then transmitting it to Earth, is adding energy into an otherwise closed system. I’m not sure that is a good idea. Before we scale such a system for Earth; how about trying it on the moon, where we can study the efficiency of the system (the moon has no atmosphere either), and provide power where other natural resources are limited.

    3. “I say build the power plants on the Moon. The resources exist on the Moon, and you don’t have to launch the resources. I think Jeff Bezos has enough money to build lunar solar power. What he should do next, is to buy stock in a few electric companies. Then using his money, the power companies money, build LSP. He could build it on the Moon’s north pole, and then beam the power to relay satellites in Earth orbit.
      Then beam that power to Earth.”

      It seems hard part is getting lunar electrical power for $1 per kw hour.
      It seems that 10,000 tons of water is worth $500 per kg or 1/2 million per ton or 5 billion for 10,000 tons [if don’t have to buy it when not available to use- though could buy say 100 tons in regards to contract prior to delivery of whenever you want it].

      And it seems if could buy enough electrical power, to convert water into rocket fuel at $50 per Kw hour, that would likewise be good price to pay.

      But if you could buy electrical power at less than $.5 per kw hour and buy lunar rocket fuel for $5 per kg, then cost to make solar panels and cost to ship them to GEO from the lunar surface would quite cheap. At polar poles one might get +80% of time getting solar energy, with GEO it’s +95% of the time. And you closer to Earth and have more square km of area to harvest solar energy.
      Or in terms providing energy to Earth, the moon has small area in which one get more than 50% of time getting solar energy.

      And if have 1000+ people living on Mars, they might willing to pay more $1 per kw hour of electrical power beamed to them from SPS in Mars orbit. And cost sending payload to Mars orbit is about same as sending to Earth GEO.

  11. My problem with space-based power has always been that, while I believe you can make such systems fail-safe against accidents, I do not believe they can be made fail-safe against intentional misdirection of whatever method you are using to beam the energy down to Earth. This would be a powerful instrument of terror or war, well insulated from counter-attack.

    Yes. Death rays.

    1. You’d have to choose a microwave frequency that doesn’t interact with water, N2, O2, or CO2. That leaves a broad range of frequencies that wouldn’t be absorbed by the atmosphere, and couldn’t be used as a death ray.

    2. As with chemicals, the dose makes the poison. You can walk around out in the sun for quite some time before suffering any injury. However, if you use a magnifying glass, you can focus the sun’s rays tight enough to cause a serious burn in seconds.
      A power satellite microwave downlink would be spread over a considerable area. The tightest antenna beamwidth I’ve ever seen was 0.1 degree. That was on a 60 foot diameter satellite control dish antenna designed to work with deep space satellites. If it were possible to achieve that same 0.1 degree beamwidth on a GEO satellite, the spot beam would have a radius of almost 40 miles even if it were directly overhead. That spot would have an area of more than 4,700 square miles. At that area, a 1 gigawatt downlink would have an energy density of about 200,000 watts per square mile. That’s far less than the energy density from the sun (~1000 watts per square meter).

      1. It seems to me you launch a 120′ dish antenna from the Moon and not have the gee force exceeding 1/2 gee, therefore not needing to be as strong as dish antenna on Earth, having a constant 1 gee, and being able to withstand some wind.

        And if 120′ how much does that reduce it’s footprint?

  12. I don’t have the URL but I’ve seen a design for an integrated solar cell/microwave emitter SPS that did not have the pointing problems referred to.
    The guy also convincingly showed that any non integrated design had huge problems resulting in high mass and complexity.

  13. China should just focus on it’s under ground coal fires that have been raging for centuries..

    “They are monstrous, centuries-old infernos that issue thick billows of ash and smoke, and generate sinkholes that consume roads and homes without warning. Yet in spite of the dangers they pose, underground coal fires are some of the least known environmental disasters. China, the world’s largest miner and consumer of coal, has consistently downplayed the fires in its coalfields, considered the most severe on earth.”

    https://www.chinadialogue.net/article/show/single/en/6296-The-world-s-longest-burning-fires-China-s-unseen-story

    1. Unfortunately that would not be easy. If it was they would have done it already. I think the USSR managed to put down a similar fire once but they basically snuffed out the oxygen with nuclear explosions. I just don’t see anyone approving something like that right now.

  14. I doubt it will happen over the next decades. This sounds like a test balloon for what else they could use their heavy launchers for once they finish their Mir-like space station.

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