# Space-based solar power? **URL:** \ **Category:** Factual Questions\ **Created:** [March 4, 2009, 9:16pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325 "2009-03-04T21:16:05Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Westrogothia](https://avatars.discourse-cdn.com/v4/letter/w/3ab097/32.png) [@Westrogothia](https://boards.straightdope.com/u/Westrogothia)\ **Post date:** [March 5, 2009, 3:42pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/21 "2009-03-05T15:42:30Z")
> [@jayjay](#): > > And, if it would, what sauce would you serve it with? > > Well, it IS France, after all…sauce is God there. theres a cock au vin joke in here somewhere. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [March 5, 2009, 4:51pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/22 "2009-03-05T16:51:53Z")
> [@Walker\_in\_Eternity](#): > > Although it is unlikely that they would be in sunlight for 24hrs as presumably they would need to be in geostationary orbit over a collector of some kind and therefore would spend the night away from the sun. The geostationary orbit is pretty high (about 22,000 miles) and inclined (to match the tilt of the earth’s rotational axis), so it spends very little time in the earth’s shadow. Most of the year a geostationary satellite is in sunlight 24 hours a day, and during the eclipse season it spends up to 70 minutes a day in the earth’s shadow. And assuming the satellite provides power to the region directly below, the eclipse happens around midnight when power demands are fairly low. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 5, 2009, 5:46pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/23 "2009-03-05T17:46:47Z")
Of course, putting them in higher orbit means that you also have to transmit the power a longer distance, which amplifies many of the problems (your beam has to be better-colimated, your aim has to be more precise, etc.). ---
**Author:** ![wolfstu](https://avatars.discourse-cdn.com/v4/letter/w/d6d6ee/32.png) [@wolfstu](https://boards.straightdope.com/u/wolfstu)\ **Post date:** [March 5, 2009, 6:14pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/24 "2009-03-05T18:14:18Z")
I thought I’d mention that one of my former colleagues in the European Space Agency’s Advanced Concepts Team is [currently working](http://www.esa.int/gsp/ACT/nrg/op/SPS/index.htm) on future concepts for space-based solar power systems. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 5, 2009, 6:25pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/25 "2009-03-05T18:25:17Z")
> [@](#): > > It depends upon what you mean by efficiency. Solar cells have a number of efficiencies. No, it doesn’t. As the rest of your post demonstrates, no one even yet has anything approaching 80% efficiency, no matter how defined. It was an absurdly optimistic prediction to make back in the mid-70s, but possibly that’s what they were hoping would bring in interest and funding. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [March 5, 2009, 6:29pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/26 "2009-03-05T18:29:15Z")
Space based solar power costs too much. > [@http://en.wikipedia.org/wiki/Solar\_panels\_on\_spacecraft](#): > > In 2005 Rigid-Panel Stretched Lens Arrays were producing 7 kW per wing. Solar arrays producing 300 W/kg and 300 W/m² from the sun’s 1366 W/m² energy near the Earth are available. Entech Inc. hopes to develop 100 kW panels by 2010 and 1 MW panels by 2015. [7] For 1 MW we would need at least 3333 kgs worth of panels. GEO launch costs are roughly $20,000/kg so we’d need to spend $66 Million just to get the damn things into space. That of course would only be a baseline value since we have yet to include the transmitter, scaffolding or anything else needed to hold everything together. $66 Million for well less than 1 MW worth of power (due to transmission losses) – but let us be generous and give it a cost of $66,000/kW What about geothermal which has the same advantages (Main costs are upfront, fuel costs are small) > [@US Dept. Of Energy](#): > > What does it cost to develop a geothermal power plant?The initial cost for the field and power plant is around $2500 per installed kW in the U.S., probably $3000 to $5000/kWe for a small (\<1Mwe) power plant. Looks like you could build 13 1MW geothermal plants for the 1 MW solar plant. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 5, 2009, 8:59pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/27 "2009-03-05T20:59:22Z")
Geothermal isn’t the best comparison, since only a few sites are suitable for conventional geothermal technologies (there are developing technologies which work almost anywhere, but I assume those aren’t what the DoE is talking about). You could, though, compare it to Earthbound solar power. Sure, those arrays will be significantly less efficient due to clouds and night and whatnot, and you’d have to pay for the land used, but even so, it costs a heck of a lot to launch anything into orbit. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [March 5, 2009, 9:12pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/28 "2009-03-05T21:12:17Z")
I hear there’s a way to transmit power over distances where the power per area does not decrease as the distance squared. It’s almost as if the power were a scalar rather than a vector… ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [March 5, 2009, 9:19pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/29 "2009-03-05T21:19:09Z")
> [@Ludovic](#): > > I hear there’s a way to transmit power over distances where the power per area does not decrease as the distance squared. It’s almost as if the power were a scalar rather than a vector… If you use laserbeams or microwave beams they spread very little over the distances involved. But can you imagine what a laser or microwave that can process the power output of small power plant would weigh? At something like 20,000 dollars a pound to put into orbit, that adds up fast. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [March 5, 2009, 9:20pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/30 "2009-03-05T21:20:19Z")
Like a 1920s-style Energy Ray… ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 5, 2009, 9:23pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/31 "2009-03-05T21:23:14Z")
Yeah, but they didn’t have orbital launch capability in the 1920s. (someone had to give a punchline, or **Ludovic** ’s head would have exploded) ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [March 5, 2009, 9:28pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/32 "2009-03-05T21:28:00Z")
> [@Chronos](#): > > Geothermal isn’t the best comparison, since only a few sites are suitable for conventional geothermal technologies (there are developing technologies which work almost anywhere, but I assume those aren’t what the DoE is talking about). You could, though, compare it to Earthbound solar power. Sure, those arrays will be significantly less efficient due to clouds and night and whatnot, and you’d have to pay for the land used, but even so, it costs a heck of a lot to launch anything into orbit. True but the point was space based solar would be a waste of money. Why build a single 1 MW plant when you could build 13 1 MW plants down here? And as the DOE site states the cost for plants over 1MW drops allowing potentially a 26:1 ratio to exist. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [March 5, 2009, 9:44pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/33 "2009-03-05T21:44:03Z")
What about these [giant mirror farms](http://boards.straightdope.com/sdmb/showthread.php?t=485131&highlight=solar) we talked about not too long ago? It sounds like we could build a lot of those things dirt-side and we’d get more energy for the money. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [March 5, 2009, 10:55pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/34 "2009-03-05T22:55:38Z")
The whole advantage of space-based is the idea that it is not weather or day/night dependent. The demand for electricity fluctuates, but is very inelastic. We need NOW whatever we demand NOW; there’s no good way to store it. As a result, any power source which is going to provide a meaningful percentage of the total MUST be 100% full time reliable. If we had reliable trans-global grids, we could mitigate the weather & day/night by shipping power from continent to continent. But that too has costs & losses. Space solevs teh day/night weather thing almost completely, and gains some efficiency by getting the collector above the atmosphere. In any engineering or business project there are not black and whites. There are simply plusses & minusses to trade off. Right now space solar doesn’t pass financial muster by a sizable margin. Change your launch costs to $2000/KG and things would be different. One of the driving assumptions of all Space fill-in-the-blank projects is that a large demand for orbital lift will work the usual economic magic of dropping the price dramatically as the volume rises. Which in this case is not out of the question, but is also far from a sure thing either. No one would have predicted 50 mile daily commutes from the suburbs when looking at the primitive cars and mud tracks for roads commonplace in 1910. It’s the rest of the infrastructure that blossomed \*around \*cars which made suburban sprawl not only possible, but readily affordable for hundreds of millions of people. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [March 6, 2009, 2:03am UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/35 "2009-03-06T02:03:18Z")
Mildly on-topic but there was a NASA study on how to turn moondust into a mirrored surface. While it required transporting some substances to the surface of the moon, something like 99% of the building material would be moondust. So an option would be to build mirror farms on the moon that all diverted light to a much smaller number of solar panels. You would need to build at least two farms on opposite sides of the moon right on the edge of the transition from the light into the dark side of the moon. Most of the time you would only have line of sight to one farm, but it would spare you from having to figure out a way to store energy when the collectors couldn’t send power. ---
**Author:** ![Walker\_in\_Eternity](https://avatars.discourse-cdn.com/v4/letter/w/46a35a/32.png) [@Walker\_in\_Eternity](https://boards.straightdope.com/u/Walker_in_Eternity)\ **Post date:** [March 6, 2009, 12:00pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/36 "2009-03-06T12:00:32Z")
> [@CalMeacham](#): > > No, it doesn’t. As the rest of your post demonstrates, no one even yet has anything approaching 80% efficiency, no matter how defined. It was an absurdly optimistic prediction to make back in the mid-70s, but possibly that’s what they were hoping would bring in interest and funding. As far as I know 80% isn’t achievable by any form of solar power, as there are physical limits to what can be achieved. But it depends (for solar cell engineers) which efficiency you are talking about, a cell could be close to 100% efficient at capturing photons, but only convert 10% into useful electricity. I guess you mean overall efficiency, which as I said means that 80% is unlikely to ever be achieved. The limit of efficiency of a single junction solar cell under standard ([AM1.5](http://rredc.nrel.gov/solar/spectra/am1.5/)) conditions is 33%. This can be improved upon by building multilayer cells with different band gaps so that they can capture a wider range of photons. Other methods of improvement include: The use of [hot carriers](http://en.wikipedia.org/wiki/Hot_carrier_injection) so that more than one electron-hole pair is produced by each incoming photon but this can cause device degredation. Cooling, but this uses energy and may offset any increase in efficiency. Surface treatment - anti-reflection coatings to trap photons more efficiently. None of these will bring us anywhere near 80% and that is for silicon or silicon germanium or gallium arsenide devices. Organic solar cells currently work at about 7% efficiency (in the best cases), I don’t know if the upper limit has been determined, but suspect it can’t be much more than a traditional semi-conductor device. ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [August 18, 2022, 11:11pm UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/37 "2022-08-18T23:11:20Z")
> Europe is seriously considering developing space-based solar power to increase its energy independence and reduce greenhouse gas emissions, the leader of the European Space Agency said this week. > > "It will be up to Europe, ESA and its Member States to push the envelope of technology to solve one of the most pressing problems for people on Earth of this generation,"Josef Aschbacher, director general of the space agency, an intergovernmental organization of 22 member states. > > Previously the space agency commissioned studies from consulting groups based in the United Kingdom and Germany to assess the costs and benefits of developing space-based solar power. > **[Europe is seriously considering a major investment in space-based solar power](https://arstechnica.com/science/2022/08/european-space-chief-says-continent-will-lead-in-space-based-solar-power/)** > > Such an initiative would require a 200-fold increase over current space-lift capacity. His twitter comment: > Here are the studies: > **[Cost vs. benefits studies](https://www.esa.int/Enabling_Support/Space_Engineering_Technology/SOLARIS/Cost_vs._benefits_studies)** > > ESA commissioned in early 2022, two independent cost vs. benefits studies of Space Based Solar Power for terrestrial energy needs from Frazer-Nash in the UK and Roland Berger in Germany. Ars Technica posters were overwhelmingly negative. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [August 19, 2022, 1:56am UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/38 "2022-08-19T01:56:20Z")
Thirty or forty years ago, I read several books by [Gerard K. O’Neill](https://en.wikipedia.org/wiki/Gerard_K._O%27Neill), who described how orbital power stations could be built from material mined on the moon. He also described large cylindrical space stations that could house thousands of people. I was fascinated by the ideas. ---
**Author:** ![Horatius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/horatius/32/3572_2.png) [@Horatius](https://boards.straightdope.com/u/Horatius)\ **Post date:** [August 19, 2022, 2:06am UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/39 "2022-08-19T02:06:31Z")
A few years back, I saw a presentation [on DE-STAR satellites](https://www.centauri-dreams.org/2018/10/05/de-star-and-breakthrough-starshot-a-short-history/). Although primarily intended as asteroid defences, they could be re-tasked for sending energy back to Earth. The modular design makes it much easier to start building them, and gradually build up capacity. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [August 19, 2022, 5:41am UTC](https://boards.straightdope.com/t/space-based-solar-power/488325/40 "2022-08-19T05:41:38Z")
For North America, a solar farm system in the southwest could probably feed the power grid a lot cheaper - the difference from 30 years ago when orbital solar power was proposed is that the battery tech is good enough today to smooth out the day-night cycle. certainly cheaper that orbiting thousands of tons of material. Making twice the cells and charging batteries is cheaper than launching solar cells. You can buy a home-sized version of this from Tesla already. For Europe - just put the solar cells in Africa or the Middle East and run the power cables to Italy or via Turkey. As I understood, the power could be beamed to location from orbit using microwaves sufficiently weak that cows could safely graze under the antenna farm - just the antennas would be spaced every few yards apart within the area of a 10-mile circle. [Previous page](https://boards.straightdope.com/t/space-based-solar-power/488325.md?page=1) [Next page](https://boards.straightdope.com/t/space-based-solar-power/488325.md?page=3)