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Electricity from Space: The 1970s DOE/NASA Solar Power Satellite Studies
- mhandley 3y agoHas anyone updated the economic feasibility studies based on using SpaceX's Starship as the heavy-lift reusable launcher? At first glance, it seems like this, combined with today's greatly improved robotics and ion thrusters to move components from LEO to GEO, may be the key enablers.
- simonh 3y agoMusk is on record saying it's a complete non-starter. There are all sorts of problems with it. Beam spreading is a huge problem, the ground receiver would generally have to be about 10x the diameter of the transmitter and these would need to be really big arrays. A 1km transmitter is ballpark. Targeting the receiver is tricky as even minuscule angular offsets mean you would miss completely. Losses from transmission and reception are huge, and the enormous emissions leakage means you have to clear the big chunk of orbital 'real estate' of other satellites or they'd suffer serious problems.
- dexterdog 3y agoIf he says it can't be done either it really is seriously unrealistic, or somebody else already has a lead on him.
- xbmcuser 3y agoHe has the cheapest way to get to space locked in for a few years so if he says it is not feasible than it probably is not feasible. Looking at how ground solar and battery prices are still falling 10-15% a year I think it will be hard for space solar to be economically viable let alone viable when you take it into account pollution.
- ben_w 3y agoOnly 1km? Given the usual claims I hear about power density and total power, it's normally 100km^2, or square 10km on the side.
- simonh 3y agoFor the receiver yes that's ballpark. I'm talking about the size of the microwave transmitter array in orbit beaming power down to the surface.
- ben_w 3y agoAh! I misread. Thanks :)
- mikepurvis 3y agoThat's pretty sobering, since you can produce/capture quite a lot of energy with 100km^2 of clear, flat ground that has a view of the sky. Not least by just putting normal solar panels on it and jettisoning the whole space part.
- DennisP 3y agoYes but with SPS, that 100km^2 is mostly just antenna wire, and you don't need any sort of energy storage.
- ben_w 3y agoAt 6cm spacing, a 10km by 10km ground array with 1mm^2 cross section wires has total 1667 m^3 volume; this is as much conductor as you would get in the equivalent of a 1111 km long 1 GW HVDC cable: https://www.wolframalpha.com/input?i=10km*10km%2F6cm*1mm%5E2%2F1500mm%5E2 https://www.wolframalpha.com/input?i=10km*10km%2F6cm*1mm%5E2... It's not exactly the same thing, of course, but it means 40 such ground stations would use as much metal as a 1 GW line looping all the way around the planet and back to itself, and a global grid is another way to obviate storage. That's 1 GW with standard existing cables; I assume if you actually want to go that far one can improve the design as the optimisation goals are different. Parallel cables lower resistance. I'm also not sure how much maximum current would scale in such cases.
- DennisP 3y agoPeople sure put a lot of weight on an off-the-cuff comment Musk made in 2012, before Starship was even a gleam in his eye. That was the same year NASA published their SPS-ALPHA study[1] on modern SPS design, so Musk may not have been aware of it. Modern designs use a phased-array transmitter, and a reference signal from the ground for targeting. Overall energy loss is 40 to 60% according to the book The Case for Space Solar Power. [1] https://www.nasa.gov/pdf/716070main_Mankins_2011_PhI_SPS_Alpha.pdf https://www.nasa.gov/pdf/716070main_Mankins_2011_PhI_SPS_Alp...
- ben_w 3y ago60% loss is also what you would get with a single 1GW existing HVDC cable, connecting anywhere on Earth to its antipode. IIRC, for n identical parallel resistors of rΩ, Σ = nrΩ, so this only gets better for bigger systems.
- giantrobot 3y agoElon Musk's most fantastic/unrealistic prediction for Starship cost to orbit is $10/kg. To get to GEO roughly doubles that cost because the cargo Starship needs to rendezvous with a tanker for the fuel to GEO then back home. Intermodal surface freight reaching most of the planet is about $1/kg on the high end. To even begin to make sense, space freight to would need to be 1/10th of Musk's overly optimistic $10/kg. You could ship the panels air freight and still beat those numbers by a huge margin. That says nothing of the construction costs. Which for SBS will cost orders of magnitude more than day laborers in t-shirts assembling arrays on the ground. Every aspect of SBS is ridiculously expensive and requires as-yet entirely undeveloped space-based construction technologies. There's no near-term horizon where it's anywhere close to competitive with ground-based solar. This holds even if you assume over-building surface solar to 3x to match the duty cycle of SBS.
- DennisP 3y agoYou don't have to get to surface freight numbers to make SPS viable, because SPS has advantages that compensate for the higher transport cost. Those include a 99.5% capacity factor, a 5X higher solar flux per panel over 24 hours, and much lighter construction due to the lack of weather and gravity. As for construction cost, NASA's design would self-assemble in orbit. I linked the full study report.
- jackmott 3y ago[dead]
- ZeroGravitas 3y agoIt's probably the lower cost of earthbound solar and batteries that are the bigger factor in updating the feasability, trending in the opposite direction.
- deleted 3y ago[deleted]
- T-A 3y agoThere has been a surge of interest over the past year: https://spacenews.com/nasa-to-reexamine-space-based-solar-power/ https://spacenews.com/nasa-to-reexamine-space-based-solar-po... https://www.esa.int/Enabling_Support/Space_Engineering_Technology/SOLARIS/SBSP_overview https://www.esa.int/Enabling_Support/Space_Engineering_Techn... https://spaceenergyinitiative.org.uk/ https://spaceenergyinitiative.org.uk/ https://www.spacesolar.co.uk/ https://www.spacesolar.co.uk/ https://www.solarspacetechnologies.com.au/ https://www.solarspacetechnologies.com.au/ Here's a nice recent summary (despite the publication date): https://aerospaceamerica.aiaa.org/features/harvesting-sunlight-in-space/ https://aerospaceamerica.aiaa.org/features/harvesting-sunlig...
- milliams 3y ago*[2016]
- fourseventy 3y agoThis idea never made any sense to me. Why the heck would you spend billions of dollars to launch solar panels into space to gather sunlight then beam it to earth when you could just wait for the sunlight to get to earth naturally for free...
- nine_k 3y agoThe fact that a powerful microwave beam shooting precisely from the orbit is also a weapon platform (if directed outside the receiver) might have played some role.
- MrOwnPut 3y agoA real-life Hammer of Dawn (gears of war) Really though I don't see this scaling to energy production for the masses due to the beaming logistics. It'll mainly be used to recharge drones that never land and possibly fry enemy systems / missiles / etc.
- DennisP 3y agoNot with a satellite in geostationary. The beam concentration on the ground would be too low to hurt anyone. You'd need a collector miles wide. With modern modular designs using phased array transmitters, even getting that much focus requires a reference signal from the ground target.
- kybernetikos 3y agoPutting the cells in orbit means that there's almost no night, and there's less loss due to the atmosphere. Of course, there are loads of problems with the idea but I can see why it's intuitively appealing.
- jackmott 3y agothere is loss from the atmosphere when you beam it down
- 3y ago
- cosgrove 3y agoI think it's neat that they did all these studies on feasibility and projected a start date into the 2000s. Also neat that we ended up with complimentary energy generation and storage technologies to fix the "it gets dark at night" problem of solar electricity generation!
- blincoln 3y agoThe article mentions that limited agriculture could be conducted at the rectenna sites. I wonder if it could have actually been beneficial. A lot of middle America (where most of the sites would have been located) gets VERY cold in the winter. Would microwave warming of the rectenna sites allow growing more crops there for more of the year?
- ben_w 3y agoYes, but a thin sheet of plastic over the farmland also massively boosts output in similar cases, and there are more issues than just temperature: https://en.wikipedia.org/wiki/Polytunnel https://en.wikipedia.org/wiki/Polytunnel
- cduzz 3y agoEven things like electricity and water, which move pretty well, have "place value" -- people commonly move water from place to place by growing grain with the water and then moving the grain (not the water) to places that don't have enough water to grow the grain conveniently / economically. The same goes for electricity -- Iceland exports refined metals which require huge amounts of electricity to melt, effectively exporting the electricity entombed in the refined aluminum. What can be made in space that can allow moving this abundant energy? Obviously you can't haul ore up into space then refine it with a big magnifying glass and drop it back onto the earth. People talk about asteroids but they seem like they're a big delta-V away from where they'd be useful to put into Kia bumpers.
- simonh 3y agoIf you need extensive industrial infrastructure in orbit, maybe make that from resources mined from asteroids. Ship high value finished goods down from orbit.
- GravitasFailure 3y agoHow much of that high value stuff will wind up in satellites? Cut the trip down the gravity well and just build in orbit, especially low value items that are expensive to launch but cheap to make.
- TrapLord_Rhodo 3y agoread the delta-v series. Great book, and that's exactly what they do.
- amitu 3y agoComputation.
- jackmott42 3y agoThat is a good point! GPT5 in space, beam down the model, not the energy.
- DennisP 3y agoNASA completed another study in 2012, with a vastly cheaper and more practical design enabled by new technologies. Here's a description: https://space.nss.org/sps-alpha-a-novel-approach-to-space-solar-power/ https://space.nss.org/sps-alpha-a-novel-approach-to-space-so... and the study itself: https://www.nasa.gov/directorates/spacetech/niac/2011_Practical_Solar_Power_Satellite/ https://www.nasa.gov/directorates/spacetech/niac/2011_Practi... A book-length treatment of modern SPS designs is The Case for Space Solar Power. It has detailed cost figures but was written before SpaceX had accomplished much, estimating a cost at gigawatt scale of 15 cents/kWh. I plugged in Starship launch costs and it came to 4 cents/kWh, which is not bad for 24/7 clean power without storage.
- bradfa 3y agoAny discussion on how much shooting giant microwave beams through the atmosphere would warm the atmosphere locally or globally? Clearly the beam won't be 100% efficient and that power loss is going to partly be absorbed by the atmosphere, causing it to warm.
- DennisP 3y agoThere's also waste heat from nuclear power and fossil plants. There's even some warming from the lower albedo of black solar panels. All of it is a tiny effect compared to the warming from greenhouse gases.
- JKCalhoun 3y agoI loved concept art (like the NASA/Boeing illustrations that accompany this article) until the artists started to go digital/CG in the 80's or whenever it was. I'm not a huge fan of the artist(s) depicting space concepts in this particular article though (still better than most rendered art). I tried to do a bit of googling to find something better but in 10 minutes the best I could come up with was this site: https://www.kuriositas.com/2013/08/space-shuttle-concept-art-of-1960s-and.html https://www.kuriositas.com/2013/08/space-shuttle-concept-art... I think there was more dynamism in the pre-CG concept art, often a bold use of color, sometimes an exaggerated use of shadow/light.
- euroderf 3y agoI feel the need to namedrop Charles Bonestell.
- nirav72 3y agoI just got done reading Critical Mass by Daniel Suarez. The technology described and used in near future story of the book is based around this concept. Except in the book, they use it to power mass drivers to shoot cylinders of lunar regolith to a Lissajous orbit where it can be processed into raw materials.
- bglusman 3y agoCame here to say the same! Though it's a bit fun that when they upgrade the moon to use a nuclear reactor to power several mass drivers, they mention how the satellite can be repurposed to provide power to earth now... which makes sense. The book (and its part 1 book, Delta-V) overall point about the value and utility of asteroid and lunar mining to bootstrap whole economies around the Lagrange points and that sending that matter back down to earth makes very little sense was pretty compelling, and relatedly that building a colony on Mars probably makes very little sense vs building in space with artificial gravity and artificial radiation shielding, where you're not subject to a giant gravity well to go back to earth/elsewhere in solar system.
- timthorn 3y agoFor those in the Cambridge area (or who have Zoom!), there will be a CSAR talk on Monday evening about the CASSIOPeiA Solar Power Satellite: https://www.csar.org.uk/lectures/2022-2023/20230501/ https://www.csar.org.uk/lectures/2022-2023/20230501/
- gene-h 3y agoOne problem with this that wasn't as much of a problem in the 1970s is RF interference. The 1970s designs and many other designs use 2.45 GHz, so it will interfere with wifi and bluetooth, with bluetooth being more sensitive to interference. How far does this interference extend? Thousands of kilometers from the receiver[0, see page 250]. Because the transmitter is far, the beam spreads out quite a bit due to diffraction and because the transmit power is gigawatts there's hundreds of megawatts of stray power. Making bluetooth headphones and bluetooth low energy tags work worse will probably make people angry. Different frequencies could be used, but that requires allocating spectrum, which is a pretty difficult task politically. In the US, there are a couple bands in the sub-10 GHz range where power beaming works best that have few users. So it's not impossible, but still politically difficult. [0]https://ieeexplore.ieee.org/document/9318744 https://ieeexplore.ieee.org/document/9318744
- mlyle 3y agoThis is a really good point. I know super narrow notch filters up in the gigahertz are difficult, but has anyone thought at all about how narrowband the power transmission could reasonably be? Because then at least notching would be possible to squeeze out adjacent spectrum.
- techdragon 3y agoThere are techniques. And generally speaking the bandwidth can be much narrower than the sort of things designed back then. Even a lot of modern systems are designed with less than state of the art tech for various reasons… reliability, cost, etc.
- mNovak 3y agoI bet the military would love/hate it (depending where deployed), because all that stray illumination would make for a perfect bistatic radar source. Suddenly many radars can be passive, and stealth techniques take a serious hit.
- wbl 3y ago
- mrguyorama 3y agoThis was an energy generation option in Sim City 2000 with the caveat that occasionally the ray of microwave energy would "miss" and cook some of your city.
- michael1999 3y agoGigawatt steerable carefully de-focused energy beam. That's a doomsday machine.
- DennisP 3y agoExcept there'd be no way to focus it enough to hurt anything.
- nickpeterson 3y agoDumb question but what about mirrors? Couldn’t we redirect sunlight to a fixed point on earth that has solar panels?
- biomcgary 3y agoI like the idea, but there are a few questions I have for the plausibility of this approach. 1. Does mylar (or weight equivalent have enough reflectivity and flatness) to target a ground station? 2. How much light can be concentrated before becoming a risk (e.g., birds above solar panels, human eyes in vicinity)? 3. How fast will the mirror material degrade from solar wind and micrometeorites? I assume someone has considered this scenario previously, but I imagine that SpaceX lift capacity and price might change the economics.
- Cthulhu_ 3y agoSolar panels drop efficiency the warmer they get; focusing more sunlight on a space will heat that up. There's solar heat based power stations, using mirrors that focus light on a point or a pipe to heat up oil; the question there is, would they become more effective if they get more light? 1 square meter of ground currently receives 1370 watts of energy (if my quick google is accurate); if this can be captured, you can do a back of the napkin calculation of how much you need. It's already been posited that filling a relatively small patch of e.g. a desert can fulfil all of europe's energy needs - no space things needed.
- TrainedMonkey 3y agoPossible but highly inefficient for power generation. Need massive amount of mirrors with pointing + stationkeeping. For medium orbits will need a huge amount of receiver sites + beefy prop & pointing systems. For Geo will need a truly staggering amount of mirrors + sophisticated focusing + massive receiver sites on the planet. Anywhere you point the beam will have massive ecology / weather disruptions... Probably not suitable for human habitation in a huge area due to atmosphere dispersing the beam. See https://en.wikipedia.org/wiki/Space_mirror_(climate_engineering) https://en.wikipedia.org/wiki/Space_mirror_(climate_engineer... for more info. One cool thing we could do is slightly boost the amount of sunlight northern latitude cities receive. This will make solar panels there more viable and will make cities far more livable in the winter season. This could also be done seasonally. This is a cool example https://www.theguardian.com/world/2013/nov/06/rjukan-sun-norway-town-mirrors https://www.theguardian.com/world/2013/nov/06/rjukan-sun-nor...
- usefulcat 3y ago".. President James Carter .." Weird, that's the first time in my life I've ever heard him referred to as 'James' rather than 'Jimmy'.
- dragonwriter 3y agoI've seen James a fair amount, but almost never without also having “Earl” and “Jr.”