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.
Even 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.
I think bottom line is that resource utilization from space on earth makes zero sense. Space resources utilized in space makes perfect sense but there’s the chicken and egg problem. Bezos focus on space colonies fits this agenda. Musk mars colonization focus does as well due to mars low gravity.
Imagine a really large lifting body, made of interlocked containers, building a honeycomb-like superstructure. Put some ablation layers around it. Maybe some small remote controlled rockets for steering. Let it glide down into the ocean near the coasts. Pull it into the the harbour via tug-boat. Remove remaining ablation layers. Disassemble honeycombed superstructure. Open containers. Get packets out. Melt containers into something else, or put them back up via space elevator, or whatever.
For the most part I believe you're correct, but certain goods do have a sufficiently high value density that space manufacturing might make sense, especially in cases (like I highlighted above) that benefit specifically from microgravity. What will probably make more sense is taking advantage of microgravity for research, then adapting what we learn to manufacturing planetside.
There's probably a whole world of manufacturing processes that benefit from low gravity. The only one currently used is making high-quality optical fiber: producing ZBLAN fibers in 0g fixes a lot of problems with bubbles and crystal formation, allowing you to make better and much longer fibers. As access to space continues to get cheaper we will probably discover a lot of other cases where 0g is beneficial for manufacturing, and entombing energy might be another way to make those economically interesting.
Moon bricks. Ship regolith and dust into orbit from the moon, mix with water to make a moldable clay, form into bricks, bake inside the mother of all solar kilns and then drop them down on Earth. The water should be recoverable if the kiln is air tight. This would greatly reduce fuel needed on earth for construction. You could even make the reentry vehicle out of baked clay, only parachutes would need to be added. Extra points if you can make the whole thing buoyant and land them in the ocean.
George Crabtree et al from Argonne national lab are working on an automated chemistry lab that synthesizes and tests various flow battery chemicals on its own. Of course simulation and AI are used too but it's not enough. There are a lot of alternatives and a lot of different requirements / dimensions.
Very fascinating video: https://youtu.be/yv_8xfwsKxE?t=1208
If you need extensive industrial infrastructure in orbit, maybe make that from resources mined from asteroids. Ship high value finished goods down from orbit.
How 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.
Any use of energy in space is going to have pretty big cooling problems unless it's a fundamentally "hot" process that radiates away heat easily. Because any usage of energy in space all becomes heat.
Solvable with a large enough thermal mass. And once we're able to start mining the moon or asteroids for mass to be cheap enough, heat would no longer be a problem in space: use conduction and convection to move heat away quickly, have a holding area for hot matter for radiative cooling to do its thing, then keep adding additional mass until equilibrium temperature of the system is below requirements
> have a holding area for hot matter for radiative cooling to do its thing
The implication of course is that surface area can be increased trivially by adding matter. And with a larger thermal mass, more energy will be required to heat the system to the same temperature, giving more slack in the system for radiative cooling to work.
So largely I believe the plan is to use microwaves to send the power back to earth so you don't have to have anything processed in space. This would usually involve ground stations that would receive the power.
Right -- microwaving the ground is just moving the energy, which may or may not actually be efficient. On the face of it it seems silly, but so does making a rocket out of water towers and landing it on it's ass on the moon, so I've re-calibrated 'silly'.
Nevertheless -- finding ways to move refined products around that embody a huge amount of energy is the traditional way to approach this problem.
And anti-matter, if you could package it, is an obvious example....
The book Critical Mass by Daniel Suarez is my only source, but, the efficiency of rectenna is discussed there, and particularly, though the efficiency of the transmission is somewhat low, the efficiency of solar panels in space is MUCH higher than on earth, and they can operate 24/7, so the overall system efficiency is still substantially higher than the equivalent solar panels on earth... at least, assuming you can build the solar panels in space from mined material as they do in the book, I imagine if you needed to launch all the material from earth, it would probably be a fairly different story, assuming you included that in the calculations.
> the efficiency of solar panels in space is MUCH higher than on earth
Not really. The biggest difference between a panel on Earth and one in space is the space panel is illuminated 23 hours a day. So per panel you're getting 2-3x the illumination over the course of the day.
The drawback is even at the absolute cheapest pie in the sky Musk estimates of cost to orbit ($10/kg), a space solar panel is orders of magnitude more expensive than a ground panel. You could just deploy 3x the number of panels on Earth for 3x the price vs deploying in space at x\^3 the price.
Even with the near constant illumination of panels in space the losses from RF conversion, free space losses, atmospheric losses, and RF rectification eliminate a lot of your power gains. For those losses you also incur significant costs. So SBS is kind of a lose-lose problem. Every technology that would make SBS more practical could be applied on the ground for a tiny fraction of the cost.
>The biggest difference between a panel on Earth and one in space is the space panel is illuminated 23 hours a day
Small nitpick, but as a GEO satellite navigator I want to point out that the solar panels are in sunlight constantly except for "eclipse season" around the equinoxes. During eclipse season it can be in shadow for about an hour.
Only if ignoring all externalities. If the panels could be manufactured in space, or on the moon, via some ultrasmall in-situ-utilizer bootstrap gizmothingy, which would then use material from the moon, or asteroids, we'd save much mining and manufacturing here on earth. Which has its own costs. As we all should know, meanwhile?
Yeah with space it is typically more efficient to move energy versus mass. The efficiency may not be great but you get to balance it with the increased efficiency of solar panels being located in space. So independent component efficiencies might be overshadowed by large end to end system efficiency gains.
It’s not efficient for replacing power sources on the ground, but for airplanes, ships, and remote communities it could be genius. No need to carry heavy batteries around and your capacity is virtually unlimited (At least as far as it is feasible to build a massive orbital solar array).
Why isn't it efficient for replacing ground based power sources? In the case of replacing ground based solar, it means not having to deal with intermittency and diplacement of natural habitats. In the case of hydrocarbon-based power plants, it means not having to contend with pollution.
One 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.
I 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.
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.
There 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.
I 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...
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.
This 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...
Yeah, no night, no atmosphere, constant power output, lot's of real estate, and panels in space do not need heavy superstructure to withstand weather or gravity, thus they could potentially be extremely light for the area (micrometers to tens of micrometers thick at most needed for light absorption). And in far future, if they are built of materials taken from moon or meteorites, you could also bypass most of the lifting cost for even that. Of course, that would need huge scale to justify the R&D to pull it off.
Anyway, space based solar power is the end game. Nothing on earth will ever provide the quantities of power (not even nuclear, fusion or fission) that capturing solar energy can.
Worth noting this isn't as much of a benefit as it's made out to be.
If you were designing a perfect power source, it would match demand, so produce more in winter in polar regions, and more in summer for regions with lots of AC. Similarly, you'd generally want more power during the day than at night.
This is part of the reason a mix of solar and wind that varies by latitude is an ideal mix.
Space power might get more bang for buck if it could target its power to different regions e.g. swapping from north to south as the seasons change, and/or following the day/night cycle and/or weather to maximise energy price.
The satellites would be in geostationary, with phased-array transmitters, focused by a reference signal from the ground target. They actually could be repointed to various receivers. The ground stations would be relatively cheap so it wouldn't be all that important to maximize their utilization.
> They could potentially be extremely light for the area (micrometers to tens of micrometers thick at most needed for light absorption).
This is really the key, if you can make a solar panel that’s as light and thin as say mylar, and then unfold it when you get to space, we could put up several kilometers of solar panels without requiring much mass at all. It’s not like there’s wind or rain up there to wear it down.
No night? Where are you putting these satellites? The only orbit that doesn't eclipse is sun synchronous, an already crowded orbit. Even GEO satellites experience eclipse.
> Glaser had noticed that a satellite in geosynchronous Earth orbit (GEO), 35,786 kilometers above the equator, would pass through Earth's shadow for only a few minutes each year.
The article addresses this. To my mind 4 minutes per year is equivalent to the parent’s layspeak “no night” comment.
4 minutes??? Not even close. Each eclipse varies from a few seconds for the first one to practically an hour in the middle, then gets shorter again, over roughly 30 eclipses each season (2 per year)
So, let's cut down the pedantry a bit. Even in the most pessimal reasonable orbits, up to an hour of outage in the middle of the night for 3-4 months per year is a very different beast from getting just several hours of sun per day.
Why?
- You still get better duty cycle from the panels
- The time the power is missing is very small
- The need for storage, etc, is low because it's a short period of relatively low demand that is missing.
They address this in the article: Only twice per year are the panels in shadow, at the equinoxes. Presumably all the rest of the time they're slightly above/below the earth with respect to its orbit. It's the same reason the moon is lit nearly all the time.
Respectfully, I believe you are inaccurate on both accounts, sun synchronous orbits (SSO) only have no eclipse if their orbital plane is within a very degrees of the terminator, this of course widens with altitude but there exists far more possible SSOs with eclipses than without.
Secondly with GEOs as with any very high altitude orbit the eclipse time trends towards zero so effectively at a GEO the eclipse time is minimal compared to the illuminated time. Of note the length for the eclipse time of GEO varies throughout the year.
Respectfully, you are not correct that eclipse in Geo is insignificant. It drives many engineering constraints for spacecraft systems. Look I get why people are excited about space space solar power, but I've been in this industry for 15 years and when you dig into the numbers and understand the realities of spacecraft engineering, SBSP just seems like a fool's errand. It may not always be that way, but the technical challenges are extreme and costs are still nowhere near what would be required to make it work.
You can chalk my comments up to a grumpy engineer tired of the cyclical SBSP pushes that never go anywhere.
Hmm, well I totally understand how it drives spacecraft design and I don’t know off the top of my head the length of greatest eclipse but it cannot be greater than a small fraction of the period (upwards of 1/12). This is significant for a spacecraft itself but as far as a regionally integrated power grid is concerned it is a clear improvement over current solar PV systems.
I get that there maybe some fatigue here with the idea and blue sky optimism that comes with SBSP, I think there are valid criticisms to level at it orbit selection and corresponding ground tracks and eclipses are not one.
> It drives many engineering constraints for spacecraft systems.
Here the only thing it's going to drive are thermal requirements-- which are admittedly significant problems. There's no need to continue to use large amounts of power for comms, etc, like on most GEO birds.
And, of course, the grid needs to deal with the power disappearing for an hour in the middle of the night for short periods of the year.
Why in this case would it cause significant problems? Are you referring to the heating (that would make sense with such a large surface area of panels)?
Concerning cooling- with such short times in eclipse I can’t imagine that it would have enough time to have cooling issues beyond flexing of the superstructure (if made from metals). Be interested to hear though if I’m missing something.
As to power disappearing with an adequately geographically integrated grid I don’t forsee that as really too much of a problem. Currently the grid deals with short term outs fairly well especially if they are planned for months in advance.
> Concerning cooling- with such short times in eclipse I can’t imagine that it would have enough time to have cooling issues
Lots of thin structure with 70 minutes to radiate, with the only thing shining on it the earth's albedo subtending a tiny angle. I'd imagine it creates rather significant demands on structure and electrical connections.
I've not run the numbers on a GEO solar spacecraft, but the smallsat group that I'm mentoring that would be "thicker" than a lot of the GEO craft... gets down to -30C without heaters during its 40 minutes in eclipse while much closer to Earth.
> As to power disappearing with an adequately geographically integrated grid I don’t forsee that as really too much of a problem. Currently the grid deals with short term outs fairly well especially if they are planned for months in advance.
Yup, that's the point I'm making. A space based solar power craft has smaller problems from eclipse than a typical comsat. Batteries, etc, are not nearly as much of a concern. It's mostly the thermals that are left.
There's no real intrinsic electrical or battery system requirements for a giant solar power satellite. The energy use is comparably trivial: no big transponders to run in eclipse like a comsat.
But you do need everything to survive the cold and thermal cycling.
Not just thermal cycling but a giant solar collector is literally a giant solar sail. There would be significant force applied to a giant collector.
You'd need propulsion to maintain position and orientation. You'd also need a number of propulsion units to balance solar pressure gradients as the collector entered and existed the Earth's shadow as well as the thermal expansion/contraction of the structure.
It's likely not a lot of power but a non-trivial amount of fuel.
Ideally sail effect would be used for position keeping, and to reduce loads needed to keep the assembly together. I suppose that would reduce amount of area available for soaking the sun, but might still be lighter than trying to build stiff enough large structures, plus you wouldn't constantly need to ferry more fuel.
You probably maintain orientation with a control moment gyro and periodically desaturate it with thrust. You also use thrust to reboost and stay in orbital slot.
High-impulse ion engines, etc, are a good match for this task.
You'd need a rigid structure to keep the gyro from ripping itself loose from the structure. Even constructed as a giant space frame, that's a lot of mass to deal with the torsion of the structure rotating.
A structure 100m on a side would be just at the bounds of current technology (the ISS's control moment gyros). With 30% efficient panels that's only about 4MW before conversion and path losses.
The high impulse ion engines to desaturate the gyros would still need to be refueled regularly. I think you're hand waving a lot of complexity that even if completely solved still leaves a solution that's orders of magnitude costlier than solar panels on the ground.
This is exactly how the NOAA GOES sats work. Every day at a proscribed time we used to desaturate the reaction wheels, so they could more or less keep running constantly and keep the satellite pointing where it should be.
Yup. This would be big enough that a control moment gyro would be "worth it," too-- and could store a whole lot of momentum and allow less frequent desaturation burns.
If someone has compiled a cost comparison of transcontinental HVDC links compared with the alternative spaceborne solution I'd certainly love to see it.
The space based solution is possibly actually more reliable, as there are actually less components involved that could fail.
One isn't a death ray; but if you only have one, then you need a global power grid anyway.
If you have enough satellites to not need the distribution grid, and they're all in geostationary orbit, then many are over the horizon at the same time and they can (in principle) be combined on the same place.
If they're in a low enough orbit that you only get a few over the horizon at any given moment, you get a substantial penalty from Earth's shadow.
On Mars this would be a great thing for colonies; get past the global dust storms, and it won't matter if you have only a handful of sites; on Earth… pick which failure mode you prefer.
Not for a single device with a fixed wavelength and size; unless someone figures out a way to cheat quantum mechanics and the diffraction limit, how well you can aim light is directly related to the size of your aperture (/antenna) in wavelengths.
Convincing governments you've not cheated with a gigawatt optical laser on your satellites (optical wavelengths being smaller than microwaves makes them easier to focus with smaller parts), that's a separate question. I assume an Iranian one of these would get destroyed by Israel for the same reason they attack their neighbour's nuclear reactors.
The loss from the atmosphere is not the issue; plenty of energy still hits the earth while the sun is out, plenty of methods of capturing it (solar panels, mirrors to focus the heat, etc), the issue is that someone actually has to build it and it goes off at night. That, and transport.
yes, but you can concentrate the beam more than sunlight so that there's less atmosphere involved. You can also choose a beam technology (wavelength etc) based on it going through the atmosphere well, rather than having to stick with sunlight's properties.
Microwave beams are attenuated in heavy rain. Typically, the beam is not going through heavy rain.
The 60% over a kilometer is not due to atmospheric absorption, it's due to losses at the transmitter and receiver (and beam spread exceeding the size of the receiver.) If microwaves lost 40% of their energy in a kilometer radar would have a hard time working.
Millimeter waves are more strongly absorbed in clear air, so they are not as good for this use case. They may be good for powering aircraft.
The 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.
Possible 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_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-nor...
Solar 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.
I 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.
This 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.
Has 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.
Musk 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.
He 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.
At 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...
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.
I think part of the theory with space based solar is to put many small collectors all over the place and avoid some of the need for all that heavy duty long distance transmission infrastructure.
But any benefit there also goes out the window if the SBS reciever is too large or dangerous or scary or ugly to have located all over the place.
People 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.
Elon 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.
You 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.
It's probably the lower cost of earthbound solar and batteries that are the bigger factor in updating the feasability, trending in the opposite direction.
The 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?
I 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.
Came 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.
I 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!
Any 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.
There'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.
and the study itself: 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.