Could Solar Power Satellites Beam Down Gigawatts of Energy?

so... what happens when it gets hit by a space pebble?
I think I'll keep my money on solar thermal, thank you.

A solar panel in space would generate about 5 times more power than would an equivalent panel on the ground at a low latitude with average cloud cover. Essentially, it would generate close to its peak wattage at all times. That's cool; that's the promise of space-based power. But the economics aren't so simple.

Solar panels today cost a few dollars/watt (divided by ~5 since we'd be in space, and that gives about 25 cents to $1 per watt), and this number is falling with time. However, most panels today generate only a few watts (times ~5) per pound of panels, yet sending material into space currently costs thousands of dollars per pound. That number (about $10,000/pound, as of 2000) has not changed much in 50 years.

In other words, before we even start talking about designing and building the facilities to transmit and receive the beamed power, this kind of satellite will cost hundreds of dollars per watt. That's a steep price just to avoid intermittency; it would be much cheaper to build new and better transmission infrastructure and a smart grid on the ground, especially since that would give us the flexibility to let a mix of intermittent renewable sources provide a large share of our energy even without large-scale storage technologies.

If we had a space elevator or some other equally cheap means of reaching space, then the higher wattage per unit area and constant availability of sunlight would make power from space both feasible and cost-competitive. Maybe that will happen soon, maybe it'll take a century, I have no idea. But we shouldn't bet on it. Right now, any renewable resource here on the surface, and nuclear power, too, are far, far cheaper than space-based solar.

Energy is measured in Joules. Power is measured in Watts.

A good idea with large obstacles to be overcome.....

What is the potential for causing an increase in global warming due to atmospheric heating caused by the transmission of this power beam?

That seems to be an issue no one ever addresses.

The hard part of space is getting up out of Earth's gravity. It makes more sense to use robots & lunar material to construct these.

re sidewinder
Solar energy at Earth orbit is energy that was going to hit the Earth anyway. These systems could eventually be used to shade the Earth selectively by reflecting away unwanted energy (IR) before it strikes the atmosphere. Or concentrating it should the need arise.

I'd also like to point out that a steam cycle powerplant (coal, nuke, etc) already dumps almost 4x as much heat energy into the atmosphere as it's rated capacity before you even consider its construction or cleanup because they are only 33% efficient - 8% distribution loss. Based on 2006 numbers, humans are running a 60TW heater 24/7.

That said, the gross solar energy hitting the Earth's upper atmosphere is 174PW which is to say 174,000TW which is to say 11,600x the entire global energy consumption. Space based solar could replace all existing energy needs and deliver 10x more energy per person with existing technology easily paying for itself and improving life for humans and other animals all over the planet.

Ugly - Good point about conventional power plants.

My concern about these beams is the effect they could have by virtue of being shifted down in wavelength into the microwave band. And the fact the power beam would result in localized heating rather than diffuse heating.

The numbers you quote indicate that the effect might be small, but then that was what we thought about our other endeavours.

IIRC, solar power in orbit is around 1450 W/sq.m. On Earth, it averages 768 W/sq.m, so it's more like double in space, not five times. That is, if I remember correctly.

Current technology (pardon the pun) for solar cells is at best around 25% efficient, with some recent lab results exceeding that significantly, but nothing that is, at this time, producible in large quantities. So, using 25% efficiency, you could capture about 360 W/sq.m on the wings of a satellite. Conversion and beaming to Earth is going to have some significant transmission losses, probably delivering around five percent of the captured energy to the rectenna and into the grid, or around one percent of the original energy. Still, that's not bad.

The big question that remains is what the perceived and actual effects on the environment are. Perceived effects result in lawsuits, often overwhelming to development companies. Actual effects impact all of humanity.

J.D. Ray - Isn't that number for sunny conditions on earth, though? Considering cloud cover and other impacts, I could easily see that number climb to 5.

@JD Ray:
The solar constant in Earth orbit is around 1400 watts/m2, that is true. ~30% gets reflected off the atmosphere. There is, after that, a 4-fold reduction from geometry. From the Sun's perspective, the Earth is a disk intercepting an area of solar radiation of Pi r^2 (r= earth's radius). But the Earth is a sphere with surface area 4 Pi r^2. In other words, not all the Earth's surface gets full sun 24 hours a day- on average, the surface receives 1/4 sun.

@sidewinder: While you are correct in principle, the amount of power used by humanity is very small compared to the amount of sunlight already reaching the Earth. Also, the waste heat produced from burning fossil and nuclear fuels today is greater than we would be introducing from space-based power. Even if our choices were getting all our current energy needs (Let's say 10 TW, to make it simple) from space based solar versus renewables on the ground, it would only change global average temperatures by

@ugly american: You're off by a factor of 4. 15 TW is mankind's rate of total primary energy consumption. We use just over 2 TW of electricity, about an equivalent amount to actually move vehicles, some more to provide heat for various uses, and most of the rest is waste heat. This makes your claim, that our direct contribution to the Earth's heat balance through waste heat is currently insignificant, even more true.

In all likelihood, though, an orbital power station will NOT be just providing power that would have hit the Earth anyway. If it did, it would need to be between the Earth and the Sun at all times, which would mean it would be constantly correcting its course (since there is no stable orbit that is always between the Earth and the Sun, unless you put it at a Lagrange point. Moreover, it would be very difficult to keep beaming the power to the same spot on the ground, especially at night, in such a situation. More likely the satellite would be in orbit far enough away that it could maintain the relative orientation to the receiving station on the ground while still providing continuous power.

So while several TW or tens of TW of power from space would not be a big deal in terms of the Earth's heat balance, petawatts and tens of petawatts probably would be. Luckily we've got another century or three to worry about that problem before it becomes a second crisis of global warming. Still, I think if we go for space-based solar the prudent course would be to just use the power in space (by taking other industry off-world, too) instead of beaming it back down.

It's very unlikely one would want to launch conventional solar cells into orbit for a Gigawatt power plant. They are just too heavy and expensive.

Instead, most concepts involve putting up a huge mylar mirror. Compared to solar cells, it would weigh almost nothing. The mirror collects and focuses the solar power onto either a heat engine which supplies power to a maser, or in some concepts, pumps the maser director.

The maser then beams down the microwave radiation to a receive station on earth.

Regarding added heat - yes, this would add some extra energy into our environment. Not much when it's on the sun side of Earth, but when on the dark side. But ALL of our power production does this. This would add a lot less heat than equivalent ground-based methods since ground-based methods are inefficient and generate a lot of waste heat when producing energy. In this system, no waste heat is generated on earth, and since at least part of the concentrated energy would have hit Earth anyway.

But heat death will always be a limit to how much power we can consume. It all ends up as waste heat. Many futurists and Sci-Fi writers have dealt with this idea ( Consider the home planet of the Puppeteer civilization in the RingWorld series).

Considering the technological unknowns and huge expense, not to mention the difficulty of servicing the orbiting powerplant, the problems would seem to me to be too great to overcome the financial inertia needed to make it happen, at least until the space elevator gets built, which will change the economics radically.

One thing which has not been discussed in regard to this scenario is what kinds of jobs will be created and what kinds of skilled workers would be required. A space based solution will focus on a very high tech approach because to make an orbiting solar plant very easy and fast to assemble, lightweight, and sturdy will be several factors more expensive than earth based units. This will be necessary because with a limited number of spacecraft and highly trained astronauts (and the huge expense of increasing those) the ease of installation is key.

Earth based units can be installed by construction guys and repaired by easily trained electricians of which there are plenty of candidates. The panels themselves can be off the shelf units that will go down in price quickly because along with the volume of panels for the solar plants, every other earthbound solar application can come off the same assembly lines.

Even if the efficiency of the orbiting panels is greater and not interrupted by night, it would be much cheaper and easier to make earthbound solar plants and implement a VTG (vehicle to grid) program to deal with the storage issue.

Imagine the power company offering low cost or free power for your car in exchange for making use of a small amount of the spare capacity in your electric car's batteries.
This scheme would also usher in the age of the electric car as well as the solar power age.

When houses are manufactured with solar roofs as a standard feature the need for centralized power plants will disappear, as every new building will generate more than the power it needs.

Won't getting more energy just warm us further, surely we have plenty of energy available if we just use it more efficiently?

@ug33:

In all likelihood, though, an orbital power station will NOT be just providing power that would have hit the Earth anyway. If it did, it would need to be between the Earth and the Sun at all times, which would mean it would be constantly correcting its course (since there is no stable orbit that is always between the Earth and the Sun, unless you put it at a Lagrange point. Moreover, it would be very difficult to keep beaming the power to the same spot on the ground, especially at night, in such a situation. More likely the satellite would be in orbit far enough away that it could maintain the relative orientation to the receiving station on the ground while still providing continuous power."

Not really. Geostationary orbits are in total sunlight 24/7 (with 2 short eclipse periods (hrs) each year). They are far enough away from the Earth (35786 km altitude above equator) that the Sun's shadow only passes over them for a short period twice a year (okay there will be several eclipses in the eclipse periods, but most are very short

It's the same orbit as DirectTV/Dish satellites. You don't have to move your satellite dish on your house, and yet you get 24/7/365 reception (save in bad weather... your dish is moving a lot or covered by snow and some atmospheric effects).

Those satellites also have eclipse periods, it's just that they have batteries to keep transmitting. I wouldn't recommend enough batteries to keep transmitting power from solar power beaming satellites, just enough to keep the satellite itself alive during the eclipse.

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Launching such a large satellite in parts would be extremely expensive, even if cost drop to 10% current costs. Manufacturering solar panels in orbit might be cheaper in the long run, though that has significant technological issues to overcome.

Space rated solar cells are typically much more efficient (~35%) than terrestrial, although they are a lot more expensive.

Space debris is a signficant issue. Putting such a large object in geosynchronous orbit would also be a political issue, since orbital slots are set up by the ITU via the UN. Slots are typically 1 deg apart, though countries will often formation fly in the same slot using different frequencies or beam patterns. A large satellite would be a potential inteference problem.

But it's late and I digress...

Why would you do this when you could buy and use solar panels here on earth for much cheaper.

we need to shoot something into space that will crystallize and grow. Crystallization studies have already been done in space for decades. Just shoot up some sort of thin film that unfurls covering a large area, and let it crystalize in space. If the cold is a problem then you make it a bubble thingy that can trap heet to, to make the crystals. Maybe make a biodome-ish thingy in space, where u have biostuff making the crystals. Probably got to shoot up a few hundred pounds of compressed O2 or CO2 and/or H2 or H2O to get the biolife-to-crystal reactions on the thin-film (or bio-crystal-bubble started). Connect it all to a electric wire transmitting the sun's energy to the dish that then beems it back to earth. Very cheap. Very doable. Today. Nothing more than the usual cost of your average shuttle payload.

Are this microwave bims going to cook everything on their way ?