Could Solar Panels in Space Solve all Our Energy Needs?

It takes a huge amount of energy to keep the modern world running. And given that there will likely be another two billion people on this planet by 2050, and we would like them to all have good qualities of lives, our energy demand is only going to go up. Unfortunately, the challenge of meeting this demand is also growing.

Even now, nearly 13% of people don’t have reliable access to electricity. And the fossil fuels we still rely on for most of our energy are not only catastrophically heating up our planet, but also they will eventually run out.

Luckily, there could be a solution, literally on the horizon, in the form of solar panels launched into space! Solar panels have long seemed like a promising solution to our energy problem. After all, they convert basically endless radiation from the Sun into electricity that we can use, without polluting our planet.

But the world hasn’t really gone solar yet. And that’s partly because there’s a limit to how much solar energy we can collect on the surface of the Earth. Solar panels can work well at low latitudes or during summer seasons, whenever the Sun is out and directly shining onto those panels.

But if the weather, the season, or the location aren’t ideal, solar panels aren’t that efficient. Plus, they only work during the day. And they can’t even make the most of the Sun’s energy, because about 30% of the sunlight that shines on Earth gets reflected by the atmosphere.

The best place to harness solar power would be somewhere free of all these limitations, and nowhere is freer than space! The idea of solar panels in space actually started out as sci-fi. In 1941, the author Isaac Asimov dreamed up the idea for a short story he was writing.

But around twenty-five years after that, scientists started thinking seriously about the prospect. In the late 1970s and early ’80s, the U.S. invested quite a bit of time and money into researching how these so-called satellite power systems might work.

The basic idea was to build satellites with huge mirrors, which would collect as much high-intensity sunlight as possible, and redirect it into some kind of solar panel. This light would then be converted into another form of electromagnetic radiation, like microwaves or infrared laser light, and beamed wirelessly back down to Earth.

The benefit is that beams of light at these wavelengths would pass through the atmosphere much better than ordinary sunlight. But wireless energy transfer from space: still a little bit tricky. For one thing, beams spread out and dissipate over long distances.

Also, the transmitter and receiver would be constantly moving relative to one another. Still, scientists have come up with two possible ideas for how to make this work. The first is to beam down the collected energy with microwaves, which can pass easily through the clouds and storms in Earth’s atmosphere.

And this would happen from a specific spot in Earth’s orbit. Scientists noticed in the 1960s that satellites in high orbits that kept pace with Earth’s rotation spent almost no time in Earth’s shadow.

So one of these so-called geosynchronous orbits would be an ideal place for solar power satellites. This would also solve the issue of sending a beam to a moving target, since satellites in geosynchronous orbits stay roughly in the same part of the sky as the Earth rotates.

Unfortunately, this solution comes with a new challenge: Geosynchronous orbits are really high up, like, 35,000 kilometers above Earth. We do have some satellites there… but this wouldn’t be just any satellite.

To deliver a worthwhile amount of energy in the form of microwaves, these satellites need a huge antenna and massive mirrors. According to some designs, they’d weigh about 80,000 tons, with mirrors three kilometers in diameter.

Just getting a single satellite of that size up to a geosynchronous orbit would take several rocket launches, and it would be almost impossible to maintain or repair. Plus, over such a long journey across space, the beam would spread out significantly, meaning the receiver on the ground would have to be several kilometers across to intercept it.

Still, the rewards could be enormous. A single low-intensity beam of microwave energy from this type of satellite could supply several gigawatts of power, which is enough to fuel a large city. Fortunately, if the hurdles do end up making this one impractical, there is another option, and this one might be a little more feasible: small, laser power satellites orbiting much closer to Earth.

It’s much easier and cheaper to get a small satellite up four hundred kilometers into a low-Earth orbit. So engineers have come up with a small design that uses an infrared laser, rather than microwaves, to beam down their energy.

Compared to microwaves, these specific wavelengths of radiation wouldn’t pass as easily through thick clouds and storms, but they’d come with a lot of other benefits. Like, at just ten tons each, they could easily be deployed with a single rocket launch.

Plus, they’d be much easier to assemble and repair. Also, lasers naturally have super narrow beams, which would stay fairly narrow over the much shorter distance to Earth. That means they could work with a smaller receiver on the ground.

The catch is, because of their smaller mirrors, and the fact that they’d pass in and out of Earth’s shadow, individual laser satellites could only deliver a few megawatts of energy. So scientists think it would take an entire array of laser power satellites working together to make a significant impact on our energy needs.

So for now, there are still some challenges to work through before space-based solar power can become a reality. But it’s not really the technology that’s holding us back, it’s more the cost and the commitment.

At the moment, several countries are actively trying to get solar power satellites off the ground, including the U.K. and Japan. And in 2020, the U.S. conducted the first solar power experiment in orbit.

Engineers put a solar panel on board a highly classified military drone that orbits three hundred kilometers above the Earth’s surface, to see how this tech would fare in space. Today, it may still be some time before we can charge our homes wirelessly from space as easily as we charge our phones.

But the sci-fi future Isaac Asimov imagined 80 years ago isn’t that far beyond our grasp. And speaking of creative people, this episode of SciShow Space was brought to you by Skillshare, an online learning community where creative people can grow their skills.

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