Space-based Solar Power: Endless Sunshine to a Fried Earth

In recent years, space agencies from all over the world have launched studies looking at the feasibility of constructing orbiting solar power plants. Such projects would be challenging to pull off, but as the world’s attempts to curb climate change continue to fail, such moonshot endeavors may become necessary.

Solar power plants in space, exposed to constant sunshine with no clouds or air limiting the efficiency of their photovoltaic arrays, could have a place in this future emissions-free infrastructure. But these structures, beaming energy to Earth in the form of microwaves, would be quite difficult to build and maintain…

A space solar power plant would have to be much larger than anything flown in space before. The orbiting solar power plant will have to be enormous, and not just to collect enough sunlight to make itself worthwhile. The main driver for the enormous size is not the amount of power but the need to focus the microwaves that will carry the energy through Earth’s atmosphere into a reasonably sized beam that could be received on the ground by a reasonably sized rectenna. These focusing antenna would have to be 1 mile (1.6 kilometers) or more wide, simply because of the “physics you are dealing with. Compare this with the International Space Station, at 357 feet (108 meters) long the largest space structure constructed in orbit to date…

In every case, building a space-based solar power plant would require hundreds of rocket launches (which would pollute the atmosphere depending on what type of rocket would be used), and advanced robotics systems capable of putting all the constituent modules together in space. This robotic construction is probably the biggest stumbling block to making this science fiction vision a reality.

Converting electricity into microwaves and back is currently awfully inefficient
Airbus, which recently conducted a small-scale demonstration converting electricity generated by photovoltaic panels into microwaves and beaming it wirelessly to a receiving station across a 118-foot (36 m) distance, says that one of the biggest obstacles for feasible space-based solar power is the efficiency of the conversion process… Some worry that microwave beams in space could be turned into weapons of mass destruction and used by evil actors to fry humans on the ground with invisible radiation.

A spaced-space solar plant transmits energy collected from the sun to a rectenna on earth by using a laser microwave beam. Image from wikipediia

The vast orbiting structure of flat interweaving photovoltaic panels would be constantly battered by micrometeorites, running a risk of not only sustaining substantial damage during operations, but also of generating huge amounts of space debris in the process. For the lifecycle of the station, you have to design it in a way that it can be maintained and repaired continuously…

And what about the whole thing once it reaches the end of its life, perhaps after a few decades of power generation?  It is assumed that, by the time we may have space-based solar power plants, we are most likely going to see quite a bit of permanent infrastructure on the moon. Space tugs that don’t exist yet could then move the aged plant to the moon, where its materials could be recycled and repurposed for another use…We could also have some kind of recycling center on the moon to process some of the material..

Excerpts from Tereza Pultarovanal, Can space-based solar power really work? Here are the pros and cons,, Dec. 23, 2022

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