Power Tower in Space: Feasibility & Practicality

[MacIntoShiba]

Hello,

I'm wondering about the practicality and feasibility of building large power tower structures in space.

I could imagine something like follows:

Take a long structural beam which is positioned in alignment to the sun rays. At the end closest to the sun a receiver is placed. Consisting of a cylinder consisting of hundreds of small tubes. Running also parallel to the sun rays. At the bottom a cool medium is compressed and enters (some kind of gas), travels through these tubes and heats up till it exits heated at the top to perhaps 700degC. The medium enters a turbine which also drives the compressor and excess mechanical power is converted to electricity. The expanded medium is transported by a tube to the end of the structural beam and fed through radiators which radiate away excess heat. Perhaps it would be possible to add another lower temperature cycle to increase efficiency.

At the other end of the main structural beam more structural beams are at an 90deg angle with the main structural beam and they spread out like the spokes of a wheel. Between the spokes cables are strung.

Mirrors consisting of reflective foil are placed at various intervals and connected to the spokes. These mirrors reflect the light onto the receiver.

The whole structure slowly rotates along the axis of the main structural beam so as to enhance positional stability.

The structure could rotate around the earth at a geostationary orbit and beam power back to earth.

 

[Baluncore]

Sounds great, but I have a few minor questions about the details.

You need to sketch the design, so we can see how much material is involved. All that material must be launched and economically assembled in space.

A disc can be stabilised by spinning on its axis, but not a long thin spindle or beam structure. A long, thin structure will alternately flip end over end, cyclically between modes.

Exactly how do you get the electricity to where it will be used?

A geostationary orbit is expensive because it is a long way up (36,000 km, 22,000 miles), and is populated by communication satellites.

There will be recurring outages. Geostationary satellites pass through the shadow of the Earth because the Earth's orbital plane about the Sun is close (23.4°) to the equatorial plane of the Earth.

 

[Vanadium 50]

One way to decide if building it in space is economical is that it costs about (factor of 2 or so, depending on the details) the same to launch something as it does to make it out of gold.

Does your idea pass that test?

 

[PeroK]

I'm wondering about the practicality and feasibility of building large power tower structures in space.

We don't currently have anything like that engineering capability.

 

[sophiecentaur]

We don't currently have anything like that engineering capability.

When any such system comes into your head (thoughts in the shower etc.) then here's a good feasibility test. In Earth's orbital position, every meter squared receives about 1kW of solar power. So you decide what power you need - say 10TW (to be worth while) and that tells you the sort of area your collecting structure would need, which shows you would need around 10¹⁰ m² of collecting area. That's a lot bigger than we have managed so far - but give it time.

 

[mfb]

Why would you want to have such a structure in space? Moving parts make it likely to fail, and cooling the cool end is a big problem in space. On Earth maintenance is easier and you can use the environment for cooling. You also save the launch costs.

say 10TW (to be worth while)

To be worthwhile, a power plant would need to exceed Earth's global electricity production by a factor 5?

 

[sophiecentaur]

On Earth maintenance is easier and you can use the environment for cooling. You also save the launch costs.

That's been my view about nearly all these proposed space borne projects. Anyone would think that we are actually short of real estate down here on Earth. There are so may Engineering problems involved with shifting Power from one place to another and they're all much harder when you're trying to 'beam' if from place to place over vast distances in space.

It's fine to discuss extreme future fiction / fact but the caveats should always be stated first.