Science Questions

Could we use solar panels in space?

Tue, 2nd Sep 2014

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Question

Benjie Fairbanks Weston asked:

If solar panels were put in space, how could the energy produced be sent back to earth?

Answer

John C. Mankins -  In space near Earth, sunlight has roughly 30% more energy than the sunlight we see, because of weather and haze in the atmosphere. When one adds the impact of the day/night cycle and the natural changes between summer and winter,  in some locations, the difference between Earth-based and space-based solar power grows to a factor of 20 or more.

It is possible that in the future, space solar power could deliver hundreds of thousands of megawatts - enough to power tens of millions of homes around the world.

First, just as on earth, sunlight in space will be converted into electricity by solar rays, that in turn power used electronic devices that produce radio waves in what is known as the "microwave" region - a wavelength of about one to ten centimeters.

This microwave energy is then transmitted from many thousands of small antennas, very much like thousands of musicians all playing the same note on their instruments. By orchestrating the individual transmitters - like an orchestra conductor with his baton guiding many musicians  a coherent beam can be formed, and the converted solar energy directed to a desired location on Earth. 

Radio waves of this size have virtually no interaction with our atmosphere, and very little with our weather; in other words, the atmosphere is almost invisible to them.   As a result, more than 90 percent of the radio wave energy from space will reach Earth in a low intensity, but precisely pointed transmission.

Once there, the microwave energy is converted back into electricity by a large but simple receiver known as a rectifying antenna, or "rectenna" which will look a lot like mesh fencing, just like one of the goals in International football, but laid out flat, like a semi-transparent ceiling.

And that's it - that's how solar energy collected in space can be transmitted efficiently and safely back to Earth for our benefit.

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A proposal was made a few years ago, and perhaps a few decades ago to use microwaves to beam the energy down from space.  See the discussion here.
http://www.thenakedscientists.com/HTML/questions/question/2849/
http://www.thenakedscientists.com/forum/index.php?topic=35774

Building such a system would be extremely expensive, and likely would not pay for itself.

Alternatively one might build a large parabolic mirror, and focus a beam of white light to the earth.  I think I saw a suggestion of inflatable supports.  In space, it would take very little gas to fill, but any leakage would be extremely expensive to replenish.

Depending on the size of the beam and intensity, it could be damaging to birds, insects, or aircraft, although short-term exposure likely won't be a big problem. CliffordK, Tue, 8th Apr 2014

There is already a vast amount of radiant energy coming in from space if one uses a expensive system to concentrate it it can be collected over a smaller area but it is far more economical to increase the collection area. syhprum, Tue, 8th Apr 2014

I could imagine huge solar installations put into the Sahara Desert.  However, that wouldn't help London much as power transmission cost would be too high, and transmission losses would be significant. 

There are, of course, a lot of rooftops that could support solar panels around the globe, and one could invest in a greener economy everywhere. 

The space mirror might help bring the power to where it is needed. CliffordK, Tue, 8th Apr 2014

Another option...

Could one replace street lamps with space mirrors?  Bring summer to the winter?  Ok, so much for Global Warming with that one.

No need for fancy collectors, just bathe a city with reflected sunlight.  A 1:1 reflector size might be like a second sun.  However, if "light" is the goal, perhaps one could make it significantly smaller.  A full moon on a clear night is pretty bright, but only puts out about 1/400,000 of the light of the sun.  So, making your reflector, 1/1000 the size of the city might be adequate at least for outdoor lighting. CliffordK, Tue, 8th Apr 2014

We just need to explode a very large bomb filled with glitter in high-earth orbit! This will slightly reduce the amount of light reaching the day-side of the Earth, and dramatically increase the light available on the night side, reducing hour-by-hour variability in the output of solar panels (reducing difference between night and day), especially for those further from the equator.

(Just kidding...) chiralSPO, Tue, 8th Apr 2014


The USA already tried that...
Well, with 1.78 cm copper needles.

That would be an interesting concept, rather than directed light, it would give random directions of reflection.  CliffordK, Tue, 8th Apr 2014


I am still not sure it is possible or not..Seems like an interesting prospect and it would easily solve our power issues.. AdamWatkins, Fri, 10th Oct 2014



The moon does a perfectly adequate job in the countryside, and nowadays I do believe that they city folk have that there electric light thingy when they needs it.

What's so wrong with a bit of dark? alancalverd, Fri, 10th Oct 2014

Get rid of streetlights - we should all have night vision by now, but the tech companies have been slow at providing it. The hardware's available and cheap, so why can't we buy them yet? It only takes two little screens held horizontally above the eyes, then flip-down mirrors and lenses for when you want to see them. These could be used as your TV, your computer monitor, your phone screen, your camera viewfinder, etc. - anything that needs a screen would simply use the one stereo display that you can wear all the time, and a pair of camears would give you stereo night vision, as well as video and photographic capability. And yet, all we're offered at the moment is that ridiculous Google Glass thing or giant virtual reality headsets! David Cooper, Fri, 10th Oct 2014

I think they could be used, with a geostationary satellite, it remains in a fixed position.  That way, it could be placed facing the sun.  If it was combined with solar panels, I think it could be done.


Satellites in geostationary orbit.
https://en.wikipedia.org/wiki/Geosynchronous_satellite
https://en.wikipedia.org/wiki/Geostationary_orbit


Teena, Sun, 7th Dec 2014

ask yourself, is there light in space? then ask are there shadows in space, yes and yes. The way we harvest light into energy is because of electromagnetic waves, and because there is light in space that proves that there is also electromagnetic waves, which then means yes it is definitely possible to harvest light into electric energy via satellite, and i have a theory that we can deliver that energy through high intensity "lazers" or light beams down to earth which are then collected into a, or multiple solar panels, that then convert the solar energy (electromagnetic waves) back into electric energy. The only real problem is the fact that the high intensity beams would use up a portion of the converted energy, but when you think about it it's probably less expensive then shipping solar power batteries back and forth. Or it honestly could be as easy as launching a giant mirror with a giant magnifier glass that is directed at a solar farm. but there is another problem, using both of these methods could potentially cause global warming. So in a sense both methods either beaming light down or using a type of retrieving device to collect solar batteries would be polluting the earth with heat or fossil fuels burning and causing an even more intense green house effect. themaht78, Wed, 14th Jan 2015

If solar panels were put in space, sent the energy produced back to earth would just be a waste of resources.  Maybe we can use these energy in the space such as provide the energy needed to power a spaceship, like an energy supply site.


diethyl, Mon, 9th Mar 2015

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