Science Questions

Can we transmit energy via lasers and satellites?

Sun, 13th Jun 2010

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Paul Anderson asked:

Hi Chris and team,


I read an article in the local paper which is talking about using concentrated solar power (CSP) from the Sahara to power Europe. It said that Desertec would need 20 or more efficient, direct current cables each costing $1 billlion to transmit electricity north beneath the Mediterranean.


I wonder if it would be possible to convert the energy into a laser beam which could then be bounced off a satellite back to Europe, thereby not requiring such long cables?

I would be interested to see some discussion.





We put this question to Dr Graeme Hirst, from the STFC's Central Laser Facility...

Graeme -   It is an interesting thought.  Yes, and in principle you can.  People have looked at it for a number of applications.  One is, can you use it to power that satellite?  Satellite power is a tough challenge, and yes, in principle, it can be made to work, but there are issues, obviously.  You'd have to decide how you're going to keep people you wanted out of the way, out of the way of the beam.  Itís kind of an unwritten rule that you never point a laser at anything you don't intend to do.  And so, you would have to ask how you make sure it wouldn't go wrong.  You've also got efficiency issues because even now, even with the very best lasers, they're not 100% efficient at converting electricity into light and then converting it back again.


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There are indeed some very powerful lasers around but these are pulsed so that they deliver a huge power but only for a tiny fraction of a second. In any case, conversion of solar power to electrical energy then back into laser light would not seem efficient. I am not sure that such a high power beam would traverse the atmoshere without a massive loss either.

I believe a scheme that may be practical is to have an array of solar collectors in geostationary orbit devised to convert the energy into microwaves that can be beamed back to collectors on the earth's surface. I think this idea has been around for more than 50 years awaiting the practical engineering ability to make it possible. This would not be affected so much by clouds etc. although it would not be good to accidentally stray into the beam. graham.d, Fri, 2nd Oct 2009

I'm afraid that such schemes are too close to being weapons for any international agreement over them to be reached. LeeE, Fri, 2nd Oct 2009

Most lasers are horribly inefficient. Bored chemist, Sat, 3rd Oct 2009

Good fun though ... RD, Sat, 3rd Oct 2009

The misuse as a weapon is a problem. Also, if it is under human control, human error where someone is thinking of what she should cook for tea tonight instead of concentrating on the job.I am surprised no one suggested that the power directed at a satellite would destroy the satellite. We have AM, FM, pulse modulation, etc, for radio signals. I think I read a year or two ago of having the internet modulated onto our 50h power supply. Can that be reversed and power modulated onto a pulse modulated laser system? However, I accept that with the problems of terrorism and human error that idea may not go further than an idea. I need to read up about fibre optics. Paul Anderson , Sun, 4th Oct 2009

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