Solar Powered Generator?

[JRod]

I have a question that might have been discussed before, but I couldn't find any pertinent info. I have thought about building a generator of the type that's normally used for a wind system, and powering the turning of it by solar panel provided work. Does this sound like a silly idea? I am thinking that depending on the effeciency of the generator, I could get more bang for the buck like that rather than using the energy from the PV cells directly, as well as the sun being more reliable around here than a steady wind. Any thoughts?

[kitno455]

what are you talking about? generating electricity from PV, turning a motor, that drives a generator, that produces electricity? uhm, law of conservation of energy, combined with less than 100% efficiency, mean that the power out will be less than the power in.

the only reason i can see to do that is use a dc motor to drive an ac gen, so that you change from DC to AC. but they have solid state devices called inverters to do that now.

so no, this is not useful.

allan

[JRod]

Yes, I thought it was going to be a stupid question. I must not have paid enough attention in high school, as soon as I read the law I remembered why I had a nagging feeling that it wouldn't make sense to get more energy that way, and why that kind of thing was never attempted. Thanks for the prompt reply.

[Norm]

  However, a solar powered engine is feasible ...

that turns a generator that makes electricity.

  But then solar cells are easier and more

efficient.

                    ( :>) Norm.

[Vernon]

One way would be to drive the generator with a solar powered gas turbine. An array of mirrors would focus the sun on what would ordinarily be the combustor can. A similar concept was tested using the waste heat from a fuel cell to drive a turbine with over 70% total efficiency. You would have the advantage of being able to burn natural gas in the combustor at night.

[Jeff7]

Be great if it was possible - just hook up a string of motors and generators, until you wind up with a few gigawatts of power from a single solar cell.

[stop4stuff]

Or would it?

Alternator efficiency 90-95%

Stirling engine efficiency 40-50%

Overall (90% & 40%) efficiency 36% compared to the most efficient PV panels at 13-15%

Also a stirling powered generator is more within the realms of a homebuild than a PV panel... eg a 1kw stirling/generator was 10% efficient and homebuilt for a couple for hundred is still way cheaper than bought PV panels and a viable homebuild option.

[bob golding]

just  started  reading up on using a tesla turbine to do just that. seems the jury is still out on the efficiency of tesla turbines at the moment.

bob golding

[JRod]

Well, I've been doing a bit more brainstorming... dangerous I know. I was thinking now more along the lines of a multi purpose system. Something like a wood burning stove, with a section that generates steam from the heat, which turns the generator, and using the excess heat to heat the room/home. Nothing planned out really, but been looking into the plans people have already made for steam based generators and how to possibly integrate that into my idea. My pops has a phd in physics, I shot him out an email, since that kind of thing is really in his realm, and can bring me into reality. =] Some times when he goes off on a tangent talking about astrophysics I just have to stop him, since he passed me up like 10 minutes into it.

[Vernon]

http://www.heuristicengineering.com/papers/Stockholm.pdf

Why bother with steam, feedpumps, condensers and the rest. The above article discusses an external combustion gas turbine, hot combustion gases from the burning wood heat the compressed air from the GT compressor just as combustion would. Components of truck turbo chargers could be used and a high speed PM alternator placed on the shaft between the compressor and turbine.

[Kwazai]

only reason I could see to do that is if you wanted to store water for later use to generate energy (nighttime). using excess from pv cells to store energy. probably would be cheaper (though it would eventually wear out) to use conventional batteries.hadn't ever run the numbers though.

L8r

Mike

[JRod]

Well I got the email back from my dad asking about the question of solar based generators and the law of conservation. Interesting note about the wind farms...

It's true that there is energy lost in any kind of device that converts energy from any form to any other form: friction, radiation, etc... usually lost as heat.  But so what?  The best solar cells convert 5 - 7% of the light striking them to electricity, but the sun is going to shine and deliver as much energy to earth whether we have solar cells out there or not. 2% (the efficency of cheap, large scale cells) is better than 0%.  The same can be said of wind and tides, but that is a little more complicated. Studies have been done of very large wind farms that indicate they would actually soak up enough wind to change the weather.  Tidal power, produced by turning huge rotors (like mammoth flattened versions of 18th century water wheels) would clearly destroy coastal ecology, already in trouble.  In the end, they will all be used after the oil and gas run out. -Dad