Is there any other way?

I've ran into that light craft site before. It got me wondering, could we make cars with giant convex lenses on the roof and focus the suns rays to a small enough point (inside some form of combustion chamber) to light propel a car down the high way.

Electrostatic, photon drive, and a few others. Lego motors are not even close to 100%. Do the numbers (torque*RPM) and I'd be surprised if it hit 70%. Bigger motors do a lot better, up to very high 90%s. Why?

Where are you getting your information? Well-designed practical electric motors can be better than 90% efficient. With superconducting wire and ball or roller bearings, nearly perfect. The inefficiency is in the techniques used to generate and store electricity, which is why water power is so popular - it doesn't have to be very efficient if the source is free and the infrastructure is cheap.

No. You can't make the image of the sun brighter than the surface of the sun. (theoretically, 1m from a 1m lens, you could get a 1cm spot, however, not much smaller.)

And the amount of energy you'd get would be horribly small.

No. But, that's with the sun overhead, or normal to the lens.

I read in sci.electronics.design that John Fields wrote (in ) about 'Is there any other way?', on Sat, 24 Sep 2005:

I read in sci.electronics.design that Ian Stirling wrote (in ) about 'Is there any other way?', on Sat, 24 Sep 2005:

No problem, just make it a 10 m diameter sphere, as in a sunshine recorder. (;-)

Be a bitch to find a parking space. :-)

Ed

That would look funny on the top of your Volvo.

John

In message , John Woodgate writes

A 1 acre field gathers sun energy over time and the horse yields the energy with low efficiency aided by the manual labour of one individual. Vast areas of land "over illuminated" could support panels with moisture conserved underneath for growing . Although by reciprocality It is not possible to focus a sun image with higher surface temp than the sun surface (a mirror) I believe it can be done if lenses of high refractive index are employed. Ignore demon email address.

I read in sci.electronics.design that John Larkin wrote (in ) about 'Is there any other way?', on Sun, 25 Sep 2005:

It would look even funnier underneath it!

It wouldn't take much wind to put it there, either.

What, 6,000 C isn't enough? ;-)

Cheers! Rich

Youre going to have to check my math, but I once calculated the amount of power generated by one acre of sun light (based on contradictory information) and It came out to near 8 megawatts

Use electrolysis to split water into hydrogen and oxygen, and use them to power a rocket. Don Lancaster can fill in the details.

John

The figure I once memorized was about 1kW/m^2 incident light power on Earth. I don't know if that was with the sun in the zenith (where the light has to penetrate the least thickness of atmosphere).

That would come out as about 4MW/acre.

robert