more energy

[trenner]

A thought I have been mulling on......
If a space vehicle has Sun 24/7, is a solar cell the only means of generating energy? With radiant energy, wouldn't a big honkin magnifying glass be able to do something?.....

Regards
Terry Renner

[selden]

Terry,

What are you suggesting that the magnifying glass be used for?

A solar cell has the advantage that it has no moving parts. One way to make solar cells more effective is to use a lens to capture light from a larger area onto the cells.

[Hungry4info]

I think he means to put a mignifying glass out between the arrays and the sun, so that the light is focoused onto the arrays (kinda like we all used to do with ants haha). If you did that, I think it would be the same has having an array the same size as the magnifying glass. After all, it's still the same area gathering sunlight, whether it be a magnifying glass focousing it onto a small array, or a larger array the same size as the magnifying glass.

I'm not all to sure on this, though.

[trenner]

I guess where I'm wallowing around, is comparing photovoltaic energy to radient energy
We "feel" the Sun. With a magnifying glass, we really feel it. Slip a cryogenic boiler in there, and turn something, mechanically instead of electrically
Now that I think about it, I guess friction and insulation would be big minuses.

Regards
Terry Renner

[eburacum45]

The Solar Moth concept uses focused sunlight to create a thermal rocket effect. See this entry at the Project Rho page
http://www.projectrho.com/rocket/rocket ... #solarmoth

Solar Moth: SOLAR THERMAL ROCKET. 175 meter diameter aluminum coated reflector concentrates solar radiation onto a window chamber hoop boiler, heating and expanding the propellant through a regeneratively-cooled hoop nozzle. The concentrating mirror is one half of a giant inflatable balloon, the other half is transparent. Propellant is hydrogen seeded with alkali metal. The advantage is that you have power as long as the sun shines. The disadvantage is it doesn't work well past the orbit of Mars and the exhaust velocity is pathetic. This might be carried on a spacecraft as an emergency propulsion system, since the engine mass is so miniscule.

Here is a model of a solar moth in Celestia
http://img293.imageshack.us/img293/2145/itokawaos7.jpg

[bdm]

The magnifying glass would work well if it was a Fresnel lens.

[duds26]

In very high-efficient solar cells sunlight is being concentrated. Although not very much, with concentrating the same energy on a smaller area, a solar cell can get more energy out of it because it's intenser and electrons in metal get less chance of hopping back because of the bigger flow of energy.

A solar cell has an internal resistance, this causes electrons to fall back and loose their energy as warmth before converting it to electricity. A more intense flow of energy (more concentrated light) avoids this.