PV Gap

Priscilla Said:

Solar Harvesters?

We Answered:

Your ideas are on the right track, I think, but not completely thought through.

I attended a lecture in 1980 on a NASA study on Solar Power Satellites. They had analyzed many possible designs.

The winners were all in geosynchronous orbit. This is optimum because they need to stay over the same piece of ground to transmit the power down.

Solar cells was the preferred technology; they also had steam engines run by concentrated solar power from reflectors.

The power was transmitted to receiver "antennae" on the ground. Microwave ones had theoretical efficiency of 80%, lasers 90%. The microwaves receivers were several km in diameter, basically a suspended wire mesh with potential for growing crops underneath. Laser receivers were less than 100m across. Aircraft were to be steered around the beams to prevent damage. Both microswave and laser beams were dangerous.

No pollution, essentially infinite power due to huge area in space. SPS loses power when in Earth shadow, but short duration, only a few SPS's at a time, Earth bound wires would provide backup.

Cost was the only real technical obstacle. It was pretty big. They were planning to reduce costs by making a moon base with an electromagnetic gun to shoot materiel to the SPS's.

Norma Said:

Solar Harvesters?

We Answered:

The tether would be the most impractical point of this idea, as the forces (not to mention the sheer length of the cable) would be too great for current technology to handle.

The thought of solar energy from space, however, has surfaced in numerous science-fiction works. Usually, such contraptions are said to "work" by converting solar energy into high-energy electromagnetic radiation (i.e. microwaves) and sending them to the surface recievers as concentrated beams.

But again, our current technology does not make this method practical, safe, nor realistic.