In theory I like solar power a lot. There’s a lot to be said for energy that falls from the sky for free for as long as we care to use it. But actually getting that energy to do useful work in an economical way. Solar panels are expensive and not terribly environmentally friendly to produce, and sunlight is only available during the day and only to the extent that the sky is clear. Getting energy to use during less sunny periods requires either lots of excess capacity during the day along with storage facilities, or alternate generation methods. The first is wildly uneconomical, the second at least partially defeats the purpose.
Still, it’s not a bad technology and with time it’s likely to become more and more practical at least for areas with high insolation. (Insolation being the snazzy word for the solar power shining on a particular location, typically averaged over a year to take into account day/night/seasonal/weather variations.) The average insolation per square meter at the earth’s surface is this, according to Wikipedia:
White corresponds to about 200 watts per square meter, so for instance your computer will probably take about 1 square meter worth of solar panel to operate on average. During a sunny day it will take a lot less, but during the night you’ll have needed the extra area to store energy to use while the sun is down.
There are alternatives. You could put a solar panel in space and beam the power back down to earth. Leaving aside all the practicality considerations, it’s not a bad way around some of the problems of solar. There’s no night and no weather, so you’ll get the full ~1300 watts per square meter of sunlight 24 hours per day, 7 says per week. Which is pretty nice. You’d still need a lot of solar panels – the US eats about 3.8 trillion kilowatt hours per year, which works out to about 130 square miles of solar panels each getting the full blast of constant sunlight. Still, it’s not something that’s entirely inconceivable. You’d need many times that to get the same amount of energy from panels at the earth’s surface.
What about getting the power from space to the ground? Running an extension cord is out of the question. The easiest way is to turn the energy back into light and shine it down to collection stations. Clearly just using visible light wouldn’t help, you want something easier to collect. Microwaves are an easy solution. Set up a field of cheap metal antennas oriented in the appropriate direction and you can capture the beamed down radiation cheaply and easily.
The Japanese space program is planning to give it a try:
The concept of solar panels beaming down energy from space has long been pondered–and long been dismissed as too costly and impractical. But in Japan the seemingly far-fetched scheme has received renewed attention amid the current global energy crisis and concerns about the environment. Last year researchers at the Institute for Laser Technology in Osaka produced up to 180 watts of laser power from sunlight. In February scientists in Hokkaido began ground tests of a power transmission system designed to send energy in microwave form to Earth.
The laser and microwave research projects are two halves of a bold plan for a space solar power system (SSPS) under the aegis of Japan’s space agency, the Japan Aerospace Exploration Agency (JAXA). Specifically, by 2030 the agency aims to put into geostationary orbit a solar-power generator that will transmit one gigawatt of energy to Earth, equivalent to the output of a large nuclear power plant. The energy would be sent to the surface in microwave or laser form, where it would be converted into electricity for commercial power grids or stored in the form of hydrogen.
It will be crazy expensive. To get a payload to geostationary orbit is something like $10,000 a pound, and space-hardened solar panels and microwave transmitters are not exactly featherweight. The power generated will have to be very cheap and reliable indeed to make up for the truly massive infrastructure costs.
To make matters worse, those of you who used to play Sim City might remember a disaster where just this technology would get knocked out of alignment and set your city on fire. But fortunately this wouldn’t happen in the real world. The power densities at the ground are relatively small; in the proposed eventual Japanese implementation they work out to about 200 watts per square meter. Now this wouldn’t leave death and flames in its wake, but it is about 4 times the occupational limit for microwave exposure. Stringent safeguards would have to be in place.
I’d love to see this technology becoming commonplace, but I don’t honestly see it happening until we find a cheap way to get to orbit. Maybe my other pet sci-fi dream of the space elevator will eventually come to pass and bring space solar along for the ride.