New Sweden wrote a diary recently regarding Florida's Andy Michaud and his advocacy of solar energy in his state. (Michaud is a Democratic candidate for Congress from Florida's 24th District.) So now I'm going to climb up on my soapbox and pontificate a little bit about solar power. Don't worry, I'll be kind.
Solar energy has several problems as a large-scale supplement for traditional fossil fuels. First of all, it's irregular. there needs to be some way to store the energy collected during the day for use at night. There needs to be some way to store the energy for use when it's cloudy. There needs to be some way to make it convenient.
Another major problem with solar energy is that it's diffuse. Historical trends are generally toward more compact, higher-density energy sources, such as wood -> coal -> oil. Turning to solar energy here at the surface of the Earth requires huge tracts of land to be converted to solar collector arrays, whether photovoltaic or thermal.
The more observant of you will have noticed I said "at the surface of the Earth" in the last paragraph. Since the late 1970's there have been various suggestions for space-based solar power. The simplest of these, a "soletta", is nothing more than a large orbiting mirror to reflect sunshine on the night side of the Earth. Most solar power satellite (SPS) ideas, however, are based on the concept of a large satellite collecting solar energy (with the advantages of no atmosphere to attenuate the energy and nearly constant sunshine) and sending that energy to receiving stations on the Earth's surface. That energy is most often in the form of microwaves (not in the same waveband as you find in a household microwave oven; that waveband suffers too much attenuation from water vapor in the atmosphere) received at a ground station called a rectenna (short for rectifying antenna) which converts those microwaves into electricity. The classical SPS concept involves large satellites in geosynchronous orbit and correspondingly large rectennas.
(Let me clear up a possible inconsistency here. I stated earlier that surface-based solar power installations required huge tracts of land to be used for collectors. Rectennas are mostly open space, similar to, say, a chain-link fence. The ground underneath is still usable.)
A couple of years ago, I came up with a variation on the classic SPS concept. Instead of large satellites in geosynchronous orbit, I envision a number of smaller satellites in lower orbits, similar to the Global Positioning System. Since any one of the satellites will only be in a position to beam power to a given rectenna for a relatively short period of time, it becomes necessary to have multiple satellites to provide continuous power. While this may sound like it will increase the costs of the system, it actually doesn't. Once the satellite is designed, any number can be built, leading to economies of scale. And once the concept has been proven, expanding the system becomes as easy as building more rectenna arrays.
Rectenna arrays (sometimes called rectenna farms) are collections of standard elements. A single rectenna element is (or can be) as simple as two pieces of copper wire and a diode. A rectenna farm would consist of huge numbers of these elements, easily in the tens of thousands and conceivably into the millions. Small-scale testing has shown that the efficiency of these rectenna elements is significantly increased by backing them with a metallic mesh, such as common hardware cloth. (Hardware cloth is a form of screen woven from steel wire with about half an inch between the wires.) So you see, rectenna farms aren't a matter of high technology, unlike the satellites themselves.
So where should we build something like this? I thought long and hard about the answer, particularly for the proof-of-concept phase. The parameters needed should be an uninhabited location such as a desert, and by preference near the Equator. Further consideration led to determining what to do with the generated power, and I began to think about the single most important need in the Third World: clean water. If we can use the generated power from the proof-of-concept to operate a desalinization plant, it would be a god idea to have the rectenna near a source of salt water such as an ocean. With these criteria in mind, I think a prime location would be the West African nation of Mauretania. There's a significant chunk of the Sahara Desert available; most of the country's population is concentrated along its Atlantic coast. There's easy access to the Atlantic and its huge quantity of salt water, and if the project is successful the standard of living in the country will improve dramatically: clean water means less water-borne disease and more agriculture. Depending on the scale of the project, some of that clean water can be exported to the rest of North Africa, spreading the benefits across the continent.
Okay, the floor is now open for comment. Anybody think this is worth pursuing?