I, along with a lot of other people, have been watching the development of photovoltaic technologies with much interest over the past two years. For a lot of people, photovoltaics represent the holy grail of power generation, and for good reason. Almost all off the power we use currently comes from the Sun in one way or another (oil and coal are condensed plant matter from millions of years ago, the energy we get when we burn them is the energy that they stored through photosynthesis from the sun; nuclear power is a bit of a stretch, but when you get down to it, all elements heavier than hydrogen were produced through the fusion power of a star, including the fissionable materials we use for nuclear power generation). The only power sources that I can think of that don't harness the Sun's energy in one way or another are hydroelectric and tidal generation, which derive from gravity (which, I suppose, you could still say comes from the Sun because without the Sun the Solar System wouldn't have formed, but that's probably taking it a bit too far). So solar power, whether it be from photovoltaics, sterling engines, or some other technology is really just a means of cutting out the middle man. The sun puts out so much energy that once we have the technology to make solar power generation a large-scale reality, we'll basically have access to infinite energy (approximately 386 billion billion megawatts).

The reason we haven't started using large-scale solar power installations, of course, is that we haven't been able to get it to the point where it's cost-competitive with coal, oil, and nuclear. The number that's always been bandied about as the tipping point where solar power becomes viable is $1 per watt. That goal was reached, indeed exceeded, last month by Nanosolar who managed to bring the production cost of photovoltaics down from about $3 per watt to about 30¢ per watt. Their technology is now shipping, and being sold for a mere 90¢ per watt.

Essentially, this now means that we have access to limitless, cheap energy. Of course the problems of cloud cover and night time are still an issue when it comes to solar generation, but there are certainly ways around that. It's always daytime somewhere on the Earth, so enough solar plants spread around the Earth will allow us to generate power 24 hours a day. And there are always places where cloud cover is essentially non-existent, basically all the large deserts around the world. The true holy grail of power generation, though, is power generation satellites. Once we put large photovoltaic arrays outside of Earth's atmosphere, we have an unobstructed view of the sun forever. Microwave power transmission can then beam that power down to Earth's surface, although there are obviously some issues there. One of personal favorite ideas is to combine the idea of solar power satellites with the idea of a space elevator: basically a giant tower that pokes up out of the Earth's atmosphere and has a huge array of solar panels at the top so that we can just transmit the power down the tower on wires; if we wanted to get really crazy we could build an entire ring of solar panels that completely encircles the Earth with multiple elevators connected to it serving as distribution nodes. That, of course, solves multiple problems at once but is sadly beyond our current technological abilities.

Science fiction aside, though, we have reached an important point in the history of human technology: the point where limitless, safe, clean energy is in reach.