Increasingly of late, I keep reading about nanotechnology being the key to solar power's breakthrough. A good place to follow this sort of story by the way is here - a website dedicated to news about nanotech with a sizeable section on solar nanotechnology.

I know there is a constituency out there that believes that solar is some kind of miracle energy source just around the corner. There has indeed been a feverish following of nanotechnology since the publication of Eric Drexler's 1986 book "Engines of Creation - the Coming Era of Nanotechnology". Sorry to spoil the party, but there are however a few hard facts that can't be ignored;

i) Today, solar photovoltaic power delivers a load factor of 10% in countries like Germany that can afford it.
ii) That's because there is no solar power at night and actually very little during cloudy days and winters in Europe
iii) It's a great mistake to concentrate on the manufacturing production cost per watt of this or that solar technology. In the long run, all that matters is the installed cost per watt and that remains high - $6 - $9 per watt.
iv) If you had the technology to produce solar power at a quarter of the cost of everyone else, would you sell it at that price too?
v) Solar power will not make the massive breakthrough until it reaches an installed cost of $1 - $2 per watt. Don't bet on that happening any time soon.

In that vein, I have just started leafing through my well-worn copy of Ray Kurzweil's "The Singularity is Near" again. A wonderfully optimistic book from a brilliant futurist who has a record of getting most things right. Yet looking at it again, I'm reminded that the world is full of broken promises about falling costs in solar power. On page 250 of the book, he quoted Martin Roscheisen of Nanosolar, who " . . . estimates that his technology has the potential to bring down solar-power costs to around fifty cents per watt by 2006, lower than that of natural gas. Competitors Nanosys and Konarka have similar projections."

Well, needless to say, this hasn't happened. I tend to think there is far more potential in the medium term for Concentrated Solar Power (mirrors heating up molten salts in deserts), an off the shelf cheaper technology that works and delivers industrial quantities of power, especially in what the Economist recently labelled the Dark Continent - because at night, unlike other developed continents, almost the whole of Africa remains dark, unlit by electricity.