As Phil's recent post demonstrated, it's not easy being green. Sometimes there are unintended consequences (the Prius). Other times (powering your home with solar cells) it's prohibitively expensive.

Maybe not for long.

As they are currently manufactured, solar cells are not competitive - price/watt - with grid power. So it's no surprise that you don't see a lot of solar panels on rooftops. Current solar is used primarily to produce power in remote locations.

But MIT has come up with a way to make solar cells both cheaper and more efficient.

Today's solar cells already reflect some of the light that passes through the silicon. But the photonic crystal has distinct advantages. Conventional solar cells are backed with a sheet of aluminum. The photonic crystal reflects more light than the aluminum does, especially once the aluminum oxidizes. And the photonic crystal diffracts the light so that it reenters the silicon at a low angle. The low angle prevents the light from escaping the silicon. Instead, it bounces around inside; this increases the chances of the light being absorbed and converted into electricity.

As a result, the photonic crystal can increase the efficiency of solar cells by up to 37 percent, says Peter Bermel, CTO and a cofounder of StarSolar. This makes it possible to use many times less silicon, he says, cutting costs enough to compete with electricity from the grid in many markets.

The task now is to scale this up for commercial manufacture. And to do so, hopefully, in an environmentally friendly way.

Given the choice between green and dirty power at equal cost, most people will choose green power.