Here’s a seemingly simple solar power factoid: the sun bathes Earth with enough energy in one hour (4.3 x 1020 joules) to more than fill all of humanity’s present energy use in a year (4.1 x 1020 joules). So how to convert it? In the world of solar energy harvesting, there’s a constant battle between cost and efficiency. On the one hand, complex and expensive triple-junction photovoltaic cells can turn more than 40 percent of the (specially concentrated) sunlight that falls on them into electricity. On the other, cheap, plastic solar cells under development convert less than 5 percent.
Bringing the cost of just the photovoltaic cells down to about $1 per watt is the magic number solar manufacturers are aiming for, figuring that will make them cost-competitive with electricity produced by burning natural gas. Some manufacturers of thin film cells (less efficient but cheaper), such as First Solar, claim to have reached that mark, with efficiencies around 10 percent. Finding a way to further boost the ability to convert sunlight into electricity while also lowering costs to this level would herald the true dawn for solar power—something anticipated since photovoltaics were discovered.