Some renewable energy ideas are complicated — it'd take a PhD to explain the biochemical ins and outs of cellulosic ethanol. But others are simple — like concentrated solar photovoltaic. If you've ever used a magnifying glass to focus the sun's light and burn an unfortunate ant, you've got the gist of it. CSPV plants uses mirrors or lenses to concentrate the sun's light on an array of solar PV panels, vastly increasing the amount of electricity that can be produced. It's a cheap way to multiply solar power; instead of producing lots of expensive PV panels, you can get the same amount of electricity with relatively cheap mirrors. Only a few CSPV plants are in operation, including a 500-kilowatt test plant from the company SolFocus in Spain, but more are on the way. One of the most innovative ideas comes from a start-up called CoolEarth Solar, which uses thin-film plastic lenses, blown up like a balloon, to cheaply concentrate the sun's rays.