July 28, 2008 While rooftop solar panels have understandably been the main focus for household solar energy breakthroughs, Tokyo-based Nihon Telecommunication System Inc. has given householders another option to do their bit to help the planet by developing windowpanes with built-in photovoltaic cells.

The solar cells have a power generation efficiency of 7 to 8% and, due to the thickness of the glass (10.5mm), up to 90% of sunlight is prevented from coming into a room, thus providing the added benefit of reducing air conditioning costs. On a sunny day, the windowpanes generate up to 70 watts of electricity per square meter of glass.

The company claims this is enough to power a PC or charge a mobile phone. Thing is, we're not sure how you're supposed to do charge either device without a traditional power outlet - the windowpane can only provide power via a USB port.

Source: Crunchgear