Inventions that take the breath away with their simplicity and elegance are rare. The new rechargeable batteries from USBCell qualify for this honour. As their name indicates, they are AA batteries that are recharged by the USB port on a laptop or other powered device. They are not cheap, but will repay the investment by being far easier to recharge than conventional rechargeable AAs. The carbon savings from these batteries are not large. My calculation is that they might save 10kg of CO2 a year in a household full of portable devices. But they will, of course, reduce the waste going into landfill.

The company that makes the batteries has won some important awards for its innovation. More importantly, it also has some extremely interesting views on the evolution of home electricity demand. It correctly points out that a larger and larger fraction of home energy is used in 12V, not 240V appliances. We waste a lot of energy switching 240V AC down to 12V DC. Its next products include a box that will allow all DC devices (phones, handheld consoles, laptops) to be efficiently charged. Eventually, it will be possible to use cheap(-ish) solar power collectors to charge all the battery DC devices in the home. The savings in carbon would be worthwhile (but probably outweighed by the purchase of one extra TV).