Asked by: Ash Blair, Northumberland
A 2008 French study estimated that you could use piezoelectric devices, which generate power when they move, to extract 12 milliwatts from a raindrop. Over a year, this would amount to less than 0.001kWh per square metre – enough to power a remote sensor.
A better idea would be to collect the water and use it to drive a turbine. The UK receives just under a tonne of water per square metre per year. For a house with a 185m2 roof, this would amount to 3kWh of energy per year. With a 60 per cent conversion efficiency, it’s enough to run a 15W light bulb for 133 hours. That’s still a lot less than solar energy; we receive 60,000 times more energy per square metre from the Sun than from rain.