Wind turbines. Enough to supply about 10.000 kWh or 10 MWh annually. "We built a 1000 watt wind turbine to help charge the battery bank that powers our offgrid home. It's a permanent magnet alternator, generating 3 phase ac, rectified to dc, and fed to a charge controller. The magnets spin with the wind, the coils are fixed, so no brushes or slip rings necessary." - MUCH cheaper. Just one foot. Designed to give to higher windspeeds, possibly by using a semi-flexible foot.
