This fascinating article in The Guardian compares the average power per square metre that different types of renewable energies produce. It turns out that dams are rubbish (and the piece rubbishes China’s Three Gorges dam project) in terms of the space they consume–and many renewable energies seem to need vast tracts of land to produce enough power.
Hydroelectric energy is the least efficient way of using land to produce power. One square metre on average produces 0.1 watts.
A generator burning biomass requires crops from 250,000 hectares to match the electricity output of a nuclear power station.
Wind farms generate around 1.2 watts for every square metre of land.
Photovoltaic cells covering an area of 150,000 square kilometres would be needed to meet US electricity needs for a year. To power New York city would take 12,000 square kilometres, about the size of Connecticut.
All this is the same kind of argument that Greenbang made recently, after hearing about the “world’s biggest solar farm”.