Electrical Power Generation: Renewables—Solar and Wind
Solar and wind power have low power densities. Large areas will be required to generate the electrical energy that we are using right now. These energy sources are intermittent, although sunshine is reasonably predictable in desert climates. Even in these ideal locations, fixed rooftop PV can only be used to meet a relatively small proportion of total electrical demand. Solar thermal with molten salt storage has a higher efficiency, and can better match electrical demands in these places. For wind turbines to generate their advertised or rated power, winds have to be blowing at about 12 m/sec (20 kt or 24 mph). In the United States, except in mountain passes and the Texas panhandle, this does not appear to happen very often. A simple test of whether a given renewable energy source is practical is to check whether it can meet the electrical demands of a single house.