No, they are much too unpredictable
Absolutely. At hydroelectric stations, for example, the power of gravity is harnessed to produce electricity.
Radiational heat
Coal Natural Gas Nuclear Hydro-Electric (Dams) Wind, Solar Geothermal
Nuclear fusion produces energy from the changes in the nuclear composition of the fuel, which is a mixture of deuterium and tritium. Essentially what happens is that some of the mass of the nuclei is...