They are often useful for heating water and for space heating. But we cannot rely on them any time soon to replace all our present sources for making electricity. Also, much more time is needed to develop some of these technologies for large-scale use. Let's look at some of the most appealing of these alternatives. Hydroelectric or water power in the U.S. is being used as much as possible now.
Solar power is a diffused energy source - it is available only when the sun shines.
Although some energy can be stored in energy cells, the technology for storing large amounts is still in its infancy. Wind power also is a diffused energy source. It is available only in some parts of the country and only when the wind blows consistently. Geothermal energy is found at only a few special locations. Other possible energy sources are methane from land fills and from burning garbage.