There are essentially four types of alternate energies that we are currently focusing on. They are solar, wind, hydroelectric and geothermal. Massive amounts of research and development are taking place in the developed nations of the world towards getting self-reliant in terns of energy requirements for the future. This article discusses briefly about two such types, hydroelectric and geothermal energies:  

• Over and above the sun and the wind, water too yields immense of power which can be harnessed to generate electricity to light and heat our homes. Today we know how to harness its force, in response to gravity, meaning the force of water as it flows downhill and put them in turbines which then produce electricity. Though forceful water is not difficult to find, producing hydroelectric energy is both expensive and complicated. We can only control water energy if we construct dams, which again is an expensive proposition. We need to store as well as control the kinetic energy produced by flowing water and then convert it to electrical energy. Of course a dam is not always a necessity when you are thinking of producing electricity to light a city or a densely populated area. Today there are smaller run-of-river hydroelectric energy converters which produce adequate electricity to light homes as well as offices.

• One of the most under-appreciated and untapped sources of alternate energy is geothermal energy, which lay dormant as heat energy under the surface of the earth. This heat forms steam which then comes out of vents on the surface of the earth. Geothermal energy plants draw out this hot steam, called 'dry steam'. The plants are also called 'flash' power plants or 'binary' power plants. The reason why the hot water from below the surface of the earth is drawn up is to gather the steam power. On of the best known geothermal sites is The Geysers, located 100 miles north of San Francisco, which is an ideal example of a dry steam plant.