Solar energy offers a convenient energy source which is also environmentally friendly. Solar energy is the energy harnessed or tapped from the sun. The sun's rays are converted into usable energy by devices such as photovoltaic cells and solar panels. Energy from the sun can also be stored in batteries and is used as a backup power source. Solar energy is advantageous as it is usable in areas where there is no main source of electricity. However, the initial cost of harnessing solar power could prove to be a major disadvantage.
Geothermal energy is produced from hot underground water flowing in the crust of the Earth. Generators and turbines can be used to harness this energy. As the water passes, it makes the turbine rotate, thus powering the generators. The energy can also be harnessed directly or by the use of geothermal heat pumps. Geothermal energy is generally inexpensive to harness, but this resource is sparse and difficult to find.
Wind energy has been in use since the ninth century to mill grain and pump water. It is harnessed through use of windmills, which generate power when the wind rotates the blades. Wind energy is used both for individual homes and to power entire regions. Wind energy is a clean source of energy as it does not pollute the environment. Wind energy, though, has disadvantages in that wind mills do not turn when there is no wind. Also, windmills are expensive to erect, making wind power an expensive option.
Hydro power is energy tapped from water bodies, such as by use of dams. Turbines and generators harness hydro power. When the water flows upon the turbine, its blades rotate and power the generator and energy is produced. The power is then transmitted to power lines and is distributed to homes, offices and industrial plants. Hydro power, though a cleaner alternative to petroleum, is very expensive to run and maintain.