Renewable energy refers to sources of energy that are always there. While this energy must be finite, due to entropy and the laws of thermodynamics, the supply is so large that there is no foreseeable end in our or our children's lifetimes. Solar energy is one of the most common examples. The sun comes up every day and hopefully will continue to do so for another 5 billion years or so.

You might think that we would be tapping these energy resources, but there is a catch. While the energy is there, the cost of getting it is actually greater than using our more popular energy sources of fossil fuels and uranium. As we run out of our supply of fossil fuels and uranium or the cost of these fuels rises for economic or political reasons, the cost of renewable energy may become much more competitive.

The other important advantage of renewable energy is that it produces much less pollution. Some people believe that if the true costs of pollution, like the medical costs of cancer, were factored into the cost of fossil fuels and uranium, that renewable energy is already cost effective and should be used much more often.

Another requirement to make renewable energy more competitive is more research. The United States government has cut funding for research into solar and other renewable energy. This has left the United States even more likely to be dependent on oil imports far into the future.

Following is a graph that shows the % of our total energy provided by renewable energy.

Courtesy of Renewable Energy Annual web site

A number of renewable types of energy are listed below along with a brief description.

Solar Energy

Solar energy is provided by the light energy that comes from the sun. There are a number of ways to harness this energy. There is direct solar heating in which the light energy is allowed to heat a house through transparent windows or heat a mass of water which can then be circulated to heat the home. There is photovoltaics where the light energy is transferred into electrical energy by the use of solar panels. For example, these panels can be attached to the roof of a house. Also many satellites use solar panels for their power needs. Finally there is thermal electric energy where the sun light is reflected and focused using a huge parabolic mirror. This reflected light energy can then be used to heat water to create steam which can be used to drive a turbine to produce electricity just like in a conventional power plant. Some areas of the country are more conducive to the use of solar energy than others. Areas like the southwest where the sun is shining most of the time and the temperatures are seldom very low are the best candidates.

Over the years the efficiencies of solar cells, which are not very high, have been increasing. If these efficiencies could be increased further, then solar energy could become competitive as an energy resource.

One way that you can utilize solar energy is to buy a solar calculator. You will never have to buy batteries again, which not only saves energy but also the pollution involved with disposing of the batteries.

Wind Energy

Wind energy is the kinetic energy contained in the movement of a mass of air molecules. The wind can be used to turn a turbine, which can then produce electricity using a generator. Many wind turbines are relatively small, and large numbers are required to produce appreciable amounts of energy. Again, certain areas of the country are particular suitable for wind turbines. The coast of California, for example, has cliffs that receive high winds on a consistent basis.

A number of wind turbines, together referred to as wind farms, have been constructed in the state of Pennsylvania. Residents there can choose to purchase some or all of their electricity from these wind farms, thereby saving pollution that would be created if the electricity was generated from fossil fuels. Similar programs may be available in your local area.

Biomass Energy

Biomass energy is generated by the decay of large masses of plant or animal material or waste which forms methane and other combustible gases. These gases contain chemical energy, which when burned can be used to generate electricity. Gas can even be extracted from large landfills, where the waste deposits that are part of the landfill generate the gas over time.

Geothermal Energy

Geothermal energy is heat energy that comes from the molten interior of the earth. There are places where this molten material is close enough to the surface where it can be harnessed. The heat energy is used to produce steam and as usual turns a turbine to generate electricity.