Earth in a HandIn many countries today, quite a lot is being said about harnessing renewable energy technologies – particularly in light of the rising oil prices. But some people might still be wondering exactly what renewable energy is.

Renewable energy is power which has been generated from renewable resources – in other words, it does not “run out” or eventually become depleted.  It can be continuously re-created.

It’s not just the prices of oil that has people searching for clean and renewable energy sources.  Global warming concerns, and international pollution problems, have triggered this concern as well.  Governments around the world have begun to support research on improving the renewable energy technologies.

Currently, the five common renewable energy sources are biomass, hydropower, geothermal heat, wind, and solar power.


Biomass consists of organic material which has been produced by animals and plants.  Biomass energy uses  stored energy from the sun.  This is a result of the natural process which any plant uses to survive – photosynthesis.

Because we can always grow new crops and trees, biomass is considered a form of renewable energy.  Furthermore, organic waste can be used to create biomass as well.

Some commonly used biomass fuels include crops, wood, garbage, and manure.  When these materials are burned, they emit heat which produces steam, that can in turn be used to create electricity.  Some biomasses are converted into other usable energy forms, such as methane gas or biodiesel.


Hydropower is one of the oldest forms of renewable energy.  It  was used in ancient times to grind grain.  Coal was once the only source of power in the United States.  But in 1880, the first Hydropower plant was built, and since then, more of these have been erected in order to provide the people with electricity.

Geothermal Energy

Geothermal Energy comes from within the Earth itself.  The steam or heat which comes from the center of the earth can be used to regulate the temperatures of buildings, and to generate electricity as well.
This is considered one form of renewable energy because water can always be replenished by rain, and because the earth’s core maintains its temperature.

Wind Power

Even the ever-present wind can provide a renewable energy source.  Wind is created because the uneven heating on the earth’s surface causes the air to move.  Thus, wind power is essentially a bi-product of solar power.  Wind propellers are used to collect the wind’s kinetic energy, which turns turbines that are in turn used to create electricity.

Solar Power

This form of renewable energy will be available as long as the sun shines.  Solar energy can either be used as thermal energy, or it can be converted into electricity.

As a thermal energy, it can be used to heat water or spaces.  Through the use of solar cells or similar photovoltaic devices, it can be used to create electricity.  The heat of the sun can also be used to create steam, which turns turbines and thus produces electricity.