More and more scientists today agree that global warming is a serious issue and that the cause of global warming is carbon dioxide released into the atmosphere when fossil fuels are burned. Politicians, too, are being swayed as they see increases in property damaged, injuries, and even deaths due to natural catastrophes which appear to have gotten worse in recent decades.

Because fossil fuels appear to be the source of worldwide atmospheric change, people have began to look to other methods of producing energy. In addition to causing atmospheric change, there's the reality that we will run out of fossil fuels. The world's economy is based on fossil fuels but they are a finite resource. Eventually we will run out of them. Fossil fuels are not a sustainable resource. Two methods of producing energy which have little impact on the environment and are sustainable are solar and wind power.

First, we'll take a look at solar power. Solar power is, of course, power derived from the energy of the sun's rays. The limitation with this energy source is the sun itself. The sun will never run out, except at night. Solar power sources have been designed to compensate for the downtime of night or cloudy days, but solar power works best in sunny climates.

Solar power is generally used in one of three ways: to generate heat, to generate electricity, and to desalinate salt water. Solar powered heating systems are usually either active or passive in design. An active solar heating system uses pumps to circulate water which has been heated by the sun. Passive solar heating systems use the nature of water to create circulation. This method relies on the fact that heat energy wants to move into areas of lesser heat.

In generating electricity, solar power is harnessed by photovoltaic cells which convert the suns energy into electricity. These cells have been widely used to power calculators for decades. In solar desalination, the power of the sun is used to evaporate water to separate it from the salt and other undesirable minerals.

Another type of clean, renewable power comes from the wind. Wind power, while growing in popularity, still accounts for barely 1% of the world's power supply. This is hard to believe considering how much the wind blows! Wind power is usually harnessed using wind turbines.

A centuries old version of harnessing wind power is the windmill. These lovely structures used the wind to grind grains and pump water. Today's wind turbines are advanced machinery employing the latest technologies.

More and more "wind farms" are sprouting up around the world. These huge arrays of wind turbines can be found on land and offshore. The biggest ones in the US are land-based farms in California, Oregon, and Washington. There are also more and more popping up the Midwest. Because of energy costs and damage done to the environment, alternative energy sources are receiving a great deal of interest. Two of the most promising are solar and wind power.