UNIT 4 Energy Sources

ENERGY SOURCES

Most of our energy comes from fossil fuels. Coal, oil and natural gas supply about 85 percent of US primary energy consumption. Although the supplies of these fossil fuels are vast, they are not unlimited. And more important, the earth's atmosphere and biosphere may not survive the environmental impact of burning such enormous amounts of these fuels. Carbon stored over millions of years is being released in a matter of decades, disrupting the earth's carbon cycle in unpredictable ways.

But fossil fuels are not the only source of energy, and burning fuel is not the only way to produce heat and motion. Renewable energy offers us a better way. Some energy sources are "renewable" because they are naturally replenished, because they can be managed so that they last forever, or because their supply is so enormous that they can never be meaningfully depleted by humans. Moreover, renewable energy sources have much smaller environmental impacts than fossil and nuclear fuels.

Our fossil fuels - coal, gas, oil - are quickly disappearing. This energy capital takes millions of years to replace. We must use less energy and find other energy sources.

Conservation of energy' can have two different meanings. One meaning is the saving of energy. We should not waste it. If we use our fuel sources carefully, they will last longer. Another meaning is that energy is neither created nor destroyed. This is the scientific meaning of conservation. It is the First Law of Thermodynamics.

As fossils disappear, we must find other sources of energy. Nuclear energy brings many dangers. We need to find other - and safer - sources of energy, e.g. the sun, the wind and the sea. These are called alternative energy sources.