Can you imagine life without television, cars, or computers? What if you had to cook your dinner over a fire or fetch water from a river? It might be fun for a camping trip, but you probably would not want to do it every day. But that's how life was before scientists and inventors discovered ways to use energy to make our lives easier.

Today, most of the energy we use comes from fossil fuels. Coal, oil, and natural gas are all fossil fuels. Over millions of years, the decay of plants, dinosaurs, and other animals was formed into fossil fuels. These fuels lie buried between layers of earth and rock. The only way to get them out is to drill or mine for them. While fossil fuels are still being created today by underground heat and pressure, they are being consumed more rapidly than they are created. For that reason, fossil fuels are considered nonrenewable; that is, they are not replaced as soon as we use them. So, we could run out of them sometime in the future. Or, we might someday use so much fossil fuel that we won't be able to drill or mine fast enough to keep up with the demand.

Because our world depends so much on energy, we need to find sources of energy that will last a long time. What if there was a type of energy that never ran out? There is. It is called renewable energy.

In addition, because there are so many people on the earth using fossil fuels, we create a lot of pollution. So, we should also use energy sources that produce as little pollution as possible. While all energy sources cause some pollution in their creation or their consumption, renewable energy systems generally are less polluting than fossil fuel systems.

What is renewable energy?

Renewable energy systems use resources that are constantly replaced and are usually less polluting. Examples of renewable energy systems include solar, wind, and geothermal energy (getting energy from the heat in the earth). We also get renewable energy from trees and plants, rivers, and even garbage.

Wind power
Did you know that wind is considered an indirect form of solar energy? This is because the wind is driven mainly by temperature differences on the surface of the earth that are caused by sunshine.Now, people use the wind to generate electricity. The windmills built long ago had many blades, but today's wind turbines usually have just two or three blades that turn when the wind blows. The blades drive a generator that produces electricity, much like steam turbines. Read more about wind power

The water in rivers and streams can be captured and turned into hydropower, also called hydroelectric power. The most common form of hydropower uses dams on rivers to create large reservoirs of water. Water released from the reservoirs flows through turbines, causing them to spin. The turbines are connected to generators that produce electricity.
Hydropower is also inexpensive, and like many other renewable energy sources, it does not produce air pollution.

However, the drawback to hydropower is that damming rivers can change the ecology of the region. For example, the water below the dam is often colder than what would normally flow down the river, so fish sometimes die. The water level of the river below the dam can be higher or lower than its natural state, which affects the plants that grow along the riverbanks.

Biomass energy
When you burn a log in your fireplace or in a campfire, you are using biomass energy. Because plants and trees depend on sunlight to grow, biomass energy is a form of stored solar energy. Although wood is the largest source of biomass energy, we also use corn, sugarcane wastes, and other farming byproducts.

There are three ways to use biomass. It can be burned to produce heat and electricity, changed to a gas-like fuel such as methane, or changed to a liquid fuel. Liquid fuels, also called biofuels, include two forms of alcohol: ethanol and methanol. Because biomass can be changed directly into a liquid fuel, it could someday supply much of our transportation fuel needs for cars, trucks, buses, airplanes, and trains.

Solar energy
We can use the energy in sunshine to warm and light our homes, heat our water, and provide electricity to power our lights, stoves, refrigerators, and other appliances. This energy comes from processes called solar heating, solar water heating, photovoltaic energy (converting sunlight directly into electricity), and solar thermal electric power (when the sun's energy is concentrated to heat water and produce steam, which is used to produce electricity). Read more about solar energy

Geothermal energy
We can also get energy directly from the heat in the earth. This is known as geothermal energy, from "geo" for earth and "thermal" for heat. Read more about geothermal energy

Energy from wastes
What you may throw out in your garbage today just might become fuel for someone else. That's right, whether you call it trash or garbage, this municipal solid waste has the potential to be a large energy source.

Garbage is also an inexpensive energy resource. Unlike most other energy resources, someone will collect garbage, deliver it to the power plant, and pay to get rid of it. This helps cover the cost of turning the garbage into energy. Garbage is also a unique resource because we all contribute to it.

Renewable energy in your future
One day, all your home's energy may come from the sun or the wind. You may not think twice about filling your car's gas tank with biofuel. And your garbage might contribute to your city's energy supply. As scientists push the limits of renewable energy technologies and improve the efficiencies and costs of today's systems, we will soon be to the point when we may no longer rely mostly on fossil fuel energy.

USA - Department of Energy
Energy Efficiency and Renewable Energy


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Glossary for Renewable Energy Sources
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Wind Turbine




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Solar Element


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