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Renewable Energy Resources

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Acre upon acre of wind turbines stretch over the landscape in this photo. The blades of the turbines spin in the wind like giant pinwheels. The energy of the moving blades is used to generate useful electrical energy. Wind is one of several renewable energy resources.

Q: What are some other renewable energy resources?

A:  

What Are Renewable Resources?

Renewable resources are natural resources that can be replaced in a relatively short period of time or are virtually limitless in supply. In addition to wind, renewable energy resources include sunlight, moving water, biomass, and geothermal energy. All of these resources are freely available and won’t run out. Most of them also have the advantage of producing little if any pollution or carbon dioxide, which contributes to global climate change. Nonetheless, these energy resources are used far less than nonrenewable energy resources, especially fossil fuels. 

Wind

Wind is moving air, so it has mechanical energy that can do work. People have been using wind for energy for thousands of years. The old-fashioned windmill in the Figure below is one way that wind energy can be used. The wind turbines in the opening photo above are a much newer way of using wind energy. They change the kinetic energy of the wind to electrical energy. However, only certain areas of the world get enough steady wind to produce much electricity. Many people also think that wind turbines are noisy, dangerous to birds, and unattractive in the landscape. 

This old windmill uses wind energy to operate a mechanical pump that lifts water out of a well. Windmills like this one have been used for centuries.

Q: Where does the energy of the wind come from? Why does air move in the atmosphere?

A:  

Sunlight

The sunlight that reaches Earth is the planet’s most important source of energy. The energy in sunlight, called solar energy, is electromagnetic energy. This is a form of energy that travels through space in electric and magnetic waves. Solar energy can be used to heat homes and produce electricity in solar cells like those on the roof seen in the Figure below . Sunny areas receive plenty of sunlight to generate electricity, but solar energy may not be practical in areas that are often cloudy.

Solar panels on the roof of this family home generate enough electricity to supply the family’s needs.

Q: In addition to the roofs of homes and other buildings, where else can you find solar cells?

A:  

Moving Water

The mechanical energy of rapidly flowing water can turn a turbine and generate electricity. Electricity produced in this way is called hydroelectric power. The water may flow over a waterfall or through a dam. You can see a picture of a dam in the Figure below A drawback of dams is that they flood land upstream from the dam and reduce water flow downstream from the dam, and this can destroy ecosystems.

This is Hoover dam on the Colorado River between Arizona and Nevada. Water flowing through the dam generates electricity for both of these states and southern California.

Q: Does a hydroelectric power plant release air pollution or carbon dioxide? Why or why not.

A:  

Biomass

The stored chemical energy in organic matter or wastes is called biomass energy. The organic matter may be trees or other plants, or it may be wastes from homes and industries. When biomass is burned, it produces thermal energy that can be used for heating homes, cooking, or generating electricity. Biomass—especially wood—is an important energy source in the poorer nations where most people can’t afford fossil fuels. However, burning biomass releases air pollution and contributes to global climate change. Biomass can be used to make ethanol, a fuel that is added to gasoline. Although ethanol releases less pollution than gasoline, large areas of land are needed to grow the plants needed to make it (see Figure below ). This reduces the amount of land available for food production.

This large machine is harvesting and grinding plants to make ethanol.

Geothermal Energy

Geothermal energy is thermal (“heat”) energy from below Earth’s surface. It can be used to heat homes or generate electricity. A geothermal system pumps water underground where it is heated and then pumps the warm water back to the home or power plant (see Figure below ). The thermal energy of the water can be used directly to heat the home. Or it can be used to produce steam and generate electricity. Installing a geothermal system can be expensive because of the need to drill through underground rocks, but the energy it uses is free.

This power plant uses geothermal energy.

Summary

  • Renewable resources are natural resources that can be replaced in a relatively short period of time or are virtually limitless in supply.
  • Renewable energy resources include wind, sunlight, moving water, biomass, and geothermal energy. Except for biomass, which is burned, these renewable energy resources produce little if any pollution, although each has other drawbacks.

Vocabulary

  • renewable resource : Natural resource that can be replaced in a relatively short period of time or is virtually limitless in supply.

Review

  1. What is a renewable resource?
  2. List five renewable energy sources. What form of energy does each resource supply?

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