Energy Alternatives

A source of energy that has a theoretically unlimited supply and is not depleted when used by people is renewable energy. The fossil fuels that currently supply most of the world’s energy needs are nonrenewable. Presented here are several sources of energy that are renewable.

Biomass

Before the widespread use of fossil fuels, biomass was the principal energy source that supplemented animate power. Biomass fuel is derived from burning wood, plant material, and animal waste directly or converting them to charcoal, alcohol, or methane gas. Biomass remains an important source of fuel in some developing countries.

When carefully harvested in forests, wood is a renewable resource that can be used to generate electricity and heat. The waste from processing wood, such as for building construction and demolition, is also available. And crops such as sugarcane, corn, and soybeans can be processed into motor-vehicle fuels. Worldwide production of biomass fuel is approximately 3 quad BTUs, including one-third each in North America, Europe, and developing regions. Brazil makes extensive use of biomass to fuel its cars and trucks.

The potential for increasing the use of biomass for fuel is limited, for several reasons:

• Burning biomass may be inefficient because the energy used to produce the crops may be as much as the energy supplied by the crops.

• Biomass already serves essential purposes other than energy, such as providing much of Earth’s food, clothing, and shelter.

• When wood is burned for fuel instead of being left in the forest, the fertility of the forest may be reduced.

Hydroelectric Power

Generating electricity from the movement of water is called hydroelectric power. Hydroelectric is now the world’s second-most-popular source of electricity, after coal. Two-thirds of the world’s hydroelectric power is generated in developing countries and one-third in developed countries. A number of developing countries depend on hydroelectric power for most of their electricity.

Electricity from Hydroelectric Power

The most populous country to depend primarily on hydroelectric power is Brazil (Figure 11-50). Brazil has made considerable progress toward sustainable development by generating 80 percent of its electricity from hydroelectric power and 7 percent from other renewable sources. Among developed countries, Canada gets 60 percent of its electricity from hydroelectric power. The United States is a leading producer of hydroelectric power, but obtains only 8 percent of its electricity from that source. This percentage may decline because few acceptable sites to build new dams remain.

Hydroelectric Dam

The Itaipu Dam is on the Paraná River, between Brazil and Paraguay. The name refers to a small island in the river and means “stepping stone” in the local Guarani language.

Wind Power

The benefits of wind-generated power seem irresistible. Construction of a wind turbine modifies the environment less severely than does construction of a dam. And wind power has greater potential for increased use because only a small portion of the resource has been harnessed.

Despite its attractions, wind power has been harnessed in only a few places. China, North America, and Europe together account for nearly 90 percent of total world production. A significant obstacle for developing countries is the high cost of constructing wind turbines. One-third of the United States is considered windy enough to make wind power economically feasible .

Wind Power

Wind Power Potential

Winds are especially strong enough to support generation of power in the U.S. Plains states.

Hundreds of wind “farms” consisting of large numbers of wind turbines have been constructed across the United States (Figure 11-53). But wind power has divided the environmental community. Some oppose construction of wind turbines because they can be noisy and lethal for birds and bats. Some also find them a visual blight when they’re constructed in places of outstanding beauty.

Wind Farm

Idaho Falls, Idaho.

Geothermal Energy

Energy from hot water or steam is called geothermal energy. Natural nuclear reactions make Earth’s interior hot. Toward the surface, in volcanic areas, this heat is especially pronounced. The hot rocks can encounter groundwater and produce heated water or steam that can be tapped by wells.

Harnessing geothermal energy is most feasible at sites along Earth’s surface where crustal plates meet, which are also the sites of many earthquakes and volcanoes. The United States, the Philippines, and Indonesia are the leading producers of geothermal power. Ironically, in Iceland, named for its glaciers, nearly all homes and businesses in the capital Reykjavik are heated with geothermal steam.

Geothermal Power

Pause & Reflect 11.2.6

Does your local power company offer options for using alternative energy? Check the company’s website.