Skip to main content icon/video/no-internet
icon backReturn to Entries

Renewable Energy

The term renewable energy describes sources of energy that exist within the natural environment including the sun, wind, water, plant material, and geothermal heat. These sources are either continuously available, like heat from the sun, or are rapidly replaced after their depletion, like wood. Renewable energy is also considered clean energy. It generally does not produce carbon dioxide or other harmful pollutants or wastes. Renewables such as hydropower and wood already contribute 15 percent of total world energy production. The so-called “new renewables,” including solar and wind, while accounting for only 2 percent of energy production, are the fastest-growing sources of energy. Since the early 1990s installed capacity of both solar power and wind energy has increased by more than 20 percent annually. With concerted action, renewable energy technologies have the potential to meet half or more of the world's energy needs within a few decades.

Hydropower

Hydropower is the most successful type of renewable energy. Humans have been using the power of flowing rivers for centuries to grind flour and turn rudimentary machinery. Hydro has been used to produce electricity for over 100 years. Rivers are dammed, impounding water in reservoirs, which is then used to turn turbines. Hydro produces 17 percent of the world's total electricity, 10 percent of U.S. electricity, and more than 90 percent of electricity in Norway and Iceland. Forty other countries get more than 50 percent of their electricity from hydro. The cost of hydropower is low and is competitive with the cheapest fossil fuels. Hydro is a domestic source of energy, which is especially beneficial for less-developed countries faced with importing expensive oil. Dam projects have other benefits such as flood control, irrigation, recreation, and municipal water supply. Hydropower has a number of drawbacks, including the loss of farmland, displaced people, and the destruction of habitat and fisheries. Droughts pose another problem, and silt can dramatically reduce the life of a reservoir.

The Three Gorges Dam on the Yangtze River in China is the world's largest dam project. It will produce 10 percent of China's electricity, thus reducing dependence on dirty coal. However, the reservoir has displaced 1.5 million people and resulted in the loss of 115,000 acres of farmland, showing that hydro is not always benign. Nevertheless, the potential for hydropower is vast, especially in poorer countries. In rich countries, high construction costs and political opposition mean that fewer large dams are likely to be built in the future.

Solar Power

Solar power uses the energy of the sun for heating and to produce electricity. There are four main types of solar energy systems. Passive solar relies on the design of structures to capture heat in the winter and to keep spaces cool in the summer. For example, a greenhouse is heated by the sun. A well-designed passive system can provide nearly 100 percent of the space heating for a home. Active solar systems are most commonly used to heat water and swimming pools. They rely on flat plate collectors, generally mounted on rooftops, to circulate and heat water. Photovoltaic systems use silicon wafers or chips to convert sunlight directly into electricity. Calculators use photovoltaic cells, as do panels on homes and in places not connected to power lines. Solar thermal electric systems heat water to produce steam to generate electricity. A commercial plant in the Mojave Desert of California uses a series of curved mirrors that track the sun to produce enough power to supply electricity to 170,000 homes.

...

  • Loading...
locked icon

Sign in to access this content

Get a 30 day FREE TRIAL

  • Watch videos from a variety of sources bringing classroom topics to life
  • Read modern, diverse business cases
  • Explore hundreds of books and reference titles

Read next

More like this

Sage Recommends

We found other relevant content for you on other Sage platforms.

close

Have you created a personal profile? Login or create a profile so that you can save clips, playlists and searches

close
close
close Signed In to profile You are signed in as:
close
Logged in Institution Institution