While many of the energy sources people rely on today are nonrenewable, scientists and engineers are increasingly exploring renewable energy resources as alternatives. Renewable energy resources come from natural processes that have been occurring for billions of years and will continue into the future. Energy from the sun, wind, water, and Earth’s interior is considered inexhaustible because it cannot be used up on a human time scale. However, each type of renewable energy source has both advantages and disadvantages.

One of the most widely used renewable resources is solar energy, which is the energy we harvest from the sun. Solar cells collect sunlight and convert it directly into electricity. In some homes, south-facing windows act as solar collectors, helping warm buildings. Although solar energy is clean and renewable, solar panels are expensive and require large surface areas to produce significant amounts of electricity. Solar energy is also limited on cloudy days and cannot be generated at night.

Another renewable resource is wind energy. Wind farms use large numbers of wind turbines to generate electricity. As wind turns the blades of a turbine, a generator produces electricity. Wind energy is nonpolluting and relatively inexpensive once turbines are installed. However, only certain regions have strong and steady winds, and electricity production can vary because the wind does not always blow.

In addition to energy from air movement, flowing water can produce power. Hydroelectric energy is created when moving water flows over dams and turns turbines. Another form of water energy is tidal energy, which uses the rise and fall of ocean tides to spin turbines and generate electricity.

Heat from inside Earth is another important renewable resource. Geothermal energy is energy obtained from hot magma or heated rocks deep beneath Earth’s surface. This heat can be used directly to warm homes or to produce electricity in geothermal power plants.

Finally, energy can also come from biomass, or organic material from living or once-living organisms. Biomass energy, also called biofuels, is produced by burning materials such as wood, food scraps, and plant products. Burning wood is the most common form of biomass energy, but it can cause pollution and disrupt natural habitats when trees are cut down. Some power plants burn garbage to generate electricity, though pollution and toxic ash can be a problem. Crops such as corn can also be converted into alcohol fuels like ethanol, although producing ethanol can require substantial energy.

Review:

1. What is a renewable energy resource?
2. List one advantage and one disadvantage to wind energy.
3. What is biomass energy?