Renewable Sources of Energy

active solar heating

Active solar systems capture the sun's energy, and then use pumps and fans to distribute the heat. Light hits the dark metal surface of a solar collector. There, it's converted into thermal energy. Water is pumped through pipes in the solar collector to absorb the thermal energy. The heated water then flows to a storage tank. Finally, the pumps and fans distribute the heat throughout the building.

geothermal energy

Below Earth's surface are pockets of hot liquid rock called magma. In some places magma is very close to the surface. In places such as Iceland and New Zealand, magma heats underground water to a boiling point. The hot water and steam can be valuable sources of energy in places like these. In Reykjavik, Iceland, 90% of homes are heated by water warmed underground in this way. Geothermal energy can also be used to generate electricity. Geothermal energy is an unlimited source of cheap energy. There are only a few places where magma comes close to Earth's surface. You would have to drill deep wells in other places to tap this energy, which would be very expensive. Geothermal energy is likely to play a part in meeting energy needs in the future.

hydrogen power

Hydrogen burns clearly, creates no smog or acid rain, and exists on Earth in large supply. Most of the hydrogen on Earth is combined with oxygen in water. Pure hydrogen can be obtained by passing an electric current through water. It takes more energy to get hydrogen than is produced by burning it. Hydroelectric plants decrease their activity when the demand for electricity is low. They could run at full capacity all the time, using the excess electricity to produce hydrogen. Excess energy from solar power plants could also be used to produce hydrogen. Scientists are looking for ways to produce hydrogen cheaply from water. Car manufacturers are now making cars that run on hydrogen fuel cells, which would produce water as emissions. The water could then be used again as fuel. If scientists can find a way to produce hydrogen cheaply, it could someday be an important source of energy.

Why hasn't solar energy hasn't replaced fossil fuels?

It's only available when the sun is visible and the energy Earth receives from the sun is spread out. You have to collect solar energy from a large area to get a useful amount of power.

What are the different ways a house can use solar energy?

Solar cells: active soar cells on the roof generate an electric current. A battery stores energy for night use. Passive interior heating: sunlight that passes through the windows is absorbed by the walls and floors and is converted to heat. At night, shades covering the windows prevent the heat from flowing back outside. Window design: large windows on the south and west side act as passive solar collectors. Solar water heater: water is pumped from a storage tank to an active solar collector on the roof. Sunlight heats the water, which is then returned to the tank. The water then heats pipes that heat the air throughout the house. Backup heat source: the house has a wood stove to provide backup heat on cloudy days.

solar cells

Solar energy can be directly converted into electricity in a solar cell. A solar cell has a negative and positive terminal, like a battery. When light hits the cell, an electric current is produced. Solar cells can be used to power some small devices, like calculators and lights. It would take more than 5,000 solar cells the size of your palm to provide electricity for a typical American home.

passive solar heating

Solar energy can only be used to power homes with passive solar systems. Passive solar systems convert sunlight into thermal energy, which is then distributed without using fans or pumps. Passive solar heating occurs to cars on sunny days. Solar energy passes through a car's windows and heats the seats and other parts of the car. These parts transfer heat to the air, and the inside of the car warms. The same principle can be used to heat homes.

solar energy

Solar energy is energy from the sun that is indirectly the source of most other renewable resources. Solar energy doesn't cause pollution and won't run out until the sun dies, which is billions of years away.

hydroelectric power

Solar energy is the indirect source of water power because it heats water on Earth's surface, forming water vapor. A dam is an example of hydroelectric power. A dam across a river blocks the flow of water, creating a body of water called a reservoir. When a dam's control gates are opened, water flows through tunnels at the bottom of the dam. As the water moves through the tunnels, it turns turbines, which are connected to a generator. Hydroelectric power is the most widely used source of renewable energy. Flowing water supplies a steady supply of energy. Once a dam and power plant are built, producing electricity is inexpensive and doesn't create air pollution. Most suitable rivers have already been dammed in the USA. Dams can have negative effects on the environment.

solar power plants

Solar power plants use rows of giant mirrors to focus the sun's rays to heat a tank of water. The water boils, creating steam, which can be used to generate electricity

What are some renewable sources of energy?

Some renewable sources of energy include water, the wind, biomass fuels, geothermal energy, hydrogen, and the sun.

How is geothermal energy used?

Step 1: Cold water is pumped below the Earth's surface Step 2: The magma heats the water Step 3: Steam rises to the power plant

What are the two ways the sun gives off energy?

The sun constantly gives off energy in t he forms of heat and light.

wind energy

Wind energy is an indirect form of solar energy. The sun heats Earth's surface unevenly, which causes different area of the atmosphere to have different temperatures and air pressures. The difference in pressure cause winds as air moves from one area to another. Wind can be used to turn a turbine and generate electricity. Wind farms consist of windmills. Together, the windmills generate large amounts of power. Wind is the fastest-growing energy source on Earth. Wind energy does not cause pollution and is the major source of power in places where fuels are hard to transport. Not many places have winds that blow steadily enough to provide enough energy and wind generators are noisy and can be destroyed by strong winds. Wind energy will become more important as fossil fuels become more scarce.

biomass fuels

Wood was one of the first fuels to be used for heat and light. Wood belongs to a group called biomass fuels. People are starting to use more biomass fuels as fossil fuel supplies shrink. Hawaiian sugar cane farmers burned sugar cane wastes to generate electricity when oil prices rose in the early 1970's. These wastes provided almost one fourth of the energy on the island of Kauai at one point. Biomass materials can be made into other fuels. Corn, sugarcane, and other crops can be used to make alcohol. Gasohol is a mixture of alcohol and gasoline that can be used as fuel for cars. Bacteria can produce methane gas when they decompose biomass materials in landfills. that methane can be used to heat buildings. Some crops, such as soybeans, can produce oil hat can be used as fuel, which is called biodiesel fuel. Biomass fuels are renewable resources, but they take time to be replaced. It takes time for new trees to replace those that have been cut down. Producing alcohol and methane in large quantities is expensive. This is why biomass fuels aren't widely used today in the USA. As fossil fuels become scarcer, biomass fuels may play a larger role in meeting energy needs.

energy sources

You are surrounded by energy sources in the woods. The sun warms the air, the wind blows, and the heat from inside Earth warms the waters of a spring. These sources of energy are all renewable-they are constantly being supplied. Scientists are trying to find ways to put these renewable energy resources to work to meet people's needs.

hydroelectric power definition

electricity produced by flowing water

biomass fuels definition

fuels made from living things, such as leaves, food wastes, and manure

geothermal energy definition

the intense heat from Earth's interior that warms magma