RENEWABLE ENERGY
What is renewable energy?
Renewable energy is energy produced from sources like the sun and wind that are naturally replenished and do not run out. Renewable energy can be used for electricity generation, space and water heating and cooling, and transportation.
Non-renewable energy, in contrast, comes from finite sources that could get used up, such as fossil fuels like coal and oil.
Renewable energy is energy from sources that are naturally replenishing but flow-limited; renewable resources are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time.
Renewable energy is energy derived from natural sources that are replenished at a higher rate than they are consumed. Sunlight and wind, for example, are such sources that are constantly being replenished. Renewable energy sources are plentiful and all around us.
Fossil fuels - coal, oil and gas - on the other hand, are non-renewable resources that take hundreds of millions of years to form. Fossil fuels, when burned to produce energy, cause harmful greenhouse gas emissions, such as carbon dioxide.
Generating renewable energy creates far lower emissions than burning fossil fuels. Transitioning from fossil fuels, which currently account for the lion’s share of emissions, to renewable energy is key to addressing the climate crisis.
Renewables are now cheaper in most countries, and generate three times more jobs than fossil fuels.
Advancing Renewable Energy in The United States
Other Renewable Energy Sources
Types of Renewable Energy
Renewable energy sources, such as biomass, geothermal resources, sunlight, water, and wind, are natural resources that can be converted into these types of clean, usable energy:
Benefits of Renewable Energy
The advantages of renewable energy are numerous and affect the economy, environment, national security, and human health. Here are some of the benefits of using renewable energy in the United States:
- Enhanced reliability, security, and resilience of the nation’s power grid
- Job creation throughout renewable energy industries
- Reduced carbon emissions and air pollution from energy production
- Increased U.S. energy independence
- Increased affordability, as many types of renewable energy are cost-competitive with traditional energy sources
- Expanded clean energy access for non-grid-connected or remote, coastal, or islanded communities.
Learn more about the advantages of wind energy, solar energy, bioenergy, geothermal energy, hydropower, and marine energy, and how DOE is working to modernize the grid.
Advancing Renewable Energy in the United States
EERE offers funding for research and development to advance clean energy technologies. Find open funding opportunities and learn how to apply for funding.
DOE's 17 national laboratories conduct research and help bring renewable energy technologies to market.
Renewable Energy at Home
Homeowners and renters can use clean energy at home by buying green power, installing renewable energy systems to generate electricity, or by using renewable resources for water and space heating and cooling.
Before installing a renewable energy system, it's important to reduce your energy consumption and improve your home’s energy efficiency.
Visit Energy Saver to learn more about the different ways to use renewable energy at home:
SOURCES OF RENEWABLE ENERGY:
SOLAR ENERGY
Solar energy is the most abundant of all energy resources and can even be harnessed in cloudy weather. The rate at which solar energy is intercepted by the Earth is about 10,000 times greater than the rate at which humankind consumes energy.
Solar technologies can deliver heat, cooling, natural lighting, electricity, and fuels for a host of applications. Solar technologies convert sunlight into electrical energy either through photovoltaic panels or through mirrors that concentrate solar radiation.
Although not all countries are equally endowed with solar energy, a significant contribution to the energy mix from direct solar energy is possible for every country.
The cost of manufacturing solar panels has plummeted dramatically in the last decade, making them not only affordable but often the cheapest form of electricity. Solar panels have a lifespan of roughly 30 years, and come in variety of shades depending on the type of material used in manufacturing.
WIND ENERGY
Wind energy harnesses the kinetic energy of moving air by using large wind turbines located on land (onshore) or in sea- or freshwater (offshore). Wind energy has been used for millennia, but onshore and offshore wind energy technologies have evolved over the last few years to maximize the electricity produced - with taller turbines and larger rotor diameters.
Though average wind speeds vary considerably by location, the world’s technical potential for wind energy exceeds global electricity production, and ample potential exists in most regions of the world to enable significant wind energy deployment.
Many parts of the world have strong wind speeds, but the best locations for generating wind power are sometimes remote ones. Offshore wind power offers tremendous potential.
GEOTHERMAL ENERGY
Geothermal energy utilizes the accessible thermal energy from the Earth’s interior. Heat is extracted from geothermal reservoirs using wells or other means.
Reservoirs that are naturally sufficiently hot and permeable are called hydrothermal reservoirs, whereas reservoirs that are sufficiently hot but that are improved with hydraulic stimulation are called enhanced geothermal systems.
Once at the surface, fluids of various temperatures can be used to generate electricity. The technology for electricity generation from hydrothermal reservoirs is mature and reliable, and has been operating for more than 100 years.
HYDROPOWER
Hydropower harnesses the energy of water moving from higher to lower elevations. It can be generated from reservoirs and rivers. Reservoir hydropower plants rely on stored water in a reservoir, while run-of-river hydropower plants harness energy from the available flow of the river.
Hydropower reservoirs often have multiple uses - providing drinking water, water for irrigation, flood and drought control, navigation services, as well as energy supply.
Hydropower currently is the largest source of renewable energy in the electricity sector. It relies on generally stable rainfall patterns, and can be negatively impacted by climate-induced droughts or changes to ecosystems which impact rainfall patterns.
The infrastructure needed to create hydropower can also impact on ecosystems in adverse ways. For this reason, many consider small-scale hydro a more environmentally-friendly option, and especially suitable for communities in remote locations.
OCEAN ENERGY
Ocean energy derives from technologies that use the kinetic and thermal energy of seawater - waves or currents for instance - to produce electricity or heat.
Ocean energy systems are still at an early stage of development, with a number of prototype wave and tidal current devices being explored. The theoretical potential for ocean energy easily exceeds present human energy requirements.
BIOENERGY
Bioenergy is produced from a variety of organic materials, called biomass, such as wood, charcoal, dung and other manures for heat and power production, and agricultural crops for liquid biofuels. Most biomass is used in rural areas for cooking, lighting and space heating, generally by poorer populations in developing countries.
Modern biomass systems include dedicated crops or trees, residues from agriculture and forestry, and various organic waste streams.
Energy created by burning biomass creates greenhouse gas emissions, but at lower levels than burning fossil fuels like coal, oil or gas. However, bioenergy should only be used in limited applications, given potential negative environmental impacts related to large-scale increases in forest and bioenergy plantations, and resulting deforestation and land-use change.
For more information on renewable sources of energy, please check out the following websites:
International Renewable Energy Agency | Renewables
International Energy Agency | Renewables
Intergovernmental Panel on Climate Change | Renewable Sources of Energy
UN Environment Programme | Roadmap to a Carbon-Free Future
Sustainable Energy for All | Renewable Energy
The wind, the sun, and Earth are sources of renewable energy. These energy sources naturally renew, or replenish themselves. Wind, sunlight, and the planet have energy that transforms in ways we can see and feel. We can see and feel evidence of the transfer of energy from the sun to Earth in the sunlight shining on the ground and the warmth we feel when sunlight shines on our skin. We can see and feel evidence of the transfer of energy in wind’s ability to pull kites higher into the sky and shake the leaves on trees. We can see and feel evidence of the transfer of energy in the geothermal energy of steam vents and geysers. People have created different ways to capture the energy from these renewable sources.
Solar Energy
Solar energy can be captured “actively” or “passively.” Active solar energy uses special technology to capture the sun’s rays. The two main types of equipment are
I. photovoltaic cells (also called PV cells or solar cells) and
II. mirrors that focus sunlight in a specific spot.
These active solar technologies use sunlight to generateelectricity, which we use to power lights, heating systems, computers, and televisions. Passive solar energy does not use any equipment. Instead, it gets energy from the way sunlight naturally changes throughout the day. For example, people can build houses so their windows face the path of the sun. This means the house will get more heat from the sun. It will take less energy from other sources to heat the house. Other examples of passive solar technology are green roofs, cool roofs, and radiant barriers.
· Green roofs are completely covered with plants.
· Plants can get rid of pollutants in rainwater and air. They help make the local environment cleaner.
· Cool roofs are painted white to better reflect sunlight.
· Radiant barriers are made of a reflective covering, such as aluminum. They both reflect the sun’s heat instead of absorbing it.
All these types of roofs help
lower the amount of energy needed to cool the building.
There are many advantages to using solar energy. PV cells last for a long time,
about 20 years. However, there are reasons why solar power cannot be used as the
only power source in a community. It can be expensive to install PV cells or
build a building using passive solar technology. Sunshine can also be hard to
predict. It can be blocked by clouds, and the sun doesn’t shine at night.
Different parts of Earth receive different amounts of sunlight based on
location, the time of year, and the time of day.
Wind Energy
People have been harnessing the
wind’s energy for a long, long time. Five-thousand years ago, ancient Egyptians
made boats powered by the wind. In 200 B.C.E., people used
windmills to grind
grain in the Middle East and pump water in China. Today, we capture the wind’s
energy with
wind turbines.
A turbine is similar to a windmill; it has a very tall tower with two or three
propeller-like blades at the top. These blades are turned by the wind. The
blades turn a
generator
(located inside the tower), which creates electricity. Groups of wind turbines
are known as
wind farms.
Wind farms can be found near farmland, in narrow mountain passes, and even in
the ocean, where there are steadier and stronger winds. Wind turbines anchored
in the ocean are called “offshore
wind farms.” Wind farms create electricity for nearby homes, schools, and other
buildings.
Wind energy can be very
efficient.
In places like the Midwest in the United States and along coasts, steady winds
can provide cheap, reliable electricity. Another great advantage of wind power
is that it is a “clean” form of energy. Wind turbines do not burn fuel or
emit
any pollutants into the air. Wind is not always a steady source of energy,
however. Wind speed changes constantly, depending on the time of day,
weather,
and geographic location. Currently, it cannot be used to provide electricity for
all our power needs. Wind turbines can also be dangerous for bats and birds.
These animals cannot always judge how fast the blades are moving and crash into
them.
Geothermal Energy
Deep beneath the surface is Earth’s core. The center of Earth is extremely hot—thought to be over 6,000 °C (about 10,800 °F). The heat is constantly moving toward the surface. We can see some of Earth’s heat when it bubbles to the surface. Geothermal energy can melt underground rocks into magma and cause the magma to bubble to the surface as lava. Geothermal energy can also heat underground sources of water and force it to spew out from the surface. This stream of water is called a geyser. However, most of Earth’s heat stays underground and makes its way out very, very slowly. We can access underground geothermal heat in different ways.
I. One way of using geothermal energy is with “geothermal heat pumps.” A pipe of water loops between a building and holes dug deep underground. The water is warmed by the geothermal energy underground and brings the warmth aboveground to the building. Geothermal heat pumps can be used to heat houses, sidewalks, and even parking lots.
II. Another way to use geothermal energy is with steam. In some areas of the world, there is underground steam that naturally rises to the surface. The steam can be piped straight to a power plant. However, in other parts of the world, the ground is dry. Water must be injected underground to create steam. When the steam comes to the surface, it is used to turn a generator and create electricity. In Iceland, there are large reservoirs of underground water. Almost 90% of people in Iceland use geothermal as an energy source to heat their homes and businesses.
An advantage of geothermal energy is that it is clean. It does not require any fuel or emit any harmful pollutants into the air. Geothermal energy is only avaiable in certain parts of the world.
Another disadvantage of using geothermal energy is that in areas of the world where there is only dry heat underground, large quantities of freshwater are used to make steam. There may not be a lot of freshwater. People need water for drinking, cooking, and bathing.
Biomass Energy
Biomass is any material that comes from plants or microorganisms that were recently living. Plants create energy from the sun through photosynthesis. This energy is stored in the plants even after they die. Trees, branches, scraps of bark, and recycled paper are common sources of biomass energy. Manure, garbage, and crops, such as corn, soy, and sugar cane, can also be used as biomass feedstocks. We get energy from biomass by burning it. Wood chips, manure, and garbage are dried out and compressed into squares called “briquettes.” These briquettes are so dry that they do not absorb water. They can be stored and burned to create heat or generate electricity. Biomass can also be converted into biofuel. Biofuels are mixed with regular gasoline and can be used to power cars and trucks. Biofuels release less harmful pollutants than pure gasoline.
A major advantage of biomass is that it can be stored and then used when it is needed. Growing crops for biofuels, however, requires large amounts of land and pesticides. Land could be used for food instead of biofuels. Some pesticides could pollute the air and water.
Biomass energy can also be a non-renewable energy source. Biomass energy relies on biomass feedstocks—plants that are processed and burned to create electricity. Biomass feedstocks can include crops, such as corn or soy, as well as wood. If people do not replant biomass feedstocks as fast as they use them, biomass energy becomes a non-renewable energy source.
Hydroelectric Energy
Hydroelectric energy is made by flowing water. Most hydroelectric power plants are located on large dams, which control the flow of a river. Dams block the river and create an artificial lake, or reservoir. A controlled amount of water is forced through tunnels in the dam. As water flows through the tunnels, it turns huge turbines and generates electricity.
Hydroelectric energy is fairly inexpensive to harness. Dams do not need to be complex, and the resources to build them are not difficult to obtain. Rivers flow all over the world, so the energy source is available to millions of people.
Hydroelectric energy is also fairly reliable. Engineers control the flow of water through the dam, so the flow does not depend on the weather (the way solar and wind energies do). However, hydroelectric power plants are damaging to the environment. When a river is dammed, it creates a large lake behind the dam. This lake (sometimes called a reservoir) drowns the original river habitat deep underwater.
Sometimes, people build dams that can drown entire towns underwater. The people who live in the town or village must move to a new area.
Hydroelectric power plants don’t work for a very long time: Some can only supply power for 20 or 30 years. Silt, or dirt from a riverbed, builds up behind the dam and slows the flow of water.
Other Renewable Energy Sources
Scientists and engineers are constantly working to harness other renewable energy sources. Three of the most promising are
· tidal energy,
· wave energy, and
· algal (or algae) fuel.
Tidal energy harnesses the power of ocean tides to generate electricity. Some tidal energy projects use the moving tides to turn the blades of a turbine. Other projects use small dams to continually fill reservoirs at high tide and slowly release the water (and turn turbines) at low tide.
Wave energy harnesses waves from the ocean, lakes, or rivers. Some wave energy projects use the same equipment that tidal energy projects do—dams and standing turbines. Other wave energy projects float directly on waves. The water’s constant movement over and through these floating pieces of equipment turns turbines and creates electricity.
Algal fuel is a type of biomass energy that uses the unique chemicals in seaweed to create a clean and renewable biofuel. Algal fuel does not need the acres of cropland that other biofuel feedstocks do.
National Geographic Renewable Energy
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