What is Renewable Energy?
Renewable energy sources can be replenished in a short period of time. These abundant and sustainable energy sources can be used to curb our need for fossil fuels. This will ensure energy independence and protect the great American outdoors that we all enjoy.
America needs more and more energy every year, whether it is fuel to create electricity or fuel for our transportation vehicles. We have all heard the debates raging in the political realm about whether or not we should drill offshore and in the Arctic National Wildlife Refuge to help America become more energy independent. While politicians debate over this issue, they lose sight of alternatives to oil, like wind, solar, geothermal and hydro power. America will not be energy independent if all resources are used to exploit every last drop of oil on American soil. Non-renewable resources do not provide for America’s long-term energy needs.
Why don’t we use more Renewable Energy:
In the past, low fossil fuel prices, especially for natural gas, have made it difficult for renewable fuels to compete. The use of renewable sources is also limited by the fact that they are not always available. For example, cloudy days reduce solar energy; calm days mean no wind blows to drive wind turbines; droughts reduce water availability to produce hydroelectricity. With oil prices higher than ever, alternatives to these fossil fuels make renewable energy ever more appealing.
The production and use of renewable fuels has grown more quickly in recent years due to higher prices for oil and natural gas, and a number of State and Federal Government incentives, including the Energy Policy Acts of 2002 and 2005. The use of renewable fuels is expected to continue to grow over the next 30 years, although we will still rely on non-renewable fuels to meet most of our energy needs.
Biomass: Energy from Plant and Animal Matter
Biomass is organic material made from plants and animals. Biomass contains stored energy from the sun. Plants absorb the sun's energy in a process called photosynthesis. The chemical energy in plants gets passed on to animals and people that eat them. We make biomass energy with wood fuels, alcohol fuels, trash, decaying crops and landfill gas. Even our trash can be used for energy!
Scientists consider biomass a renewable energy source because we can always grow more trees and crops, and waste will always exist. Some examples of biomass fuels are wood, crops, manure, and some garbage.
Check out this article in the Colorado Independent about how Vail plans to use the beetle killed tree in the Colorado Rockies as biomass for making electricity. The mountain pine beetle leaves stands of brown trees in its wake. Their populations have exploded as a result of warmer winters and competition for water. Learn more about the pine beetle here.
Solar: Energy from the Sun
The sun has produced energy for billions of years. Solar energy is the sun’s rays (solar radiation) that reach the earth. Solar energy can be converted into other forms of energy, such as heat and electricity. In the 1830s, the British astronomer John Herschel used a solar thermal collector box (a device that absorbs sunlight to collect heat) to cook food during an expedition to Africa. Today, people use the sun's energy for lots of things, including generating electricity on-campus at CU.
Solar energy can be converted to electricity in two ways:
- Photovoltaic (PV devices) or “solar cells” – change sunlight directly into electricity. PV systems are often used in remote locations that are not connected to the electric grid. They are also used to power watches, calculators, and lighted road signs.
- Solar Power Plants - indirectly generate electricity when the heat from solar thermal collectors is used to heat a fluid which produces steam that is used to power generator.
Wind: Energy from Moving Air
Wind is simple: air in motion. Caused by the uneven heating of the earth’s surface by the sun, wind is constantly moving. Since the earth’s surface is made of very different types of land and water, it absorbs the sun’s heat at different rates.
Like old fashioned windmills, today’s wind machines use blades to collect the wind’s kinetic energy. As the blades turn, a generator inside the turbine creates clean electricity that can be added to the grid to power homes and businsses around the world. Historically windmills were used to mill grain. Now, they can make enough energy to power entire cities.
The world’s largest wind turbine is now the Enercon E-126. This turbine has a rotor diameter of 126 meters (413 feet). This new turbine is officially rated at 6 megawatts, but will most likely produce 7+ megawatts (or 20 million kilowatt hours per year). That’s enough to power about 5,000 households of four in Europe. A quick US calculation would be 938 kWh per home per month, 12 months, that’s 11,256 kWh per year per house. That’s 1776 American homes on one wind turbine.
In 2006, wind machines in the United States generated a total of 26.6 billion kWh per year of electricity, enough to serve more than 2.4 million households. This is enough electricity to power a city larger than Los Angeles, but it is only a small fraction of the nation's total electricity production, about 0.4 percent. The amount of electricity generated from wind has been growing fast in recent years. In 2006, electricity generated from wind was 2.5 times more than wind generation in 2002.
Hydropower: Energy from Moving Water
Of the renewable energy sources that generate electricity, hydropower is the most often used. It accounted for 7% of total U.S. electricity generation and 73% of generation from renewables in 2005.
Through the use of large dams we are able to harness the power of rivers and moving water. Dams are good for two things, creating electricity and creating reservoirs for drinking water. Water passes through the bottom of the dam and the pressure from all the water in the reservoir turns turbines that generate electricity. We use hydropower specifically to create electricity.
These dams do have their own drawbacks though. Impeeding the natural flow of a river causes widespread ecological damage, affecting the migration and habitat of countless aquatic species. The change in river flow can lead to serious problems with errosion and sediment depletion. Read about some of the impacts of dams on Colorado rivers in the LA Times article titled, Colorado river dams decimate native fish.
Geothermal: Energy inside the Earth
The word geothermal comes from the Greek words geo (earth) and therme (heat). So, geothermal energy is heat from within the earth. We can use the steam and hot water produced inside the earth to heat buildings or generate electricity. Because the water is replenished by rainfall and the heat is continuously produced inside the earth, geothermal energy is considered a renewable energy source.
Geothermal power today supplies less than 1% of the world's energy in 2009 needs but it is expected to supply 10-20% of world's energy requirement by 2050. Geothermal power plants today are operating in about 20 countries which are actively visited by earthquakes and volcanoes.