Energy Info


Renewable Energy Sources

What is Renewable Energy?

Renewable energy resources can be referred to as inexfraustible resources. The availability of energy amount per unit of time of these resources is restricted. Some excellent examples of these resources include hydropower, biomass, geo thermal, solar, wind, wave action, ocean thermal and tidal action. In the year 1850, about ninety percent of the energy consumption in the United States came from renewable energy resources. Today, the U.S. is heavily dependant on varied non-renewable fossil fuels such as oil, coal and natural gas. In the year 2004, about six percent of all energy consumed and nine percent of electricity production in all, was derived from renewable energy resources.

How is Renewable Energy used?

Renewable energy is highly utilized for generation of electricity. It can also be used for producing heat in industrial processes, heating and cooling buildings as well as fuel transportation. In the year 2004, electricity generation was accounted for about seventy percent of total renewable energy consumption. About 359 billion kilowatt hours (kWh) amounting to almost 9 percent of total U.S. electricity generation came from renewable energy. Industrial process heat and building space heating accounted for about 25 percent of renewable energy utilization. The rest of the energy was utilized as fuel for vehicles.

What are the different types of Renewable Energy?

Biomass Energy:

This is derived from non-fossilized materials coming from plants. The largest sources of biomass energy are wood and wood waste. Other resources include energy derived from alcohol fuels and municipal solid waste (MSW). In the year 2004, biomass contributed to about 47 percent of renewable energy consumption. About half of this energy was utilized for heating purposes, 40 percent for producing electrical power and rest as fuel for transportation.


Wood biomass includes wood chips resulting from forestry operations, residues coming from lumber, pulp or paper and furniture mills and fuel wood for space heating. ‘Black Liquor is known to be the largest and only source of wood energy. It is actually a residue of pulp, paper and paperboard production. It functions towards supplying more than fifty per cent of all the above mentioned energy requirements of the industry. Manufacturers of lumber mills and furniture tend to utilize saw dust, chips and bark for more than 60 percent of requirements for energy. A small but increasing amount of wood is burnt in conjunction with coal in utility power plants. Wood chips, cordwood and pellets obtained from sawdust are utilized for space as well as water heating purposes in varied buildings. More than about two million households use these elements as primary or supplemental fuel heating sources.

Municipal Solid Waste and Biogas:

About 29 million tons of MSW was burned by waste-to-energy facilities in the year 2004 in order to produce electricity and heat. About 380 landfills are used to recover methane. This contributes to the formation of waste decomposes in low oxygen conditions. Methane is burnt to facilitate production of heat and electricity. The production of methane is also done through anaerobic ‘digesters’ for generation of heat and electricity at dairy farms, municipal sewage treatment facilities and concentrated livestock operations.

Bio Fuels:

These include a variety of alcohol fuels such as ‘bio diesel’ ‘a fuel made by combining grain oils and animal fats. Fuel ethanol obtained from corn is the most commonly used bio fuel in the United States. Almost all fuel ethanol is consumed in the form of a gasoline oxygenate in reformulated or oxygenated gasoline or as a gasoline enhanced in fuels such as ‘gasohol’. Gasohol is also known as E-10. E-10 is a combination of 10 percent ethanol and 90 percent gasoline fuel. In the year 2004, total consumption of fuel ethanol was amounted to 3.5 billion gallons. This is equal to about 2.3 billion gallons of gasoline on an energy content basis. It is also equivalent of gasoline amount consumed in 4.3 million passenger cars. The utilization of Bio diesel is quite small. However, its’ utilization in diesel engines as well as heating is increased on a consistent basis.


This is a type of electricity produced from flowing water. That's why the output of hydropower tends to vary according to rainfall. Most of the hydropower is produced at large facilities constructed by the federal government including Grand Coulee Dam on the Columbia River in Washington State. This is also known to be the largest single electric power facility in the U.S. The rivers of western United States houses most of the largest dams. However, there are a lot of smaller facilities operating across the nation.

The production of Hydropower varies from years to year and also depends on precipitation. In the year 2004, hydropower dams produced about 270 billion kWh. This amounts to about seven percent of total U.S. electricity production and accounted for about 45 percent of total renewable energy consumption. The latest ‘wave’ in hydropower technologies is also in the process of being developed in order to harness the energy coming from ocean waves, currents and tides.

Geothermal Energy:

Geothermal energy is a type of energy emitted from the hot interior of the earth. Fissures in the crust of earth facilitates rise in water heated through geothermal energy naturally to the surface at geysers as well as hot springs. All wells drilled into the earth facilitate heated steam or water to escape to the surface in a controlled manner to operate steam turbines and electricity generators.

The temperature of the earth or ground water near the surface of earth is utilized as a heat source in a different application. About 6 percent of total renewable energy consumption in the year 2004 was contributed by geothermal energy. The same year witnessed 14.4 billion kWh of electricity generation by geothermal power plants in Utah, California, Nevada and Hawaii. Hot sprints have been utilized at spas and resorts for a long time now. It is also used for creation of heat in greenhouses, buildings, aquaculture facilities as well as industrial processes. There are more than about 500,000 geothermal heat pumps in the United States. This number is increasing by around 37,000 each year.

Wind Energy:

Water pumping windmills as well as small wind electric generators were used throughout the United States. However, the rural electrification programs of the 1930’s as well as 1940’s replaced the requirement for these systems. In the early 1980s, revival in wind power generation was a result of federal and state government policies.

Solar Energy:

Solar Energy systems utilize solar radiation in order to produce electricity and heat. About 90 percent consumption of solar energy was used for creation of heat and the remaining was used to produce 580 million kWh of electricity. Here is a description of three basic categories of solar systems:

  • Solar Thermal Systems for heating water and buildings: These systems utilize solar collectors in order to absorb solar radiation. The process is helpful in heating water or air. The sales of solar thermal energy collectors grew drastically between the period 1975 and 1985. This was facilitated by federal and state income tax credits for solar energy equipment installation. With the end of federal tax credits in 1985, sales also dropped. However, a drastic increase in sales of low cost collectors for heating swimming pools has increased in the past few years.

  • Solar Thermal-Electric Power Plants: These power plants tend to utilize concentrating solar collectors in order to focus on the rays of sun to heat fluid at a high temperature. The heated working fluid can be thereafter utilized to generate steam to further facilitate operation of a turbine. This is later utilized towards production of electricity in a generator. Parabolic Trough, Solar Dish and Solar Power Towers are the three primary types of solar thermal power systems developed in the United States.

  • Photovoltaic Systems: These systems are heavily based on solar electric cells that convert solar radiation directly into electricity. Different individual PV cells are successfully configured into modules of varying electricity producing capacities.
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