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Renewable Energy
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Last Updated: December 2008
Next Update: August 2009 What is renewable energy? Whereas fossil fuels are exhaustible, renewable energy sources - water (hydropower), biomass, wind, heat from the earth (geothermal), and the sun (solar energy) - regenerate and can be sustained indefinitely. "Green" renewables generally produce far lower quantities of grennhouse gases by offsetting fossil fuels used to generate electricity. The use of renewable energy is not new. Five generations (125 years) ago, wood supplied up to 90 percent of our energy needs. Due to the convenience and low prices of fossil fuels, wood use declined. Now, the biomass which would normally present a disposal problem is converted into electricity (e.g., manufacturing wastes, rice hulls, and black liquor from paper production). Renewable Energy Consumption in the Nation's Energy Supply, 20071
Source: Energy Information Administration, Office of Coal, Nuclear, Electric and Alternate Fuels Renewable Energy Consumption Decreases. Renewable energy consumption declined 1 percent between 2006 and 2007 to 6,830 trillion Btu, according to preliminary 2007 data. In contrast, both total energy and non-renewable energy increased 2 percent. Hydro electricity dropped 14 percent in 2007 due to reduced precipitation in several regions of the country. On the plus side, biomass-based energy grew 7 percent and wind-generated electricity jumped 21 percent. Major increases in consumption of biomass to produce and use biofuels (ethanol and biodiesel) were almost entirely responsible for the increase in biomass during 2007 Electric Power Sector. While the electric power sector currently consumes the most renewable energy (51 percent), its use dropped 8 percent between 2006 and 2007. In 2003, the electricity sector accounted for 59 percent of total renewable energy consumption. Industrial Sector. The industrial sector was the second-leading consumer of renewable energy, accounting for nearly 30 percent, due to that sector's major consumption of wood and derived fuels. Geothermal and conventional hydropower played only minor roles in the industrial sector. Other Sectors. The transportation sector was the fastest growing sector, consuming 30 percent more renewable fuel between 2006 and 2007. This is mainly due to increased ethanol consumption, by far the fastest growing component of biofuels during those years. Residential sector consumption grew 12 percent due to healthy increases in all three energy sources: biomass, geothermal, and solar/photovoltaic. The residential sector consumed about 8 percent using wood for space heating and solar energy for water heating and electricity. The commercial sector accounted for just 2 percent of total renewable energy consumption.
In 2007, there were 60 manufacturers and/or importers active in manufacturing, importing, and/or exporting solar thermal collectors, a significant increase from the 44 companies operating in 2006. These companies shipped 15.2 million square feet of solar thermal collectors in 2007, compared with 20.7 million square feet in 2006. Corresponding to the decrease in total shipments, domestic shipments of solar thermal collectors plunged more than 29 percent to 13.8 million square feet during 2007. Solar thermal collectors are generally used almost exclusively for pool heating. The residential sector is the largest domestic market in the United States for solar thermal collectors. Solar thermal collectors shipped to the residential sector in 2007 totaled 12.8 million square feet, approximately 93 percent of total domestic shipments. This market sector primarily involves the use of low-temperature solar collectors for pool heating and medium-temperature solar collectors for water heating. More than half (56 percent) of the total domestic shipments in 2007 were sent to the wholesale market, 33 percent to retail distribution, 3 percent to exporters, 6 percent to installers, and about 2 percent directly to end-users. Geothermal Heat Pumps. Manufacturers shipped 63,682 geothermal heat pumps (GHP) in 2006, a 33 percent increase over the 2005 total of 47,830. Of those shipped in 2006, 10,968 were ARI-320 rated2, and 47, 440 were ARI-325 or ARI-330. ARI-rated shipments increased to 58,408 units in 2006, while the number of other non-ARI-rated units shipped increased to 5,274 in 2006. The total rated capacity of geothermal heat pumps shipped in 2006 was 245,603 tons, compared to 160,402 tons in 2005.3 Green Pricing Participation Decreases. Green pricing/marketing programs allow electricity customers to pay the additional costs for renewable energy through direct payments on their monthly bills. The total number of participating customers was 645,167 in 2006, an decrease of 32 percent from 2005. Of this total, 609,213 or 94 percent, were residential customers. The number of participating customers decreased in nine states, most notably in Ohio, which lost over 400,000 customers, as a result of Green Mountain Energy Co., a green power marketer, discontinuing service in Ohio. The state with the biggest increase was Oregon with a net gain of almost 17,000 customers, followed closely by New York, with a net gain of almost 16,000 customers. U.S. Green Pricing Customers by Top 5 States, 2006
Net metering participation increases. Net metering programs usually permit customers - typically residential - operating very small generators for some of their needs to purchase extra electricity when needed and to sell back any excess power to the utility. Net metering programs have increased each year during the 2003 through 2006 period for both electric industry participants and participating program customers. The total number of electric industry participants increased from 188 in 2005 to 232 in 2006. The total number of participating customers was 34,469 in 2006, an increase of 63 percent over 2005. Of this total, 31,323 or 91 percent, were residential customers. Thirty-five states and the District of Columbia reported gains of net metering customers, with the largest gain - 8,705 customers - reported by California.
How Renewable Energy Is Produced. Solar Energy. Solar energy produces predictable flows of energy that can be converted to other energy forms, such as electricity and heat, or stored in biomass. Clouds, the daily pattern of light and darkness, seasons, and dust in the air greatly affect the fraction of sunlight which is available. The sun's rays must fall on a relatively large area for enough heat to be collected for conversion to electricity; a "concentrating collector" can be used to focus the rays onto a much smaller area. Solar energy can also be directly converted into electricity by means of photovoltaic cells (based on the element silicon) which generate electricity. In nations with underdeveloped electricity networks, photovoltaic systems may be chosen because they can provide small amounts of electric power. The major economic application of solar energy is residential heating as well as other buildings. Solar collectors, often seen on rooftops, are used for hot water, space heating, and heating swimming pools. However, backup heating systems are generally needed. Wind power. Wind machines use blades to collect the wind’s kinetic energy. The blades are connected to a drive shaft that turns an electric generator to produce electricity. New technologies have decreased the cost of producing electricity from wind, and growth in wind power has been encouraged by tax breaks for renewable energy and green pricing programs that were mentioned above. 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. The amount of electricity generated from wind increased at a greater rate than any other renewable source in recent years. In 2006, electricity generated from wind was almost 50 percent more than wind generation in 2005 and more than double the amount in 2003. Wind machines generate electricity in 28 different states in 2006. The states with the most wind production are Texas, California, Iowa, Minnesota, and Oklahoma. Biomass. Biomass, formed when the sun shines on plants and trees, can be burned, providing heat for homes and fuel for boilers. Electricity generators burn wood chips, sawdust, garbage, bagasse (a plant refuse), and low-quality methane gases from landfills, but supplies are limited by distance to the generator. Another widely available fuel source is the biomass from corn; this is fermented into alcohol (ethanol) and the alcohol is used to replace petroleum-based automobile fuel (by blending with gasoline). Another biomass is oil is extracted from soybeans that is blended with diesel. Biomass burning for cooking and heating, especially in underdeveloped nations, may contribute to global warming and erosion. Geothermal energy. Geothermal energy comes from natural processes beneath the earth's surface, and is recovered as steam and hot water. Most domestic electricity from geothermal energy is generated in California, other western States, and Hawaii. The world's largest geothermal facility and the first commercial-scale development tools placed in California are at The Geysers, a 10-megawatt unit owned by Pacific Gas & Electric. Direct-use of geothermal energy for aquaculture, health spas and district heating continues to grow, as do installations of geothermal heat pumps.
1. 2007 data are preliminary
More information on this subject can be found in the following EIA publications: |
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