Energy in Briefs explain important energy topics in plain language. Each Brief answers a question relevant to the public and recommends resources for further reading. Please use the tools to the right to give us feedback, share with others, or sign up for notices as new Briefs are released.
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August 30, 2011How much of the world's electricity supply is generated from wind and who are the leading generators?
Worldwide wind power generation exceeded 250 billion kilowatthours in 2009, which is equivalent to the annual electricity consumption of over 22 million average households in the United States. Wind generation increased by about 20% from 2008 to 2009, and has more than tripled since 2004. This growth is mostly due to capacity increases in the United States, China, India, and Western Europe. Despite this growth, the world still generated only 1% of its total electricity from wind power in 2009.
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August 8, 2011How old are U.S. power plants?
The current fleet of electric power generators has a wide range of ages. About 530 gigawatts, or 51% of all generating capacity, were at least 30 years old at the end of 2010. Trends in generating capacity additions vary by fuel type, for coal, hydropower, natural gas, nuclear, petroleum, and wind.
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August 4, 2011What is shale gas and why is it important?
Shale gas refers to natural gas that is trapped within shale formations. Shales are fine-grained sedimentary rocks that can be rich sources of petroleum and natural gas. Over the past decade, the combination of horizontal drilling and hydraulic fracturing has allowed access to large volumes of shale gas that were previously uneconomical to produce. The production of natural gas from shale formations has rejuvenated the natural gas industry in the United States.
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June 24, 2011How dependent are we on foreign oil?
The United States imported about 49% of the petroleum, which includes crude oil and refined petroleum products, that we consumed during 2010. About half of these imports came from the Western Hemisphere. Our dependence on foreign petroleum has declined since peaking in 2005.
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May 27, 2011What is the role of coal in the United States?
Due to its relatively low cost and abundance, coal is used to generate about half of the electricity consumed in the United States. Coal is the largest domestically-produced source of energy. Coal use, however, results in higher amounts of carbon dioxide per unit of energy than the use of oil or natural gas.
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May 6, 2011What are greenhouse gases and how much are emitted by the United States?
Greenhouse gases trap heat from the sun and warm the planet's surface. Of U.S. greenhouse gas emissions, 87% are related to energy consumption. Since 1990, greenhouse gas emissions in the United States have grown by about 1% per year. In 2005, about 21% of the world's total energy-related carbon dioxide was emitted by the United States.
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April 22, 2011What is the status of the U.S. nuclear industry?
There are currently 104 operable commercial nuclear reactors at 65 nuclear power plants. Since 1990, the share of the Nation's total electricity supply provided by nuclear power generation has averaged about 20%, with increases in nuclear generation that have roughly tracked the growth in total electricity output.
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October 28, 2010What are the major sources and users of energy in the United States?
The major energy sources in the United States are petroleum (oil), natural gas, coal, nuclear, and renewable energy. The major users are residential and commercial buildings, industry, transportation, and electric power generation. The pattern of fuel use varies widely by sector. For example, oil provides 94% of the energy used for transportation, but only 1% of the energy used to generate electric power. Understanding the relationships between the different energy sources and their uses provides insights into many important energy issues.
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September 1, 2010How much of our electricity is generated from renewable sources?
Americans used renewable energy sources — water (hydroelectric), geothermal, wind, sun (solar), and biomass — to meet about 8% of our total energy needs in 2009.
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February 1, 2010What is a cap-and-trade program and how does it work?
A cap-and-trade program is designed to reduce emissions of a pollutant by placing a limit (or cap) on the total amount of emissions. The cap is implemented through a system of allowances that can be traded to minimize costs to affected sources. Cap-and-trade programs for greenhouse gas emissions would increase the costs of using fossil fuels.
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December 14, 2009How can we compare or add up our energy consumption?
To compare or aggregate energy consumption across different energy sources like oil, natural gas, and electricity, we must use a common unit of measure. This is similar to calculating your food energy intake by adding up the calories in whatever you eat.
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November 20, 2009What are renewable portfolio standards (RPS) and how do they affect generation of electricity from renewable sources?
Renewable portfolio standards are policies designed to increase electricity generation from renewable resources, including wind, solar, geothermal, and biomass. Many States have their own renewable portfolio standards, although currently there is no program at the National level. States with renewable portfolio programs have seen an increase in the amount of electricity generated from renewable fuels.
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October 20, 2009What is the electric power grid, and what are some challenges it faces?
The grid of electric power lines has evolved into three large interconnected systems that move electricity around the country. Standards have been developed by the electric power industry to ensure coordination for the linked operations. Challenges facing the power grid include getting approval for corridors of land for new transmission lines within States or that cross multiple States, and the financing and constructing of new transmission lines to assure continued reliability of our electricity supply.
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January 28, 2009Who are the major players supplying the world oil market?
Governments of oil-rich countries have a major influence on the world supply of oil through ownership of national oil companies and, for some governments, their membership in OPEC.
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