Capitol Power Plant

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Coordinates: 38°52′58.35″N77°0′27.06″W / 38.8828750°N 77.0075167°W / 38.8828750; -77.0075167


The Capitol Power Plant in 2011, from the Architect of the Capitol Flickr - USCapitol - Capitol Power Plant.jpg
The Capitol Power Plant in 2011, from the Architect of the Capitol
A Capitol Power Plant employee inspecting the equipment, from the Architect of the Capitol Flickr - USCapitol - Working at the Capitol Power Plant.jpg
A Capitol Power Plant employee inspecting the equipment, from the Architect of the Capitol
The Capitol Power Plant at the turn of the 20th century. CapitolPowerPlant.jpg
The Capitol Power Plant at the turn of the 20th century.

The Capitol Power Plant is a fossil-fuel burning power plant which provides steam and chilled water for the United States Capitol, the Supreme Court, the Library of Congress and 19 other buildings in the Capitol Complex. Located at 25 E St SE in southeast Washington, D.C., it is the only coal-burning power plant in the District of Columbia, though it mostly uses natural gas. [1] [2] The plant has been serving the Capitol since 1910, and is under the administration of the Architect of the Capitol (see 2 U.S.C.   § 2162). Though it was originally built to supply the Capitol complex with electricity as well, the plant has not produced electricity for the Capitol since 1952. [1] Electricity generation is now handled by the same power grid and local electrical utility (Pepco) that serves the rest of metropolitan Washington. [3]

According to the U.S. Department of Energy, the facility released 118,851 tons of carbon dioxide in 2007. [4] In 2009 it switched to using natural gas, unless coal was needed for backup capacity. In 2013, it was announced that the Capitol Power Plant would add a Cogeneration Plant to the CPP that will use natural gas in a combustion turbine in order to efficiently generate both electricity and heat for steam, thus further reducing emissions. A 7.5 megawatt cogeneration facility was completed at the CPP in 2018. [2]


The power plant was constructed under the terms of an act of Congress passed on April 28, 1904, authorized in order to support two new office buildings that were then being planned. Now known as the Cannon House Office Building and the Russell Senate Office Building, these new offices required a substantial increase in energy to Capitol Hill. In addition, the U.S. Capitol and the Library of Congress would also receive power from the new plant, along with all future buildings to be constructed on the Capitol campus. [3]

Originally called the "Heating, Lighting, and Power Plant," the Capitol Power Plant was one of the earliest 25-cycle alternating current electric-generating facilities in the United States. The original steam boilers were replaced in 1923. In 1950, the steam boilers were modernized and replaced with coal-fired steam generators; at the same time, the plant's electricity generating capacity had reached its limit, and it was decided to abandon electricity production in favor of the local electrical utility. Expansion of the plant to support additional new construction was authorized in 1958, 1970, and in the early 21st century to support the opening of the Capitol Visitor Center. [3]


Senators from coal mining states blocked a proposal in 2000 to use cleaner fuel for the plant. Senators Mitch McConnell (Republican of Kentucky) and Robert Byrd (Democrat of West Virginia), both from coal mining states, used their influence as two of the Senate's most senior members to block this proposal. In May 2007, CNN reported that two companies, International Resources Inc. and the Kanawha Eagle mine, have a contract to supply a combined 40,000 tons of coal to the plant over the next two years. The companies gave a combined $26,300 to the McConnell and Byrd campaigns for the 2006 election. [5]

In June 2007, Speaker of the House Nancy Pelosi announced the "Greening the Capitol" initiative. [6] The initiative's goal is to make the Capitol carbon neutral, and the power plant is a major obstacle to achieving this objective. [5] In November 2007, Daniel Beard, the House's Chief Administrative Officer, announced that he would purchase $89,000 worth of carbon offsets for 30,000 tons of carbon emissions. Beard made the purchase from the Chicago Climate Exchange. [7] On February 28, 2009, Pelosi and Senate Majority Leader Harry Reid sent a letter to the Architect of the Capitol asking him to create a plan to switch the power plant entirely to natural gas by the end of 2009. [8] This letter came just three days before a March 2009 scheduled protest (which happened despite the change). [9]

In response to the letter from Pelosi and Reid, the Architect of the Capitol replied on May 1, 2009 that the plant had been transitioning to natural gas and was prepared to switch completely to that fuel, using coal only as a backup source. In 2008, the plant had operated on about 65% natural gas and 35% coal, compared to 58% coal in 2005. This did not end the Capitol complex's reliance on coal. Electricity is supplied by a local utility company that uses coal as a power source. [10] By 2011, coal use at the CPP was down to 5%.

In 2013, the Architect of the Capitol announced that it had "identified the construction of a cogeneration plant as the most environmentally and economically beneficial way to meet its goal to use natural gas 100% of the time." The new cogeneration unit would use 100 percent natural gas to provide power for the 23 buildings of the Capitol complex, which includes the Capitol Building, the House and Senate office buildings, the Supreme Court, the U.S. Botanic Garden and the Library of Congress buildings, among others. Not only will it reduce the use of coal on-site for the chillers and boilers, but it would provide 93% of the facility's electricity. This would allow it to replace inefficient, 45% coal-generated electricity bought off the grid with more efficiently generated, on-site electricity that uses no coal. [11] They completed the permitting process for this facility in June 2013.


Table 1: Summary of Point Source Emissions: District of Columbia in 2002 (Tons) [12]

Capitol Power Plant8312948384
Pepco Benning Road Generating Station 15/1615253146767
Pepco Buzzard Point Generating Station53403905
GSA Central Heating Plant1266812
10 Miscellaneous Sources1252932014
Share produced by Capitol Power Plant65%10%20%46%

Table 2: Summary of Pollution Reduction at the Capitol Power Plant Following Transition to Natural Gas (Tons) [11]

Hazardous Air Pollutants-39.6229.686.038.40


For a plant its size (roughly 1/100 the size of the typical 500 MW power plant), the Capitol Power Plant used to produce a remarkably high quantity of the type of particulate matter (PM2.5) most closely associated with human health effects. As shown in Table 1, in 2002, the plant emitted a full 65 percent of the PM2.5 emitted in the District of Columbia by fixed sources (excluding automobiles, buses, trucks, trains and shipping). With the two other large power plants in the District of Columbia closed, and the CPP transition to cleaner energy, all of the emissions have been significantly reduced.

Particle pollution, also called particulate matter or PM, is one of six "criteria pollutants" (PM, lead, mercury, sulfur dioxide, nitrogen oxide, and ozone) regulated by the Environmental Protection Agency. PM is a complex mixture of extremely small particles and liquid droplets in the air. When breathed in, these particles can reach the deepest regions of the lungs. Exposure to particle pollution is linked to a variety of significant health problems, ranging from aggravated asthma to premature death in people with heart and lung disease. Particle pollution also is the main cause of visibility impairment in the nation's cities and national parks. [13] Fine particles (PM2.5) are 2.5 micrometers in diameter and smaller; and inhaleable coarse particles (PM10) are smaller than 10 micrometers and larger than 2.5 micrometers. [13]

In 2006, EPA tightened the 24-hour fine particle standard from 65 micrograms per cubic meter to 35 micrograms per cubic meter, while leaving the annual fine particle unchanged. EPA retained the annual fine particle standard at 15 micrograms per cubic meter. EPA retained the pre-existing 24-hour PM10 standard of 150 micrograms per cubic meter. Due to a lack of evidence linking health problems to long-term exposure to coarse particle pollution, the agency revoked the annual PM10 standard. [13]

Even before the EPA tightened the fine particular standard, Washington, D.C., was a "non-attainment" area. [14]

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Power station facility generating electric power

A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.

Incineration waste treatment process, burning material for disposal

Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration and other high-temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas and heat. The ash is mostly formed by the inorganic constituents of the waste and may take the form of solid lumps or particulates carried by the flue gas. The flue gases must be cleaned of gaseous and particulate pollutants before they are dispersed into the atmosphere. In some cases, the heat generated by incineration can be used to generate electric power.

Cogeneration Simultaneous generation of electricity, and/or heating, or cooling, or industrial chemicals

Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time. Trigeneration or combined cooling, heat and power (CCHP) refers to the simultaneous generation of electricity and useful heating and cooling from the combustion of a fuel or a solar heat collector. The terms cogeneration and trigeneration can also be applied to the power systems simultaneously generating electricity, heat, and industrial chemicals.

Flue-gas desulfurization

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Fossil fuel power station Facility that burns fossil fuels to produce electricity

A fossil fuel power station is a thermal power station which burns a fossil fuel, such as coal or natural gas, to produce electricity. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, which then operates an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating gas engine. All plants use the energy extracted from expanding gas, either steam or combustion gases. Although different energy conversion methods exist, all thermal power station conversion methods have efficiency limited by the Carnot efficiency and therefore produce waste heat.

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  2. 1 2 "Cogeneration Addition at the Capitol Power Plant". Architect of the Capitol. Retrieved June 6, 2014.
  3. 1 2 3 "Capitol Power Plant". Explore Capitol Hill. Architect of the Capitol. Retrieved February 4, 2013.
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  5. 1 2 "Effort to 'green' U.S. Capitol complicated by coal". CNN.
  6. Greening the Capitol Archived February 25, 2009, at the Wayback Machine
  7. Weisman, Jonathan (November 5, 2007). "Capitol to Buy Offsets in Bid to Go Green". The Washington Post.
  8. "Speaker Blog".
  9. Anti-coal campaign gets some good news, but battle is far from won Archived February 28, 2009, at the Wayback Machine
  10. "Congress to Stop Using Coal in Power Plant". nbcnews. April 5, 2009. Retrieved June 6, 2014.
  11. 1 2 "Capitol Power Plan Cogeneration Fact Sheet" (PDF). Retrieved June 6, 2014.
  12. Base Year 2002 Emissions Inventory Document for Washington, DC-MD-VA Annual PM2.5 NAA_12.14.07, Attachment A1, page 2, "Summary of Point Source Emissions: District of Columbia," [ permanent dead link ] Metropolitan Washington Council of Governments, Air Quality Files
  13. 1 2 3 "PM Standards Revision - 2006," Archived May 22, 2011, at the Wayback Machine U.S. Environmental Protection Agency.
  14. EPA, US. "Green Book - US EPA".