Which are the best new CHP schemes operating in the US? The US Environmental Protection Agency (EPA) operates a CHP Partnership which seeks to reduce the environmental impact of power generation by promoting the use of CHP and names its ENERGY STAR CHP Award winners each year. Here are some details of this year’s winners.

Night-time view of the 14 MW CHP system installed at the University of Massachusetts Amherst. The 10 MW Solar combustion turbine, heat recovery steam generator, 4 MW steam turbine and three natural gas-fired boilers replace coal-fired boilers dating back nearly 80 years.
Source: Adam Caron, Soulfullifephotography.com

The US Environmental Protection Agency (EPA) puts it very well – combined heat and power (CHP), also known as cogeneration, is an efficient, clean, and reliable approach to generating power and thermal energy from a single fuel source. By installing a CHP system designed to meet the thermal and electrical base loads of a facility, CHP can greatly increase the facility’s operational efficiency and decrease its energy costs. At the same time, CHP reduces the emission of greenhouse gases that contribute to global climate change.

The EPA’s voluntary CHP Partnership works closely with energy users, the CHP industry, state and local governments, and other clean energy stakeholders to facilitate the development of new projects and to promote their environmental and economic benefits. It also chooses its annual ENERGY STAR CHP Award winners.

The award scheme recognizes highly efficient CHP systems that reduce emissions and use at least 5% less fuel than comparable, state-of-the-art, separate heat and power generation. The EPA is proud to recognize the outstanding pollution reduction and energy efficiency qualities of the following six projects that have won 2011 ENERGY STAR CHP Awards.

The six winners, not necessarily new schemes, include CHP installations at three universities – each powered by combustion turbines – along with a further scheme located at a medical research facility.

A fifth scheme uses microturbine technology to supply heat and power to an office building and data centre. The sixth scheme also uses microturbines but in a rather different application – to supply energy to a natural gas compression station.

CORNELL UNIVERSITY

Cornell University set a goal of reducing its carbon dioxide emissions to 20–30% below its 1990 levels by 2012. The university’s most recent step to improve its energy infrastructure and reduce carbon dioxide emissions was the addition of 30 MW of new CHP capacity in 2009.

Two new Solar combustion turbine/generators, along with two existing back pressure steam turbines provide the university’s 31,000 faculty, staff and students with up to 37 MW of electricity. Additional electricity is generated by a small 1904-vintage hydroelectric plant re-built in 1981.

Three boilers and two exceptionally efficient heat recovery systems can produce 580,000 pounds per hour (16,800 hp) of steam to satisfy the demand of campus operations. The combined effect of the new CHP system and energy modernization activities will allow Cornell University to retire two coal boilers in 2011. These units previously burned 59,000 tonnes of coal each year.

With an operating efficiency of nearly 79%, the CHP system requires approximately 29% less fuel than a typical energy supply system. Based on this comparison, the CHP system prevents an estimated 81,000 tonnes per year of carbon dioxide emissions, equivalent, says the EPA, to the emissions from more than 15,000 passenger vehicles.

DOMINION TRANSMISSION — CRAYNE STATION

Dominion Transmission is an interstate gas transmission company and operates one of the largest underground natural gas storage and transmission systems in the US. This gas transmission network includes approximately 7800 miles of pipeline in six states – Ohio, Maryland, New York, Pennsylvania, Virginia, and West Virginia. Some of Dominion’s gas compression sites are located far from the electrical grid, or in areas that have limited availability of grid-supplied power, and microturbine/generators have been used to provide a reliable power supply.

Capable of functioning in remote locations, adhering to emissions standards, ensuring power reliability and reducing maintenance costs, CHP has been the answer to the varying operational obstacles Dominion faces at some of its gas compressor stations. The Crayne Compressor Station CHP system located in Waynesburg, Pennsylvania is a great example. Since 2004, three microturbines have been generating up to 195 kW of electricity – enough power to meet 100% of the station’s electricity demand.

The turbines that power the station’s gas compressors are fuelled with gas from the pipeline. Heat from the CHP system is used to warm raw gas chilled during the decompression process when it is taken from the pipeline.

With an operating efficiency of almost 73%, the CHP system requires about 25% less fuel than a typical system with a similar output and prevents an estimated 400 tonnes of carbon dioxide emissions annually.

KPMG, NEW JERSEY

KPMG LLP may serve one fifth of the Fortune 1000 companies as clients, but that does not mean it is too busy providing audit, tax and advisory services to recognize the importance of energy efficiency, reliable power and the benefits of CHP. Late in 2007, KPMG launched its Living Green programme to reduce the firm’s consumption of natural resources and its carbon footprint. In the first three years of the programme, KPMG reports it met its goals and reduced its carbon emissions by 22%.

The stylish exterior of the CHP scheme at the University of Cincinnati, which saves the establishment an estimated $4 million per year

The CHP system located at the firm’s administrative headquarters in Montvale, New Jersey is a key factor in that success.

Powered by more than a dozen Capstone microturbines provided by UTC Power, the CHP system generates up to 720 kW of electricity – nearly half the power needed by the data centre located at the site. Using otherwise wasted heat from the microturbine exhaust, the CHP system also produces chilled water that is used to cool the data centre and keep the servers operating within specified temperature limits.

With an operating efficiency of 68%, the CHP system requires about 22% less fuel than a conventional energy supply system with a similar output and thereby prevents an estimated 2000 tonnes of carbon dioxide emissions each year.

NATIONAL INSTITUTES OF HEALTH

How do you meet the escalating energy needs of one of the world’s largest medical research facilities, which is growing, constrained for space, under pressure to minimize air pollution and challenged by a tight construction budget? The National Institutes of Health (NIH) answered that question in 2002 when it began operation of a natural gas-fired CHP system.

Located near the centre of its 75-building, 1.2 km2 main campus in Bethesda, Maryland, the CHP system – designed and developed by PEPCO Energy Services – generates up to 23 MW of electricity for the local grid. By using otherwise wasted heat from the exhaust of the combustion turbine, it also produces up to 180,000 pounds per hour (5200 hp) of steam that is used to provide space heating, space cooling and to support laboratory operations.

With an operating efficiency of 76%, the CHP system requires about 31% less fuel than a typical energy-supply system. Based on this comparison, the CHP system prevents an estimated 46,000 tonnes of carbon dioxide emissions each year.

THE UNIVERSITY OF CINCINNATI

The University of Cincinnati greatly benefits from the reliability, environmental performance, and cost savings of its 46 MW natural gas-fired CHP system. Powered by two Solar combustion turbines, the system provides electricity and steam to the campus to support the university’s faculty, six hospitals and more than 35,000 students.

A key objective of the project was to improve the reliability of the power supply to support medical and other research, according to the university. In addition to reducing the university’s dependence on grid-supplied electricity, the turbines can also run on fuel oil in case of an unforeseen interruption in the natural gas supply.

While satisfying almost 50% of the campus electricity demand, the system saves the university an estimated US$4 million each year by recovering the otherwise wasted heat from the turbine exhaust and producing steam. During cooler months, the steam is used for space heating. When building cooling is required, the steam is used to produce additional electricity that makes chilled water to cool campus facilities.

At night, when less cooling is needed, the chilled water produced by the CHP system is stored in a 13,200 m3 underground storage tank. The chilled water is then pumped to buildings across campus during the day to meet cooling demands and reduce operating costs.

With an operating efficiency of 73%, the system requires about 32% less fuel than a conventional system with similar output and prevents an estimated 95,000 tonnes of carbon dioxide emissions each year.

UNIVERSITY OF MASSACHUSETTS AMHERST

In December 2008, the University of Massachusetts Amherst began operating a 14 MW CHP system. The system represents a major milestone for the university and is part of a multi-year initiative to reduce fuel consumption and minimize its environmental footprint. Activities ranging from the replacement of old light fixtures to a $133 million investment in the CHP system are the reason the university has reduced overall energy consumption by 21% since 2004.

A 10 MW Solar combustion turbine, a heat recovery steam generator, a 4 MW steam turbine and three natural gas-fired boilers have replaced the university’s coal-fired boilers, which date back almost 80 years. The CHP system produces almost all the electric and steam demand for a campus that consists of more than 200 buildings and nearly 930,000 m2 of building space.

Interior view of the CHP scheme at the National Institutes of Health’s main campus in Bethesda, Maryland – which operates at an efficiency of 76%

Interestingly, a unique and environmentally progressive characteristic of the system has little to do with energy conservation – about 600 m3 of treated effluent per day from the local wastewater treatment plant is used to generate steam. The effluent replaces the drinking water that would typically be used by such systems.

Exterior view of Cornell University’s 2009 CHP plant – a re-built hydroelectric scheme provides further on-site power

With an operating efficiency of nearly 75%, the CHP system requires about 18% less fuel than the separate production of thermal energy and electricity. Based on this comparison, the CHP system prevents an estimated 24,000 tonnes per year of carbon dioxide emissions.

For details of the EPA CHP Partnership, visit https://epa.gov/chp

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