CHP Success Stories
The following case studies are illustrative of a growing number of facilities that are cutting costs and increasing their energy generation efficiency through the use of CHP.
Kent State University. With enrollment of 34,000 students across eight campuses, Kent State University (KSU) is Ohio’s second-largest university. The 880-acre main KSU campus in Kent contains 115 buildings. Its electricity load is 80 million kWh annually and rising. With continued expansion of campus buildings and residence halls, total electricity demands are likely to reach over 18.5 MW. Seeing this increase in demand on the horizon, KSU engineers began to consider CHP as a strategy to meet growing energy loads and control costs.
KSU, in conjunction with the U.S. Department of Energy and Dominion East Ohio, undertook a study to investigate the benefits of deploying expanded CHP technology at its new power plant facility. The primary objectives were to reduce fuel consumption, decrease emissions, and lower the cost of electricity. The study concluded that all of these objectives could be met through cogeneration units. What made KSU such an excellent candidate for CHP was not just its need for power but also the fact that it has a substantial year-round steam demand. The university uses almost all of the steam from the turbines in both the winter and summer.
The system consists of a fuel-flexible Taurus 60 turbine (which can run on natural gas or fuel oil) and a Taurus 70 generator capable of generating 7.2 MW of electricity. Both feature heat-recovery steam generator (HRSG) units, which enable plant operators to use waste steam to chill water. The 60,000 pounds of steam captured by the HRSG units provide more than half of the campus’s steam needs. In winter, the generators are able to provide almost 90% of KSU’s electricity needs; in summer they meet 60% of the load. In the event of a power outage, KSU’s power system can island itself from the grid and produce enough power for most of the university’s functions.
The power plant was built in two phases at a total cost of $23 million. The savings on fuel costs are substantial enough to eclipse the CHP system’s annual maintenance costs of more than $400,000. Total annual savings are expected to be more than $700,000.
Reliant Energy Minnegasco Dakota Station CHP Facility. The Dakota Station, located in Burnsville, Minn., 10 miles south of Minneapolis and owned by Reliant Energy, is a natural gas, peak-demand-shaving facility that is part of the Minnegasco gas distribution system. In the spring and summer months, when natural gas prices are lower and there is lower gas demand, the facility cools natural gas to –260F to liquefy it and then stores it in a 12 million – gallon holding tank for use in the winter months, when the demand for natural gas is higher. The liquefaction process draws about 500 kW. The stored gas is equivalent to approximately 1 billion cubic feet of natural gas. By storing natural gas like this, Minnegasco can ensure lower costs for its customers and offset the need to provide additional expensive pipeline capacity to meet peak natural gas demands in the winter.
Dakota Station applies the exhaust heat from a 30-kW microturbine, used to reduce the peak energy demand during the liquefaction process, to provide dehumidification in the summer and heating in the winter to the facility. Basically, the facility saves on energy costs by balancing energy demand; it stores energy (liquefying gas) when it is less expensive (summer) and then makes it more readily available when it is more expensive (winter).
Although the Dakota Station is not a typical commercial installation, it clearly exemplifies the positive results of using CHP, in that it:
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Reduces monthly energy costs by offsetting grid usage. (Installed cost was $45,000, with a simple payback of 2.5 years.)
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Provides further energy savings through use of exhaust heat for plant cooling and heating.
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Achieves the highest efficiency when exhaust heat is recovered for use in heating or cooling applications.
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Reduces maintenance costs versus other electric generation technology.
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Reduces emissions versus other electric generation technology.
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Contributes to utility customers’ understanding of advanced energy technology.
A Solution That’s Ready Today
CHP is first and foremost an energy efficiency option. It allows users to produce needed electricity, heat, and mechanical energy while using as little fuel as possible. As an efficiency technology, CHP can lower overall energy demand, reduce reliance on traditional energy supplies, make businesses more competitive, cut greenhouse gas emissions, and reduce the need for infrastructure improvements.
Because of its inherent efficiency, performance, and reliability, CHP is an effective near-term solution that can address the nation’s current and future energy needs (see table).
Significant energy and carbon savings today, but more tomorrow. This estimate of the potential for CHP used 2006 data (first data column) to compute the annual fuel use and CO2 emissions of existing CHP facilities. Savings are based on comparison with facilities using separate heat and power consisting of on-site thermal energy supplied by the same fuel type and average fossil-based electricity generation with 7% transmission and distribution losses. The second column of data extrapolates existing CHP performance to proposed 2030 capacity, using the same assumptions as for the 2006 base case. Source: U.S.EIA Annual Energy Outlook 2008 and eGRID, EPA
—Angela Neville, JD is POWER’s senior editor.
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