Renewable Energy: Combined Heat And Power
By Gary McNeil
From the April 2014 issue of Today's Facility Manager
The National Archives and Records Administration (NARA) preserves and provides public access to U.S. government and historical records. The National Archives Building (known as Archives I and located on the National Mall in Washington, DC) houses the original copies of the Declaration of Independence, the Constitution, and the Bill of Rights. In response to Executive Order 13514, which was signed by President Obama in October 2009, NARA established a goal of reducing its energy use by 30% at Archives I as well as its Archives II facility in College Park, MD. This order expanded on the energy reduction and environmental requirements of Executive Order 13423 by making reductions of greenhouse gas emissions a priority, and by requiring agencies to develop sustainability plans focused on cost-effective projects and programs.
After implementing efficiency measures—such as lighting retrofits and solar panels—at its Archives I and Archives II facilities, NARA management then contacted a product and service provider to explore the use of combined heat and power (CHP). Also known as cogeneration, CHP is an approach to generating both electric power and useful thermal energy. This is not a single technology, but an integrated energy system that can be modified depending upon the needs of the end user. By generating electricity on-site and using the heat produced (and usually wasted) by electricity generation to derive steam or hot water, this type of system decreases electricity and boiler fuel purchases.
There are several key benefits of CHP systems. These provide reliable power even during grid outages; the systems can be configured to operate in “island mode” to supply critical electric loads in the event electricity supply from the grid is disrupted. Second, CHP reduces energy costs; superior efficiency can lower facility energy costs by 30% or more. On average, converting fuel to electric power in central power plants wastes about 67% of the fuel energy as heat. CHP systems recover wasted energy to provide heating, cooling, or dehumidification, while achieving total efficiency of 60% to 80%. Thirdly, because less fuel is burned to produce each unit of energy output, CHP reduces emissions of greenhouse gases and other air pollutants.
In researching CHP for its Archives I facility, NARA was also interested in installing this type of system at its Archives II facility if CHP proved successful at Archives I. Reliability was a leading goal. The Archives I building, comprising 983,000 square feet, had recently experienced a grid outage when one of the three 13.8 kilovolt (KV) feeders supplying the facility failed during the same time that a second feeder was out of service for routine maintenance (two operating feeders were required to supply the facility’s electricity needs). It was also important to NARA that the high efficiency of a CHP system would reduce greenhouse gas emissions compared to less efficiently generated grid power.
The product and service provider chosen by NARA for the project engineered and installed two 75 kilowatt CHP modules at Archives I, covered by a 15 year fixed-price comprehensive maintenance contract. To finance the system, NARA used an energy services performance contract (ESPC) with an energy services company (ESCO), on the basis of a successful energy efficiency project that company had completed at the Archives II facility. Interconnection to the electric utility was straightforward, and thanks to the electrical output of the CHP system, the facility can now operate normally using only one of the three 13.8 KV feeders. By recovering otherwise wasted heat from the engine exhaust, cooling system, and engine block, the system now produces the facility’s hot water.
The ESCO paid for system engineering, CHP equipment, and installation, and NARA is paying a portion of the savings from the project to the ESCO. At the end of the seven year ESPC term, NARA will own the CHP system and benefit from the continuing savings.
The system requires approximately 24% less fuel than would be consumed to generate grid supplied electricity and produce hot water with an on-site boiler. The system also prevents emissions of air pollutants, including an estimated 470 tons of carbon pollution annually.
NARA is pleased with the system, which is now in its fourth year of operation. “Selecting the right vendors is key to getting a successful system,” says Ngan Pham, energy manager at the Archives. “Both Ameresco and Aegis [the ESCO and product/service provider] did a great job for NARA.” Pham offers the following advice for facility managers who are considering CHP:
- Be a good partner and keep the lines of communication open in working with the contractor. Make sure the contractor knows what you are looking to achieve with the system.
- Selecting the right size CHP is key. If it is too small, it will not do the job. If it’s too big, thermal or electrical output will be wasted, and the economic performance of the system will suffer.
In 2013, the U.S. Environmental Protection Agency recognized the Archives I system with an ENERGY STAR Combined Heat and Power Award. Based on the success of its Archives I CHP system, NARA installed a similar system at the Archives II facility in College Park, MD and now plans to install additional CHP systems at other facilities.
McNeil is the communications director for U.S. EPA’s Combined Heat and Power Partnership. He holds a BA in Economics and a Masters in Business Administration from the University of Washington.
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