Recognizing combined heat and power (CHP) as a realistic, near-term option for reducing energy use and emissions, the U.S. Department of Energy (DOE) has actively supported cost-shared technology R&D and demonstration projects during the past 10 years - contributing to 85 GW of CHP power in more than 3,500 facilities in the United States. This article showcases four successful DOE cost-shared CHP demonstration projects using a variety of technologies, and illustrates the broad applicability of CHP across industrial, commercial, and institutional facilities.
DOE’s technology development focuses on gas-fired advanced reciprocating engine systems, industrial gas turbines, microturbines, fuel cells, and thermally-activated technologies. DOE has also focused on integrated energy systems (IES) - combining power generation and heat recovery technologies to develop packaged and modular ‘plug and play’ systems. The following case studies illustrate some of these technologies in action.
This Verizon Switching Center uses fuel cells and reciprocating engines to power the facility. (Click on the image for an enlarged view.)
The Verizon Telecommunications Switching Center in Garden City, N.Y., is a 292,000-square-foot building that houses 900 employees and provides telecommunications services to more than 35,000 customers on Long Island. The facility is the largest fuel-cell-based CHP installation providing energy service to a Verizon facility. It uses seven 200 kW, natural-gas-fired fuel cells paralleled with the grid, three reciprocating engines, two 70-ton absorption chillers, and a heat recovery steam generator (HRSG) to provide power, cooling, and heating to the facility.
The CHP system became operational in June 2005. A unique feature of this system is that the fuel cells and reciprocating engines are used to supply energy to the facility at different times and outputs depending on the facility’s energy needs. For example, the system recovers high-grade waste heat from the fuel cells for use by the two absorption chillers to cool the central office in the summer. During the winter months, the same waste heat is used by the HRSG for heating to supplement existing boilers.
On an annual basis, this combination of CHP sources provides 16 MMBtu of useful thermal energy and 38,000 Btu of useful electricity, and offsets 11.1 million pounds of CO2. With an annual energy savings of $0.5 million, and implementation costs of approximately $13 million, the payback period is about 10 years.
Verizon hopes to replicate this CHP system within their portfolio of central offices, using lessons learned. According to Jeremy Metz, energy team leader, Verizon Strategic Sourcing, the company hopes to “learn all about operating and maintaining fuel cells now so when their prices come down, we can install them efficiently and cost-effectively.”
Arrow Linen is an industrial laundry facility located near Prospect Park in Brooklyn, N.Y. The facility uses large quantities of hot water, electricity, and steam to clean uniforms, table linens, and other items for restaurant and institutional customers. In April 2003, two natural-gas-fired 150kW reciprocating engines were installed to produce electricity and preheat hot water. The engines run six days per week for 10 to 14 hours each day and are automatically controlled to match their electrical output to the building load so that no power is exported to the utility. The system provides approximately 75 percent of the required electricity to run the facility.
Because the engines operate only when the process is active, the CHP system achieves a consistently high efficiency of more than 80 percent. Additionally, this CHP installation uses nearly all the available heat recovered to meet process hot water loads (2,000 MBtu per hour), and achieved monthly cost savings of $10,000 and annual utility savings of $120,000 with a simple payback of three years.
The CHP system at the Fort Bragg Army base provides heating and cooling services for 50 barracks and buildings. (Click on the image for an enlarged view.)
Fort Bragg in Fayetteville, N.C., is one of the world’s largest U.S. Army installations. The Army post houses the 82nd Airborne Division and the XVIII Airborne Corps, along with Army Special Operations Command and other rapid deployment units. Thanks to development of the system through DOE’s Integrated Energy System (IES) program and financing from an energy savings performance contract (ESPC) with Honeywell, Fort Bragg installed a CHP generation system at the 82nd central heating plant in June 2004.
The innovative CHP system at Fort Bragg is used to drive the plant’s heating and cooling services for about 50 barracks and buildings. It directs waste heat from a solar 5 MW gas turbine generator to a heat recovery steam generator to produce hot water for heating. During summer, waste heat from the turbine is used to drive an absorption chiller to produce 1,000 tons of chilled water. The system can seamlessly switch from base operations in case of an emergency, which allows the installation to operate as an “island” during prolonged electrical outages on the main grid. Additionally, the system has improved fuel efficiency of 33 percent to 45 percent to more than 70 percent, and is expected to save the base about $1.8 million per year. Total energy costs have been reduced by more than 25 percent.
This CHP installation is also unique in that Fort Bragg operates it with optimization software to determine the best operating strategy on an hourly basis. The software is part of the plant’s control system and considers electric, heating, and cooling loads; fuel prices; the electric grid; equipment performance; and current weather data to determine how to meet these loads using the CHP equipment, grid power, and supplementary heating and cooling equipment.
RONALD REAGAN PRESIDENTIAL LIBRARY AND MUSEUM AND AIR FORCE ONE PAVILION
The 100,000-square-foot Ronald Reagan Presidential Library and Museum in Simi Valley, Calif., is located adjacent to the 95,000-square-foot Air Force One Pavilion (opened in October 2005), which houses a Boeing 707, Marine One helicopter, Irish pub, and special exhibits. A cogeneration system, including the use of 16 60-kW microturbines, generates 95 percent of the buildings’ electricity and captures waste heat to operate absorption chillers for cooling.
The 16 microturbine units are ideal for the Ronald Reagan facility as they can be run at full load and still allow for ramping up or down as needed per various cooling and power requirements throughout the day. Additionally, because the library has environmental constraints in spaces that house important historical documents, those rooms must be kept at a steady temperature and humidity level.
The system at the library includes three UTC PureComfort™ cooling, heat, and power packages - each with four 60-kW microturbines and one 129-ton Carrier absorption chiller. The direct exhaust-fired chillers use thermal energy from the microturbines to create 387 tons of refrigeration for cooling both the Library and the Pavilion. The exhaust from four PureThermal™ 60-kW turbines, which produce 960 kW, raises the temperature of water to heat the Pavilion during winter months. This system operates at 80 percent efficiency, reduces greenhouse gases by about 40 percent and NOx emissions by 90 percent from grid generated power, and has been estimated to save approximately $300,000 in annual operating costs.
The UTC PureComfort System was developed with support from DOE. The system at the Ronald Reagan Presidential Library is one of more than 20 replicable systems that have been installed since the design and demonstration of the initial system. Reprinted and adapted with permission from the Winter 2009 issue of
Energy Matters, a quarterly publication from the U.S. Department of Energy’s Industrial Technologies Program. For the latest issue and archived issues of
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