On-Site Electric Generation Supplies Buffalo Area Facility
Oakwood Health Care Center is 200-bed residence providing skilled nursing, subacute care and rehabilitation in Williamsville, New York. Williamsville is 10 miles northeast of Buffalo. The health care center is operated by ElderWood Senior Care. Easily recognized by its unique, three-story atrium, the facility is located adjacent to picturesque Bassett Park. The Oakwood facility has gained recognition for its high quality, personalized senior health care, and more recently for its advanced, self-sufficient electric energy supply system.
ElderWood Senior Care operates 13 health care centers and assisted living residential centers in Western and Central New York. In the past two years ElderWood has completed energy projects at four of its facilities including the installation of an electric boiler and thermal storage for HVAC load management, and microturbines. The objective of the Oakwood project was to utilize an off-grid 850kW, triple-redundant cogeneration system that optimizes both reliability and operating costs.
Structured as Performance Contract
The project was done using a performance contract with Gerster Trane Energy Services of Buffalo. The system includes diesel electric generation, engine heat recovery, a new Trane electric air-cooled chiller, new CALMAC thermal storage Off-Peak Cooling tanks, d a comprehensive control system. The experience gained through the demonstration of this system may be applied to future installations at other ElderWood Senior Care sites.
The co-generation portion of the project was completed with the assistance of a grant from the New York State Energy Research and Development Authority (NYSERDA). The new system is isolated from the electricity grid and allows ElderWood to maintain power during blackouts. It is estimated it saves the facility nearly $100,000 in annual energy costs. The cost reductions come both from more attractive energy rates, and from the elimination of utility demand charges. The project was completed and went into full operation in January 2001.
"This project allows ElderWood to maintain quality service for its residents and save tens of thousands of dollars in energy costs at the same time," said NYSERDA President William M. Flynn. "NYSERDA has the technical and financial assistance available to not only help health care facilities, nursing homes and assisted living communities, but help other businesses and institutions in New York State save money through energy efficiency."
Annual Savings Approach $100,000
State senator Mary Lou Rath noted, "Energy conservation is a must as we go forward, for environmental and cost reasons. NYSERDA, working with Gerster Trane Energy Services, has put forth a tremendous measure here that will save ElderWood almost $100,000 in annual energy expenses. In the face of rising prices and demand, this partnership represents the kind of thinking necessary for the future and will serve as a role model that other companies and local governments can emulate."
Designed by Gerster Trane Energy Services, the combined heat and power (CHP) system at ElderWood uses two natural gas engine-generator sets and one diesel engine that combined can produce up to 850 kW of electricity. Using a heat recovery system, the heat from the engines is used for pre-heating water for the existing boiler and domestic hot water systems. An Off-Peak Cooling thermal storage system, allows Oakwood to optimize its generating load profile and install engines that are smaller than if they had been if sized for the cooling load without storage. Using Off-Peak Cooling, the engines can be run at more efficient levels at night, supplying the chiller to make ice for cooling for the next day. This approach increases electric generation efficiency and reduced the project's initial cost. The effect of the CHP system is the removal of approximately 400 kW of peak load from the electricity grid.
Gerster Trane’s energy services manager, Steven Aughey, points out that the design of this system actually increases the facility’s potential reliability over grid-supplied energy. The full energy requirement of the facility can normally be met by one of the two 300 kW natural gas-fueled Waukesha generator sets. The two units are used on alternating three-month schedules, with the unit not in use on continuous standby, ready to pick up load if required. A third unit, a diesel fuel fired 250 kW unit, is an additional standby resource.
System Makes Ice at Night
As electric load declines in the evening, the generator output is shifted partly to making ice in the two CALMAC 570 Ton-Hr IceBank tanks. Making ice at night is the process of generating and storing cooling capacity at night-time to reduce peak daytime kW demand, energy usage.
The insulated ice tanks are partially buried in an outdoor location, near the generator and chiller facilities. Chilled fluid is produced with the Trane Series R™ air-cooled chiller, Model RTAA. This unit has a nominal rating of 150 tons, and is operated cooling a 25% glycol solution at temperatures down to 25F. This low-temperature fluid either goes to a plate-and-frame heat exchanger cooling a secondary fluid for direct building cooling, or to the IceBank tanks for ice making.
The air-cooled chiller approach was taken because of its simplicity of operation, and because it is so well suited to ice making. The units require no condenser cooling piping or pumps, and no cooling tower, thus operation and maintenance is simplified. Refrigeration is achieved with two refrigerant loops operated by screw compressors. Screw compressors are an attractive solution because of their inherent simplicity, reliability, and ability to efficiently make ice for storage.
The entire system, including cooling, ice making, engine operation, heat recovery and facility environmental management is overseen with a Trane Tracer Summit™ building automation system. This control system allows operators to observe that status of all equipment, adjust setpoints for cooling and heating, and optimize heat recovery and thermal storage equipment. The flexible Tracer Summit system allows the electric generation, heat recovery, ice making and building comfort system to operate unattended around the clock.
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