Magazine article Health Facilities Management

Chiller Up: Technology Advances Drive Major Efficiency Gains for Hospitals

Magazine article Health Facilities Management

Chiller Up: Technology Advances Drive Major Efficiency Gains for Hospitals

Article excerpt

The latest chiller technology features variable-speed drive, dedicated heat recovery and oil-free operation. These features are available to hospital facility managers who seek to improve efficiency. However,

determining the proper number of chillers needed to maintain maximum performance is just one factor to consider when choosing and implementing these systems.

Proper selection and use are critical because chillers are a major energy-using component in most facilities. Chillers that run inefficiently can result in decreased equipment reliability, increased maintenance intervals and a shortened life span.

Latest advances

Experts agree on the types of technological advances available. Ron Holdaway, P.E., C.E.M., LEED AP, senior design principal, Smith Seckman Reid, Nashville, Tenn., says oil-free chillers with magnetic bearings or ceramic bearings are among the latest features available. These designs improve chiller efficiency and, more importantly, reduce bearing and motor failure and reduce preventive-maintenance costs.

Another trend is dedicated heat-recovery or heat-pump chillers, which are designed primarily for heating rather than cooling, he says. Their purpose is to capture low-grade building heat and reuse it for space heating, reheating and for preheating domestic water.

"Central geo-exchange systems represent another trend for both chillers and boilers, allowing use of traditional air-side HVAC mechanical systems such as fan coil units or VAV [variable air volume] systems," Holdaway says. A geo-exchange system consists of a vertical or horizontal ground-source closed loop, a pond or other surface-water feature coupled to the building's HVAC system to reject or add heat to the building as required.

"Design features such as heat recovery options, ice-making capability and free-cooling are not necessarily new technologies but these and other energy-saving features are being specified more frequently today than in recent years," he notes.

Richard D. Hermans, P.E. HFDP, director of training and advanced applications for Daikin McQuay, Minneapolis, says modular chiller designs are becoming popular, as are variable-speed drives and oil-free magnetic bearing compressors. Controls continue to evolve, he adds, and soon will include an interface to future smart electric grids. Today's smart controls know when it's better to run multiple chillers at part-load, he notes.

Elsewhere, the chiller-heater is enjoying a resurgence in health care applications. This involves a refrigeration machine specially built to produce unusually hot condenser water that can be used for heating domestic hot water or to produce reheat water. "This concept has been around for a long time but is making a comeback, with new designs of these machines now available," Hermans notes.

Tube efficiency is another important trend in chiller technology, says Derrick Shoe-make, project engineer for Hudson Technologies, Pearl River, N.Y., which recently purchased Efftrack (Efficiency Technologies Inc.), Tulsa, Okla. Tubes are getting more efficient by utilizing surface enhancements such as rifling techniques, which provide greater heat transfer through a larger surface area, he notes.

More efficient compressors are making chillers more cost-effective as well, he adds. "Some new compressors have magnetic bearings, which not only reduce friction and heat, but reduce noise levels as well. The downside to magnetic bearing compressors, however, is [that] the size of chillers available is usually less than 700 tons."

Push for perfection

Just how efficient are the latest chillers and what level can they achieve? According to Hermans, no chiller can surpass the perfect Carnot efficiency. However, the technology of the newest chiller systems has gotten close to this level of perfection when the chillers are running at part-load. "This suggests that some chiller types should be sized for peak load, but operated at part-load as much as possible. …

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