Heat Pump Reduces Hospital’s Steam Bill By $8,000 Per Day

By Consulting Specifying Engineer Staff September 5, 2006

Like medical centers everywhere, St. Michael’s Hospital in Toronto, Canada, is under budget constraints and constantly seeking ways to pare down operating expenses. The facility’s managers have discovered that energy efficiency can make a tremendous difference in their bottom line.

This 550-bed acute-care, teaching and research hospital, which has served the residents of Toronto since 1892, found a way to save Can$1.4 million annually through a major heating and cooling system retrofit. The project centered on replacing two aging centrifugal chillers with a water-to-water heat pump.

The electric-drive heat pump has reduced the hospital’s steam bill by as much as $8,000 daily during the coldest part of Toronto’s winter, though usual savings range from $2,500 to $6,000 per day, depending on the outdoor temperature. This is accomplished by repurposing heat discarded from the facility’s air-handling system and water-cooled chillers located throughout the hospital. The heat pump raises the temperature of the recovered heat to warm the incoming ventilation air.

“St. Michaels was using steam, and steam is very expensive in downtown Toronto—$23.00 per 1,000 lbs.,” says Rejean Cormier, sales engineer with Master Group LP, an HVAC equipment distributor in eastern Canada.

The heat pump has also made possible a 36% reduction in greenhouse-gas emissions by reducing the amount of steam the hospital requires. This helps St. Michael’s meet Canada’s emissions-reduction requirements under the international Kyoto Accords and eliminates the equivalent of a year’s greenhouse-gas output by 1,375 cars. As an added benefit, the heat pump uses environmentally responsible R-134a refrigerant. The old chillers used CFC-11 refrigerant, now banned in Canada.

“For us, it was a win-win situation. Not only did we get new equipment, but we got rid of equipment that was environmentally unfriendly,” says Allan Kelly, manager of plant services at the hospital. “We received a certificate of recognition from the Ontario Power Authority for reducing greenhouse-gas emissions.”

The heat pump installed at St. Michael’s uses the compound technology of two centrifugal compressors in series while in heating mode and has a heating capacity of 10,237 MBH at a coefficient-of-performance (COP) of 4.2. A traditional water heater typically has a COP of less than 1.0.

Operating at full load for nine months of the year, a 62°F water stream carrying the recovered heat enters the heat pump where useful heat is created and used two ways: 40

“We have chilled water year-round because certain areas of the hospital require cooling all year round,” says Kelly.

The heat pump features a graphic control center that regulates both the heating output and chilled-water temperature by means of compressor control, anti-surge and dynamic-override control systems. Its main purpose is to prioritize the heating function and adjust, through several function keys on the control panel, to meet the loads at all times.

Graphic control center regulates heat output and chilled water temperature.

The system is part of a wider energy-plant retrofit designed by Ecosystem, Inc., an energy-efficiency contractor with offices based in Quebec and Ontario. Other parts of the $7.9 million project included:

• converting the hospital’s old steam network to a hot-water heating system;

• modifying heating networks to create two distinctive loops, the first one using warm water (heat reclamation) and the second one using hot water (steam heat-exchanger);

• installing a high-pressure humidification system, including reverse-osmosis water treatment;

• switching domestic hot-water production to a central unit to benefit from the heat-reclamation network, while using the steam heat-exchanger for peak periods;

• eliminating cooling equipment that used municipal water;

• optimizing the building’s automation system for maximum operating efficiency year-round.

“The goal of the hospital was obviously to save energy and, up to now, the heat pump shows that it can meet performance and reliability requirements of the system,” says Stephane Michaud, engineer and project manager for Ecosystem, Inc.

For more about the York MaxE water-to-water heat pump and OptiView graphic control center, click here