Cogen with Lean-Burn Cuts Health-Care Cost
Staff -- Consulting-Specifying Engineer, 6/1/2002
When it came time for administrators at St. Catharines General Hospital in St. Catharines, Ontario, Canada, to consider ways to control costs, energy expenditures jumped out.
As a large facility in a cold climate, the hospital had a significant heating load for more than six months of the year. And its laundry facilities had a year-round need for hot water. With rising fuel costs for space and water heating, combined with increasing costs for electric power, St. Catharines was looking for a solution to several energy-use issues.
For help they turned to St. Catharines-based Peninsula Engineering, whose engineers determined that the facility was an ideal candidate for a combined-heat-and-power (CHP) system, with one fuel source producing two forms of energy—in this case, electric power and hot water. Engineers also recommended lean-burn natural-gas-engine gensets with heat recovery boilers. Together, the generator sets and the heat from the engine exhausts and cooling systems would provide all the electricity, heat and hot water needed by the facility.
The installation consists of two 1.25-MW-rated lean-burn generators with a total electrical output of 2.5 MW at 600 volts. The total thermal output—5.12 million BTU/hr—is enough to supply winter space heating loads, domestic hot water for laundry and other needs, and excess capacity for future growth.
Heat is extracted from the engine in two ways: from the exhaust gases and from the engine cooling system. A heat-recovery boiler, located in the engine exhaust stream, transfers the heat energy from the 500ºF gasses to water circulating through the hospital's heating system and to the domestic hot water supply.
A separate heat exchanger transfers the waste heat from the engines' cooling systems to the hospital's hot water systems. By extracting as much energy as possible from the natural gas, the generators and heat-recovery boilers produce an electrical efficiency of nearly 39% and a thermal efficiency of nearly 46% for a combined efficiency of about 84%.
Sized to supply all of the hospital's electrical needs, the units also generate enough power to facilitate load-shedding in cooperation with the local utility at times of peak demand. This benefits the hospital economically and helps the local utility to defer capacity additions and associated expenses.
The system also features digital master controls and utility paralleling switchgear, which greatly simplify system operation. Designed and built to work as an integrated system, the generators, controls and switchgear provide easy installation, intuitive operator control, sophisticated monitoring options and exceptional reliability.
From Pure Power, Summer 2002
