A series of new and innovative projects at Cornell’s Central Energy Plant aims to significantly cut campus water use by millions of gallons a year.
“Water is a valuable commodity, so we want to ensure we’re not being wasteful,” said Garret Quist, a utilities engineer in Cornell’s Infrastructure, Properties and Planning division, who has designed each system.
Feeding the classroom, research and residential buildings, the turbines and boilders at the central energy complex generate all of the campus steam and much of the campus electricity – making (with the hydroelectric plant) about 220 million kilowatt hours annually – but using less than half the energy of conventional power plants.
Exiting steam is piped to the buildings, keeping campus toasty. As the steam turbines convert steam to electricity, inefficiencies in the generator create waste heat that must be removed to keep the generator from overheating. During summer months, a portion of this heat was removed using cool potable water. After cooling, the water went down the drain, a loss of 475,000 gallons annually.
To stanch water waste, last summer Quist designed a new way to cool the windings (coils) using a heat exchanger-based water-cooling system from Cornell’s campus chilled-water network. The new system, built for about $42,000, saves the university $24,000 annually in water, sewer and treatment costs, and reduces the annual 475,000-gallon water loss to zero.
“During the winter months, the waste heat from our generators is recovered and put back into service to heat campus,” said Lanny Joyce, director of Utilities and Energy Management. “Now in summer months, this cost-effective new system eliminates the use of potable water for chilling and replaces it with closed-loop water,” he said.
The next project aims to save even more water: Cornell’s steam-heat delivery system requires high-quality water. To constantly monitor and assess water quality, scalding boiler water must be cooled before testing. In the old system, potable water was used to both condense steam and cool water used by a continuous sampling system, which sent 4.2 million gallons of potable water down the drain annually – after use.
Now, Quist is installing a chilled-water cooling loop to transfer heat from the boiler water to the colder, closed-loop chilled water. That new heat-exchange system is under construction for $55,000, but it will save the university $75,000 a year in water and sewer costs, said Quist: “That’s a nine-month payback, which means it will pay for itself by the end of 2016.”