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Air conditioning in the winter
Heat exchanger will save WSU thousands of dollars
Monday, Feb. 4, 2013
By Kaylee Ray, WSU News intern
PULLMAN, Wash. - It may be the heart of winter, but some campus facilities still need a cooling system. Washington State University is in the process of installing a heat exchanger to save energy costs during the winter months.
"Computer rooms produce so much heat that even in the winter you still have to cool them off,” said Terry Ryan, WSU director of energy services.
The WSU Pullman air conditioning system consists of three electrical chilled water plants and a pipe system that brings cooled water to fans at most of the major buildings on campus. As the cold water warms up, it is returned to the chilled water plants to go back through the cooling cycle, where an electric chiller lowers the temperature to about 40 degrees. The cold water supply runs through one set of pipes while warmer return water runs through another set.
The heat exchanger will be used instead of the chiller at the east campus plant, located on Ferdinand’s Lane, Ryan said. The heat exchanger does not require electricity and will save the university $34,000 each winter. One side of the heat exchanger is connected to the supply/return chilled water lines across campus. The other side is connected to the cooling towers at the chilled water plant.
Cold water is piped from the chilled water plant cooling towers to the heat exchanger. As the name of the equipment implies, heat from the return chilled water is transferred to the colder cooling tower water, thus lowering the temperature of the chilled water.
That returning chilled water becomes chilled supply water and flows to campus to provide air conditioning. The now warm cooling tower water returns to the cooling tower where it is cooled and the process can begin again.
"In the winter it is actually cold enough outside that we can produce chilled water without needing to have the chiller actually drive the temperature down,” Ryan said. The water in the chilled water plant cooling towers, in fact, have to be monitored to make sure it does not freeze.
Above the WSU arboretum is a 2 million gallon storage tank where chilled water is often pumped overnight so it can be used the next day.
The new equipment is funded in part by a state grant worth $478,812, a little more than half of the total cost of $848,000. Avista Utilities provides a rebate program for projects that reduce energy use, and WSU anticipates receiving about $85,000 from that program, Ryan said.