The story begins in the mid-1990s when Nestlé began a phased replacement of its existing oil-free reciprocating compressors, which were experiencing unacceptably high maintenance costs and down time.
“The recips were old technology in a hot room, which was a bad combination,” according to Lane Hawkinson, National Sales Manager Kobelco KNW Series Oil-Free Air Compressors for Rogers Machinery Company, Inc., of Portland, Oregon. “Nestlé bought their first Kobelco in 1996, then a second in 1998, and two more in 2001. Each Kobelco rejects 11,500 cfm of air at 160°F with high potential for heat recovery.”
An initial cooling plan for the air compressors involved simply ducting the cooling air out the roof. That would dramatically reduce the heat load inside the utilities area, but Nestlé’s global commitment to energy efficiency presented Finn with a challenge and an opportunity: instead of just rejecting all that heat, could it be put to work?
A common method to recover heat rejected from air-cooled compressors is to direct the warmed air via ductwork to a large space, such as a warehouse or garage, to provide interior heating. The need for low quality heating like this is seasonal, however, and because the heating season in California’s Central Valley is short, most of the time the heat still would be vented outdoors. Rather than settle for low quality heat used seasonally, Finn conceived of a system to recover BTUs rejected from the air-cooled compressors to heat water.
“Nestlé is highly tuned into resource conservation,” Finn explains. “In Tulare we’re already at the stage of the game where we’ve pulled the low hanging fruit, so we have to be more creative in finding ways to capture energy savings. With heat recovery from the compressors, I was looking at energy we can use year round, so I had to think about what we use year round in a food production facility. The answer was hot water. We have many hot water stations around the plant for washing, sanitary systems, waste systems and a lot more, and demand for hot water is ongoing.”