I have 1 set 350 tons centrifugal chiller, i tune the chilled water set point from 8 degree C to 11 degree C.?

Question

How much saving i can get from 3 degree C difference in term of kwh.

Answer 1

Sony Disc Manufacturing operates a 365,000-sq-ft compact-disc manufacturing facility in Springfield, OR. The six-year-old plant employs approximately 400 employees and has the capacity to produce as many as 12 million discs/month in a process that requires nonstop, 24-hr cooling. The year-round demand for chilled water is created by the need for humidity control, an extensive exhaust system, and production equipment which requires cooling.

When the facility was built, Sony installed two constant-speed centrifugal chillers, one a York (York, PA) 400-TR unit and the other a 700-TR unit. During winter months, the average load was 300 to 350 tons and was carried by the smaller unit.

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During warmer summer months, the cooling load reached as high as 900 or 1,000 tons and required the operation of both chillers. This meant that the hvac system could not offer the redundancy critical to a 24/7 operation.

"Our production equipment relies on chilled water, so we needed to ensure a constant supply, regardless of weather conditions or other events affecting conditions within the facility," says Steve Kreuzer, facilities engineer at Sony.

The company decided last year to purchase a third chiller. "Our initial thought," recalled Dan Riney, Sony's facilities engineering manager, was to provide redundancy year-round by purchasing one of the cheaper chillers on the market, figuring we would rarely require its services."

VARIABLE SPEED MAKES FOR SYSTEM HARMONY

However, as the purchase process proceeded and they talked with Dan Mitchell, technical sales representative with Applied Systems Oregon (ASO, Vancouver, WA), the company realized a York 700-TR centrifugal chiller equipped with an OptiSpeed [TM] vsd offered significant energy benefits they hadn't considered.

The OptiSpeed seemed to be the logical choice for the Sony facility, whose chiller system operated at off-design conditions (lower loads and especially lower entering condenser-water temperature [ECWT]) for 90% or more of its operating hours.

A YorkCalc energy analysis using data from Sony's hvac system showed the York chiller, using ECWT as low as 55[degrees]F instead of the 70[degrees] limit of the existing chillers could save Sony more than $20,000 annually in energy costs. Based on this report, Sony purchased the chiller.

Today, the York 700-TR variable-speed chiller is the first machine to be brought on-line because it is less expensive to operate than the 400-TR constant-speed chiller, even during low-load periods that are typical during cooler winter months.

"It is now the lead chiller," said Kreuzer, "running year-round and providing savings that meet or exceed those of the original report." "One of the biggest advantages the chiller offers is the ability to run colder condenser water. The energy savings from that alone have been tremendous, and we have actually been able to reduce the ECWT for more hours of the year than were projected when the original energy assessment was made." he added.

An increase in the leaving chilled-water temperature (LCHWT) contributed additional savings. Sony engineers reset the LCHWT from 45[degrees] to 50[degrees] to take advantage of chiller energy savings as high as 3%/degree of reset.

EFFICIENCY HITS ALL THE RIGHT NOTES

Even the local electric utility is impressed with the savings Sony has posted, basing its reaction to meter readings it collected before and after the chiller installation. According to Keith Lockhart, energy and conservation services manager at the Springfield Utility Board (SUB), the vsd chiller and the LCHWT reset saved Sony 404,000 kWh/yr, resulting in an Energy Savings Plan award from SUB to Sony of $32,352.

The actual savings verified by SUB do not take into account additional savings resulting from a lower ECWT. "After we lowered the ECWT for the York chiller, we continued to collect data and share it with SUB. The analysis showed that our savings appear to be even better than our initial calculations predicted," Riney says.

"Some days," Riney continues, "we run our constant-speed chillers just to be certain they are working and will be available as backups. If you look at our daily data on those days, it is very easy to discern exactly when those chillers come on-line; the difference in efficiency is that obvious."

"The cost projections have been difficult to track with the recent volatile energy prices and some operational changes we have made, but the energy savings are real. Additional project work, such as vsd's on the York pumps have contributed to the savings, but the electrical energy used for cooling dropped an average of 1,251 kWh/day," Riney added. "The historical savings attributable to the chiller and the related projects actually have approached 460,000 kWh/yr."