Trane TRG-TRC016-EN manual Chiller Efficiency Improvements, Low-Flow Systems

period three

System Variations

notes

A third method of using an “alternate” fuel is actually to use the same fuel (electricity) but to use it at a different time. The highest electricity costs occur at the time of highest demand. For example, a real-time-pricing rate for electricity may be $0.50/kWh at times of peak demand during the day but only $0.03/kWh at night. By using either ice or chilled water to store cooling capacity at night when the cost of electricity is low, and then using that stored energy to help cool the building during the day when the cost of electricity is high, total electric costs can be reduced substantially. Although thermal storage does not use a different fuel, it is certainly an option for avoiding high electricity costs during peak periods.

Chiller Efficiency Improvements

chiller efficiency(kW/ton)

0.9

COP

0.8

0.7

0.6

kW/ton

0.5

1970 1980 1990 year

8.0	chiller
7.0
	efficiency
6.0
5.0	(COP)
4.0

2000

Figure 68

Low-Flow Systems

Building owners are becoming more conscious about how improved efficiency reduces system operating costs and overall environmental impact. Typically, the largest piece of equipment in the chilled-water system is the water chiller. However, it is also the most efficient piece of equipment in the system.

Figure 68 shows the dramatic improvements in chiller efficiency, at standard ARI conditions, since 1970. High-efficiency compressors and motors, economizers on multiple-stage centrifugal compressors, more heat-transfer tubes, and tubes with special geometry to enhance heat transfer in both the evaporator and condenser, have all contributed to these efficiency improvements. Manufacturers continue to strive to improve chiller efficiency by redesigning chiller components.

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