Power Line Q&A: Chiller efficiency

Here's a recent question and answer from Western's Power Line. To ask your own question, call the Power Line at 1-800-769-3756. Our energy experts are there to give you the answers.

Question:

What's the latest in chiller technology? Which energy-efficient chillers qualify for utility rebates?

Answer:

There have been a lot of improvements in chiller technology in the past few years, partly because of the demand for higher efficiency (enlarged condensers, enhanced controls, improved compressors) and partly because of better sizing of applications. The minimum efficiency recommended by ASHRAE for chillers over 300 ton capacity is 0.68 kW/ton, while the minimum efficiency recommended by the Federal Energy Management Program is 0.56 kW/ton. The best available efficiencies available are in the range of 0.47 kW/ton./p>

There is a good description of high efficiency chillers on the FEMP Web site at www.pnl.gov/techguide/7.htm. While you're on that Web site, look at some of the other technical guides on high-efficiency air conditioning equipment, heat pumps, and other HVAC applications. FEMP also has a lot of information available on energy efficient chiller procurement on the Energy Efficiency and Renewables Network Web site at www.eren.doe.gov/femp/procurement/le_chiller_ find.html. Be sure to look at the buyer tips and cost effectiveness examples linked to that Web site.

Utility incentives for equipment efficiency upgrades will vary among utilities...

The Energy Star program sponsored by EPA has product efficiency recommendations on selecting both air-cooled and water-cooled chillers. The Energy Star Web site for information on electric chillers is www.epa.gov/ nrgystar/purchasing/6fff_wce_ chillers.html. While you're on the Energy Star Web site, take a minute to look at the other information they have on non-residential HVAC equipment.

The American Council for an Energy-Efficient Economy publishes a "Guide to Energy-Efficient Commercial Equipment," which lists certified performance of most commercial equipment. You can find out more about this guide at www.aceee.org/press/ceg.htm. In the case of chillers, much of the equipment these days is being custom designed to meet owner-specified operating conditions with very efficient performance. Design engineers are more often defining integrated part-load conditions as the basis for selection rather than full-load operating performance.

Existing chillers 10 years old and older can have efficiencies less than 0.8 kW per ton of cooling, whereas new chillers can have efficiencies below 0.5 kW per ton of cooling. Chillers operating more than a couple thousand hours a year may provide excellent opportunities for energy savings and are candidates for upgrading based on energy savings alone. If a chiller is due for an overhaul or refrigerant replacement, chances are that a new energy efficient machine is cost effective.

Utility incentives for equipment efficiency upgrades will vary among utilities, so you will have to work with each utility program to find out its own requirements. Obviously, the reduction in peak demand between a minimum efficiency and a high efficiency chiller can be significant (up to 40 percent or more reduction in peak load), and power savings will be significant if the equipment is operated a large number of hours annually.