ASHRAE Journal - June 2014 - 80

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Employing such an organized and accountable
approach to implementing an all-variable speed chiller
plant will go a long way toward ensuring it will perform
as expected and result in significant annual energy use
savings throughout its lifetime.

all-variable speed cooling technologies both desirable and
attainable. Implementation of optimized variable speed
cooling offers to be an important element in bridging the
gap that is developing between electrical generation and
energy usage in areas of North America

Summary and Conclusion

References

New, all-variable speed chiller plant operating strategies have been developed that are based on the specific
performance characteristics of variable speed chillers and the variable flow characteristics of condenser
pumps and cooling towers. Substantial annual energy
use reductions can be expected from optimized allvariable speed centrifugal chiller plants compared to
constant speed chiller plants with the same f irst cost.
All-variable speed technologies also can be applied to
unitary cooling system products with similar improvements in annual energy use. Because it is estimated that
cooling systems account for more than 20% of the electrical
power generated in the U.S.,10 this potential reduction in
energy, which can be achieved without a first cost premium
in many cases, makes the widespread implementation of

1. The Hartman Company. 2001. The Hartman LOOP Chiller Plant
Design and Operating Technologies: Frequently Asked Questions, March.
2. Redden, G.H. 1996. "Effect of variable flow on centrifugal chiller
performance." ASHRAE Transactions 102(2).
3. Braun, J.E., G.T. Diderrich. 1990. "Near optimal control or cooling towers for chilled-water systems." ASHRAE Transactions 96(2).
4. Cascia, M.A. 2000. "Implementation of a near-optimal global
setpoint control method in a DDC controller." ASHRAE Transactions.
5. Schwedler, M. 1998. "Take it to the limit...or just halfway?"
ASHRAE Journal July.
6. Hartman, T.B. 1999. "'LOOP' Chiller plant dramatically lowers
chilled water costs." Renewable and Advanced Energy Systems for the
21st Century, Lahaina, Hawaii.
7. Guven, H., J. Flynn. 1992. "Commissioning TES systems." Heating, Piping, Air Conditioning Magazine January.
8. Hartman, T. 2000. "Chiller plant control using gateway technologies." Heating, Piping, Air Conditioning Magazine January.
9. Pacific Gas and Electric Company. 2000. "Chilled water plant
design guide." A Report of the CoolTools Project.
10. Sartor, D., A. Chen. 1996. "Green cooling: improving chiller efficiency." Center for Building Science Newsletter Spring.

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ASHRAE Journal - June 2014

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