Page 356 - HVAC Pump Handbook

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Source: HVAC Pump Handbook

Chapter
13

Pumping Open Thermal

Storage Tanks

13.1 Introduction
Thermal storage in the HVAC industry consists of both hot and chilled
water storage. Hot water storage has not been prevalent, since it is not
necessary for most hot water systems. As energy conservation grows
with large chilled water plants, there may be some economic reasons to
store hot water that is generated by the heat rejection from chillers.

13.2 Cool Thermal Storage
Cool thermal storage in HVAC systems has become popular in
attempts to reduce overall energy costs. The driving force has been
the demand charges put in place by the electric utilities as they
attempted to reduce their electrical demand due to cooling load dur-
ing the afternoon hours of the summer days. This demand charge
necessitated the shifting of this load from the daytime to nighttime
hours. Thermal storage provided this shift, using either ice, chiller
water, or eutectic salt to provide cooling during the peak hours
instead of electric motor–driven chillers.
The disappointing fact of this effort has been that the peak load
was reduced in most cases, but the overall energy consumption was
increased due to the higher kilowatts per ton of cooling required for
chillers making ice or chilled water at night. The mission of many of
these efforts was only peak shaving by the electric utility and demand
charge reduction for the customer, not overall energy conservation.

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