aqueous fluid, with operating supply
and return temperatures of 30 F and
54 F. The TES is designed to discharge
at flow rates of up to 25,500 gpm or
25,000 tons at the LTF delta T of 24 F,
enough to fully discharge the TES in
under 5 hours.
This particular TES system provides
the following benefits:
• The availability of a low supply
temperature ( 30 F), used to produce
low-temperature air for distribution
in miles of air ducts within the
convention complex, reducing the
size and cost of ducts and fans.
• A larger-than-normal TES supply-to-return temperature difference ( 24
F), reducing the volume versus that
required for conventional chilled-water TES and achieving a tank
footprint of only 0.5 sq ft/ton, less
than that of conventional (non-TES)
• Reduction in peak electric demand of
approximately 20 MW, with associated
reductions in operating demand and
• A fully installed (1994) capital cost
for the tank (including its LTF) that
was under $40/ton-hr of TES capacity
and under $200/ton of discharge
capacity – far less than the cost of
equivalent conventional (non-TES)
chiller plant capacity.
• Avoidance of the need for ongoing
water treatment, as the chemicals
used in the aqueous LTF provide
essentially permanent water treatment for control of both corrosion
and microbiological activity.
• Extremely low maintenance requirements and a continuous successful
operating history (of 18 years and
counting), not unlike many other
TES installations dating to the 1990s
and older. TES equipment is generally quite simple and static, with a
longer expected operating life than
that of mechanical chiller plant
Finally, yet another powerful testimony to the value of TES for district
energy systems is the wide incidence of
satisfied system developers, owners
and operators who have installed multiple TES systems at one or more of
Table 3. Examples of District Cooling Systems With Multiple TES Installations.
District Energy System
TES Type Number
University of Arizona-Tucson
Ford Motor Corp.
U.S. Veterans Administration
District Energy St. Paul
University of Texas System
Tabreed, Abu Dhabi, UAE
State Farm Insurance
Toyota (U.S. and Canada)
University of California System
Trigen (Some systems later sold)
California State University System
Northwind (U.S. and Canada)
Saudi Electricity Company
Chilled water, Ice
Source: The Cool Solutions Company.
Peter B. Myers Peter B. Myers
Courtesy Chicago Bridge & Iron Co.