their district energy networks. Table 3
shows some of the many noteworthy
examples.
In Conclusion
TES can, of course, reduce peak
electric power demand and reduce operating energy costs. In addition, for large
applications such as district cooling, the
capital investment in TES is partially (or
fully) offset by reduced capital expenditures in conventional (non-TES) cooling capacity, when executed at times
of new construction, retrofit capacity
expansions or replacements of existing
cooling capacity (i.e., at any time when
investments in cooling capacity are
planned). This produces a very short
simple payback or even an immediate
capital savings, sometimes at the multi-million-dollar level.
Other TES benefits often include
reduced energy use (both on-site and
at “source” power plants), enhanced
redundancy and reliability, operating
flexibility and flattened load profiles to
better support the economics of CHP.
TES can often be a key to optimizing a district cooling system – and in
more ways than one.
Survey: TES in District Cooling
Data from hundreds of cool TES installations in both thermal utility and campus
district cooling systems were compiled by this author approximately seven years ago
and are summarized in table 4. The data demonstrate the breadth and depth of TES
use in district cooling systems primarily in the U.S. but also include examples from the
Americas as well as Asia, Australia and Europe. Although an updated analysis of similar
applications has not been undertaken, it is clear that the use of TES in district cooling
applications has continued to expand. (Among the notable recent examples are more
than 200,000 ton-hr of ice TES for a single university campus application in China and
over 700,000 ton-hr of chilled-water TES for a single turbine inlet cooling project in
Saudi Arabia.)
Table 4. Analysis of TES Use by Utility and Campus District Cooling Systems (Through 2005).
Utility
Systems
Identified district cooling installations with diurnal TES
Total TES capacity (ton-hr)
Average TES capacity per installation (ton-hr)
Smallest single TES installation (ton-hr)
Largest single TES installation (ton-hr)
Total peak cooling load served by TES (tons)
Peak cooling load served per installation (tons)
Total peak electric load management from TES (MW)
Peak electric load management per installation (MW)
106
2,610,815
24,630
365
160,000
372,974
3,519
279.7
2. 6
Campus Total District
Systems Cooling
Systems
265
4,419,223
16,676
320
160,000
631,318
2,382
473.5
1. 8
159
1,808,408
11,374
320
93,200
258,344
1,625
193.8
1. 2
Author’s Note: The author thanks the
many owners of the TES installations
described in this article for sharing data
related to their systems, as well as the
engineering firms with whom he collaborated during design and execution
of the highlighted installations, including
Burns & McDonnell; Lutz, Daily & Brain;
Morrissey Engineering Inc.; and Stellar.
Latent Heat (Ice) TES
Number of installations
Portion of total district cooling TES installations
Subtotal of latent heat TES capacity (ton-hr)
Portion of total district cooling TES ton-hours
Capacity per latent heat installation (ton-hr)
Smallest latent heat TES installation (ton-hr)
Largest latent heat TES installation (ton-hr)
27
25%
912,832
35%
33,809
NA
125,000
86
54%
397,850
22%
4,626
320
93,200
113
43%
1,310,682
30%
11,599
320
125,000
John S. Andrepont is the founder and president of The Cool Solutions Company in Lisle, Ill., which provides professional consulting services in the areas of thermal energy storage, district cooling and turbine inlet cooling. Andrepont served on IDEA’s
board of directors for five years and has co-chaired
three IDEA cooling conferences. He has also held
leadership positions in several technical committees of
ASHRAE and in the Turbine Inlet Cooling Association.
A graduate of Rensselaer Polytechnic Institute with
bachelor’s and master’s degrees in mechanical
engineering, Andrepont is an inventor with more than
one dozen U.S. patents. He can be reached at
CoolSolutionsCo@aol.com.
Sensible Heat TES
Number of installations
Portion of total district cooling TES installations
Subtotal of sensible heat TES capacity (ton-hr)
Portion of total district cooling TES ton-hours
Capacity per sensible heat installation (ton-hr)
Smallest sensible heat TES installation (ton-hr)
Largest sensible heat TES installation (ton-hr)
Chilled-water sensible heat TES
Chilled-water (LTF-convertible) sensible heat TES
LTF sensible heat TES
Hot water or hot water/chilled-water sensible heat TES
Sensible heat TES above ground
Sensible heat TES fully below ground
Sensible heat TES partially below ground
Sensible heat TES, unidentified tank location
79
75%
1,697,983
65%
21,493
365
160,000
75
9
4
2
69
8
2
0
73
46%
1,410,558
78%
19,323
NA
60,000
71
4
1
1
53
11
5
4
152
57%
3,108,541
70%
20,451
365
160,000
146 (96%)
13 (9%)
5 (3%)
3 (2%)
122 (80%)
19 (12%)
7 (5%)
4 (3%)
Source: The Cool Solutions Company.
