ASHRAE Journal - November 2019 - 28

TECHNICAL FEATURE

Existing Alternative Water Cooling Systems
There are many projects around the globe where
river, lake and ocean water is used for purposes beyond
industrial, and many of these locations are where
electricity, fuel and water are not abundant. Among the
best locations are islands, and such projects are either in
design or underway, such as Mauritius and Honolulu, or
complete, as in many building projects along the Great
Lakes such as Enwave Deep Lake Cooling,5 the HSBC
Building, Hong Kong,6 and the more detailed examples
below.

Cornell Lake Source Cooling Project
In Ithaca, N.Y., Cornell University undertook the first
deep lake source cooling project in the United States
(Figure 5). The system began operation in July 2000 and
supplies 20,000 tons (70 337 kW) of cooling load for the
university as well as other buildings in the city of Ithaca.7
The cost was about US$58.5 million. This replaced the
need for mechanical cooling space as well as being lower
28

ASHRAE JOURNAL

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N O V E M B E R 2 0 19

EQUIPMENT TRADITIONAL CHILLED WATER RIVER, LAKE, OCEAN COOLING
KW/TON
KW/TON

Chiller

0.40 - 0.54

-

Chilled Water Pumps

0.05 - 0.08

0.05 - 0.08

Cooling Tower

0.08 - 0.12

-

Condenser Water Pumps

0.07 - 0.11

-

River/ Lake/ Ocean Pumps

-

0.08 - 0.13

Total

0.6 - 0.85

0.13 - 0.21

Minimum Difference

0.39

FIGURE 5 Cornell Lake Source Cooling project diagram.

Cornell University

Cayuga Lake

Heat Exchange
Facility

60°F
45°F

48 - 56°F
39 - 41°F
10,400 ft

12,000 ft

than an estimated cost of about $70 million (1999) for
six new cooling plants on the campus. Data science,
computer laboratories and other sensitive equipment
were to be supported by the new cooling scheme. The
system eliminates refrigerants and the operational
energy savings over the old chiller plant systems
averages at about an 86% improvement.
The lake source cooling system draws from a depth
of 250 ft (76 m) to get water at 38.8°F (3.8°C) to 41°F
(5.0°C) from the bottom of the lake. This water is then
cycled through a heat exchanger near the shore of the
lake then back out to the lake at a depth where the outlet
temperature more closely matches the average stratified
lake temperature.
The closed loop cooling water system for the university
needs much less water treatment and doesn't consume
water for evaporative cooling. Pumps supporting the
water flow on each side of the heat exchanger vary their
speed as needed to ensure adequate cooling is available
for the university year-round.

IMAGE COURTESY CORNELL FACILITIES AND CAMPUS SERVICES

The risk for river, lake and ocean water cooling systems
from storms, watercraft, and biological sources (fish,
shellfish, mollusks, etc.) should be noted and explored
based on the location. Although pumps can be placed in
parallel, the intake piping from a river, lake or ocean is
often not redundant. Due to this, the piping at the shore
line can be buried or otherwise hidden since this is the
most vulnerable section.
While typical mechanical plants are more flexible for
location, they also have vulnerabilities due to having
more equipment that can fail without a rigorous
maintenance program. For high-availability needs, this
can be an issue if personnel are inexperienced or not
trained in the details of the system such as refrigerant
types, condenser water treatment chemicals, controlling
valves and energy management system, or balancing to
achieve optimum efficiency.

water cooling.10

450 ft

Reliability Comparisons

TABLE 1 Comparison of traditional chilled water systems and river, lake and ocean

250 ft

chiller plant is about one-third. For a megawatt (MW)
of cooling required, the amount of savings would be
about 0.135 MW; over the course of a year this would be
over 1 million kWh. Additionally, since the river/lake/
seawater system does not require potable water for heat
rejection, over a million gallons of fresh water per MW of
cooling load would be saved.
ASHRAE Journal - November 2019

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