Pumping system design significantly affects district cooling system efficiency. Quite often, numerous pumps can be removed to save a facility energy and money. Hemant Mehta is shown here with
23 pumps that were removed from an 18,600-ton chilled-water system. Nine additional pumps were
bypassed. The facility is reporting nearly $1 million in annual cost savings.
Case Study:
Major Cancer Center
In many instances, system optimization can be achieved with simple
solutions. Such was the case at a major
cancer center that had been aggressively expanding its facility and, as a
result, experiencing substantial cost
increases for infrastructure – specifically cooling and power. Plus, its
location makes it subject to an electrical peak-power-reduction program to
ease the grid’s load.
In many instances, system
optimization can be achieved
with simple solutions.
The cancer center realized that
its four chilled-water systems, totaling
18,600 tons of capacity and serving mul-
tiple buildings across the campus, were a
major electrical power draw. The cancer
center brought in WM Group to review
the chilled-water system to determine
how to simplify the system and reduce
peak electric power use. The firm pre-
pared a feasibility study, which included
a detailed survey of site chilled-water
generation, distribution and utilization
systems, and made these observations:
existing injection valves should be
bypassed or set to be completely
open at all times.
• More than 32 pumps should be
decommissioned, of which 23
should be removed from the site.
The cancer center received a
$662,000 grant from a state energy
agency to optimize the system. The
conversion enabled the cancer center
to operate fewer chillers at low-load
conditions. Instead, more chillers were
able to run at their ‘sweet point,’ and
less manpower was needed for their
operation. One operator was particularly
satisfied with the changes that were
made: He said he can now talk next to
the chillers without shouting!
Operating chillers at an optimum
load, removing 23 pumps and bypassing
nine more allowed the cancer center
to reduce its peak power demand by
1. 1 MW. The WM Group study estimated
an annual cost reduction of $600,000;
the client is reporting an actual annual
savings of about $1 million per year.
Numerous other district cooling
systems have similar optimization
opportunities. In fact, a university
medical center in the same city had
a study conducted and was able to
remove more than 20 pumps, which
reduced the peak power demand by
700 k W. The annual savings are
estimated at more than $600,000.
In another example, a Pfizer Inc.
facility had three connected chiller
plants, each operating as a dedicated
plant to serve offices, manufacturing,
laboratories and a data center. Due to
the critical nature of these functions,
the idea of making any changes to
their chilled-water service had always
been viewed as too risky. During winter
months, one 2,000-ton chiller was
supporting only about 300 tons of a
very critical manufacturing process
load. A hydraulic analysis showed,
however, that this plant along with
its cooling tower could safely be shut
down, with the load transferred to
another plant. The plant configuration
was subsequently changed, and the site
has operated in this manner for two
years now, saving significant amounts
of energy. “Had WM Group not instilled
