Re-Commissioning of the Water

Cooling System at Université de

Sherbrooke

Department of Buildings June 2008

• Presentation of the university

• The university’s water cooling system

• Chiller room• Problem• Mandate• Solutions (Phases 1, 2, 3, 4 and 5)• Results• Project costs and grants• Benefits for the university• Conclusion

Department of Buildings June 2008

• 5,000 employees and 15,000 students (full-time equivalent)

• 63 various types of buildings (laboratories, classrooms, offices, residences, sports centre, etc.) for both campuses

• Area of 252,000 m2

• Energy bill exceeding $5.5 million

• A thermal power station with 3 boilers, 3 chillers and the2 main generators

• A network of tunnels and walkways linking most of the buildings. This network is also used for supplying steam, cooled water and electricity from the power station.

Presentation of the university

Department of Buildings June 2008

The university’s water cooling system

Department of Buildings June 2008

The university’s water cooling system

Department of Buildings June 2008

Chiller room

Department of Buildings June 2008

Chiller room (cont’d)

• Chiller No. 1 was installed in 1987 and is a York R-11 centrifugal chiller with a 1000-tonne capacity

• Chillers No. 2 and No. 3 were installed in 2000 and are Trane R-123A centrifugal chillers, with respectively 800- and 1200-tonne capacities

• Peak production is roughly 2400 tonnes (2003 data)

• The water cooling system for air conditioning supplies

23 buildings and operates from May to September (2003 data)

Department of Buildings June 2008

Problem

Around the late 1990s, an increasing number of teaching and research activities at Université de Sherbrooke prompt it to add several buildings

and new equipment for its specialized laboratories. These new facilities cause a constant rise in the demand for cooled water on campus. In

2000, the university adds two more chillers, bringing the total installed capacity to 3000 tonnes.

Department of Buildings June 2008

Problem (cont’d)

In 2003, the university’s chillers and cooled water distribution systems reach their maximum capacity. A study is undertaken to see whether to go ahead with

projects, costing over $1 million in the short term, which will help support the university’s continuous growth. Furthermore, the 3 chillers must operate during heat

waves to meet demand.

Department of Buildings June 2008

Mandate

In the fall of 2003, a working group, composed of technical personnel and operators from the university’s energy station, along with engineers and technicians of

the consulting firm Teknika HBA, is set up at the request of the director of the Department of Buildings. The aim of this working group is to examine and go over

the whole system, including its equipment and operation modes, in order to improve the system’s performance and avoid having to make major investments.

Department of Buildings June 2008

Mandate (cont’d)

The group’s findings show that large quantities of water are handled by the system without any end-use by consumers. This unnecessary handling

of water leads to saturated systems and requires that the chillers be maintained in operation even though they are not essential for handling the

cooling load. A maximum difference in temperature of 7oF was found at the water cooling station between the inlet and outlet of fully loaded chillers.

Department of Buildings June 2008

Solutions – Phase 1 (2004)

• Shutdown of 52 secondary pumps totalling 377 HP and

installation of bypasses with control valves in buildings.

• Installation of a speed selector on 2 of the main 250 HP

pumps and shutdown of a 3rd pump in the station.

• Improvement of controls.

Department of Buildings June 2008

Solutions – Phase 2 (2005)

• Replacement of three-way valves with two-way valves on

cooling coils of ventilation systems. A total of 48 two-way

valves were installed.

Department of Buildings June 2008

Solutions – Phase 3 (2006)

• Replacement of cooling coils on 11 ventilation systems

resulting in a ΔT = 2oF to T = 16oF in these systems.

Department of Buildings June 2008

Solutions – Phase 4 (2007)

• Installation of a bypass so that the two Trane chillers could

operate in series or parallel.

• Replacement of controls and optimization of sequences so

that the two 250-HP feed pumps could operate in parallel

with the speed selectors.

• Replacement of an impeller on a water tower pump and

installation of a selector on another water tower pump.

• Installation of a new 300-tonne winter water tower.

Department of Buildings June 2008

Solutions – Phase 5 (2008)

• Adding of a new 300-tonne centrifugal chiller with a speed

selector to optimize cooling during mid-season and winter.

Department of Buildings June 2008

Results

Department of Buildings June 2008

SummerArea

(m2)Flow

(GPM)

ΔT(oF)

Peak capacity

of station

(T)

Chillers in operation

kW/T

2003 232,000 8200 7 2400 3 1.2

2005 240,000 5300 9.5 2100 2 0.95

2007 252,000 4400 12 2200 2 0.8

Project costs and grants

Department of Buildings June 2008

Phase Cost GrantkW/h saved

SavingsPP*

(years)

1 to 3 $475,000 $190,500 1,269,000 $63,450 4.5

4 $313,000 $99,315 930,000 $46,500 4.6

5 $330,000 $97,965 600,000 $30,000 7.7

* PP = payback period

Benefits for the university

• Lower maintenance due to the removal of 52 secondary

pumps.

• Replacement of dilapidated and inefficient coils.

• Replacement costs for system pipes and adding of new

chillers avoided due to the reduced flow of circulating

water and recovery of this capacity for future buildings.

Department of Buildings June 2008

Benefits for the university (cont’d)

• New design criteria for more efficient cooling coils with

ΔT = 16oF to 20oF rather than the usual 10oF.

• In 2007, the university took advantage of the re-commissioning

project to start the continuous operation of the water cooling

system in order to offer year-round service to all users.

• The system’s ongoing operation makes it unnecessary to

install units using aqueduct water or direct expansion to cool

processes or server rooms in winter.

Department of Buildings June 2008

Benefits for the university (cont’d)

• Because of the ongoing operation of the water cooling

system, the university now uses this system to recover heat

that is available in one building and redistribute it to other

buildings where necessary in winter.

Department of Buildings June 2008

Conclusion

•This project is part of the Université de Sherbrooke’s

sustainable development plan since it increases the energy

efficiency of the water cooling system due to better use of

electricity.

•Moreover, the results achieved have exceeded the

Department of Buildings’ expectations.

•The re-commissioning of the water cooling system has

proved to be very effective and profitable for the university.

Department of Buildings June 2008