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 m 2 Energy bill exceeding $5.5 million A thermal power station with 3 boilers, 3 chillers and the 2 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 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 7 o F 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 3 rd 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 = 2 o F to T = 16 o F 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 Summer Area (m 2 ) Flow (GPM) ΔT (o F) Peak capacity of station (T) Chillers in operation kW/T , , ,

Project costs and grants Department of Buildings June 2008 PhaseCostGrant kW/h saved Savings PP* (years) 1 to 3$475,000$190,5001,269,000$63, $313,000$99,315930,000$46, $330,000$97,965600,000$30, * 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 = 16 o F to 20 o F rather than the usual 10 o F. 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