Up to 67% Energy Savings and Improved Occupant Comfort Achieved
Western University in London, Ontario, is widely regarded as one of Canada's premier collegiate institutions with an on-campus population to approximately 40,000 students, faculty, and staff. The main campus comprises 481 hectares [1189 acres] of Gothic-style buildings and a mix of state-of-the-art, LEED-certified structures. With overall utility costs averaging CAD 20 million, Western's facilities team devotes considerable time and resources to improve energy efficiency and sustainability.
Over time, Western University's campus has grown to more than 90 buildings. Two chiller plants located at the north and south ends of the property that serve separate loops manage the extensive campus cooling system. As cooling needs increased over the years, the two plants have expanded to include nine centrifugal chillers that serve a variety of classrooms, residences, eateries, kitchens, art galleries, meeting areas, research laboratories, and exercise facilities. The chilled water supply to each building came from a traditional primary-secondary tertiary pumping system. Each building had at least one decouple bridge (common pipe) between the secondary and tertiary loops, with a bridge valve controlled to achieve a return water setpoint of 13°C [55°F]. As the infrastructure grew, the cooling system's imbalance increased significantly, leading to inefficient plant performance, high pumping cost, and occupant discomfort in different locations. Buildings close to the plants were receiving too much chilled water flow, while those further along the loops were not receiving enough. Over time, pumps were added to help increase pressure at the plant whenever a building was not receiving enough flow. These additional pumps were unsuccessful.
At the south end, the facilities team added variable frequency drives to boost water pressure to reach the buildings located uphill. However, this exacerbated the problem and caused water balancing issues. "We finally realized we were doing it backward. We had to accept that boosting the pressure at the plant wasn't going to work - we needed to do valve work instead," said Dan Larkin, HVAC Controls System Specialist, Physical Plant and Capital Planning Services at Western University. "Every building had at least one bridge valve pouring water into the building and back out, often bypassing the AHU coils and leading to a huge waste of energy. The plan was to modify the return water piping to eliminate the decouple bridges and valves, so the chilled water has to flow through the AHU coil. In that way, only the chilled water that is needed goes into the buildings and returns to the plants, allowing the chillers to operate more efficiently."
After learning about the Belimo Energy Valve, Larkin knew it was the right solution for retrofitting the chilled water system. Shortly after the install, Western University experienced a reduction in pumping energy. After installing the valves, the initial testing showed significant improvements in Delta T and flow reduction. However, they still had issues cooling all areas on peak demand days. The facilities team began to leverage the Delta T Manager feature to realize additional energy savings further and improve occupant comfort. In one example, the AHU coil Delta T improved to 5.7°C (10.3°F) while the flow decreased from 431 GPM to 142 GPM, with no sacrifice to the room comfort.