The I.K. Barber Learning Centre is the main library on campus. It was built in 2007 and has a gross floor area of 27,000m². The building was a significant user of thermal energy from the District Energy System (DES) due to its size.
During investigation of the building, it was discovered that the heat pipe system in the main Air handling units (AHUs) were both non-functional. A heat pipe system is a series of multiple hollow tubes filled with refrigerant, arrayed in a coil held together by heat transfer fins. When the assembly is tilted toward the warm air stream (building exhaust), the warm air causes the liquid refrigerant in the heat pipes to evaporate. The refrigerant gas then rises up the pipe to the cold side (outdoor air intake), where it condenses and transfers the heat via condensation.
The process is incredibly simple, only relying on the coil to be tilted appropriately. However, it was discovered that the tilting mechanisms for all three primary AHUs for the building were not functioning as intended, either because of bent linkages or broken actuators. Out team undertook a project to replace the broken actuators and fix the linkages, as well as adding various sensors.
Additionally, a demand based heating water supply temperature (HWST) reset strategy was implemented, where the heating valve positions for the building’s fan coils and AHUs were monitored every 5 minutes. When more than one valve is open 95%, and the associated room temperature is less than 21°C, the primary HWST set point is incremented up by 1°C. The building’s HWST currently typically operates at temperatures 20-30°C below what it used to when using an outdoor air temperature reset strategy.
The result of the above measures is that the building’s thermal energy demand has been reduced by ~22%, saving ~$11,000 per year in thermal energy cost and reducing emissions by ~40 tCO2e per year.