District Energy System Project
The Facilities Management department operates and maintains the campus district energy system (DES). Phase 3 of this $14 million project was completed in October 2011 and has been operating 24 hours a day ever since. The DES is a system of pipes and equipment that provides heating and cooling to twelve academic buildings totalling about 90,000m2.
Distributed water source heat pumps within the academic buildings take ambient temperature water and convert it to hot (45C) water and cold (7C) water, which is required to keep the buildings comfortable.
The water is distributed around the campus by pumps located in the geoexchange building. The ambient temperature range (6C to 36C) is maintained by geothermal temperature exchange. Additional heating is provided by a high efficiency condensing boiler and additional cooling is provided by two 400 ton evaporative cooling towers.
Why was the DES created?
UBCO Academic & Admin buildings were known to have differing heating/cooling profiles or usage. In some cases, buildings would reject surplus heat energy while outside temperatures were as low as -2°C. Other buildings would meanwhile experience a heating demand at outside temperatures of +15°C. DES allows our buildings to utilize this rejected energy.
UBC has set aggressive GHG reduction targets, to exceed Kyoto Protocol requirements. Recapture of waste heat was therefore desired to further reduce harmful GHG emissions from natural gas fired building heating systems. Buildings that reject energy can feed the surplus energy to other facilities that require it, as long as all facilities are grouped together in an Energy Sharing Closed Energy Loop format.
3 advantages of a closed loop system are:
- Enables reduction of the existing open loop geothermal aquifer peak and monthly demand
- Allows for the centralization of heat exchanger maintenance, required to reduce ongoing cost, complexity and to increase system reliability
- Supports adaptation to future environmentally friendly technologies using low temperature energy sources.
System Operation
The DES pumps water at ambient temperature (8.9C to 23.9C) around the campus to 11 academic buildings. This is what we call the DES energy loop. Each building has its own energy loop supply to heat pumps which produce hot and cold water to heat or cool the building.
Often a building is balanced, meaning that its energy loop water supply is operating within the temperature parameters that allow the heat pumps to produce hot or cold water. In the winter a building may require more heating than cooling. In this case it will open a two way valve and take heat energy from the main DES energy loop.
If the DES loop is operating within its temperature limits the loop is balanced.
If more of the buildings are calling for heating than those requiring cooling, then the temperature of the DES energy loop will go down. If it goes down below the minimum temperature limit then we have to add heat to the loop. This can be done by diverting the DES water through one of the heat exchangers located in the geoexchange building.
On the other side of the heat exchanger is the geothermal water. This water is a constant temperature of between 10C and 12C all year round. The difference in temperature of the return water from the DES (maybe 5C), and the geothermal water, allows us to extract heat from the geothermal water.
Diverting the DES water through a high efficiency condensing boiler to raise the temperature creates an additional source of heat.
If more of the buildings are calling for cooling than heating, then we need to cool the DES loop water. Again, the first stage of cooling is to use the geothermal water via the heat exchangers. The second stage is to divert the DES water through two 400 ton evaporative fluid coolers.
Proof Not Promises Award
As part of an ongoing partnership between UBC Okanagan and GE Water & Process Technologies, a Proof Not Promises Award was presented to the Geothermal Facility as recognition of a joint project that realized a reduction of corrosion rate in the District Energy geothermal loop by 92%. This has greatly improved the life expectancy of the piping and heat exchanger surfaces, resulting in a much healthier system.
As part of a continuous corrosion monitoring, GE Water tested the DES geothermal loop for Sulfate Reducing Bacteria (SRB’s). SRB’s were found to be present in the loop and contributing to possible fouled heat exchange surfaces as well as localized corrosion. The solution was to add a non-oxidizing biocide to the closed loop at regular intervals to impede SRB growth. After implementation, mild steel corrosion had dropped by 92% indicating a much healthier and long lasting system. The reduction of corrosion and growth within the heat transfer surfaces has resulted in increased heating and cooling capacity of the district energy system. This has deferred capital expenditure in cooling tower infrastructure.g.
Project History
2004: Clean water is required for a trout research project. A 750’ deep well was drilled but was found to be dry. A local hydro geologist suggested drilling to the east of campus where there is a known aquifer. Test wells produce excellent results, up to 1200 US gallons/minute.
2005: Water supply utility now upgraded. Trout Program abandons well water supply idea although an open district energy loop concept is created.
2006–2008: Design and construction of open loop district energy system.
2008-2011: Open Loop operates (Phase 1) with the newer buildings as they are constructed, however reliability of supply issues delays the addition of the 5 original buildings (Phase 2).
2010: UBCO directs consultants to resolve issues, provide additional system capacity. Design and construction of a closed loop “energy share” system begins.
2010–2011: Design/construction of hybrid “Energy Share” campus system.
2011: Open Loop system converted to Closed Loop DES (Phase 3) with an open loop geothermal heat exchange system. Operation of District Energy System is live.
2012: Original 5 buildings connected to the system (Phase 2).
Today: Ongoing optimization of newer buildings to operate efficiently with the closed loop temperature operating parameters. Operation and maintenance of the system is ongoing.
Student, Faculty and Staff Engagement
Facilities Management welcomes discussion on this system, and opportunities exist to learn from this project. Please contact our team if you or your department wish to know more.