Schematic of system with two-pipe closed loop that can provide both heating and cooling.
System heats the Whistler Athletes’ Village even when the wastewater effluent temperature is low.
The Whistler Athletes’ Village District Energy-Sharing System (DESS) extracts heat from treated sewage effluent and circulates it through a two-pipe, closed-loop system. It is unusual because it extracts low-temperature ambient heat, enabling it to provide both heating and cooling.
The Whistler DESS provides space heating, domestic hot water heating, and cooling for 2,200 users occupying 85,000 square metres of space. The system is one of the first closed-looped, heating and cooling district energy systems in the world, and should reduce greenhouse gas emissions by 96% over conventional heating technologies.
Prime consultants Kerr Wood Leidal Associates, in partnership with DEC Design Mechanical Consultants, were asked initially to analyze potential heat recovery from four sources: treated wastewater effluent, methane gas from a nearby landfill, groundwater, and geo-exchange. Ultimately, the team determined that treated wastewater effluent was the most reliable and cost-effective option. The analysis revealed that wastewater effluent is a high-capac-ity, reliable, and long-term energy source that can provide 97% of the Village’s annual heat energy requirements.
Installed last year, the system uses submersible pumps located in a chamber just downstream of the wastewater plant to pump the treated effluent into the DESS mechanical room, where heat is transferred by heat exchangers into a closed-loop energy distribution system. The clean water is then pumped through a high density polyethylene pipe system to the Athletes’ Village. Heat pumps within the village buildings transfer the low intensity energy from the DESS to higher intensity energy for heating and cooling purposes.
Designing the Whistler system was extremely complicated because of the degree of variability in the energy source and variable demands. Further complicating matters was the need for the system to perform in a cold climate.
The size of the distribution network’s piping creates thermal storage, which can be conditioned to reduce the system’s peak loads. When combined with the system’s ability to add other renewable energy sources, the storage capacity further reduces the system’s reliance on back-up gas-fired boilers.
The system can function in either a heating or cooling mode, or both at the same time. It was necessary to ensure that freezing would not occur under extreme weather conditions, but for both financial and environmental protection reasons, the potential use of anti-freeze was successfully avoided. The system has a design life of at least 50 years, requires little maintenance, and is inexpensive to operate.
It is projected that the system will produce up to 11,000 megawatt hours of building heating energy per year, using energy that would otherwise be wasted.
Project: Whistler Athletes’ Village Low-Temperature District Energy-Sharing System, B.C.
Award-winning firms: Kerr Wood Leidal Associates (Neil McDonald, P. Eng.), DEC Design Mechanical Consultants (William Vaughan, P. Eng., Tom Ren, P. Eng.)
Owner: Whistler 2020 Development Corporation
Other key players: Empac Engineering, Pro-Site Management, Graham Construction & Engineering, Whistler Excavations
Supplier: Camus Hydronics (boilers)