Stantec designed a large geothermal heating and cooling system for Walmart Canada's 135,000-square-foot green prototype supercentre in Burlington, Ontario. The project used other innovative cost-savin...
Stantec designed a large geothermal heating and cooling system for Walmart Canada’s 135,000-square-foot green prototype supercentre in Burlington, Ontario. The project used other innovative cost-saving technologies as well.
The geoexchange system has a horizontal arrangement of pipe beneath the parking lot, drawing heat from the earth in the winter and pumping it back in the summer. As a result, Walmart Burlington’s heating, ventilating and air-conditioning systems (HVAC) will generate energy savings of 57% compared to those in Walmart stores constructed prior to 2008.
The project represents the first known global geo-exchange installation using SpiderPlow technology. Traditionally the SpiderPlow has been used almost exclusively for oil and gas applications.
At the Walmart store, 15 kilometres of pipe was laid using the SpiderPlow in only six days, compared to about three months of installation time for a typical bore-hole system. The SpiderPlow technology had several benefits: it reduced ground disturbance, and it allowed digging at depths of greater than 7 feet, at a consistent depth in undulating terrain. It also allowed the installation of piping in a single pass. The technology reduced the geothermal construction costs by about 70%.
Roll-Out Radiant Mat
Walmart had previously experiment-ed with radiant cooling in one of its Las Vegas stores, but the Burlington store was the first application of both heating and cooling via a radiant slab. Stantec worked with the radiant system manufacturer to develop a “roll-out” radiant mat for the hydronic floor heating and cooling system inside the store.
Because proper humidity control was critical for the Burlington store, Stantec, in conjunction with the dehumidification equipment manufacturer, developed air handlers using heat pump technology specifically for this project. The system includes tempera ture and humidity control, CO2 demand ventilation control, and building pressurization.
Harvesting Heat From Store Refrigerator Cases
Stantec worked with the refrigeration equipment engineer to design a system that harnesses the heat rejected from refrigerator cases and uses it for the hydronic heating system in the store during the cold months. During the warm months, the rejected heat is stored in the geo-exchange field.
The CO2-based refrigeration systems use a non-traditional heat transfer fluid, which is 90% more environmentally friendly than conventional refrigerants. Bio-Green 1,3-Propanediol (25 mixture) has improved environmental and heat transfer proper ties compared to propylene glycol.
Modelling And Controls
Stantec developed a highly accurate computer model for the entire building system (roof, slab, walls, windows, and skylights) to analyze the rate of heat transfer to and from the ground over several years of heating and cooling the building. This extensive energy model using TRNSYS software, a transient thermal analysis software tool, was used to measure the performance of the mechanical system and the geo-exchange field, and to provide a tool to further improve performance.
An extensive control sequence to optimize and integrate all the system components was developed, using a Novar control system.
Compared to a similar building designed according to the Model National Energy Code for Buildings, the Burlington store has achieved a 50% reduction in peak load demand.
Project: Walmart, Burlington, Ont.
Award-winning firm –HVAC engineer: Stantec Consulting (Nuno Duarte, P. Eng., Jim Berenton, P. Eng., David Overton, Steve Hughes)
Owner: Walmart Canada
Other key players: Petroff Architects, Counterpoint Engineering, Ellard-Wilson Engineering, Cobalt Engineering