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One of the major components of the OAA HQ’s Renew + Refresh project is the ground-source heat exchange system, which is also commonly known as geothermal. The system has undergone improvements as it moves ahead, through concept to testing to implementation.
What is Ground-Source Exchange?
A ground-source heat exchange system utilizes energy extracted from the Earth. This energy maintains a constant temperature year-round, allowing for a dependable distribution of heating and cooling irrespective of the climate. This provides a warmer starting point in the winter and a cooler starting point in the summer.
The OAA HQ will rely on a closed-loop system, using a grid of pipe to pump heat-transfer fluid through a vertical circuit of underground piping. The benefits of this kind of system are both environmental and financial:
While traditional electric baseboard heaters certainly provide heat, heat pumps produce a greater amount of heat for each unit of power. Ground-source heat pumps are the most efficient (over air-source heat pumps) because the ground is a steady temperature all year long, which provides a warmer starting point in the winter, or a cooler starting point in the summer, than the air around us.
The OAA HQ will have a double circular field of 15 wells that are more than 180 m (600 ft) deep. Because Toronto’s climate means buildings require more heating than cooling, the field will be balanced using warm water from hydro-solar panels on the roof. The water is circulated around the building using SA Armstrong pumps.
Thermal Conductivity Test
Geosource Energy Inc., based in Caledonia, Ont., has created the system currently being installed. A test borehole was drilled in October 2017 to 185 m (600 ft) in order to complete a 48-hour thermal conductivity test.
The thermal conductivity test was held on November 1 to 3, 2017. As the test did not detect artesian conditions, natural gas, trace oil or significant water production during drilling, it verified there would be no major issues during the geothermal field construction. These successful results allowed the design of a closed-loop system to move forward, with a construction depth of 184 m (600 ft)—equivalent to the height of the TD Centre’s North Tower.
TD North Tower 183m (far right in image)
To read the thermal conductivity test, click here.
The 15 bore holes were originally to be laid out in a rectangular grid pattern on the west parking area of the site. Architect David Fujiwara came up with an alternate design based on a circular configuration. In collaboration with WSP, a new oval arrangement of the same number of bore holes was designed and tested. The results were an additional five per cent more efficient that the rectangular grid pattern.
In April, the bore hole drilling began and was completed by mid-May.
Video of Drilling
The OAA will continue to update this introduction to the ground source exchange system, as the construction of the Renew + Refresh project continues.
The OAA’s System
Along with photovoltaic (PV) solar panels, high insulation and improved airtightness, the ground-source exchange assembly is one of four “off-the-shelf” components required to create the full system at 111 Moatfield Drive, which comprises both passive design approaches and commonly available, proven technologies.
For the OAA HQ, two types of solar panels are being installed: 411 m2 (4425 sf) of the standard PV panels by Heliene and 128 m2 (1380 sf) of transparent, experimental panels by Morgan Solar. The transparent panels will be located over the outdoor terrace on the south facade. The total system should produce 100,000 kWh/year (about what 8 -10 average homes would use in a year).
Electrical production from the rooftop solar PV panels will be fed into the grid, while the power needed to operate the building will be drawn from the grid. It is our goal to be ‘electrical power-balanced’ over the course of a year and thus be net-zero energy.
Additional insulation is being installed to all solid exterior walls and underside soffits. At the same time, this will reduce thermal bridging. The R-values of the completed walls will vary between the existing R-10 to up to a new R-30 level where possible.
Unlike many other buildings constructed in the early 1990s, the OAA building was very airtight to begin with. Notwithstanding, some adjustments are being made at vent locations to improve it further.
The full program will require two to three years in order to finalize construction and monitor how the building performs. This information will be made available on the OAA Website and be shared with our members and the building industry as ‘lessons learned’ and demonstrate how best to address the retrofit of Ontario’s existing building stock.