Toronto and Region Conservation Authority feasibility study and hydrogeological assessment of closed loop, open loop and ATES geoexchange systems

The Toronto and Region Conservation Authority (TRCA) will complete a study to investigate the feasibility of an open loop or aquifer thermal energy storage (ATES) geoexchange system at its proposed new head office. Geoexchange is a non-consumptive technology that uses stable temperatures found below ground to heat and cool a building. The new TRCA facility is currently designed for zero carbon certification and features a closed loop geoexchange system. However, when test drilling began, a deep bedrock valley with several shallow aquifers was discovered. This presents an opportunity to adopt an even more efficient open loop or ATES system.

In line with its mandate to safeguard natural resources across its jurisdiction, the TRCA works alongside its member municipalities to help develop and implement municipal climate change mitigation plans, including the TransformTO Climate Action Strategy (2017) and the Region of Peel Climate Change Master Plan (2019). Funding contributions have been confirmed from both municipalities, and each has expressed interest in the potential for open loop and ATES systems to help achieve their greenhouse (GHG) emissions reductions targets.

In addition to being more energy efficient, open loop and ATES systems have been shown to be 25–50% less expensive in more mature markets like Europe. If implemented in the new TRCA office, an open loop system would be 10–15% more energy efficient and would reduce GHG emissions by 15% compared to the closed loop base case. ATES—essentially an open loop system with seasonal storage of heat and cooling—would be 15–25% more energy efficient and would reduce GHG emissions by 25%. These GHG reductions would result from emissions savings linked to system installation. From the TRCA’s initial capital cost study, the closed loop option would require 44 boreholes drilled 200 metres deep, whereas the open loop or ATES options would both only require five boreholes drilled 50–120 metres deep. This represents a significant reduction in diesel emissions from drilling rigs.

Using an exploratory drilling program, the study will answer three critical questions:

1. Is there sufficient groundwater available in the aquifers under the site?
2. Is groundwater moving slow enough for inter-seasonal storage of heat and cool?
3. Would groundwater chemistry be impacted by heating or cooling?

If an open loop or ATES system is implemented, the TRCA will use the new facility as an engagement and training tool for government, institutions and the private sector, and to address barriers to widespread adoption of geoexchange technology in Canada. The final study will be shared directly with member municipalities, York University, NRCan, and the Geological Survey of Canada, as well as through the TRCA’s Partners in Project Green and Sustainable Technology Evaluation Program (STEP) networks. Community benefits of this project include filling the knowledge gap around geoexchange systems, transforming the geoexchange market and providing more opportunities for green employment.

Innovative aspect(s):

Open loop and ATES systems are innovative technologies that have not been widely adopted in Canada. In evaluating three geoexchange systems, this study may showcase open loop or ATES systems as more beneficial than closed loop systems, which could spur a new best practice for geoexchange evaluation and adoption.

Replicability:

The City of Toronto, the Region of Peel and York University will use the results of this initiative to inform building retrofit decisions and, potentially, to help achieve their GHG emissions reductions targets. If an open loop or ATES system is implemented, this study and ensuing project could be replicated in municipalities across Canada where suitable groundwater conditions are present.