Investigation into Open Loop Geothermal Potential at Toronto and Region Conservation Authority's Headquarters

Kristina Anderson

Dans les comptes rendus d’articles de la conférence: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNC

ABSTRACT: Aquifer Thermal Energy Systems (ATES) are significantly cheaper than traditional borehole-based, closed loop geo-exchange systems. However, ATES are highly dependent on the availability of a suitable aquifer, and the data gathering, and analysis of the underground conditions can be costly and time consuming. Specifically, open loop geothermal system require one or more costly boreholes to be drilled very early in the design stage to test for the presence and productivity of an aquifer. These costs - at this early stage - have been historically seen as a barrier to entry that many proponents are unwilling to bear, defaulting to either closed loop geothermal, air-source heat pumps or fossil fuels. NRCan's Geological Survey of Canada (GSC), York University and Toronto & Region Conservation Authority (TRCA) developed a proposal with three main activities: (1) applying high-resolution seismic mapping techniques pioneered by GS to non-invasively characterize aquifers in sufficient detail to support investment decisions in geo-exchange systems, at a potential cost lower than drilling test wells and boreholes; (2) evaluating the incorporation of inter-seasonal thermal storage to the Keele campus' existing district heating and cooling system and the conversion of much of the heating and cooling loads from natural gas to electricity; (3) including a preliminary analysis of ATES implementation potential across the GTA to be disseminated to relevant stakeholders. The seismic survey included the neighbouring TRCA property, which conducted conventional aquifer borehole drilling earlier in the year independent of this proposed project. The proposed ATES or open-loop geothermal system will heat and cool its new corporate head office, located at 5 Shoreham Drive, Downsview, Ontario. As part of the process to obtain Leadership in Energy and Environmental Design (LEED) Platinum certification of this new structure, the energy system is proposed to provide high efficiency heating and cooling. A preliminary borehole was drilled using the mud-rotary technique in January 2019 by Geosource Energy Inc. This borehole was terminated at a depth of confirmed overburden thickness of 119 m (390 ft), much deeper than suggested by the existing mapping of the regional bedrock surface elevations in the area. Three potential aquifer complexes were identified: Oak Ridges Aquifer Complex, Thorncliffe Aquifer Complex, and Scarborough Aquifer Complex. A second borehole was drilled using a PQ wireline core system in August 2020 to characterize the aquifer complexes. A suitable medium to install a borehole was not encountered until 108 m (355 ft) bgl and bedrock had still not been encountered when drilling was halted at 125 m (410 ft) bgl. The data from the two boreholes suggest that a hereto unknown bedrock valley is present in this location.

Please include this code when submitting a data update: GEO2021_189

Retrouver cet article:
Les membres de la Société canadienne de géotechnique peuvent accéder à cet article, ainsi qu'à tous les autres articles de la Conférence Géotechnique Canadienne, dans le Espace membre. Les comptes rendus d'articles sont également disponibles dans de nombreuses bibliothèques.

Citer cet article: