The geothermal field and Energy Innovation Centre (EIC) project is part of the ongoing transformation of Durham College’s (DC) energy infrastructure to support and implement sustainably focused initiatives on campus.

Located underground at the Oshawa campus, DC’s geothermal field harnesses 550 tons (1.9 megawatts) clean, sustainable geothermal power, which is then processed through the EIC and sent to the Gordon Willey building to fuel its energy needs.

The bright, modern EIC also provides an exhibit-like atmosphere where students and visitors can learn more about how the geothermal system works through interactive touch screen monitors, which features system diagrams and performance metrics. Additionally, a real-time energy dashboard provides insight on campus energy savings and the reduction of associated greenhouse gas emissions.

The EIC also acts as a living lab, allowing faculty from selected programs to incorporate geothermal technology into their curriculum and provides students with a unique experiential learning opportunity as they observe how green-energy technologies work.

The geothermal field and EIC were completed in partnership with Siemens Canada, who provided valuable industry knowledge and contributed as the primary contractor for the project.

What is underground thermal energy storage?

Underground thermal energy storage (UTES) is a form of energy storage that provides large-scale seasonal storage of cold and heat in natural underground sites.

While multiple types of thermal energy supplying systems use geothermal energy for cooling and heating, such as the deep lake water cooling systems, UTES is different because it is an active energy storage system.

The underground is suitable for thermal energy storage, because it has high thermal inertia. If undisturbed, below a depth of 10 to 15 meters, the ground temperature is only weakly affected by local climate variations above ground. The large storage capacity of natural underground sites makes UTES a common form of long-term and seasonal storage.

How does Durham College’s underground thermal energy storage system work?

There are currently three common types of UTES: aquifer thermal energy storage, borehole thermal energy storage (BTES) and rock cavern thermal energy storage. DC’s geothermal system is a BTES. It works by storing energy underground for extraction during demand periods.

BTES is a closed-loop system that stores thermal energy in the bedrock underground. Borehole heat exchangers (BHEs) are installed to penetrate into the storage medium and the thermal energy carrier circulating through the BHEs is thermally coupled to the bedrock. The liquid, carrying thermal energy from sources including the ambient air, solar energy and process waste heat, can either store or discharge thermal energy into or out of the bedrock.

BTES is suitable for both small and large-scale energy applications, depending on the number of installed BHEs. Large-scale BTES like DC’s geothermal project, are more applicable toward providing seasonal thermal energy storage and are used to supply cooling and heating to large buildings.

What is a geothermal field?

A geothermal field is comprised of a section of land that features one or more boreholes, which are U-types of high-density polyethylene pipes installed in the crust of the earth for the purpose of picking up the stored heat.

A circuit of boreholes is a connection of a number of boreholes from the field. Each geothermal field typically has several circuits, each one of them with a determined number of boreholes interconnected.

DC’s geothermal field consists of 150 boreholes.

What is the role of the heat pump?

In a geothermal energy system, the heat pump serves two purposes: one is to extract heat and the other is to use the earth as a heat sink to absorb excess or unwanted heat. This is why in winter, when the outside air temperature is colder than the temperature of the earth, the heat pump extracts heat from the earth to warm a building. In summer, the operation is reversed and the heat pump drives the excess heat from the outside air temperature into the heat sink, i.e. the earth.

How does the BTES system provide heating and cooling?

The system circulates a glycol solution, which is encased in polyurethane tubing, through the underground network of boreholes to the heat pump.

The heat pump then uses compressors and refrigerant to deliver heating and cooling water/glycol to heat exchangers and air cooling units located in buildings across campus.