Standing Column Wells for Clé-des-Champs School

The Centre de Services

Scolaire des Mille-Îles (CSSMI) mandated gbi to replace the heating, ventilation and air-conditioning (HVAC) system at its Clé-desChamps primary school, which involved refitting its mechanical room. Through collaboration with the client, it was decided to install a geothermal heat exchanger with permanent column wells—a first for an institutional building in Québec— to make a major shift in energy consumption, reduce pressure on the local electricity generation and distribution network and combat greenhouse gas (GHG) emissions.

The concept is to heat and cool an indoor environment efficiently by directly using groundwater, which exchanges heat through conduction and advection with the hydrogeological environment. The technology can rely on a process called the ‘bleed,’ whereby undisturbed groundwater infiltrates a pumping well through a network of fractures in the rock.

A new concept

This technology has been the subject of research at Polytechnique Montreal, which worked with gbi to test its theoretical model and then demonstrate its viability.

The main advantage of perma- nent column wells is a significant reduction in the total number of wells that need to be constructed in the field, compared to a closed-loop well system.

With the use of closed-loop geothermal energy, 22 wells of 150 m in depth would have needed to be drilled at the school. With the permanent column wells, on the other hand, only five pumping wells of 135 m in depth and one injection well were required, reducing the project cost by 40%.

Standing column wells are feasible in small spaces where geothermal energy was not previously con- sidered an option, including the sites for many existing buildings that will need to be decarbonized in the years to come. Also, water resides longer in them and allows users to reduce their electrical power demand during severely cold winters.

Exploration with a deadline

The project began as soon as classes ended. The schoolyard had to be available to students, with its new wells, two months later.

Most of the work was condensed into short two-phase periods. Existing mechanical spaces were tight, so the team had to work creatively to optimize the available volume.

The project also stood out for its complexity at the level of the exploratory phase, since a lot of new information was needed to design the geothermal heat exchanger. In addition to a thermal response test, a pumping test and groundwater sampling were required.

The gbi team worked closely with Polytechnique to deploy an automatic control system capable of measuring and recording essential data for academic research activities. The use of groundwater raised several issues, such as the management of suspended solids, the risk of clog ging and the durability of the facilities. The team responded to these challenges, among others, with the addition of a filtration system, a plate heat exchanger redundancy system to maintain continuous operation during maintenance and stainless steel components.

Just the beginning

Fewer wells mean less drilling time, which can reduce the initial investment cost compared to traditional geothermal energy. The reduced duration of work on-site allows teams to compress the schedule and to increase the number of projects achievable, which is important given drilling contractors are in high demand.

The team from gbi continues to work with the Polytechnique research chair. This collaboration not only makes it possible to advance knowledge, but it also helps inspire confidence in customers, who see the benefits of the technology through the success of the project at Clé-des-Champs School. Indeed, many have responded to the call to test permanent column w ells in their own projects.

This innovation also makes it possible to extend the life of equipment and systems. With the geothermal heat pump’s stable operating conditions, due to the thermal inertia of the ground at great depth, its lifespan is estimated at 25 years compared to, for example, 15 years for aerothermal. This makes it possible to act on the problem of managing end-of-life refrigerants, which too often ha ve a high global warming potential (GWP).

Standing Column Wells for Clé-des-Champs School, Mirabel, Que.

Award-winning firm (mechanical and electrical engineering): gbi, Montreal, Que. (Olivier Paquette-StJean, ing.; Jean-Michel St-Georges, ing.; Jasmin Faucher, CPI; Maxime Boisclair, ing.; Guillaume Gigoux-Théorêt, ing., M. Ing.; Eric Lemieux, Tech.).

Owner: Centre de Services Scolaire des Mille-Îles (CSSMI).

Other key players: Polytechnique Montréal (concept development), Lachance et associés architects (architecture), Construction Genfor (general contractor), Groupe Charbonneau (plumbing and heating contractor), Reguvar (automatic control contractor), Les forages LBM (drilling contractor), Multistack (water and heat pump), Franklin Electric (submersible pumps), Armstrong (heat exchanger and pumps), Delta Controls, Belimo, Siemens, Versaprofiles (piping), Bollfilter (filter).