Project Overview
Funded through ERA’s Natural Gas Challenge in 2020, Stone Mountain Technologies, Inc. (SMTI) conducted a rigorous field trial of pre-production prototypes of their thermally driven heat pump (TDHP), a gas absorption heat pump with all-natural ammonia water refrigerant. The project successfully proved the technology in the intense cold of Edmonton winter, evaluated performance, and measured system efficiency across seasons.
Reducing Emissions in Residential Heating with Advanced Heat Pump
TDHP are emerging as a promising technology to enhance heating and cooling efficiency while reducing greenhouse gas (GHG) emissions. They operate using a thermodynamic cycle that moves heat rather than generating it through combustion. A gas burner drives this cycle and can be fuelled by any typical thermal fuel (natural gas, propane, etc.) or any renewably produced fuel such as renewable gas, hydrogen, synthetic natural gas, or biofuels. Given this, the technology enables direct emission savings by replacing natural gas consumption with renewable fuels while still providing the same amount of heat as current technologies. Alongside the TDHP, each unit is paired with a Napoleon hydronic air handler that uses hot water from a boiler or water heater to warm air, which is then distributed through the home’s heating system. Additionally, the TDHP use a natural ammonia-water absorption process, where ammonia acts as the refrigerant and water as the absorbent. The natural refrigerants have a global warming potential (GWP) of zero, unlike traditional electric heat pumps, which use synthetic refrigerants with high GWP. Beyond environmental impacts, TDHP technology can offer savings for Albertan homeowners because, compared to the alternatives of gas furnaces and boilers, and electric heat pumps, SMTI’s technology has a lower cost per unit of heating capacity.
Validating the Technology and Improving Installations Through Real-World Experience
By completion in 2025, the project confirmed TDHP’s viability with five residential field installations, comprehensive measurement and verification, and documented high-efficiency performance in cold climates. During the project, meaningful product design improvements prior to launch and expansion from an 11,000 to a 160,000 square foot production facility enabled full commercialization of the TDHP system in both Canadian and U.S. markets. The TDHP achieved efficiencies at or above the 140 per cent target and, in some cases, reached approximately 150 per cent, while demonstrating reliable operation in Edmonton’s extreme winter conditions. Additionally, the field and laboratory testing confirmed meaningful reductions in gas use and carbon emissions (up to 15 per cent at certain sites) and validated homeowner comfort and domestic hot water availability.
While the core heating technology worked well, the most important lessons came from installing and operating the systems in real homes. For example, the length and layout of the hydronic piping between components affected performance and electricity use more than expected. This highlighted the need for careful planning before installation. Managing water drainage in extremely cold weather was another key lesson. In some cases, drainage lines froze when not adequately insulated, which temporarily affected operation. These experiences led to improved installation instructions and design updates to make the system more reliable in very cold climates. Additionally, real-world use uncovered durability improvements that were not fully visible in lab testing. Some mechanical parts required redesign to improve long-term reliability and reduce noise. Addressing these issues before full commercialization strengthened the final product and reduced the likelihood of future service problems.
What’s next?
The technology advanced to full commercialization, allowing SMTI to launch their TDHP technology in the North American market, sell approximately 100 units, and install the product in Toronto, Halifax, Montreal, Saskatoon, Regina, Edmonton, Vancouver, and Kelowna with Fortis BC, Sask Energy, ATCO, Enbridge, Energir, and Eastward Energy. To expand further, SMTI plans to address the market for cold climate electric heat pumps and is working on developing a product with both heating and cooling.