You may have heard the hype recently (ok, probably from TAF) about electric heat pumps. They’re a relatively simple technology, low-carbon, and highly efficient – is there anything they can’t do? But not all heat pumps are electric. Back in 2016, TAF installed two gas heat pumps in a large residential complex, one of the first large-scale field pilots in a cold climate. Our new report charts their progress and reveals some exciting results and lessons.
Why not all electric? In fact, while electric heat pumps in Ontario are certainly lower carbon and most efficient, gas absorption heat pumps (GAHPs) enable buildings to consume natural gas more efficiently, and are a key priority for reducing carbon emissions. For building owners who don’t want to switch from gas to electric-heating, GAHPs offer an affordable and efficient alternative.
We installed two such heat pumps in a Toronto social housing building built in 1972, containing about 400 residential units. Our goals were to monitor the system and determine whether actual performance would measure up to expected performance, and whether this technology would be appropriate for future projects in cold climates across North America.
Field monitoring over last winter revealed that the heat pumps achieved 114% efficiency. During extreme cold weather (down to -13°C) the heat pumps continued to save natural gas and emissions compared to a modern condensing boiler. Over the past summer, as the exterior temperatures warmed up, performance increased to a maximum of 125% efficiency, in line with manufacturer performance curves.
Overall, these units are expected to save nearly 5400 m3 of natural gas and over 10 tonnes of carbon emissions annually compared to a 90% efficient condensing boiler (that’s equivalent to driving a gas combustion automobile around the Earth’s circumference!) Our findings have shown that GAHPs are significantly more efficient than conventional gas-fired heating equipment and can reduce emissions and gas consumption, while avoiding switching to a higher cost fuel. We also found that domestic hot water applications are ideal for this technology due to the relatively low water system temperatures required. This enables the heat pumps to operate at their most efficient levels.
Gas absorption heat pumps result in lower operational costs, but due to the relatively new nature in the North American market, may require higher capital costs for installation until the market matures. This is one of a few key challenges to scale up. Integrating GAHPs with conventional equipment and within existing systems adds complexity – this means more time spent during the design and optimization stages to ensure the systems are working as intended. As with most other non-typical mechanical systems, experienced engineers and contractors are integral to success.
The Federal, Provincial and Territorial governments have all identified the development of a market for residential gas absorption heat pumps as a 2030 goal in both space heating and water heating. With efficiencies exceeding 100%, they will be an important piece of achieving this goal; if fuelled with renewable natural gas, this technology could also provide a pathway to further decarbonisation of space and water heating equipment.
Click here to read the full report.
