What if you could heat your home or hot water with natural gas, but at more than 100% efficiency? With advances in Gas Absorption Heat Pumps technology, this is becoming a more viable residential and commercial option.
Gas Fired Heat Pumps Technology
There are two types of gas fired heat pumps that are commonly available for residential and commercial use: gas-engine heat pumps (GEHPs) and gas-absorption heat pumps (GAHPs).
GEHP use a natural gas-fired engine to power a compressor to drive the refrigeration cycle typically seen with air source heat pumps (ASHP).
GAHPs uses the heat produced during the combustion of natural gas to power an ammonia-water based absorption cycle.
While both use natural gas at some point in the heat pump cycle, the main difference is the refrigerant used. A GEHP will typically use R-134a or R-410a like a traditional ASHP versus the the GAHP which uses ammonia as the refrigerant.
Refrigerants and Global Warming Potential
A benefit of GAHP technology using an ammonia based refrigerant is the significantly lower global warming potential (GWP). GWP is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide (CO2). The GWP is 1 for CO2.
Recalling that traditional heat pump technology (ie: ASHP and GEHP) use R-134a and R-410a, we can see the prevalence of this benefit. R-134a and R-410a have GWPs of 1,430 and 2,088 respectively. Ammonia has a GWP of 0. Additionally, the quantity of ammonia used in a GAHP is low, minimizing the adverse health and safety impact in the event of a leak.
Canadian Residential Energy Use and GHG Emission
According to Natural Resources Canada (NRCan), Natural Gas accounted for 43.7% of the secondary energy use for the residential sector in Canada in 2017. Heating Oil (which is still predominantly used in Prince Edward Island and Nova Scotia) accounted for 3.7% of energy use.
This large natural gas use represents an opportunity to further improve the efficiency of natural gas appliances and to reduce provincial carbon footprints in areas where electrification via traditional heat pumps is not a viable option.
Commercial Competitiveness
Beyond the positive environmental impact compared to traditional natural gas technology, squeezing more efficiency from a natural gas appliance makes commercial sense.
The California based Emerging Technologies Coordinating Council (ETCC) found that in restaurant heating applications where a GAHP was used for domestic hot water heating could yield a simple payback period of 1.4-2.6 years depending on the size and application.
Organizations such as FortisBC are piloting Gas Absorption Heat Pump Technology to determine it's practical applications in BC.
Conclusion
GAHPs could prove to be an attractive solution in jurisdictions that rely on more carbon intensive fuel sources for electrical generation and/or heating but electrification is not an economic or environmentally friendly option.
GAHPs could also prove to be a good business investment in industries such as restaurants and food services where profit margins can be razor thin (on top of being devastated by the COVID-19 pandemic).
Sources:
Emerging Technologies Coordinating Council. (2018). Gas-fueled absorption heat pump commercial water-heaters on the way to commercialization. Retrieved from https://www.etcc-ca.com/sites/default/files/summit2018fall/water_-_scott_reed_-_final.pdf
Natural Resources Canada. (2020). Comprehensive energy use database. Retrieved from https://oee.nrcan.gc.ca/corporate/statistics/neud/dpa/menus/trends/comprehensive_tables/list.cfm
Wikipedia. (2020). Global warming potential. Retrieved from https://en.wikipedia.org/wiki/Global_warming_potential
