Cimco Refrigeration, a Toronto-based refrigeration contractor, recently partnered with Canadian environmental and engineering consultancy Pinchin to create an ammonia/NH3 (R717)-based “fifth-generation” district heating and cooling system in Canada.
The system, designed by Pinchin, is located in a new development called Blatchford in Edmonton, Alberta. The 1.5km2 (0.6mi2) municipality, built on the site of a former airport, has targets of net-zero emissions and 100% renewable energy.
The first phase of the development, which was completed two years ago, consists of 1,000 homes, each of which has a domestic water-to-air heat pump that provides cooling, heating and hot water. Each heat pump is connected to a centralized thermal plant in the middle of the community, which is powered by an ammonia chiller produced by Cimco.
The elaborate district cooling and heating system was outlined by Benoit Rodier, Director of Business Development at Cimco, during the HVAC and Heat Pumps session at the ATMOsphere (ATMO) America Summit 2022 on natural refrigerants. The conference, which took place June 7–8 in Alexandria, Virginia, was organized by ATMOsphere, publisher of Ammonia21.com.
The ammonia chiller works in two directions – supplying glycol to a geothermal field, and supplying water to the Blatchford homes. The geothermal field is a stormwater lake with 570 boreholes that go 150m (500ft) deep. The water delivery system uses two pipes (for delivery and return), buried 10 ft deep in the ground.
Operating as a chiller in the summer, the ammonia system becomes a heat pump in the winter, reversing the roles of the evaporator and condenser. Similarly the heat pump at the homes, serves as an air conditioner in the summer, and a space heater in the winter.
As detailed by Rodier, in the summer, the ammonia chiller’s evaporator produces 10°C (55°F) water that is piped to the homes; there, the water removes heat from the home unit’s condenser as the home unit produces cool air at its evaporator. At the same time, the ammonia system’s condenser is rejecting heat through the glycol loop that delivers the heat to the geothermal field.
The process reverses in the winter. The ammonia system’s condenser heat delivers 25°C (77°) water to the homes, where it is cooled by the home unit’s evaporator, while the home unit’s condenser is releasing hot air to the home. At the same time, the ammonia system’s evaporator is cooling glycol, which is delivered to the geothermal field where it absorbs heat.
Low charge ammonia system
The 1MW (284.3TR) ammonia chiller consists of one compressor, plate-and-frame heat exchangers and a very low charge of ammonia – roughly 0.6lbs/TR (0.08kg/kW).
What is rare about this system is that an installation of this nature would normally use an HFO- or HFC-based commercial chiller, said Rodier. From a natural refrigerant perspective, the chiller could also have been designed to use CO2 (R744) or, if a larger charge was permitted, propane (R290).
In terms of emissions reductions, this district heating/heat pump arrangement reduces each household’s emissions by 1.5 metric tons of CO2e annually compared to gas heating, said Rodier. He pointed out that the savings potential would be much greater on a larger scale. Emissions reductions also depends on where the system is located and the make-up of the area’s energy supply.
Opting for ammonia as the chiller’s refrigerant over a synthetic alternative brings the total emissions reduction of the system to 8.8 metric tons of CO2e per year, he said.
Cimco is currently involved in a similar project in downtown Toronto, which will use Lake Ontario as the heat source for high-temperature district heating with a two-stage ammonia system. The network will be more complex than the system in Blatchford as this one will serve a mix of homes, offices and retail spaces.
Home NatRef heat pumps needed
According to Rodier, one disappointing aspect of the project was that the domestic heat pumps did not use natural refrigerants. He put this down to the lower demand for the technology in North America compared to other regions like Asia and Europe. Low gas prices have also limited the growth of heat pump technologies in North America, but this is likely to change as prices rise.
Rodier encouraged the introduction of home heat pumps using natural refrigerants like CO2 or R290 in North America for space heating. (Hot water home heat pumps using CO2 are already sold in North America.)
Likewise, for countries, regions and cities with emissions targets, natural-refrigerant-based district heating will also be key to their decarbonization plans, said Rodier.
Heat pumps are the technology that makes this all happen, noted Rodier. “If you put one kW of electricity into a compressor, you get 4-6kW of heat from the condenser,” he said. “This is one of the very rare things – maybe the only thing – on this planet that actually gives you more than you are paying for. So it is the right tool to reduce carbon footprint and fossil fuels.”
“[Refrigeration] is one of the very rare things – maybe the only thing – on this planet that actually gives you more than you are paying for. So it is the right tool to reduce carbon footprint and fossil fuels.”Benoit Rodier, Cimco Refrigeration
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