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Large ammonia heat pumps offer new technological opportunities for retail and trade at significant energy savings. In the latest edition of the ScanRef magazine, eurammon is discussing two case studies confirming the potential of R717 and the ammonia-dimethyl ether blend R723 for non-residential applications.

Heat pumps for large-scale applications in retail and trade offer environmental and economic opportunities currently not exploited by industry, by reverting to energy sources such as waste heat from refrigeration and air-conditioning, discharged process waste air or wastewater with a higher temperature level. While already delivering on environmental promises, heat pumps can further enhance the carbon footprint of heating applications in larger facilities by using natural refrigerants. To demonstrate the ecological and economic benefits ammonia heat pumps can bring to manufacturing facilities and smaller businesses, the European initiative of natural refrigerants advocates – eurammon – has drawn attention to two successful developments in the re-discovery of ammonia for heat pump applications.

R717 heat pumps to save 3,400 t of carbon emissions

One of Europe’s largest ammonia (R717) heat pumps has been installed by Johnson Controls at the Mülligen letter sorting centre, part of the Swiss Post. Handling 4.5 million letters every day, the facility constitutes the largest building in Switzerland, and consequently has impressively high heating and cooling needs. These are covered by taking energy from the wastewater of a nearby sewage plant – an energy source with a potential of 266 million kWh low temperature waste heat per year. Around 50% of the heat energy is taken from the treated wastewater, with another 30% coming from heat rejected by the building air-conditioning system.

The installed R717 heat pumps, having a refrigerating capacity of 4.3 MW and a heating capacity of 5.6 MW at 62°C hot water outlet temperature, use the wastewater to cool the rejected heat from the refrigeration system. The combined heating/refrigerating machine installed in a 70 m² plant room shows increased efficiency especially during summer times when the automated letter sorting systems demand an increased cooling load of 4.9 MW. Three reciprocating compressors are used for first-stage refrigeration at an evaporation temperature of 5°C and a condensation temperature of 30°C. They can also work in pure refrigerating mode, without using waste heat. The ammonia system, installed in 2007, has reduced the use of fossil fuels by 85%, equalling a reduction in carbon emissions of 3,400 tonnes per year.

R723 heat pump with COP of 4.2

Since early 2009, Frigopol has been offering an air/water heat pump for industrial use that works with the natural refrigerant R723 – a blend consisting of ammonia and dimethyl ether. Working at a capacity of 24 kW, the system provides hot water at a temperature of up to 45°C for room heat, and at 65°C for process water. The heat pump’s main component is a semi-open compressor filled with 3.5 kg of R723, and featuring a frequency control to allow variable capacity adjustment between 50 and 100%. An overriding control ensures that the water flow temperature remains on a constant level by changing the speed of the compressor when the need arises. Overall, the heat pump achieves a Coefficient of Performance (COP) of 4.2, using water to cool the electric motor that will then directly flow into the hot water circuit. Being soundproofed and installed outside the building, the R723 heat pump unit is suitable for housing associations and smaller businesses.