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Speaking on the first day of the Heat Pump Summit, Dr. Andy Pearson presented two case studies whereby large scale ammonia heat pumps have operated efficiently in district heating and a food factory. The presentation raised several questions from the audience interested to learn about the natural refrigerant’s rediscovery for heating.

150 years after the first discovery of ammonia as a refrigerant in cooling processes, the highly efficient substance might make its strong reentry in the heating industry. Despite the general belief that ammonia would be limited to large refrigeration processes, R717 would be similarly efficient in large-scale heat pumps. This was confirmed by Dr. Andy Pearson from UK manufacturer Star Refrigeration in a dedicated speech about the benefits of NH3 as a most viable replacement for HCFCs and HFCs in district heating and industrial production processes.

Pearson hence started his presentation with an overview of “fashionable” and “business” reasons for not having chosen ammonia before and for choosing it now. For the latter, the well-known and well-researched substance has been used over the past 150 years and today no policy maker “would have the idea to ever phase out ammonia”, as it is currently happening to generations of fluorinated gases. On the contrary, ammonia would be a “future-proof” refrigerant able to comply with all legislation when safely handled and efficiently used. If all disadvantages and advantages over a year were combined, R717 would still save about 10% of energy at lower running costs than HFC134a, Pearson confirmed.

Ammonia here to stay

Compressors that could handle the pressure requirements of ammonia, in the past often not available in the right size or only at higher costs, are now offered. Moreover, these high-pressure compressors with balanced radial and axial forces would ensure a high durability needed for large-scale heating systems. The limits of using R717 could range as widely as from process heating at + 90°C to process cooling at -40°C.

Pearson concluded that ammonia in heat pumps would not constitute a new technology as all components would be available as standard solutions on the markets today. Being a proven technology at favourable costs and being also suitable for both new and refurbished buildings, the only remaining barrier would be the acknowledgement of R717 by the heat pump industry. Answering to a question from the audience about the reaction of customers confronted with the fact to have ammonia in a heating plant, he referred to existing safety guidelines covering all necessary precautions in handling ammonia. Accidents involving leaking R717 plants would always be the result of not following these simple safety standards. As a result, ammonia would be perfectly safe to use, such as any other refrigerant would be when basic design, installation and servicing rules would be followed.

R717 in district heating and chocolate making

Pearson presented two case studies about the company’s experience with a 90°C R717- heat pump for district heating systems and factory process applications. The application of an ammonia heat pump incorporating three 5MW packs for a district heating delivered a Coefficient of Performance (COP) greater than 3, supplying heating at 90°C and cooling at +8/4°C. The heat pump encompassed similar capital cost as that of conventional technology.

In a second case study, a NH3 heat pump was installed in a chocolate production plant where the chocolate must not become cold to then interfere with the machinery. According to Pearson the plant in question wasted up to 40% of steam which was used by the ammonia heat pump system much more efficiently, by recovering heat from the vapour otherwise lost to the environment without using the energy saving benefits.