Ohrid 2019: dernières tendances technologiques concernant l’ammoniac et le CO2 (en anglais)

Présentation de plusieurs études de cas d’installations frigorifiques à l’ammoniac et au CO2 sur la base des communications de la récente conférence IIF d’Ohrid.

During the 8th IIR Conference on “Ammonia and CO2 Refrigeration” in Ohrid, North Macedonia, on April 11-13, 2019, 51 papers were presented, including 21 on ammonia, 22 on CO2 and 8 on ammonia or CO2 + another refrigerant.

Ammonia trends

Eight of the papers dealing with ammonia focused on low-charge systems, which represent the leading disruption in the traditional industrial refrigeration market according to K. Zolcer Skacanova et al1. The proliferation of low-charge ammonia systems is evident in Australia and in North America where they are considered as a very attractive option for the replacement of R22 systems. In China, the development of NH3/CO2 secondary and cascade refrigeration systems, that reduce ammonia refrigerant charge, has been gaining popularity since 2013. The initial results of an on-going Shecco research1 indicate that cost is identified by many experts in the field as the biggest barrier to wider adoption of low-charge technology.

Overall, today more than 90% of large industrial refrigeration facilities in Europe use ammonia as the refrigerant1. Besides food processing, cold storage and distribution, ammonia has found its place in breweries, wineries, ice rinks, chemical plants, cargo ships and fishing vessels as well as district heating and cooling and large-scale air conditioning for office buildings, universities and airports. Concerning food processing, valuable papers presented in Ohrid dealt with a revamped ammonia milk chilling plant in India2 and a new two-step mackerel filets freezing processing line in Norway3. The use of ammonia in breweries was illustrated by a modern installation in Norway comprising an efficient ammonia heat pump – instead of a boiler in traditional breweries – to produce the steam needed for different phases of the process4. Regarding ice rinks, the case of a Slovakian ice hockey stadium, where all cooling and heating needs are provided by an indirect ammonia heat pump with only 120 kg of refrigerant, was presented5. Concerning district heating, a thermodynamic model of a 5 MW test and demonstration heat pump, implemented in the district heating network of Copenhagen, Denmark, was presented6. A genetic algorithm was applied to the model for 27 different operating conditions, optimizing the system COP by adjusting the available set points. The highest achieved COP was 4.2.

CO2 trends

At least 20,000 stores globally are using CO2 transcritical technology. The majority of these, around 16,000, are located in Europe, where they represent about 14% of the food retail market (food retail stores over 400m2), with annual growth rates of 25-40%1. According to K. Zolcer Skacanova et al1, depending on the market and technology, the total installation price is currently at the same level as conventional systems or in the range of 5-10% higher. Industry experts estimate that for warmer ambient climates using ejector and parallel compression technologies, the price of a system is about 10% higher.

CO2 use is also growing in small stores. Based on data collected from system suppliers by Shecco, an estimated 6,000+ stores use CO2 condensing units and mini boosters globally, with a growing number of suppliers offering such equipment1. In addition to commercial refrigeration, CO2is also increasingly used in other applications as illustrated by several papers presented in Ohrid.

The first combined CO2 heating, air-conditioning and hot water system installed in a Scandinavian hotel, in Norway, was presented7. It uses a CO2 heat pump and chiller unit with an integrated thermal storage. Preliminary results show significant energy savings (59-68%) and peak power reductions (15-45%). In the same domain, another paper shows that a transcritical CO2refrigerating system with parallel compression applied to the cooling and heating of buildings in Australia has very significantly reduced energy and cooling water8.

Another paper presents promising field results of a CO2 transcritical water chiller installed in 2018 in a winery in North Italy. The unit was designed to cool down glycol, which keeps temperatures under control during fermentation9.

In the field of refrigerated transport, Italian researchers presented a modelling approach to predict the performance of a refrigerated unit with CO2 as working fluid, with the possibility of using a new configuration with a two-phase ejector instead of an expansion valve10.

All papers from Ohrid conference are available in our FRIDOC database.

1 Zolcer Skacanova K. et al, Market & technology trends for CO2 and ammonia in commercial and industrial refrigeration

2 Gulanikar A. D., Revamping and expansion of milk chilling centre

3 Widell K. et al, Freezing of mackerel filets in two step freezing process

4 Taguas F. J. et al, Heat pumps for energy efficient breweries

5 Svingal J., Using low charge ammonia heat pump as main cooling/heating energy source for ice hockey stadiums

6 Jorgensen P., Performance optimization of a large-scale ammonia heat pump in off-design conditions

7 Smitt S. M. et al, Presentation of the first combined CO2heat pump, air conditioning and hot tap water system for a hotel in Scandinavia

8 Visser K., Transcritical CO2refrigerating systems applied to the cooling and heating of buildings reduce energy and cooling water

9 Tosato G., CO2-based water chiller for wineries: a case study

10 Artuso P. et al, Numerical investigation on the thermal performance of a new cooling unit for refrigerated transport using CO2 as the working fluid