The 13th Gustav Lorentzen Conference took place from 18th to 20th June 2018 in Valencia, Spain. 299 participants from 45 countries have updated their knowhow regarding natural refrigerants through 153 lectures and 26 posters. The main topic was clear: half of all contributions focused on carbon dioxide (CO₂ or R744). Today, there is no need of a crystal-ball to predict that CO₂ will play an enormously important role in the future refrigerating and heat pump sector. Due to its excellent thermodynamic properties, it is expected that CO₂ will also be widely used in heating, ventilation and air conditioning systems. This technology for example is already promisingly used in integral systems in the retail-sector where it covers the total thermal heating and cooling requirements of a building.

In the lecture held by Frigo-Consulting, first operating experiences of two CO₂ refrigeration systems in a fish processing plant were presented. Jonas Schönenberger highlighted the advantages of the CO₂ refrigeration systems with ejectors, which have been in operation since summer 2017 very close to the conference location in Valencia. An investigation has shown that CO₂, despite an annual mean temperature of +18°C in Valencia, it is a very efficient and sustainable solution. The extraordinary thing about these CO₂ refrigeration systems is the fact that they cover four different evaporation temperatures from -45°C to +2°C and provide the energy for the high demand of hot water. During the engineering phase, great attention was paid to achieving the low evaporation temperature of -45°C. Since the low temperature speeds up the freezing process of the fish, time could be saved. Thanks to this, 24 tons of fish per day can be frozen.

Approximately one third of the conference's main topics were hydrocarbons and ammonia. To achieve the environmental goals formulated by the F-Gas Regulation and the Kigali Amendment, experts agree that there is no way around flammable refrigerants such as hydrocarbons and ammonia. Tremendous effort is given to develop compact and low charge systems for flammable refrigerant, so that in case of leakage, the risk is minimized. The remaining 20% of the presentations focused mainly on absorption / adsorption systems, other safety aspects and market developments.

In an exciting keynote lecture, Dr. Piotr Domanski of the National Institute of Standards and Technology, highlighted the approach searching for new refrigerants. Over 32,000 different fluids have been investigated for the use as refrigerants. Only 28 of them fulfill the thermodynamic and ecological requirements of future refrigerants. The highest potential of the remaining fluids is predicted to natural fluids like ammonia, carbon dioxide and propane. The lowest potential of the remaining fluids is predicted to latest 4th generation refrigerants, the HFOs. With regards to energy efficiency and volumetric cooling capacity, their potential is far too low to play a leading role in the future refrigeration and heat pump sector. In addition, these substances are expected to pose a new significant risk to the environment. According to Domanski, it can be assumed that there will not be a 5th generation of refrigerants. Today, the potential of natural refrigerants is far too big with today's level of knowhow and available technologies, such as ejectors or parallel compression.

The combination of ejectors or parallel compression was also analysed by Ekaterini Kriezi from Danfoss, who presented the results of an investigation related to the payback times of the latest technologies with CO₂. According to her calculation, the payback time of the ejector technology is between 1 and 6 years, depending on latitude and application. A further study by Samer Sawalha of the Royal Institute of Technology Sweden, was devoted to the comparison of various concepts in the retail sector. Among other things, CO₂ refrigeration systems were compared with propane water loop systems. Sawalha came to the conclusion that water loop systems achieve about the same efficiency as conventional CO₂ refrigeration systems. Compared to CO₂ ejector systems, their energy consumption is approximately 20-30% higher. In addition, the waste heat from water loop systems cannot be used to the same extent as with CO₂ systems.

In summary, the conference was a great success. The direction is clear: natural refrigerants, especially carbon dioxide because it is efficient, sustainable and, last but not least, non-flammable.
 

05.07.2018