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Natural refrigerants, continuously growing!

Natural refrigerants, continuously growing!

The question is no longer whether or not to use natural refrigerants, but rather which one. This is the feeling I took away from the second Virtual Trade Show (VTS) organised by Shecco on 30-31 March. Propane or CO in commercial refrigeration? Ammonia or CO in industrial applications? Propane, ammonia or CO for heat pumps? These are some of the questions that emerged during the event and that more than one of you reading this post may have asked yourselves. The use of natural refrigerants is growing at a frenetic pace, and new innovations allow different ones to be adopted in applications where they have never been used before!

Before starting with the main findings coming out of the event, I cannot neglect to mention that in the week I am writing this post, the USA and China have committed to implementing the Kigali Amendment to the Montreal Protocol. Having this commitment from two of the major producers and users of HFCs represents many steps forward on the road to phasing down these refrigerants and implementing solutions with natural refrigerants!

Getting back to the VTS then, I will summarise the topics that were discussed in three parts: the first regards the future and why natural refrigerants could be the only solution for sustainable cooling, the second one the current research into technologies for different types of natural refrigerants, and the third the evolutions thus far, with some examples on how the use of refrigerants has grown over the last 15 years. Looking at the future, the present and the past of natural refrigerants can help understand how their use is growing and how technologies are evolving.

There are already 119 countries (out of 197) that have ratified/accepted the Kigali Amendment to the Montreal Protocol and, according to Ilana Koegelenberg from Shecco, many more will join this year. Sooner or later, low GWP refrigerants will become the only (or predominant) option worldwide.

So far, the only available low-GWP alternative to natural refrigerants is the new class of synthetic refrigerants: HFOs. During his presentation at the VTS, Arno Kaschl from the European Commission recognised that there are some sectors in which HFOs have helped the phase-down of HFCs. However, he mentioned that there is lot of ongoing research into understanding the potential negative effects on the environment of these refrigerants, as also highlighted in other presentations. For instance, Koegelenberg specified that the by-product trifluoroacetic acid (TFA) can potentially cause acid rain and that long-term exposure to HFO refrigerants can potentially damage the liver and thyroid function in humans. Tim Grabiel from EIA and Andreas Meier from TEKO pointed out that the manufacture of HFOs is very complex. Specifically, Meier described how the synthesis process is multi-stage and produces intermediates with a high climate impact.

We will have to wait to see the results of the studies on the effects on HFOs on the environment and how the institutions will act in terms of regulations. In the meantime, the F-gas regulations are under review and hopefully we will see a proposal aligned with the Kigali amendment by the end of this year, with a final version in 2023, as stated by Kaschl. The content of the new regulations will be key to understanding which refrigerants will be used over the coming years in Europe. 

It is clear that the use of low-GWP refrigerants needs to be accompanied by high-efficiency solutions that help also reduce indirect CO emissions. “Efficiency is key”, Koegelenberg pointed out. Indeed, during my presentation, I specified that from the 210 to 460 Gt of CO2 emissions that can be avoided over the coming four decades by phasing down HFC refrigerants and improving system efficiency, three quarters would come from energy efficiency. Moreover, the proportion of energy used for cooling represents a significant portion of the total. For example, in Germany about 19% of total power is used in refrigeration processes, as indicated by Thomas Frank from Refolution Industriekälte.

Currently, the development of natural refrigerant technologies has a different focus depending on the main drawbacks of each refrigerant, while always aiming at maintaining or increasing system performance.

The main scope of CO technological innovation is indeed to increase efficiency. Heat recovery is one of the methods that optimise system performance: “the best way to use CO is to fully utilise the heat produced”, explained Wynand Groenewald, from FGN. Indeed, he specified different uses for heat recovery: domestic hot water, washing requirements, space heating, underfloor heating. This is due to the different temperatures of supercritical CO from compression to expansion in a transcritical cycle. Obviously, the use of different heat exchangers for different uses is necessary for heat recovery, as highlighted Alessio Fadini from Alfa Laval. Moreover, my colleague Matteo Dal Corso presented an example of a CO rack system with heat recovery that also includes other energy-saving technologies, such as parallel compression, ejectors and evaporative cooling.

From a practical point of view, good results with CO are being achieved. For instance, Jeffrey Carlson showed an example of two shops in Minnesota, one with COand one with an HFC, where the energy savings over the year are 22% when using CO2 compared with the HFC. These results can mean wider use of CO in smaller systems. Indeed, Britta Paetzold from HEAT pointed out that heat recovery offers high energy saving potential for stores with an area below 400 m using centralised systems, as already widely used (> 70%) in stores over 400 m in area.

Clearly, the development of CO technologies is making giant steps and will very probably also be used in new applications. Perhaps Gustav Lorentzen was right when he said “CO is as close to the ideal refrigerant as is possible”, as illustrated by Giacomi Pisano from Dorin at the end of his presentation.

Ammonia is moving in the direction of reductions in refrigerant charge, which will possibly extend its use to more applications. On this topic, José Expósito from Intarcom presented a solution for a packaged chiller where the charge can be as low as 70 g/kW of cooling capacity, without the need for an equipment room due to the inclusion of the electrical cabinet in the system. The solution includes a semi-hermetic compressor, which reduces the possibility of leakage, a double-wall (DW) plate heat exchanger for preventing the possibility of mixing between ammonia and water, and stainless steel to avoid rust in the system. 

As regards propane, many solutions presented looked at waterloop systems, which reduce refrigerant charge and thus make it easier to comply with safety standards. This type of system is also ideal for heat recovery, avoiding the need to use other heat sources, as pointed out by Collin Bootsveld from Colruyt Group. Javier Cano from Intarcom listed some of the advantages of having a plug&play unit: hermetic system pre-charged with refrigerant, factory tested and configured, and water connections using plastic piping. My colleague Marco Fusca presented a solution for waterloop systems, HEOS, which can achieve high performance thanks to continuous modulation. Richard Taylor from Pick n Pay mentioned that this kind of system is being used in some Pick n Pay stores in South Africa.

The number of systems with natural refrigerants has grown over the last 15 years, with a huge increase in the speed in the last five years, as highlighted by several end users and other speakers during VTS. Taylor called it the “road to natural refrigerants!”, from 3 Pick n Pay stores with ammonia glycol systems in 2008/9 to new 34 transcritical CO2 stores expected this year. Olaf Schulz from METRO Ag specified that they have installed 121 transcritical CO shops and more than 20 more are expected in 2021. Dario Ferlin from Woolworths also talked about their history with CO, with the first store opened in 2006 that involved a combination of CO and CO to a total of more than 350 CO2/R-134a plus 39 with transcritical CO2. As regards low-charge ammonia, Koegelenberg showed that 2200 systems were already installed in 2019 in Europe, 870 in Japan and 530 in USA.

It was also interesting to hear about the current scenario in Asia Pacific, as explained by Jan Dusek from Shecco, who specified that there are estimated to be more than 1 million vending machines using the hydrocarbon R-600a and more than 7 million natural refrigerant heat pump water heaters in Japan, as well as more than 270000 hydrocarbon room air conditioners and hundreds of thousands of hydrocarbon plug-in systems in China.

When an event such as VTS ends, it is normal to wonder how much the use of natural refrigerants will grow before the next event. We are privileged to be living through this historical transition of the HVAC/R sector, not only involving a change in refrigerant but a new approach in which innovation is playing a very important role.

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