The increasing availability in Europe of optimised R290 compressors for heat pumps is reviving interest in the technology. During the UNIDO ATMOsphere Technology Summit, hydrocarbons21.com interviewed Mr. Daniel Colbourne, Consultant at Re-phridge, about the historical development of hydrocarbon (HC) heat pumps and the current state of play in Europe.
hydrocarbons21.com: In the 1990s there were several hydrocarbon-based heat pump products for domestic application in the EU market, which subsequently disappeared. What in your view might have caused this?
Daniel Colbourne: There were many hydrocarbon (HC) heat pump products on the European market; Austria, Switzerland, Scandinavia and Germany, mainly from small and medium sized producers. But the EU Pressure Equipment Directive (PED) was introduced which basically states that the components and piping in the refrigeration system must be designed, tested and approved for that particular refrigerant (or refrigerant “group”). The PED requirements for flammable refrigerants are one level above those for the non-flammable, low toxicity fluid “group”, which includes refrigerants like R22.
Previously many companies were taking R22 compressors and adapting them for use with R290. So when the PED came into force it essentially meant that they could no longer utilise those R22 compressors; i.e., they could only use R290 compressors for R290. At the time there were no manufacturers producing the right type of R290 compressors and, since in order to certify compressors for R290, additional approval processes are necessary (which in some cases are costly), the size of the market was evidently not sufficient for manufacturers to justify it. For example, the person that is welding the compressors has got to have a higher level of certification, which implies additional investments for the compressor manufacturers.
So the heat pump manufacturers apparently had little choice, all they could do was to switch to an alternative which was not a flammable refrigerant. I would say that was the main reason for the decline. Given the extensive literature demonstrating the comparatively higher efficiency of R290 and the excellent safety record, it was not performance or hazardous aspects that were responsible.
A number of manufacturers continued with some R290 models (and still do today) in particular for smaller capacity units where R290 hermetic compressors normally used for commercial refrigeration are suitable. Nonetheless, this represents a relatively small portion of the market.
hydrocarbons21.com: In terms of performance and reliability, how were these R290 products performing?
Colbourne: With regards to reliability, when R22 compressors were initially used there were some problems. However, a study presented by a major German player on the development of their R290 heat pumps in 1999 stated that after optimisation of the compressor oil, the reliability of their R290 heat pumps was better than that of their R22 heat pumps. Of course, many companies are currently selling R290 heat pumps, which would not be the case were there reliability issues.
Throughout that period there were many studies published on the efficiency of hydrocarbons in heat pumps and most of them said that R290 performance was at least as good, typically much better than the other alternatives (for space heating purposes). Both the large volume of technical literature and publications from different manufacturers support this. Furthermore, when considering the thermophysical properties of HCs, it is fairly obvious; not only do the thermodynamic properties demonstrate this but also the excellent viscosity and thermal conductivity infers better component performance than most other fluorinated alternatives.
hydrocarbons21.com: More recently do you see a renewed interest in the use of hydrocarbons in heat pumps by European manufacturers?
Colbourne: In general we can see increasing pressure to use heat pumps in Europe as they are seen as a means for accelerating CO2 emission reduction. Within this context it seems rather daft to not use low-GWP refrigerants or particularly natural refrigerants for those types of products where they can be used. There are a fairly large number of manufacturers within Europe (but also Australia and China) that are currently using HCs (as well as other natural refrigerants). In this respect there is increasing interest in some quarters, but of course others are also resisting.
The safety issue is surely already addressed, since relevant safety regulations and standards are available and have been for many years.
hydrocarbons21.com: Heat pump manufacturers often state that the reason they do not offer HC-based heat pumps is that they cannot find optimised HC compressors or other components for the purpose. What would you recommend to the industry for overcoming this barrier?
Colbourne: On the compressor side, at least two major compressor manufacturers are now producing compressors specifically designed and optimised for R290 heat pump systems, implying that this barrier is now becoming resolved. Moreover, there are several companies that make other components, such as controls for hydrocarbons that can be used in heat pumps. These enterprises obviously see that there is a market and they would not invest large sums in the technology unless they had confidence in it.