Stratospheric ozone depletion as well as atmospheric greenhouse effect due to refrigerant emissions have led to drastic changes in the refrigeration and air conditioning technology since the beginning of the 1990s.
This is especially true for the area of commercial refrigeration and air conditioning systems with their wide range of applications. In former years the main refrigerants used for these systems were ozone depleting types, namely R12, R22 and R502; for special applications R114, R12B1, R13B1, R13 and R503 were used.
The use of these substances is no longer allowed in industrialised countries, but the use of R22 has been extended through transitional periods. However, the European Union also commited to an early phase-out for R22, which was enforced in several stages (R22 as transitional refrigerant). The main reason for this early ban of R22 contrary to the international agreement is the ozone depletion potential although it is only small.
Since 2010, phase-out regulations became effective in other countries as well, for instance in the USA.
This implies enormous consequences for the whole refrigeration and air conditioning sector. BITZER therefore committed itself to taking a leading role in the research and development of environmentally friendly system designs.
After the chlorine-free (ODP = 0) HFC refrigerants R134a, R404A, R407C, R507A and R410A have become widely established for many years in commercial refrigeration, air conditioning and heat pump systems, new challenges have come up. They concern primarily the greenhouse effect: The aim is a clear reduction of direct emissions caused by refrigerant losses and indirect emissions by particularly efficient system technology.
In this area, applicable legal regulations are already in force, such as the EU F-Gas Regulation No. 517/2014 (BITZER brochure A-510) and a series of regulations already ratified or in preparation as part of the EU Ecodesign Directive (BITZER brochure A-530). Similar regulations are also in preparation or already implemented in Australia, Canada and the USA. On an international level, the so-called “Kigali Amendment” was adopted in 2016 under the Montreal Protocol, in which a step-by-step reduction of HFCs (“HFC phase-down”) was agreed upon starting in 2019.
Even though indirect emissions caused by energy production are considerably higher than direct (CO2-equivalent) emissions caused by HFC refrigerants, refrigerants with high global warming potential (GWP) will in the future be subject to use restrictions or bans. This will affect primarily R404A and R507A, for which alternatives with lower GWP are already being offered. However, in order to achieve the legal objectives, substitutes for further refrigerants and increased use of naturally occurring substances (NH3, CO2, hydrocarbons) will become necessary.
This requires comprehensive testing of these refrigerants, suitable oils and adjusted systems. Therefore a close co-operation exists with scientific institutions, the refrigeration and oil industries, component manufacturers as well as a number of innovative refrigeration and air conditioning companies.
A large number of development tasks have been completed. Suitable compressors for alternative refrigerants are available.
Besides the development projects, BITZER actively supports legal regulations and self commitments concerning the responsible use of refrigerants as well as measures to increase system and components’ efficiency.
The following report deals with potential measures of a short to medium-term change towards technologies with reduced environmental impact in medium and large size commercial and industrial refrigeration, air conditioning and heat pump systems. Furthermore, the experiences so far and the resulting consequences for plant technology are discussed.
Several studies confirm that vapour compression refrigeration systems normally used commercially are far superior in efficiency to all other processes down to a cold space temperature of around -40°C.
The selection of an alternative refrigerant and the system design receives special significance, however. Besides the request for substances without ozone depletion potential (ODP = 0) especially the energy demand of a system is seen as an essential criterion due to its indirect contribution to the greenhouse effect. On top of that there is the direct global warming potential (GWP) due to refrigerant emission.
Therefore a calculation method has been developed for the qualified evaluation of a system which enables an analysis of the total influence on the greenhouse effect.
The so-called “TEWI” factor (Total Equivalent Warming Impact) has been introduced. Meanwhile, another, more extensive assessment method has been developed considering “Eco-Efficiency”. Hereby, both ecological (such as TEWI) and economical criteria are taken into account (Eco-Efficiency).
Therefore it is possible that the assessment of refrigerants with regard to the environment can differ according to the place of installation and drive method.
Upon closer evaluation of substitutes for the originally used CFC and HCFC as well as for HFCs with higher GWP, the options with single-substance refrigerants are very limited. This includes e.g. R134a, which will be usable for quite some time based on its comparatively low GWP. Similarly, the hydro-fluoro-olefins (HFO) R1234yf and R1234ze(E) with a GWP < 10, which are also exempted from the F-Gas regulation.
Direct alternatives (based on fluorinated hydrocarbons) for almost all refrigerants of higher volumetric refrigerating capacity and pressure level than R134a can (mainly) only be “formulated” as blends. However, taking into account thermodynamic properties, flammability, toxicity and global warming potential, the list of potential candidates is very limited. Blends of reduced GWP include in addition to R134a, R1234yf and R1234ze(E) primarily the refrigerants R32, R125 and R152a.
Besides halogenated refrigerants, Ammonia (NH3) and hydrocarbons are considered as substitutes as well. The use for commercial applications, however, is limited by strict safety requirements.
Carbon dioxide (CO2) becomes more important as an alternative refrigerant and secondary fluid, too. Due to its specific characteristics, however, there are restrictions to a general application.
The following illustration (Structural classification of refrigerants) shows a structural survey of the alternative refrigerants and a summary of the single or blended substances which are now available. After that the individual subjects are discussed.
For refrigerant properties, application ranges and lubricant specifications: Refrigerant Properties.
For reasons of clarity the less or only regionally known products are not specified in this issue, which is not intended to imply any inferiority.