Background article

Count-down for the phase-out

The phase-out which started at the beginning of the year will further boost the use of natural refrigerants in industry and in air-conditioning systems for buildings. On 1 January 2016, the EU reduced the permitted total quantity of climate-damaging F-gases by 7 %. Experts see high ecological and economic potential in using natural refrigerants for air-conditioning systems in buildings.

The European Union wants to bring about a 20 % reduction in greenhouse gas emissions by the year 2020. The so-called F-gases are an important lever in this respect. F-gases are partly fluorinated hydrocarbons which are used among others as refrigerant in air-conditioning systems for buildings and for generating industrial refrigeration. The revised F-gases Regulation will, by law, implement a 79 % reduction in the quantity of climate-damaging F-gases used throughout Europe in six stages through to 2030, referred to the European average from the years 2009 to 2012. The first stage with a 7 % reduction came into effect on 1 January 2016. Implementing a controlled shortage of F-gases in this way as part of the phase-out strategy will make climate-damaging refrigerants successively more expensive, thus indirectly promoting the use of natural refrigerants. Natural refrigerants make both ecological and economic sense, and systems using them are currently in great demand for air-conditioning systems in buildings.

Natural refrigerants are sustainable

One of the reasons for gradually prohibiting F-gases consists in their large contribution to global warming. In order to quantify the impact a gas has on global warming, the global warming potential (GWP) was introduced as an objective measurement parameter. The natural refrigerant CO2 has a GWP of 1. By contrast, the F-gas R22 has a GWP of 1,700, while the widespread refrigerant R404a even has a GWP of 3,922. Depending on the particular refrigerant, chlorofluorocarbons (CFCs) can even reach a GWP in excess of 10,000. The legislator is now intervening here with the revised F-gases Regulation: from 2020 onwards, stationary systems may no longer operate with refrigerants that have a GWP > 2,500.

Another parameter indicating the sustainability of a substance is the ODP. The ODP (ozone depletion potential) indicates to what extent a substance harms the ozone layer. In new systems, refrigerants with an ODP > 0 are not allowed anymore for a long time already. None of the natural refrigerants contributes to ozone depletion, which means ODP = 0, whereas R22 is still used as a refrigerant in many existing systems although it contributes to the ozone depletion and should thus be replaced urgently.

Leakage limits for synthetic refrigerants make hermetic systems necessary

To minimise the environmentally harmful effect of F-gases, the first version of the F-gases Regulation in 2007 stipulated maximum leakage limits for refrigerants. Depending on the system size, the leakage rate for synthetic refrigerants may not exceed a maximum of 1 to 3 percent.

Since the revision of the F-gases Regulation, system operators also have to face up to extended operator obligations, including among others verifying that their system is leakage-free. If the stipulated leakage limits are not verifiably met in the next few years, legislation can be expected to become even tighter, through to a progressive prohibition of certain refrigerants. As a result, planners and system engineers will therefore give greater significance to hermetically sealed solutions when planning systems with synthetic refrigerants. Hitherto systems with high safety requirements were required particularly when planning to use refrigerants that pose a health hazard or are explosive.

Energy efficiency scores!

When looking at the contribution refrigeration systems make to global warming, it transpires that only 20 % of the climate-damaging effect comes from leaks of synthetic refrigerants. The remaining 80 % come from the amount of energy needed during refrigeration production. Here too, systems with natural refrigerants offer benefits in both ecological and economic terms, due among others to the outstanding thermodynamic properties of natural refrigerants. NH3/CO2 cascade systems in particular generate energy savings of up to 35 % compared to similar systems with hydrofluorocarbons (HCFC systems).

Profitable in economic terms

Detailed analysis shows that systems with natural refrigerants are often the best choice also in economic terms. When calculating the payback period, all costs occurring during the life cycle of a system have to be taken into consideration. These include the initial outlay and all subsequent costs, in other words, the costs for planning and installing the system and subsequent expenditure on energy, servicing and maintenance. Natural refrigerants offer convincing values in this respect. Although they make higher demands of system safety than synthetic refrigerants, their higher energy efficiency generates clear cut backs in operating costs; furthermore, the systems are rated for a longer service life, usually amounting to 25 years and more. In overall economic terms, natural refrigerants offer greater cost advantages.

Optimum rating of the system

There is one important aspect that has to be taken into account to make full use of all the advantages of systems with natural refrigerants. The energy consumption of a refrigeration system is influenced not just by choosing the right refrigerant but, above all, by the rating of the system. For example, the operation of a screw compressor with shutter slide control in the lower part-load area can result in higher pressure levels that exceed the optimum operating pressure, resulting in clearly reduced energy efficiency for the overall system. Comprehensive know-how lets planners and operators realise great potential savings in this respect.

Trend: using ammonia for air-conditioning in buildings

Systems with natural refrigerants are currently finding increasing use in atypical applications. Ammonia is no longer used just in industrial refrigeration for capacities exceeding 500 kW; meanwhile it is also taking over areas that used to be the domain of synthetic refrigerants, such as air-conditioning in buildings. Many large exhibition halls in Germany have been equipped with ammonia liquid chillers for air-conditioning. Banks, insurance companies and office buildings also make increasing use of natural refrigerants for air-conditioning. Furthermore, the trend is spreading to areas with high safety requirements: risk analyses have shown that refrigeration systems with natural refrigerants are no greater potential hazard than systems with synthetic refrigerants so that refrigeration systems operating with ammonia are also being used for air-conditioning in airports. Examples here include the refurbished Düsseldorf Airport, the new Terminal 5 at London Heathrow or Zurich Airport.

Developments with hydrocarbons

The trend to use natural refrigerants for air-conditioning in buildings also applies to systems operating with hydrocarbons such as propane, butane and butene. Propane has very similar thermodynamic properties to the synthetic refrigerant R22. Some Asian countries have therefore replaced R22 with propane in central air-conditioning systems and report cut-backs in energy consumption between 10 and 30 percent with only minimum modifications necessary to the systems.

Conclusion: natural refrigerants are (usually) the best

Triggered by the F-gases Regulation, planners and operators are increasingly looking at where and how it makes sense to use refrigeration systems with natural refrigerants, thus reflecting the increasingly widespread use of natural refrigerants in air-conditioning for buildings. Besides a growing environmental awareness, this is also due to economic advantages. The significance of natural refrigerants therefore continues to grow worldwide.