ACRIB issues statement on future HFC policies - 10/11/2009

 

Industry agrees that direct emissions from the use of HFC refrigerants which have a high global warming potential need to be curbed. It is fully behind the effective implementation of the F Gas Regulations designed to reduce these emissions. However in order to make the substantial reductions in carbon emissions for the sector required, a policy framework, which takes into account total emissions ie both indirect emissions through energy use and direct emissions through leakage, is necessary. By focusing on restrictions on one specific refrigerant fluid, there is a risk that the industry will be forced into making system design decisions which compromise system efficiency – and therefore contribute to increased carbon emissions in the long term.

ACRIB is equally concerned that by “phase down” most system operators are likely to believe it means “phase out”. (Phase down has been defined by Government officials as a move which would allow exemptions for certain critical applications and a reduction in manufacture and supply accordingly and is not a complete ban on use.) This comes at an unfortunate time when many end users are considering their options with regard to the soon to be phased out ODS refrigerants in their existing equipment, and are looking for certainty in their options rather than more restrictions. System operators need to be confident that efficient equipment installed in the next few years can continue to be used and serviced cost effectively throughout its lifetime.

 

UK Government policy advisers suggest that negotiation of a position sometime during 2010 remains the most likely realistic approach. Once formal discussions by Parties to the Montreal Protocol begin to take place, the sectors of UK industry affected are very keen to engage in a formal consultation process to help ensure legislation reduces emissions in the most appropriate and effective manner, taking into account the performance and availability of new lower GWP refrigerants and systems using low or zero GWP refrigerants.

The Institute of Refrigeration Guidance note on Refrigerant Selection and System Design issued earlier this year gives a much fuller picture of the linkage between carbon emissions reduction and selection of refrigerant and as such ACRIB member organisations endorse this balanced position (see extract below).

 

 

 

 

 

The Institute of Refrigeration has compiled this guidance note to provide non-partisan advice on the effects of refrigerant choice and system design on the carbon footprint of a refrigerating system. Two effects are considered: the direct global warming potential of the refrigerant selected and the climate change effect of energy use by the system. The direct effect is measured as a “global warming potential” (GWP), usually against a reference of the potential of carbon dioxide over a 100 year period. Strategies for the reduction of carbon footprint include designing more efficient systems, minimising sources of leakage through the selection of more robust system components, reducing the quantity of refrigerant required to operate the system in order to mitigate the effect of a large leak and substituting refrigerants with a high GWP for those with a lower potential. These include ammonia, hydrocarbons, carbon dioxide, some low-GWP HFCs and hydrofluoroolefins (also known as unsaturated HFCs or HFOs)

 

There are many situations where the direct substitution of a hydrofluorocarbon (HFC) with a “natural” refrigerant is not reasonably practicable, either due to toxicity or flammability or high pressure. In such cases it would be possible to minimise HFC charge, or even eliminate it, by using a secondary fluid but this would tend to make the alternative system more expensive and less efficient. Rather than promoting a total ban of HFCs a more appropriate course would be to advocate a policy of “responsible use” of fluorocarbons in order to ensure that the climate effects of refrigerant emissions are minimised. A responsible refrigerant policy would place a high emphasis on the elimination of leak sources, the efficiency of the overall system and the life cycle cost of ownership.  

 

 

 

Energy Efficiency of refrigeration systems is governed by the laws of physics and by practicality. Practicality embraces cost, cycle, legislative requirements, refrigerant choice and maintenance. Efficiency is not only dependent on choice of refrigerant but also on good design, selection of an appropriate system and good maintenance. Selection of the refrigerant demonstrating highest efficiency in an appropriate system is unlikely to improve system efficiency by more than 10% over efficiency of an optimized system using an HFC refrigerant. Some “natural” refrigerants such as carbon dioxide may result in reduced system efficiency unless they are integrated into a heat recovery system. At current levels of knowledge and expertise, practicality often leads to a choice of HFCs for good efficiency to be realistically achieved and maintained. In some applications, ammonia, carbon dioxide or hydrocarbons would be the preferred choice, but these refrigerants are not suitable for all applications. Good efficiency is vital to minimize emissions of greenhouse gases.

 

 

The practicality element will change as costs and design changes associated with HFC use evolve, and more components, experience and skills for ammonia, HCs and CO2 are developed. This can be expected to reduce the applications that require HFCs, but not eliminate them in the foreseeable future. Examples of highly practical HFC applications include split A/C systems, and in particular VRF combined cooling/heating systems. 

Arbitrary constraints on how designers can specify systems (such as bans on the use of specific refrigerant fluids) could result in less efficient systems being installed and will not drive the industry along the path of lowest GHG emissions.

 

To obtain ‘good efficiency’ attention needs to be given to the following steps:

1) Avoid refrigeration / reduce the cooling load. This is the most important first step – there is no point designing an efficient system if the load was unnecessary!

2) Get the overall system design right (e.g. best cycle, splitting loads at different temperatures onto different suction levels, etc. etc)

3) Get the control philosophy right (don’t forget the “off-design” operating conditions which are much more common than the peak “design point”, avoid head pressure control, avoid partly loaded compressors, avoid fixed speed auxiliaries like pumps and fans, etc. etc.)

4) Optimise individual components for efficiency (e.g. how big should heat exchangers be, which compressor has best efficiency etc.)

5) Operate and maintain the plant for best efficiency.

 

Mistakes in any of the above can change the efficiency of a plant by large amounts (e.g. 20% to 50%). Where does refrigerant selection fit in? It can either be thought of as a system design issue or a “component optimisation”. The impact of the refrigerant on efficiency is likely to be less than 5%, assuming all other design parameters are optimized.