Replacement of CFCs and HFCs
Replacement of CFCs and HFCs
The most important contribution to reduce greenhouse gases emissions.tBy replacing CFCs, which had significantly higher Global Warming Potential (GWP) by HFCs, the refrigeration and air-conditioning industry have already made the most significant and positive contribution to reducing greenhouse gas emissions.
Although CFCs are not included in the Kyoto Protocol, because they are to be phased out under the Montreal Protocol, their replacement by industry has significantly reduced the impact both on the ozone layer and climate change.
In 1990, CFCs represented 25 per cent of global greenhouse gas emissions.In 2002, the emissions from the use of HFCs were about 0.5 per cent of total global GHG emissions1.
A report issued by the International Panel on Climate Change in April 2005 (see article below) states clearly that whilst atmospheric concentrations of HFCs are rising, their contribution to climate change, measured as direct radiative forcing is expected only to be about 1% by 2015, whilst their adoption has contributed to a threefold reduction in the global warming emissions of all halocarbons. Application of best practice, improved containment and refrigerant recovery at end-of-life, has the potential to halve the projected business-as-usual of ODS and HFC emissions by 2015.
This reduction represents about four times the objective of the Kyoto Protocol. Furthermore, the responsible use of HFCs in energy efficient, cost effective, applications continues to help in achieving its targets.
The main climate impact of refrigeration : energy consumption
On average 80 % of the climate impact of applications like refrigeration or air conditioning results from CO2 emissions associated with the energy consumption of their power equipment. Energy efficiency improvements are the key element of sustainable refrigeration, irrespective of the refrigerant used. In many applications, F-gases contribute to significantly lower the associated CO2 emissions. Considered over the complete lifetime of an application, the reduction in climate impact resulting from the improved energy efficiency obtained by using an HFC is more important than the impact of emitting the HFC itself. This is supported for some applications by verified life cycle analysis available on request. Because of their good thermodynamic properties and their adaptability to various operational conditions. HFCs can be used across a wide range of application temperatures. They can be carefully selected to optimise system efficiency, from small individual air-conditioning systems to large industrial freezer units.
High performance thermal insulation of buildings and refrigerated spaces. Also, good insulation maintains refrigerated cold spaces and provides a better energy return. In blown insulated foams, it is the entrapped gas – not the polymer material – which determines the degree of insulation. Life-cycle studies show that insulation foam using HFCs can be more efficient and longer-lasting than that using other blowing agents such as hydrocarbons, water or CO2. In refrigerated transport, this advantage is reflected in the increased volume available for goods, improving thereby transport efficiency.
Systems using HFCs are continuously improving and delivering better energy efficiency, in addition to reduced refrigerant loads and lower emissions, and consequently reducing their environmental impact. The newest generation of HFC systems perform even better than those designed in 2000. Comparing HFC and non-HFC refrigerants should thus take this evolution into account and use the data for the newest systems. Comparisons between a five-year-old system and a current system do not give accurate conclusions about performance.
Direct comparisons have also shown HFCs do have the potential for better energy efficiency than hydrocarbons for some air conditioners, heat pumps, and commercial refrigeration applications. CO2 is intrinsically less efficient than HFCs for usual applications in refrigeration and air-conditioning2, mainly due to its low critical temperature of only 31°C. In the district cooling and heat pump systems (see Newsletter June 2005), HFCs provide the right balance of properties, which result in major energy savings compared to other systems.
Compared to potential alternatives, the products of the HFC family are in most cases non-flammable and have favourable toxicity profiles, a key factor for consumer applications, for use in public places and for occupational health
The responsibility of a choice
Taking into account the potential environmental impact of HFCs, 2 possibilities exist:
Either revert to the previously used toxic or highly flammable refrigerants Or the way forward, managing the use of HFCs, called “extremely useful chemicals”, in a way to minimize their impact on the environment. In the first case, safety remains a fundamental issue in comparison with HFCs. Highly flammable or toxic refrigerants require the additional risks they present to be taken into account. In most cases the additional flammability and toxicity risks posed by alternative non-HFC refrigerants implies additional costs for safety, and can also lead in some situations to lower efficiency and increased energy consumption. The advantage of the second route is the need for reduced safety requirements and investment. The added “cost of safety” could indeed be more effectively invested in further energy saving measures, and in minimizing HFC emissions.
Technical and Economic reasons
HFCs belong to the family of F-gases often vital to our daily life. They are hydrocarbons containing fluorine atoms that give them their exceptional properties.
The range of available HFCs, used pure or blended, allows to design “tailor-made” systems for specific application sectors, and to deliver higher performances.
The range of available HFCs allows also a wide variety of applications, like among others :
1 Emissions of HFC-134a were zero in 1990, so an initial high growth rate was to be anticipated. The 1996 emission rate is actually only 0.1% of all global GHG emissions in the base year for the Kyoto Protocol, and emissions of 0.032 Tg/yr of R134a can be compared to the approximate 30,000 Tg/yr of CO2 emitted annually.
2 An in-depth theoretical analysis has concluded that the biggest contributors to the lower CO2 performance are irreversibilities associated with the heat rejection process and the expansion related processes the expansion related processes http://fire.nist.gov/bfrlpubs/build02/PDF/b02184.pdf