To estimate present emissions and their future development, a comprehensive modelling approach was applied. The first step was to model the stock, i.e. the number of appliances in use in the various countries. Future unit sales and emissions were derived from the modelled stock.
The stock for the various RAC subsectors was calculated by two different methods, depending on the available data. The list of covered systems is not comprehensive.
Where it was possible, a sophisticated modelling approach was chosen to estimate the stock, where a relationship is built between the current response (stock, diffusion rate, ownership) and the current predictor variables. The following predictors were considered: Population, GDP, temperature index, urbanisation and electrification rates. Specifically, generalised linear models and generalised additive models were used to model the stock accordingly. Penetration rates for domestic refrigerators were taken from McNeil & Letschert (2008).
This detailed approach requires very specific information, and it is thus limited to RAC systems with a sound database to calibrate the models.
A simpler modelling approach to calculate the stock is based on ratios of RAC systems per inhabitants. These ratios were primarily built based on data given in Schwarz et al. (2011) who provide numbers of RAC equipment for developing and developed countries. Using this approach, the only factors that determine the stock are population and number of households. This approach is limited in its informative value, because it does not reflect purchasing power or climatic conditions. However, it gives a first estimate about the number of systems in use. The table below shows which approach was applied to the different systems.
|RAC Subsector||Sophisticated approach||Simple ratio approach|
|Unitary air conditioning||Split residential AC||Self-contained AC Commercial ducted splits Multi-splits|
|Chillers||Air conditioning chillers|
|Mobile air conditioning||MAC in passenger cars||Large vehicle AC (buses only)|
|Domestic refrigeration||Domestic refrigeration|
|Commercial refrigeration||Stand-alone equipment Condensing units Centralised systems|
|Industrial refrigeration||Centralised systems|
|Transport refrigeration||Refrigerated trucks/trailers|
The modelled stock was used to derive unit sales figures, taking into account that a certain part of the equipment is decommissioned at end-of-life. Multiplying the unit sales figures by current unit market prices results in market value estimates.
The stock and sales figures were then used to calculate current and future CO2 emissions, accounting for direct (refrigerants) and indirect (energy consumption) emissions. Therefore a vintage bottom-up stock model was used, considering additional parameters such as initial charge, cooling capacity, emission factors for each of the appliance types.
In order to assess the effect of mitigation strategies two different scenarios were calculated: a business-as-usual (BAU) scenario and a mitigation scenario which considers the change of the refrigerant and system design and improvements in the energy efficiency. A comparison between the BAU scenario and the mitigation scenario results in the mitigation potential.
Calculations were done separately for developed and developing countries as the type of equipment, energy efficiency and refrigerants differ substantially.
A full description of this vintage bottom-up stock model can be found in module 1 of the GIZ technical handbook on NAMAs in the RAC&F sectors (GIZ 2013).
Although this data has been compiled with care, its processing, analyses and modelling have required a number of compromises to be made. Therefore, this data may deviate from actual numbers in countries. If you have better data for your country or a specific subsector or appliance system, you can help us improve our database.