Conversion Efficiency in 2060

Even though the ETP model is a bottom-up model, conversion efficiency is not always modelled explicitly–for example vehicle fuel consumption (in units of l/100km) is the modelled efficiency metric, not engine efficiency–while in other cases conversion efficiency is modelled explicitly (e.g. boiler efficiency in buildings) but the assumed values are not always described in the publication. To isolate the improvement in conversion device efficiency

assumed in the model additional information is retrieved from the background literature used by the modellers and from personal communication with IEA staff. In this section, the general method to attribute energy intensity improvements to efficiency improvements is described, then the data sources and assumptions used for each conversion device are described in detail.

Where energy efficiency improvements are included within energy intensity metrics two steps are required to convert these estimates into conversion efficiency improvements. An energy intensity (i) defines the Final energy input (Eⁱⁿ) required to provide a unit of service (S).

i= Eⁱⁿ S

However, this reduction includes all types of technical improvements which include improve-ments in passive systems, operation, and conversion device efficiency. The first step is to identify the share of this reduction attributable to conversion devices (s_η). Therefore the energy intensity reductions attributable to conversion devices are defined as

∆i

The value for s_η is determined by inspecting the sources used by the modellers to quantify the energy intensity reduction. The sources include breakdowns of the effects of the different technical improvements that lead to the state energy intensity reduction. The second step is to convert this value in a change in conversion efficiency. Starting from the definition of an energy intensity change from t to t+1

∆i and from the definition of conversion efficiency

η = E^out Eⁱⁿ

∆i

Since the change in intensity is only referring to the changes occurring thanks to the conver-sion device improvements, the energy output per unit of service at time t and t+1 is equal (E_t+1^out = E_t^out). Therefore, the above equation can be written as

∆i

taking into account that the energy intensity term is always negative when it refers to a reduction in energy intensity due to efficiency improvements.

Transport

Road - light duty In the ETP publication, the fuel economy (l/100km) of cars is expected to improve by 36% respectively by 2060, with only small variations among scenarios. The estimate is based on a technical assessment developed by the EU’s Joint Research Center [413], where the contribution engine improvements accounts for 44% f the total fuel economy improvements for gasoline and diesel engines respectively. As described in chapter 4, the difference between spark ignition and compression ignition is likely to fade in the coming decades, therefore these separate categories of conversion devices, are considered as a single one named “Reciprocating Engines” and its efficiency improvements are defined as the weighted average of spark ignition and diesel engines. The average efficiency of engine operation in road transport is also a function of the share of vehicles with hybrid powertrains.

Hybrid cars are more efficient as the engine always operate at a single speed and peak efficiency therefore the share of hybrids must be taken into account to assess the expected engine efficiency. Hybrid engines are assumed to have 85% of the losses of conventional vehicles, as described in section 4.2.7. The share of hybrids in 2060 is 62%, 52%, and 31% in the B2DS, 2DS and RTS respectively. For electric vehicles, fuel economy improvements of 6% are assumed for all scenarios by the year 2060. Of these improvements, 44% is assumed to be attributable to motor improvement (same as for gasoline vehicles).

Road - heavy duty The fuel consumption (l/100km) of trucks is expected to decrease by 35% in the B2DS and 23% in the RTS, by 2060. The estimate is based on a study performed by the Global Fuel Economy Initiative [414], where a 10 percentage point increase in engine break thermal efficiency is assumed possible. This increase corresponds to a 18% energy intensity reduction. The share of hybrids in the heavy duty trucks sector influences the average engine efficiency in each scenario, with 78%, 71% and 11% in the B2DS, 2DS and RTS respectively.

Navigation The energy intensity of freight ships (MJ/vkm) is assumed to decrease by 37%

and 65% in the RTS and B2DS scenario with respect to 2015 consumption. These values were obtained from a report commissioned by the International Marine Organisation on the potential for GHG emission reduction [415, 416]. The report lists a number of technical measures and provides an estimate for energy reduction potential of each. Energy efficiency improvements in engine account for 19% of overall energy reduction, with the remainder resulting from passive system and operational improvements.

Aviation : The energy intensity of air transport (MJ/pkm) is assumed to decrease by 57%

and 68% in the RTS and B2DS respectively, compared to 2015. These values are in line with industry association climate targets, and are deemed technologically feasible, according to the IATA Technological Roadmap [417, 418]. The contribution of engine improvements in the IATA Roadmap can be isolated from the overall fuel reduction measures (i.e. including passive system improvement) and its contribution ranges from 39% to 49% of the overall fuel burn reduction.

Buildings

Heat Pumps In the ETP report it is stated that the efficiency of Heat pumps is expected to reach values that range from 4 to 4.5 but no mention is made with respect to how this value might vary in the different scenarios. Personal communication with the IEA staff suggests that global average COP values of around 4.0 are to be expected for the RTS scenario while 4.5 is in line with the values assumed for the two climate scenarios. Higher uncertainty is associated with heat pumps in the model due to the low quality of the available information.

Air conditioning The IEA’s ETP publication provides no specific information on the efficiency of coolers in the different scenarios. However, a more recent publication focusing

on future air conditioning [419] developed using the same model, provides explicit estimates about future seasonal efficiency ratings. This new publication uses two scenarios, a baseline and an efficient scenario. In terms of assumed SEERs the baseline scenario is similar to the RTS and the efficient scenario is in line with both the 2DS and B2DS according to personal communication with IEA staff. Therefore, the SEER for air conditioners is believed to range between 4.9 and 5.6 in RTS, and between 8.5 and 9.5 in the climate scenarios

For air conditioners it is also necessary to update the technical efficiency limit value obtained in section 4.2.4 because the TEL of air conditioners is a function of the average climatic conditions, and the TEL are scaled to reflect the seasonal efficiency of an air conditioner in western Europe, using the EU’s SEER metric. Therefore, this value needs to be scaled to reflect the global average climate, where summer temperatures are higher on average compared to EU temperatures. The UNFCC has developed tools that provide a methodology to translate these values using standard conversion factors [420]. These conversion factors range from 89% to 90% to convert EU standard into those of other countries. Therefore, the TEL obtained in section 4.2.4 is scaled by multiplying it with a uniform distribution ranging from 0.89 to 1.

Boilers The IEA’s ETP states that gas boilers have efficiencies that range from 80% to 90%

but does not explicitly mention their efficiency developments in future years. Yet, the report mentions condensing boilers with an efficiency of 90%. This is in line with the ETSAP [227]

data on new boilers. It therefore seems like no improvement beyond this value is assumed in any of the scenarios. Since the information on boilers is scarce, the uncertainly associated with the efficiency estimates is larger than for other devices.

Industry and other devices

The IEA’s ETP report gives not data on efficiency improvements in cross-sector technologies in industry such as electric motors and steam generators. That is because the industry module is based on industrial processes rather than on individual technical devices. For this reason, it will be assumed that efficiency remains constant for these industrial devices, as efforts will likely be focused on process level changes that will substitute carbon intensive processes with carbon neutral ones. Lighting efficiency is assumed to be the same as the one calculated for the UK in absence of global efficiency estimates.

Energy balances and Sankey diagram

The assumptions outlined in the previous sections enable the estimation of Useful energy balances for the global energy system in each scenario and at each point in time through to 2060. This is done simply by multiplying the Final energy demand for each device with its estimated conversion efficiency at each time point and for each scenario. The resulting Useful energy consumption values are then aggregated and presented in the form of an energy balance and compared to the standard Final energy balance.

The resulting energy balances are displayed using a Sankey diagram which has been recog-nised as a useful tool to facilitate the communication of large energy consumption data set [421]. As seen in previous chapters, efficiency values for boilers and vapour compression devices (heat pumps and air coolers) can be above unity because the useful energy output is higher than the Final energy input. For boilers this is a result of convention on the reporting of energy statistics (net heating value instead of gross), while for vapour compression it is because thermal energy is effectively extracted from the environment. Therefore, to balance Final and Useful energy consumption it is necessary to take into account both conversion losses and conversion gains. The latter are referred to as “ambient gains” and are calculated as the difference between the thermal Useful energy output and the Final energy input in Vapour compression devices.