What about the long term? Using experience curves to describe the energy-efficiency improvement for selected energy-intensive products in Germany

We analyse the long-term energy efficiency trends of selected energy-intensive production processes in Germany in the second half of the 20th century. The processes we consider are the pulp and paper industry, the production of crude steel, cement, and primary aluminium. Together they represent about 34 % of the energy consumption in the German industry. To analyse the time series, we use the experience curve approach, which is widely used for assessing the dynamics of specific costs for energy technologies, but has so far only rarely been applied to analyse energy-efficiency developments. We use the specific energy consumption as an indicator of the energy efficiency improvement and the cumulative production as an indicator of experience. The results show learning rates in the range of 3.5-9.5 % for the specific primary energy consumption, that is doubling the cumulative production volumes results in 3.5-9.5 % lower energy consumption. Using available forecasts for industrial production shows efficiency improvements of 4.0 % by 2020 and 6.9 % by 2035 compared to 2007 as the average across all processes considered. Further, the results reveal huge improvements in energy efficiency for the period after WW2 and a rather slow improvement in the last two decades for many processes. Energy efficiency has improved more for fuels than for electricity. In general, energy efficiency improved fast, when new processes entered the market as for example for electric steel and hardly improved for very old and mature processes like clinker burning or primary aluminium smelting. In order to improve the robustness of these first analyses and conclusions follow-up studies looking at other processes, products and industries and also countries are certainly necessary.