## 2 Materials and Methods
### Scenario Development
#### 2.2.2 Parameter Selection  
The implementation of the scenarios is based on the individual selection of the parameters efficiency increase and energy carrier penetration rate. The number of individually selected parameters is (8) in the _base_ scenario and increases to (53) in the _efficiency_ and _transition_ scenario. The parameters were selected individually by sector, useful energy category and in some cases also depending on the federal state. The individually selected parameters are described in the following. Efficiency increase: The reduction of energy consumption is caused by process optimization (e.g., energy cascades, sector coupling, digitalization, flexibilization) and technology-specific energy efficiency improvements (determined by technologies itself, e.g., higher fuel utilization rates) which is considered as efficiency increase in this work. The efficiency increase is inserted in the calculations as a percentage. For instance, 10% means that the FEC in the scenario decreases by 10% compared to the _status quo_. Depending on the sector and useful energy category, individual values are chosen based on literature references (e.g., [32; 33; 34; 35; 36; 37; 38]) and expert inputs through the participatory stakeholder process. In general, they are chosen in the range of 2-10% for thermal appliances. For example, only a small energy efficiency improvement of 2% is assumed for the _iron and steel_ industry, as steelmaking processes like the current BF-BOF route are already well optimized and efficiency potentials are largely tapped. However, in the nonenergy-intensive sectors, energy costs usually play a subordinate role. Therefore, the focus on energy reduction is usually lower, and thus higher efficiency potentials of around 10% are expected. Details for single values can be seen in the _IndustRiES_ study. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Assumptions // Scenario** & **Base** & **Efficiency** & **Transition** \\ \hline Starting point & _Status quo_ (refers to 2019) & _Base_ scenario & _Efficiency_ scenario \\ \hline \multirow{3}{*}{Thermal applications} & Low temperature by heat pumps (HP); CHPs unaltered & Steam generation and industrial furnaces (especially drying) partly by HP; CHPs unaltered & Higher penetration of HP (replace steam generation up to 160 \({}^{\circ}\)C); CHPs only for closed material cycles (e.g., pulp) \\ \hline \multirow{3}{*}{Key aspects} & Fuel switch to renewables (biogenic/electrical energy); Electrification of fossil stationary engines & Process efficiency (value determined for every sector and useful energy category individually) & Biogenic and combustible waste mainly for high temperature applications \\ \hline Iron and steel production & Coal and coke as well as blast furnace gas and coke oven gas & \\ \cline{1-1}  & & remain without changes due to process & Direct reduction with hydrogen \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of the storylines of the three defined scenarios (detailed assumptions are described in the _IndustRiES_ study [10]). Fossil fuel switch to biogenic and electrical energy: The parameter \"penetration rate\" is used when fossil fuels are substituted by renewable energy sources. It shall determine the type and share of the new renewable energy carriers. Hence, it indicates which share of the replaced amount is to be obtained from biogenic and which share from electrical energy. COP (coefficient of performance): Wherever possible, low-temperature applications (up to 160 \({}^{\circ}\)C) [39] are assumed to be covered by HPs. For all sectors and the respective useful energy category, the specific temperature requirements, determined in the literature research, are considered. This results in individual COPs ranging from 1.9 to 3.8. A COP of 1 is equivalent to pure electrification (100% electrical energy and no ambient heat used). The COPs are used to calculate the respective proportion of ambient heat required by the HP as the heat source.