**7. Conclusions**

The investigations in this paper show the significant potential of reducing *CO*2,*<sup>e</sup>* emissions in industrial facilities. Especially, the combination of biomass boilers and steam accumulator leads to an adequate ratio of *CO*2,*<sup>e</sup>* emissions reduction and steam production costs. Due to an expected future increase in the volatility of the power supply system, the characteristics of batch processes, start-up times and partial load are of crucial importance when planning a steam supply system. In contrast to previous research work, an annual dynamic simulation model was developed which takes these characteristics as well as a variety of new technologies into account. It was applied to a practical case study which demonstrates the complex relationships of steam supply systems in batch processes.

The steam supply in industrial plant systems is defined by their steam demand load profile. The results from this work cannot be transferred directly to any other case. So, a detailed investigation of various steam demand situations should be considered to transfer this results into other concepts. Similar results are expected for other industries, that is, dairy and galvanic, with a discontinuous steam demand and steam temperatures below 175 °C. Before changing the steam supply, a substitution of the steam demand by hot water processes should be analysed. This increases the integration potential of renewable energies and leads to higher *CO*2,*<sup>e</sup>* emission reductions.

Since energy cost increase and the *CO*2,*<sup>e</sup>* emission reduction are strongly dependent on the demand profile, the optimum design size for each individual utility must be determined. For the detailed evaluation and analysis of the transmission of energy supply sector in accordance with load management of steam processes, it is necessary to investigate technology combinations such as electrode boilers and micro gas turbines in future research. These could bring further advantages, especially regarding load management and grid stabilisation. Due to the inertia of the biomass boiler, fuel cell, solar thermal system and heat pump, these technologies do not show any potential for grid stabilisation. Soon, concepts of the fuel cell will become more attractive. Due to the strong development and research in this area, significantly decreasing investment costs and increasing efficiencies are predicted until 2030.

**Author Contributions:** Conceptualization, R.-H.H.; methodology, R.-H.H.; software, J.S.; validation, J.S., A.O.; formal analysis, J.-P.S. and M.S.; writing—original draft preparation, R.-H.H.; writing—review and editing, J.-P.S.; visualization, R.-H.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.

*Energies* **2020**, *13*, 2532
