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District heating will play an important role in the transition towards climate-neutral heating. Various studies on modelling the energy system show that district heating and the related expansion of the networks can have different levels of importance. A main reason is that the costs for distribution grid expansion are not well or not at all considered and empirical evidence for a threshold for cost-effective distribution costs is missing in such studies. In this paper, we aim to improve empirical evidence allowing to improve the representation of future district heating expansion in energy systems models. For that, the current status of district heating is analysed in high spatial resolution for Germany. The results show that with the currently accepted average costs, a large range of the possible future market share of district heating for buildings between 17–52% is possible by 2050, with the parameters of the connection rate and the renovation rate of the building stock. We conclude that the district heating share could be increased by the factor of 2 to 5 in the future, proving the importance of climate-neutral district heating in the transition.

The measures needed to limit global warming pose a particular challenge to current fossil fuel exporters, who must not only decarbonise their local energy systems, but also compensate for the expected decline in fossil fuel revenues. One possibility is seen in the export of green hydrogen. Using Algeria as a case study, this paper analyses how different levels of ambition in hydrogen exports, energy efficiency and fuel switching affect the cost-optimal expansion of the power sector for a given overall emissions reduction path. Despite falling costs for photovoltaics and wind turbines, the results indicate that in countries with very low natural gas prices, such as Algeria, a fully renewable electricity system by 2050 is unlikely without appropriate policy measures. The expansion of renewable energy should therefore start early, given the high annual growth rates required, which will be reinforced by additional green hydrogen exports. In parallel, energy efficiency is a key factor as it directly mitigates CO2 emissions from fossil fuels and reduces domestic electricity demand, which could instead be used for hydrogen production. Integrating electrolysers into the power system could potentially help to reduce specific costs through load shifting. Overall, it seems advisable to analyse hydrogen exports together with local decarbonisation in order to better understand their interactions and to reduce emissions as efficiently as possible. These results and the methodology could be transferred to other countries that want to become green hydrogen exporters in the future and are therefore a useful addition for researchers and policy makers.

The global energy system is transitioning to renewable energy to phase out fossil fuels and combat climate change. Large amounts of PV and wind capacity will be added and the whole transport system will change to electric vehicles to reach the global goals of becoming climate neutral. A lot of additional raw materials will be needed for all technologies relevant for these transitions. Some literature even suggests that this increased demand will lead to raw material bottlenecks in the next decades. Power electronics is a crucial enabling technology for the transition but is often overlooked in research. While the material demand of other technologies is well examined, there are no indepth studies regarding the material demand of power electronics. Considering the important role power electronics play in the success of the transition, this is a research gap that needs to be filled. Therefore, this thesis was conducted to analyse the role of power electronics for the raw material demand of the energy transition. The power electronics devices necessary for energy generation technologies, energy storage and electric vehicles were considered. The innovative approach of this thesis included determining one representative device and its material demand for each technology. Based on the results of analysing six representative devices, a scenario analysis on both a global and a German level was realised. This approach determined the future material demand. While doing this, the most important technological developments in power electronics and their potential impact on material demand were identified. This analysis shows that the material demand for power electronics for the energy transition will multiply in the coming years, regardless of which scenario is considered. It will lead to an immense demand for many different materials, especially copper, aluminium, and iron. Electric vehicles are projected to have the highest power electronics material demand among the technolo

Scenario planning provides stakeholders with a tool to understand the future. Through the depiction of different possible futures, it informs decision-making and challenges how we think about future developments. In Germany, a series of studies modeled various pathways to climate neutrality by 2045/50. Although giving valuable insights, they fall short of explaining how they arrived at the scenarios they modeled. This thesis aims to address this gap. It focuses on the decarbonization of the industry, which is one of the key challenges on the path to achieve climate neutrality by 2045, as targeted by the German government. It does so by applying a systems approach, which aims to explain other developments that are linked to industry as well. In addition to techno-economic factors, qualitative developments such as societal trends, corporate strategies, the political framework, and others are also taken into account. To achieve this, the thesis utilizes a cross-impact balancing (CIB) technique. CIB allows for the construction of consistent scenarios by creating a matrix of interactions between different developments. Through a structured expert elicitation, these interactions are assessed one by one on whether they promote or restrict each other. For the expert elicitation, essays portray the possible course that each of the individual developments considered could take. Then, the matrix is analyzed with software. That way, sixteen scenarios are developed, which are consistent within the CIB framework. Four of these are described in more detail through storylines: one scenario where developments occur late and decarbonization seems at risk, one where PtX is the dominant energy carrier, one where a quick scale-up of technologies makes decarbonization possible, and one where societal change and the establishment of a circular economy leads to a reduction in demand. Furthermore, the impact of the different developments upon each other is assessed. Because of how the metho