PhD defense - Yannik Werner - Modeling Electrolyzers and Gas Networks for Integration with Power Systems

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The world must shift from fossil fuels to renewable energies to combat climate change. Wind turbines and photovoltaic cells can generate renewable electricity from wind and solar energy. Electrolyzers can produce hydrogen from renewable electricity to substitute natural gas. Hydrogen is envisioned to play a major role in decarbonizing the gas sector. Some governments consider building electrolyzers on
artificial islands - so-called energy islands - to produce hydrogen using offshore wind power out on the sea.

As the available wind and solar power potential varies over time, technologies providing flexibility to compensate for those fluctuations are needed. When there is excess renewable electricity, electrolyzers can produce hydrogen. If there is a renewable electricity shortage, gas-fired power plants can quickly adjust their power production. To be able to do that, the gas network must provide them with sufficient gas.

Nonlinear physics characterizes electrolyzers and gas flows in the pipelines. Capturing this nonlinearity in models is essential to ensure that the model results coincide with the physical behavior in practice. Depending on the application, the modeler should consider a different degree of technical and physical detail. This thesis identifies three modeling levels: component, system, and policy. One research direction is pursued on each level, leading to substantial scientific contributions. On the component level, this thesis proposes a new model to capture the nonlinear
relationship between the power consumption and the hydrogen production of the electrolyzer. A new framework for modeling gas flow physics is proposed on the system level, generalizing and enabling a comparison of various existing approaches in the literature. Additionally, the model results show that considering gas flow directions variable increases the flexibility of the gas network. On the policy level, an electricity market model is used to derive recommendations that may enhance the flexibility of electrolyzers on energy islands.

The proposed modeling approaches and policy recommendations can support the integration of electrolyzers and gas networks with power systems. The integration contributes to the flexibility potential needed to accommodate massively increasing electricity generation from wind and solar energy.