Modeling and Control of Power-to-Hydrogen Technology for Renewables Integration

The transition to green energy, driven primarily by renewables, is imperative as fossil fuels deplete and their environmental impact worsens. However, integrating renewables effectively into existing energy systems is challenging due to their intermittent and fluctuating nature. The emergence of power-to-hydrogen (PtH₂) technologies offers a promising pathway to efficiently facilitate renewables integration from a cross-sectoral perspective. To this end, it is essential to understand the principles of PtH₂ technologies and investigate their role in accelerating the integration of renewable energy sources.
The main objective of the thesis is to investigate the modeling and control aspects of PtH₂ technologies in the context of renewable energy systems (RENSs). Drawing insights from seven papers, the thesis seeks to answer the overarching question: How can development of advanced models and control enable cost-effective PtH₂ solutions facilitating the integration of renewable energy sources in complex energy systems? This question is further addressed through in-depth investigations of four specific research questions: (i) How can PtH2 models be developed to holistically embody the full sense of multiscale and multi-physical attributes, meeting model requirements for their control purposes in RENSs? (ii) How can the synergy between PtH₂ systems and other assets within renewable hydrogen hubs be optimized to ensure system stability in the presence of fluctuating renewables and grid disturbances? (iii) How can cross-sectoral energy management of PtH₂ systems be strategically optimized to maximize their added value? (iv) How can the potential grid frequency services of PtH2 systems be efficiently quantified, harnessed and strategically aggregated to ensure a stable system frequency while minimizing operational costs?
After the introduction given in Chapter 1, an integrated modeling framework for PtH₂ systems is developed that can handle different scales and physical domains, as detailed in Chapter 2. These models embody the multi-physics of PtH₂ systems from high-fidelity cell-level characteristics up to comprehensive system-level representations, also covering the electrical, electrochemical, thermal, and the gas domain. The framework is validated and offers a holistic understanding of the fundamental PtH₂ principles while at the same time offering high-fidelity insight into e.g. polarization characteristics and complex electricity-thermal-hydrogen interaction dynamics. Moreover, model applications are discussed to provide insights into model demands in implementing stability-oriented control and strategic scheduling in diverse renewables-integrated scenarios.
Expanding upon the developed models, the attention is directed towards the real-world utilization of PtH₂ systems across different scenarios that involve the integration of renewable energy sources. Particular attention is given to developing advanced control strategies for optimizing the operation of RENSs as detailed in the body of the thesis. The advanced control methods involve stability-oriented dynamic control at second-level timeframes and optimal scheduling at hour-level timeframes. The studies validate the effectiveness of the developed dynamic control strategies in achieving two significant outcomes as shown in Chapter 3 and Chapter 4 respectively: (i) cost-effectively strengthening the grid integration of wind-hydrogen-storage systems, making them more resilient to grid voltage sag and wind fluctuations; and (ii) enabling PtH₂ systems to provide frequency regulation, thereby enhancing the frequency stability of renewable-dominated and low inertia power systems.
In addition, the developed scheduling methods address a range of operation objectives of PtH2-integrated multi-energy systems in Chapter 5 and Chapter 6. In those two chapters the operational constraints of PtH₂ systems are accounted for as well as their produced added values including profits from waste heat recovery, resilience enhancement, and frequency support. It is found that these scheduling methods can effectively achieve both economic and resilient operational objectives for renewables-integrated multi-energy systems, meanwhile ensuring system frequency security in low-inertia scenarios. Moreover, the thorough consideration of operational specifics related to PtH₂ systems enhances their adherence to PtH2 security constraints, thereby improving their practical feasibility.
Finally, key findings regarding the modeling and control of PtH₂ systems is summarized in Chapter 7. Promising avenues are put forth for future research initiatives building upon the modeling framework laid out in this thesis. These prospective directions broaden the thesis’s scope to encompass the following areas: (i) exploring synergies among multiple modules within single PtH₂ systems; (ii) advancing process modeling and control of PtH₂ systems; (iii) studying the hybridization of diverse PtH₂ technologies; and (iv) analyzing stability-oriented interaction within renewable power systems. These areas aim at accelerating the large-scale and sustainable development of PtH₂ technologies for cost-effective and reliable renewables integration.