Extended power to hydrogen operations for enhanced grid flexibility in low carbon systems

Abstract

Power-to-hydrogen (P2H) systems are increasingly recognized as a promising solution to expedite the integration of Renewable Energy (RE) in various energy sectors. P2H in Hydrogen Consuming Industries (HCIs) can serve hydrogen demands and the much-needed flexibility for power system operations. However, consideration of these systems for significant industrial and power sector use cases requires modelling fidelities for exact operational and economic reflections. P2H operational modelling for flexibility focuses on excess renewable energy evacuation and storage only while often oversimplifying their models by using constant efficiency models or neglecting specific Hydrogen Electrolyzer (HE) overvoltage components. Under variable operations and downstream HCI demands, this can lead to inaccurate assessments, undermining existing flexibility quantum from HCIs. Another prevalent issue with P2H adoption is its costs, which are directly linked with P2H operating ranges. These systems are presently modelled with constrained operations, leading to increased costs and limited ability to provide grid services. Therefore, appropriate modelling of HCIs considering P2H device working characteristics and its inherent flexibilities is essential. It can allow cost-effective operations and the exchange of accurate flexible margins with electrical grids. In this regard, this work proposes a comprehensive extended electro-chemical HE model for HCIs allowing high current density working through the extended operation of P2H. The considered model inherits intrinsic working characteristics of electrolyser operation, i.e., variable current, nonlinear efficiency, and loading, to cater to the hydrogen demands of HCI. The effect of high current density operations is elucidated through device operations under reaction kinetics. The results highlight that the proposed model integrated with the electrical grid provides actual operational costs and flexibility margins. A comparison of various modelling approaches and their effect on adjustable margins demonstrates a considerable difference in P2H loading, working efficiency, operating costs, and adjustable margins with the proposed model.