Optimal multi-stack scheduling strategy for large-scale electrolysis: Integration with renewable energy and multi-market electricity

• Optimal techno-economic dispatch model of a multi-stack hydrogen production system. • Integration of a photovoltaic on-site PPA and a wind off-site PPA. • A wind-solar mix optimizes electrolysis and minimizes surplus losses. • Practical insights for real-world hydrogen production projects are provided. The production of renewable hydrogen through the electrolysis of water has grown with the advancement of renewable energies. Power purchase agreements (PPAs) are essential to ensure a steady and affordable supply of renewable energy at hydrogen production plants, allowing green hydrogen to be truly sustainable and competitive in the energy market. The aim of this paper is to propose an optimal hourly techno-economic dispatch model of a multi-stack hydrogen production system with two PPAs, photovoltaic (on-site) and wind (off-site) to meet hydrogen production in the defined calculation window and minimize operating costs. The model allows purchasing energy in the wholesale market if the PPAs do not meet all the hydrogen demand and selling surpluses when the energy purchased through PPAs exceeds the demand of the electrolysis plant. A mixed-integer nonlinear programming model is formulated to optimize the technical and economic management of the proposed system. The problem is applied to a Spanish case where pioneering projects are being carried out through the provision of PPAs. The increase in wind PPA capacity enables a significant reduction in energy imports from the grid, with decreases ranging from roughly 50% to 80% and a higher profitability. It is essential to achieve a balanced wind-solar mix to ensure efficient electrolysis demand coverage and reduce export losses.