Sustainability analysis and Power-to-Methane mathematical model comparison of Hybrid Renewable Energy System Day-Ahead scheduling

Sustainability is a topic that is becoming more and more important in energy production systems. Due to new energy policies, hydrogen is receiving increasing attention as a carbon-free energy carrier embedded in hybrid renewable energy systems (HRES). This paper presents a sustainability analysis of the HRES operation involving electrolytic hydrogen production and conversion to methane through Power-to-Methane (PtM). The analysis is based on day-ahead (DA) scheduling to accomplish the minimum HRES operating cost by comparing two PtM models: A simple rigid model with constant input/output efficiency without hydrogen storage and a linearised electrolyser and methane model with hydrogen storage. The subsequent analysis is conducted by adding heat and gas accumulators in the linearised PtM model to evaluate the added flexibility of these components. Based on the optimal DA programming solution, the three PtM representations are compared based on their respective operating costs and carbon dioxide emissions. The outcomes show that hydrogen into the HRES via a PtM process is not a direct sign of sustainability and that the environmental impact depends on the electricity source provided by the electrolyser. Therefore, this paper highlights that the growth of RES and the integration of PtM should go in synergy and deducting that a more accurate model is required to understand the potential of PtM.