Simultaneity of green energy and hydrogen production: Analysing the dispatch of a grid-connected electrolyser

Hydrogen is a promising supplement in future energy systems with high penetration rates of renewable energy (RE) generation. As conversion technology between the two secondary energy carriers, hydrogen and electricity, particularly grid-connected electrolysers, have a role to play. During the market ramp-up, grid-connected electrolysers could cause unwanted side-effects through inducing additional CO2 emissions in the power sector. Since the reduction of CO2 constitutes the overall goal, a simultaneity obligation between RE generation and hydrogen production is discussed to prevent indirect emissions from an electrolyser's energy consumption. The paper presents a model framework including a mixed-integer linear program and a Markov chain Monte Carlo simulation for stochastic electricity prices to assess a grid-connected electrolyser's dispatch. Within a case study of the German electricity market, the effect of simultaneity on the dispatch is assessed. The results show that simultaneity reduces the CO2 emission intensity of hydrogen while constraining profits. The choice of the simultaneity interval length affects the electrolyser's average contribution margin from hydrogen production and the corresponding profit at risk, which results from fluctuating RE generation. Regulations aiming at the interface between hydrogen and electricity must consider the trade-off between economic viability, full load hours, and associated emissions of electricity-based hydrogen.