Energy management control strategies addressing the rSOC degradation phenomena in a polygeneration microgrid

Economically competitive long-term energy provision and performance stability are becoming increasingly strategic for the upcoming energy market. Despite hydrogen-based technologies representing a viable way for the aforementioned targets, such systems are affected by performance reduction over time. This paper is aimed at presenting energy management mitigation policies for a reversible solid oxide-based (rSOC) polygeneration microgrid. Particularly, interest has been paid towards the rSOC degradation phenomena and its mitigation by applying strategies allowing meeting target performance and satisfying economics. In a multilevel framework, the rSOC degradation mitigation has been pursued proposing two central-level strategies, namely Grid support (GS) and Limited Grid support (LGS), which act between the power split targets coming from the supervisory level and working set points actuated by the low-level controllers. The former aims at compensating for the energy gap caused by degradation relying on external contributions: power grid network and boilers. Alike, the goal of the latter is to keep the rSOC turned on as much as possible, therefore, complying with the energy management goals given by supervisory level. The state of charge of the hydrogen storage tank has been chosen as a metric to best show the results obtained implementing the mitigation strategies, as it directly displays the rSOC active management and boundaries applied on the storage systems. Considering a 3 years scenario, the LGS strategy in comparison to the GS one has resulted to be more effective concerning: costs, microgrid self-sufficiency, reliability and overall robustness. Quantitatively, for the LGS strategy, considering degradation degrees in the range 0.25–1 %/kh, relative additional integration costs with respect to the case unaffected by degradation are seen to be in the range 30–105 %.