Flexible operation space of hydro–hydrogen–based hybrid power systems

Schedulable hydropower and hydrogen power provide essential flexibility to mitigate variability of renewables such as wind and photovoltaic power. Previous research has focused on the flexibility of power systems utilizing a single adjustable source (e.g., hydropower). However, joint flexibility of combining adjustable hydropower and hydrogen power has rarely been explored simultaneously. This study aims to establish a joint flexible operation framework for hydro–hydrogen–wind–photovoltaic hybrid power systems. Initially, the forecast uncertainties are quantified regarding the inflow as well as the combined wind and photovoltaic power. Subsequently, a tri-objective optimization model is formulated to maximize operation benefits while enhancing joint flexibility in managing water levels and allocating power to hydrogen production, deriving the flexible operation space. Finally, the operation space's effectiveness is validated by stochastic simulation. Results from a case study using China's Ertan hydro–hydrogen–wind–photovoltaic hybrid power system indicated that the minimum operation benefit derived from the decisions within the operation space decreased with increasing flexibilities of both the water level and power allocation to hydrogen production. The benefit loss (i.e., the gap between the theoretical maximum and actual benefits) decreased by 26.53 %, from 3.77 to 2.77 million CNY, through maintaining operation decisions within the flexible space during a hypothetical earthquake emergency. This was achieved by adjusting 1.79 % release and 10.71 % hydrogen production power. The proposed method provides implications of jointly utilizing flexibilities of adjustable power sources to decrease economic loss. This research contributes to reducing energy emissions by improving energy use efficiency of power systems.