Capacity optimization of a wind-photovoltaic-electrolysis-battery (WPEB) hybrid energy system for power and hydrogen generation

Abstract

Utility-scale (>10 MW) Wind-Photovoltaic-Electrolysis-Battery (WPEB) system is an emerging technology that adopts open loop “Power-to-H2” architecture for large-scale green hydrogen production. It applies to curtailment reduction in the area with abundant wind and solar energy resources. The traditional residential-scale (0–1 MW) or commercial/facility-scale (1–10 MW) WPEB systems usually adopt the close loop “Power-to-H2-to-Power” structure for power supply in the microgrid. The capacity optimization of the commercial-scale, residential-scale WPEB system have been studied extensively, but the researches for utility-scale WPEB system are rare. This work proposes a multi-constraints single objective capacity optimization method for the utility-scale WPEB system. The optimization objective is to minimize the levelized cost of electricity (LCOE) and the constraints of power balance, annual grid sales rate (AGSR), wind/PV/electrolysis station capacity are considered. The feasible domain is identified by the 8760-h production simulation and the gradient descent method is applied to search the optimal solution. The main conclusions are summarized below: (1) Increasing the wind-to-generation capacity ratio can reduce the LCOE, required grid sales capacity, and net generation curve fluctuation. (2) The lower and upper limits of the electrolysis station capacity are determined by the AGSR constraint and the LCOE target. (3) The battery bank time-shifts electricity to reduce the downtime of the electrolysis station. Thus, its power capacity should be no less than the minimum load ratio of the electrolysis station and the discharge duration greater than 1 h is preferred. Overall, this work provides a capacity optimization roadmap for the utility-scale WPEB system which plays a significant role in renewable electricity-based hydrogen production and curtailment reduction.