Design of a dynamic control system for standalone solar-hydrogen power generation

Solar-hydrogen systems employing a photovoltaic array and storage of surplus energy in the form of hydrogen are an attractive zero-emission and low-maintenance solution for remote area and other standalone power supplies to replace diesel and PV- battery systems. A number of experimental and demonstration solar-hydrogen systems have been constructed and tested, but little work has been done to date on an overall control unit for such systems. The present paper thus focuses on the design of a control unit for a solar-hydrogen system with hydrogen generation via a proton exchange membrane (PEM) electrolyser, compressed gas or metal-hydride hydrogen storage, and a PEM fuel cell. Particular emphasis is placed on the design of an integrated maximum power point tracker and load splitter that can dynamically supply power to meet the load and divert any surplus to operate the PEM electrolyser and produce hydrogen for storage. Two alternative algorithms for the execution of the load splitting function are outlined. Measurements of the typical variation of solar radiation over a very short time scale, together with typical household load variations, are used to suggest an appropriate unit time interval within which the system operates at selected optimal settings. The main components of a planned experimental program to measure the performance of the control unit for a small standalone solar PV-hydrogen system are presented.