Data results and operational experience with a solar hydrogen system

A solar hydrogen system is presented able to provide uninterrupted 200 We power to an isolated application. It is composed of a photovoltaic generator, a battery set, an electrolyser, a metal-hydride system for hydrogen storage and a fuel cell. Batteries are charged with the photovoltaic array and the fuel cell, and discharged with the electrolyser and the application load. The fuel cell switches on when the state of charge of the batteries is low, until they are recovered to a predetermined level. The electrolyser produces H2 at 30 bar, enough to feed directly the metal hydrides, avoiding pressurization steps. Metal hydrides work under pressure control in the temperature range 0-40 °C. Kinetics of absorption-desorption of hydrogen is observed as an important limiting aspect for this kind of storage. The system is able to convert about 6-7% of total solar energy irradiated in 1 year. Results and evaluation after 1-year operation are shown. Energy management is found to be a critical issue to improve the behavior of the system.