Hydrogen as an energy currency, carrier and storage medium may be a key component of the solution to problems of global warming, poor air quality and dwindling reserves of liquid hydrocarbon fuels. Hydrogen is a flexible storage medium and it may be generated by the electrolysis of water. It is particularly advantageous if an electrolyser may be simply and efficiently coupled to a source of renewable electrical energy. This paper examines direct coupling of a 2kW PEM electrolyser to a matching solar PV source. A control system provides for disconnection when required and for shut down at night, simultaneously addressing the goals of minimum energy loss and maximum safety. The electrolyser is designed for fail safe operation with multiple levels of safety and operational redundancy.

The PV system is a 2kW array at RMIT University’s Bundoora East campus. The array comprises thirty 12V, 80W Solarex polycrystalline modules in a series-parallel configuration delivering 24V (nominal) at a peak current of around 70A.

The integrated system has operated for approximately 60 days over a 4-month period from September 2007 to January 2008. It has had many periods of unattended operation for multiple days, experiencing a weather ranging from hot and sunny (above 40ºC) to cool and cloudy.

The functionality of matched direct-coupled array and electrolyser has been successfully demonstrated. Approximately 50m3 (~45kg) of hydrogen has been generated at an efficiency which is calculated to be only a few percent less than the theoretical maximum assuming perfectly matched energy transfer at all times.