Optimisation of Photovoltaic-Powered Electrolysis for Hydrogen Production for a Remote Area in Libya

Abstract

Hydrogen is a potential future energy storage medium to supplement a variety of renewable energy sources. It can be regarded as an environmentally-friendly fuel, especially when it is extracted from water using electricity obtained from solar panels or wind turbines. The focus in this thesis is on solar energy, and the theoretical background (i.e., PSCAD computer simulation) and experimental work related to a water-splitting, hydrogen-production system are presented. The hydrogen production system was powered by a photovoltaic (PV) array using a proton exchange membrane (PEM) electrolyser. The PV array and PEM electrolyser display an inherently non-linear current-voltage relationship that requires optimal matching of maximum operating power. Optimal matching between the PV system and the electrolyser is essential to maximise the transfer of electrical energy and the rate of hydrogen production. A DC/DC converter is used for power matching by shifting the PEM electrolyser I-V curve as closely as possible toward the maximum power the PV can deliver. By taking advantage of the I-V characteristics of the electrolyser (i.e., the DC/DC converter output voltage is essentially constant whereas the current increases dramatically), we demonstrated experimentally and in simulations that the hydrogen production of the PV-electrolyser system can be optimised by adjusting the duty cycle generated by the pulse-width modulation (PWM) circuit. The strategy used was to fix the duty cycle at the ratio of the PV maximum power voltage to the electrolyser operating voltage. A stand-alone PV energy system, using hydrogen as the storage medium, was designed. The system would be suitable for providing power for a family's house located in a remote area in the Libyan Sahara.

Date of Award	31 Dec 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Peter Stansby (Supervisor)