European Journal of Scientific Research - EuroJournals

European Journal of Scientific Research
ISSN 1450-216X Vol.20 No.2 (2008), pp.384-396
© EuroJournals Publishing, Inc. 2008
http://www.eurojournals.com/ejsr.htm
Photovoltaic-Stand-Alone Hydrogen System
R.Y. Tamakloe
Department of Physics
Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
K. Singh
Department of Physics
Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
Abstract
A photovoltaic system consists of an array, a storage medium and elements for
power conditioning. Many photovoltaic systems operate in a stand-alone mode and the total
energy demand is met by the output of the photovoltaic array. The output of the
photovoltaic system fluctuates and is unpredictable for many applications making some
forms of energy storage or backup system necessary. The role of storage medium is to store
the excess energy produced by the photovoltaic array, to absorb momentary power peaks
and to supply energy during sunless periods or during night. One of the storage modes is
the use of electrochemical techniques, with batteries and water electrolysis as the most
important examples. In this paper, we report the optimal design for a stand-alone hydrogen
system with the volume of hydrogen produced against current as regards the concentration
of electrolysis cell. Operating characteristics of a small capacity solar hydrogen system
have been determined and also demonstrated that the I-V characteristics of the batteryphotovoltaic
module and electrolysis cell are influenced by variations in the concentration
of the electrolysis cell, which in turn determines the amount of current that flows through
it. A 50W photovoltaic panel rated as 17.4V, 2.87A yielded a maximum volume of about
8.6ml per minute for 1.0M cell concentration. Numerical simulation was used to compare
the experimental results and also the possibility of increasing the cost-effective yield of
hydrogen.
Introduction
Solar hydrogen is one of the most interesting options for the sustainable energy future relating to the
increasing concerns of the environmental effects of current energy production and will accelerate the
transition into renewable energy systems. The production of hydrogen from the decomposition of water
(H2O) using solar energy as the driving force has been a main focus of many scientists and engineers
since the early 1970s when Fujishima and Honda [1] reported the production of hydrogen and oxygen
in a photoelectrochemical hydrogen cell using a titanium dioxide (TiO2) electrode exposed with near
ultraviolet light. Since then there has been an explosion of scientific interest and experiments in this
direction. The energy required to produce hydrogen via electrolysis (assuming 1.2 V) is about 32. kWhr/kg.
For 1 mole (2g) of hydrogen the energy is about 0.0660 kW-hr/mole. The power in this case is
the voltage required to split water into hydrogen and oxygen (1.2 V at 25°C). The rate is the current
flow and relates directly to how fast hydrogen is produced. Time, of course, is how long the reaction
runs. It turns out that voltage and current flow are interrelated. To run the water splitting reaction at a