Unitized Regenerative Fuel Cells for Stand-Alone Photovoltaic Generation Systems

Photovoltaic (PV) stand-alone applications are able to provide electricity to isolated loads in remote areas and they are installed particularly where grid extensions would be uneconomical. However, the limitation in power availability of PV systems due to the variability of solar radiation calls for the use of storage systems in order to supply loads with adequate reliability levels. The storage systems have to store a great amount of energy to be maintained for quite long time periods with small losses. This is quite difficult to achieved by using electrochemical batteries and the use of hydrogen in regenerative fuel cells as a means for energy storage can represent a solution to overcome to achieve the aforesaid goals. This paper deals with the use of Unitized Regenerative Fuel Cells (URFC) in the realization of stand-alone PV generation systems. The study of the generation system with solar hydrogen storage will be carried out using analytical models to represent the efficiency of each component in order to assess the capability of the generation system of supplying its load with an adequate reliability level. In this perspective, the comparison between different storage technologies such as Regenerative Fuel Cells (RFC) and Unitized Regenerative Fuel Cells will be presented taking as reference the performance of a storage system based on electrochemical batteries.