Low power hybrid fuel cells and photovoltaic systems for stand alone applications

During the last few years, the growing energy demand in the telecommunication sector and increasing care for safety and reliability of energy production systems have driven the development of integrated systems, using innovative power production processes. A particular interest has led to the possibility of producing energy in a stand alone configuration through the use of photovoltaic panels. This type of application still has some difficulties in storing produced energy since there isn´t an alternative possibility to put energy in the electric grid. The proposed solution foresees the reduction of the use of the traditional batteries, replacing them with a system based on production and accumulation of hydrogen and on the reuse of hydrogen in a fuel cell system. The choice was focused on fuel cells system, 2000 W power, working at 48 VDC or 220 VAC with hydrogen-featuring a high purity level, and air taken from the surrounding environment. For the hydrogen storage, metal hydride reservoirs have been used, containing up to 1000 NI at very low pressure (up to 10 bars). The choice to manufacture small size power systems simplifies some issues related to the management of thermal flows and humidification of membranes so their use at a demonstration scale becomes immediately available. The purpose of this article is to provide a detailed description of the technical specifications adopted as a base for system design and to show the flexibility using this system. A special focus is assigned to hydrogen storage technology in metal hydride reservoirs, and to the techniques adopted to facilitate desorption during system operation. Finally, an analysis of the costs of installation and operation of the entire system is introduced, underlining the components that introduce great margins of decreasing in case of mass production.