Hybrid PV-Diesel power generator: design criteria and preliminary performance analysis

In recent times a fast growing role in distributed power generation is played by Renewable Energy Sources. Among them the Photovoltaic source (PV) is the most promising because of widespread availability of solar energy, easy installation and low plant maintenance costs. As almost all renewable sources, PV energy is characterized by discontinuous availability due either to normal day-night cycle and to random atmospheric conditions. The integration of the PV generators with other energy power systems, also based on conventional energy source is more and more suggested whenever users need uninterrupted power and no electric public distribution network (or only an unreliable network) is available. Hybrid PV-Diesel power generation results particularly attractive to supply electrical energy in remote areas or to sustain weak grid. For this reason, ENEA, Italian Agency for New Technology, Energy and Environment, has realized in the Test Site of Monte Aquilone near Manfredonia, in cooperation with Elettronica Santerno SpA, a prototype of PV-Diesel plant. The Power Generator is based both on a PV source and an asynchronous generator driven by the diesel engine. The internal energy storage is assured by lead-acid batteries. The system management is performed by means of modern high-efficiency solid state switching converters. Particular relevance is represented by the innovative embedded Energy Dispatcher Controller which assures uninterrupted power generation and optimum renewable resource exploitation by minimising operations of endothermic generator. The Controller not only performs the Energy Dispatching but also takes care of system management functions such as automatic reminders of periodic maintenance tasks, automatic lubricant replacements, fuel management and recording of historic energy production and consumption data. System maintenance is simplified so that the Hybrid Power Generator can be operated also by non specialised personnel. In the paper technical description of the system components and functions and energy dispatcher politics are presented. Experimental test results carried out with a medium sized system (120kW output peak power, 45kW diesel engine) are reported. Experimental data show the effectiveness of the Energy Manager. Finally, the paper deals with how a Virtual Power Distribution System can be realized using several Hybrid Power Generators remotely controlled through PSTN or Wireless Phone Service (GSM or GPRS). A network of power management nodes capable of supplying electric power anywhere in the territory can be virtually connected to a central management centre from which energy billing, production monitoring and remote maintenance can be assured.