A software tool to support design and upgrade of energy production and storage systems

In the last years, the rise in cost of fuel and the introduction of incentives from European countries led to a growth of interest for home systems that can locally produce, store and manage electric energy. In this scenario, a correct sizing, with respect to the expected consumption, of the energy production and storage devices is a key element for keeping acceptable the cost of the system. Here, we propose and describe a software simulation tool that can be used in the system design phase in order to determine, in a given range, the values of nominal power of the energy production devices (photovoltaic panels) and the values of capacity of the storage devices (battery) that satisfy basic requirements about autonomy and selfconsumption. The designer can then choose among the various possible combinations of nominal power and battery capacity the one that better fits with other requirements, like e.g. that of minimizing the costs of components. The tool works by simulating energy production and flows over a given time period and under chosen external condition. Its structure basically consists of a Petri Net, in which energy production, consumption and flows are represented, in a quantized way, by the exchange of tokens. Such structure has the advantage of providing a simple, effective and intuitive way to describe the features and functionalities of the system that are of interest in the design phase. Behaviours that force autonomy and self-consumption are implemented by means of inhibitory arcs. Two series of simulations, with different discretization steps, are used in order to explore the performances of systems characterized by various combinations of nominal power and battery capacity in a range chosen by the designer. Combinations that do not satisfy specific design requirements about autonomy and self-consumption (expressed roughly as percentage of consumed energy that is locally produced and as percentage of produced energy that is locally consumed) are automatically discarded.