The subject of this paper is an economic analysis of a model of a stand alone energy system based only on a renewable source (solar irradiance) integrated with a system for the production of hydrogen. The purpose of this system is to supply the complete electric and part of the heat requests of a small residential user in a remote area (an isolated building in a valley of the Alps in Italy) during a complete year of operation without integration of a traditional energy system based on fossil fuels. The system analysed is composed of a PV array integrated with an electrolyser, with a tank where the hydrogen is stored as compressed gas and with a proton exchange membrane fuel cell. Such a system has no pollutant emissions and is environmentally friendly. A simulation program has been developed to design the system and to analyse the technical and economic performance during a complete year of operation. The economic analysis is developed using thermoeconomic analysis. This procedure joins some aspects of exergy analysis with some economic information, such as the fuel market costs and the investment and maintenance costs of the, components of the energy plant. Using this methodology, it is possible to obtain some information on the economic behaviour of the plant and to analyse in depth the process of cost formation of all system flows, in particular those of the final products. The thermoeconomic analysis can be performed to evaluate the different economic behaviour of the system in different operating conditions (e.g. during daylight hours or in evening hours). In this paper, the analysis has been effected considering a representative day for each month of operation and two significant hours (1:00 p.m. and 8:00 p.m.) in order to consider two opposite situations (with and without solar irradiance) with high energy demands by the user.
