Influence of actual component characteristics on the optimal energy mix of a photovoltaic-wind-diesel hybrid system for a remote off-grid application

Hybrid energy systems are an interesting solution for the electrification of remote, off-grid users, which usually are obligated to satisfy their electricity demand by means of quite old technologies, like for example diesel generators. An energy mix including also renewable energy sources (such as wind and PV) would lead to a reduction of supply costs and is therefore being increasingly appreciated. In the present study, a sizing strategy was developed based on a long-term energy production cost analysis, able to predict the optimum configuration of a hybrid PV-wind-diesel stand-alone system. With respect to conventional practical design approaches already available in the literature, a more realistic description of the problem was here provided, since the present analysis relies in the use of actual machines data, realistic system constraints and cost functions, which led to the identification of some trends that are usually neglected by the optimization processes using continuous variables for the power outputs of renewable energy sources. The approach was tested on an isolated mountain chalet in Italian Alps. The hybrid system was optimized based on the maximum long-term saving with respect to a conventional diesel engine configuration. The results for this case study showed that the optimal solution was not that including the maximum allowed contribution from renewables, highlighting the existence of an optimized energy mix between the three sources. Accumulation batteries were also able to induce a reduction of both the fuel consumption and the engine transitory usage. According to the present results, a properly sized hybrid system could provide notable money and pollution savings for a remote consumer with respect to a diesel-only configuration.