Abstract:The contribution of renewable energies to the reduction of the impact of fossil fuels sources and especially energy supply in remote areas has occupied a role more and more important during last decades. The estimation of renewable power plants performances by means of deterministic models is usually limited by the innate variability of the energy resources. The accuracy of energy production forecasting results may be inadequate. An accurate feasibility analysis requires taking into account the randomness of the primary resource operations and the effect of component failures in the energy production process. This paper treats a novel approach to the estimation of energy production in a real photovoltaic power plant by means of dynamic reliability analysis based on Stochastic Hybrid Fault Tree Automaton (SHyFTA). The comparison between real data, deterministic model and SHyFTA model confirm how the latter better estimate energy production than deterministic model.

Biomass energy conversion is a reliable way to produce energy and chemical products if compared with other renewable sources such as wind, solar and wave which have intermittent nature. Amongst different methods of converting biomass to energy, the thermo-chemical process of steam gasification is an outstanding way, since it enables a subsequent polygeneration process that can lead to production of heat, electricity, synthetic natural gas and synthetic chemicals such as methanol, Fischer-Tropsch diesel, gasoline and kerosene. The modelling of biomass gasification enables the optimization of the process designs, but it is a challenge due to its high complexity. Here, a new approach is used to simulate a 100 kW dual fluidized bed gasifier. Detailed pyrolysis modelling is a key factor of this approach and enables more accurate results. The results have been validated by experiments conducted with softwood pellets as fuel and fresh olivine sand as bed material. The impact of the gasifier temperature variation on the final product gas composition is measured in the experiments and implemented in the simulation to have a better insight on the pyrolysis process, the char heterogeneous reactions as well as the deviation from equilibrium of the water gas-shift reaction.

Grid-connected low voltage photovoltaic power plants cover most of the power capacity installed in Italy. They offer an important contribution to the power demand of the utilities connected but, due to the nature of the solar resource, the night-time consumption can be satisfied only withdrawing the energy by the national grid, at the price of the energy distributor. Thanks to the improvement of storage technologies, the installation of a system of battery looks like a promising solution by giving the possibility to increase auto-consumption dramatically. In this paper, a model-based approach to analyze and discuss the performance and the economic feasibility of grid-connected domestic photovoltaic power plants with a storage system is presented. Using as input to the model the historical series (2008–2017) of the main ambient variables, the proposed model, based on Stochastic Hybrid Fault Tree Automaton, allowed us to simulate and compare two alternative technical solutions characterized by different environmental conditions, in the north and in the south of Italy. The performances of these systems were compared and an economic analysis, addressing the convenience of the storage systems was carried out, considering the characteristic useful-life time, 20 years, of a photovoltaic power plant. To this end the Net Present Value and the payback time were evaluated, considering the main characteristics of the Italian market scenario.

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