Sviluppo di un modello per il dimensionamento ottimizzato di sistemi multienergia per il soddisfacimento dei fabbisogni energetici dell'edificio

Abstract

In this thesis is developed a model for energy analysis and economic feasibility of multienergy plant for fulfillment the electric, thermal and cooling demand of the civilian building. The aim of the model is the optimal allocation of energy requirements of a building, by using renewable energy systems, partially renewable energy systems, systems powered by natural gas and by electricity. The analysis is based on the time series, with the possibility to set the time-step considered. The simulation takes into account the variability of the performance of the energy systems according to the energy demands and to the external environmental conditions. The performance of the energy systems are modelled through a systemic approach. Solar photovoltaic panels, solar thermal collectors, CHP, absorption chillers, geothermal heat pumps and air heat pumps both reversible, are modelled. The heat produced by the solar thermal collectors and by the CHP, if not used simultaneously is stored within the thermal tank. Condensing boilers and electric chillers are take into account as auxiliary systems. The systems described may be present all at the same time or it may be considered only some of them. The control logic of the systems is thermal-follows; heat dissipation is not allowed. According to the kind and to the number of unknown variables, the model is able to operate in two distinct ways: direct calculation and optimization mode. In the first case, known the size of the systems, the annual operating of multienergy plant is simulated; the energy production of the different systems, the fuel used, the electricity take from the grid and sent to the grid during the twenty-four hours of the day are obtain as results. The efficiencies of the systems are expressed as a function of load and of external environmental conditions (e.g. outside temperature). Otherwise, if the size of the systems are unknowns, the optimal sizing of the different technology composing the multisource energy plant is searched by using a genetic algorithm, with the goal of minimizing a specific objective function. The model also provides financial results: notice the specific cost of the various systems, it is estimated the investment cost of the plant; the model also derived the annual cost of operation of the multienergy plant taking into account the current national incentives (e.g. V Conto Energia, Certificati Bianchi, Conto Termico, etc. ). Energy and financial indices are proposed for the evaluating of multienergy system and for its comparison with conventional systems. The model has been applied at two case studies in order to obtain useful information and guidelines for the design of multienergy systems.