Dynamic performance assessment of a residential building-integrated cogeneration system under different boundary conditions. Part I: energy analysis

This work examines the energy performance of a residential building-integrated micro-cogeneration system during the winter season by means of a whole building simulation software; a 6.0 kWel natural gas-fuelled internal combustion engine-based cogeneration unit was coupled with a multi-family house composed of three floors, compliant with the thermal transmittances of both walls and windows equated to the threshold values suggested by the Italian Law. The main purpose of the paper is to compare the proposed system with a conventional system composed of a natural gas-fired boiler (for thermal energy production) and a power plant mix connected to the Italian central grid (for electric energy production) in order to assess the potential energy saving under various operating scenarios. The simulations were performed by considering the multi-family house located into four different Italian cities (Palermo, Napoli, Roma and Milano) representative of different climatic regions of Italy in order to estimate the influence of climatic conditions; a parametric analysis was also performed with the aim to evaluate the sensitivity of the energy flows when varying the volume of the combined storage tank; taking into consideration that the economic viability of the cogeneration unit strongly depends also on the value of the co-produced electricity, the system performance was also evaluated by considering two different electric demand profiles (with and without the electric consumption associated to the overnight charging of an electric vehicle); the operation of the microcogeneration device was estimated under both electric and thermal load-following control strategies. The analyses showed that, in comparison to the conventional system, the proposed system allows for a relevant reduction of primary energy consumption under thermal load-following logic; significant effects of climatic conditions, tank volume, as well as electric demand profile on the simulation results were highlighted. In the companion paper (Part II: Environmental and economic analyses) the performance of the proposed system was analyzed and compared with those of the reference system from both environmental and economic point of views.