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Energy efficiency is a key target of the European Union policy. The “Europe 2020 strategy” quantitative targets account an increase by 20% of the energy efficiency by the end of 2020. The attention to power sources optimization and energy waste reduction leads European Countries to develop subsidy strategies to drive the energy market towards efficiency enhancement. According to this trend, energy efficiency of residential buildings has significantly grown in Italy in the last years. Combined production of electric and thermal power is a notable example of efficiency enhancement awarded by the CAR ( Cogenerazione ad Alto Rendimento ) Italian subsidies system. In these circumstances, the optimization of the ensemble between power generators and thermal storages becomes crucial to satisfy in an efficient way thermal power requirement independently from electric power production. The purpose of this paper is to find the optimal power plant design of power generators and thermal storages in order to minimize daily management costs and environmental impact. The power plant layout in analysis consists in a micro-CHP (Combined Heat and Power) and an absorption chiller both coupled with respective thermal storages. Through this evaluation, it is possible to identify the optimal coupling of the devices as a function of the load requirements and understand the great influence of their sizing on the energy management benefits. The analysis is performed with reference to cold and warm thermal load required by a residential case study. The performance analysis takes place in representative days of different seasons and the results are extended on an annual base. The power request profiles are developed on the basis of literature data. The results are compared on an economic basis considering the NPV (Net Present Value) index, evaluated using as the benchmark a standard plant layout composed by a water boiler and an electric chiller. [ABSTRACT FROM AUTHOR]

The increasing need for energy and cost efficient solutions for thermal and electric supply is giving new life to CHP plants, even for small power sizes. It is renowned that the optimal application of a CHP plant is to satisfy as much as possible both the electricity and the thermal requirements of the loads, but the frequent applicative context, especially for residential and/or tertiary buildings, is unbalanced towards the thermal needs, so that the sizing of the CHP is determined by the electric loads, at least in the Italian tariff structure context, with the consequence that the generator is relatively small and, consequently, the installation costs represent a consistent part of the capital investment. The increasing level of the performance of the electric heat pump can sensitively minimize the former issue: the combination between a CHP and an EHP can led to a larger size of the co-generative unit, whose exceeding power output can feed the heat pump so that to efficiently satisfy most of the thermal loads of the plant. In this paper an application case referred to an office building is presented: the optimal size of the system will be discussed, and the economic results (in terms of PBT and NPV) of the management of the plant compared with other commonly exploited solutions: • Conventional supply, with the heat produced by a gas boiler, the cooling from an electric chiller, and the electricity purchased by the grid; • Optimal sizing of the CCHP based on the heating loads duration curve, with the engine operated in thermal-led; • Optimal sizing of the CCHP based on the electric loads duration curve, with the engine operated in power-led. The environment performance will be discussed as well, focusing on the comparison between the different solutions in terms of equivalent CO 2 emissions and primary energy consumptions. [ABSTRACT FROM AUTHOR]