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This paper presents a hybrid system consisting of a 100 kWe micro gas turbine (MGT) that juxtaposes the energy production of a photovoltaic (PV) plant whose yearly yield is available by on field measurements. The aim of the work is to model and investigate the behavior and the performance of a hybrid MGT-PV system under the topical constraint of firming renewable power and hence of guaranteeing a reliable power production to the grid. We propose a solution for the sizing of the PV plant and two strategies for the management of the hybrid system in order to guarantee a reliable day-ahead hourly forecast of the electric power that can be actually produced by the plant under whatever ambient condition. The results ascertain the advantages of the upgraded system in terms of natural gas consumption (−16%) and and NO X (∼ −33%) with a higher local emission of CO. In particular, the proposed hybrid system: i) solves the problem due to the unpredictability of PV energy production; ii) grants a significant reduction of the primary fuel usage and specific energy cost; but iii) increases the level of local pollutants, since it internalizes the emissions previously generated in a centralized power plant to produce the amount of electricity of the hybrid system. [ABSTRACT FROM AUTHOR]

The paper presents the operational results of a real life residential microgrid which includes six apartments, a 20 kWp photovoltaic plant, a solar based thermal energy plant, a geothermal heat pump, a thermal energy storage, in the form of a 1300 l water tank and two 5.8 kW h batteries supplying, each, a couple of apartments. Thanks to the thermal energy storage, the solar based thermal energy plant is able to satisfy the 100% of the hot water summer demand. Therefore the thermal energy storage represents a fundamental element in the management of the residential demand of thermal energy. It collects renewable thermal energy during day-time to release it during night-time, effectively shaving the peak of the thermal energy demand. The two electric storages, on the other hand, provide the hosted electrical subsystems with the ability to effectively increase the self-consumption of the local energy production, thus lowering the amount of energy surplus to be sold back to the grid, and increasing the self-sufficiency of the microgrid. For instance, the storage has supported self-consumption up to the 58.1% of local energy production with regard to the first battery, and up to the 63.5% with regard to the second one. Also, 3165 and 3365 yearly hours of fully autonomous activity have been recorded thanks to the first, and the second battery respectively. On the other hand, the yearly average efficiency amounts to 63.7%, and 65.3% respectively, for the first and second battery. In the second part of the paper we propose a computational framework to evaluate the overall performance of the microgrid system, while accounting different operating conditions and energy management policies. From this perspective, the framework acts as a useful modeling and design tool, to assess the opportunity of employing alternative energy management system topologies and strategies. Eight different configurations, with growing complexity, have been derived from the original system on purpose. The simulations, carried out based on real data related to one-year time period, have provided results showing that, the higher the integration level of electrical and thermal storage is, the higher degree of self-sufficiency can be achieved by the microgrid, and, in turn, the more consistent the yearly energy saving become. Nevertheless, despite the energy cost reduction achievable with the availability of storage systems in the Leaf House, their high investment cost made them not really profitable at the current price conditions for devices and energy purchase. [ABSTRACT FROM AUTHOR]

This study investigates how a district with a high capacity of non-controllable renewable electricity generation can entirely self-consume its production at a community level either directly or for heating and cooling, thus potentially fulfilling the concept of "Renewable Energy Community". It investigates the potential role of storage systems and polygeneration in renewables self-consumption, by also exploiting the synergies among different energy networks in a real residential district with high PV penetration. Two scenarios were modeled other than the "baseline": the first one evaluating the optimal portfolio of energy conversion and storage technologies, and a second one achieving the same goal only using batteries. Both scenarios proved to be a viable solution to exploit the excess of electricity production from the PV plants in the district only through local self-consumption. The results show that a multi-energy system is the most cost-effective solution in doing so, exploiting polygeneration technologies (CHP) and the storage of energy as thermal, electrical, and chemical through power-to-gas. In particular, the least cost solution entails a 42 kWe CHP micro gas engine fueled by a natural gas-hydrogen blend, a 135 kWh battery system, and a 2830 kWh hydrogen storage. • P2G coupled to polygeneration is a viable solution to store renewable energy. • Cost-effective optimal solution consists of cogeneration, electric and hydrogen storages. • The use of only batteries is too expensive to store the excess of renewables in a district. • Batteries are more effective than P2G with hydrogen due to the higher roundtrip efficiency: 90% vs. 23%. • Synergies among energy networks and distributed generation can reduce the power ramp. [ABSTRACT FROM AUTHOR]

Due to their non-deterministic behaviour, renewable energies are defined as non-dispatchable energies and are largely coupled with energy storage systems to overcome the problem of matching energy production and demand. Hence, in the energy efficiency and conservation field there is growing interest towards energy storage systems, especially when combined with the demand side management (DSM) concept, representing DSM the possibility of shaping end user electricity consumption. In this work an existing installation of a thermal energy storage (TES) system coupled with heat pumps in an industrial building is presented and a dynamic simulation model is built to represent its behaviour. Simulations are performed to show the load shifting potential of such storage and costs and energy use are assessed for different configurations, in order to evaluate the viability of this TES application. In particular the demand side strategy considered is aimed at shifting energy demand for cooling to weekend daytime to recover surplus PV electricity or otherwise to off peak hours to profit from lower electricity tariffs. It is found that the use of TES implies increased energy demand, while costs can decrease when electricity tariffs with a considerable difference between on peak and off peak rates are applied. Furthermore the integration with renewable sources for electricity production, such as PV panels, makes the installation of TES economically interesting independently of the electricity tariff in place. However the more relevant aspect for the overall economic feasibility of such installation is the initial capital investment. [ABSTRACT FROM AUTHOR]

This work analyzes and compares the effects of the secondary optics on the performance of a triple junction solar cell used in a compact HCPV prototype unit. The HCPV system is composed of triple junction III-V (Ga 0.5 In 0.5 P, Ga 0.99 In 0.01 As and Ge) solar cells that have a circular shape with an active area of 4.15 mm 2 . The optics consists of a primary PMMA square Fresnel lens (75 mm – side) with constant pitch and a refractive secondary optic (RTP) made of dielectric material. The overall geometrical concentration ratio is 1300×. The tracking system is a tip-tilt type two-axis mechanism driven by stepper motors. The HCPV secondary optics were firstly designed at Polo Tecnologico Andrea Galvani and then tested on the prototype unit at the Engineering Faculty of Università Politecnica delle Marche in Ancona, Central Italy. The aim of the paper is to present the numerical and experimental performance results of two different secondary optics and to assess the effects of the main construction parameters (i.e.: the geometry of the secondary optics and the distance between the two optics) on the concentration efficiency. Moreover, two different 3 J cell receiver types were tested, the Insulated Metal Substrate technology (IMS) and the Direct Bonded Copper (DBC) technologies. The experimental tests were performed under real outdoor operating conditions, therefore also the Direct Normal Irradiance (DNI) was measured. In general, the free-form optics showed significant improvements in terms of overall irradiance and homogeneity. In the best configuration the electric efficiency achieved 39.55%, neglecting the primary optics losses, thus confirming that the presented system setup is able to reach the highest standards of CPV technology performance. [ABSTRACT FROM AUTHOR]