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This work presents a novel renewable trigeneration plant powered by solar, geothermal and biomass energy, producing simultaneously electricity, heat and cool. The developed system includes a 193 m2 photovoltaic field, a 159 kWh lithium-ion battery, a 30 kWe organic Rankine cycle, a 350 kWth biomass auxiliary heater, a geothermal well at 96 °C and a 80 kW single stage H2O/LiBr absorption chiller. The Organic Rankine Cycle is mainly supplied by the geothermal well, producing electricity. An additional amount of electricity is produced by the photovoltaic panels. A detailed dynamic simulation model was developed in TRNSYS environment in order to calculate both energy and economic performance of the plant. The model includes algorithms validated versus literature and experimental data. The model of the renewable trigeneration plant is used for a suitable case study, a residential building in the Campi Flegrei (Naples, South Italy) area, a well-known location for its geothermal sources and good solar availability. The proposed plant exhibits promising energy performance achieving a primary energy saving of 139%, mainly due to the obtained excess energy. From the economic point of view, the proposed plant gets a limited profitability, showing a payback period of about 19 years, mainly due to the high capital cost of the employed technologies. A thermo-economic optimization is also implemented, considering photovoltaic field and battery capacities as independent variables. The results of the optimization suggest increasing the area of the photovoltaic field and to limit the capacity of electric energy storage system, due to the high specific capital cost of the lithium-ion battery. Finally, a multi-objective optimization is also carried out, aiming at calculating the set of the optimal design variables of the proposed trigeneration plant.

During the past few years a significant effort has been performed in order to promote the use of renewable energy sources. However, one of the main barriers for a mature commercialization is due to the unpredictability of the renewable power production, mainly in case of wind and solar energy. Unfortunately, electric storage devices are often poorly profitable. Therefore, some more stable renewable energy systems must be designed. In this framework, this paper presents a novel hybrid renewable system consisting of Building Integrated PhotoVoltaic panels and small-scale Wind Turbines and double-stage heat pumps. This combination is very promising since it reduces the typical fluctuations of solar or wind systems, achieving a more stable profile of the overall power production. A detailed dynamic simulation model is developed in TRNSYS environment, including validated models for all the components and a suitable thermoeconomic analysis. A case study is implemented for a hotel building, where the space heating and cooling energy is supplied by an electrically driven reversible air-to-water Heat Pump, supplied by the electricity produced by Building Integrated PhotoVoltaic panels and Wind Turbines. the thermal energy recovered from the HP desuperheater is coupled with the thermal energy produced by a two-stage cascade cycle Heat Pump to produce domestic hot water. Results are presented in terms of hourly, monthly and yearly system performance data as well as by discussing the results of a detailed sensitivity analysis performed to detect the optimum configuration and weather zone of this hybrid renewable system. An analysis of the building envelope features is also performed, according to the nearly zero energy buildings target. Results showed that the combination of photovoltaic and wind technologies allows one to significantly enhance the stability of the renewable power production. Results also show that the use of heat pumps leads to a reduction of the primary energy demand for building space heating/cooling and domestic hot water by 30%. A payback period of about 5.2 years is obtained and the optimum configuration suggests adopting one 20 kW Wind Turbine for the selected case study.

District Heating and Cooling is considered an efficient solution to address the thermal energy demand of the building sector and reduce its environmental impact. In this paper, a 5th generation bidirectional heating/cooling network is designed and modelled. The network is coupled with water-to-water heat pumps, ground heat pumps and a photovoltaic field and is designed to meet the energy requirements of a 50-building district in the city of Leganes (Madrid). All components are modelled in TRNSYS 18. The studied network achieves a primary energy saving index of 64% and reduces the CO2 emissions by 76% relative to the current situation. The economic analysis of the system results in the relatively long payback period of 33 years, mainly due to the high costs of excavation and the installation of the heat pumps and pipes. With the current design, the photovoltaic field meets only 30% of the electricity demand of the district. However, additional energy storage could help align the power production with the actual power demand better and avoid grid balancing issues. The inclusion of other types of thermal energy consumers would also enhance the performance of the network by increasing the simultaneity between cooling and heating demands.

This work presents a dynamic analysis of an anaerobic digestion plant, in which concentrating photovoltaic/thermal collectors are used to match a part of both heating and power demand of the process. The system is supplied by the organic fraction of municipal solid waste. The system also includes a thermal storage tank and an auxiliary heating system. An up-grade section is also included, to produce biomethane, suitable for injection into the natural gas pipeline network. For such hybrid solar-biomass system, a comprehensive simulation model was developed in MATLAB®, calculating the time-dependent production of biomethane as a function of the operating temperature within the digester. The model, based on differential equations and thermal balances, accounts for both thermal and biological phenomena occurring within the process, taking into consideration the geometrical and structural characteristics of the system. The consistent Anaerobic Digestion Model 1 is used to model the biological process, evaluating the biogas production as a function of a series of operating variables: the digester operating temperature, mass flowrate and temperature of the hot water entering the digester, ambient temperature, mass flowrate and composition of the organic waste in input. The model also calculates the electric consumption of the upgrading process, used to convert the biogas into biomethane. Such model was integrated into the simulation platform of the overall plant, developed in TRNSYS, evaluating the energy, environmental and economic performance of the entire system. A case study is presented, showing the dynamic performance of the system under evaluation: for such case, a primary energy saving of 24% was found, with respect to a conventional digester; around 20% of the overall thermal energy demand is met by solar energy; finally, a promising payback time of about 3 years was estimated.

The production of “green hydrogen” is currently one of the hottest topics in the field of renewable energy systems research. Hydrogen storage is also becoming more and more attractive as a flexible solution to mitigate the power fluctuations of solar energy systems. The most promising technology for electricity-to-hydrogen conversion, and vice versa, is the reversible solid-oxide cell (SOC). This device is still very expensive, but it exhibits excellent performance under dynamic operating conditions compared to the competing devices. This work presents the dynamic simulation of a prototypal renewable plant combining a 50 kW photovoltaic (PV) field with a 50 kW solid-oxide electrolyzer cell (SOEC) and a compressed hydrogen tank. The electricity is used to meet the energy demand of a dwelling located in the area of Campi Flegrei (Naples). The SOC efficiency is simulated by developing a mathematical model in MATLAB®. The model also calculates the cell operating temperature as a function of the input current. Once the optimal values of the operating parameters of the SOC are calculated, the model is integrated in the transient system simulation tool (TRNSYS) for dynamic analysis. Furthermore, this work presents a parametric analysis of the hydrogen storage system (HSS). The results of the energy and environmental analyses show that the proposed system can reach a primary energy saving by 70% and an amount of saved CO2 of 28 tons/year. Some possible future market scenarios are considered for the economic analysis. In the most realistic case, the optimal configuration shows a simple pay back lower than 10 years and a profit index of 46%.

This work presents a dynamic simulation model of a prototypal renewable plant producing electricity, heat and cool. The hybrid system consists of a 6 kWe Organic Rankine Cycle (ORC), a 17.1 kWf absorption chiller, a geothermal well, a 25 m2 evacuated solar collector field, a 200 kWt biomass heater and a 45.56 kWh electric energy lithium-ion storage system. The geothermal well at 96 °C, in combination with the solar field, supplies the thermal energy driving the ORC. This simulation model is implemented in TRNSYS environment. In order to evaluate the thermoeconomic performance of this renewable trigeneration plant, a suitable case study is analysed: a bar and soccer centre in the area of Campi Flegrei (Naples). By the simulation, interesting results in terms of energy and environmental performance are obtained. The proposed renewable power plant achieves a primary energy saving of 94.54% and a reduction of CO2 emissions equal to 97.36%. The high total capital cost of the plant significantly affects the payback period of 16.7 years. However, in the future European energy scenarios, where a full decarbonization will be achieved and the capital cost of the renewables will significantly decrease, the use of these technologies will be pivotal and significantly profitable.

This work presents a thermoeconomic comparison between two different solar energy technologies, namely the evacuated flat-plate solar collectors and the photovoltaic panels, integrated as auxiliary systems into two renewable polygeneration plants. Both plants produce electricity, heat and cool, and are based on a 6 kWe organic Rankine cycle (ORC), a 17-kW single-stage H2O/LiBr absorption chiller, a geothermal well at 96 °C, a 200 kWt biomass auxiliary heater, a 45.55 kWh lithium-ion battery and a 25 m2 solar field. In both configurations, electric and thermal storage systems are included to mitigate the fluctuations due to the variability of solar radiation. ORC is mainly supplied by the thermal energy produced by the geothermal well. Additional heat is also provided by solar thermal collectors and by a biomass boiler. In an alternative layout, solar thermal collectors are replaced by photovoltaic panels, producing additional electricity with respect to the one produced by the ORC. To reduce ORC condensation temperature and increase the electric efficiency, a ground-cooled condenser is also adopted. All the components included in both plants were accurately simulated in a TRNSYS environment using dynamic models validated versus literature and experimental data. The ORC is modeled by zero-dimensional energy and mass balances written in Engineering Equation Solver and implemented in TRNSYS. The models of both renewable polygeneration plants are applied to a suitable case study, a commercial area near Campi Flegrei (Naples, South Italy), a location well-known for its geothermal sources and good solar availability. The economic results suggest that for this kind of plant, photovoltaic panels show lower pay back periods than evacuated flat-plate solar collectors, 13 years vs 15 years. The adoption of the electric energy storage system leads to an increase of energy-self-sufficiency equal to 42% and 47% for evacuated flat-plate solar collectors and the photovoltaic panels, respectively.

The paper presents an in-depth analysis of a novel scheme for the sustainable mobility, based on electric vehicles, photovoltaic energy and electric energy storage systems. The work aims to analyse such innovative system, putting in evidence its advantages in comparison to a conventional one, based on the grid-to-vehicle technology. The study also provides interesting guidelines for potential users and system designers. Two case studies are presented: i) the taxi fleet of the city centre of Naples and ii) the cargo vans of the city of Salerno; both towns are in Southern Italy. For each case, the hourly power consumption of the vehicles was evaluated, as a function of the daily trip length. An accurate procedure was implemented to select the sites suitable for the installation of the charging stations, including a photovoltaic field and an electric storage system. A comparison was also performed between two different electric storage technologies: lead-acid and lithium-ion battery. The case studies were analysed by means of a detailed dynamic simulation model, developed in TRNSYS. A sensitivity analysis was also performed, to evaluate how different values of the most important design and operating parameters affect the system overall performance. It was found that the results are mostly affected by solar field area, capacity of the energy storage system and investment cost. The comparison between the two selected storage technologies did not exhibit significant differences. For both the cases investigated, it was found that, during the summer, solar energy covers an important amount of the total energy demand. On the contrary, in winter the amount of energy provided by the public electric grid was high. From an economic point of view, assuming a lithium-ion battery capital cost equal to 90 €/kWh, acceptable pay-back periods (about 6 years) were obtained, for both the applications considered.

This paper presents the integration of the evacuated tube solar collectors into a novel solar polygeneration plant. The analysis is performed by evaluating the energy and economic performance of the plant, coupled to a multi-effect distillation unit for seawater desalination, a single effect water lithium bromide absorption chiller, a biomass auxiliary heater, heat exchangers, tanks and balance-of-plant devices. Solar collectors produce heat, at about 90 °C, used for space heating and domestic hot water production, driving the absorption chiller (used for space cooling). Solar heat, combined the heat produced by the biomass auxiliary heater, also drives the multi-effect distillation unit producing desalinated water. The plant is simulated by means of a zero-dimensional dynamic model, developed in TRNSYS environment, which considers several control strategies, for the plant management. The economic analysis shows that the economic profitability significantly improves in case of feed-in tariffs, achieving a payback period of about 3.5 years. The optimization procedure performed by using the Design of Experiment method, returned a payback period of 2.4 years, by selecting the solar field area equal to 1200 m2, the tank dead band temperature to 2 °C, the summer/winter outlet set point temperature from the solar field equal to 95 °C/50 °C.

The issues dealing with climate change also caused by the private transport sector are attracting more and more attention in European Countries. This work aims to simultaneously address the issue related to the management of the energy demand of the private transport sector and building sector in the framework of the smart grid energy districts. The investigated smart grid is designed for meeting the energy demands of a district, including the energy demand for space heating and cooling, as well as the electric energy of a lot of buildings, occupied by people who only use electric vehicles. The system is equipped with a cogenerator, which is expected to operate according to the base-load operation strategy, constantly producing the rated power for whatever power demanded. Two charging strategies are analyzed and compared with the aim of detecting which strategy better exploits the power produced by the cogenerator. The performed dynamic simulations of the whole system are carried out by means of TRNSYS tool. TRNSYS allows one to use a detailed library of components which carefully model and simulate the devices included in the proposed system model. Suitable control strategies are also developed in order to improve the energy, environmental and economic performance of the smart grid. The results show that this layout allows one to considerably reduce the primary energy consumption and carbon dioxide emissions of the investigated district. As matter of fact, the proposed smart energy grid achieves a primary energy saving index of about 32%, with a payback period of about 6 years. These promising results suggest that the proposed smart energy grid may be useful for addressing the issue related with environmental impact of building sector and private transport sector.

A dynamic simulation model of a novel solar–geothermal polygeneration system and the related exergetic and exergoeconomic analyses are presented in this paper. The plant is designed in order to supply electrical, thermal and cooling energy and fresh water for a small community, connected to a district heating and cooling network. The hybrid system is equipped with an Organic Rankine Cycle fueled by medium-enthalpy geothermal energy and by a Parabolic Trough Collector solar field. Geothermal brine is also used for space heating and cooling purposes. Finally, geothermal fluid supplies heat to a Multi-Effect Distillation unit, producing also desalinized water from seawater. Dynamic simulations were performed in order to design the system. The overall simulation model, implemented in TRNSYS environment, includes detailed algorithms for the simulation of system components. Detailed control strategies were included in the model in order to properly manage the system. An exergetic and exergoeconomic analysis is also implemented. The exergetic analysis allows to identify all the aspects that affect the global exergy efficiency, in order to suggest possible system enhancements. The accounting of exergoeconomic costs aims at establishing a monetary value to all material and energy flows, then providing a reasonable basis for price allocation. The analysis is applied to integral values of energy and a comparison of results between summer and winter season is performed. Results are analyzed on different time bases presenting energetic, exergetic, economic and exergoeconomic performance data. Results show that global exergy efficiency varies between 40% and 50% during the “Thermal Recovery Mode” operation and between 16% and 20% during the “Cooling mode” operation. It was also found that electricity, chilled water, cooling water and desalinated water exergoeconomic costs vary respectively in the ranges 0.1475–0.1722 €/kW h, 0.1863–0.1888 €/kW hex, 0.01612–0.01702 €/kW hex and 0.5695–0.6023 €/kW hex.