Search

This paper addresses the problem of the reduction in the huge energy demand of hospitals and health care facilities. The sharp increase in the natural gas price, due to the Ukrainian–Russian war, has significantly reduced economic savings achieved by combined heat and power (CHP) units, especially for hospitals. In this framework, this research proposes a novel system based on the integration of a reversible CHP solid oxide fuel cell (SOFC) and a photovoltaic field (PV). The PV power is mainly used for balancing the hospital load. The excess power production is exploited to produce renewable hydrogen. The SOFC operates in electrical tracking mode. The cogenerative heat produced by the SOFC is exploited to partially meet the thermal load of the hospital. The SOFC is driven by the renewable hydrogen produced by the plant. When this hydrogen is not available, the SOFC is driven by natural gas. In fact, the SOFC is coupled with an external reformer. The simulation model of the whole plant, including the reversible SOFC, PV, and hospital, is developed in the TRNSYS18 environment and MATLAB. The model of the hospital is calibrated by means of measured data. The proposed system achieves very interesting results, with a primary energy-saving index of 33% and a payback period of 6.7 years. Therefore, this energy measure results in a promising solution for reducing the environmental impact of hospital and health care facilities. [ABSTRACT FROM AUTHOR]

Smart energy networks including renewables and energy storage systems are a promising technology for improving the sustainability of residential districts and private mobility. In this work, a smart energy network is analyzed, based on photovoltaic panels, electric energy storage systems, heat pumps and electric vehicles. The system consists of a fully electric residential district, where air-to-air heat pumps are used for space heating and cooling and air-to-water heat pumps provide domestic hot water; a photovoltaic field meets the power load of the residential district, including charging stations for electric vehicles. A district electric energy storage system is included for balancing power supply and demand: two storage technologies are considered and compared in this work: a lithium-ion battery and a reversible solid oxide fuel cell. These systems are modelled and dynamically simulated in Transient Systems Simulation Program (TRNSYS) 18. A case study is discussed, where the proposed systems exhibit promising results in terms of primary energy saving: for example, the renewable energy matches almost 74–77% of the district primary energy demand for the analyzed smart energy districts. Moreover, both the proposed systems achieve very profitable results with a payback period of 3.5–4.4 years. Both the analyzed layouts achieve very similar results. [ABSTRACT FROM AUTHOR]

The anaerobic digestion of the organic fraction of municipal solid waste and the biogas production obtained from its stabilization are becoming an increasingly attractive solution, due to their beneficial effects on the environment. In this way, the waste is considered a resource allowing a reduction in the quantity of it going to landfills and the derived greenhouse gas emissions. Simultaneously, the upgrading process of biogas into biomethane can address the issues dealing with decarbonization of the transport. In this work, the production of biogas obtained from the organic fraction of municipal solid wastes in a plug flow reactor is analyzed. In order to steer the chemical reactions, the temperature of the process must be kept under control. A new simulation model, implemented in the MatLab® environment, is developed to predict the temperature field within the reactor, in order to assess how the temperature affects the growth and the decay of the main microbial species. A thermal model, based on two equilibrium equations, is implemented to describe the heat transfer between the digester and the environment and between the digester and the internal heat exchanger. A biological model, based on suitable differential equations, is also included for the calculation of the biological processes occurring in the reactor. The proposed anaerobic digestion model is derived by the combination of these two models, and it is able to simultaneously simulate both thermal and biological processes occurring within the reactor. In addition to the thermal energy demand, the plant requires huge amounts of electricity due to the presence of a biogas upgrading process, converting biogas into biomethane. Therefore, the in-house developed model is integrated into a TRNSYS environment, to perform a yearly dynamic simulation of the reactor in combination with other renewable technologies. In the developed system layout, the thermal energy required to control the temperature of the reactor is matched by a solar thermal source. The electrical demand is met by the means of a photovoltaic field. In this work, a detailed thermoeconomic analysis is also proposed to compare the environmental impact and economic feasibility of a biomethane production plant based on a plug flow reactor and fed by renewables. Several economic incentives are considered and compared to determine the optimal solution, both in terms of energy and economic savings. The plant is designed for the treatment of a waste flow rate equal to 626.4 kg/h, and the biomethane produced, approximately 850 tons/years, is injected into the national gas grid or supplied to gas stations. In the proposed plant, a solar field of an evacuated tube collector having a surface of approximately 200 m2 is able to satisfy 35% of the thermal energy demand while over 50% of the electric demand is met with a photovoltaic field of 400 m2. A promising payback time of approximately 5 years was estimated. [ABSTRACT FROM AUTHOR]

This system can be considered as a sort of virtual energy storage system, because the excess renewable electricity is used to produce the hydrogen for this process. Here, hydrogen is used as an energy storage system because it is produced when the renewable energy production is higher than the user demand and is consumed when the user demand is higher than the renewable energy production. During the 20th century, the global energy system was mainly based on the use of fossil fuels, such as oil, natural gas, and coal. Overview of the Recent Advances in Green Energy Technologies In the past few years, several papers have been published proposing novel technologies for the production of green hydrogen by renewables and/or to integrate hydrogen into existing energy systems. [Extracted from the article]

The authors point out that luminescent solar concentrators were extensively investigated for purposes of power generation based on photovoltaic effect but a lack of knowledge in literature regards the investigation about the use of thermal energy generated at the edges of luminescent solar concentrators. In the private single buildings and building districts, solar thermal collectors can also be integrated to match the thermal energy demand of the users as well as the cooling energy demand by absorption and adsorption chillers. The renewable energy technologies attracted 70% global energy investment in 2021, but the global CO SB 2 sb emission is increased by 1.5 billion tons in the same year [[1]]. Two conventional reference energy systems were considered: (i) a reversible heat pump for both heating and cooling energy purposed; and (ii) a natural gas boiler for heating energy purposes and air-cooled chillers in the cooling months. [Extracted from the article]

This work presents a dynamic simulation model for the production of liquefied biomethane by anaerobic digestion. This layout includes anaerobic digesters supplied by the organic municipal solid wastes, biogas upgrading and biomethane liquefaction units, photovoltaic panels, evacuated solar collectors, electric and thermal storages. Solar collectors provide the heat to anaerobic digesters. Photovoltaic panels supply electricity to the electric devices of the plant. The dynamic model evaluates the electric consumption for the biogas upgrading and biomethane liquefaction units and the thermal load of the anaerobic digesters. The produced liquified biomethane is supplied as fuel to some ships traveling from the mainland to the islands of the Gulf of Naples. The simulation models of the anaerobic digester, biogas upgrading and biomethane liquefaction units are developed in MATLAB® environment and subsequently integrated in TRNSYS18, where the whole plant is modelled. The model of anaerobic digester takes into account both the biological and thermal processes and it considers the digester geometrical and structural features. The biogas upgrading unit consists of a three-stages selective membrane system, whereas the liquefaction system is modelled by the conventional Linde cycle. Significant energy savings and CO 2 emissions reduction are obtained, that is a strategic outcome for harbours located in densely populated cities. When the proposed system is compared with the reference system consisting of an existing fleet, equipped with very old ferries using internal combustion diesel engines, the primary energy saving is about 50 %. Considering the present Italian funding policy for biomethane, such system exhibits a good economic profitability. [Display omitted] • A dynamic simulation model for the production of liquefied biomethane is developed. • Modeling of anaerobic digestion, biogas upgrading and biomethane liquefaction. • The plant is equipped with photovoltaics and solar thermal collectors. • The proposed system reduces the primary energy consumption by 38 %. [ABSTRACT FROM AUTHOR]

The conference event allowed researchers to present recent research in the field of non-renewable and renewable energy sources and technologies, sustainable energy development, green energy and economy, environmental protection in energy managements systems, power-to-gas and power-to-liquid technologies, alternative fuels and other areas. New knowledge concerning non-renewable and renewable energy sources and technologies, green energy and economy, environmental protection in energy, power generation technologies, alternative fuels and other energy- and environment-related areas of research is constantly provided by the intense research activity of researchers worldwide. The energy sector, along with the conditions of the natural and built environment, are significantly affected by the tremendous increase in total energy consumption. [Extracted from the article]

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 kW e organic Rankine cycle, a 350 kW th biomass auxiliary heater, a geothermal well at 96 °C and a 80 kW single stage H 2 O/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. • Polygeneration system based on the combination of geothermal and photovoltaic energy. • Optimization analysis of a fully renewable polygeneration plant. • Dynamic simulation of a polygeneration plant meeting the thermal and electric load of a residential user. • The proposed system exhibits interesting environmental and energy performance. [ABSTRACT FROM AUTHOR]

The energy refurbishment of residential heating and cooling systems is crucial to achieve the carbon neutrality expected by 2050. In this framework, many researchers are developing low-temperature district heating and cooling systems, integrated with renewable technologies. In particular, fourth-generation district heating and cooling systems are largely used, and a considerable number of these systems have been installed in the last few years. This is due to the wide use of heat pumps and low-temperature heating terminals, such as radiant floors and fan coils. Fifth generation district heating and cooling systems include several significant advancements with respect to the previous technology. This research proposes a thermoeconomic comparison between fourth generation and fifth generation district heating cooling networks, including ground-source heat pumps, supplying heating and cooling energy to a residential district located in Leganes, Madrid. The thermal load of the residential district network is simulated by means of detailed models of the buildings. In the proposed systems, the electric load is partially met by a 3 MW photovoltaic field. The dynamic simulation model of such districts is developed in TRNSYS18, including detailed models for each component. Both the analysed technologies achieve very promising results from both economic and energy points of view. The Primary Energy Saving for the 4th and 5th generation districts are equal to 97% and 81%, respectively. Finally, 4th and 5th generation networks determine a reduction of the CO 2 emissions by the 98% and the 87%, respectively. The development of innovative district heating and cooling systems is crucial for the reduction of the environmental impact of buildings sector. However, for residential applications, novel 5th generation networks do not exhibit a better energy and economic performance with respect to mature 4th generation networks, due to the scarce simultaneous heating and cooling demand. • 4GDHC shows a PES of 97% whereas 5GDHC 81%. • Long SPB period, i.e. 16 years (4th generation) and 21 years (5th generation). • The lithium-ion battery is fundamental for mitigating the mismatching with the PV. • 4GDHC is the best solution in case of pure residential district. [ABSTRACT FROM AUTHOR]

Power to gas technology is an innovative solution to promote the use of renewable energy technologies, also including e-fuels. This work presents a techno-economic analysis of a novel concept of a renewable power to gas plant. A 2.4 MW solid oxide electrolyzer fed by a 3.1 MW photovoltaic field is coupled with a biomethane production unit to produce synthetic methane by means of a 2.4 MW methanation unit. The hydrogen produced by the electrolyzer is used for the methanation reaction aiming at producing natural gas at net zero carbon emissions. The CO 2 is obtained as a byproduct of the membrane separation in a biogas upgrading unit. The methanation unit and the electrolyzer models are developed in MatLab and integrated in TRNSYS to perform a dynamic simulation of all the components and the system as a whole. Dynamic simulation results show a 42% increase in the production of natural gas from renewable energy sources. The thermoeconomic analysis shows a remarkable primary energy saving index of 176% and a total amount of 896 tons of CO 2 equivalent emissions saved. As expected, the critical point is the economic feasibility since the simple payback is 9 years in case local incentives and subsidies are considered. The parametric analysis on the photovoltaic capacity shows that the simple payback dramatically depends on such design parameter, varying from 6 years in the best case scenario to 92 years in the worst case scenario. [Display omitted] • Natural gas production increases by 42% with respect to the base case. • A primary energy saving of 176% is due to great production of synthetic methane. • Even in case of subsidies the economic performance is quite poor. • Each MWh of renewable electricity is converted into 6.5 MWh of synthetic methane. [ABSTRACT FROM AUTHOR]

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. • Building integrated photovoltaic panels coupled with small size wind turbines. • Dynamic simulation model developed with TRNSYS software. • Sensitivity analysis on the building envelope features and weather zones. • Simple payback period of about 4.4 years for two 20 kW wind turbines. [ABSTRACT FROM AUTHOR]

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. • Dynamic simulation of a novel polygeneration plant based on evacuated tube collectors. • Multiple effect distillation unit is supplied by both solar and biomass energy. • Best economic solution is identified by Design of Experiment optimization technique. • Optimization analyses suggest selecting a solar field area equal to 1200 m2. [ABSTRACT FROM AUTHOR]

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. • Dynamic analysis of electric vehicle solar parking focused on sustainable mobility concept. • Transport/statistical model development for both private/public transport sector. • Environmental, energy and economic comparison between lead-acid and lithium-ion battery. • Interesting pay-back periods in case of lithium-ion battery capital cost expected reduction. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a detailed exergetic and technoeconomic analysis of a Building Integrated PhotoVoltaic Thermal (BIPVT) system. BIPVT system, consisting of flat-plate PVT solar collectors, is integrated in the south facing façade of a non-residential high-rise building. BIPVT collectors produce: i) thermal energy for space heating purposes, by a radiant floor system; ii) Domestic Hot Water (DHW); iii) electricity. Electric air-to-water heat pumps/chillers and a condensing gas fired boiler are used as auxiliary systems for space heating/cooling and DHW, respectively. In addition, the system also includes an electricity storage system coupled to the BIPVTs in order to mitigate the effects of solar energy intermittency and to obtain a virtually grid-independent system. In order to compare the proposed BIPVT system to a conventional building, a reference building model, i.e. without BIPVTs, energy storage and radiant floor, is considered. Here, the space heating and cooling energy is supplied by air-to-water heat pumps (one for each floor), DHW is produced by a condensing boiler and electricity is supplied by the national grid. The comparison is performed for three thermal zones, well representative of the thermal behaviour of the whole building. In this paper, a detailed dynamic simulation model is developed by means of well-known tool TRNSYS 17, in order to predict the transient behaviour of BIPVT system. Energy and exergy balances are taken into account to determine, for the 1-year operation, the exergy destructions and exergetic efficiencies of each of the investigated components. The economic viability of the proposed system is also discussed and the resulted Simple Pay Back period is about 4 years. From the carried out exergy analysis, the average exergetic efficiency of electricity storage system is about 90%, whereas the condensing boiler one is close to 2% all year long. In addition, an exergy analysis on the proposed BIPVT system located in several European weather zones is also carried out, as well as a suitable exergy analysis is performed by varying the capacity of the electricity storage system. Such analyses aim to assess the weather condition and the size of electricity storage effects on the destroyed exergy and exergetic efficiency of BIPVT collectors and electricity storage, respectively. It resulted that, the highest destroyed exergy of BIPVT occurs in Larnaca (150 MWh/year) vs the lowest one in Belfast (87 MWh/year), whereas the BIPVT collectors exergetic efficiencies range from 8.4% for Larnaca to 8.8% for Belfast. Highlights • Exergy and thermoeconomic analysis of BIPVT - electricity storage system. • Assessment of exergy destruction and efficiencies of main system components. • Case study for a non-residential building in different European weather zones. • Analysis of heating, cooling, DHW and electricity production. • Assessment of exergetic, energy and economic enhancement vs. traditional systems. [ABSTRACT FROM AUTHOR]

Abstract The paper presents a thermoeconomic comparison between two different solar thermal technologies, namely Linear Fresnel Reflector (LFR) and evacuated tube solar collectors (ETC), integrated into a polygeneration plant. The system produces space heating and cooling, domestic hot water and drinkable desalinated water, by means of a multi-effect distillation (MED) system. In the ETC layout, a single-effect LiBr H 2 O absorption chiller (ACH) is included; in the second layout, based on LFR collectors, a double-effect ACH is considered. An auxiliary biomass-fired heater is used to supply the additional heat required by the MED unit, in case of low availability of solar radiation. Both plants are simulated by means of a zero-dimensional dynamic simulation energy model, developed in TRNSYS environment. The model also includes detailed thermo-economic calculations. The results show that in some winter weeks, the solar fraction for freshwater production ranges between 15% and 20% for the ETC-based system, whereas is zero in case of LFR, when the MED unit is supplied only by the biomass auxiliary heater. Therefore, for the analysed case study, ETCs resulted more profitable than LFRs, achieving simple pay-back periods of about 4–5 years. Highlights • The analysed polygeneration plant produces fresh water, heat and cool. • Linear Fresnel and evacuated tubes solar collectors are compared. • Solar desalination technique is based on multi-effect distillation process. • The system is dynamically simulated in TRNSYS environment. • Evacuated solar collectors achieve lower pay back periods equal to 3.52 years. [ABSTRACT FROM AUTHOR]

Abstract This work aims at presenting the current works concerning the polygeneration systems simulation, by specially focusing on the potential integration of different technologies into a single system. Polygeneration allows one to produce energy vectors (power, heating and cooling) as wells as other useful products (hydrogen, syngas, biodiesel, fertilizers, drinking water etc.) by converting one or multiple energy sources. Polygeneration system can be fuelled by renewable sources (geothermal, solar, biomass, wind, hydro), as well as fossil fuels (natural gas, coal, hydrogen, etc.). In this paper innovative energy technologies, such as fuel cells and conventional ones are taken into account, by also focusing on the control strategies implemented for the proper management of polygeneration systems in general. Works regarding energy, economic and exergy analyses and system optimizations are also illustrated. Highlights • Current literature studies on polygeneration systems simulation. • The review includes conversion technologies fuelled by fossil and/or renewable energy. • A classification of methodology, outputs, control and optimization. • Contribution of polygeneration to the development of distribute generation systems. [ABSTRACT FROM AUTHOR]

In this work, a dynamic model of a high-temperature integrated solar combined cycle power plant is presented. The system includes a three-pressure combined cycle power plant coupled to parabolic trough solar collectors. Thermal storage, a heat solar steam generator, pumps, heat exchangers, and several controllers are also included in the system. Solar energy is used to produce additional steam to be supplied to the steam turbine of the combined cycle power plant. The integrated solar combined cycle system is based on the heat transfer fluid arrangement, exploiting solar energy to produce steam. The analysis is developed by a dynamic simulation model including detailed algorithms for the calculation of the performances of system components. Special control strategies are included in the model in order to accurately manage the steam production of the heat solar steam generator. The paper presents a thermo-economic and environmental comparison between the integrated solar combined cycle and a conventional combined cycle, powered by fossil fuels, based on dynamic simulations. A case study, referred to a plant with a maximum power of around 100 MW, located in Almeria (Southern Spain), is presented and discussed. A parametric analysis was also performed to show the effect of the variation of total solar field reflector area on the system performance. For the case under evaluation, a simple pay-back of 15 years was found, for a solar field aperture area of 80 000 m 2 ; however, the parametric analysis suggests that a smallest solar field area should be used under the hypotheses of the case study. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel high-temperature solar assisted triple-pressure level combined cycle power plant. The system includes innovative high-temperature flat plate evacuated solar thermal collectors, a double stage lithium bromide/water absorption chiller, pumps, heat exchangers, storage tanks, mixers, diverters, controllers and a triple-pressure combined cycle power plant. This novel layout uses high-vacuum non-concentrating flat plate solar thermal collectors driving a double effect absorption chiller, leading to an overall high coefficient of performance for the solar cooling section. The provided cooling energy is used to cool gas turbine inlet air to enhance system efficiency and electrical capacity. This effect is mainly performed during central hours of the day when the conventional gas-fired combined cycles dramatically suffer for efficiency and capacity reduction, as a consequence of the corresponding increase of external air temperature. Such increase is related to the higher availability of solar radiation. This technology may be a viable solution, especially for hot and dry areas, in terms of primary energy savings and increased revenues. This prototypal system was numerically analysed for a combined cycle with a rated electrical power of 99 MWe and an electrical efficiency of 56%, developing a dynamic simulation model and detailed thermo-economic optimizations. Special attention is also paid to the design of novel control strategies aiming at maximizing the solar cooling effect. The results of the dynamic simulations show a very high average thermal efficiency of the solar collectors, equal to 34%. Implications of the performed work allowed an increase of the power output up to 5.5% and a satisfactory payback period equal to 10.7 years. [ABSTRACT FROM AUTHOR]

This work presents a thermo-economic simulation model of a hybrid renewable power plant based on wind turbine and photovoltaic technologies, coupled to an energy storage system. The total plant capacity is 200 kW (190 kW and 10 kW, for photovoltaic and wind turbine, respectively), whereas the energy storage capacity is 400 kWh. Aim of this work is to design a renewable power plant showing limited fluctuations (with respect to the ones typically achieved in case of solar systems) with marginal amounts of electricity purchased or sold to the grid, maximizing the electricity self-consumption. The thermo-economic model, developed in TRNSYS environment, allows one to determine the best system configuration and maximize the economic profitability by considering the time-dependent tariffs applied to the electricity exchanged with the grid and the possibility to store electricity. Different system layouts with or without the storage system and for different users are considered. Results show negative profit indexes of the layouts including the storage system (−0.27 in the worst case vs. 0.61 in the best case without the storage), due to its lower efficiency and its higher capital cost, although a remarkable reduction of the operating costs and an enhancing of the self-consumed energy. [ABSTRACT FROM AUTHOR]

The current applications in the energy sector are based largely on fossil fuels which release greenhouse gas emissions to the atmosphere. To face the issue of global warming, the energy sector has to transfer to and develop sustainable energy solutions that do not release carbon emissions. This is one of the primary motivators for the SDEWES conference as well as for this review, and previous ones, examining the most recent works based on sustainable and green energy production in such fields. The 17th Conference on the Sustainable Development of Energy, Water, and Environment Systems (SDEWES) was held on 6–10 November 2022 in Paphos, Cyprus. The SDEWES conference aims at solving complex and ongoing concerns that approach a long-term perspective and supporting innovative solutions and continuous monitoring and evaluation. This review paper aims at collecting the main presented papers focused on the following hot topics: low-carbon technologies based on renewable and clean-energy systems, including mainly biomass, solar, and wind energy applications; energy storage systems; hydrogen-based systems; energy-saving strategies in buildings; and the adoption of smart management strategies using renewable energy systems. These topics are investigated in order to propose solutions to address the issues of climate change, water scarcity, and energy saving. From the analyzed works, we note that some key issues for sustainable development remain to be further addressed: such as novel and advanced energy storage systems, green hydrogen production, novel low-temperature district heating and cooling networks, novel solar technologies for the simultaneous production of power and high temperature heat, solar desalination for hydrogen production systems, and agrivoltaic systems for the production of power and food. [ABSTRACT FROM AUTHOR]

Solar heating and cooling systems are a promising technology which may significantly contribute to the reduction of greenhouse gas emissions, the enhancement of energy efficiency, and the increase of renewables share in the building sector. The available literature show a high number of papers aiming at investigating solar heating and cooling systems based on heat driven and solar technologies, configurations, operating strategies, and financing issues. Nevertheless, none of the papers available in literature investigates the possibility to replace conventional solar thermal collectors by flat plat and concentrating photovoltaic/thermal systems, also producing renewable electricity. To cover this lack of knowledge, in this paper a dynamic simulation model of novel solar polygeneration heating and cooling systems is presented. Such dynamic simulation model is developed and implemented in a computer code, written in MatLab, and allows investigating the energy, economic and environmental performance of such novel solar polygeneration systems, based on both adsorption and absorption chiller technologies fed by dish-shaped concentrating and flat photovoltaic/thermal collectors. In order to show the potentiality of the presented tool, a comprehensive parametric case study is carried out to find out the optimal system configurations, as a function of crucial design and operating parameters and of weather conditions. The presented case study analysis refers to a small cluster of four buildings, including office and residential spaces, located in different European weather zones. The modelled solar polygeneration systems simultaneously produce electricity, space heating and cooling, and domestic hot water; electricity is self-consumed or delivered to the electrical grid. For comparative purposes, two different back-up system configurations, based on an electric chiller and a condensing gas-fired heater are also taken into account as conventional reference building-plant systems. By means of this systematic parametric analysis, comprehensive guidelines for system designers, practitioners and/or researchers focused on the development and use of solar heating and cooling systems are provided. [ABSTRACT FROM AUTHOR]

In this paper a thermoeconomic analysis of a novel hybrid Renewable Polygeneration System connected to a district heating and cooling network is presented. The plant is powered simultaneously by solar and geothermal sources, producing electricity, desalinated water, heat and cooling energy. System layout includes Parabolic Through Collector (PTC) field, geothermal wells, Organic Rankine Cycle (ORC) unit and a Multi-Effect Desalination (MED) system. Cooling and thermal demands are calculated by suitable building dynamic simulation models, calibrated for Pantelleria Island. Electrical demand is obtained by measured data. A detailed control strategy has been implemented in order to prevent any heat dissipation, to match the appropriate operating temperature levels in each component, to avoid a too low temperature of geothermal fluid reinjected in the wells and to manage the priority of space heating and cooling process. A 1-year dynamic simulation has been performed and results analyzed on daily, monthly and yearly basis. The system achieved an SPB equal to 8.50 and it resulted capable to cover the energy demands of a small community. Moreover, the plant is capable to cover the fresh water demand of the Pantelleria Island. [ABSTRACT FROM AUTHOR]

This work focuses on a dynamic simulation model for the energy, economic and environmental analysis of an innovative polygenerative system layout based on a building integrated photovoltaic thermal system coupled to an adsorption chiller and to an electricity storage system. The thermal energy of building integrated photovoltaic thermal collectors is exploited in order to produce solar space heating and cooling and domestic hot water. Auxiliary electric air-to-water heat pumps/chillers and a gas-fired condensation boiler are included in the system model in order to integrate the demands of heating, cooling and domestic hot water production. The electricity produced by building integrated photovoltaic thermal collectors is used to satisfy the building needs. The eventual extra-production is delivered to the grid or stored in lead-acid batteries. By means of the developed dynamic simulation model (implemented in TRNSYS environment) the energy system performance on the whole building can be analysed in terms of heating/cooling energy, electricity and domestic hot water demands. In particular, both the passive and active energy effects of the investigated collectors can be assessed. The model includes a suitable tool for the comparison of the innovative system layout vs. traditional reference building-plant systems. For energy, economic and environmental impact optimization purposes, sensitivity analyses can be performed by varying the main system design parameters with respect to the value of reference case ones. In order to show the potentiality of the developed simulation model, several new case studies are developed. They refer to a 3-floor office building located in four different Italian weather zones. Simulation results show that the obtained SPBs, the primary energy saving for electricity and domestic hot water production, and the equivalent carbon dioxide avoided emissions range between 10.6–11.3 years, 58.5–68.8% and 76.3–90.2%, respectively. [ABSTRACT FROM AUTHOR]

In this paper a dynamic simulation model and a thermo-economic analysis of a novel polygeneration system are presented. The system includes photovoltaic/thermal collectors coupled with a solar-assisted heat pump, an adsorption chiller and an electrical energy storage. The modelled plant supplies electrical energy, space heating and cooling and domestic hot water. The produced solar thermal energy is used during the winter to supply the heat pump evaporator, providing the required space heating. In summer, solar thermal energy is used to drive an adsorption chiller providing the required space cooling. All year long, solar thermal energy in excess, with respect to the space heating and cooling demand, is used to produce domestic hot water. The produced electrical energy is self-consumed by both user and system auxiliary equipment and/or supplied to the grid. The system model includes a detailed electrical energy model for user storage and exchange with the grid along with a detailed building model. This study is a continuation of previous works recently presented by the authors. In particular, the present paper focuses on the real electrical demands of several types of users and on the analysis of the comfort of building users. Differently from the works previously published by the authors, the present work bases the calculations on measured electrical demands of real users (fitness center and offices). The system performance is analyzed with two different electricity supply contracts: net metering and simplified purchase/resale arrangement. Daily, weekly and yearly results are presented. Finally, a sensitivity analysis is performed in order to determine the system performance as a function of the system main design/control parameters and to evaluate the minimum Simple Pay-Back period. The results outlined a share of the electrical energy storage system on the self-consumed electrical energy of about 20%. The economic profitability is better in case of net metering contract compared to the simplified purchase/resale arrangement one. Moreover, a Simple Pay-Back of about 15 years is achieved for the best configuration, decreasing to 5.6 years in case of capital investment incentive of 65%. The best system configuration, in terms of solar field area, for the fitness center user ranges from 250 to 300 m 2 . [ABSTRACT FROM AUTHOR]

In this paper, a detailed numerical analysis of a Combined Cooling, Heating and Power system is presented, aiming at determining its optimal operating strategy in a real industrial application. The system layout includes a reciprocating engine, fuelled by natural gas, heat exchangers for waste-heat recovery, pumps, storage tanks, a single-effect water lithium bromide absorption chiller, a cooling tower, a back-up vapour-compression electric chiller, mixers and valves. A dynamic simulation model of the whole system was developed in TRNSYS. A case study was analysed, referred to a real industrial application, where the system under evaluation should be installed in the near future, providing electricity, mainly used for the production process, and space cooling. Real measured data were used to estimate the electric energy demand of the factory. A detailed building simulation model was used to calculate heating and cooling demands. A detailed economic analysis was carried out, aiming at evaluating: (i) the optimal size of the Combined Cooling, Heating and Power system; (ii) the optimum control strategy, from a thermo-economic point of view, comparing three different cases: Base-Load operation, electric load tracking and a new hybrid strategy based on the simultaneous tracking of electric and thermal-loads. The results showed that the optimal capacity of the system was lower than that selected by the designers of the real unit to be installed. The hybrid control strategy obtained the best profitability, achieving a simple pay-back period equal to 3.8 years, compared to 4.1 years achieved in case of electric-load tracking. [ABSTRACT FROM AUTHOR]

Energy policies accompanying the transition towards a sustainable development process must be supported by technical analyses in which future energy scenarios are modeled and evaluated. This paper analyzes possible decarbonization scenarios in Italy for the year 2050. They envisage high electrification of transports and residential buildings, high use of renewable energies, and a modal shift towards public transport. The energy scenarios are evaluated using a software program, EnergyPLAN, starting from a reference model developed for the year 2014. Special attention has been given to the modeling of data that are unavailable in the literature, such as the time profile of heating and cooling demands, obtained with the degree-days method and validated by elaborating the results of the modeling of the residential building stock, this latter was dynamically simulated in TRNSYS. The results show that to obtain a significant decrease of greenhouse gas emissions and fossil fuel consumption, it is necessary not only to promote a deeper penetration of renewable sources, but also their integration with other technologies (cogeneration, trigeneration, power-to-heat systems, thermal storage, vehicle-to-grid operations). In fact, renewables technologies alone can raise some critical issues, such as excess and/or shortage of electricity production and non-sustainable exploitation of biomass. [ABSTRACT FROM AUTHOR]

This paper presents the design of a novel Solar Assisted Combined Cycle power plant. The system includes a solar loop equipped with a double stage absorption chiller driven by high-temperature high-vacuum non-concentrating flat-plate solar thermal collectors. The solar loop is coupled to a single-pressure Combined Cycle power plant. The cooling energy produced by the absorption chiller is used to cool gas turbine inlet air, aiming at enhancing system efficiency and electrical capacity. This Solar Assisted Combined Cycle arrangement is analysed through a dynamic system simulation and a thermoeconomic analysis is also performed aiming at determining the optimal set of design and operating parameters. The paper has the objective to prove the technical, energetic and economic feasibility of this technology, especially for hot and dry areas, with respect to other alternative air cooling configurations. In addition, solar collectors operating temperatures are high enough to drive a two stage absorption chiller, showing a Coefficient of Performance roughly two times higher than the one of a conventional single stage absorption chiller. This original configuration was numerically analysed in TRNSYS environment, developing a suitable dynamic simulation model in order to predict system performances. Suitable dynamic models are implemented for all the components included in the system. Special attention is also paid to the design of novel control strategies aiming at maximizing the utilization of solar energy for cooling purposes. In particular, a special control strategy managing cooling water flow is implemented in order to limit as much as possible water condensation within the cooling coil. The simulation also includes a detailed thermoeconomic model which accurately evaluates system capital and operating costs as a function of design and operating parameters. The simulations results show that a very high thermal efficiency of solar collectors, on average equal to 34%, is achieved. Results from the economic point of view were also satisfactory. In fact, the pay back period was about 8 years in the best case. Finally, in order to analyse the effects of the variation of the main design parameters, a parametric analysis is also presented. Such analysis shows that high solar radiation and low ambient humidity are crucial in order to achieve acceptable economic profitability indexes. [ABSTRACT FROM AUTHOR]

• Development of a novel approach for studying and addressing the issue of heat theft. • Definition of a novel vote parameter assessing for which penalty the heat theft is profitable. • A penalty up 2.5 times the constant fee would limit unwanted behavior of heat theft. • The constant fee should account for 40–60% of the total energy bill. European Union is facing a dramatic energy crisis, due to the huge increase of the natural gas cost, due to the Russian-Ukrainian war. In this framework, the fair allocation of natural gas costs, used for space heating purposes in residential centralized heating systems, is becoming a crucial issue. These systems suffer for the heat theft phenomenon, where an unheated apartment may benefit of the heat transfer from the surrounding heated apartments. Unfortunately, there is no consensus regarding a suitable heat accounting method, implemented in order to limit heat thefts. In this work, two novel billing strategies are proposed. In the first one, the heating cost includes both a variable fee and a constant fee. The second one also considers a penalty for the unheated apartments. A case study is analyzed. It consists of a multifamily building including 4 floors and located in Naples. This building is equipped with a centralized heating system, coupled with radiators, variable speed pumps, thermostatic valves, and heat metering devices. A suitable dynamic simulation model is developed in TRNSYS 18 environment to analyze the energy and economic performance of the system. The comfort parameters of unheated users are also analyzed and discussed. The proposed billing strategies are able to smooth the heating bill increase for the heated apartments adjacent to the unheated user. The novel billing strategy proposed by this research can significantly mitigate the heat theft issue. In particular, results show that the penalty should be almost 2.5 times the constant fee for preventing the unheated user issue. Simulations also show that installing a suitable thermal insulation for the walls among adjacent apartments may dramatically limit the heat thefts. However, insulating such walls may result often unfeasible for the owners of the apartments, due to reduction of the floor area and to the major refurbishment required. [ABSTRACT FROM AUTHOR]

In the field of primary energy saving, biomethane is becoming more and more attractive. The need to manage urban waste, combined with the increasing use of biofuels, makes this resource crucial for sustainability objectives. Therefore, a detailed estimation of biogas production from an anaerobic digester is an important aspect for the related research activity. This work presents a thermal transient model developed in MATLAB® that can accurately predict heat transfer and biological phenomena occurring within the digester. The model developed in this paper can conveniently consider the thermal inertia of the treated biomass during the retention time. This model is subsequently linked to the TRNSYS environment, where the produced biogas is upgraded to biomethane. For this purpose, a membrane permeation model is considered. A concentrating photovoltaic/thermal collector is coupled to the digester to meet the plant electricity and thermal energy demands. In particular, the electricity demand is mainly due to the upgrading process while the thermal energy is necessary for the anaerobic digestion process. The results of the dynamic analysis show that neglecting the thermal inertia of the digester leads to an overestimation of the total biogas production by 20%. Furthermore, the integration of renewables with the anaerobic digestion process shows remarkable results. In this case study, the Primary Energy Saving is roughly 5% and the Simple-Pay Back is less than 10 years, despite the small scale selected for solar collectors. • The thermal transient affects the time needed to get the steady-state conditions. • In a yearly dynamic simulation, the total biogas production is roughly 20% lower. • CPVT collectors are not a feasible solution to meet the energy needing. • Incentives for the systems proposed lead to profit index of 68% and 92%. [ABSTRACT FROM AUTHOR]

This paper presents a detailed numerical analysis of a trigeneration system serving a hospital, aiming at determining the best economic operating strategy. In this paper, a novel approach is presented aiming at developing a detailed tool to be used to predict the real time performance of the trigeneration system and to optimize its operation designing efficient control strategy. To this scope, a detailed dynamic simulation model was developed in TRNSYS environment. The simulated system provides electrical, thermal and cooling energy. It includes: a natural gas fired reciprocating engine, heat exchangers for waste-heat recovery, a single-stage LiBr-H 2 O Absorption Chiller (ACH), a cooling tower, pumps, a backup boiler, a backup vapor-compression electric chiller, storage tanks, valves, mixers. For such components, suitable control strategies and detailed algorithms were implemented in order to develop a model as much realistic as possible. To this scope, cooling and thermal loads were estimated by implementing detailed building dynamic simulations strictly related to the trigeneration system model. Three different operating strategies were evaluated in order to minimize the plant cost and maximize the performance of the system, namely: Thermal Load Tracking mode (TLT), Maximum Power Thermal Load Tracking mode (MPTLT) and Electricity Load Tracking mode (ELT). In the first one (MPTLT), the thermal power provided by the engine is always lower or equal to the thermal demand; in the second one (TLT), the engine operates according to an On/Off strategy; in the third one (ELT), the electrical power provided by the engine is always lower or equal to the electrical demand. The results of the case study were presented on different time bases (days, weeks, years). Such results show that the ELT control strategy can achieve a better profitability, with a simple payback period, SPB, equal to 4 years. For this strategy, 256 simulations were also performed by varying the main model parameters, in order to determine the combination showing the lowest SPB value and the highest Primary Energy Saving (PES) value. The optimum and the analysis of the optimum response surface was obtained by using Design of Experiments (DoE) method, showing that the best SPB value, equal to 3.9 years, comes out choosing an engine capacity ratio equal to 1, an ACH capacity ratio equal to 1, a hot tank volume equal to 5 m 3 and a cold tank volume equal to 2 m 3 . The best PES value, instead, is equal to 20.6% and comes out selecting an engine capacity ratio equal to 0.5, an ACH capacity ratio equal to 1, a hot tank volume equal to 6 m 3 and a cold tank volume equal to 2 m 3 . [ABSTRACT FROM AUTHOR]

This paper presents a dynamic simulation model and an energetic and economic analysis of novel polygeneration system. The system integrates: cogenerative Proton Exchange Membrane Fuel Cell (PEMFC), Concentrated PhotoVoltaic-Thermal (CPVT) collectors, alkaline electrolyzer and single-stage LiBr/H 2 O absorption chiller. The plant is designed to supply electrical energy, space heating or cooling and domestic hot water for a small university building. The system produces hydrogen and oxygen, the first one is stored and then it is supplied to the fuel cell, while the second one is sold. The electrolyzer system is powered only by the CPVT collectors, only a small amount of the solar electrical energy is available to the user. Such electric energy along with the one produced by the PEM fuel cell are used by the user and/or supplied to the grid. The system is designed and dynamically simulated using TRNSYS software package. This study is based on a model previously developed by the authors. In particular, the system was modified in order to implement the new components (CPVT, alkaline electrolyzer, hydrogen and oxygen system) in this work. Special attention is paid to the control strategy of the proposed system in order to achieve the optimal system configuration. Daily, weekly and yearly results carried out with the dynamic simulation are presented. Finally, a sensitivity analysis was performed in order to determine the system performance as a function of the main design parameters. The energetic and economic analysis shows that the system can ensure significant energy savings and it can be profitable in presence of a capital investment incentive. The total energy efficiency of the CPVT collectors, calculated with respect to the beam radiation, is above 80% and the fuel cell electrical and thermal efficiencies resulted 35.0% and 43.4%, respectively. The hydrogen production of the electrolyzer system covers 4.3% of the fuel cell hydrogen demand. The Simple Pay Back period, in case of incentive, results of about 5 years when the optimal FC nominal power of 100 kW is selected. [ABSTRACT FROM AUTHOR]

This paper presents a one-dimensional finite-volume model of an unglazed photovoltaic/thermal (PVT) solar collector. The unit consists of a conventional solar photovoltaic (PV) collector coupled with a suitable heat exchanger. In particular, the collector includes a roll bond heat exchanger and it is not equipped with back and frame insulation. The system is discretized along the flow direction (longitudinal) of the cogenerative collector. For each finite-volume element of the discretized computational domain, mass and energy balances are implemented. The collector geometry and materials parameters are taken from a commercially available device. An on-field experimental investigation is performed in order to validate the proposed model. The model is used to evaluate both electrical and thermodynamic parameters for each element of the domain and for fixed operating conditions. Finally, a sensitivity analysis is also performed in order to investigate the energetic performance of the cogenerative collector as a function of the main design/environmental parameters. [ABSTRACT FROM AUTHOR]

This paper analyses the energy and economic performance of roof and/or façades Building Integrated flat-plate PhotoVoltaic and Thermal (BIPVT) collectors for residential applications. Aim of the analysis is to assess the active and passive effects due to the building integration of solar technologies on the building energy consumptions. In particular, a comparison among innovative building-plant system configurations, based on BIPVT collectors for the simultaneous production of electricity, thermal energy, and domestic hot water, is carried out. The simulation models of the proposed system layouts are designed and implemented in TRNSYS simulation environment for the dynamic assessment of their energy and economic performance. By means of the developed simulation model, the occurring summer and winter building passive energy effects due to the PVT building integration are also analysed. Several case studies are developed by modelling a representative multi-storey residential building and by taking into account different European climates. For such case studies a suitable energy parametric analysis is performed by varying the thermal resistances and capacitances of the building envelope. By the simulation results interesting design and economic feasibility guidelines are obtained. In particular, by varying the weather location and the building-plant configuration, the adoption of BIPVT panels produces a decrease of the primary energy demands from 67% to 89%. The passive effects of the BIPVT system in both the winter and summer season are also assessed for all the investigated climate zones. The calculated economic profitability resulted slightly better for roof BIPVT panels than for roof and façade applications. For the investigated case studies, the pay back periods appear quite long, varying from 11 years for South European weather zones to 20 for North European ones. [ABSTRACT FROM AUTHOR]

In this paper, an innovative solar-geothermal polygeneration system is investigated. The system supplies a small community with electricity, desalinated water and space heating and cooling through a district network. The hybrid multi-purpose plant, based on an Organic Rankine Cycle (ORC) supplied by medium-enthalpy geothermal energy and by solar energy; this latter is provided by Parabolic Trough Collectors (PTC). The geothermal brine is first used to drive the ORC loop, then to provide space heating at around 85÷90 °C (in the winter), or cooling (in the summer, by means of a single-effect absorption chiller). Finally, the geothermal brine drives a Multi-Effect Distillation (MED) system, where seawater is converted into freshwater. For such a system, a dynamic simulation model was developed in TRNSYS environment. In particular, the ORC model, developed in Engineering Equation Solver (EES), was based on zero-dimensional energy and mass balances and includes specific algorithms to evaluate the off-design performance. Similarly, a novel model of the MED unit was developed in EES. Suitable control strategies were implemented for the optimal management of system. The energy and economic performance of the system under analysis was investigated, using different time bases (day, week, month, year). Finally, a sensitivity analysis was performed to determine the set of system, design/control parameters able to minimize the simple payback period. The results showed that the novel system is highly flexible and efficient. On the other hand, a significant capital cost must be taken into account, so that the system is economically profitable only when the majority of the energy available for heating and cooling purposes is actually used. [ABSTRACT FROM AUTHOR]

This Special Issue aims at collecting the recent studies dealing with polygeneration systems, with a special focus on the possible integration of different technologies into a single system, able to convert one or multiple energy sources into energy services (electricity, heat and cooling) and other useful products (e.g., desalinized water, hydrogen, glycerin, ammonia, etc.). Renewable sources (solar, wind, hydro, biomass and geothermal), as well as fossil fuels, feeding advanced energy systems such as fuel cells and cogeneration systems, are considered. Special attention is paid to control strategies and to the management of the systems in general. Studies including thermoeconomic analyses and system optimizations are presented. [ABSTRACT FROM AUTHOR]

This paper presents a detailed exergetic analysis of a novel high-temperature Solar Assisted Combined Cycle (SACC) power plant. The system includes a solar field consisting of innovative high-temperature flat plate evacuated solar thermal collectors, a double stage LiBr-H2O absorption chiller, pumps, heat exchangers, storage tanks, mixers, diverters, controllers and a simple single-pressure Combined Cycle (CC) power plant. Here, a high temperature solar cooling system is coupled with a conventional combined cycle, in order to pre-cool gas turbine inlet air in order to enhance system efficiency and electrical capacity. In this paper, the system is analyzed from an exergetic point of view, on the basis of an energy-economic model presented in a recent work, where the obtained main results show that SACC exhibits a higher electrical production and efficiency with respect to the conventional CC. The system performance is evaluated by a dynamic simulation, where detailed simulation models are implemented for all the components included in the system. In addition, for all the components and for the system as whole, energy and exergy balances are implemented in order to calculate the magnitude of the irreversibilities within the system. In fact, exergy analysis is used in order to assess: exergy destructions and exergetic efficiencies. Such parameters are used in order to evaluate the magnitude of the irreversibilities in the system and to identify the sources of such irreversibilities. Exergetic efficiencies and exergy destructions are dynamically calculated for the 1-year operation of the system. Similarly, exergetic results are also integrated on weekly and yearly bases in order to evaluate the corresponding irreversibilities. The results showed that the components of the Joule cycle (combustor, turbine and compressor) are the major sources of irreversibilities. System overall exergetic efficiency was around 48%. Average weekly solar collector exergetic efficiency ranged from 6.5% to 14.5%, significantly increasing during the summer season. Conversely, absorption chiller exergy efficiency varies from 7.7% to 20.2%, being higher during the winter season. Combustor exergy efficiency is stably close to 68%, whereas the exergy efficiencies of the remaining components are higher than 80%. [ABSTRACT FROM AUTHOR]

In the paper, a model for the simulation and the optimization of a novel solar trigeneration system is presented. The plant simulation model is designed to supply electricity, space heating or cooling and domestic hot water for a small residential building. The system is based on a solar field equipped with flat-plate photovoltaic/thermal collectors, coupled with a water-to-water electric heat pump/chiller. The electrical energy produced by the hybrid collectors is entirely supplied to the building. During the winter, the thermal energy available from the solar field is used as a heat source for the evaporator of the heat pump and/or to produce domestic hot water. During the summer, the heat pump operates in cooling mode, coupled with a closed circuit cooling tower, providing space cooling for the building, and the hot water produced by the collectors is only used to produce domestic hot water. For such a system, a dynamic simulation model was developed in TRNSYS environment, paying special attention to the dynamic simulation of the building, too. The system was analyzed from an energy and economic point of view, considering different time bases. In order to minimize the pay-back period, an optimum set of the main design/control parameters was obtained by means of a sensitivity analysis. Simultaneously, a computer-based Design of Experiment procedure was implemented, aiming at calculating the optimal set of design parameters, using both energy and economic objective functions. The results showed that thermal and electrical efficiencies are above 40% and 10%, respectively. The coefficient of performance of the reversible heat pump resulted above 4 for both heating and cooling modes. For the base case, a Simple Pay Back period of 5.36 years was found; such index decreases to 2.33 years in case a capital investment incentive of 30% is available. As expected, a decrease of the performance of the system was detected for weather conditions in which the availability of solar energy is scarce. The Design of Experiments analysis outlined that the appropriate selection of collector area is crucial in order to achieve a good profitability of the system under analysis. [ABSTRACT FROM AUTHOR]

In this paper a new simulation model of a novel solar heating and cooling system based on innovative high temperature flat plate evacuated solar thermal collector is presented. The system configuration includes: flat-plate evacuated solar collectors, a double-stage LiBr-H2O absorption chiller, gas-fired auxiliary heater, a closed loop cooling tower, pumps, heat exchangers, storage tanks, valves, mixers and controllers. The novelty of this study lies in the utilization of flat-plate stationary solar collectors, manufactured by TVP Solar, rather than concentrating ones (typically adopted for driving double-stage absorption chillers). Such devices show ultra-high thermal efficiencies, even at very high (about 200 °C) operating temperatures, thanks to the high vacuum insulation. Aim of the paper is to analyse the energy and economic feasibility of such novel technology, by including it in a prototypal solar heating and cooling system. For this purpose, the solar heating and cooling system design and performance were analysed by means of a purposely developed dynamic simulation model, implemented in TRNSYS. A suitable case study is also presented. Here, the simulated plant is conceived for the space heating and cooling and the domestic hot water production of a small building, whose energy needs are fulfilled through a real installation (settled also for experimental purposes) built up close to Naples (South Italy). Simulation results show that the investigated system is able to reach high thermal efficiencies and very good energy performance. Finally, the economic analysis shows results comparable to those achieved through similar renewable energy systems. [ABSTRACT FROM AUTHOR]

This paper presents numerical and experimental analyses aimed at evaluating the technical and economic feasibility of photovoltaic/thermal (PVT) collectors. An experimental setup was purposely designed and constructed in order to compare the electrical performance of a PVT solar field with the one achieved by an identical solar field consisting of conventional photovoltaic (PV) panels. The experimental analysis also aims at evaluating the potential advantages of PVT vs. PV in terms of enhancement of electrical efficiency and thermal energy production. The installed experimental set-up includes four flat polycrystalline silicon PV panels and four flat unglazed polycrystalline silicon PVT collectors. The total electrical power and area of the solar field are 2 kWe and 13 m², respectively. The experimental set-up is currently installed at the company AV Project Ltd., located in Avellino (Italy). This study also analyzes the system from a numerical point of view, including a thermo-economic dynamic simulation model for the design and the assessment of energy performance and economic profitability of the solar systems consisting of glazed PVT and PV collectors. The experimental setup was modelled and partly simulated in TRNSYS environment. The simulation model was useful to analyze efficiencies and temperatures reached by such solar technologies, by taking into account the reference technology of PVTs (consisting of glazed collectors) as well as to compare the numerical data obtained by dynamic simulations with the gathered experimental results for the PV technology. The numerical analysis shows that the PVT global efficiency is about 26%. Conversely, from the experimental point of view, the average thermal efficiency of PVT collectors is around 13% and the electrical efficiencies of both technologies are almost coincident and equal to 15%. [ABSTRACT FROM AUTHOR]

• Optimization of a 5th generation district heating and cooling network. • Two bidirectional low-temperature rings cooled by seawater heat exchangers. • High payback period of about 15 years due to the high capital cost of heat pumps. • The renewable production of solar and wind field meets 57% of the district demand. This work presents the design and the thermo-economic optimization of a novel layout of a 5th generation district heating and cooling network, for a residential district located in the Pantelleria island (South of Italy). The research focuses on a novel arrangement based on two bidirectional low-temperature neutral rings. For both rings, the fluid temperature is controlled by means of two groups of heat pumps cooled by seawater. The investigated layout also includes wind turbines and photovoltaic panels for power production. This layout will be used as a driver to promote the transition from the present centralized energy paradigm to a novel one, based on small-scale distributed generation integrated with renewables. The paper aims at evaluating the energy, economic and environmental savings achieved by this novel layout. A thermo-economic optimization is also implemented in order to determine the set of design/operating variables, maximizing system economic profitability. To this scope, a detailed approach is implemented, developing a dynamic simulation model of the system in TRNSYS 17. The developed simulation tool is able to mimic the real time operation of the system, for whatever weather condition, boundary and/or design variable. The results of the simulations show that the proposed layout achieves significantly positive results, with a primary energy saving and avoided greenhouse gases emissions equal to 133% and 134%, respectively. The economic profitability of the system is limited with the payback period close to 15 years, due to the high capital cost of the plant. The renewable electric production of the plant meets 57% of the district demand, although only 37% of this amount is self-consumed by the district. The study also includes a sensitivity analysis suggesting to limit the capacities of solar and wind fields to reduce the electricity in excess sold to the grid. [ABSTRACT FROM AUTHOR]

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 h ex , 0.01612–0.01702 €/kW h ex and 0.5695–0.6023 €/kW h ex . [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical analyses of a novel high-temperature solar cooling system based on innovative flat-plate evacuated solar thermal collectors (SC). This is the first solar cooling system, including a double-effect absorption chiller, which is based on non-concentrating solar thermal collectors. The aim of the paper is prove the technical and economic feasibility of the system, also presenting a comparison with a conventional technology, based on concentrating solar thermal collectors. To this scope, an experimental setup has been installed in Saudi Arabia. Here, several measurement devices are installed in order to monitor and control all the thermodynamic parameters of the system. The paper presents some of the main results of this experimental campaign, showing temperatures, powers, energies and efficiencies for a selected period. Experimental results showed that collector peak efficiency is higher than 60%, whereas daily average efficiency is around 40%. This prototypal solar cooling system has been numerically analysed, developing a dynamic simulation model aiming at predicting system performance. For a representative operating period, numerical data were compared with the experimental one, showing an excellent accuracy of the model. A similar system, equipped with Parabolic Trough solar thermal collectors (PTC) was also simulated in order to compare the novel solar collectors with such reference technology. For both systems a detailed thermo-economic model has been implemented in order to perform such comparison also from the economic point of view. Results showed that the rated energy performance of the prototypal solar cooling system featuring new collectors is better than that of the reference system. In particular, the difference between the novel and the reference solar cooling system becomes more and more significant, when considering the effects of dust and defocusing related to the tracking mechanism of concentrating collectors in harsh environments. Finally, from the economic point of view, results showed that the novel prototype was able to achieve a good profitability. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic simulation model and a thermo-economic analysis of a novel polygeneration system based on a solar-assisted heat pump and an adsorption chiller, both driven by PVT (photovoltaic/thermal) collectors. The aim of this work is to design and dynamically simulate a novel ultra-high efficient solar heating and cooling system. The overall plant layout is designed to supply electricity, space heating and cooling and domestic hot water for a small residential building. The system combines solar cooling, solar-assisted heat pump and photovoltaic/thermal collector technologies in a novel solar polygeneration system. In fact, the polygeneration system is based on a PVT solar field, coupled with a water-to-water electric heat pump or to an adsorption chiller. PVT collectors simultaneously produce electricity and thermal energy. During the winter, hot water produced by PVT collectors primarily supplies the evaporator of the heat pump, whereas in summer, solar energy supplies an adsorption chiller providing the required space cooling. All year long, solar thermal energy in excess is converted into DHW (domestic hot water). The system model was developed in TRNSYS environment. 1-year dynamic simulations are performed for different case studies in various weather conditions. The results are analysed on different time bases presenting energetic, environmental and economic performance data. Finally, a sensitivity analysis and a thermoeconomic optimization were performed, in order to determine the set of system design/control parameters that minimize the simple pay-back period. The results showed a total energy efficiency of the PVT of 49%, a heat pump yearly coefficient of performance for heating mode above 4 and a coefficient of performance of the adsorption chiller of 0.55. Finally, it is also concluded that system performance is highly sensitive to the PVT field area. The system is profitable when a capital investment subsidy of 50% is considered. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review of the possible layout configurations of hybrid power plants based on the integration of solid oxide fuel cells (SOFC) and gas turbine (GT) technologies. SOFC/GT power plants have been investigated by using a plurality of approaches, such as: numerical simulations, experimental analyses, and thermo-economic optimizations. The majority of SOFC/GT hybrid systems are fed by methane, which is much cheaper and easier to manage than hydrogen. In fact, SOFC/GT systems use the capability of the fuel cell to internally perform the reforming process required to convert methane into hydrogen. The steam required to drive the reforming reaction can be supplied by the anode recirculated stream. Alternatively, such steam can be produced externally, by using the heat of the exhaust gases. In this case, steam can be used also for thermal purposes and/or for further system hybridization (e.g. Cheng cycle). The majority of the SOFC/GT power plants analyzed in literature are based on the pressurized arrangement, potentially able to ensure lower capital costs and higher efficiencies. Conversely, atmospheric plants are easier to manage, due to the possibility of operate the SOFC and the GT independently one of each other. The paper also investigates more complex SOFC/GT configurations, including: HAT turbines, IGCC SOFC/GT power plants, ORC cycles, etc. A detailed analysis of the SOFC/GT control strategies and part-load performance analyses is also presented, showing that such systems reach their best performance at nominal capacity, and are affected by significant reduction of the electrical efficiency in case of large variations of the load. Finally, the paper also presents a review of hybrid SOFC/GT power plants fed by alternative fuels, such as coal and biomass. [ABSTRACT FROM AUTHOR]

Nowadays, almost 30% of total energy consumption (130 EJ) is consumed for the operation of buildings, mainly by space heating/cooling and ventilation systems, hot water preparation systems, lighting, and other domestic appliances. To improve the energy efficiency of buildings, several countries are promoting the use of renewable energy. The most promising systems include active and passive solar installations. In passive systems, the solar energy is collected, stored, reflected, or distributed by the roof ponds, natural convective loops, and the most popular direct gain walls and thermal storage walls (known as Trombe walls). This paper reviews the experimental and numerical studies devoted to the different solutions of Trombe walls, including solar chimneys integrated on the vertical walls, classic Trombe walls, Trombe walls with incorporated phase change materials, and photovoltaic Trombe walls. The actual state of the art is presented in the context of reducing energy consumption and enhancing thermal comfort. Most of the analyzed studies showed that the application of thermal storage walls allowed achieving these goals, led to lower emissions of greenhouse gases, and improved living standards. Nevertheless, there is a need for more detailed feasibility studies, including cost and environmental indicators. [ABSTRACT FROM AUTHOR]

Smart energy networks, based on the integration of thermal and electric technologies, are becoming more attractive to match the increasing energy demand with minimum environmental impact. The design and optimization of a smart energy network based on a combined heat and power system, a photovoltaic solar field, an electric energy storage system and electric vehicles is presented in this work. The investigated system is designed to match the power, heating and cooling demands of a district of 50 residential buildings. The cogeneration system, operating in thermal tracking mode, is based on a reciprocating internal combustion engine, fuelled by natural gas. The engine waste heat is used to match the heating and domestic hot water demands of the residential district. The power produced by both engine and photovoltaic panels is used to match the power demand of the district, including the electric vehicles. The electric energy storage system based on lithium-ion technology is included to shave the peaks of power demand and to decouple demand from supply. The whole system, including all final users, was dynamically simulated in TRNSYS 18. The model was used to develop a case study regarding a district of 50 residential buildings located in Naples (South of Italy). A thermoeconomic optimization of the layout was also performed, using Genopt software. The results of the case study showed that the proposed system exhibits promising performance, reducing CO 2 emissions by 62%, with a payback period of 6.39 years. In the optimal scenario, the peak power of the photovoltaic field was found equal to 3.50 MW, with a capacity of the electric energy storage system of 6.70 MWh. The corresponding payback period was equal to 6.31 years. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic simulation model and a parametric analysis of a solar-geothermal hybrid cogeneration plant based on an Organic Rankine Cycle (ORC) powered by a medium-enthalpy geothermal resource and a Parabolic Trough Collector solar field. The fluid temperature supplying heat to the ORC varies continuously as a function of the solar irradiation, affecting both the electrical and thermal energies produced by the system. Thus, a dynamic simulation was performed. The ORC model, developed in Engineering Equation Solver, is based on zero-dimensional energy and mass balances and includes specific algorithms to evaluate the off-design system performance. The overall simulation model of the solar-geothermal cogenerative plant was implemented in the TRNSYS environment. Here, the ORC model is imported, whereas the models of the other components of the system are developed on the basis of literature data. Results are analyzed on different time bases presenting energetic, economic and exergetic performance data. Finally, a rigorous optimization has been performed to determine the set of system design/control parameters minimizing simple payback period and exergy destruction rate. The system is profitable when a significant amount of the heat produced is consumed. The highest irreversibilities are due to the solar field and to the heat exchangers. [ABSTRACT FROM AUTHOR]

In this paper the results of an on-site experimental analysis carried out on a Molten Carbonate Fuel Cell (MCFC) fed by different fuels (hydrogen, landfill gas and different mixtures of them) are presented. The examined MCFC is one of the experimental devices of an innovative power plant located at the urban landfill of Giugliano in Campania (Naples, Italy). Here, electricity is produced through four cogenerative reciprocating engines and one cogenerative gas turbine fed by landfill gas, operating since 2003. At the same site, two different fuel cells are installed for scientific purposes. During the considered experimental campaign, the MCFC is initially supplied by hydrogen for testing the system at the best operating conditions. Afterward, the fuel cell is fed by mixtures of different ratios of hydrogen and reformed landfill gas. For this reason, the system is equipped with an external reformer and a suitable gas cleaning. In order to analyse the system energy performance under varying electricity loads (obtained through an electronic device), several tests were carried out. In addition, several stress tests were also performed aiming at analysing the system endurance when fed by landfill gas. The experimental results concerning the produced electric currents and voltages show satisfactory performance of the system, while the obtained operating temperatures and cell reliability still need to be improved. [ABSTRACT FROM AUTHOR]

During the last years, special attention has been paid to renewable polygeneration technologies, able of simultaneously producing thermal, cooling, electrical energy and desalinated water from seawater. This paper focuses on an innovative polygeneration system driven by renewable energy sources, including the following technologies: hybrid photovoltaic/thermal collectors, concentrating parabolic trough (CPVT), a biomass heater, a single-stage absorption chiller and a multiple-effect distillation desalination system. The system is designed to cover the base load of an isolated small community. In previous papers, the dynamic simulation model about plant operation is discussed. In this paper, a detailed exergy, economic and environmental analysis of the plant is presented. In addition, the plant was optimized using different objective functions, applying the Design of Experiment (DoE) methodology which evaluates the sensitivity of the different objective functions with respect to the selected design parameters. The results show that an increase of the storage volume is generally negative, whereas increasing the solar field area involves an increase of the exergy destruction rate, but also an improvement of the CPVT exergy output provided; the final result is an increase of both the exergy efficiency and the economic profitability of the polygeneration system. [ABSTRACT FROM AUTHOR]