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This paper aims at optimizing the energy performance of an innovative integrated collector-storage solar water heater (ICSSWH) prototype. The system incorporates a high-vacuum gap, which significantly reduces convective thermal losses, and a serpentine absorber system coated with a low-E layer to minimize radiative thermal losses. The methodology is based on a detailed dynamic simulation model, implemented in the MatLab environment, suitable conceived to accurately predict the energy performance and economic profitability of the ICSSWH under various weather conditions and energy market prices. This approach aims to initially identify the most influential geometrical, thermophysical and optical parameters that impact the energy performance of the system through the assessment of different objective functions. After identifying the most influential parameters, the range of existence with the interval step for each variable is defined, and the optimization procedure is conducted to determine the optimal set of variables that maximize / minimize the selected objective functions. To demonstrate the effectiveness of the proposed methodology, a proof of concept was conducted to optimize the energy performance of novel ICSSWH by considering nineteen parameters with the aim of maximizing/minimizing three different objective functions. The results of this analysis yielded various sets of optimized parameters for the ICSSWH.

In this paper a novel Concentrating Photovoltaic/Thermal Glazing system (CoPVTG), developed at the Centre for Sustainable Technologies of the University of Ulster (Belfast, UK), and exploiting concentration technology, is presented and investigated. The innovative device consists in two glazed panels of which the external one is moulded to form several lenses that concentrate the solar radiation onto photovoltaic cells lines. Thanks to the specific behaviour of these lenses, the solar radiation is capable to reach the indoor environment during the winter months (when it's more useful), while it ends onto the photovoltaic cells during the summer months (reducing the solar gains while also providing electricity to the building). To increase the electricity production, a forced air flux can be created inside the glazed cavity to reduce the PhotoVoltaic cells temperature, and the obtained hot air can be exploited for diverse purposes. Finally, such device is conceived to be integrated into existing windows framing to boost its adoption in new or refurbishment construction. With the intention of studying the device under a wide range of boundary and working conditions, a dynamic simulation tool was developed in MATLAB environment and validated trough experimentally gathered data. With this tool it is possible to investigate the performance of the novel device integrated into several buildings. Specifically, a case study analysis was performed by considering an office building located in five different localities. From the conducted analyses, interesting results and design criteria are obtained. Specifically, the CoPVTG adoption returns higher electricity yield vs. standard semi-transparent window, ranging between 54 and 84% in case of cold and hot weather zones, respectively. In term of overall economic performance, the adoption co CoPVTG allow for a HVAC system running cost reduction, for the investigated case study, ranging from 20 to almost 100% depending on the considered weather zone.

Today, the use of renewable energies in buildings represents one of the main ways to reach a sustainable world. Whilst present buildings are still often energivorous systems, in the near future they will have to be converted to (or replaced by) zero energy buildings, also capable to export green energy (produced on-site by renewables) towards other buildings and/or users. This review article focuses on a selection of research papers, presented at the 16th International Conference on Building Simulation (BS 2019), regarding renewable energy applications, energy saving and comfort techniques for buildings. BS 2019 conference was organized in collaboration with the International Building Performance Simulation Association (IBPSA) and it was held at the Angelicum Congress Centre (San Tommaso d’Aquino Pontifex University) in Rome, Italy, during September 2-4, 2019. The conference was attended by 912 researchers and experts, with 660 presented research papers. The above-mentioned selection of papers is included in a dedicated Special Issue of the Renewable Energy - An International Journal (RENE), titled “Renewable energies: simulation tools and applications”. Reported studies are mostly dedicated to models, simulations, and optimization procedures of renewable energy devices. Specifically, photovoltaic systems, building integrated photovoltaic collectors, hybrid photovoltaic/thermal systems, solar thermal collectors as well as other energy efficiency tools are analysed through different simulation approaches and suitable optimization procedures. Attention is also paid to specific case studies related to innovative combinations of renewable energy devices and innovative envelope materials in different building typologies and weather zones. In some papers, solar energy is exploited for space heating and cooling purposes, while in other articles renewables or other energy tools are studied to achieve comfort targets, low grid dependencies, smart building/communities, and mainly the zero energy building goal.

This paper proposes and analyses a novel energy management system for buildings connected in a micro-grid, by considering electric vehicles as active components of such energy scheme. Renewable energy sources, PV, energy storage systems and bidirectional electricity exchange with the buildings and the grid are taken into account. The considered energy scheme, Building to Vehicle to Building, is analysed by including both buildings and mobility consumptions in the energy balance. Three different management system scenarios, designed to analyse the role of electric vehicles as electricity vector among buildings integrating PV panels and electrical storages, are analysed through a case study analysis. To this aim, a dynamic simulation model, implemented in MatLab, is suitably developed for the assessment of the energy demands and loads of the building, as a function of the considered electric vehicles energy use patterns. Simulation results show that the proposed energy management systems improves the building grid reliance and the grid electricity consumption is remarkably reduced up to 45% and 77% depending on the proposed scenarios. Their energy exchange options also enhanced the energy-matching indexes. The economic analysis highlights the economic viability of the system, as well as the need of suitable funding policies to support the development of such micro-grid systems.

Seasonal storage of hydrogen is a valuable option today increasingly considered in order to optimize cogeneration plants under continuous operation in an incentive framework where electricity sale to the national grids is becoming less economically profitable than in the past. The paper concerns the numerical study and optimization of a cogeneration plant installed in an industrial site having an availability of hydrogen over a continuous time scale, to meet the energy needs and mitigating the environmental impact of the plant operation by reducing the energy withdrawal from traditional sources. Two alternatives are analyzed into detail: the former regards energy production through an internal combustion engine, this last properly controlled to be fueled with blends of natural gas and increasing percentages of hydrogen, the latter concerning the addition of fuel cells to the proposed layout to further reduce the electricity integration by the grid. The dynamic response of the cogeneration system under examination is dynamically evaluated to efficiently fulfill the industrial loads to be fulfilled. First, optimization is performed by implementing a PID controller to better track the industrial demand of electric energy. The main results of this solution reveal a −81% reduction of excess electricity, a −7% reduction of natural gas consumed but a 47% raise of CO2 emissions due to the increase in thermal integration. Then, an additional energy generation from fuel cells is assumed. An economic analysis is carried out for each of the implemented configurations. The adoption of fuel cells, despite requiring a greater initial investment, allows obtaining a SPB of 1,4 years (− 16%), 1,17 Mln € of avoided costs (− 18,5%) and 1320 t/year of CO2 emissions avoided (− 95%) with respect to the initial layout.

Nowadays, due to the raising research interest in net and nearly zero-energy concepts at community level, great efforts are spent to investigate self-sustaining and energy-independent communities. Small and off-grid islands represent one of the best places to focus the attention on, and to suit pilot projects of self-sufficient energy communities. In this context, the dynamic simulation represents a useful tool for designing, analysing, and optimizing islands’ energy system layouts, especially in case of renewable energy system adoption (due to the performance unpredictability of renewable energy sources). Therefore, powerful yet flexible dynamic simulation tools are increasingly in demand. In this framework, this paper presents a novel dynamic simulation model, developed in TRNSYS environment, purposely conceived to investigate innovative technologies, novel system layouts, and advanced control logics, in the case of small and off-grid islands, aiming at reaching the nearly/net-zero energy goal at a community level. To prove the potential of the novel dynamic simulation tool, a suitable case study referring to the existing island community of El Hierro (Canary Island) was considered and investigated. Specifically, to enhance the island energy independence, diverse scenarios and system layouts, including different renewable energy based technologies (e.g. wind turbines, hydroelectric power plants, solar thermal collectors, etc.) have been investigated by the novel developed simulation tool. Results demonstrate the potentiality of the adopted method as well as the feasibility of the proposed system layouts. Specifically, the investigated scenarios provide up to 85% of the annual electricity demand and about 79% of the annual thermal energy needs by renewable energy sources with substantial economic savings.

This paper presents a novel dynamic simulation tool able to assess and optimize the energy, environmental and economic performance of standard and innovative district heating/cooling systems. To this aim, several design and operating parameters (e.g.: weather conditions, heat selling price for users, national unitary price of electricity, etc.) are dynamically taken into account. The heating and cooling demands and loads of the buildings to be fed by the network working fluid are dynamically calculated. The system pipeline network is modelled through a suitable plug-flow approach. Fluid temperatures are calculated in each network node. The optimization of several system design and operating parameters is achieved for different objective functions. A suitable analysis is considered for selecting the most convenient urban zones for system application. The whole simulation model is implemented in a suitable computer code written in MatLab. By such tool useful design criteria and feasibility analyses can be obtained. To show the capabilities of the presented simulation tool, a novel case study, referred to a district heating system supplied by an existing thermoelectric power plant, was developed. The conducted analysis is based on system optimizations focused on the number of users, the selling heat/electricity prices and system geometric features. As for example, for minimizing the system payback to about 14.0 year, the optimal number of users and network length are 5 × 103 and 2.7 km, respectively. In this case the primary energy savings and the avoided carbon dioxide emissions are about 11.0 GWh/y and 16.1 ktCO2/y, respectively.

An advanced mathematical model capable of simulating the energy performance of an innovative Integrated Collector Storage Solar Water Heater (ICSSWHs) is presented. Usually, ICSSWH devices available in the market are typically simple and low-cost, combining solar heat collection and storage functions in one unified vessel. However, they exhibit higher heat loss characteristics when compared to standard solar collector systems, with a subsequent reduction in energy performance during night-time and non-collecting hours. An innovative ICSSWH prototype was developed at the Centre for Sustainable Technologies (CST) at Ulster University using a patented, innovative thermal diode feature, attained by incorporating a liquid-vapour phase change material (PCM) and very low pressures. In order to fully investigate the energy performance of the proposed prototype, a suitably dynamic simulation model has been developed and validated in MatLab environment. All modelled temperatures are ±1 °C from the respective experimental measurements. The developed model has been used to evaluate the ICSSWH energy performance by varying several pivotal parameters (physical features and materials) in order to produce an optimised device.

Existing Integrated Collector Storage Solar Water Heaters (ICSSWHs) are typically simple and low-cost devices that combine heat collection and storage functions in one unified vessel. However, during non-collection periods they are affected by higher heat loss characteristics when compared to standard solar collector systems. This paper introduces the design evolution of new horizontal cylindrical ICSSWH prototypes developed at Ulster University that use novel, patented double vessel, thermal diode features (to enhance heat retention during non-collection periods) achieved by incorporating a liquid–vapour phase change material (PCM) with a very low pressure annular cavity. The energy performance evaluation and characterisation of different prototype designs under solar simulated experimental conditions has been conducted and the subsequent parametric analysis presented. A balance between performance and physical/operational considerations is necessary to ensure that new and practical design solutions (in materials, fabrication and assembly) can be formulated to improve the performance of the ICSSWHs within the limits of commercial reality. The importance of augmenting heat transfer across the annulus cavity has been demonstrated with improvement of the cold-start daily collection efficiency from around (ηcol) of 20% (no HTF), to > 55% when the annulus is evacuated to remove non-condensable gases and form a liquid–vapour phase change thermal diode. Annulus thermal diode heat transfer coefficients of around (Ufr) 35 W/m2K in forward mode and 2 W/m2K in reverse mode have been demonstrated. Diurnal thermal efficiencies ( η c o l 24 ) of 22% have been measured, but values of 39% have been identified as achievable in the longer-term development of presented ICSSWH.

The new standards on energy saving for new and existing buildings have animated both researchers and technicians in recent years, aiming at reducing the dependence on fossil fuels, improving indoor comfort, and systems efficiency. In this scenario, special attention must be paid to historical buildings that need to preserve their key testimonial heritage within the society. This paper describes the design and realization stages of a pilot system based on a ground-coupled heat pump, operating both in heating and cooling modes, installed in the monumental site of Saints Marcellino and Festo (SM&F), in Naples, Southern Italy. This study aims to demonstrate that low-enthalpy geothermal systems can be employed as energy retrofit applications in buildings of historical, artistic, and cultural interest and, at the same time, to prove that the use of this technology allows achieving the objectives, set at global level by the current regulations, and requiring a reduction of carbon dioxide emissions (tCO2) of 53% compared to technology using fossil fuels.

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.

To reduce the environmental impact of modern cruise ships, a crucial role is played by the recovery of waste heat from onboard diesel generators used to balance part of the onboard thermal energy demand. To maximize the recovered waste heat, this paper proposes a novel design methodology for ships energy systems based on the dynamic simulation approach, suitably enhanced to consider moving objects like ships. Through this approach, partial load regimes due to variable energy requirements and the relative response of innovative energy saving technologies are dynamically assessed by properly considering real cruising conditions as a function of the current ship position along its route. To this aim, 3-D ship envelope models, detailed energy ship-plant system layouts, and algorithms for deriving new customized hourly weather data files are suitably developed in MatLab and TRNSYS. To show the capability and potentials of the proposed methodology, a novel case study referred to an LNG-powered cruise ship traveling in the Norwegian fjords sea is presented. Different thermally and electrically activated technologies are coupled in 16 energy ship-plant system layouts, implementing novel controls strategies for optimizing the exploitation of the waste heat recoveries and cold-ironing. Encouraging results are achieved for the best layout, including primary energy savings of 18.1%, avoided pollutants emissions of 24.4 ktCO2/y, 40.0 tNOx/y, 90.0 tSOx/y, 84.0 tPM2.5/y, and a simple payback of 0.68 years. Finally, the proposed methodology represents a step forward toward the modern early design of onboard ship energy systems useful for ship designers, manufacturers, owners and operators.

Worldwide, the design, renovation, and sustainable management of port buildings play a crucial role for sustainability. In this framework, a computer simulation of a building’s thermal behaviour is an almost mandatory tool for making informed decisions. However, the development of a building energy model is a challenging task that could discourage its adoption. A possible solution would be to exploit an existing Building Information Modeling (BIM) model to automatically generate an accurate and flexible Building Energy Modeling (BEM) one. Such a method, which can substantially improve decision-making processes, still presents some issues and needs to be further investigated, as also detectable from the literature on the topic. In this framework, a novel workflow to extrapolate BIM data for energy simulation is proposed and analysed in this paper. Here, the BIM to BEM approach was tested as a useful tool for the maritime industry to improve the implementation of effective energy-saving measures. Specifically, in order to prove the capabilities of the proposed method, a maritime passenger station in Naples was chosen as case study and investigated by comparing different strategies to reduce the annual primary energy consumption. The optimal level of modelling detail required by a trustable building energy assessment was also investigated. By the proposed method, interesting primary energy savings (ranging from 24 to 41%) are achieved and CO2 emissions avoided (ranging from 16 to 34 tons CO2/year) for the investigated building, proving the potential of this approach. Definitely, this paper proves the validity of the proposed methodology and emphasizes its numerous benefits towards the achievements of the most modern sustainability standards.

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.

This paper focuses on the experimental validation of a building energy performance simulation tool by means of a comparative analysis between numerical results and measurements obtained on a real test room. The empirical tests were carried out for several months under variable weather conditions and in free-floating indoor temperature regime (switched off HVAC system). Measurements were exploited for validating an in-house simulation tool, implemented in MatLab and called DETECt, developed for dynamically assessing the energy performance of buildings. Results show that simulated indoor air and surface room temperatures resulted in very good agreement with the corresponding experimental data; the detected differences were often lower than 0.5 °C and almost always lower than 1 °C. Very low mean absolute and percentage errors were always achieved. In order to show the capabilities of the developed simulation tool, a suitable case study focused on innovative solar radiation high-reflective coatings, and infrared low-emissivity materials is also presented. The performance of these coatings and materials was investigated through a comparative analysis conducted to evaluate their heating and cooling energy saving potentials. Simulation results, obtained for the real test cell considered as equipped with such innovative coatings and material, show that for the weather zone of Naples a 5% saving is obtained both in summer and in winter by simultaneously adopting a high-reflectance coating and a low- emissivity plaster for roof/external walls and interior walls, respectively.

This paper focuses on the design of an innovative low-cost air-based photovoltaic/thermal collector prototype, for which a novel dynamic simulation model is suitably developed in order to investigate its energy performance and economic feasibility under different operating conditions. The main novelty of this photovoltaic/thermal collector is the low-cost heat extraction system, implemented to reduce the photovoltaic cells temperature and to recover thermal energy. The prototype is tested under different operating conditions and the experimental data are used to validate the presented simulation model. The developed tool, implemented in a MatLab code, is used for analysing a suitable case study. The photovoltaic/thermal collectors are coupled to an air-to-air heat pump for space heating of a sample building. A novel performance map of such a coupled system is built with the aim of linking the heat pump coefficient of performance to both the outdoor air temperature and incident solar radiation. In addition, the system energy effectiveness and economic feasibility, compared to those of a traditional system, are assessed for the climate of 8 different European weather zones. Simulation results highlight the effectiveness of the proposed system, estimating primary energy savings (11.0–19.7 MWh/year corresponding to 52–80%), avoided carbon dioxide emissions (4.64–10.4 tCO2/year), and simple pay-back periods (3.2–4.8 years).

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 facade 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.

This paper presents a new TRNSYS Type (called Type 99) which can be used for the energy assessment of thermosiphon Flat-Plate solar thermal Collectors (FPCs) for water heating. The accuracy of this new type is higher than the standard type (Type 45a) available in TRNSYS library, since the density and specific heat of water are estimated according to the operating fluid temperature. The results of a suitable experimental campaign are also presented for different commercial FPCs system layouts. The developed Type 99 is successfully validated, proven by the very good agreement achieved between the simulation and experimental results. By the new Type 99 a suitable Design of Experiment (DoE) analysis is carried out with the aim to assess the design and operating parameters mostly affecting the energy and economic performance of two types of FPCs. Specifically, collector pipe diameters, slope, storage tank volume, and thermal insulation thickness are investigated. The analysis is carried out for three case studies which refer to residential Domestic Hot Water (DHW) production applications and to three different European weather zones (Freiburg, Naples and Larnaca). For these case studies an optimization procedure is also carried out by varying the same design and operating parameters for two different objective functions: best energy behaviour [maximum Primary Energy Saving (PES)] and best economic performance [minimum Simple Pay Back (SPB)]. Interesting novel design criteria and encouraging economic results are obtained.

Phase change materials are considered a very promising technology to reduce energy consumption for space heating and cooling purposes in buildings. In this framework, this paper presents a comprehensive energy performance analysis of building envelopes integrating phase change materials to provide suitable selection and design criteria of such technology. To this aim, an in-house dynamic simulation model implemented in a computer code, and validated by means of experimental data, has been used. The performance of phase change materials embedded in building enclosures and their optimal configuration (i.e., positions with respect to the construction layers) are evaluated. The results obtained by applying the code to suitable case studies (several climate zones and buildings are investigated) return that the energy saving percentage potentials per cubic meter of phase change materials range from 1.9%/m3 to 18.8%/m3. Finally, interesting design criteria for their adoption in buildings are provided.

Modern cruise ships are energivorous systems and their design is challenging due to stringent restrictions on the environmental impact recently imposed by the International Maritime Organization. Nowadays, energy saving technologies and strategies for ships can be selected and analysed by means of system dynamic simulations. In this paper this innovative goal is obtained through TRNSYS where the ship-envelope and the related energy system are modelled and simulated by means of new customized weather data with the aim to optimize the system energy performance by considering different objective function (maximum energy saving, minimum payback, etc.). To show the effectiveness of the proposed approach, a novel case study is presented. It refers to a modern cruise ship fuelled by liquefied natural gas cruising in Mediterranean and Caribbean seas. Novel hourly weather files are developed for accounting actual locations and orientations of the moving ship. Low-, medium- and high-temperature engines waste heat recoveries are exploited for supplying different thermally activated energy saving devices. Results of the conducted optimization procedure show significant reductions of fuel consumption (between 0.1 and 1.9 kt/y), operating costs (up to 615 k€/y), and pollutant emissions with respect to traditional systems. Short paybacks are obtained (lower than 5 years), depending on the considered innovative system layouts. Finally, useful design and operating criteria for ship manufacturers and users are provided.

This paper presents the design and the thermodynamic analysis of a new prototype of flat-plate solar thermal collector, suitable for building integration, using water as working fluid. The main novelty of the proposed solar thermal collector is the use of cheap materials and simple design solutions, taken into account with the aim to reduce the manufacturing and installation costs towards the improvement of the market penetration of this technology in the near-term future. The collector is suitable for domestic hot water production and for space heating and cooling, achieved through the use of adsorption chillers. A suitable dynamic simulation model for the system energy, comfort, economic, and environmental performance assessment is developed by taking into account both active and passive effects related to the building integration of the solar collector. The developed simulation model, implemented in a suitable MatLab computer tool, is experimentally validated; the main results of the validation process are discussed in this paper. Moreover, in order to show the potential of the presented building integrated collector prototype and of the related simulation tool, a suitable case study is developed. It refers to a residential unit of a multi-floor building where the prototype collectors are integrated on the South facade. Simulations are carried out for 2 building envelope weights and 9 different weather zones. Interesting outcomes from the energy, economic, environmental, and comfort point of views are obtained.

Natural gas is typically transported for long distances through high pressure pipelines. Such pressure must be reduced before the gas distribution to users. The natural gas lamination process, traditionally adopted for this scope, may determine hydrate formation which may damagingly affect the system operation. Therefore, in order to avoid such circumstance, a suitable gas preheating is required. On the other hand, the available pressure drop can be recovered through a turbo-expansion system in order to provide mechanical energy to drive electricity generators. In this case a higher gas preheating is necessary. This paper presents a detailed simulation model capable to accurately analyse this process as well as the traditional decompression one. Such new model, implemented in a computer tool written in MATLAB, allows one to dynamically assess the energy, economic and environmental performance of these systems, by also taking into account hourly energy prices and weather conditions. Two turbo-expansion system layouts are modelled and simulated. In particular, the gas preheating is obtained by considering two different scenarios: gas-fired heater or solar thermal collectors. Another novelty of the presented dynamic simulation tool is the capability to take into account the time fluctuations of electricity feed-in and purchase tariffs. Finally, a suitable case study relative to a gas decompression station located in South Italy is also presented. Here, a remarkable primary energy savings and avoided CO2 emissions can be obtained through the examined turbo-expansion systems vs. traditional decompression ones. Results show that the economic profitability of the investigated novel technology depends on the available gas pressure drops and flow rates and on the produced electricity use.

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. (C) 2015 Elsevier Ltd. All rights reserved.

In this paper the integration of vegetable oil-fed reciprocating engines with solar thermal collector is investigated, seeking to design a novel polygeneration system producing: electricity, space heating and cooling and domestic hot water, for a university building located in Naples (Italy), assumed as case study. The polygeneration system is based on the following main components: concentrating parabolic trough solar collector, double-stage LiBr–H2O absorption chiller and a reciprocating engine fed by vegetable oil. The engine operates at full load producing electrical energy which is in part consumed by the building lights and equipments, in part used by the system passive loads and the rest is eventually sold to the grid. In fact, the engine is grid connected in order to perform a convenient net metering. The system was designed and then simulated by means of a zero-dimensional transient simulation model, developed using the TRNSYS software. The simulation tool developed by the authors allows one to analyze the results for different time basis (minutes, days, weeks, months and years), from both energetic and economic points of view. The economic results show that the system under investigation is profitable, especially if properly funded.

In this paper, a transient simulation model of solar-assisted heating and cooling systems (SHC) is presented. A detailed case study is also discussed, in which three different configurations are considered. In all cases, the SHC system is based on the coupling of evacuated solar collectors with a single-stage LiBr–H2O absorption chiller, and a gas-fired boiler is also included for auxiliary heating, only during the winter season. In the first configuration, the cooling capacity of the absorption chiller and the solar collector area are designed on the basis of the maximum cooling load, and an electric chiller is used as the auxiliary cooling system. The second layout is similar to the first one, but, in this case, the absorption chiller and the solar collector area are sized in order to balance only a fraction of the maximum cooling load. Finally, in the third configuration, there is no electric chiller, and the auxiliary gas-fired boiler is also used in summer to feed the absorption chiller, in case of scarce solar irradiation. The simulation model was developed using the TRNSYS software, and included the analysis of the dynamic behaviour of the building in which the SHC systems were supposed to be installed. The building was simulated using a single-lumped capacitance model. An economic model was also developed, in order to assess the operating and capital costs of the systems under analysis. Furthermore, a mixed heuristic-deterministic optimization algorithm was implemented, in order to determine the set of the synthesis/design variables that maximize the energy efficiency of each configuration under analysis. The results of the case study were analyzed on monthly and weekly basis, paying special attention to the energy and monetary flows of the standard and optimized configurations. The results are encouraging as for the potential of energy saving. On the contrary, the SHC systems appear still far from the economic profitability: however, this is notoriously true for the great majority of renewable energy systems.

SYNOPSIS In this paper the results of a CFD investigation for a push-pull local ventilation system are presented. The velocity field and the capture efficiency prediction are investigated for different system arrangements. The analysis is carried out for systems respectively with and without fluid-dynamic obstacle in the working plane and for dust pollutants with particle diameters ranging from 1.0 to 100 μm and emission velocities between 1.0 and 7.0 m/s. The analysis, carried out using the commercial code FLUENT, shows that the system performances are dependent on operating conditions and are influenced by the presence of the above-mentioned obstacle on the working plane. In the case of working plane emission without obstacle the system capture efficiency is in general very low never exceeding 25%. Higher efficiencies are instead achieved for particle emission from a vessel placed in the system's working plane centre. In this case even unitary peak efficiencies are reached for particular operating condi...

This paper presents a full and partial load exergy analysis of a hybrid SOFC–GT power plant. The plant basically consists of: an air compressor, a fuel compressor, several heat exchangers, a radial gas turbine, mixers, a catalytic burner, an internal reforming tubular solid oxide fuel cell stack, bypass valves, an electrical generator and an inverter. The model is accurately described. Special attention is paid at the calculation of SOFC overpotentials. Maps are introduced, and properly scaled, in order to evaluate the partial load performance of turbomachineries. The plant is simulated at full-load and part-load operation, showing energy and exergy flows trough all its components and thermodynamic properties at each key-point. At full-load operation a maximum value of 65.4% of electrical efficiency is achieved. Three different part-load strategies are introduced. The off-design operation is achieved handling the following parameters: air mass flow rate, fuel mass flow rate, combustor bypass, gas turbine bypass, avoiding the use of a variable speed control system. Results showed that the most efficient part-load strategy corresponded to a constant value of the fuel to air ratio. On the other hand, a lower value of net electrical power (34% of nominal load) could be achieved reducing fuel flow rate, at constant air flow rate. This strategy produces an electrical efficiency drop that becomes 45%. © 2005 Elsevier B.V. All rights reserved.

The economic analysis for running two kinds of hybrid air conditioning systems: all-air and air-and-water, both with add-on evaporative cooling stages, is studied in this paper. Single-duct, single-zone, constant volume systems are dealt with. Processing the climatic data of the European 'test reference year-TRY' for Italy, a comparison of such systems' performance versus the relative traditional one is performed. Energy consumption and operating costs are evaluated by an appropriate computer code written with the aim of: (i) making plain the input/output of data; and (ii) displaying very friendly software masks as well as useful graphical elaboration. On the basis of outdoor air state, calculations are performed according to two different procedures: (a) hourly, following the TRY profile; and (b) for each bin, 1 °C wide, in which the simultaneous dry- and wet-bulb temperatures fall.

In this paper we present work involving the processing of climatic data relating to some Italian cities, taken from a set of data known as European ‘test reference year’ (TRY). We aim to make a critical comparison of the thermohygrometric conditions of outdoor air in the summer season thus obtained with those design conditions as laid down by Italian regulations (UNI 10339) and with those recently suggested by ASHRAE. Subsequently, and with reference to some traditional and recent applications in the field of air-conditioning, we report on how performance differs according to outdoor summer thermohygrometric design conditions, such as those indicated by UNI 10339, by ASHRAE and by the processing of TRY data. Finally, we discuss the optimal choice of design conditions according to the type of application. Copyright © 2000 John Wiley & Sons, Ltd.

This paper deals with European TRY weather data processing for climatic indexes generation, useful for HVAC energy and cost simplified evaluation. For nine Italian locations are presented: 99 and 2.5% dry bulb temperatures, 2.5% wet bulb temperatures, heating and cooling degree days, latent enthalpy days, unitary sensible and latent loads. TRY psychrometric data were processed according to a bin method that preserves the correlation between dry bulb temperature and moisture content, and then reduced by an averaging technique. An example is worked out in order to present an engineering shorthand for energy and cost evaluation of HVAC system.

In this paper, a detailed model of a solid oxide fuel cell (SOFC) tube is presented. The SOFC tube is discretized along its longitudinal axis. Detailed models of the kinetics of the shift and reforming reactions are introduced in order to evaluate their rates along the SOFC axis. Energy, moles, and mass balances are performed for each slice of the components under investigation, allowing the calculation of temperature profiles. Friction factors and heat-exchange coefficients are calculated by means of experimental correlations. As for the SOFC overvoltages, the activation overvoltage is calculated using the Butler‐Volmer equation and semiempirical correlations for the exchange current density, Ohmic losses are evaluated introducing an appropriate electrical scheme and material resistivities, and concentration overvoltage is calculated by means of both binary and Knudsen diffusion coefficients. On the basis of this model, a case study is presented and discussed, in which temperatures, pressures, chemical compositions, and electrical parameters are evaluated for each slice of the SOFC tube under investigation. Finally, a sensitivity analysis is performed, in order to investigate the influence of the design parameters on the performance of the system. DOI: 10.1115/1.2784296

SYNOPSIS In this paper an economic comparison between the sensible and the total energy recovery for HVAC systems in the Italian climate is dealt with. Both all-outdoor-air and mixed-air systems are considered. During the summer period, the energy saving by the sensible device is achieved by evaporative cooling. The performance of the hybrid innovative HVAC system and the traditional one, for both the heating and cooling season, are calculated hour by hour following the Test Reference Year (TRY) profile.

The problem of HCFC22 phase-out in refrigeration plants is analysed. A comparison is performed between R22 and R407C. The latter seems a promising drop-in substitute. Indeed, its use in existing plants would only require discharge of mineral oil and refilling with a compatible polyolester oil. The experimental tests are performed in a plant consisting in a water-cooled vapor-compression circuit employed for cooling a water–glycol mixture in a closed-loop system. Both the thermodynamic properties and general performance of R407C are comparable with those of R22. The COP, however, is 5–17% lower. As a consequence, in order to provide the same refrigerating load, a plant working with R407C requires higher electric-power consumption. The operational behaviour of R407C is increasingly better with increasing condensation and evaporation temperature. Therefore, R407C is a good R22 substitute in all applications requiring high evaporation temperatures, such as air-conditioning plants. © 1997 John Wiley & Sons, Ltd.