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Abstract: This paper presents a detailed finite-volume model of a concentrating photovoltaic/thermal (PVT) solar collector. The PVT solar collector consists in a parabolic trough concentrator and a linear triangular receiver. The bottom surfaces of the triangular receiver are equipped with triple-junction cells whereas the top surface is covered by an absorbing surface. The cooling fluid (water) flows inside a channel along the longitudinal direction of the PVT collector. The system was discretized along its axis and, for each slice of the discretized computational domain, mass and energy balances were considered. The model allows one to evaluate both thermodynamic and electrical parameters along the axis of the PVT collector. Then, for each slice of the computational domain, exergy balances were also considered in order to evaluate the corresponding exergy destruction rate and exergetic efficiency. Therefore, the model also calculates the magnitude of the irreversibilities inside the collector and it allows one to detect where these irreversibilities occur. A sensitivity analysis is also performed with the scope to evaluate the effect of the variation of the main design/environmental parameters on the energetic and exergetic performance of the PVT collector. [Copyright &y& Elsevier]

Abstract: The paper is focused on the dynamic simulation of a Photovoltaic/Thermal collector (PVT) integrated in a high-temperature Solar Heating and Cooling (SHC) system. The system is based on the following main components: concentrating parabolic PVT (photovoltaic thermal) collectors, a double-stage LiBr-H2O absorption chiller, storage tanks, auxiliary heaters, balance of plant devices. The PVT is made-up by a parabolic dish concentrator and a triple-junction receiver. The polygeneration system provides electricity, space heating and cooling and domestic hot water for a given building, whose simulation is also included in the model. In particular, PVT produces electric energy, which is in part consumed by the building loads (lights and equipments), in part by the system parasitic loads, whereas the eventual excess is sold to the public grid. Simultaneously, the PVT provides the heat required to drive the absorption chiller. The system was simulated by means of a zero-dimensional transient model, that allows the evaluation of temperature profiles and also heat/electrical energy flows for whatever period of the year. It is also possible to evaluate the overall energetic and economic performance on whatever time basis (day, week, month, year, etc.). The economic results show that the system under investigation can be profitable, if a proper funding policy is available. The paper also includes an extensive parametric analysis aiming at evaluating the set of design and operating parameters (solar field area, tank volumes, set point temperatures, etc.) that maximize the energetic and/or economic performance of the system. [Copyright &y& Elsevier]

In this paper a novel dynamic simulation model for enhancing the sustainability of transportation systems equipped with diesel co-generators is presented. In each simulation time step of the carried out energy performance analyses, the best operation/combination of generators as well as their optimal part load ratio are determined with the aim to achieve the minimum fuel consumption. Input to the model are: size of each installed diesel generator; number of engines; required power profile; route scheduling and hourly weather data. The developed simulation model is implemented in TRNSYS environment. Here, a new in-house TRNSYS type written in Fortran is also included. With the presented approach - especially helpful for cruise ship designers, manufacturers and owners - new design criteria and useful technical results can be obtained. To show the capability of the tool a novel case study is presented. It concerns on an existing cruise ship to be refurbished from the energy point of view. Here, four diesel generators are installed on-board. The ship energy system includes five electric chillers, two auxiliary boilers, two reverse osmosis and two multi-stage flash desalination devices (driven by the diesel generators waste heat recoveries). Simulation results show remarkable energy savings obtained through the proposed optimization approach. Specifically, a maximum primary energy saving of about 15 GWh/y is obtained compared to the initial reference scenario. It corresponds to a fuel consumption reduction of 2.5 kt/y (-1.6 M$/y) and to an avoided CO 2 emission of 8.0 kt/y. • Proposed model improves sustainability of ships through unit commitment approach. • Optimization of the generators operating sequence increases a ship's energy efficiency. • The model dynamically adapts waste heat recovery to different operating conditions. • A novel algorithm identifies the best running sequence for on-board generators. • Primary energy saving of 1.92% and fuel consumption reduction of 1.73% are obtained. [ABSTRACT FROM AUTHOR]

This paper presents a novel dynamic simulation model for the analysis of a hybrid turboexpander system coupled with innovative high-vacuum solar thermal collectors. The model is developed in MatLab and it is able to dynamically calculate the energy, exergy, environmental, and economic performances of the investigated system, by taking into account the hourly fluctuation of thermodynamic and economic parameters (e.g. electricity cost, natural gas temperature, and flow rates, etc.). In addition, a computer-based Design of Experiment (DoE) approach was implemented for achieving the optimal design of the proposed system. A suitable case study is presented in order to show the capabilities of the developed simulation tool. Conventional and non-conventional decompression systems located in the weather zone of Messina (South-Italy) are investigated with the aim of assessing the optimal system configuration. By means of the computer-based DoE analysis, the optimal values of several design parameters (such as the number of solar thermal collectors, the volume of the hot water storage tank, and the size of the water loop pump) are calculated. Numerical results show significant primary energy savings (1.36 TWh/year) and avoided carbon dioxide emissions (348 t CO2 /year). From the economic point of view, a feasible simple pay-back period of 4.51 years is achieved. The destroyed exergy of the system components are calculated, obtaining the highest value for the turbo-expander, equal to 12.0 TWh/year. • Dynamic modelling and simulation of natural gas turbo-expander system. • Energy, exergy and economic analysis of the turbo-expander system coupled to solar thermal collector field. • DoE analysis for the optimization of the solar field. • Analysis of a case study of pressure reduction station. • Confirmed system feasibility by achieved energy, economic and environmental results. [ABSTRACT FROM AUTHOR]

Optimal design of building envelopes/HVAC systems and free cooling strategies are today necessary to reduce energy, economic and environmental impact of telecommunication, electricity distribution, or electric transportations infrastructures. To this aim, designers and operators require advanced techniques and tools. Target of this paper is to present the development of a simulation model for assessing and optimizing cooling performance of new/existing infrastructures to be designed/refurbished from the energy point of view. The model is implemented in a computer tool to assess the related potential benefits of different energy saving technologies/strategies and optimize different objective functions. By the presented approach new design and operating criteria are developed by varying all the occurring boundary conditions (weather, temperature limitations, electricity tariffs, etc.). To show the capability and suitability of the proposed approach, a case study concerning the equipment cooling of a railway substation is developed. The analysis is conducted for different Italian climates, obtaining remarkable energy savings. Specifically, by optimizing free cooling operation and thermal insulation the cooling energy consumption can be decreased up to 80% and 10%, respectively. By an energy refurbishment of all the Italian railway substations an annual electricity cost reduction due to equipment conditioning of about 0.5 M€ can be achieved, 47% lower. • Distributed building infrastructures have great potential of reducing cooling energy consumption. • Dynamic simulation is a paramount tool to design enhanced energy management strategies. • Free cooling contributes to 50% reduction of energy demand for equipment cooling. • Operational energy and use of material can be reduced with optimal envelope design. • The study proposes design criteria aimed at increasing energy efficiency at the infrastructure level. [ABSTRACT FROM AUTHOR]

This paper presents an innovative water photovoltaic thermal collector prototype. One of the main novelties of such system is its economic affordability, obtained through low-cost materials. The collector, constructed and experimentally tested at the University of Patras (Greece), is composed of a polycrystalline photovoltaic module coupled to eleven plastic pipes for water heating, located under the PV panel in an aluminium box. The prototype, suitable for building architectonical integration, can provide domestic hot water and electricity to the building. In order to assess the energy, economic and environmental performance of the system under different weather conditions and for diverse building uses, a suitable dynamic simulation model was developed and validated vs. experimental data. To investigate the convenience of the presented prototype and the potentiality of the developed software, a suitable case study is presented. In particular, the photovoltaic thermal collector is coupled to a stratified hot water storage tank for supplying domestic hot water to a single-family house located in three different European weather zones: Freiburg, Naples and Almeria. The system layout optimization was also performed through an energy and economic sensitivity analysis to some design and operating parameters. Useful design criteria and interesting energy and economic results were obtained. • Development of a novel low-cost photovoltaic/thermal collector prototype. • Development of a dynamic model for thermal and electrical performance assessment. • Experimental validation of the developed simulation model. • Comparative analysis between prototype and commercial collector performance. • Case study analysis for evaluating the prototype energy and economic feasibility. [ABSTRACT FROM AUTHOR]

In the last years, the Covid-19 outbreak raised great awareness about ventilation system performance in confined spaces. Specifically, the heating, ventilation, and air conditioning system design and operating parameters, such as air change per hour, air recirculation ratio, filtration device performance, and vents location, play a crucial role in reducing the spread of viruses, moulds, bacteria, and general pollutants. Concerning the transport sector, due to the impracticability of social distancing, and the relatively loose requirements of ventilation standards, the SARS-COV-19 outbreak brought a reduction of payload (up to 50%) for different carriers. Specifically, this has been particularly severe for the railway sector, where train coaches are typically characterized by relatively elevated occupancy and high recirculation ratios. In this framework, to improve the Indoor Air Quality and reduce the Covid-19 contagion risk in railway carriages, the present paper investigates the energy, economic and environmental feasibility of diverse ventilation strategies. To do so, a novel dynamic simulation tool for the complete dynamic performance investigation of trains was developed in an OpenStudio environment. To assess the Covid-19 contagion risk connected to the investigated scenarios, the Wells-Riley model has been adopted. To prove the proposed approach's capabilities and show the Covid-19 infection risk reduction potentially achievable by varying the adopted ventilation strategies, a suitable case study related to an existing medium-distance train operating in South/Central Italy is presented. The conducted numerical simulations return interesting results providing also useful design criteria. [ABSTRACT FROM AUTHOR]

This paper investigates several actions for the energy refurbishment of some buildings of the University Hospital Federico II of Naples. The analysis focuses on a specific lot of 4 buildings, representative of the whole district hospital. For those structures, sustainable energy savings actions are investigated. They regard the installation of: i) roofs thermal insulation; ii) a substation climatic 3-way valve; iii) radiators thermostatic valves; iv) AHU (air handling unit) time-programmable regulation. This paper aims at presenting an investigation methodology, useful for designers and other stakeholders involved in hospital energy refurbishments, based on an integrated approach which combines dynamic energy performance simulations and experimental campaigns. In order to measure all the simulations' missing input parameters, a suitable experimental analysis, including measurements of temperature, humidity, flow rate and density of construction materials, is performed. A thermographic investigation is also performed for investigating the building envelope performance. This analysis showed that significant savings can be achieved especially by adopting radiators thermostatic valves and AHU regulations. Coherently, the installation of a 3-way valve in the substation does not determine significant additional savings when radiators thermostatic valves are already installed. For high-rise buildings, roofs insulation returns only marginal reductions of space heating and cooling demands. [ABSTRACT FROM AUTHOR]

This paper explores the implementation of the Building To Vehicle To Building (V2B2) scheme in European Countries, by evaluating the influence of weather conditions and local energy market prices on its energy and economic performance. The use of electric vehicles as energy vectors among buildings belonging to a virtual cluster is the key aspect of the V2B2 scheme: by exploiting mobile electric storage devices, renewable electricity produced by building integrated PV panels is shared among diverse users and consumed off-site. This novel energy management scheme has a twofold aim: i) promoting energy flexibility and efficiency in multiple buildings by improving the share of self-consumed renewable electricity at a cluster level and ii) reducing the interaction with the power grid. The proposed cluster includes two buildings, a house and an office space, and an electric vehicle, and it can be considered as the basic nucleus of human linked energy users. The energy and economic performance of the proposed V2B2 scheme highly depends on weather conditions and purchasing/selling electricity price. Therefore, to assess the impact of weather and energy prices on the system energy and economic performance, a comprehensive parametric analysis is conducted by varying the main design and operating parameters of the capacity of the key components of the investigated energy cluster, such as of buildings integrating PV panels and electric storage devices. The modelled and simulated scenarios refer to two different layouts simulated in several European cities, selected to consider different weather conditions and national electricity market prices. To identify the optimal V2B2 configurations, several energy and economic indicators of each simulated scenario are compared to a conventional reference one in which the novel energy management scheme is not implemented. Through the proposed V2B2 scheme, encouraging energy savings, from a minimum of 13.6% to a maximum of 71.2%, and economic outcomes are achieved. • Energy and economic performance of the Building to Vehicle to Building scheme. • The proposed V2B2 layouts are simulated in 22 European cities. • Evaluation of the impact of the weather and of national energy market prices. • Grid interactions drop from a minimum of 13.6% to a maximum of 71.2%. • Net present values reach 18.0 k€, also thanks to favorable energy prices. [ABSTRACT FROM AUTHOR]

This paper presents an innovative Concentrating Glazing system to be adopted in smart building façades: The Concentrating Photovoltaic Glazing system (CoPVG). The device consists of a double-glazing panel integrating a series of concentrating lenses. A thin layer of PV cells is then placed at the lenses' focus. The peculiar lens design can produce, by using the Total Internal Reflection (TIR), a seasonal effect with more light entering the building at low incidence angles (i.e. in the winter months) and higher electricity production at high incidence angles (i.e. in the summer months). To investigate this device's performance, a suitable dynamic simulation tool has been developed in MATLAB environment. Furthermore, to investigate active (electric energy production) and passive (building insulation and solar gains variations) effects related to the building integrated devices, the developed CoPVG simulation tool is implemented in a building energy performance simulation one (DETECt). To show the potential of the innovative device, a case study relative to a multi-floor office building integrating the innovative CoPVG prototype is investigated. Conventional and semi-transparent PV windows are also investigated for comparative purposes. By using the novel façade system, interesting energy savings ranging from 30 to 60 % for the investigated weather zones can be obtained. • Novel building integrated concentrating photovoltaic glazing system. • Modelling and dynamic simulation of smart building facades. • Analysis of photovoltaic yield of concentrating and standard solar windows. • Analysis of passive effects of building integrated glazing systems. [ABSTRACT FROM AUTHOR]

Solar systems represent a viable way to reduce in a sustainable manner building energy consumptions. Nevertheless, two issues can be underlined: insufficient building surface areas for hosting typical stand-alone solar devices and related high initial costs. Consequently, growing research and industrial interest in cost-effective building-integrated solar systems is today observed. In this framework, this paper presents a comprehensive analysis of two low-cost building-integrated hybrid photovoltaic/thermal collector prototypes (water- and air-cooled, respectively). Both active and passive effects are investigated employing a purposely developed dynamic simulation tool, able to carry out complete system performance analyses. The capability of such the proposed innovative devices as well as of the presented in-house code is shown by a novel case study regarding a dwelling unit located into a multi-story residential building for three diverse European weather zones. Here, the investigated prototypes are modelled as integrated into the building South façade. For comparison purposes, a building integrated photovoltaic panel is also modelled as a reference case. Both active and passive effects are assessed. Relevant energy savings (up to 4236 kWh e /y), comfort outcomes (related hours variation range from −190 to +121), and economic results (paybacks are between 3 and 6 years) are achieved. • Novel low-cost building integrated photovoltaic thermal collectors are presented. • A dynamic simulation tool for the prototypes analysis is developed and validated. • Thermal energy and electricity production are estimated by using the developed tool. • Analyses of the prototypes building integration passive effects are performed. • Energy, economic and indoor thermal comfort analyses have been conducted. [ABSTRACT FROM AUTHOR]

Nowadays, due also to high hygrothermal comfort requirements, the energy consumption for heating/cooling of modern trains can reach 30% of the related overall electricity demand. Energy-saving of train Heating, Ventilation and Air Conditioning systems can be suitably assessed through dynamic simulation approaches. Specifically, the weather solicitation has to be dynamically accounted for by considering the actual moving train location and orientation. Through such methodology different innovative actions for energy efficiency, environmental impact reduction and comfort enhancement can be analysed by also assessing their economic feasibility. In this paper, a novel simulation tool for the complete performance analysis of trains was developed in TRNSYS environment. To show the capabilities of the considered approach, a novel case study referred to an existing medium-distance train operating in South Italy is presented. Heating/cooling loads and demands, and the related electricity requirements, are dynamically assessed for the standard and revamped train. Several energy saving actions are considered for the coupling between the envelope and the Heating, Ventilation and Air Conditioning systems enhancement. The obtained results return significant benefits in terms of energy saving, avoided CO 2 emissions and comfort. Paybacks depend on operating conditions. Useful design and operating criteria for trains manufacturers and users are provided. • Dynamic simulation for train HVAC system energy performance analyses using TRNSYS. • Customized weather data files for accounting real train locations and orientations. • Innovative energy efficiency solutions for trains with saving up to 6.0 MWh e /y. • Economic feasibility of energy efficiency solutions for trains. • Reduction up to 50% of the train environmental impact. [ABSTRACT FROM AUTHOR]