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Integrated collector storage units are typically affected by convective and radiative heat losses which significantly reduce their energy performance. To enhance solar collection and heat retention, innovative techniques and novel design of such units are being more and more developed. In this framework, this paper focuses on the design and optimization of a prototypal high-vacuum integrated collector storage solar water heater. The proposed unit allows for reaching high temperatures of the stored water and for reducing the temperature drop during non-collection periods. This goal is achieved by suppressing the convective heat losses into the system by keeping the pressure into the related enclosure below 0.01 Pa and by applying a special selective coating to the solar absorber surface to drastically reduce radiative losses as well. In this paper, details about the system design and the conducted experimental tests are reported. In addition, a new mathematical model able to assess the energy performance of the innovative prototype is presented. This tool, based on a detailed 3-D transient finite-difference thermal network, was validated against the gathered experimental data. By such a tool the optical properties of the adopted selective coating are optimized for maximizing the system thermal efficiency. Finally, with the twofold aim of showing the potentiality of the developed code, as well as the effectiveness of the presented innovative solar collector prototype, a comprehensive case study referred to three different European weather zone is presented. Promising results in terms of energy savings (0.73 MWh/y) and CO2 emission reduction (149 kgCO2/y) are achieved.

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.

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 tCO2/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.

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 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.

This paper presents an innovative Concentrating Glazing system to be adopted in smart building facades: 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 facade system, interesting energy savings ranging from 30 to 60 % for the investigated weather zones can be obtained.

In this paper a new dynamic simulation model for the building energy performance analysis of multi-enclosed thermal zones, where rigid air temperature and humidity conditions must be kept, is presented. The model was implemented in a suitable computer code (DETECt 2.3.1) developed for research scopes. Such simulation model allows the hygrothermal analysis of buildings with multi-enclosed thermal zones surrounded by larger ones (e.g. display glass cases with valuable artefacts in museum halls, neonatal intensive care units for premature and full-term newborn babies in hospitals wards, etc.). For this purpose, a novel control algorithm, based on a model reference adaptive control scheme, enabling the online adaptation of the control gains, is implemented. Rigid air temperature and humidity conditions can be guaranteed also in case of sudden and rapid variations of hygrothermal loads. Through such new tool innovative techniques and operative strategies for obtaining energy efficiency and indoor comfort of special building spaces can be studied. In order to show the capabilities of the tool and the robustness of the adaptive algorithm, as well as the potentiality of the proposed multidisciplinary approach to the energy-related behaviour in buildings (based on building energy modelling and simulation and control theory), two meaningful case studies have been developed. In particular, they refer to the museums and hospital indoor spaces where enclosed thermal zones have to be kept under stringent hygrothermal conditions.

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 work is to assess the active and passive effects due to the building integration of solar technologies on the building energy consumptions. 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 considering 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 results interesting design and economic feasibility guidelines are obtained. For the investigated case studies, the pay back periods vary from 11 years for South European weather zones to 20 for North European ones.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.

This paper analyses the energy, environmental and economic performance of a future scenario where electric vehicles are connected to efficient buildings powered by building integrated flat-plate photovoltaic/thermal collectors, equipped with electric energy storage. The produced renewable electricity and thermal energy are exploited for building electrical and thermal applications. The surplus of produced electricity is stored into the electrical battery and used to charge the electric vehicle. The proposed system is modelled and dynamically simulated within the TRNSYS environment, where special attention is paid to the design of suitable system control strategies, aiming at optimizing the exploitation of the solar energy for electricity and heating purposes. To this aim, a sensitivity analysis is also carried out to find out the optimal system configuration. A case study analysis, relative to the weather zone of Naples (South Italy), is conducted to evaluate the energy, economic and environmental feasibility of the investigated scenario. Simulation results show that, with respect to a reference system, a remarkable reduction of electricity from the grid is achieved, corresponding to a primary energy saving equal to 57.66%. A reduction of 51.63% of CO2 emissions and a simple pay payback period equal to 11.64 years are achieved.

In this paper the design and the energy performance investigation of a new flat-plate solar thermal air collector prototype is presented. The adoption of cost-effective materials and simple design solutions represent the main novelties of the proposed device when compared to existing commercial collectors. In addition, the prototype is suitably designed to be integrated into the building envelope (facade), which is a key feature for the market uptake of building integrated solar thermal systems. The paper includes the description of the dynamic simulation model, developed for the energy and economic performance analyses of the whole building-prototype system. The simulation model, implemented with a computer code written in MatLab, is able to predict both active (hot air production for building space heating) and passive (winter free heating and summer overheating) effects due to the building integration of the proposed solar collector. By such tool, indoor comfort investigations can also be carried out. The dynamic simulation models of both the building and the collector prototype were successfully validated. In order to show the features of the developed simulation code, a suitable case study was carried out. It refers to an office space, part of a high-rise multi-use building, simulated as located in three different weather zones (Freiburg, Naples and Almeria). The examined solar collector is modelled as vertically integrated into the building facade, and three different orientations (East, South-East and South) were taken into account. Interesting results for the energetic, economic and occupants comfort points of view are obtained. By taking into account an initial cost of the system of about 5 k€, the primary energy savings achieved by the proposed system against the traditional buildings range between 1.9 and 8.0 MWh/y (depending on the selected weather zone and backup system). The shortest payback for all the investigated weather zones is obtained for Naples, which is equal to 6.2 years.

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.

In this paper a novel optimal Model Reference Adaptive Control approach, developed to tame the thermohygrometric behaviour of buildings as well as to guarantee the indoor comfort, is presented. The main advantages of the proposed method are: (i) no-need of a priori knowledge of the specific building dynamics due to climate, occupants’ behaviour, building use, envelope features and utility rates; (ii) robustness with respect to a large class of perturbations, external disturbances, nonlinear unmodelled dynamics or parameters uncertainty; (iii) ability to impose desired optimal dynamics; (iv) accurate regulation and fast tracking of indoor air temperature and humidity in the case of stringent requirements in special building spaces (e.g. hospitals, museums, laboratories, etc.). In order to investigate the effectiveness of the proposed method, the developed strategy has been implemented in the new release of a white-modelling building energy performance simulation code, called DETECt 2.3. The tool enables multi-zone building simulation analyses and is capable to dynamically predict: (i) spaces sensible and latent heating and cooling demands and loads; (ii) indoor air temperatures and humidity, as well as building envelope internal and external temperatures; (iii) the performance of phase change materials (PCM) embedded in building enclosures and for any layer configuration; (iv) the thermohygrometric comfort of occupants. In order to analyse the effectiveness and robustness of the proposed control strategy, several case studies have been carried out. They refer to some reference buildings with different geometry, use and construction materials (also including PCM integrated into the building envelope) simulated in different weather conditions. For each case study, both continuous and intermittent control system regimes have been considered. Results confirm the ability of the developed approach to achieve the selected indoor air temperature and humidity conditions in order to guarantee indoor comfort in uncertain conditions. The numerical analysis is complemented with the rigorous analytical proof of asymptotic stability.

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 facade. 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 kWhe/y), comfort outcomes (related hours variation range from −190 to +121), and economic results (paybacks are between 3 and 6 years) are achieved.

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 CO2 emissions and comfort. Paybacks depend on operating conditions. Useful design and operating criteria for trains manufacturers and users are provided.

This paper analyses the integration of air open-loop photovoltaic thermal systems on the facade of high-rise buildings, with a special focus on their active and passive effects. The system energy performance and its impact on the building heating and cooling demands and electrical production are assessed through a new dynamic simulation model. The developed numerical model of the proposed system, based on a detailed transient finite difference thermal network, is verified by comparing its outcomes to experimental results. With the aim to carry out whole building energy performance analyses, the model is implemented in a dynamic simulation tool for the building energy performance assessment, called DETECt 2.3, and suitably modified to analyse the main building integration energy issues. To assess the potentiality of the numerical model and the feasibility of the investigated system, a comprehensive case study relative to a multi-floor high rise office building located in several European climate zones is developed. A comparative and parametric analysis is also carried out with the aim to evaluate the system active and passive effects as a function of the building height. Simulation results show that by using building integrated air open-loop photovoltaic thermal systems, an interesting percentage reduction of the heating demand can be obtained. Both passive and active effects contribute to the variation of the thermal and electrical efficiencies. For the investigated weather zones, the innovative system leads to a reduction of the final energy consumptions ranging from 56.8 to 104.4%, approaching the nearly or net positive zero energy building target in the southern climate. Finally, the proposed analysis also aims to show the main implications linked to the design of the system, to be carefully taken into consideration by designers and stakeholders in case of new buildings or renovations.

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.

This paper presents the design, simulation and optimisation of a small trigeneration plant supplied by geothermal and solar energies. Different technologies are implemented in a dynamic simulation model purposely developed for research scope: a 6 kWe micro Organic Rankine Cycle (ORC); a 30 kWf single stage H2O/LiBr absorption chiller; a geothermal well; a solar field obtained by new prototypal flat-plate evacuated solar collectors. The ORC is supplied by heat obtained by a geothermal well in which geothermal brine is about at 95 °C. In order to improve system performance, additional heat is provided by solar energy obtained through a 25 m2 solar field. Diathermic oil (up to 130 °C) is adopted as working fluid in order to supply heat to the ORC evaporator. A suitable oil storage tank is modelled in order to mitigate the temperature fluctuations due to the variability of solar energy availability. The output power of the ORC depends on the availability of solar energy. The absorption chiller is switched-on in summer time and it is fed by geothermal energy only. This simulation model is implemented in TRNSYS environment. The ORC is modelled by zero-dimensional energy and mass balances implemented in Engineering Equation Solver (EES). A case study is developed in order to test the energy and economic performance of this innovative micro-trigeneration plant. In particular, the above mentioned model is applied to the Regina Isabella hotel in Ischia (Naples, South Italy), famous for its geothermal sources. Currently, such hotel is already equipped by a geothermal system (by several hot water wells) for thermal cares, domestic hot water production and space heating. By TRNSYS the optimisation of the system design parameters and the calculation of the thermo-economic conditions were performed. The system showed excellent energy performance indexes. In fact, the average yearly efficiency of the solar thermal collectors is close to 60%, whereas the average yearly ORC electric efficiency is about 6%, which is a good achievement considering the system driving temperature. Results also show that the system performance is more dependent on the availability of the geothermal energy than the solar one. From the economic point of view, good results are also obtained. In fact, in the worst operating conditions the Simple Pay Back Period is 7.6 years, decreasing to 2.5 years in the most convenient considered scenario (public funding and full utilisation of the produced thermal energy).

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.

A novel dynamic simulation model for the building envelope energy performance analysis is presented in this paper. This tool helps the investigation of many new building technologies to increase the system 36 energy efficiency and it can be carried out for scientific research purposes. In addition to the yearly heat- 37 ing and cooling load and energy demand, the obtained output is the dynamic temperature profile of 38 indoor air and surfaces and the dynamic profile of the thermal fluxes through the building elements. The presented simulation model is also validated through the BESTEST standard procedure. Several new case studies are developed for assessing, through the presented code, the energy performance of three different building envelopes with several different weather conditions. In particular, dwelling and commercial buildings are analysed. Light and heavyweight envelopes as well as different glazed surfaces areas have been used for every case study. With the achieved results interesting design and operating guidelines can be obtained. Such data have been also compared vs. those calculated by TRNSYS and EnergyPlus. The detected deviation of the obtained results vs. those of such standard tools are almost always lower than 10%.

In this paper, a novel purposely designed dynamic simulation model for the performance analysis of solar heating and cooling systems is presented. The investigated system layouts are based on single stage LiBr–H2O absorption chillers and on both evacuated tube and concentrating photovoltaic thermal solar collectors. Furthermore, both electric chiller and gas fired heater backup system are considered. Such model is implemented in a computer code written in MATLAB. Here, the optimisation of several system design and operating parameters in terms of energy saving is also carried out. A code to code analysis is performed comparing the obtained simulation results vs. those achieved by a TRNSYS model available in literature. The simulation code for the concentrating photovoltaic thermal solar collectors is validated by experimental data. A good agreement among results is observed in both the cases. A suitable case study referred to a building including both offices and dwellings located in Northern and Southern Italy is presented. High primary energy savings are obtained for some of the investigated system layouts. By evacuated tube collectors solar field such savings can reach 74%, while shifting to concentrating photovoltaic thermal solar collectors they often surpass 100%. The system economic profitability strongly depends on future scale economies and eventual public funding.

Several new technologies can be today implemented in buildings in order to achieve the NZEB goal. In this paper a novel computer model for predicting the energy demand of buildings integrating phase change materials, photovoltaic-thermal collectors, adjacent sunspaces and innovative daylighting control is presented. Through this tool, DETECt 2.2, written in MatLab and conceived for research purposes, the overall energy and economic performance of multi-zone NZEBs can be assessed. Both the active and passive effects on the energy demands of all the above mentioned technologies, even if simultaneously utilized, are taken into account by means of an integrated building modelling approach. In addition, parametric and sensitivity analyses, with a single simulation run, can be carried out for design purposes. A novel relevant case study referred to the energy design of a non-residential NZEB for Mediterranean climates is developed. For this building a suitable energy optimization analysis was also carried out. For each use of the indoor space, the optimal value of the pivotal design and operating parameters is calculated. Details about the optimal position of building PCMs and thermal insulation layers, also coupled to BIPV and/or BIPV/T systems, are provided. For the obtained best configuration very low heating and cooling demands are achieved (0.9 and 1.5 kWh/m 3 y, respectively). Results about a simplified economic analysis carried out on the investigated energy saving technologies are also reported. At last, new NZEB definition details and criteria are provided for non-residential buildings located in the southern European zones (Mediterranean climates).

In this paper, the simulation of the performance of solar-assisted heating and cooling systems is analyzed. Three different plant layouts are considered: (i) the first one consists of evacuated solar collectors and a single-stage LiBr–H2O absorption chiller; here in order to integrate the system in case of insufficient solar radiation, an electric water-cooled chiller is activated; (ii) configuration of the secondly considered system is similar to the first one, but the absorption chiller and the solar collector area are sized for balancing about 30% of the building cooling load only; (iii) the layout of the thirdly considered system differs from the first one since the auxiliary electric chiller is replaced by a gas-fired heater. Such system configurations also include: circulation pumps, storage tanks, feedback controllers, mixers, diverters and on/off hysteresis controllers. All such devices are modelled for maximizing the system energy efficiency. In order to simulate the systems’ performance for dynamic heating/cooling loads, a single-lumped capacitance building is also modelled and implemented in the computer code. A cost model is also developed in order to calculate the systems’ operating and capital costs. All the models and the relative simulations are carried out by TRNSYS. A design of experiment procedure is also included. By such tool the effects of the system operating parameters’ variation on the relative energy efficiency are analyzed. In addition, the set of synthesis/design variables maximizing the system’s energetic performance can be also identified. The annual primary energy saving is chosen as the optimization objective function, whereas collector slope, pump flows, set-point temperatures and tank volume are selected as optimizing system design variables. A case study was developed for an office building located in South Italy. Here, the energetic and the economic analysis for all the three considered system layouts are carried out. The simulations’ results are referred to both the initial and the optimized systems configurations. The highest primary energy saving vs. the reference traditional HVAC system is reached by the first considered system layout. The economic performance of the investigated solar heating/cooling systems is still unsatisfactory. The economical profitability of the considered solar heating and cooling systems can be improved only by significant public finding. From this point of view, the best results were achieved by the second above mentioned system configuration.

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...

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.

The simulation and exergy analysis of a hybrid Solid Oxide Fuel Cell–Gas Turbine (SOFC–GT) power system are discussed in this paper. In the SOFC reactor model, it is assumed that only hydrogen participates in the electrochemical reaction and that the high temperature of the stack pushes the internal steam reforming reaction to completion; the unreacted gases are assumed to be fully oxidized in the combustor downstream of the SOFC stack. Compressors and GTs are modeled on the basis of their isentropic efficiency. As regards the heat exchangers and the heat recovery steam generator, all characterized by a tube-in-tube counterflow arrangement, the simulation is carried out using the thermal efficiency-NTU approach. Energy and exergy balances are performed not only for the whole plant but also for each component in order to evaluate the distribution of irreversibility and thermodynamic inefficiencies. Simulations are performed for different values of operating pressure, fuel utilization factor, fuel-to-air and steam-to-fuel ratios and current density. Results showed that, for a 1.5 MW system, an electrical efficiency close to 60% can be achieved using appropriate values of the most important design variables; in particular, the operating pressure and cell current density. When heat loss recovery is also taken into account, a global efficiency of about 70% is achieved.

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.

In this paper, a purposely designed code for the performance analysis of the Water Loop Heat Pump (WLHP) systems is presented. Hourly, daily and seasonal energy system consumptions, operating economic costs and environmental impact assessments are dealt with. For the scope of comparison, the performances of two reference HVAC system are investigated too. For the computation of the building heating and cooling requirements, a suitable dynamic performance simulation model is being developed. All the relevant algorithms are implemented in MATLAB®. A case study of an office building undergoing simulation in different European climatic areas is being presented. Here, different building thermal features are considered. In order to maximize the system performance an additional optimization procedure to the operating devices temperatures is carried out. Results show that primary energy savings and avoided CO2 emissions of the WLHP system vary in relation to the compared reference systems and can be obtained only in several European weather zones. The feasibility of the WLHP system strongly depends on electricity and natural gas national costs.

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.

Nowadays the computational fluid dynamics (CFD) simulation represents an important tool for the performance analysis of the local exhaust ventilation (LEV) systems. In this paper air velocity field in the proximity of a free-standing flanged slot having a 6:1 aspect ratio is investigated by such an approach. Numerically calculated velocities both in centreline and off the hood axis are compared with the velocities obtained by the most popular experimental and theoretical formulas available in literature. Simple equations are with a common mathematical structure, which are provided for all the numerically simulated velocity trends.

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.

Evaporative cooling can be adopted in wet areas by integration into HVAC systems. Processing TRY data for Italy, the economics of three-stage evaporative cooling systems were examined. Summertime conventional system operating costs and hybrid system savings were evaluated. The method was based on a simplified approach that is not intended as a substitute for accurate dynamic modelling, but as a simple analysis tool. The results were found to be strongly dependent on: climatic area, internal set point, initial cost of extra equipment. The highest savings appeared to be achieved in the middle-south of Italy. © 1999 Elsevier Science Ltd. All rights reserved.