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Abstract After shortly highlighting the main features of the classical hydrodynamic theory of pool boiling critical heat flux (CHF), the present paper describes a new approach to predict CHF in the presence of a submerged liquid jet impinging onto the heating surface in saturated conditions at both atmospheric and sub-atmospheric pressure. This approach, based on the instability of liquid-vapor interfaces, has proved to be able of fitting CHF data for submerged jets as well as for electrohydrodynamic (ionic) jets. The main dimensionless parameters governing the phenomenon have been disclosed, namely the Bond number and an equivalent Froude number. Two distinct fluid-dynamic regimes have been identified, herein named velocity-prevailing and gravity-prevailing , depending on the equivalent Froude number values and the subsequent effect of vapor buoyancy on liquid-solid contacts. The developed correlations providing CHF for both regimes have coefficients of determination higher than 0.9 with respect to the available experimental data. Further development may involve the identification of dimensionless parameters and specific correlations for CHF under free-surface jets. [ABSTRACT FROM AUTHOR]

In this study a probabilistic approach for optimal sizing of cogeneration systems under long-term uncertainty in energy demand is proposed. A dynamic simulation framework for detailed modeling of the energy system is defined, consisting in both traditional and optimal operational strategies evaluation. A two-stage stochastic optimization algorithm is developed, adopting Monte Carlo method for the definition of a multi-objective optimization problem. An Italian hospital facility has been used as a case study and a gas internal combustion engine is considered for the cogeneration unit. The results reveal that the influence of uncertainties on both optimal size and annual total cost is significant. Optimal size obtained with the traditional deterministic approach are found to be sub-optimal (up to 30% larger) and the predicted annual cost saving is always lower when accounting for uncertainties. Pareto frontiers of different CHP configurations are presented and show the effectiveness of the proposed method as a useful tool for risk management and focused decision-making, as tradeoffs between system efficiency and system robustness. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of an infinite cylindrical heat source embedded into a saturated porous medium and subject to a cross-axial Darcian flow. Only forced convection is considered. We derived the transient dimensionless solution through a combined analytical – numerical method consisting of four steps: (a) a preliminary dimensional analysis of the constitutive equations of the problem in order to find the dimensionless groups governing the solution; (b) the identification of the validity range of the model as a function of the just-mentioned dimensionless groups; (c) the numerical resolution of the problem; (d) the synthesis of the numerical results in a general dimensionless form. Specifically, we provide several dimensionless maps of the 2D thermal field evolution for six different orders of magnitude of the Péclet number ( 10 - 3 – 10 2 ) . The evolution of the temperature of the heat source is fully illustrated and discussed through plain dimensionless criteria. Then, we discuss the time, space and fluid velocity scales in which the solution is practically equivalent to the ones given by a linear heat source and a purely conductive model. We conclude that the present model has to be employed to evaluate the temperature in proximity of the heat source when the reference Péclet number is greater than 0.5. On the contrary, the linear model can be successfully used for radial distances 5–10 times greater that the heat source radius, depending on the reference Péclet number. [ABSTRACT FROM AUTHOR]

The heat transfer performance of an ionic jet impinging on the upper surface of a heated plate is investigated. Ions are injected by a point, set at high voltage. The working fluid is the viscous dielectric ester MIDEL 7131, a refrigerant for power transformers. Different tests are performed on the working fluid, varying the composition, the shape and the polarity of the point, the applied voltage, the point-to-plane distance, and the imposed heat flux. Heat transfer coefficients are augmented up to 310% with respect to natural convection, a higher enhancement than the one obtained with traditional transformer oil. The electrohydrodynamic flow can be generated without significant power input (<0.01 W in these experiments). Cooling of power transformers can be greatly enhanced by this technique. [ABSTRACT FROM AUTHOR]

In Italy, the recast of the European Directive on Energy Performance of Buildings (2010/31/EU) is implemented with specific definitions and deadlines for Nearly Zero Energy Buildings. We focus our attention on schools, not only for their social importance and high visibility, but also because in the next future a significant share of these buildings is likely to undergo refurbishment for different purposes than the energetic one. We start to analyze the criticalities associated with the current Italian legislation on NZEBs by means of a bottom-up approach: we choose a benchmark secondary school (located in Pisa, hosting about 750 students) and perform an accurate energy audit of the building system, together with an energy and economic simulation of an NZEB retrofit. More in detail, we present the case study and explain its choice as an appropriate representative of the existing scholastic buildings in Centre Italy; besides, we build two concurrent energy models, based on tailored and asset rating methods, we propose technically-feasible actions for deep renovation, and simulate, for both models, the associated energy and economic savings after 20 years of use. We observe long payback periods of the retrofit measures, due to low yearly energy uses in the existing configuration. Based on these results, we attempt to extend to a more general level the considerations on strengths and weaknesses encountered in the present application of the Italian regulation on NZEBs. [ABSTRACT FROM AUTHOR]

The design of HVAC systems for museum exhibition rooms is a challenging issue, as artworks require specific hygrothermal conditions to prevent deterioration: on one hand, technical equipment should be able to maintain optimal microclimate, even in critical conditions (e.g., high visitors' presence); on the other hand, energy inefficiency due to oversized system should be avoided. Specifications and guidelines provide hygrothermal values for several typologies of artworks, but the suitability of these values has not been checked through risk assessment methods. In this work, risk assessment models are used to verify the suitability of hygrothermal values suggested by in-force specifications for three artifacts typologies, i.e. paper, panel paintings and wooden sculptures. Results show that current values are suboptimal for two artwork types. Consequently, a procedure for the artwork risk minimization is applied to identify new suitable hygrothermal values for panel paintings and wooden sculptures. The application of these risk assessment methods is also useful in the characterization of actual microclimate in museum exhibition rooms, through the analysis of monitored data. Moreover, risk assessment methods can be used together with suitability indexes of microclimate performance to assess actual microclimate suitability or evaluate risks in indoor environment dynamic simulations. This procedure can be useful for the decision-making community to provide artwork-depending optimal hygrothermal values for museum environments to professionals. Furthermore, it can also be applied by technicians to obtain reference values to minimize risks and, if possible, achieve additional objectives (e.g., energy savings, human thermal comfort). [ABSTRACT FROM AUTHOR]

In the present work, we investigate the effect of the electrical and gravitational force fields on weakly forced convection (Reynolds numbers range from 500 to 5600) in a square duct heated from the bottom side. On the top side, we placed an array of sharp point electrodes. Microgravity conditions were obtained during a parabolic flight campaign. At the application of a sufficiently-high DC electric field, a plume-like motion is induced in the fluid by the mechanism of ion injection and heat transfer is dramatically augmented. The working fluid is the dielectric liquid HFE-7100. Local temperatures on the heated wall were measured by liquid crystal thermography and by electrical resistance thermometers. By means of the temperature field, we were able to characterize the behaviour of the ionic jets and their interaction with the crossflow. We also investigated the effects of the Reynolds number, the gravity level, and the major electrical parameters on the average heat transfer coefficients. When no electric field is applied, heat transfer coefficients are influenced by the gravity level, particularly at the low flow rates. On the other hand, in the electrohydrodynamic regimes, heat transfer rates are not only enhanced, but also no longer gravity-dependent, showing that the resulting convection is dominated by the electric field intensity, conveniently controllable by the applied high voltage. Relatively small pressure drop increases caused by the induced flow were also measured. Profitable implementation of electrohydrodynamics in the design of compact heat exchangers and heat sinks such as cold plates is foreseen; possible benefits are pumping power reduction, size and weight reduction, and heat exchange capability augmentation. [ABSTRACT FROM AUTHOR]

The application of a strong electric field within a dielectric medium can produce a jet-like motion of ionized liquid from a high-voltage electrode to a grounded heated plate. Ionic jet impingement on the upper surface of a horizontal plate where boiling is occurring significantly modifies the boiling curve. The effect of ion injection on saturated boiling heat transfer, specifically on boiling inception, nucleate boiling, and CHF, in a small-size sample with a single point-electrode configuration, has been experimentally investigated; the working fluid is FC-72. Significant heat transfer enhancement has been observed for the entire nucleate boiling curve. Besides, CHF has been delayed to higher heat fluxes (up to a 40% increase) by means of the impinging ionic jet. This active technique requires a negligible power input (in the order of a few milliwatts) for the ionic current. A focus on the influence of the electrical parameters on the phenomenon has been performed and preliminary results are presented. Further tests and modeling effort are needed to optimize this very promising technique. [ABSTRACT FROM AUTHOR]

This paper deals with the cost-optimal sizing of solar technologies for thermal and electrical needs of residential or tertiary nearly Zero-Energy buildings. The proposed design procedure is based on lifetime simulation of building loads and energy systems; therefore, according to proper cost-optimality considerations, it is possible to find the best sizing of both heat and electricity generators in the context of high-efficiency buildings (e.g. number of solar thermal and PV modules). The paper is divided in two parts. In this first part, we describe general features and principles of the methodology, together with the physical models of building-plant system. Building requirements of thermal and electrical energy are evaluated according to internal loads and external climate, while energy system operation is simulated by a full set of equations reproducing the coupled behavior of each piece of equipment. A preliminary application example referring to a nearly Zero-Energy Building is also illustrated: In the second part of the work, we will apply and discuss the overall simulation-based optimization procedure. Results show the notable benefits of the proposed design approach with respect to traditional ones, in terms of both energy and economic savings. Besides, the proposed methodology can be successfully applied in the more general framework of Net Zero Energy Buildings (NZEBs) in order to fulfill recent regulatory restrictions and objectives in building energy performances. [ABSTRACT FROM AUTHOR]

In this paper, the second of two parts, we apply the cost-optimal design method illustrated in Part 1 [1] to a case study. We select a farm hostel located in Enna, Italy, as the local climate and the required energy services are suitable for the development of a solar-assisted nearly zero-energy building. The system is connected to the electric grid and does not use any other thermal energy vector. Energy demand includes heating, cooling, domestic hot water production, lighting and other electric uses, viz. inductance cooking, food refrigeration, local dehumidification, household appliances, and office devices. The building-plant system is described in terms of both technical characteristics of each component and internal loads. According to the proposed simulation-based methodology, we investigate the best design configuration by minimizing the lifecycle cost after 20 years of operation. The results of the procedure identify the optimal solution, in terms of number of solar thermal and photovoltaic panels, volume and control strategy of the thermal storage. Other outputs are the dynamic and seasonal energy balance of each system component and of the whole system, and additional economic parameters. The results show that the proposed method leads to a very favorable design with relevant notable economic and energy benefits with respect to a no-solar design solution ( ΔC TOT =11%, ΔE IN TOT =67%). However, several nearly optimal configurations provide very similar outcomes in terms of lifecycle costs, with different initial investment and energy performances. Consequentially, we introduce a multi-objective optimization approach aimed at identifying the best solution in terms of investment availability and energy objectives. [ABSTRACT FROM AUTHOR]

SEAS is an energy auditing software that can simulate residential, office, school, and hospital buildings, providing energy requirements for heating, domestic hot water production, ventilation, lighting, and other electrical uses. In order to validate this quasi-steady-state tool, we simulated in SEAS several reference cases (based on EN 15265 benchmark room) and a residential dwelling. We also used the dynamic simulation software TRNSYS and compared the results of the two software in terms of seasonal energy requirements for space heating and energy fluxes through the elements of the building envelope. Most of SEAS results are in good agreement with EN 15265 and with TRNSYS. Nonetheless, we pointed out that SEAS lacks in accuracy when it simulates high thermal inertia buildings with intermittent heating: for these particular cases, new correlations for dynamic parameters and reduction factors should be developed. [ABSTRACT FROM AUTHOR]

Radiant heating coupled to a heat pump is a particularly energy-efficient system, recommended in new constructions. However, the potential energy savings associated with this high thermal inertia system can only be achieved with appropriate control laws, to be tested in a full building–plant simulation environment. The developed transient code concurrently solves three tailored dynamic models of each involved sub-system, namely: building envelope (a benchmark room defined by ISO 13791), radiant floor (designed in accordance with EN 1264-2), and heat pump (an air-to-water electrically-driven modulating unit). Different control strategies were implemented, such as variation of internal temperature set-point dead band, supply temperature to radiant panels, and heating modes. Among the examined variables, we found that the higher energy savings (up to 15%) can be obtained by a proper choice of the supply temperature: in particular, fixed supply temperature should be preferred to climate-based control for this case study. The developed model can be used for optimal design of new systems and associated controls and for accurate energy audits of existing buildings employing these technological solutions. [ABSTRACT FROM AUTHOR]

Abstract: Colour can be expressed as a weighted combination of three attributes: hue, intensity, and saturation. Non-coherent light reflected by thermo-sensitive liquid crystals holds a variable hue, moving in a generally narrow temperature interval and also depending on its inclination with respect to the plane of the crystals and on the characteristics of the impinging light. In experimental practice it is not feasible to ensure uniform lighting over an extensive area and its entire view under the same angle. Thus, the acquired hue field is non-uniform even if the liquid crystal sheet is isothermal. However, by means of proper filtering and calibration of the colour attribute, this optical technique, besides being non-intrusive and inexpensive, is capable of mapping the temperature with an accuracy better than 5% of its measuring-range amplitude. A similar method can be applied for measuring the thickness of a thin liquid film. In this case, the colour attribute to be processed is its intensity. In fact, the light transmitted through a dyed liquid decreases with an increasing thickness of the layer. Again, a perfectly uniform light source is unattainable and the recorded intensity field is non-homogeneous even if the liquid free surface is flat. Nevertheless, the film thickness can be determined by this colour-processing procedure with an accuracy better than 8% of the measuring-range amplitude, which is dictated by the utilised dyestuff concentration. Further thermo-fluid dynamic measurements performed over extensive areas could be handled with analogous methodologies. Surface temperature by emitted infrared waves and void fraction in ducts by light absorption are particular examples. [ABSTRACT FROM AUTHOR]

Abstract: Upward flow of perfluorohexane (FC-72) in the entry zone of a uniformly heated circular duct was studied in a regime of transitional combined forced and free convection. Heat transfer coefficients were measured along the heated length at different values of flow rate and heat flux. Heat transfer impairment in the developing region due to laminarisation of the turbulent flow was observed and characterised by means of two well-known dimensionless groups: the Grätz number and the Grashof number based on the wall heat flux. [Copyright &y& Elsevier]

Abstract: In the presence of a sharp HV electrode, free charge can build up in a single-phase liquid by ion injection at the metal/liquid interface. Electrophoretic forces acting on ions can generate strong convective motion, thus augmenting the heat transfer rate. In a vertical annular duct, uniformly heated on the outer wall, a dielectric liquid is weakly forced to flow upward. Sharp points are added perpendicularly to the inner cylinder and d.c. voltages as high as 22 kV are applied to it, while the outer wall is grounded. Prior to the application of the electric field, a regime of turbulent aided mixed convection is obtained. Being in a region of thermally developing flow, laminarization effects are observed, with local heat transfer coefficients depending non-trivially on longitudinal position, heat flux, and flow rate. With the electric field on, heat transfer turns out to be only weakly influenced by the heat flux and the flow rate. The heat exchange reveals to be highly enhanced by this technique and can be modulated by varying the applied voltage. In all cases, the heat transfer improvement is accompanied by a slight increase in pressure drop through the test section and a negligible Joule heating. [Copyright &y& Elsevier]

Abstract: The preliminary experimental results of the effect of an electrostatic field on turbulent aided mixed convection in a short vertical annulus are reported herein. A dielectric liquid (FC-72 by 3M) is used as working fluid. The local heat transfer improvement is obtained by inserting appropriate points on the inner surface of the annulus, generally acting as the positive electrode, while the surrounding pipe is grounded. A high voltage (up to 22 kV) is established between the two surfaces. The heat exchange revealed to be highly enhanced by this technique, thus providing encouraging indications for practical applications. [Copyright &y& Elsevier]

The paper deals with the multi-objective optimization of the HVAC control in museums. Scientific literature, technical standards and museums stakeholders mainly focus on the single-objective of artefacts conservation. However, a major attention should be paid at visitors' comfort and energy consumption, without compromizing artwork integrity. In this work, we propose and apply a methodology to find the best control of the air-handling unit to concurrently optimize the three objectives. The proposed methodology is based on the achievement function method and finds the Pareto-optimal value of the HVAC control variables over the operational period. The priority given to each objective can be customized by changing the reference point of the achievement function. The method is applied to a museum in Italy hosting paper artworks during summer. Both exhibition room and HVAC system are simulated through an in-house dynamic model. The results show that all three objectives are improved with respect to typical fixed setpoint values (i.e., T = 23 °C and RH = 50%). Depending on the reference point, different profiles of indoor hygrothermal parameters are found; in any case, improvements of each of the objective functions indexes (equivalent lifetime multiplier for artwork preservation, predicted percentage of dissatisfied, and energy consumption) are obtained with respect to fixed setpoint strategy. The multi-objective optimization of museums with paper artworks in summer periods encourages low indoor temperatures. This would lead to slightly increased energy consumptions, which can be limited, by reducing the ventilation rate to 3–3.5 1/h instead of the typical 4–5 1/h. • The multi-objective methodology optimizes museums HVAC control in each timestep. • Objective functions are artwork preservation, visitors' comfort, and energy saving. • Objectives priority is chosen by changing the optimization reference point. • All objectives are concurrently improved with respect to fixed-setpoint strategies. • A case study compares different control strategies and objectives priorities. [ABSTRACT FROM AUTHOR]

• Robust optimal integration of heat pumps in distributed energy systems is analyzed. • Climate, load and economic uncertainties are included by the Monte Carlo method. • The proposed multi-objective stochastic method optimizes both sizing and operation. • The method maximizes the expected performances, even in worst-case scenarios. • Heat pumps improve the system performances and reduce the effects of uncertainties. Heat pumps represent a link between different energy vectors and their application in thermal and electrical grids can improve the overall operational flexibility of the system. In this work, the optimal integration of electrically driven heat pumps within a hybrid distributed energy system is investigated. A multi-objective stochastic optimization methodology is proposed to evaluate the integrated optimal sizing and operation of the energy systems under uncertainties in climate, space occupancy, energy loads, and fuel costs. A case study is considered, namely a University campus, and two different configurations, with and without heat pumps, are compared. Both configurations include a cogeneration system, photovoltaic and solar thermal panels, and a wind turbine. The results show how the integration of heat pumps can reduce the operational cost of the system, increase the renewables share, provide a more robust design of the system, and moderate the risk of the investment. Indeed, the configuration with heat pumps entails a 50% higher expected value of the energy savings, a 28% increase of the renewable energy production, and higher energy savings in the worst-case scenario (13% vs. 5%). [ABSTRACT FROM AUTHOR]

• An integration of reversible absorption heat pumps in cogeneration systems is proposed. • A levelized cost of electricity method is applied to the proposed system. • An exergy analysis is performed to compare different energy systems. • The system is economically optimized (design and operation) in a case study. • The proposed system shows promising energy and economic performance. Polygeneration energy systems in building applications are widely recognized as an effective way to reduce primary energy consumption and greenhouse gas emissions, thanks to high energy efficiencies and optimal integration of different energy technologies and sources. In the present work, the integration of a reversible absorption heat pump and an internal combustion engine in a novel trigeneration system is proposed. The reversible absorption heat pump, which employs a water-ammonia mixture, is driven by the exhaust gas of the engine, and can produce heating and cooling, alternately. The proposed trigeneration system is presented, and the energy services provided under the heating and cooling operating modes are evaluated. A levelized cost of energy analysis is conducted to evaluate the economic viability of the proposed system. Next, a second-law analysis compares its overall exergy efficiency to those of conventional systems. Finally, the novel trigeneration system is implemented in a case study, namely a large office building located in Pisa, Italy. The integrated optimal sizing and operation are evaluated by using a genetic algorithm-based procedure. The findings show that the system integrating reversible absorption heat pump and cogeneration unit provides valuable economic and energy performance. The exergy efficiency of the system can reach 43%, and cost savings of around 5% and 10% are achieved compared to traditional cogeneration and separate-production system, respectively. [ABSTRACT FROM AUTHOR]

• The TES allows a cost and primary energy consumption up to 8% and 13% respectively. • The energy flexibility depends on the TES capacity and the operation control. • The DR specific cost is reduced between 45% and 75% with TES installed. • Performance maps can be created to characterise building flexibility potential. The present paper assesses the capability of a cost-optimal control strategy to activate demand response actions in a building equipped with an air-source heat pump coupled with a water thermal storage system. Commencing with a reference scenario where no demand response actions are considered, the electricity consumption pattern and the operational cost are evaluated. Several demand response scenarios are next considered by adapting consumption patterns by reduction of baseline heat pump power consumption. The difference between the operational cost evaluated under a specific demand response program and the benchmark cost are used to assess the marginal cost that should be considered to provide incentives to promote user participation in demand response programs. The results illustrate the effectiveness of thermal energy storage for reducing the total system operational cost and its seasonal primary energy consumption, both with and without demand response actions. The application of the proposed methodology over the whole heating season, allows performance maps to be created that can be used either by the grid-operator or end-user to identify the best demand response action to be implemented on any particular day. These maps represent useful decision tools to assess and optimise the flexibility potential while meeting end-user needs. [ABSTRACT FROM AUTHOR]

• The proposed procedure evaluates risks for books in historic libraries. • Monitoring campaigns and handy indices were applied to evaluate risky situations. • Risks are related to hygrothermal values that cause biological and chemical damage. • The procedure is applied on the Baroque Library of the University of Coimbra. • For the case study, solutions are identified to improve book preservation. The study presents a new procedure for identifying possible risks for books kept in historic libraries. It is addressed to all those historic libraries where large collections of old and rare books are stored and preserved. These libraries were rarely used by people, but, nowadays, many of them have become touristic attractions. Consequently, their indoor microclimate may have changed, possibly leading to risks for books conservation. The proposed methodology is based on an intensive monitoring campaign, followed by an in-depth data analysis. Handy indices are also proposed to guide the researchers in the identification of possible risks. Problems related to too-high daily or spatial hygrothermal variations or problems related to specific risks (e.g., biological or chemical risks) can be identified. If a problem is observed, the identification of the most suitable solutions is more straightforward. The application of the proposed procedure to a real case study (the Baroque Library of the University of Coimbra, Portugal) has highlighted its handiness. A 6-month monitoring campaign and its consequent data analysis has pointed out potentially risky situations. Thus, measures should be taken to avoid books damage. Primarily, local actions are suggested. [ABSTRACT FROM AUTHOR]

Energy performance improvement in manufacturing is hindered by the lack of information on energy use in production and by the predominant economic vision in the assessment of energy interventions. This paper proposes a framework that integrates energy performance mapping with energy systems optimization. The framework introduces a new dimension to energy performance mapping by tracing energy use along processing and energy conversion steps and revisits multi-criteria assessments by assigning penalties to the energy performance gap with best practice. The suitability of food manufacturing for the application of the framework is exemplified from both a top-down and bottom-up perspective. More than 80% reductions in purchased energy carriers and non-renewable energy sources are achieved in a representative process through interventions coupling sector-specific manufacturing knowledge and energy expertise. With regard to one of the interventions, the introduction of the penalty is shown to shift the optimal solution, yielding more than 25% reductions in energy consumption compared to a purely economic assessment. The proposed framework can help industrial stakeholders identify improvement opportunities and develop more sustainable energy systems in manufacturing. Its widespread use can encourage poor performing companies to align with best practice and virtuous companies to continuous innovation to maintain their competitive advantage. [Display omitted] • A framework for energy performance improvement in manufacturing is proposed. • The framework introduces a new dimension to energy performance mapping. • The framework revisits multi-criteria assessments with an applicative orientation. • 80% reductions in purchased and non-renewable energy are achieved in a case study. • The introduction of the penalty yields 25% energy reduction in the optimal solution. [ABSTRACT FROM AUTHOR]

In museums, hygrothermal conditions must be carefully controlled by HVAC system to avoid artwork degradation. Higher energy requirements are needed for the maintenance of the suitable thermal environment. Moreover, a comfortable thermal sensation is needed for a positive museum experience. In light of current policies on energy efficiency, we propose an original procedure for the concurrent achievement of three goals: artwork preservation, energy efficiency, and human thermal comfort. This procedure is based on the application of multi-objective optimization and aims at correctly choosing temperature and relative humidity setpoints, through the use of dynamic simulations and evaluation of three indexes as objectives. This strategy can be particularly effective in museums hosted in historic buildings, where envelope and HVAC refurbishment is often forbidden or discouraged due to the architectural constraints. Furthermore, the retrofit action is almost costless. A case study is presented: first, a monitoring campaign in an Italian museum has been used for the validation of dynamic simulation models of the building-HVAC system; then, the validated models have been used to show that improvements of artwork lifetime, human thermal comfort and reduction of energy requirements of the HVAC system are possible, if currently-used hygrothermal setpoints (based on technical standards and guidelines) are replaced with those identified by the optimization problem. [ABSTRACT FROM AUTHOR]

Renewable Energy Communities (RECs) are increasingly recognised as potential tools for promoting the adoption of Renewable Energy Sources (RES). However, their success depends on the energy flexibility of participants – that is, their willingness to adjust habits to better align with energy production and loads. This study aims to provide insights into whether participation in a REC can enhance users' flexibility compared to individual prosumers. Our analysis is grounded in an experiment conducted with 192 young adults, using a web-based serious game developed specifically for this study. The results of a logit regression analysis suggest that the sense of belonging to a REC increases flexibility when combined with peer pressure. Control variables such as environmental or ethical concern are also found to influence energy flexibility. These findings provide useful suggestions for policymakers and energy managers in promoting renewable energy sources and sustainable energy practices. [ABSTRACT FROM AUTHOR]

The scientific literature lacks methodologies for assessing HRES investments because of complex interactions among HRES components, conflicting objectives, and uncertainty in the energy demand. This work fills this gap by presenting a methodology to assess long-term investments in HRES for off-grid buildings. To strengthen the reliability of the assessment, the methodology exploits an HRES optimal synthesis, sizing and operation simulating the system and embodying the interactions among HRES components for both electrical and heat generation, the building loads evaluation, and the verification of the effect of uncertainties in the energy demand. These aspects have already been investigated, but, to our best knowledge, have never been considered in a concurrent and integrated way. The resulting designs are optimised through an NSGA-II algorithm that minimises the system CO 2 emissions and differential cost with respect to a solution that does not use renewable energy sources. The soundness of the solutions is evaluated through a scenario analysis and a sensitivity analysis using the Morris method. The applicability of the proposal was verified through a case study in an off-grid facility, showing possible savings up to 47 k€ and 320 t CO 2. The methodology is thus strongly consistent with the building decarbonisation addresses set by the policymakers. • The methodology optimises HRES synthesis, sizing and control in off-grid building. • The methodology is applied to a case study of a farm hostel in Italy. • The Pareto frontier is created considering environmental and economic aspects. • Five optimal solutions are analysed, distinct for total costs and caused emissions. • Scenario and sensitivity analyses corroborate the robustness of the solutions. [ABSTRACT FROM AUTHOR]