•Green roofs and green walls have negligible effect on UHI mitigation in winter.•The application scale factor is crucial in mitigating UHI.•BIVT wide application can efficiently mitigate UHI up to ...1 °C.•Green façades on high-rise buildings mitigate UHI more than green roofs.•Wind parallel canyons are preferable to orthogonal ones for green wall installation.
The proposed study investigates the effect of urban heat island mitigation scenarios by applying extensive green roofs, green façades, and living walls to two built areas within Turin and Rome, Italy. Three mitigation scenarios and a baseline one have been developed in ENVI-met software for each built area and run for a typical winter day, summer day, and summer day with a heat wave.
The simulation results show that building integrated vegetation technology-application on a single building has an irrelevant effect on local temperatures; contrariwise, building integrated vegetation technology-wide application can effectively mitigate urban warming. Furthermore, the effect of green roofs and green walls on urban temperature is negligible in winter, likely because of the limited plant activity and the reduced amount of incoming solar radiation. Results also show that green façades are more effective than green roofs in mitigating pedestrian-level air temperature when installed on high-rise buildings, and green walls are more beneficial in mitigating summer urban heat island when installed in canyons parallel to wind direction than in perpendicular ones. Depending on the mitigation scenario, average decreases in urban temperatures up to 1 °C can be reached in the whole selected built area, alleviating urban warming.
Over the last decades, the reduction of the energy use in the building sector has become a topic of major investigation and policy development worldwide. Guidelines have been defined to drive ...governments and building construction stakeholders towards the retrofit of the existing building stock and to the construction of new high-performance buildings. However, availability of operational data is often limited, especially when it comes to high performance buildings in warm climates, although it is essential to define design approaches targeted to energy efficiency, to design smart energy grids and demand-response oriented energy programs. Buildings, such as living laboratories, may offer opportunities to implement and develop energy databases, to provide benchmarks and to study occupant behaviour under different operational conditions.
The paper investigates the energy and thermal comfort performance of a residential building in the Mediterranean climate. The building, certified as Passivhaus and equipped with an advanced monitoring system, allows to test different control strategies, to study occupant behaviour and to provide real time operational data. In particular, the data analysis showed a positive energy balance on yearly basis, i.e. an energy use of 59.7 kWh/m2net/year vs. an on-site energy generation of 76.0 kWh/m2net/year. The energy breakdown highlighted, that energy uses related to user behaviour and comfort requests account for about 72% of the total energy use, confirming that occupant behaviour is one of the major drivers of the operational energy use (and the related services) in high performance buildings.
Energy Performance Certificates (EPCs) and EPC digital registers are key tools to evaluate different aspects of the building stock and its energy consumption. This paper presents several detailed ...energy performance evaluations on the Italian buildings based on a sample of over 2,000,000 EPCs extracted from the national EPC register (SIAPE), contributing to the definition of an updated energy performance baseline of the Italian building stock. This is the first work using the Italian EPC register to define such a baseline to the extent of the authors’ knowledge. Furthermore, combined analyses of EPC data were carried out to obtain information on the influence of the Italian energy regulations on building characteristics and on the effectiveness of energy strategy application for building renovation.
This study underlines the relevance of EPC registers and how the combined analysis of EPC parameters can provide a large amount of useful information on several aspects of the building stock, allowing the monitoring of the impact of the Italian energy policy framework on buildings energy performance. Finally, based on these results, the paper supports public authorities and decision-makers in planning and developing future energy programs and identifying the best practices on the Italian territory.
•Italian building energy performance assessment using the national EPC DBMS, SIAPE.•Evaluation of energy policy impact over time through EPC data combined analysis.•Relevance of the purpose for EPC issuing to monitor energy measure effectiveness.•The results are a support for decision makers to develop energy and sustainable plans.•This kind of analysis can harmonize the energy evaluations on EU buildings.
The results of an extensive experimental campaign on a climate façade with a mechanically ventilated air gap, carried out at the Department of Energetics at the Politecnico di Torino, are presented. ...Measurements were performed utilizing the TWINS (Testing Window Innovative Systems) test facility, which consists of two outdoor cells, one used for reference purposes, and the other which adopts different active façade configurations. The energy efficiency of the façade and the thermal comfort implications have been evaluated considering the ability to pre-heat the ventilation air in the winter season, and the ability to remove part of the solar load during the summer season; the normalized daily energy passing through the façade and the normalized surface temperature of the inner glass were analysed. The improvement in performance obtained by varying the configuration and operative conditions (changing the air flow rate, the shading device and the internal glazing) has been investigated.
Active transparent façades constitute a building envelope component that is becoming more and more common in high-rise office buildings. Many designers have opted for a ventilated façade, claiming ...that this technology is sustainable, reduces energy consumption and enhances indoor comfort conditions, but these claims have often proved to be wrong. From the thermofluid-dynamic analysis point of view, few design procedures or sufficiently detailed, reliable and easy to use simulation software are available for ventilated façades. A numerical model that has been developed to simulate the thermal behaviour of mechanically ventilated active transparent façades is presented in this paper. The model, developed in the Simulink/Matlab
® environment, simulates the façade in both steady-state and transient conditions and provides the temperature of the different layers of the façade structure and the corresponding heat fluxes as output data. The model has been validated by comparing the simulation results with experimental data obtained in the laboratory. A test has also been performed on a real façade under actual operating conditions. The model performance has resulted to be quite promising. The accuracy of the prediction of the temperature is good, while the simulations of the heat fluxes are slightly less reliable for some operative conditions.
Different variables concur to the outdoor comfort assessment and, among them, the Mean Radiant Temperature (Tmr) represents the most challenging one to experimentally evaluate. According to the ...scientific literature, the most accurate method for in-field Tmr calculation is integral radiation measurements with three net radiometers. Nevertheless, net radiometers are expensive sensors and their implementation on large scale may be hindered by their price. To provide a cost-effective alternative some researchers proposed the use of globe thermometers. Globe thermometers are affordable sensors but typically exploited indoors, and their accuracy in urban settings is still under investigation.
The scope of this work is to provide information regarding the extent to which globe thermometers can substitute net radiometers in the evaluation of the Tmr in outdoor urban settings. To this purpose, an experimental comparison has been performed between the Tmr calculated using net radiometers, assumed as a reference, and using two different globe thermometers: a standard 150 mm black globe and a grey 50 mm globe.
The results revealed that the black globe tends to overestimate the Tmr while the grey globe mainly underestimates it. Moreover, the analyses evidenced a wide fluctuation in the profile of the Tmr calculated using globe thermometers, due to the rapid variation of meteorological parameters and the globes' long response time. To improve the fit between globe thermometers and net radiometers' response, regressive functions have been proposed, resulting in a significant enhancement of the adherence between Tmr calculated using the standard black globe's measurements and the reference Tmr.
•Tmr is key parameter for outdoor thermal comfort assessment in urban settings.•Globe thermometers cannot directly substitute net radiometers to assess the Tmr.•A regression equation is used to assess the Tmr from the standard globe thermometer.•In 90.4% of cases, the equation results in a negligible error for Tmr.•This result decreases greatly the cost and number of required sensors.
•Reduced model based on the logistic CDF for the thermocline of hot water TES.•Correlation between the thermocline thickness and Reynolds and Fourier numbers.•Comparison three different numerical ...models: 1D, 2D and reduced model.•Validation on test data of two TES at different temperatures in a mCHP+HP system.
Thermal Energy Storages (TES) are widely used in many energy systems and improving their performance has become increasingly important. Various CFD models are currently available, both one-dimensional and multi-dimensional, with different level of accuracy, computational cost and capability to be generalised. This work is aimed at analising the relevant phases, i.e. charge, discharge and low inertial discharge, of a couple of hot water TES characterized by different inlet temperatures and flow rates, with three numerical approaches: 1D, 2D, and a reduced model. In particular, the latter approach provides a simple analytical function for the evaluation of the temperature profile inside the tanks. The numerical models are validated on experimental data obtained from a test bench with two hot water tanks, in which one tank is connected to a micro-CHP while the other is connected to a heat pump, and operated at different temperature levels.
The results of the 2D and the reduced models are in good agreement with experiments showing a maximum error lower than 1.2 K during the discharge cycles; nevertheless, the reduced model has a much lower computational cost and the dimensionless nature of the implemented function allows generalising the validity of the results to storage tanks operating at different conditions.
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