•A novel prototype of water nebulizers was optimized to mitigate the urban climate.•Climate adaptive features were imparted by implementing a fuzzy controller.•Fuzzy and on-off logics were monitored ...and compared in two different urban settings.•The energy saving touched 70% with ambient conditions very close to neutrality.•The cooling capacity reached −7.5 °C mostly dependent on wind.
Several mature urban climate mitigation technologies have been proposed to date. What mostly hinders their wide implementation is that their efficiency heavily depends on the local microclimatic specificities, since they cannot self-adjust to the environmental changes. This study aims at investigating benefits and impacts of smart logics applied to outdoor cooling, by field testing a web of nebulizers coupled to a bespoke fuzzy controller piloting the pump. The cooling action was tweaked as convenient to maintain comfortable conditions and to avoid energy wastage whenever unneeded. To the best of the authors’ knowledge, this is the first application of fuzzy logic to water spraying systems (or to any other controllable urban climate mitigation technology) targeting comfort and energy optimization. The prototype was field monitored in comparison with the conventional on-off control, in two Italian urban contexts (Cfa and Csa climatic zones) over 15 days in the hottest months of the year. The cooling and humidification action was thoroughly characterized by mapping both the horizontal and vertical profiles and by applying advanced Artificial Intelligence techniques to spot the main environmental drivers. The maximum cooling (measured between the sprayed area and an undisturbed reference) touched 7.5 °C and 6.14 °C in the two locations, respectively. The energy saving achieved under fuzzy control versus the temporized control, was spectacularly high in the wetter and windier location with an average of −51.2% and a maximum of −67.5%. The comfort benefit was also substantial: the temperature never deviated from neutrality by more than ±2 °C, whereas with the on–off, this threshold was surpassed between the 14% and the 20% of the time by even more than 5 °C. The results suggest that smartly controlled nebulization is an energy-efficient and comfort-effective strategy to counteract urban overheating. Furthermore, solar-powered solutions are well suited as proved by the preliminary design estimation we included.
Increase of the ambient air temperature in cities caused by the urban heat island phenomenon has a seri- ous impact on the economic and social system of cities. to counterbalance the consequences of ...the increased urban temperatures important research has been carried out resulting in the development of efficient mitigation technologies. the present paper aims to present the state of the art in terms of local climate change and urban heat island mitigation techniques. In particular, developments in the field on highly reflective materials, cool and green roofs, cool pavements, urban green and of other mitigation technologies are presented in detail, while examples of implemented projects are given.
The building energy performance pattern is predicted to be shifted in the future due to climate change. To analyze this phenomenon, there is an urgent need for reliable and robust future weather ...datasets. Several ways for estimating future climate projection and creating weather files exist. This paper attempts to comparatively analyze three tools for generating future weather datasets based on statistical downscaling (WeatherShift, Meteonorm, and CCWorldWeatherGen) with one based on dynamical downscaling (a future-typical meteorological year, created using a high-quality reginal climate model). Four weather datasets for the city of Rome are generated and applied to the energy simulation of a mono family house and an apartment block as representative building types of Italian residential building stock. The results show that morphed weather files have a relatively similar operation in predicting the future comfort and energy performance of the buildings. In addition, discrepancy between them and the dynamical downscaled weather file is revealed. The analysis shows that this comes not only from using different approaches for creating future weather datasets but also by the building type. Therefore, for finding climate resilient solutions for buildings, care should be taken in using different methods for developing future weather datasets, and regional and localized analysis becomes vital.
•Cooling energy savings up to 2.9kWh/m2 in the reference cooled buildings for 0.1 increase of solar reflectance.•Average operative reduction up to 1.1°C in the reference not cooled buildings during ...summer.•Average external surface temperature reduction up to 7.5°C, with peak reductions up to 25°C.
Cool materials are characterized by high solar reflectance and by high thermal emissivity, the combination of these two radiative properties allows such construction materials to remain cooler than conventional materials of the same colour under the solar radiation. During the past decades there was a growing interest mainly for roofing and pavements applications, aiming at cooling buildings and cities. This study presents the potentiality of the technology for façade applications in residential buildings, focusing on the performance in the Mediterranean region, where cooling energy uses and urban heat islands are critical issues. The study analyses the performance of cooled and non-cooled buildings by means of dynamic simulations, showing the potentiality of the technology in terms of energy performance and impact on indoor thermal comfort. Calculations are carried out for several building configurations and climatic conditions; also the impact of different solar reflectance values of facades, depending on their orientation, was explored. Cooling energy savings up to 2.9kWh/m2 per 0.1 increase of solar reflectance are calculated. The average indoor operative temperature is reduced up to 1.1°C in non-cooled buildings during the summer period. Average exterior surface temperature reductions up to 7.5°C, with peak reductions up to 25°C, are calculated.
Urban greenery is a natural solution to cool cities and provide comfort, clean air and significant social, health and economic benefits. This paper aims to present the latest progress on the field of ...greenery urban mitigation techniques including aspects related to the theoretical and experimental assessment of the greenery cooling potential, the impact on urban vegetation on energy, health and comfort and the acquired knowledge on the best integration of the various types of greenery in the urban frame. Also to present the recent knowledge on the impact of climate change on the cooling performance of urban vegetation and investigate and analyse possible technological solutions to face the impact of high ambient temperatures.
Indoor Environmental Quality (IEQ) is a crucial issue in school buildings, because of the conditions that pupils and students are exposed to. From this assumption, potentialities of retrofit actions ...with Nearly Zero-Energy Building (NZEB) targets were analyzed in existing school buildings, focusing on the impact of such measures of IEQ. Numerical analyses in a transient regime for a typical school building were carried out to assess the impacts on the thermal comfort and Indoor Air Quality (IAQ). The study took into account several building configurations and three reference cities. The results showed severe overheating risks in retrofitted schools: the operative temperature increased by several degrees with respect to the existing configuration, leading to thermal discomfort for a relevant part of the observation period. Passive techniques, namely external solar protection devices and night ventilative cooling, were applied to assess their mitigation potential. Results showed that the combination of the two solutions restored the pre-retrofit performance. CO2 levels were found to be too high for naturally ventilated buildings, regardless of the building configuration; acceptable levels might be reached only with long opening times of windows, which are unrealistic for real building operation.
•Experimental characterisation of cool coloured materials for facade applications.•Impact on the cooling and energy performance of residential buildings.•Thermal response of envelope materials ...exposed to the solar radiation.
Climate changes and urban sprawl dramatically increase the urban temperatures and the thermal quality in the built environment. Among several proposed mitigation techniques, cool roofs have now reached a broad audience, while the cool materials potentialities for façade applications are still little investigated. A novel masonry paint, produced with the inclusion of cool pigments, is investigated in this paper. A palette of colour is developed with the objective of covering a wide range of architectural integration solutions. Reflectance and emissivity are measured and calculated. The results strongly depend on the base colour used to prepare the sample; solar reflectance increase up to 0.16 is achieved for dark colours. A numerical analysis is carried out to evaluate the impact of the cool paint on the thermal response of a typical Italian residential building. Energy uses are calculated for different insulation levels and climatic conditions. Cooling energy uses are reduced in the 10–20% range; total energy uses are affected by several parameters with 5% maximum savings. Peak operative temperature reductions range from 0.5 to 1.6°C for the building in free floating conditions, according to climate and insulation level. External surface temperatures are reduced above 6°C during the peak irradiation hours.
The combination/integration of renewable energy and storage systems appears to have significant potential, achieving high-energy results with lower costs and emissions. One way to cover the thermal ...needs of a building is through solar energy and its seasonal storage in the ground. The SMARTEP project aims to create an experimental area that provides for the construction of a road solar thermal collector directly connected to a seasonal low-temperature geothermal storage with vertical boreholes. The storage can be connected to a ground-to-water heat pump for building acclimatization. This system will meet the requirements of visual impact and reduction of the occupied area. Nevertheless, several constraints related to the radiative properties of the surfaces and the lack of proper thermal insulation have to be addressed. The project includes the study of several configurations and suitable materials, the set-up of a dynamic simulation model and the construction of a small-scale road thermal collector. These phases allowed for an experimental area to be built. Thanks to careful investigation in the field, it will be possible to identify the characteristics and the best operation strategy to maximize the energy management of the whole system in the Mediterranean area.
A radiative cooling device, based on a metamaterial able to mirror solar radiation and emit heat toward the universe by the transparency window of the atmosphere (8–13 µm), reaching and maintaining ...temperatures below ambient air, without any electricity input (passive), could have a significant impact on energy consumption of buildings and positive effects on the global warming prevention. A similar device is expected to properly work if exposed to the nocturnal sky, but during the daytime, its efficacy could be affected by its own heating under direct sunlight. In scientific literature, there are only few evidences of lab scale devices, acting as passive radiative cooling at daytime, and remaining few degrees below ambient air. This work describes the proof of concept of a daytime passive radiative cooler, entirely developed in ENEA labs, capable to reach well 12 °C under ambient temperature. In particular, the prototypal device is an acrylic box case, filled with noble gas, whose top face is a metamaterial deposited on a metal substrate covered with a transparent polymeric film. The metamaterial here tested, obtained by means of a semi-empirical approach, is a spectrally selective coating based on low cost materials, deposited as thin films by sputtering on the metallic substrate, that emits selectively in the 8–13 µm region, reflecting elsewhere UV_VIS_NIR_IR electromagnetic radiation. The prototype during the daytime sky could reach temperatures well beyond ambient temperature. However, the proof of concept experiment performed in a bright clear June day has evidenced some limitations. A critical analysis of the obtained experimental results has done, in order to individuate design revisions for the device and to identify future metamaterial improvements.
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