Water nebulization to counteract urban overheating: Development and experimental test of a smart logic to maximize energy efficiency and outdoor environmental quality
Abstract 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 degC and 6.14 degC 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 degC, whereas with the on off, this threshold was surpassed between the 14% and the 20% of the time by even more than 5 degC. 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.
Applied Energy