Analysis of the heat budget of standard, cool and watered pavements under lab heat-wave conditions

Abstract

The thermal behavior of 12 standard and cool pavement structures (asphalt, granite, stabilized sand, cobblestones, reflective paints, pervious concretes, dry grass, etc.) coupled with pavement-watering is studied in the lab under heatwave like conditions. Watering is fine-tuned for each structure to maximize cooling and minimize water consumption using two linear cooling regimes, before deployment in the field. The surface heat budget is closely studied and the partitioning of irradiance and net radiation into conductive, convective, radiative and cooling flux at surface is analyzed for each structure. Energy partitioning, surface temperature increase and optimal watering rates all exhibit good correlation with overall surface absorptivity. The transmitted flux at varying depths is also characterized using a transmission index that includes surface absorptivity and apparent conductivity of the traversed layers. Results of this study intend to improve our understanding of the energy balance of cool pavements compared to traditional ones under given weather conditions, as well as that of processes involved in the optimization of their evaporative cooling versus watering rate. Benefits of each pavement, efficiency of the method, limitations of the protocol and its potential transposition to the field are all discussed in this contribution.

Capacity of Urban Green Infrastructure Spaces to Ameliorate Heat Wave Impacts in Mediterranean Compact Cities: Case Study of Granada (South-Eastern Spain)

“…Whilst the stronger relationship between NDVI and LST is expected for those greener spaces, such as Node areas (based on their definition), the resulting correlation is negative for the Other areas type. These results point to this type of UGI area, which combines vegetated with non-vegetated permeable surfaces, as being capable of strengthening the city's cooling capacity during heatwave episodes [83][84][85][86]. These areas correspond to small public green spaces distributed heterogeneously throughout the urban matrix and mainly comprise scattered shrubs, grasslands, a mix of medium-and low-height vegetation with scattered or isolated trees, and small parks with irrigation and diverse surface composition.…”

Assessing the Relationship between Land Surface Temperature and Composition Elements of Urban Green Spaces during Heat Waves Episodes in Mediterranean Cities

“…According to the official regional environmental information network for the study area (Environmental Information Net-work of Andalusia-REDIAM), within the years under consideration in the study, 2022 in Granada exhibited, on the on hand, the highest vegetation water stress index (ratio between stressed and non-stressed vegetation) and, on the other hand, one of the lowest monthly average precipitations for the month of June (1.3 L/m 2 ) [99]. Herbaceous vegetation and grass can reach very high temperatures in the absence of evapotranspiration, and their positive impact on air temperature and, consequently, pedestrian heat stress, strongly rely on irrigation, so when this type of land cover becomes dry, the surface temperature can increase, negating its positive impact [100,101].…”

Direct evaporative cooling from wetted surfaces: Challenges for a clean air conditioning solution

“…Mist spray systems for outdoor cooling are the subject of published review work (Ulpiani, 2019) and lie outside the scope of this review. One alternative to spraying water is to wet large porous surfaces such as pavements (Kubilay et al, 2021; Parison et al, 2020). Some authors examine the effect generated by wetted porous elements behaving as passive evaporative cooling walls, such as the pipe ceramics humidified through capillary action developed by J.…”