## 2 Research in Sustainable Energy Systems at DTG: Main Results and Discussion
### Urban Heat Island Effect in Padova: Theoretic and Experimental Analysis  
In the period 26 July-9 August 2012 some mobile surveys were conducted by the authors. A vehicle crossing the city of Padova mounted with the measurement instrumentation continuously recorded the data (Figure 20). Data were measured during the late afternoon (day measurements) and 1 to 4 h after sunset (night measurements) to evaluate the different intensity of the UHI phenomenon. The main variables detected were solar global radiation on the horizontal, relative humidity, and dry bulb air temperature. The UHI intensity was calculated by the difference between the air temperature by mobile measurement and the simultaneous data recorded by the reference rural meteorological station (8.5 km from the city centre). Figure 19: (**a**) Schematic of the WLSC supermarket; (**b**) electricity consumption of the WLSC system divided for each element in six experimental tests. Figure 20: (**a**) The path of mobile surveys from north-west (NW) to south-east (SE) of Padova and back (Google Earth); (**b**) the vehicle equipped with a data logger, anemometer, thermo-hygrometer and globothermometer, supplied by a rechargeable battery, transformer and magnetothermic switch. Experimental measurements revealed that the main intensity of the UHI was during the night (3-6 \({}^{\circ}\)C), while a lower value was present during the day (1.2-2 \({}^{\circ}\)C, Figure 21). As a methodology note, the evaluation of the intensity of UHI was considered only during the \"return\" path (SE to NW). In fact, moving from the countryside towards the city centre when the air was cooling allowed to consider this as the most precautionary path. The maximum intensity of UHI was detected when crossing the historic centre with narrow streets (high height-to-width ratio (H/W) of the street). The increase in impervious surfaces and the H/W ratio along via Guizza, a long road that crosses the suburb to inside the city, were the main causes of the UHI intensity increase (Figure 21). The following part of the path was along a canal (via Goito): This was the reason the UHI intensity decreased due to the water evaporative cooling effect. Furthermore, some measurements (wind velocity, air humidity, temperature and mean radiant temperature (MRT)) were realized in some characteristic sites along the path. Here, only the case of Prato della Valle during night measurements is depicted because it is representative of very different situations in the same place (Table 3). This picturesque circle in the centre of the city is the second largest urban square (about 90,000 m\({}^{2}\)) in Europe. A decrease in nightly temperature was expected as green areas and water flows were present; instead, as reported by the red star in Figure 21, a maximum was measured. This revealed the limited spatial influence of the beneficial effect of the green, as the path passed not inside the circle but within the perimeter. Based on data from Table 3, the RayMan model [58; 59] was used to determine the main outdoor thermal comfort indices: The Predicted Mean Vote (PMV), the Physiological Equivalent Temperature (PET) and the new Standard Effective Temperature (SET*). Regarding air temperature, the results indicated a difference of 0.5-1 \({}^{\circ}\)C between external positions 1, 2, 3, 6 (near the streets) and in the green (position 4). Instead, a larger difference in MRT was measured (with a maximum of 7 \({}^{\circ}\)C) due to the different characteristics (water storage capacity, thermal inertia and emissivity) of the surface; moreover, a lower sky view factor (SVF) can be detected in outer positions with respect to the square centre. As a consequence, PMV and PET highlighted a neutral situation in the green and a slightly warm condition in the outer positions. The same air temperature was measured  
Figure 21: UHI intensity during the night-time mobile survey of 30 July 2012. The U-turn point corresponds to the vertical broken line. The Prato della Valle site is represented by the red star. in Pos.