Abstract
While capabilities in urban climate modeling have substantially increased in recent decades, the interdependency of changes in environmental surface properties and human (dis)comfort have only recently received attention. The open-source solar long-wave environmental irradiance geometry (SOLWEIG) model is one of the state-of-the-art models frequently used for urban (micro-)climatic studies. Here, we present updated calculation schemes for SOLWEIG allowing the improved prediction of surface temperatures (wall and ground). We illustrate that parameterizations based on measurements of global radiation on a south-facing vertical plane obtain better results compared to those based on solar elevation. Due to the limited number of ground surface temperature parameterizations in SOLWEIG, we implement the two-layer force-restore method for calculating ground temperature for various soil conditions. To characterize changes in urban canyon air temperature (Tcan), we couple the calculation method as used in the Town Energy Balance (TEB) model. Comparison of model results and observations (obtained during field campaigns) indicates a good agreement between modeled and measured Tcan, with an explained variance of R2 = 0.99. Finally, we implement an energy balance model for vertically mounted PV modules to contrast different urban surface properties. Specifically, we consider (i) an environment comprising dark asphalt and a glass facade and (ii) an environment comprising bright concrete and a PV facade. The model results show a substantially decreased Tcan (by up to − 1.65°C) for the latter case, indicating the potential of partially reducing/mitigating urban heat island effects.
Highlights
Today about half of the world’s population resides in urban areas
Due to the possible settings in FLIR Tools (FLIR Systems 2016), the position where pictures were taken was 5 m in front looking normal to the wall of the Schwackhofer-Haus and the emissivity was set to εw = 0.95
Following Lindberg et al (2016), we show in Fig. 2a the difference in wall surface temperature Tw and air temperature Tcan, as a function of the maximum solar elevation
Summary
Today about half of the world’s population resides in urban areas. In order to adapt to climate change, some countries aim to reduce solar absorption in urban environments by maximizing the area of highly reflective surfaces through installation of the socalled white roofs. At a time where sustainable energy production becomes more and more important, “solar cities” aim on maximizing “solar harvest”, i.e., the solar yield from photovoltaic (PV) modules, by directing their roofs and. This study has shown that for specific study areas, the non-baseload electricity demand can be satisfied by costeffective PV investments on roofs and facades at today’s market conditions for up to 10 months of the year. Winter mid-day electricity demand can only be achieved if the solar yield of PV facades is taken into account
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