Challenges resulting from urban density and climate change for the EU energy transition

Dense urban morphologies further amplify extreme climate events due to the urban heat island phe-nomenon, rendering cities more vulnerable to the effects of extreme climate events. We developed a modelling framework using multiscale climate and energy system models to assess the compound im-pact of future climate variations and urban densification on renewable energy integration for 18 Euro-pean cities. We observed a marked change in wind speed and temperature due to the aforementioned compound impact, resulting in a notable increase in both peak and annual energy demand. Therefore, an additional cost of 20%‒60% will be needed during the energy transition (without technology inno-vation in building) to guarantee climate resilience. Failure to consider extreme climate events will low-ers power supply reliability by up to 30%. Energy infrastructure in dense urban areas of southern Eu-rope is more vulnerable to the compound impact, necessitating flexibility improvements at the design phase when improving renewable penetration levels.