Preliminary assessment of asphalt solar collectors for heat harvesting from urban roads across European cities

Asphalt solar collectors (ASC) recover low-temperature heat from paved surfaces. This preliminary assessment compares seven European cities under a common thermal configuration using hourly ERA5-Land data for 2015–2024. Mean annual recovery ranges from 43.14 kWh m −2 a −1 in Reykjavik to 458.41 kWh m −2 a −1 in Madrid. Historical minimum–maximum spread is 10.74–15.30 % in Nice, Madrid and Rome, compared with 60.15 % in Oulu and 83.29 % in Reykjavik. Combining productivity with mapped asphalt service-road area, 40 % deployment and 2 % annual degradation gives cumulative heat of 84.74 GWh in Amsterdam to 4.31 TWh in Rome over 2026–2050. Area scaling therefore changes the ordering obtained from unit-area productivity alone. Environmental and economic indicators complement this thermal comparison: Madrid, Rome and Nice have the lowest levelized costs, 0.042–0.069 € kWh −1 , and baseline carbon-recovery times of 10.1, 9.6 and 12.6 years, respectively. Within the tested support ranges, capital subsidies affect financial results more than heat-price premiums. Heating-system and policy context identifies the demand, infrastructure and project conditions needed to interpret these preliminary indicators.