Thermal comfort and energy performance of a passive urban climate shelter under extreme heat: Large-scale measurements at Cartuja Qanat Agora

• Full-scale urban climate shelter validated under extreme heat conditions. • Passive cooling reduces outdoor air temperatures by more than 15°C. • Radiant cooling lowers mean radiant temperature by up to 8°C. • Night-time cooling regenerates thermal storage with very high efficiency. • User surveys confirm high outdoor thermal comfort in real urban use. Extreme heat increasingly challenges the sustainability of Mediterranean cities, requiring urban cooling solutions that reduce energy demand without relying on conventional air conditioning. This paper presents a large-scale experimental assessment of the Cartuja Qanat Agora (Seville, Spain), an outdoor climate adaptation prototype that integrates passive cooling, renewable energy generation, and water-based thermal storage within a single operational system. The project rehabilitates the former EXPO’92 Water Avenue as a permanent urban climate refuge through near-total solar blocking, reduction of long-wave radiative loads using a water-fed radiant ceiling, air-temperature reduction via ground- and water-based heat exchange, and nocturnal regeneration of thermal resources through radiative–evaporative cooling powered by on-site photovoltaic energy. System performance is evaluated through an integrated framework combining analysis of outdoor climatic potential, high-resolution microclimatic monitoring, and thermal comfort assessment, complemented by user perception surveys conducted under real-use conditions. During representative extreme-heat events, outdoor temperatures approaching 40°C were mitigated to values around 29°C in the occupied zone, achieving air-temperature reductions exceeding 15°C through passive processes. Thermal comfort remained within the comfort range, and 80% of surveyed users reported a neutral thermal sensation. Night-time regenerative cooling reached a capacity of 152kW with a coefficient of performance of 32.4, confirming the effectiveness of thermal storage regeneration for daytime passive operation. The results demonstrate the potential of integrated energy and water systems to deliver energy-efficient, socially accepted, and replicable urban climate shelters, supporting heat-resilient public spaces in Mediterranean cities.