Coupled experimental-simulation study of radiative cooling ceramics on bus roofs

Passive daytime radiative cooling technology offers a promising energy-saving solution for reducing air-conditioning loads. However, current research on its applications has been predominantly concentrated on the building sector, while the actual performance of passive daytime radiative cooling in the transportation field, particularly in large public transport vehicles, remains unclear. Here, we employ a combined approach of experimental measurements and numerical simulations to investigate the cooling performance and energy-saving potential of passive daytime radiative cooling ceramics as an integrated component in buses. Outdoor tests revealed that the ceramic bottom surface maintained effective heat dissipation performance below ambient conditions, with a temperature difference exceeding 10 °C for over 60 % during daytime hours. Thermal modeling exhibited that passive daytime radiative cooling application reduced the average in-cabin air temperature by 1.23 °C, with the most substantial cooling effects occurring in the afternoon. Economic assessments further demonstrated that daily electricity savings reached 6.75 kWh per bus, corresponding to approximately 1.52 kg of diesel. Scaling up to regional implementation, the use of passive daytime radiative cooling ceramics across buses in Henan Province could save an estimated 1.42 × 10 7 kWh of electricity, 3.4 × 10 3 tons of diesel, and 1.08 × 10 3 tons of CO 2 emissions during summer, which would translate to economic benefits of United States dollar 3.86 million. These findings not only validate the efficacy of passive daytime radiative cooling ceramics as a scalable passive thermal management strategy in reducing fuel consumption and emissions in buses, but also provide crucial support for their broader adoption within the transportation sector. • Cooling ceramic achieves a 7.6 %(6.75 kWh) reduction in daily energy consumption for a bus. • Analysis of optimal cooling system design of radiative cooling ceramic. • Mid-roof is identified as the optimal application location. • Regional economic assessments of radiative cooling ceramic are quantified.