A passive radiative cooling method has a significant influence on thermal management applications because it can cool without any energy input. This work both experimentally and theoretically demonstrates a multilayer thin film structure with high solar reflectance, which can be applied to passive daytime radiative cooling. The combination of physical vapor deposition and spin-coating prepared the samples, which were also characterized experimentally by spectrometers. On-site measured results show that the emitter can effectively achieve daytime radiative cooling, and the cooling performance can be further improved with the increase of the ambient air temperature. When the emitter is exposed to direct solar radiation (AM1.5) of about 880 W/m² on a rooftop under dry air conditions, it can achieve an average temperature reduction of about 12.6 °C from the ambient air temperature with nonradiative heat transfer (11 a.m.–1 p.m.). Theoretical simulations reveal that the emitter can still have a certain cooling performance in the presence of significant nonradiative heat exchange and nonideal atmospheric conditions. The influence of ambient air temperature on the cooling performance of the emitter is also theoretically analyzed.

This work theoretically demonstrates a quasi-periodic selective multilayer emitter for sub-ambient daytime radiative cooling. In the design process, by inserting well-defined materials with different refractive-index profiles in suitable layers, there are absorption bands at different regions and the absorption bands are enhanced and broad in atmospheric transparency windows. Combined with the interference effects of the surface and the high reflectivity of Ag, the solar reflectance of the emitter is maximal in the solar spectrum. The influence of different nonradiative heat exchanges and the ambient air temperatures on the cooling performance of the multilayer emitter are calculated. At the same time, the mechanism of radiative cooling is analyzed. All the results show that the proposed emitter can effectively achieve sub-ambient daytime radiative cooling. Due to the superior durability and mechanical robustness of the multilayer emitter, it may be a key element in the realization of energy-efficient radiative cooling devices.

In the context of China’s dual carbon goals—carbon peaking and carbon neutrality—the im-plementation of high-efficiency carbon reduction and control technologies is of paramount importance. This study evaluates the impact of renewable energy integration and energy management strategies on carbon emissions in a research and office institute park located in Nanjing, China. A 1.162 MW photovoltaic system was deployed to supply on-site electricity demand. The system exhibited substantial performance, achieving electricity self-sufficiency rates exceeding 100% on 50 days and surpassing 50% on 58.8% of the monitored days over the study period. To enhance energy efficiency on the demand side, the air conditioning tempera-ture set point was raised from 25 °C to 27 °C. This adjustment led to a 15.1% reduction in air conditioning energy consumption and increased the average summer photovoltaic self-suffi-ciency rate from 51.27% to 56.85%. In addition, a carbon flux tower was installed to facilitate continuous monitoring of carbon flux and atmospheric CO₂ concentrations. The measured data indicated consistently low carbon dioxide concentrations and negative carbon flux values, with average concentra-tions of 464.87 ppm and mean CO₂ flux of –0.0087 mg/m²·s, respectively. These results un-derscore the effectiveness of integrated renewable energy systems and active demand-side management in reducing operational carbon emissions in urban building clusters.