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Thermoelectric cooling suffers from low energy conversion efficiency (i.e., COP) which is a major bottleneck that hurdles its wide application, especially for large-scale systems. The COP of thermoelectric cooling system can be improved by integrating with other technologies. Due to its "free" nature, radiative sky cooling technology can potentially be integrated with thermoelectric cooling to obtain much higher system COP. This study introduces a novel radiative sky cooling-assisted thermoelectric cooling (RSC-TEC) system. The system has four different working modes under different operating conditions. A case study has been conducted for a two-story residential building that has 223 m2 living zone area located in Los Angeles, USA. Sensitivity analysis is first performed to size the system parameters. It is shown that the RSC-TEC system with a 0.83 m3 cold storage tank, 32 m2 radiative cooling surface area, and 101 thermoelectric modules (Laird ZT8-12), could achieve annual cooling COP of 1.87. Further analysis showed that daytime and nighttime cooling of the radiative sky cooling subsystem contribute to 55.0% and 45.0% of annual cold generation (heat dissipation) respectively, which indicates the critical importance of daytime cooling. The RSC-TEC system demonstrates a potential solution for large-scale adoption of the thermoelectric cooling technology. • A radiative sky cooling assisted thermoelectric cooling (RSC-TEC) system is proposed. • Sensitivity analysis is performed to size the system parameters. • Annual building energy simulation is conducted with EnergyPlus and MATLAB. • Annual cooling COP of 1.87 is achieved in a two-story residential building. • The RSC-TEC system demonstrates a potential solution for the wide adoption of thermoelectric cooling technology. [ABSTRACT FROM AUTHOR]

• Improved model developed to evaluate a metamaterial-based new cool roof performance. • The model incorporates the spectrum selective approach for radiative sky cooling. • Experiments of the metamaterial-based cool roof are conducted on reduced-size building. • The metamaterial-based cool roof can significantly reduce roof-induced cooling load. A new cool roof with potential to generate significant energy savings in buildings has been developed from a metamaterial film named as RadiCold. Considering that the RadiCold film has unique optical and thermal characteristics and the current Roof Thermal Transfer Value model neglecting the effect of roof thermal mass that may lead to overestimating the cooling load from roofs, this work developed an improved Roof Thermal Transfer Value model and validated the model for both RadiCold cool roof and traditional roofing structures. Data from the reduced-size model building experiments showed that the improved Roof Thermal Transfer Value model can accurately describe the heat gains or losses via the roofs. Under real-world weather conditions in the United States (Tucson AZ, Los Angeles, CA, and Orlando FL), the improved Roof Thermal Transfer Value model has been applied to three types of roof exterior finishing: shingle, Thermoplastic Polyolefin (a cool roof material) and RadiCold. In a typical meteorology year, the modeling results show that the shingle and Thermoplastic Polyolefin roof transfer 78.9–294.1 kWh/(m2·yr) and 8.5–128.2 kWh/(m2·yr) of heat into the building space, respectively, but the RadiCold cool roof dissipates 137.6–268.7 kWh/(m2·yr) of heat from the building space to outdoor environment (e.g., sky). The cooling load reduction from utilizing RadiCold cool roof results in cooling electricity savings of 113.0–143.9 kWh/(m2·yr) compared to the shingle roof and 88.0–92.4 kWh/(m2·yr) compared to the Thermoplastic Polyolefin roof for the three analyzed locations with an assumed air conditioning system's coefficient of performance of 3.0. [ABSTRACT FROM AUTHOR]