Coupling spectral-dependent radiative cooling with building energy simulation

As a passive cooling strategy without energy consumption, radiative cooling has attracted considerable attention, especially in the building field. Building energy simulations have been conducted to identify the benefits of this technology in buildings. However, in existing studies, constant emissivity was used for radiative cooling materials in the building energy simulation programs, which can cause certain errors. To tackle this problem, this study developed a method to couple the spectral-dependent radiative cooling with building energy simulations in EnergyPlus. Compared with the existing constant-emissivity model, the proposed coupled model can further consider the influence of spectral-dependent emissivity, material surface temperature, and precipitable water on the radiative cooling power in EnergyPlus. Based on the results in a typical strip mall in New York, the radiative cooling power calculated by the proposed spectral-dependent model can be significantly different from that by the existing constant-emissivity model. However, since the energy saving from radiative cooling was relatively small compared with the total energy consumption, the differences in annual cooling electricity and heating natural gas consumption calculated by both models were not significant. Furthermore, case studies in five cities using the proposed model showed that using a broadband radiative cooling roof on a typical strip mall would reduce the annual electricity consumption for cooling, while increasing the annual natural gas consumption for heating. The coupling of spectral-dependent radiative cooling with building energy simulation would improve the accuracy of energy performance assessment for buildings with radiative cooling technology.