Performance analysis on system-level integration and operation of daytime radiative cooling technology for air-conditioning in buildings

Abstract

Passive daytime radiative cooling has attracted recent interest due to its ability to achieve sub-ambient cooling without energy input. However, the practical utility of radiative cooling for building applications remains under-explored, which requires not only rational design and integration of the system but also optimized control. In this work, we develop a detailed model-based framework for system-level integration of water-based daytime radiative cooling panels with heat exchangers and cold storage to cool indoor air for residential buildings. A numerical model was developed to simulate and analyze the heat transfer processes for the entire system. With this model, the effects of different system design and operation parameters were investigated in detail, including water flow rate, parasitic convective heat transfer coefficients, size of radiative cooling panels, number of heat exchangers, and operational schemes. We show that optimal water flow rates needed to maximize air-cooling are 0.001–0.002 kg/(s⋅m2), with air temperature drops approaching 12.7 °C for typical single-family houses in the U.S. Based on an energy and economic analysis, the feasible capital costs to practically implement integrated radiative cooling systems with payback period were estimated for different U.S. cities. Our work not only identifies key operational constraints and recommendations for building energy management using radiative cooling, but also develops design guidelines for the practical integration of radiative cooling systems.