Radiative cooling for buildings: A review of techno-enviro-economics and life-cycle assessment methods

Radiative cooling (RC) can provide free cooling by emitting radiative heat into outer space. This article presents the effects of solar radiation, non-radiative heat gains, atmospheric conditions, and spectral selectivity on the performance of radiative cooling technologies. Radiative cooling materials, including polymeric structures, pigmented paints, and photonic structures, are also reviewed. The benefits of integrating RC structures into buildings are reviewed, including estimates of energy and cost savings, and payback period. Methods for determining the global warming potential (GWP) when carrying out a life-cycle assessment (LCA) for RC structures are also presented. These LCA methods include two primary mechanisms through which radiative cooling technologies reduce GWP: 1) by directly reducing radiative forcing by radiating energy to outer space, and 2) by indirectly reducing radiative forcing by decreasing cooling loads, which reduces the CO2 emissions associated with providing power for cooling. Estimates for exemplary case studies show that by installing radiative cooling technologies the GWP for cooling houses in Jamaica, Ghana and Brazil over a 20 year period can be reduced by ∼40,000 kg CO2-eq, ∼14,000 kgCO2-eq, and ∼22,000 kgCO2-eq, respectively. In most cases, the dominant reason for the decrease in the GWP is the reduction in CO2 emissions achieved by reducing the building cooling load. However, the emission of long wavelength radiation and the corresponding reduction in radiative forcing is significant and is the dominant factor reducing the GWP for some cases. The limitations and future prospects for RC technologies in building applications are also discussed.