Passive daytime radiative cooling has "the potential to simultaneously alleviate the two major problems of energy crisis and global warming" while being an "environmental protection refrigeration technology." PDRCs thereby have an array of potential applications, but are now most often applied to various aspects of the built environment, such as building envelopes, cool pavements, and other surfaces to decrease energy demand, costs, and CO 2 emissions. PDRC has been tested and applied for indoor space cooling, outdoor urban cooling, solar cell efficiency, power plant condenser cooling, among other applications. For outdoor applications, the lifetime of PDRCs should be adequately estimated, both for high humidity and heat as well as for UV stability.