Research, development, and interest in PDRCs has grown rapidly since the 2010s, attributable to a breakthrough in the use of photonic metamaterials to increase daytime cooling in 2014, along with growing concerns over energy use and global warming. PDRC can be contrasted with traditional compression-based cooling systems (e.g., air conditioners) that consume substantial amounts of energy, have a net heating effect (heating the outdoors more than cooling the indoors), require ready access to electric power and often employ coolants that deplete the ozone or have a strong greenhouse effect,