Infrared-transparent convection shields for radiative cooling: Initial results on corrugated polyethylene foils

Radiative cooling to a temperature far below that of the ambience requires a new type of convection shield which combines high transmittance in the 8–13 μm wavelength range with high non-radiative thermal resistance. We investigated a design with crossed layers of vee-corrugated high-density polyethylene foils. Typical results were infrared transmittance up to 73% (measured on an infrared-imaging instrument) together with thermal resistance of 1.1 m2 K W−1 (determined with a modified guarded hot-plate technique).