Transparent conductive far-infrared radiative film based on polyvinyl alcohol with carbon fiber apply in agriculture greenhouse

Abstract In this study, a transparent conductive film is developed using polyvinyl alcohol as the substrate material and carbon fiber is deposited for electrical conductivity. The two materials are mixed into a solution and then cast to form a transparent conductive film suitable for usage in agricultural greenhouses. The designed film with a dimension of 200 mm × 200 mm has an average edge-to-edge resistance of 560.87 + 118.17 Ω, block resistance (BR) of 1.4 + 0.29 Ω/cm2, light transmittance of 70.07% over a wavelength of 400 to 780 nm, and a heating capability of 72 W/m2 via far-infrared light over a wavelength of 25–1,000 µm. Being highly transparent, the film can be integrated into the structure of agricultural greenhouses as it allows adequate sunlight penetration for the necessary photosynthesis of crops while providing heating capability during cold climates in seasonal regions such as northern China, thus replacing the need for conventional electrical heaters. A proof-of-concept is conducted at an agricultural greenhouse in Shandong, China, in rural settings where electricity may not be available. The films were powered with 200 custom-made aluminum-air (Al-air) batteries rated for 12 V, 20 mA. The electrolyte used for the batteries is potassium sulfate (K2SO4), which is a kind of agricultural chemical fertilizer that is easily available in agricultural greenhouse settings. For 7 weeks, the films were successfully powered by the batteries and operated to provide constant heating to maintain the nighttime temperature inside the greenhouse at above 10.06°C with outside temperatures dropping as low as 3.8°C.