Development of a Janus radiative cooler using a versatile fabrication process

Radiative cooling is a passive heat dissipation technique that emits thermal radiation to outer space through the atmosphere window. A radiative cooler has one side facing the sky, and the other side extracts heat from hot targets. Excellent cooling performance of a cooler can be archived via broadband absorption on one side and wavelength-selective emission on the other side like a Janus structure. However, Janus radiative coolers are usually constructed with complicated structures that take tremendous effort and costly facility. This work thus proposes an alternative Janus radiative cooler, which can be fabricated using a versatile and cost-effective fabrication technique, the electrophoretic deposition. The same setup and procedure can deposit chitosan and carbon black thin films on each side of a metallic substrate to achieve dual functionality. Five measurement units were constructed, and fabricated samples were placed on the top surface of each. The cooler successfully lowered the heater temperature inside the unit. Temperature reduction of 5.6 °C and 0.2 °C can be achieved respectively during daytime and nighttime with the proposed cooler compared to the case without thin film depositions. The repeatability of results was validated, and numerical modeling was conducted to exhibit thermal fields. The proposed cooler is promising in diminishing energy demand as well as carbon emissions while taking cost-effectiveness, feasibility, and simplicity into consideration.