Absorber and self-cleaning surfaces on modified polymer plates for solar harvesting in the humid (sub)tropics

• For mild winter climates, a polymeric thermo-solar collector concept is proposed.
• A polymeric absorber plate is used with an absorber/heat exchanger carbon coating.
• Self-cleaning of IR reflective cover is reached by superhydrophobic functionalization.
• Simultaneous cover self-cleaning and high visible/near IR transmittance is shown.
• Results are promising for large-scale, cost-effective solar collector production.

Mild winters in (sub)tropical climates generally do not require water heating to temperatures above 100 °C for residential consumption. This allowed development of a cost-effective polymeric thermo-solar collector concept for all-year and low temperature operation. High absorptance in the solar spectrum (90%) was achieved with a carbon black coating on a transparent PMMA (polymethyl methacrylate) plate, and low emissivity in the black body radiation range at 50 °C (6–14 μm) was provided by a polyester cover. Using the highest average absorber roughness attained (0.369 μm) and a UV-filtered 300 W Xe/Hg lamp, a 30 °C water temperature increase in 80 min was produced. In addition, superhydrophobicity was attained (contact angle of 158±1°158±1° and hysteresis of 2±1°2±1°) by deposition of SiO2SiO2 nanoparticles on the polymeric surface to allow self-cleaning in rainy conditions without significant transmittance loss in the solar spectrum.