Prospects toward UV-blue filtered solar drying of agricultural farm produce using chemically deposited copper chalcogenide thin films on cellular polycarbonate. (June 2020)

• Record Type: Journal Article
• Authors: Nair, P.K.; Espinosa-Santana, Angélica Lizbeth; Guerrero-Martínez, Laura; López-Ortiz, Anabel; Nair, M.T.S.
• Is Part Of: Solar energy. Volume 203(2020)
• Page Start: 123
• Page End: 135
• Publication Date: 2020-06
• Subjects: Solar drying -- Copper chalcogenides -- Copper sulfide -- Copper selenide -- Chemical deposition; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2020.04.012
• Languages: English
• ISSNs: 0038-092X

Abstract

Graphical abstract: Solar drying of produce F on mesh M irradiated through cellular polycarbonate (PC) with a copper chalcogenide UV-Blue optical filter. Highlights: Chemically deposited copper chalcogenide coatings for novel solar drying. They are degenerate semiconductors with zero UV transmittance and high absorption. UV filtered solar drying benefits from nearly 850 W/m 2 of solar energy in the bin. Methodology for large-scale batch production of coatings in cellular polycarbonate. Abstract: We analyze the suitability of copper chalcogenide (sulfide/selenide) thin films applied by chemical deposition on cellular polycarbonate sheet (8 mm cell-size, 0.6 mm wall thickness) 130 cm × 122 cm in area in UV-blue filtered solar dehydration of farm produce. The optical bandgap of 1.5 eV of these semiconductors causes the optical transmittance of the coated sheets to drop toward zero for solar radiation of wavelengths shorter than 500 nm. A high p-type electrical conductivity, 2 × 10 3 Ω −1 cm −1 of the coatings brings-in metal-like optical reflectance (>0.5) in the near infrared and a very low optical transmittance (<0.05) for a free-carrier optical absorption coefficient of 10 5 cm −1 at 2500 nm. The coated sheet acting as a UV-Blue filter and protected by an adhesive 'food-safe' polyethylene foil, provides a solar radiation intensity of above 800 W/m 2 in the dryer tray, and facilitates a temperature of 48 °C over the produce. Solar dehydration of sliced apples in 210 min, which occurred in such condition, provided it a 'shelf life' of over 8 months to date. The cellular geometry of the polycarbonate sheet makes it a sturdy cover in solar drying and inhibits convective thermal loss from the dryer tray. We report preliminary results on the kinetics of dehydration of apple slices under four modes of solar drying.