Performance augmentation of a solar thermal desalination system using different floating absorber plates

Abstract

Interfacial evaporation is known to boost the evaporation rate compared to conventional bulk evaporation, as energy conversion and vapor generation simultaneously occur at the air–liquid interface. This work presents the investigation details on the design, fabrication, and testing to determine the performance of a floating absorber structure with the sole interest of maximizing the evaporation rate. Polyvinyl alcohol cloth is the wicking cum absorber material, while extruded polystyrene sheet is the floating structure cum thermal insulator. Phase I of the study involves the comparative study between bulk and interfacial heating and the effect of different types of patterns with the same area on interfacial heating with a single absorber. Phase II involves the effect of multiple absorbers on interfacial evaporation. To identify a better design, different absorber configurations (single, patterned, multiple, and multiple blocks with full coating and patterns) were compared to bulk heating. The study highlighted the improvement in evaporation rate achieved using floating absorbers by 43% and 56% for single and multiple absorbers under one sun illumination compared to bulk heating. Also, a multiple absorber design yields a 10% higher evaporation rate than a single absorber. An extended analysis with and without black coating on multiple absorbers design indicates an improvement of 17% evaporation efficiency compared to bare multiple absorbers. In selecting a suitable pattern embedded on the single absorber, the stripe-type pattern resulted in a 21% improvement in evaporation rate than the bare absorber among the four patterns tested. The multiple absorbers with stripe patterns obtained an evaporation rate of 1.17 kg m⁻² h⁻¹ under one sun (1 kWm⁻²) irradiation. Further, the multiple absorbers with stripe-type patterns obtained an evaporation rate of 1.69 kg m⁻² h⁻¹ under 1.5 sun irradiation (1.5 kWm⁻²).