Studies on Solar-Driven Desiccant Dehumidification Systems using Novel, Less-Corrosive Desiccants and Improved Packing Materials

Abstract

In response to the high energy demands in air-conditioners that exacerbate environmental challenges, liquid desiccant dehumidification systems (LDDS) have emerged as a more energy-efficient alternative, offering enhanced control over temperature and humidity. However, the widespread adoption of LDDS is hindered by the corrosive nature of liquid desiccants on metal components. Recognizing the critical role of desiccant materials in the sustainability of these systems, this study focused on developing low-corrosive desiccant solutions, improving the design of packed bed LDDS and geometrically modification of evacuated tube solar collector (ETSC) to improve thermal heat supply during desiccant regeneration. It also addressed challenges such as desiccant carryover and high pressure drop in packed bed dehumidifiers by modifying the packed bed geometry and synthesizing hydrogel beads through the crosslinking of sodium alginate with the desiccant solution. Empirically optimized mixture of 55% HCOOK and 45% MgCl2 at a 40% concentration was proposed, reducing the corrosion rate by 53.6% compared to pure MgCl2. This new desiccant solution was then used to create sodium alginate hydrogel beads, which were tested at various concentrations. The study also tested three different ETSC models, each with one inlet but varying numbers of outlets, to enhance regeneration heat and collector efficiency. Experimental setups for the packed bed LDDS were operated at a dehumidification capacity of 1.5 TR, and parametric studies were conducted to evaluate thermal and flow characteristics. A new corrugated wire mesh design was introduced as a contacting media, enhancing moisture removal and decreasing pressure drop or desiccant carryover. The hydrogel beads were tested in a fixed bed dehumidifier system, and response surface methodology (RSM) was used to optimize inlet parameters. Experimental validation showed a deviation of ±4.7%, confirming the model's robustness. An economic evaluation revealed that the proposed ETSC model had the shortest payback period of 2.5 years, and the integration of a solar-assisted regeneration system reduced energy costs by 22.8% compared to traditional vapor compression systems, achieving a return on investment within 1.8 years. This work highlights the potential of LDDS as a sustainable alternative to conventional air-conditioning systems, with significant improvements in efficiency, cost-effectiveness, and environmental impact through material optimization and innovative designs.