Manufacturing and operation of adsorption devices for heat transformation and desalination
Creators: name: Al Hasni, Shihab
Publisher: name: The University of Edinburgh
Year: 2024
Subjects: Adsorption cooling
Adsorption Desalination
3D printing
Adsorption Heat Transformation
Heat Exchanger Design
Energy Efficiency
Low-Carbon Energy Solutions
Sustainable Manufacturing
Clean Energy Transition

description: In recent years, research on adsorption cooling has encountered significant challenges, especially in developing nanoporous materials with improved heat and mass transfer properties and system design enhancements. These obstacles present a major hindrance to effective heat transfer within adsorption chiller beds. Overcoming this limitation has become essential, prompting concentrated efforts to develop advanced adsorption materials like metal-organic frameworks and zeotypes. However, at the material level, the current body of literature often neglects the implications of the research advancements on the production costs of the overall adsorption chiller. This neglect has resulted in a limited understanding of the actual cost of manufacturing adsorption chillers, which hinders the widespread adoption of adsorption cooling technology. To bridge this gap, this study delved into a comprehensive analysis of the manufacturing cost and end-user pricing for silica gel adsorption chillers. A thorough examination revealed that manufacturing costs are intricately tied to various components, including direct and indirect labour, production overhead, and direct materials. Furthermore, a crucial finding emerged regarding the minimum annual sales volume required for business viability, shedding light on the pivotal role of production scale in the profitability of adsorption chiller manufacturing. The study found that chillers using advanced adsorption materials such as metal-organic frameworks and zeotypes could not compete with silica gel chillers in terms of cost, establishing a clear standard for market acceptance. This comparison highlighted the economic difficulties that newer and potentially more effective adsorption materials can face. Furthermore, this study revealed that 29% of total costs are attributed to direct and indirect labour, production overhead, and direct materials. This significant percentage emphasises the importance of analysing manufacturing costs for developing new advanced adsorption materials. It underlines the necessity of transitioning from traditional manufacturing processes to advanced methods to produce adsorption chillers with lower equipment costs and minimal waste material generation without necessitating additional expenses, such as welders. Therefore, an alternative advanced manufacturing process to produce adsorption chillers is investigated, moving away from traditional metal-based methods. Stainless steel and aluminium have been preferred for constructing high-vacuum vessels due to their ability to create leak-tight welds, but they come with significant costs. They may lead to bulkier designs that limit adoption. Alternative manufacturing processes, such as plastic 3D printing, have been explored to address these challenges as a cost-effective solution facilitated by accessible desktop 3D printers. In addition, this thesis aimed to investigate 3D printing parameters to reduce porosity and develop testing apparatuses to assess leakage rates vital for evaluating the integrity of printed vessels intended for practical applications such as adsorption chillers. Research findings of this thesis revealed that stereolithography (SLA) 3D printing could create pore-free structures, achieving tight leak rates suitable for stringent requirements in thermally driven systems such as adsorption chillers and heat pumps. In contrast, fused deposition modelling (FDM) demonstrated inherent structural porosity but showed some improvement through composite resin-infusion efforts despite not meeting all application-specific needs compared to non-infused vessels. The superiority of SLA over FDM in producing vacuum-tight structures essential in thermally driven systems such as chillers and heat pumps, marking a notable advancement in the incorporation of affordable plastic desktop 3D-printing into adsorption chiller production. The feasibility of plastic 3D printing in adsorption cooling has been investigated in an experimental module, demonstrating its potential. The study found that employing plastic 3D printing to create a module for a water/silica gel adsorption heat transformer effectively replaced metal components, leading to efficient manufacturing and significant cost savings. The total manufacturing costs for the stainless-steel vessel amounted to € 267.19, covering direct material, labour, and overhead expenses, and weighed 5.2 kg. In contrast, the 3D-printed plastic vessel incurred significantly lower costs at €68.83 and weighed only 0.1 kg, highlighting a disparity in cost-effectiveness and weight efficiency when utilising additive manufacturing methods such as 3D printing technology. The design of the micro-adsorption chiller consisted of three finned metal heat exchangers enclosed within a single plastic component produced using 3D printing. The performance of the micro-adsorption chiller matched current industry benchmarks, distinguishing itself through its efficient conversion of ultra-low-grade heat at 56°C (329.15 K) into cooling temperatures. This innovative design employed an unconventional thermodynamic cycle to explore new cooling processes. The first part of this thesis explored the fundamentals of adsorption cooling by developing a micro adsorption chiller and investigating the interaction between adsorbents, such as silica gel, and water as a refrigerant in a sealed system to ensure uncontaminated circulation. This understanding is essential for grasping adsorption desalination, which originates from adsorption cooling but utilises saline water as the working fluid in an open system. In adsorption desalination, specific types of adsorbent materials selectively adsorb and release water vapour, enabling the continuous intake of saline water while producing pure water and brine at the end of the process. However, conventional methods for adsorption-based desalination encounter notable challenges related to low efficiency with ultra-low temperature heat. The last section of this thesis introduces a PCT patent application for a desalination process called temperature-induced pressure-swing adsorption (TIPS-AD), which utilises ultra-low-grade heat to produce fresh water. This desalination process has garnered more attention than other thermally driven desalination processes due to its compatibility with ultra-low-temperature heat between 40°C (313.15 K) and 50°C (323.15 K). Traditional thermally driven adsorption desalination cycles face challenges such as low specific daily water production, resulting in larger and heavier systems when using an ultra-low heat source. To address this issue, TIPS-AD offers a potential solution by efficiently managing water vapour transfers through cyclic pressure variation with minimal temperature fluctuations between the inlet and outlet streams of the adsorption bed. By using temperature variations to induce pressure swings, TIPS-AD enhances the adsorption-desorption cycles and increases the efficiency of adsorption desalination. This innovative approach overcomes the challenges posed by conventional methods and significantly improves daily water production compared to traditional desalination techniques.