Beam steering electrowetting device for solar energy concentration

Khan, K 2018, Beam steering electrowetting device for solar energy concentration, Doctor of Philosophy (PhD), Engineering, RMIT University.

Document type: Thesis
Collection: Theses

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Title Beam steering electrowetting device for solar energy concentration
Author(s) Khan, K
Year 2018
Abstract Bulky mechanical tracking equipment poses challenges in solar energy concentration systems. Different technologies have been used to track the movement of the sun and concentrate its energy. However, these technologies have limitations due to equipment accuracy and steering capacity. A parabolic concentrator along with its steering equipment is heavy and bulky, and therefore it is not suitable for urban infrastructure such as on a rooftop. A thin and flat solar concentration device is much more appropriate for rooftop integration. Electrowetting controlled liquid lenses have emerged as a novel approach for solar tracking and concentration. Recent studies have demonstrated the concept of steering sunlight using thin electrowetting cells without the use of any bulky mechanical equipment. The basic concept of this technology is to change the contact angle of a liquid interface by applying an electric field. By deforming the liquid shape in an electrowetting cell, light can be steered and concentrated for solar energy applications. Effective application of this technique may facilitate the designing of a thin and flat solar concentrator. In this research work, first, a detail description is provided on theories and fundamental physics of electrowetting. It is known that electrowetting depends on several factors such as the selection of an appropriate liquid, electrode material and shape, substrate, etc. This research work presents a thorough review of recent beam steering electrowetting studies and identifies their applications and limitations. After that, it presents a comprehensive investigation on the selection of appropriate dielectric material and the deposition process. Furthermore, the research work investigates the effect of electrode position and the type of power supply on the electrohydrodynamic behaviour of liquid in electrowetting. Previous studies on electrowetting device have been able to demonstrate only one-axis steering of sunlight. This study designs an electrowetting device for two-axis tracking to effectively track the sun. In this research, a novel simulation model is developed in commercial software COMSOL Multiphysics to predict the liquid-liquid interface behaviour of electrowetting cell as a function of varying parameters such as applied voltage, dielectric constant, fluidic properties and electrode shape. The model simulates the electric field and couples it with microfluidic simulation to derive the deflection of the liquid-liquid interface using Lippmann-Young equation. The model can be used to design the appropriate electrode arrangement to maximise transmission and focusing accuracy. After the simulation study, the electrowetting solar energy steering and concentration device is fabricated. A proposed hexagonal electrowetting cell that mimics the structure of insect compound eyes has been studied. A pattern of hexagonal shape structure facilitates a planar 360° steering of sunlight. The study identifies appropriate liquids and materials for the device. It also identifies the appropriate geometry and fabrication process to achieve an efficient electrowetting solar concentration device. The findings of this research work will facilitate the development of a low-profile flat solar concentration device.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Engineering
Subjects Energy Generation, Conversion and Storage Engineering
Microelectromechanical Systems (MEMS)
Keyword(s) Electrowetting
Solar Energy Tracking
Solar Energy Concentration
Beam Steering
Liquid Lens
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Created: Thu, 13 Jun 2019, 09:02:10 EST by Adam Rivett
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