The design and optimization of critical parameters for a non-mechanical solar tracking system, which is controlled by electrowetting principles, is outlined. By removing heavy and bulky mechanical moving parts of conventional motor-driven solar trackers, our microfluidic solar tracker offers low-cost, lightweight and high-efficiency solar energy collection. Exceptionally wide beam steering performances up to α = ±89°, covering a whole-day solar tracking, were observed at a low apex angle of φ = 30° for a quad-stacked prism configuration. This shows a fivefold increase over a single prism at the same apex angle. With low apex angles needed for wide solar tracking, our system is able to lower the voltage requirements that is helpful in avoiding problems such as contact angle saturation and hysteresis usually seen in electrowetting device operation. The reflection loss was also studied for various prism configurations. Our fundamental study showed that the even-stacked prism modules are able to effectively minimize the loss by reducing the refractive index ratio, r = n2/n1 at the last interface with air. To further reduce the loss, the addition of anti-refractive thin films at each interface following Rayleigh’s principle was proposed. This results in an additional reduction of the loss, indicating 4.4% for the case of a quad-stacked prism.
The effect of the proposed solar tracking system on system level properties such as solar concentration factor is also studied. The arrayed prism panel is capable of solar concentration as high as 2032× at α = 0° and approaching roughly 1138× for high incident angles when the water/N-LAK21 system is used. This shows marked improvement upon using our tracking system as opposed to just a Fresnel lens. The dispersion effect of materials was then studied on concentration factor. Our data suggests that less dispersive materials with higher Abbe numbers produce higher concentration factors.
Most importantly, the elimination of bulky mechanical tracking systems and the use of low-cost, lightweight and silent microfluidic tracking systems would be ideally suited for rooftop usage in residential areas. Upon successful implementation, this revolutionary beam steering technology has the potential of high solar energy harvesting and may not only be economically viable, but also sustainable and practical for domestic usage.