Microfluidic tunable liquid prisms for solar beam steering and concentration

Concentrated photovoltaic (CPV) is an alternative solution to reduce the cost of solar PV systems by using less semiconductor materials. One key component in CPV systems is a solar tracker that enables to keep them in an optimal position to maximize solar concentration. However, CPV solar trackers typically are expensive, often unreliable and require lots of power, because they are composed of bulky, complex and heavy mechanical moving parts such as motors and supporting frames. These bulky and heavy tracking components make CPV systems difficult to be installed on building or residential rooftop. We present a microfluidic tunable liquid prim panel that enables to track the daily and seasonal sun's motion and concentrate steered sunlight onto a solar cell for solar power generation. The panel consists of arrayed tunable liquid prisms. An apex angle in each prism is tuned by electrowetting, which allows incident light to be adaptively steered and focused onto a solar cell. Our systems consume very little power in the range of ∼mW as well as require no heavy and expensive supporting hardware or moving parts for solar tracking. We discuss concept, design and analytical estimation of the system performances. It is able to steer incoming light beam with incident angle up to α = ± 70°, while only causing additional optical reflection loss about 5 ~ 10%. We have fabricated the liquid prism with a 1cm × 1cm aperture area and demonstrated apex angle modulation up to φ = ± 30°, and beam steering up to Δα = 14.6°. By eliminating expensive and inefficient motor-driven mechanical solar trackers, our optofluidic solar tracking system can offer a cost-effective CPV system with low power consumption for residential or building rooftop installation.