Optofluidic Solar Concentrators Using Electrowetting Tracking

We report a novel optofluidic solar concentration system based on electrowetting. With two immiscible fluids (water and silicone oil) in a transparent cell, we can actively control the orientation of the water-silicone oil interface via electrowetting. The naturally-formed meniscus between the two liquids can function as an optical prism and hence a beam deflector. With 1wt% KCl and 1wt% SDS (Sodium Dodecyl Sulfate) added into the DI water, the orientation of the water-silicone oil interface has been successfully modulated between 0° and 26° that can deflect and steer sunlight within the incidence angle of 0°–15°. Without any mechanical moving parts, this dynamic liquid prism allows the device to adaptively track both the daily and seasonal changes of the sun’s orbit, i.e., dual-axis tracking. An integrated dual-axis tracker and solar concentrator can be constructed from the optofluidic beam deflector in combination with a fixed optical condenser (Fresnel lens). The beam deflector consists of liquid prism arrays and electrowetting modifies the orientation of each individual liquid prism in order to steer the deflected beam normally towards the Fresnel lens as the incident sunlight beam shifts. Therefore, electrowetting tracking can adaptively focus sunlight on a concentrating photovoltaic (CPV) cell sitting on the focus of the Fresnel lens as the sun moves. This approach can potentially reduce capital costs for CPV and increases operational efficiency by eliminating the power consumption of mechanical tracking. Importantly, the elimination of bulky tracking hardware and quiet operation will allow extensive residential deployment of concentrated solar power. In comparison with traditional silicon-based photovoltaic (PV) solar cells, the electrowetting-based self-tracking technology will generate ∼70% more green energy with a 50% cost reduction.