Parametric Design of Lens Arrays for Solar Energy

Solar energy is growing to become a major factor in the world’s energy supply. However, approximately 80% of the incident solar energy is wasted during the conversion process in a typical solar cell. There are technologies that promise to improve the efficiency of solar energy utilization, for instance concentrator photovoltaics (CPV) or concentrated solar power (CSP). However, a major complicating factor of these technologies is that they must be combined with solar concentrators that accurately follow the movement of the sun across the sky. This contributes to making them more bulky and expensive than regular solar cells.
We are working on ways of utilizing these high-efficiency solar energy technologies without requiring bulky mechanical structures to rotate the system. One way to achieve this goal is to use lens arrays – transparent polymer sheets covered with thousands of small lenses. When these lens arrays are stacked on top of each other, the movement of the sun can be followed simply using millimeter-scale relative movement between lens-arrays. Our work includes ray-tracing analysis to simulate the systems, numerical optimization to identify the best possible shape and movement of the lenses, and the fabrication of physical proofs-of-concept to demonstrate the feasibility of the approach.

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Example of how the sun can be followed using millimeter-scale movement of lens arrays

Part of a lens-array where each individual lens is a Fresnel-lens. This lens array is fabricated using grayscale lithography and designed to be part of solar tracking system