Concentrators

The Objective

FIG. 2.1 GEN-1 Concentrator Lens. Single concentrator shown without a primary mirror on its back. Instead, it uses many radially directed facets and TIR. Note, it is actually possible to see through the lens form angles greater than about 3 degrees off axis but for lesser angles it is effectively mirrored. Note, the secondary mirror on the front has been removed to expose the focal region for ease of viewing here—without the secondary ≈ 50% of the sunlight is focused by TIR. The GEN-2 lens will have no mirrors.

FIG. 2.2 Wedge Concentrator Lens. This is a Building Block element for the entire lens. Sunlight enters the wedge concentrator lens and is slightly refracted at the first surface. It then is reflected by Total Internal Reflection (TIR) up to three times before it finally reaches the focal region. Many facets are arranged about the optical axis to make a concentrator lens. Although hard to see in the above image, the facet apex angle and the surface vary in a complicated and continuously way across the lens. In the GEN-1 lens a tiny mirror at the upper surface was required, however, the GEN-2 lens will not require any mirrors at all.

XE’s objective is to develop the lowest loss compact concentrator commercially available in order to obtain huge gains in solar panel performance. Our GEN-1 efforts have thus far provided a new type of patented concentrator that removes most of the loss mechanisms of a mirrored concentrator. Our next iteration, GEN-2, will extend the lens design by using only one refractive process and multiple high-efficiency Total Internal Reflections (TIR)---no mirrors. The result will be a device that is easy to fabricate into an array using only a single molding step, which allows for a very low-cost and robust device.

Additionally, we intend to further extend our engineering by using advanced accurate and precise manufacturing to achieve total lens losses of no more than 5%. This is a very hard engineering objective to meet, especially when one realizes that the typical state-of-the-art concentrator has between 10%-20% loss! However, if we are successful it will allow XE to build solar panels that provide about 10% more power efficiency (from about 25% to 29% panel efficiency) than the best current state-of–the-art solar concentrator lenses that are produced by other technologies. This is a staggering increase in total conversion efficiency of and would take many years to replicate if the efficiency gain was to come exclusively from incremental solar cell improvements!