Coatings for solar panels that increase efficiency

Anti-reflective coatings are a key area for solar panel efficiency gains because any light that is reflected cannot be harvested. Moth-eye inspired anti-reflective coatings have been validated as a potential solution, but quantitative evidence in deployed settings has been lacking. This corporate-academic study in Japan provides vital proof of concept in the field. The test protocol compared effects in Tokyo, a site with more diffuse solar radiation, and Phoenix, a site with more direct solar radiation. In this case the anti-reflective coating is constructed from acrylic resin, and provided notable efficiency gains. The gains are shown to be 5-6% depending on the geographic location of the solar panels; in this field, such gains are very substantial. Additionally, the team demonstrated a high-throughput roll-to-roll process for nanoimprinting the film, enabling cost effective mass-production. Research is now focused on optimization for various types of solar panels, and exploration into applications in windows and displays.

Key Differentiators

This study was the first to provide quantitative data, the ultimate requirement for engineering implementation. The researchers showed quantitative analysis of the effect of the ratio of diffuse solar radiation to total solar radiation (diffusion index) and incident angle, as well as the effect of vertical tilt angle on the conversion efficiency. This data proved ultralow reflections for broadband wavelengths and omnidirectional light incidences. Spectral matching with the PV modules can also be achieved, providing the light-harvesting components with the wavelengths of light that they best harvest. The introduction of an industrial-scale manufacturing methodology places this technology close to market.

Biomimicry Story

Moth eyes have a remarkable anti-reflective ability that is vital to their sight abilities in nocturnal activity. In a broad search of inspiring organisms, moths proved to have the most effective capabilities for the characteristics of solar panels. Numerous methods have been tested to produce moth-eye mimetic coatings, and in this case an acrylic resin was used to achieve the correct patterning.   See also: Mitsubishi Rayon Co. Ltd.; Tokyo Metropolitan University

Challenges Solved

Surface reflection as a source of energy loss; quantitative analysis of the effect of various sunlight characteristics on conversion efficiency.