Holograms increase solar energy yield

PICTURE: A holographic light collector separates the colors of the sunlight and directs them to the solar cells. view More

Photo credit: RK Kostuk, University of Arizona

The energy available from sunlight is 10,000 times greater than that required to meet the world’s energy needs. Sunlight has two main properties that are useful in designing renewable energy systems. The first is the amount of energy that falls on a solid area such as a person’s floor or roof. This amount varies with the time of day and the season. The second property is the colors or spectrum of sunlight.

One way to capture solar energy is to use solar cells that convert sunlight directly into electricity. In a solar module that people place on their roofs, many cells are assembled on a rigid plate, connected to one another, sealed and covered with protective glass. The solar cell works best when certain colors of sunlight fall on it and when the entire area is covered by photocells. However, some panel area is required to connect the cells, and the shape of the solar cell may not allow all of the remaining panel area to collect sunlight. These effects make the solar panel less efficient than it could be. The efficient use of sunlight on a solar panel is crucial for the efficient use of solar energy.

Researchers at the University of Arizona recently developed an innovative technique to capture the unused solar energy illuminating a solar panel. As reported in the Journal of Photonics for Energy (JPE), they have created special holograms that can be easily inserted into the solar panel package. Each hologram separates the colors of the sunlight and directs them onto the solar cells in the solar panel. This method can increase the amount of solar energy that the solar panel converts by about 5 percent over the course of a year. This reduces both the cost and the number of solar panels needed to power a home, city, or country.

The research was supported by the QESST Engineering Research Center, sponsored by the US National Science Foundation and the US Department of Energy, to meet the challenge of transforming power generation and sustainably meeting growing energy needs.

Inexpensive, sustainable design

The holographic light collector was designed by PhD student Jianbo Zhao under the supervision of Raymond K. Kostuk, Professor of Electrical and Computer Engineering and Optical Sciences, and, in collaboration with his PhD student Benjamin Chrysler, combines an inexpensive holographic optical element with a diffuser. The optical element is located symmetrically in the center of the photovoltaic module in order to achieve maximum effective light collection.

The team calculated the annual improvement in energy yield for Tucson, Arizona and presented a reproducible method for evaluating the energy collection efficiency of the holographic light collector as a function of the sun angles at different times of the day, different seasons and different geographic locations.

According to Sean Shaheen, Editor-in-Chief of JPE at the University of Colorado Boulder, the collector and the method associated with it are particularly noteworthy for being inexpensive, scalable and powerful: “Increasing annual solar energy yield by about five percent. Activating this technique could be great Have an impact when scaled to a small fraction of the 100 gigawatts of photovoltaics installed worldwide. Professor Kostuk’s team has demonstrated its holographic approach with an inexpensive gelatin-based material that can be easily manufactured in large quantities Gelatin is normally derived from animal collagen, advances in laboratory versions have made it likely that synthetic alternatives could be used on a large scale. “


Zhao and his co-authors are encouraged by the results of their research and look forward to future work to further optimize the energy output of holographic light harvesters through experimental evaluation of materials.

Read the open access report: J. Zhao, B. Chrysler, and RK Kostuk, “Low Concentration Holographic Optical System to Increase Light Collection Efficiency of Regular Solar Modules”, J. Photon. Energy 11 (2), 027001 (2021), doi 10.1117 / 1.JPE.11.027002

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