Leaf-inspired Solar Concentrators Could Significantly Improve Efficiency

Leaf-inspired Solar Concentrators Could Significantly Improve Efficiency
by Riko Seibo
Tokyo, Japan (SPX) Aug 16, 2024

Luminescent solar concentrators (LSCs) have been a key focus of research since their inception in the 1970s, aiming to enhance solar energy capture by converting and concentrating sunlight onto photovoltaic (PV) cells. Unlike traditional solar concentrators that rely on mirrors and lenses, LSCs can efficiently harvest diffuse light and have been used in applications like building-integrated photovoltaics, where their semi-transparent and colorful appearance adds aesthetic value.

However, scaling up LSCs to cover larger areas has faced challenges, such as the self-absorption of photoluminescent (PL) photons within the waveguide. Researchers at Ritsumeikan University in Japan have now introduced a novel "leaf LSC" design that promises to address these challenges by improving light collection and transfer to photovoltaic cells.

The newly proposed leaf LSC model tackles the scalability issue by utilizing smaller, interconnected luminescent components that operate similarly to leaves on a tree. According to a study published in the Journal of Photonics for Energy (JPE), the innovative setup consists of luminescent plates arranged around a central luminescent fiber, with the sides of the plates facing the fiber. This configuration enables incident photons to be converted into PL photons by the plates, which are then guided through the fiber and collected at its tip by a PV cell. To further boost efficiency, clear lightguides connect multiple fibers to a single PV cell, expanding the LSC's incident area while minimizing photon losses due to self-absorption and scattering.

This modular design offers several benefits. By reducing the lateral dimensions of individual modules, the researchers found that photon collection efficiency significantly improved. For example, decreasing the side length of a square leaf LSC from 50 mm to 10 mm greatly enhanced photon collection efficiency. Additionally, the modular design allows for the easy replacement of damaged units and the integration of advanced luminescent materials as they become available.

To further enhance system efficiency, the researchers incorporated techniques from traditional planar LSCs, such as edge mirrors and tandem structures, into the leaf LSC design. Their experiments revealed that the optical efficiency of these leaf-like structures can be calculated analytically based on the spectrum and intensity of incident light, using a single-spot excitation method.

"These findings demonstrate a creative approach that advances the concept of luminescent solar concentrators to effectively guide sunlight toward adjacent photovoltaic devices. By combining scalable, bio-inspired designs with enhancements in optical engineering, the authors have increased the efficiency of their devices toward what is needed for practical use," said JPE Editor-in-Chief Sean Shaheen, professor of engineering and physics at the University of Colorado Boulder, and fellow of the Renewable and Sustainable Energy Institute.

Optimizing photon collection in LSCs could lead to more flexible and scalable solar energy solutions. This advancement may revolutionize the application of solar concentrators, making them more efficient and adaptable for a variety of uses, from large-scale installations to building-integrated systems. As this technology evolves, it has the potential to greatly improve the performance of solar energy systems, contributing to more sustainable energy solutions.

Research Report:Enhanced photon collection in leaf-inspired luminescent solar concentrators