- Scientists at Mohammed VI Polytechnic University in Morocco have proposed the use of luminescent solar concentrators (LSCs) in greenhouses and agrivoltaic installations.
LSCs are commonly used as photonic devices in the production of fine chemicals in photomicroreactors, in dynamic “smart” windows to control light entering spaces, and for distribution of color-tuned light to enhance plant growth in greenhouses. They can also be used to improve the efficiency of solar panels. The LSCs consist of luminescent materials that are also known as luminophores, which are groups of molecules that emit light when illuminated.
The materials can be coated on the surface of a polymer or glass plate, or used as a dopant of the polymer or glass plate acting as a light guide. They can capture direct and indirect sunlight at one wavelength and re-emit it at a longer wavelength. If applied to PV, luminophores are able to capture high-energy photons that the photovoltaic panels cannot absorb and re-emit them as photons.
“Compared to conventional silicon solar cells, LSCc are more transparent, which means the necessary light for crops could be sufficiently diffused through them,” researcher Omar Moudam told pv magazine. “These devices are capable of converting ultraviolet (UV) light to visible light that could be used for crops and diffused light can be tuned for different colors such as red and blue that are favorable for plant growth.”
He said LSC devices can even produce electricity in low-light illumination. They are not heavy and are easy to for installation in greenhouses. LSCs can operate under full sunlight or shady conditions, and they don’t need to be oriented. They can be produced through simple manufacturing processes with cheap materials.
Moudam and his colleagues said current scientific research is looking into rare-earth complexes rather than common organic dyes for the development and fabrication of LSCs, as these compounds reportedly offer good photostability, high absorption coefficient, efficient quantum yield, and fewer reabsorption losses. LSCs can achieve values close to 300 nanometers in terms of Stokes shift, which is the spectral shift to lower energy between the incident light and the scattered or emitted light after interaction with a sample.
“Achieving a remarkable improvement in fluorescent quantum efficiency of rare-earth complex-based LSCs requires a deeper understanding of their molecular structures and an extended absorption up to the maximum wavelength of the visible spectrum,” the researcher said. “Highly efficient fluorophores with excellent absorption in the 430 nanometer to 780 nanometer range of the wavelength spectrum still need to be developed and improved.”
The research team presented its findings in “Recent progress in organic luminescent solar concentrators for agrivoltaics: Opportunities for rare-earth complexes,” which was recently published in Solar Energy.
In March, US solar panel manufacturer Heliene and US startup UbiQD signed a joint development agreement to make light-optimizing, energy-producing modules for agrivoltaic greenhouses. UbiQD has been developing electricity-generating windows alongside the photoluminescent light-optimizing UbiGro product.
Recent research from Eindhoven University of Technology provided a series of measurement protocols to assess the performance of luminescent solar concentrators (LSCs) with the aim of helping this technology reach commercial maturity. The research shows that LSCs can be integrated with finished PV modules without the need to modify their electronic structure. If applied to PV, luminophores can capture high-energy photons that the solar panels cannot absorb and re-emit them as lower-energy photons.
More recently, a Dutch-Australian research team developed a luminescent solar concentrator device equipped with 20%-efficient bifacial silicon PV cells. It can be used and assembled in several mosaic configurations.
Author: Emiliano Bellini
This article was originally published in pv magazine and is republished with permission.
