As countries around the world search for sustainable energy sources, renewable energy such as photovoltaic solar panels are in high demand. However, deploying large solar parks to power the world's growing population is difficult and can take up a lot of space.
Researchers at the Samueli School of Engineering at the University of California, Los Angeles (UCLA) have now explored a viable new application for solar cells that does not require large land plots. They have developed a prototype miniature greenhouse with a roof made of semi-transparent solar cells that resulted in better plant growth than a traditional greenhouse.
Semi-transparent organic photovoltaics is an emerging solar energy harvesting technology with promising applications, such as rooftop power supply for green greenhouses. However, the main drawback that has prevented its widespread use so far is its lack of stability.
Organic solar cells tend to degrade faster than their inorganic counterparts because sunlight can cause organic materials to oxidize and thus lose electrons.
The team has developed a strategy to augment semi-transparent organic solar cells that are based on carbon-based materials, as opposed to the inorganic substances in conventional devices. They added a new ingredient: a layer of a natural chemical called L-glutathione, which is sold as an over-the-counter antioxidant dietary supplement.
The researchers found that the extra layer prevented the other materials in the solar cell from oxidizing and breaking down. It extended the life of solar cells, improving their efficiency and allowing sunlight to reach the plants in a dollhouse-sized greenhouse prototype.
In tests, organic solar cells with this protective layer maintained efficiency above 80% after 1,000 hours of continuous use, while those without it dropped to less than 20% over that time.
The researchers also followed the growth of common crops, such as wheat, beans, and broccoli, in two miniature greenhouse prototypes. One had a transparent glass roof with segments of inorganic solar cells, and the other had a roof made entirely of semi-transparent organic solar cells.
The semi-transparent organic PV demonstrated a power conversion efficiency of 13.5% and a mean visible transmittance of 21.5%.
In addition, the team found that crops in the greenhouse with the organic sunroof grew surprisingly more than those in a normal greenhouse. The researchers suggest this is because the L-glutathione coating blocks ultraviolet rays, which can inhibit plant growth, and infrared rays, which can cause greenhouses to overheat and indoor plants need more water.
We did not expect organic solar cells to outperform a conventional glass-roofed greenhouse. But we repeated the experiments several times with the same results, and after further investigation and analysis, we found that plants do not need as much sunlight to grow as we had originally thought. In fact, too much sun exposure can do more harm than good, especially in climates like California where sunlight is more abundant.
Yepin Zhao, lead author of the research and a UCLA postdoctoral fellow
Request your 100% personalized proposal completely free
quote now
Ariel Ramirez
March 30, 2023