Researchers from Canada’s Western University have conducted a study on romaine lettuce growth under various transparencies of cadmium telluride thin-film solar modules, revealing that Germany’s regulatory framework is the most effective for maximizing the benefits of agrivoltaics. Their experimental findings show how different levels of photosynthetically active radiation (PAR) impact crop productivity, suggesting that policymakers could enhance agrivoltaic integration by considering dynamic mandates that adapt to technological advancements and agricultural practices.
The study uniquely quantifies the effect of varying PV transparencies on PAR and crop performance, providing empirical data that could guide agrivoltaic policy-making. The controlled experiment replicated outdoor conditions in London, Ontario, with daytime temperatures at 25 °C and nighttime at 19 °C, using high-pressure sodium lights for additional illumination. Seven different transparencies of cadmium telluride solar modules—ranging from 10% to 80%—were tested, along with a control group of eight lettuce plants without solar modules.
The experimental timeline began on February 21, 2024, with plant emergence noted on day six and final thinning occurring on day 20. Fertilization commenced on March 20, 2024, with specific dosage and application adjustments. Upon measuring PAR and lettuce yields at harvest, it was determined that the 10% transparency module resulted in the lowest values for both PAR and fresh weight, while the 80% transparency module yielded the best results, demonstrating the importance of transparency in achieving optimal agricultural output.
Subsequently, the researchers assessed agrivoltaic policies in four European countries: Germany, France, Italy, and the Czech Republic. Notably, Germany’s regulatory requirement that crops maintain at least 66% of their yield emerged as the most favorable for agrivoltaic success. The findings suggest that effective policy design can have significant implications for land-use decisions and the adoption of agrivoltaic systems, emphasizing the relationship between system design and crop productivity.
The study concludes that a minimum yield requirement of 70% could be established, aligning Germany’s approach with empirical evidence. The researchers advocate for dynamic policy mandates that are reviewed every five years to remain synchronized with evolving technologies and agricultural practices. Their research is detailed in the publication “Photosynthetically active radiation complexities in agrivoltaic policy mandates: Insights from controlled environment yields under semitransparent photovoltaics,” featured in the Journal of Cleaner Production.