Impacts of Transparency in Agrivoltaics Lettuce Cultivation Using Uniform or Non-Uniform Semitransparent Solar Photovoltaic Modules

Abstract

Although agrivoltaic lettuce production appears promising, the literature is unclear what effects the type of illumination from agrivoltaics have on production if transparency is held constant. To fill this knowledge gap, this study undertakes a comparative analysis of lettuce agrivoltaics employing two different illumination methodologies: uniform illumination facilitated by thin film photovoltaic modules (type 1) and non-uniform illumination provided by semitransparent c-Si modules featuring rows of solar cells and transparent glass elements (type 2). Specifically, this study evaluates the growth of lettuce under two different bifacial c-Si-based PV module types (44% and 69% transparent clear solar PV modules) as well as Cd-Te thin film modules of similar transparencies (40% and 70% transparency). All modules were evaluated for photosynthetically active radiation (PAR) and the plants were monitored for gas exchanges including net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate as well plant height, number of leaves and fresh weight as a function of agronomic and physiological performance under agrivoltaics. The 69% transparent c-Si PV modules demonstrated minimal impact on lettuce yield and plant physiology, maintaining performance close to that of a control without PV, which is representative of traditional cultivation systems. The current study reveals that non-uniform 69% transmisivity results in a maximum yield enhancement of 3.6%, while uniform illumination through thin-film modules loses 6% compared to the control. Scaling agrivoltaics across all lettuce farms in Canada with 69% transparent PV modules would result in 1,200 MW of PV. A 3% increase in lettuce yield under the 69% transparent c-Si modules would provide a CAD$20 million annual bonus for Ontario’s lettuce farmers for crop value alone in addition to CAD$30 million expected from leasing the farmland for agrivoltaics. These findings underscore the promise of non-uniform semi-transparent solar PV modules in agrivoltaic applications, offering a sustainable balance between agricultural productivity and energy generation.

Keywords: agrivoltaics, silicon photovoltaics, lettuce, bifacial photovoltaic, semi-transparent photovoltaic, thin film photovoltaics