How much agrivoltaic shading is enough
Spanish researchers found that semi-transparent silicon PV greenhouses boosted tomato fruit weight by 25% while generating 726.8 kWh over two seasons, outperforming cadmium telluride PV and shaded controls. The PV-Si system balanced sunlight, temperature, and energy, showing strong agrivoltaic potential.
Researchers led by Spain’s Murcian Institute for Agricultural and Environmental Research and Development (IMIDA) have evaluated the impact of different agrivoltaic system designs on tomato crops to determine the level of shading that benefits the plants most.
“The use of four independent, identical greenhouses enables a robust assessment of their respective impacts on microclimate, crop performance, and energy generation,” the team said. “Specifically, the study aimed to evaluate the agronomic and energy performance of two commercially available semi-transparent PV technologies, with distinct light transmission patterns, in comparison with control and shading-net treatments.”
The researchers tested a semi-transparent monocrystalline silicon (PV-Si) greenhouse and a cadmium telluride thin-film (PV-TF) greenhouse against a control greenhouse and one with a shading net.
The study took place in Murcia, Spain, over two tomato-growing seasons: a 120-day winter-spring season from December 2023 to April 2024, and a 98-day spring-summer season from April to July 2024. Murcia’s semi-arid Mediterranean climate features average summer and winter temperatures of 30 C and 12 C, respectively. In both seasons, the team used polyethylene greenhouses measuring 3.9 m long × 2 m wide × 3.1 m high.
Materials under evaluation were installed on the roof and south façade of each greenhouse. The control greenhouse used only the standard polyethylene film, while the shading-control greenhouse added a shading net to selected zones. One solar greenhouse featured monofacial silicon PV modules with 50% transparency, and the other used cadmium telluride (CdTe) modules, also at 50% transparency. Each solar greenhouse had 18 modules—half on the roof, half on the façade—with nominal powers of 59 W for PV-Si and 40 W for PV-TF.
The microclimatic conditions inside each pilot greenhouse were monitored at two-minute intervals. Measurements included air temperature, relative humidity, solar irradiance, and photosynthetically active radiation,” the team explained. “Additionally, soil temperature and humidity were measured at five-minute intervals at depths ranging from 10 to 60 cm in 10 cm increments.”
The testing showed that the PV-Si technology generated an average daily energy output of 3.92 kWh in winter-spring and 4.07 kWh in spring-summer. PV-TF, meanwhile, produced 2.58 kWh and 2.79 kWh, respectively. Total energy generation across both seasons reached 726.8 kWh for PV-Si and 488.4 kWh for PV-TF.
Daily light integral (DLI), representing total photosynthetically active light received by plants each day, averaged 18.1 mol m⁻² in winter-spring and 25.4 mol m⁻² in spring-summer in the Si greenhouse. In the TF greenhouse, DLI averaged 10.8 mol m⁻² and 17 mol m⁻², respectively.
“During the winter-spring cycle, only the control and PV-Si greenhouses maintained DLI values above the minimum threshold required for optimal crop development,” the researchers reported. “Despite a similar number of fruits, the PV-Si greenhouse produced fruits with a mean weight 25% higher than the control, attributed to more favorable nighttime air temperatures and higher soil moisture.”
In winter-spring, the Si greenhouse yielded 21 fruits with an average weight of 74 g, while the TF greenhouse produced 18 fruits averaging 50 g. During spring-summer, the Si greenhouse produced 30 fruits averaging 93 g, compared with 23 fruits at 79 g in the TF greenhouse.
“Overall, the PV-Si system effectively balanced solar radiation management, thermal regulation, and energy production, demonstrating its potential as a suitable technology for agrivoltaic applications,” the team concluded.
The research findings were presented in “Comparative evaluation of semi-transparent monocrystalline silicon and cadmium telluride photovoltaics for tomato cultivation in Mediterranean agrivoltaic greenhouses,” published in Smart Agricultural Technology. Researchers from Spain’s IMIDA, Miguel Hernández University of Elche, and Italy’s University of Bari Aldo Moro have contributed to the study.
