Agrivoltaic systems can significantly alter the microclimate around crops, with soil temperatures recorded at more than 20 C below those measured in directly exposed areas, according to Giuseppe Ferrara, professor at the University of Bari.

Ferrara’s team is currently taking field measurements at two pilot sites developed through a collaboration between the University of Bari, Italy’s ENEA research agency, startup Agridatalog, and other partner companies.

The first site is the Vigna Agrivoltaica di Comunità in Laterza, in the southern Italian region of Puglia, where the researchers are studying fig and olive crops. The second is an agrivoltaic installation operated by the Le Greenhouse consortium in Scalea, Calabria, where the focus is on lemon and lavender.

The two projects are designed to complement each other, Ferrara said, as they investigate different crops under different environmental conditions and with different photovoltaic configurations. The sites include fixed-tilt and tracking systems, as well as panels installed at different heights.

“We need as much data as possible to assess the feasibility of agrivoltaic systems,” Ferrara said. “This includes identifying the crops that are best suited to the technology and the environments where the benefits are greatest.”

Soil temperatures more than 20 C lower

Measurements at the Laterza site have shown substantial differences between shaded and sun-exposed soil. At around 11 a.m., soil temperatures beneath the agrivoltaic system were more than 20 C lower than in areas directly exposed to sunlight.

The figure was recorded during a period of particularly high temperatures and is therefore not representative of an average reduction. Ferrara said the difference can vary according to latitude, time of day, ambient temperature and soil characteristics.

Soil color also plays a role, as darker soils generally absorb more solar radiation and can therefore reach higher temperatures. The cooling effect could be particularly relevant in Mediterranean regions, where agricultural production is increasingly exposed to high temperatures, intense solar radiation and limited water availability.

However, the researchers are also examining how the reduction in solar radiation affects plant development.

Finding the right balance of shade and light

Reduced light availability is one of the main constraints of agrivoltaic systems. While shading can lower temperatures and potentially reduce water stress, excessive shading can limit photosynthetic activity and ultimately reduce crop yields.

The movement of the sun, and in some systems the movement of the photovoltaic panels, can help distribute radiation throughout the day. This can provide crops with sufficient light to maintain photosynthetic activity, growth and production.

Ferrrara and his team also found that crops with a lower tolerance for shade can nevertheless experience a much stronger reduction in productivity and should therefore be assessed carefully before being introduced into agrivoltaic systems.

The researchers are consequently looking not only at the amount of shade but also at how the timing and duration of shading interact with crop physiology and production.

Different crops, systems and environments

The two pilot projects are intended to generate data across a range of crops and system configurations. According to Ferrara, this variety is important because there is no single agrivoltaic design that will be suitable for every crop or location.

“Combining different areas of expertise allows us to examine the system from different angles and identify both its positive and negative aspects,” he said, noting that collaboration between different entities is essential for generating comprehensive field data rather than focusing solely on the potential benefits of the technology.

“Research should not be marketing,” he said. “It should provide information that is useful to decision-makers.”

Agrivoltaics and the Mediterranean climate

Ferrara believes the research is particularly relevant to regions with Mediterranean climates, where high temperatures and solar radiation coincide with periods of limited water availability.

The interaction between energy production and agriculture therefore needs to be considered at the site level. Crop selection is only one part of the equation; the configuration of the agrivoltaic system must also ensure that crops receive sufficient radiation to maintain an acceptable level of production.

Rather than relying on preconceived assumptions about which crops or systems will work best, Ferrara argues for continued field experimentation.

“Agriculture is changing rapidly, particularly in response to drought,” he said. “Agrivoltaics could represent another pathway that may be adopted, at least under certain climatic conditions.”

The ongoing measurements at Laterza and Scalea are intended to provide the data needed to determine where that potential can be realized and how agrivoltaic systems should be designed to balance electricity generation with agricultural production.