The initiative is part of a project supported by the Regional Ministry of University, Industry, Energy, and Innovation of the Andalusian Government. Specifically, two commercially available semi-transparent photovoltaic module technologies have been tested. The authors of the study, published in the journal 'AgriEngineering', argue that this is an interesting alternative for coping with increasingly adverse weather conditions. Reducing the temperature is key to preventing heat stress in plants, as observed in the trials.
The balance between light and electricity production
Ensuring a greenhouse maintains its productivity while simultaneously generating energy is no easy task. The challenge lies in determining how much solar radiation should reach the crops and how much should be absorbed by the solar panels. Too much sunlight reduces electricity generation; too little hinders plant photosynthesis. To find this balance, researchers in Jaén, Spain, compared two commercial solutions: one composed of cadmium telluride modules, which transmit about half of the solar radiation, and another made of amorphous silicon, which transmits only 20%. The choice between these technologies will depend on the specific crop , as the optimal balance varies considerably between the two.
A rigorously controlled experiment
To draw reliable conclusions, two mini-greenhouses of approximately two square meters each were installed, each equipped with one of the technologies, along with a third greenhouse with a conventional control covering. The quantity and quality of light passing through the panels, humidity and temperature of both the air and the substrate, COâ‚‚ levels, and the electricity generated by each panel were measured every five minutes. This process was carried out over five consecutive growing cycles of tomatoes and lettuce over the course of a year. The level of detail in the collected data allowed for the observation of changes barely perceptible in a conventional trial.
Lower temperature, higher humidity, and shorter watering intervals
The results confirm that installing the panels not only generates electricity but also transforms the plant's internal environment. A temperature drop of up to five degrees Celsius has been recorded, a significant decrease during peak heat periods. Furthermore, relative humidity increases, causing water to evaporate much less easily. Savings in irrigation requirements were 31% with cadmium telluride modules and over 60% with amorphous silicon modules. This reduction in water loss is due to the cooler environment and less exposure to evaporation.
Another key finding is the quality of the filtered light. The cadmium telluride panel preferentially allows blue and red wavelengths to pass through, which are most beneficial for leaf development. This explains why, even though less radiation reaches the plants, they are not affected in the same way. The crops respond by expanding their leaf surface area and lengthening their stems, an adaptive behavior that has been observed in detail.
Adaptation to heat and expansion into rural areas
The plant's ability to adapt to lower light intensity has been verified in trials. This is not a deficiency but a morphological change that allows it to better capture available light and reduce photostrain. This opens the door to integrating solar energy into protected crops without sacrificing acceptable yields. Although the prototypes have been tested in an area of ​​Jaén, the semi-arid climate there shares many similarities with that of western AlmerÃa, one of the world's largest horticultural production centers.
The next step is already underway: research continues in an experimental greenhouse, more like a commercial one, located in the Region of Murcia. Other types of photovoltaic technology and their performance in the field will continue to be compared. At the same time, the team is studying the integration of these technologies in olive groves, a crop characteristic of the Andalusian landscape. The possibility of obtaining a double economic return thanks to the additional electricity makes agriculture a sector less dependent on a single source of income, which is especially useful in years of poor harvests.
Finally, it's worth noting that this project has been funded by the Regional Government of Andalusia and is supported by the GLASS project of the Ministry of Science and Innovation. Agrivoltaics is emerging as a cost-effective way to avoid competition between agricultural and photovoltaic land use. New generations of solar greenhouses capable of generating energy could transform greenhouses into energy cells, protecting crops and providing a competitive advantage in the context of climate change and water scarcity.
