Montpellier solar food farm

Montpellier solar food farm

Montpellier solar food farm

This Solar Food Farm in Montpellier (France) is a successfull research project.

It took a while to find the balance between maximizing the amount of electricity produced by the solar panels and maintaining the productive capacity of the farm.

But after three growing seasons they had their answer: yes, balance was possible. But not quite for the reason they expected.

Montpellier research

It was the Goldilocks Principle at work: too much shade hurt the crops, too little hurt electricity generation. Everything had to be just right. Could this balance be achieved? Variables the researchers identified included:

  • The proper angle or tilt of the PVPs
  • The proper spacing between solar panels
  • Making adjustments for localized conditions (such as latitude)
  • Choosing between fixed panels or panels on trackers (cost is a factor)
  • The proper height of the PVP array
  • Engineering issues involved with the construction of the structure that holds the PVPs in place (must be durable)

By the end of three growing seasons they had their answer: yes, balance was possible. But not quite for the reason they expected.

Productivity

Not surprisingly, the crops under the full-density PVP shading lost nearly 50 percent of their productivity compared to similar crops in the full-sun plots in Montpellier. However, the crops under the half-density shading were not only as productive as the control plots;

in a few cases they were even more productive!

The reason for this surprising outcome, according to Dr. Hélène Marrou, who studied lettuce in the plots, was the compensating ability of plants to adapt to lower light conditions. She reported that lettuce plants adjusted to decreased levels of radiation by:

  1. an increase in the total plant leaf area
  2. an increase in total leaf area arrangement in order to harvest light more efficiently

Water efficient

There was also good news to report on the water front for dry area like Montpellier.

They showed in this experiment that shading irrigated vegetable crops with PVPs panels allowed a saving of 14-29% of evapotranspired water, depending on the level of shade created and the crop grown. In the context of global warming and water shortage, reducing water demand by shading plants could represent a big advantage in the near future.

While commercially available solar panels operate at 15 percent efficiency, the intrinsic efficiency of photosynthesis is “quite low” at roughly 3 percent (which is why companies are trying to “improve” it). This makes PVP systems more attractive to landowners than farms from a solar radiation perspective, especially at big scales. Combined, however, silicon and carbon systems can be very efficient.

The scientist say that more research is needed, including questions about rain redistribution under the panels, wind effects on the crops, soil temperature changes, the effect of dust from farming on PVP efficiency, and the validity of the results for various latitudes, and a special focus on plants that have a demonstrated ability to compensate for reduced light conditions

Early results were very hopeful

“As a conclusion,” Dr. Marrou wrote, “this study suggests that little adaptation in cropping practices should be required to switch from an open cropping to an agrivoltaic cropping system and attention should be mostly focused on mitigating light reduction and on plant selection.”

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