The Resurgence of Solar Agriculture: Harvesting food and energy side by side
The French National Institute for Agricultural Research into Agrovoltaic in Montpellier in 2010 found that too much shade hurts the crops but too little shade reduces electricity generation. Both the spacings between the panels and the tilt of the array is key to maximising both the crop and electricity generation.
The study compared the impact of different levels of sun on crops (lettuce) by growing crops under full sun, standard density PV array and half-density PV array. After three growing seasons they found the crops under the full-density array had lost nearly 50% productivity. They found that the crops under the half-density array had not only grown as well as the crops under full sun but were more prolific. They found that the lettuce had adapted to the half sun by increasing the leaf size. It had the added benefit of reducing the water demand compared with the full sun crop with a 14-29% saving of evapotranspired water.
A German study installed 720 bi-facial solar panels to catch the rays from above and below. The panels were mounted high off the ground to increase the sunlight to the crops and enable large farm equipment to move under the arrays. They planted wheat, celery, potatoes and clover under the arrays. The combined yield, after the first year, was 60% higher per square meter then if two separate fields had been used to split the two.
Computer modelling has indicated that the installation of solar panels on grape farms in India would increase the economic value of the farms by 15 times with no decline in grape yields due to the grape tolerance to shade. Widespread application across India could generate enough energy to supply 15 million people with electricity.