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Integration of Solar Power and Agriculture

In densely populated areas land-use and water-use conflicts are emerging between the production of solar power and agriculture. The water used to clean solar panels is taken away from irrigation and other uses. Moreover, solar power plants have often been established in a way that has reduced the amount of land available to grow food for the people. Some countries, including Italy, have already banned the installment of photovoltaic panels on agricultural lands. With the world planning to establish 6,000 gigawatts of solar power within the next 25 years, such conflicts are likely to multiply and become much worse, unless we can find ways to dissolve them.
Could solar power installations be planned so that it would be possible to produce both food and solar power on the same piece of land? Can solar power and agriculture complement each other? Could solar power plants even be designed so, that they increase agricultural production, instead of reducing it?
In the tropical and subtropical regions the amount of sunlight is almost never the factor limiting agricultural production. During the day a single layer of crops receives up to eight times more sunlight than it can utilize for photosynthesis. The most important factors limiting the potential of agricultural production are the availability of fresh water and nutrients and the too high temperatures. As a general rule, the most optimal temperature range for photosynthesis is roughly between 25 and 35 degrees Celsius. The efficiency of photosynthesis increases steeply until 25 degrees Celsius, and then almost plateaus. After 35 degrees Celsius it begins to lessen, again rather steeply. Even though this is a rough generalization and there is significant variation between different food plant species, this is still a very useful thumb rule.
For these reasons, shade trees or shade nets have always been used in numerous tropical and sub-tropical agricultural systems. They were even more common before the colonial period, during which the European powers introduced their own farming methods, developed for colder climates. The partial shading both reduces evaporation of water from the soil and lowers the temperature of the soil and the air straight above it towards a range that is more optimal for photosynthesis. In the tropics, black surface soil often heats to 50 degrees Celsius or more in direct sunlight.
In experiments conducted in Abu Dhabi, food plants produced eight times more with the same amount of water when the temperatures were dropped from 45 degrees to 30 degrees Celsius. Could photovoltaic panels or narrow photovoltaic modules be installed on agricultural lands so that they would function just like shade trees or shading nets, providing partial shading for the crops? This way, also the water used to clean the panels would automatically become irrigation water, dropping on the roots of the plants.
What would be the best and the most affordable way of doing this? Structures consisting of bamboo, or possibly wood and bamboo? Is it possible to increase agricultural production with the help of solar power installments on agricultural land? What kind of increases in production are possible, this way, in different types of conditions and circumstances?
Somewhat surprisingly, to our knowledge (almost) no experiments along these lines have ever been conducted, anywhere. We have only been able to find one study from Britain, and in the much colder British climate the approach does not have much potential. We urge you to start or propose pilot projects testing the possibilities of this approach, and to share your ideas and results with us!

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