Arable land is at a record high. Since the end of the ice age, humans have cleared over one-third of the planet’s forests and two-thirds of the wild grasslands, much of which is used for agriculture. As the global population of 8 billion as of November last year –continues to grow, there’s a growing demand on the land to produce more food and clean energy.
In areas like Yakima County, Washington, in the United States, this has led to the need for space since land-hungry solar arrays eat the available fields. In the last month, the Washington state’s Energy Facility Site Evaluation Council approved plans to cover 1,700 acres of land for agriculture by installing solar photovoltaic (PV) panels in a way that shook off the county’s moratorium on solar installations and raising concerns among the community about the long-term effects of losing land for crop production.
However, an upcoming study by an academic institution at the University of California, Davis, demonstrates farmers could soon be capable of harvesting energy and crops together on the same terrain. Researchers found that the bands of the visible spectrum could be harnessed and filtered separately–blue light waves that produce solar power, and red light waves for growing vegetables and fruits, allowing for the best land utilization, reducing the stress on crops, and reducing waste.
“Why does [agriculture] have to be a zero-sum game if we can optimize the land for both?” Asks Majdi Abou Najm, an Associate Professor in the Department of Land, Air and Water Resources at UC Davis and an Institute of the Environment fellow who wrote the paper with Majdi Abou Najm.
Photons, the particles that comprise light, have distinct characteristics; as he explained, blue particles have more energy than red ones, resulting in light having shorter wavelengths and a higher frequency. In addition, blue light gets the jolt required to generate power; the additional pulses produce more heat.
“From a plant perspective, red photons are the efficient ones,” Abou Najm says. Abou Najm. “They don’t make the plant feel hot.”
With the help of computer models, Abou Najm and lead author Matteo Camporese, an associate professor in the Department of Civil, Environmental, and Architectural Engineering at the University of Padova, found that the application of the red light spectrum to plants increases carbon assimilation, the process that allows them to metabolize carbon dioxide and convert it into organic compounds – while the transpiration rate is reduced. Also, in the more astonishing spectrum, “crops can get the same amount of CO2 using less water,” Abou Najm says.
Their research was influenced by hydroponic light systems used in indoor farms, “those come at a high energy cost,” says Abou Najm. “We decided to use sunlight as our input.”
One of the significant purposes of the study, according to Abou Najm Abou Najm, the study’s primary goal is “to motivate the industry to create a new generation of solar panels.” Camporese believes there is potential in organic solar cells that, in contrast to the shiny metallic silicon-based panels, originate from carbon-based materials. The cells are translucent and thin; cells are sprayed like film on surfaces such as glass. According to him, the technology can be utilized to create photo-selective PV cells that block blue light to produce power and transmit the red spectrum to the crops planted directly below.
The rapidly growing field of agrivoltaics, where land is used for energy generation and food production, actually increased land efficiency through interspersing conventional solar arrays between areas of plants. (Solar grazing is a variant that allows livestock to graze among the solar arrays.) The angled panels protect plants and other heat-sensitive fruit from the day’s most vital sunlight; the plants, in turn, release moisture and reduce the temperature below the cells that are sensitive to heat, increasing their efficiency.
However, the plants grown by agrivoltaics are cultivated in the shade, meaning “less light typically means less yield,” Camporese says. This limits the number of solar panels and plants in cogeneration farms. However, translucent arrays permit full field coverage, both maximizing the use of land and providing a significant boost to productivity per acre.
In May, the researchers conducted a brief field experiment of photo-selective cropping at the UC Davis Agricultural Experiment Station. The team planted processing tomatoes — a typical Sacramento Valley crop–on small, similar-sized plots. One was covered using a photo-selective red filter, one with blue, and a fourth was left uncut as a control.
After about four months, with an unprecedented heat wave in September, The two filtered plots yielded around one-third less than the unfiltered one. But when it was sorted according to quality–ripe, unripe, or “bad”-the filtered plot had two times the number of rotten tomatoes. “So the filters helped reduce heat stress,” Abou Najm says. Abou Najm. It also “cut [crop] wastage by more than half.”
He states that including energy generation and the net profit would offset the lower yield. When you combine solar and crop production, “100 percent becomes a deficient number when you can get 120 or 140 percent yields.”
And for regions and countries that are tightening their grip on the land, this boosts productivity even more critically, particularly when you consider that producing green energy takes 10x more acres in terms of energy than fossil fuels.
Abou Najm is also adamant about the canopied method, as farmers can build resilience to climate change. The sun’s filtering helps the soil hold water and protects farm workers from the harsh sun’s rays. Less transpiration means that less water is required to grow crop production. In addition, by producing the power themselves, farmers can lower the rising energy cost and push the industry towards moving towards electric vehicles and machines as well, he says.
“By 2050, we’ll have [an additional] two billion people on this planet, and we’ll need 60 percent more food, 40 percent more water and 50 percent more energy” that is currently being produced, according to Abou Najm. Research must take place at a revolutionary scale to meet these growing needs.
By maximizing the spectrum of sunlight, “we’re optimizing an endlessly sustainable resource,” the expert says. “If a technology kicks in that can develop these panels, then the sky is the limit on how optimized we can be.”