The Surprising Synergy of Cropping under Solar Panels

Agrivoltaics can be scaled right from individual households having rooftop or yard gardens to large farms and plantations. image source: Divya Singh

The primary challenge faced in making agriculture sustainable is its requirement of land. Agriculture effectively locks out land resource. Any piece of land devoted to cultivation cannot be simultaneously subjected to any vertical development. The same deterrence is faced by another industry - Solar Energy. The requirement of unused land that cannot be put to any other use is a significant deterrent against the expansion of the Solar Energy sector. Unlike plants, solar panels are becoming increasingly efficient year-by-year. However, its ubiquitous implementation is still distant. The primary criterion for a site to qualify for Solar Panel installation is the provision of an unobstructed surface to intercept the incident sunlight. Thus, agriculture and solar energy harvesting exert a similar land demand on those who wish to undertake them. However, when the two are combined, they perform surprisingly well, as recent research has shown. Vertically stacking small plants on custom-designed frames fitted with root drips is already utilising the ability of many plants, especially vegetables to prosper in shade or diffused indirect illumination. This technology, called aeroponics, has already been around for quite some time. However, the cool shade under Solar Panels, if ever utilised, was only considered fit to grow fungi. It seems counterintuitive that a natural lifeform and a man-made inorganic technology would cooperate rather than compete when they both depend on the same resource.

A September 2019 research study carried out by a team led by University of Arizona's Greg Barron-Gafford, published in Nature sustainability discovered that when certain crops are grown under Photovoltaic panels, they prove multifacetedly mutually-beneficial. Their research entailed meticulously observing, recording, and studying various internal and ambient parameters such as soil surface temperature, panel temperature, plant's water uptake, ambient moisture, physiological functions in plants, and plant biomass yield. Many plants showed an increase in the edible biomass (equivalent to increase food productivity), a reduction of drought stress experienced by the plants, and a decline in the heat stress on the solar panels. The researchers asserted that this phenomenon could prove instrumental in combating drought-like conditions that are predicted in the coming months and years, owing to global warming, heatwaves, and erratic precipitation patterns. They stressed the particular pertinence of the study to areas exhibiting climate patterns akin to that of Southwestern United States.

The shade offered by the panels drops the temperature of the soil surface and lowers evaporation. The plants return the favour by keeping the panels cool. This cooling is beneficial because Solar PV Panels begin to lose their efficiency at high temperatures gradually. The presence of vegetation keeps the region cool and helps Solar Panels operate efficiently. In turn, the coverage provided by the latter to the former not only cools them during daytime but also helps retain heat during the night. This is beneficial for plants, especially those in extreme regions. Deserts experience dual temperature extremities - days are sweltering, and nights are freezing. Such solar-agricultural integration, called Agrivoltaics, holds great promise for making arid areas agriculturally accessible because of this compound temperature and moisture maintenance. In effect, these would serve as self-temperature regulators.

Not only do many plants adapt to growing in shade, but a number of them actually afford more produce under shade than when fully exposed to sunlight. The aforementioned study experimented with three plant species, out of which two exhibited a profound increase in their Carbon-dioxide uptake as well as a tremendous increase in food production, compared to when they were fully illuminated. The third displayed a marginal decrease in these parameters, but still appreciably enhanced its water-efficiency. This disparity underscores the necessity of conducting long-term research consisting of coordinated, extensive trials of various plant species and varieties. Such studies should aim at documenting each one's response to shade and their subsequent evolution. Nonetheless, the current results are overall quite encouraging, to say the least.

It was earlier thought that solarisation of a piece of land renders it unfit for most forms of agriculture (spare maybe fungi-culture and the sorts). However, this recent discovery has flung open new avenues of possibilities that mandate considerate and extensive trial and investigation of the shade-growth properties of various crops. In fact, agrivoltaics could very well form the basis of sustainable, independent, free communities and even households. These would not be quite distant from the quasi-utopian "tech ecovillages" that socialists have frequently dreamt of. It would reduce constant dependency on both governments and corporations and help the individual and the community proclaim "energy-sovereignty". This would be a giant stride towards achieving economic independence. By affording a means to gain self-reliance and self-accountability, it would also help in curtailing the discrimination, blame-game, and scapegoating that the impoverished and the marginalised sections of the society are subjected to. Corporations, Governments, and the affluent put the onus of energy consumption and ecological footprint on individual usage, population growth, and supply of energy to unsanctioned settlements via so-called illicit transmission routes. Such attributions outright neglect the disproportionate energy consumption by industries and private freight and transport. On the downside, agrivoltaics would still link energy availability to land or property availability, continuing if not reinforcing the existent neo-feudalistic social organisation.

Agrivoltaics has shown to be particularly effective with root vegetables and leafy greens. Hence the technology could, in the future, help diversify agriculture, whereby these would serve as a reliable secondary source of income and a safeguard against primary crop failure in select areas. Although such pervasive levels of solarisation as envisioned here are still a distant ideal, Kitchen gardening and Backyard-gardening can readily and immediately benefit from these developments. The former could prove a nifty way to ease the burden in towering metropolitan apartment blocks.

Integrating crops and solar panels can help turn farms into self-sufficient, resource-wise independent entities. Agrivoltaic technology can drastically cut the ecological footprint of farming, especially in the United States and Australia, as well as significantly improve living standards in rural South-East Asia, South America, and Africa. They can also be integrated with drip irrigation and rainwater harvesting, or even hydroponics - growing plants in a nutrient-rich aqueous medium. Solar Panels are already being put to use over water reservoirs to prevent evaporation and avail its cooling. In fact, with squat crops such as certain creepers and root vegetables, limited aeroponics - stacked, root-drip watered rack agriculture could also be sustained under the shade of the panels. However, such installation is mostly public-venture and is often limited to being an experimental novelty. On the other hand, Agrivoltaics can be scaled right from individual households having rooftop or yard gardens to large farms and plantations.

Implementing Agrivoltaics in arid and semi-arid areas will not only check desertification but also help us to reclaim land lost to it. The sub-panel vegetation will cool and retain moisture. It should keep the soil from eroding and also offer a degree of shielding from airborne dust. The panels would also serve to hinder wind erosion to an extent and disrupt the flow of precipitation, considerably ameliorating water-borne erosion as well. Hailstorms are often quite destructive to crops, and solar panels could serve to block hailstones out too, although the damage they might themselves sustain needs study. All in all, the plant-solar panel system restricts the flow of erosive forces, conserves water, and moderates itself, keeping the ambience of its parts in check.

Rooftop Agrivoltaics can help urban units become sustainable and alleviate their energy footprint. Tropical areas can avail a trio of benefits with rooftop installations: High solar insolation translates to higher power output while the vegetation would prevent overheating to decay. A wider variety of plants are available to choose from owing to both the natural diversity of tropical areas as well as the ability to grow temperate crops in the cool shade. Thirdly, the coverage would also shield the house from heat in summers, moderating the temperature of the space underneath it.

Agrivoltaics can be upgraded using automation. It would require a sizeable one-time investment but would render the owner carefree, and guarantee peak performance. IoT systems equipped with Machine Learning can be used to optimise the available area and sunlight. Mounting the panels on movable frames permits them to be rotated, tilted, and adjusted according to the Sun's motion as best to reconcile the needs of the plant and the panel, and maximise either's output according to the user's needs.

Agrivoltaics could be our best shot at making our living non-intrusive upon nature, as well as in extracting the most out of our habitation spaces, without wastage. Agrivoltaics can empower us to achieve both sustainability as well as all-round self-reliance. It can enable us to make the most out of nature's plentiful bounties and would provide us with something invaluable- independence.

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