One of the primary deterrents to the intensification of agriculture has long been its requirement of insolation. Land put to agricultural use could not be simultaneously devoted to any kind of vertical development, given the dependence of photosynthesis – the Earth’s most abundant chemical reaction, upon sunlight.
Another sector faces the same problem – Solar Energy. Devotion of land area is a major concern. Although unlike plants, solar panels constantly evolve to become more efficient, the progress rate does not seem fast enough to realise sea-change within our generation’s lifetime. Provision of an unobstructed surface to intercept the sunlight is the primary consideration.
However, combining the two is not a bad idea, as recent research has shown. Aeroponics, the vertical stacking of small plants on racks equipped with root drip sprayers, to save water and land use, is already exploiting the ability of several plant species, particularly vegetables to thrive under shade or indirect and spare illumination. Initially, the cool shade provided by Solar Panels was deemed to be appropriate only for fungiculture. Shade is conducive to various kinds of plants, and studies are still ongoing. It’s a precarious territory and some varieties don’t even struggle to cope with shade, it is conducive to them, eliciting higher CO2 uptake.
A research study led by the University of Arizona’s Greg Barron-Gafford, published in Nature sustainability in September 2019, found out that shading by Photovoltaic panels provides multiple additive and synergistic benefits. These included, amongst others, greater food production, a reduction in the plant drought stress, and a drop in the solar panel heat stress. The entire research exercise involved rigorous monitoring of various internal and ambient parameters – microclimatic conditions, panel temperature, water uptake, soil moisture, plant ecophysiological function, and phytobiomass production. The researchers foresee a steep rise in its already immense utility in the near future, in light of predicted climate phenomena as persistent warming, acute heat waves, and precarious droughts.
The shade provided by the panels lowers soil surface temperature and evaporation, and the vegetation would reciprocate by keeping the panels cool. Solar PV Panels begin to wane in efficiency at high temperatures, hence the vegetation presence is conducive to their yield. Coverage by the panels not only provides cooling during daytime but helps retain considerable heat in the night. Of the three types of plants experimented upon, two showed a high increase in CO2 uptake as well as an immense rise in food production. Meanwhile, the third plant showed marginal decreases therein, but nonetheless considerably improved its water-efficiency. This implies that extensive trials to probe what crop plants prefer shade, or a meticulous investigation into the underlying mechanisms affording the changes is appropriated to fruitfully implement the scheme. However, overall, the results were extremely promising.
Such spatially integrated arrangements of certain crops and Solar Photovoltaic installations, also known as “Agrivoltaics” can turn farmlands into self-reliant entities, alleviate carbon and water footprints, and vastly improve rural living standards in the third world. Combining this innovation with drip irrigation would further enhance its water-efficiency.
Agrivoltaic installations in arid and semi-arid regions has the potential to check desertification. Plants not only serve to cool and retain moisture but also act as a shield against soil erosion and airborne dust, the latter of which poses a serious detriment to the efficiency of Solar Panels. Moreover, the panels would also hinder wind erosion and by breaking the flow of precipitation, water erosion as well. In fact, agrivoltaics may help recover certain tracts of land which were rendered unfit for cultivation. Rooftop agrivoltaics can also help urban infrastructure become sustainable, and households and homesteads to conveniently negate their carbon and energy footprint. In tropical areas, the benefits are three-pronged – high insolation would lead to higher energy yields further boosted by the overheating the plants prevent, a great diversity of plants can be grown, and the entire setup by simple virtue of its roof coverage would afford heat-shielding in Summers. In arid areas, the entire setup can be integrated with a rainwater harvesting system, and the roof cover would offer significant temperature moderation – cooler days and warmer nights.
The best part is that such installations can be automated – it is more of a one-time investment. An IoT-enabled network comprising of sensors and simple robotic actuators viz. temperature and moisture sensors, simple repetitive panel cleaners, and timed watering mechanisms can render the installations near-completely independent of human intervention, even for household units. For large installations, agro-business or otherwise, Machine Learning can enable extensive automation, adaptive optimisation and yield maximisation – say by tilting and turning the panels to tune in to the motion of the Sun or reconcile or readjust the plant’s and the panel’s needs according to the immediate requirement. Constant monitoring and foresighted planning can enable the satiation of both short-term and long-term goals.
Agrivoltaics might just be the redemptive cooperation that would salvage humanity from the ill-thought pursuit of indiscriminate competition. This adaptable, integral solution has the potential to not only make economic pursuits sustainable in general but also help achieve individual self-sufficiency and energy independence.
By Pitamber Kaushik, columnist, journalist, writer and researcher.
Featured image credit: Chelsea on Unsplash