In 2015 the United Nations Member States adopted the 2030 Agenda for Sustainable Development, setting 17 transformative goals and targets. Three-dimensional approach built on economic, social, and environmental principles should guide us towards a more sustainable future, serving as a beacon of light on our embarked journey (UN, 2015). The world free of hunger, fear, and violence, with equitable access to education and health care, safe for all its inhabitants, resilient, and sustainable. Sounds like utopia, isn’t it?! But how do we get there? In a world where the population is growing at an unprecedented rate, how can we make sure we can reach all of the Sustainable Development Goals (SDG)?
Take renewable energy for one. Honouring the commitment to provide universal access to affordable clean energy, the world advances towards a sustainable energy target with renewable sources covering about 30% of the world’s energy consumption (UN DESA, 2023). Among different types of renewable energy solar power is the third largest renewable electricity technology, coming after hydropower and wind. In 2022 generation of solar energy increased up to 26%, reaching almost 1 300 TWh (IEA, 2023). This is the largest generation growth of all renewable technologies in 2022 and it accounts for 4.5% of total global electricity generation (IEA, 2023). It comes as no surprise. Solar energy is a ubiquitous, economically competitive, and one of the cleanest forms of energy that has no harmful by-products nor does it emit any greenhouse gases. In 2022 investment in solar PV comprised almost 45% of total global electricity production, which is almost 3 times more than on all fossil fuel technologies collectively (IEA, 2023). And there is no sign of slowing down.
However, this transition comes at a cost. Installation of solar parks can have a tremendous impact on agricultural landscapes and rural communities as in densely populated countries they are often installed on land suitable for agriculture or forestry (Goldberg et al., 2023; Marshall-Chalmers, 2023). Once the land is used for PV modules the prime farm soils are lost for agriculture for the next 20 - 25 years. As the demand for food resources is growing with the increasing population, which is forecasted to reach more than 8.1 billion people by the end of 2023 (UNPF, 2023), competition between the agricultural sector and renewable solar energy becomes more fierce. But what if there was a way to achieve both? Can you transition to a more sustainable green energy source without compromising your ability to grow crops?
The agrophotovoltaic (APV) or agrivoltaic systems represent a symbiotic approach of dual land use, where the generation of PV electricity is combined with food production. The idea is not new. Professor Adolf Goetzberger, founder of Fraunhofer ISE, and Dr. Armin Zastrow introduced the concept of APV for the first time back in 1982. In their article “Kartoffeln unter dem Kollektor” (potatoes under the collector), which appeared in the “Sonnenenergie” journal, they talked about how raising the PV modules 2 meters above the ground frees space underneath for agricultural purposes (Goetzberger, Zastrow, 1982). It took 30 more years for this idea to take root. In 2004 one of the first stilt-mounted AV was invented in Japan followed by rapid development of small-scale AV in the country (Nagashima, 2005; Sekiyama and Nagashima, 2019). Starting from 2010 and onward AV plants were installed in many European countries France, Italy, and Germany, in Asia, Australia, and the United States (Wydra et al., 2023). Today AV plants are operational in countries such as Argentina, Austria, Belgium, Chile, Czech Republic, Denmark, Greece, India, Israel, Netherlands, New Zealand, Pakistan, South Africa, South Korea, Spain, Sweden, Switzerland, Taiwan, Turkey, and UK (Wydra et al., 2023). Overall AV capacity is estimated to be at least 14 GWp in 2022 (Ferris, 2022). In order to keep up with the decarbonisation pathways outlined in the European Green Deal the amount of AV plants worldwide is predicted to increase even more in the future.
Over the past decade, the technology rapidly developed, offering flexible design of the PV modules. The height of the ground-mounted solar modules can vary between three to five meters above the field, freeing space to accommodate heavy machinery to work the land underneath the agrivoltaic system. Distance between PV modules, orientation, and angles of the panels could be tailored to the specific needs of the crop, planted below, to ensure sufficient irradiation and precipitation. Single or double-axis customized tracking (CT) for the mobile AV allows tracking solar radiation changes throughout the day. Manual adjustment of the axis position will help maximize economic performance and optimal light management improving not only efficiency but also crop protection against all elements (Wydra et al., 2023; Vandest, Hemetsberger, 2021). Light tracking could also be adjusted to the specific demand of the crop, allowing seasonal control of the modules (Hörnle et al., 2021).
Until recently, countries mostly employed conventional opaque photovoltaic (PV) modules that can cause up to 40 % reduction in solar radiation depending on the density and orientation of PV modules (Gomez-Casanovas et al., 2023). Although some initial field studies showed that this so-called “shading effect” can negatively affect crop productivity resulting in reduced yields (Fraunhofer Institute for Solar Energy Systems ISE, 2022), more and more evidence suggests the opposite for some crop types (Gomez-Casanovas et al., 2023). Field studies based on corn and some varieties of lettuce showed that their productivity is not only comparable to conventional agriculture but also increased (Edouard et al., 2023; Marrou et al., 2013; Sekiyama and Nagashima, 2019). New novel panel designs that emerged in recent years also help mitigate the shading effect (Gorjian et al., 2021; Zhang et al., 2021).
Overall, acquired agricultural practices and field studies carried out over the past decade showed that potentially any type of crop could be cultivated under the AV. To alleviate the effect of reduced irradiation due to the shading effect created by the modules more shade tolerant crops are preferable for AV systems. These can include leafy vegetable species, grass, various stone fruit and berry species, and other specialized crops (e.g. wild garlic, asparagus, hops) (Fraunhofer Institute for Solar Energy Systems ISE, 2022). Relatively sensitive crops like viticulture are most likely to gain additional benefits from overhead AV structures. Intensifying solar radiation puts additional strain on the crops that suffer from sunburn and water shortages (Losh, 2023). PV modules not only provide protection from excessive solar heat but also shield the crops from extreme weather events like strong wind, rain, and hail (Fraunhofer Institute for Solar Energy Systems ISE, 2022). Moreover, these panels help curtail soil moisture loss by reducing evaporation rates (Gomez-Casanovas et al., 2023). Even though AV panels may pose constraints on the productivity of some crops, in the future these crops are more likely to be more resilient to extreme heat waves or droughts, compared with plants grown in conventional agricultural systems. Further studies showed that letting your livestock graze under the AV systems can have similar benefits. Shade provided by PV modules decreases heat stress and water consumption in domestic animals (Andrew et al., 2021; Maia et al., 2020; Sharpe et al., 2021).
But not only PV modules can benefit the crops. Crops themselves create a microclimate below the modules that helps regulate the temperature of the soil, resulting in more efficient cooling of the modules and an increase in power generation efficiency of up to 3% (Barron-Gafford et al., 2019).
More studies are looking now into the further potential positive effects of the AV modules on the ecosystem level. Incorporation of nectar-producing plants (flowers) under the solar arrays showed to increase insect diversity important for crop pollination and crop yields (Graham et al., 2021; Levenson et al., 2022). Integration of native species into the AV-habitat systems will help conserve biodiversity and restore important ecosystem services like carbon sequestration or soil health (Walston et al., 2022).
However, AV installation still faces many challenges. One of the main ones is the significant upfront investment costs for its installation and the prospect of the long-term commitment. Integration of the appropriate crop rotation design can alleviate some of these costs, minimizing the payback period by up to 35 % (Roy and Ghosh, 2017). The combination of animal husbandry with agriculture will further reduce the financial burden providing additional revenue (Lytle et al., 2020). There are potential prospects to use the by-products of the agricultural crops aka waste from processing raw materials and animal manure for biogas production that can further be used to produce heat or electricity (Temiz et al., 2022).
Although agrivoltaic parks can have positive effects on the socioeconomic status of the communities, providing jobs, training opportunities, and additional sources of income, public perception is still a burning issue. The bad reputation of the solar industry raises concerns among local stakeholders (Margolis and Zuboy, 2006). Fears that AV will interfere with agricultural production and future farming practices are rooted in its high complexity and uncertainties regarding the operation and business plan (Torma and Aschemann-Witzel, 2023). In this context, future adaptation of AV practices by local farmers will rely on appropriate governmental support through public policy mechanisms as well as the involvement of the local stakeholders in the decision-making process.
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Dr. Alexandra Filippova
Dr. Filippova is a marine geochemist with an extensive and diverse scientific background in geoscience, natural management, polar marine research and climate science. Over a decade she studied processes that affect ocean circulation in the past and how they could compare to the modern day situation. One of the key questions of her studies included the role of climate induced melt water inputs in ocean circulation and climate changes on short and long term scale. Beyond academia, she truly enjoys volunteering with Non-Profit Organizations, where she advocates for diversity and inclusion of caregivers in all STEMM fields (Mothers in Science) and works on development of sustainable projects that aim at preserving nature and biodiversity (Viable Community).