Agrivoltaics: Synergistic solar-sharing provides a dual harvest of food and green energy
The combination of solar PV panels with farming systems, known as agrivoltaics, can help resolve the conflicting land use between food and energy in a way that is sustainable, profitable, and ultimately beneficial to players across the board. inspiratia's guest contributor Mary Condon delves into the benefits of deploying agrovoltaic systems in the market for crops, animals, farmers, and solar PV farms.
An impediment to the continued expansion of electricity production from solar photovoltaics (PV) will be a sizable amount of space required to capture sufficient solar irradiation. Often, land suitable for solar PV farms is also land that is or could be used in agricultural production, creating tension between food and solar energy farms.
While integrated rooftop solar PV has blossomed, ground-mounted PV systems are still, in many cases, in direct competition with agricultural land - a precious and limited resource. The continued expansion of solar farms on arable land could threaten food security within its current precarious context, where climatic changes, conflict, and loss of biodiversity are already challenging the stability and resilience of our food systems. Competing and conflicting land use between food and energy highlights the importance of finding a strategic and well-planned balance of crop, livestock, and energy production.
The solution: Dual-use systems
Agrivoltaics (agri-PV), the intentional combination of solar PV panels with crop and/or animal farming systems, can help mitigate this conflict by enabling food production and electricity generation on the same land. This dual land-use design not only increases land productivity and PV panel efficiency but has been shown to increase the resilience of certain crop and livestock production systems. With intentional site selection and holistic planning, agri-PV systems (also known as "agrophotovoltaics", "agrovoltaics", "solar sharing", and "APV") can produce multiple synergies between food and solar energy production systems.
Key issue: Land-use efficiency
As the efficiency of solar PV modules increases, less surface area is required to generate a given quantity of power. According to data from the International Renewable Energy Agency (IRENA), the amount of land required by PV projects to produce each megawatt (MW) of energy declined by 62% between 2010 and 2021, from 2.69 ha/MW to 1.94 ha/MW. However, even utilising the most efficient PV modules, agri-PV projects tend to require more land to produce the same amount of electricity due to the necessary spacing between solar arrays for farm equipment and sunlight to pass through. Therefore, with agri-PV systems, other important indicators should be considered to evaluate land-use efficiency and the benefits of colocation.
One such parameter is the land equivalent ratio (LER), originally derived for agroforestry systems, which can highlight when the combination of two systems – here, food and energy – provides a higher total output, indicating advantages to the combined production system. As an example, consider the combination of two hectares (ha) of land: 1 ha of crops and 1 ha of solar panels. Each considered individually, production from these monocultural farms corresponds to 100% crops and 100% solar energy. However, the use of agri-PV design on both hectares of land could correspond to production levels of 160% cultivation and 160% energy, that is, 80% of crop and 80% of solar energy on each hectare of land.
In practice, researchers have cited LERs of 135% and 173% in agri-PV systems with Durham wheat, while others have cited LERs of 110% and 150% with lettuce crops comparing fixed and dynamic PV mounts. Indeed, various studies have shown that well-planned agri-PV systems offer higher LERs than either monocultural system (indicated as > 100%), benefiting crops, animals, farmers, and energy companies.
Benefits: For crops
While not all farming systems can be successfully combined with solar, studies have shown that certain crop species, especially those in arid and/or humid climates, fare better under the protective shade of solar panels. While plants do need sunlight for photosynthesis, most solar energy occurs at unsuitable wavelengths for this process, and thus, only 1-2% is captured by plants. Furthermore, plants can reach the point of light saturation where they can no longer convert solar energy into chemical energy, as well as a point of photoinhibition – past which the sunlight becomes harmful to the plant.
Shade provided by solar panels in agri-PV systems reduces the levels of direct solar irradiation reaching the plant, protecting crops from harmful levels of light and heat. As a result, the plants tend to use less water and show reduced evapotranspiration, as well as lower mean soil temperatures around their roots and better soil water balance, on average providing more favourable conditions for plant growth than in full light.
In a 2018 simulation study covering maise production under a patented agrivoltaic solar tracking system named Agrovoltaico, in rain-fed conditions, average grain yield was higher and more stable under the PV panels than under full-light. Furthermore, the advantage of growing maise in the shade increased proportionally to drought stress, indicating that agri-PV systems such as Agrovoltaico could increase crop resilience to climate change.
Benefits: For animals
Just as certain crops fare better grown alongside or underneath solar panels, so too do certain animals raised within agri-PV systems. A 2023 study showed that Holstein heifers benefitted from a 40% reduction in radiant heat load due to the shade of solar panels facilitating lower body surface temperature, skin temperature, and respiratory rate in the shade compared to when they were exposed to the sun. The study concluded that agri-PV systems, in addition to producing electricity, can have significant potential benefits in providing better thermal comfort to cattle, as well as offsetting their enteric methane emissions released into the environment by means of the renewable energy produced on the same land.
Agri-PV systems can further increase animal well-being through habitat expansion, especially for pollinators. Apivoltaics (bee-keeping and solar PV) have been shown to be a promising pair. Both the expansion of solar farms and mono-agricultural land have contributed to diminishing habitat for wild and managed pollinator populations. Pollinators provide invaluable ecosystem services directly related to food production and food security. Agri-PV systems combining forage species for ruminants like sheep with clover and/or wildflowers for pollinators can further increase their LERs and contribute to multiple food and energy objectives at once.
An impressive example of apivoltaics can be found at the 100MW / 200 Ha Edensa Solar Apiary in Carmona, Spain. The project combines 3 hectares of aromatic plants (sage, rosemary, oregano, and coriander) with 30 hives within the PV installation. Beekeeping promotes the improvement of crop productivity by increasing the degree of pollination while the project as a whole fosters symbiotic relationships for crops, pollinators, and energy on the same land.
Benefits: For solar PV farms
Solar PV modules themselves benefit from the integration of agricultural practices as well. While solar panels inherently need solar radiation to produce electricity, excess heat can diminish the efficiency of the solar modules. In a recent 2023 study, researchers developed a numerical model to investigate the microclimate of a solar farm. They used their model to compare an agri-PV system to a traditional PV. The researchers noted that as modules experience efficiency losses between 0.1% and 0.5% per degree above 77°C, the implication is that solar conversion efficiency is greater when solar is mounted above crops that provide a cooling effect compared to exposed soil or gravel. Their results indicate a cooling benefit of up to 10°C in agri-PV systems.
In addition to efficiency improvements, researchers in this study believe that years of reduced operating temperatures could lead to improved solar module lifespan, which further speaks to the long-term economic potential of agri-PV systems. From a financial perspective, solar PV farms benefit from the synergies of agriculture through improved efficiency, as mentioned, as well as decreased maintenance costs associated with cleaning PV panels and mowing or spraying between arrays.
Benefits: For farmers
Not least are the potential benefits for farmers using agri-PV systems, many of which have been noted in the studies thus far. In many cases, water efficiency improves, having huge implications for farmers in traditionally water-stressed regions or those facing more frequent and/or severe droughts due to climate change. Many systems show improved crop yields as well, although some crops fare better than others under agri-PV shade. Farmers can increase pollinator services for their crops if they choose to expand further into apivoltaics.
The direct production of solar energy on farmland can facilitate the adoption of intelligent irrigation systems, also known as 'precision agriculture' or 'agriculture 4.0'. Electricity produced from the PV system can be used directly on-site to run high-pressure irrigation systems, further strengthening the resilience of farming operations. Furthermore, the steel construction of the PV mounting systems and the panels themselves are significantly more durable than traditional plastic used for rain and hail cover. The more robust design lends to lower maintenance costs for farmers, as they need not be replaced frequently as with traditional plastic coverings.
From a financial perspective, agri-PV systems can provide resilience to farmers in the face of climate change, where high temperatures, water scarcity, floods, pests, and disease threaten to decimate crop production in any given year. Agri-PV systems can provide multiple sources of income for farmers, and this diversification adds to resilience, allowing farmers to continue and even expand their farming operations. In total, it has been found that the combined crop and energy output from an agri-PV system can enhance land productivity by up to 70%.
Benefits: For society
The increased pervasiveness of electricity in agriculture through the application of agrivoltaic design can help reshape the market and incentivise greater production and usage of electric tractors and other farm equipment, further electrifying our world. Agri-PV farms located in rural areas can help enhance connectivity for electric vehicles (EVs) by providing EV charging stations between larger urban centres. In a development context for rural and/or remote settings, electricity produced on agri-PV farms might help replace diesel generators in areas not yet connected to the grid, further cutting down on our GHG emissions. Additionally, the adoption of this dual-use design can contribute to the digital agriculture transition that many large development organisations promote. It could even be beneficial in slowing detrimental trends of youth migration into urban centres.
Land-use and land-use change have their own implications for GHG emissions. Converting agricultural land into traditional PV solar farms without the use of agri-PV has direct and indirect effects on climate change. Food production may need to expand in other areas of the world, possibly encroaching on biodiverse land and habitats, increasing the likelihood of zoonotic diseases jumping into food production systems - especially animal-based systems. In many ways, agri-PV shows promising benefits for society across energy and food systems alike.
To stay on track with the Net Zero Emissions by 2050 Scenario, solar PV projects will continue expanding. The mitigation pathways we choose to employ, however, must be compatible with sustainable, long-term goals. With agri-PV designs, we can indeed continue to expand and capitalise on solar resources without increasing the difficulty of feeding our growing population in sustainable and equitable ways. Agri-PV can provide systemic agronomical, ecological, and financially sustainable solutions that minimise negative trade-offs and amplify synergies.
Carefully designed and implemented agrivoltaic systems have the potential to increase land-use efficiency and provide multiple benefits for stakeholders within each system. Crops, animals, and humans can benefit from reduced heat stress under the shade of panels. Pollinators benefit from increased habit. Solar PV panels benefit from increased efficiency with cooler microclimates and increased airflow. Farmers benefit from the diversification of income and lower maintenance costs. Food, water, land, and energy efficiencies can be enhanced through this dual-use design.