Guest Post by Taylor Bacon, 2022-2024 InTERFEWS Fellow, Ph.D. Student in the Department of Soil and Crop Sciences at Colorado State University
On a cool April morning I sat at the breakfast table of a picturesque bed & breakfast outside of a small town in southwestern Georgia. As our hostess set a plate of steaming biscuits and homemade peach preserves down on the table, she said something along the lines of “we’re sad to see so much of our beautiful farmland being turned into solar panel fields.” The panels in question were part of the nearly 200-megawatt solar photovoltaic (PV) power plant about ten minutes down the road from the bed & breakfast – and our research site for the next three years.
Our hostess’s concerns around solar power plants like this one are certainly not uncommon. The U.S. now has nearly 150 gigawatts of installed solar capacity covering roughly 1.5 million acres. The buildout of solar energy has increased dramatically over the last decade and is expected to only continue increasing with an estimated 10 million acres of solar needed to meet state & federal climate standards and renewable energy targets. These power plants are often located on leased farmland or ranchland – landowners get a monthly payout in exchange for giving up their agricultural productivity on that land for the duration of the project.
This tradeoff – agricultural productivity for energy generation – has created its fair share of contention. One of the greatest concerns raised with the buildout of solar energy is the land footprint required, and there’s often local resistance to new projects despite the economic force pushing them forward. Many rural communities like the one in Georgia are concerned about the loss of farmland and feel there aren’t any benefits from the appearance of new solar in their neighborhoods. However, for many rural agricultural producers, the guaranteed income from leasing land to a solar developer is nearly impossible to turn down.
But maybe this tradeoff is avoidable. The presence of solar panels on the American landscape seems somewhat inevitable, but there is opportunity in the way in which solar power plants are planned, designed, built, and managed. Over the last decade, budding research has addressed the potential to both produce food and clean electricity from the same piece of land. This co-location of agriculture and solar photovoltaic energy generation, often coined ‘agrivoltaics’, has the potential to alleviate some of the tension between the solar industry and agriculture. However, our understanding of these dual land use systems is still nascent and many questions remain.
Articulating these questions is an important first step in designing the research projects to tackle answering them. Here I do my best to outline some of the major questions I’ve run into as I’ve explored this rapidly growing field:
- How do solar panels affect the ecosystems where they’re installed?
When you see a field of solar panels from the highway, it’s easy to think of the installation as a homogenous, inanimate, mechanical entity. Walking between rows of panels, however, the reality of the system as a highly heterogeneous, dynamic ecosystem comes to life. In many solar power plants, some vegetation is retained, which helps to cool the panels, keeping them more efficient in their energy capture. Compared to a piece of land without solar panels, the panels introduce spatial variation into the landscape, redistributing water and redirecting sunlight. The areas directly beneath the panels see a reduction in both sunlight and water, while land at the edges of the panels may see more water that drips off the panel edge paired with intermittent shading over the course of the day. These influences on the microclimate beneath the panels change how plants grow and how carbon flows through the ecosystem. In some cases, there may be benefits from these changes (like increased water use efficiency), while in other cases there might be unintended consequences (like reduced productivity). The impact of solar panels on the ecosystem will have different effects in different climates and on different types of plants and soils. Understanding these new dynamics across a range of climates and ecosystems is central to understanding how solar PV can be incorporated with other land uses.
- How can different agricultural systems be integrated with solar PV? What works well? What doesn’t?
Agriculture is incredibly broad and can include everything from raising bees to growing corn to grazing cattle. Different agricultural production systems will be impacted differently by the co-location with solar PV. For example, the additional shade from the panels may benefit some crops while hindering others. In addition to altering the amount of sunlight plants receive, the panels also alter the time of day at which plants receive direct sunlight. Plants on the eastern edge of a row of panels that track the sun will be shaded in the morning but get direct sun in the afternoon, often during the heat of the day. Different plants will respond to these variable conditions in different ways, and some agricultural products will be more sensitive to these changes. For example, grazing livestock around panels may have more resilience to changes in plant productivity caused by the panels than certain crops. Understanding these specific interactions in different agricultural systems will be key to the successful deployment of agrivoltaic systems.
On top of the question of how different forms of agriculture can be integrated with solar PV, there are questions about what land is available for systems like this and what land is well-suited for these systems. This will be critical to understanding what forms of these systems can be deployed at large scales.
- How can solar PV design & construction be optimized for agriculture & ecosystem benefits?
Both the physical design and installation of the solar PV system have dramatic impacts on the potential for agrivoltaic systems. Through modifications in spacing between rows of panels, panel transparency, and panel height, there is opportunity to tailor the physical infrastructure to specific agricultural demands. For example, taller panels have the potential to allow for grazing of larger animals but will cost more in building materials. Wider rows between panels could accommodate farm equipment for row crops, but will reduce the energy generation per land area. Understanding the economic, environmental, and agricultural tradeoffs of these choices is critical to making informed choices and ultimately designing successful agrivoltaic systems. Developing both ecological and financial models that can simulate different design options and compare tradeoffs will be an essential focus of agrivoltaics research.
- How do the life-cycle climate, energy, and water impacts of an agrivoltaics system compare to agriculture-only or solar-only alternatives?
While agrivoltaic systems seem to offer environmental and economic benefits through increased land use efficiency, it’s important to develop a holistic understanding of these systems. The layering of multiple land uses is anticipated to alter the greenhouse gas and water footprints of the energy and food production compared to standalone agriculture or solar. Understanding the direction and magnitude of these changes is key to making informed decisions around the best use of land from a climate and environmental perspective. Thinking about the big picture life-cycle tradeoffs of dual-land use system also raises questions around the end-of-life. Most solar arrays have a lifetime of 20-30 years, and solar is new enough that we haven’t fully experienced what the end-of-life of solar power plants looks like on a large scale. Important questions remain around how retirement of an agrivoltaics system compares to a traditional solar PV system, including potential disruption to agricultural practices during decommissioning and impacts to the landowner and community.
- How do agrivoltaic systems impact the surrounding communities? How do these impacts and outcomes compare to single-use systems?
Our conversations over the breakfast table made clear that there is much more to the impact of solar PV and agrivoltaics than just the environmental outcomes we are measuring. The identity and economy of the rural areas often selected for large solar power plants are deeply tied to the land, and dramatic changes in land use – like the installation of hundreds or even thousands of acres of solar panels – can cause major ripples throughout the community. While there has been some research on community response to large-scale solar energy, agrivoltaics-specific research in this area is limited. Preliminary research suggests that integrating agriculture into the development of a solar project can increase community support but additional research on the human dimension of agrivoltaics – from solar developers to farmers to local community – is crucial to the intentional development of these systems.
Agrivoltaics research across the world is tackling these five questions and many others to better understand the potential of these novel systems. There are research projects studying high-value fruit and vegetable crop production under solar panels in water-limited environments, the potential for row crop production under panels, and ecosystem services like pollinator habitat, all with the goal of better characterizing the integration of agriculture and solar energy.
Our project in Georgia is studying the potential for pairing regenerative cattle grazing with solar PV, where we aim to both design the infrastructure to facilitate this dual land use as well as understand how the integration of panels & grazing affects ecosystem services including soil carbon sequestration. This project brings together ranchers, solar developers, ecologists, modelers, animal scientists, and energy experts to tackle these questions.
I spent two weeks at our field site this spring collecting soil samples, carefully clipping vegetation, and installing soil and weather sensors. I walked away with an appreciation of the vibrance and complexity of these dual land use systems, as well as a better understanding of the people and communities who support them. There’s no doubt that we are amid a major – and necessary – energy transition that will impact people and ecosystems across the country and across the world, from the coal communities of Appalachia to the lithium mines of Chile. We still have influence over what this energy transition looks like for the ecosystems and people that are impacted. Agrivoltaics offers one tool for guiding this energy transition towards both environmental and ecological sustainability but the questions above show just how much we still need to learn.