How “Agrivoltaics” Can Provide More Benefits Than Agriculture And Solar Photovoltaics Separately

Energy Innovation partners with the independent nonprofit Aspen Global Change Institute (AGCI) to provide climate and energy research updates, and a full list of AGCI’s quarterly research updates covering recent climate change research on clean energy pathways is available online at https://www.agci.org/solutions/quarterly-research-reviews

Solar photovoltaic (PV) technology is pivotal in the transition to a low-carbon energy system. Yet wide-scale deployment may be hindered due to fears about sustainability tradeoffs and pockets of social resistance. For instance, deployment of PV farms can compete with agriculture for the use of the same land for food production and may create local tensions about how land is used and allocated.

However, an emerging strategy known as agrivoltaics combines solar electricity generation with agricultural production in the same location. As shown in Figure 1, more and more research is evaluating agrivoltaics for its potential to enhance land-use efficiency, climate solutions, sustainable food, and local economies. Different agrivoltaic configurations—such as combining PV with croplands, pastures, or pollinator habitats—may contribute to achieving sustainable energy and food goals simultaneously, while possibly reducing local opposition to PV deployment. This article reviews a few recent studies that uncover what researchers are finding about the myriad potential benefits of agrivoltaics.

Agrivoltaic systems are shown to increase crop production, among other benefits, in drylands

A study by Barron-Gafford and colleagues compared the food, energy, and water implications of an agrivoltaic system to a traditional agriculture system in Arizona. Across the plants examined (chiltepin pepper, jalapeño, and cherry tomato), fruit production doubled in the agrivoltaic system relative to the traditional environment. Due to the cooling effect of plant transpiration on the solar panels (Figure 2), there were also marginal improvements to electricity production. The agrivoltaic PV system generated 1 percent more electricity on an annual basis (3 percent increase during summer months) compared to a regular PV system in the same location. Additionally, carbon dioxide uptake and water use efficiency were also both higher (both by 65 percent) in the agrivoltaic system, which the authors suggest aided overall productivity by reducing plant stress due to heat and drought.

Agrivoltaic systems can support economic development of rural communities in developing countries

A recent study conducted by Choi and collaborators sought to estimate the benefits of implementing agrivoltaics in rural communities in low- and middle-income countries. The authors selected Indonesia as a test case and applied a life cycle analysis approach to estimate the effects of different land-use scenarios on greenhouse gas emissions, income, and environmental co-benefits.

The model-based results showed that “small-scale agrivoltaic systems are economically viable in certain configurations and can potentially provide co-benefits including rural electrification, retrofitting diesel electricity generation, and providing electricity for local processing of agricultural products.” The authors also noted the barrier of high capital expenditures solar, which currently may be difficult to justify absent increases in subsidies for solar or reductions in subsidies for fossil fuels.

Pasture-based agricultural processes may also be improved through agrivoltaics

Relatively less research has explored how agrivoltaics could work in pasture settings. An April 2021 research article by Andrew and colleagues in Frontiers in Sustainable Food Systems conducted an experiment that monitored sheep grazing on both agrivoltaic and traditional pastures open over two years. Predictably, shady plots with solar panels generated less herbage than the sunnier, open pastures. However, lambs in both the traditional and agrivoltaic plots gained weight at nearly the same rate. The authors found reduced quantity in herbage due was made up for by higher quality forage in shady areas, possibly alongside reduced heat stress and more effective foraging behavior when sheep roamed among the PV panels. All told the comparable outcomes in lamb production between the two treatments indicate opportunities for improved land-use efficiency in an agrivoltaic pasture system.

A related study explored the opportunities of shifting conventional animal feeding operations and conventional PV farms to pasture-based arrangements that integrate PV. In Cleaner and Responsible Consumption, Pascaris and colleagues explored this potential using life cycle analysis on different scenarios of rabbit and electricity production (as shown in Figure 3). When comparing emissions from the energy utilized to mow grass in conventional PV farms and supply processed feed for conventional rabbit farms, the authors estimated substantial reductions in emissions by converting to an agrivoltaic configuration. In the agrigvoltaic scenario, rabbits fed on natural grass, eliminating the need for additional feedstock or mowing operations, resulting in sizable emissions reductions gains.

Agrivoltaic systems can restore pollinator habitat

Relative to PV with crops or PV with pasture, the most widely deployed form of dual-use PV in the United States to date is called “pollinator-friendly PV.” This type of agrivoltaic strategy installs solar arrays on top of pollinator habitat, which according to the National Renewable Energy Laboratory (NREL) is already utilized in more than 1 gigawatt of U.S. PV installations.  A field study by Graham and colleagues published earlier this year in Nature Scientific Reports compared the composition and behavior of foraging pollinators between fully and partially shaded plots under solar arrays and on full-sun (control) plots at the Eagle Point Solar Plant in southwestern Oregon (Figure 4). Although the fully shaded areas directly beneath the panels attracted far fewer pollinating insects, the researchers observed more types and greater numbers of insects in the partial-shade plots, relative to the full-sun plots, at certain times throughout the growing season. Although pollinators were observed to actually visit plants at comparable rates between each of the treatment areas, some plants in the partial shade plots bloomed later, which the authors suggested could benefit late-season pollinators.

Agrivoltaic systems may improve public support for solar PV development

In a May 2021 pre-print posted to SocArXiv (open archive of social science research not yet under peer-review), Pascaris and colleagues reported on a survey of nearly 200 respondents across in Lubbock County, TX and Houghton County, MI. Although most of these respondents already expressed favorable attitudes toward solar deployment (72 percent), a marginally higher percentage (81 percent) indicated they would be even more supportive of local solar installations if they were combined with agriculture production. Although the results signaled that agrivoltaic proposals could further reduce local opposition, they also tracked the considerations important to communities when deliberating over solar projects – namely, that proposed agrivoltaic projects need to take into account local concerns such as how the project would provide economic benefits to farmers, the fairness in how economic benefits are distributed, the details of the siting of any new installations, and the overall alignment with local interests.

Conclusion

What can we take away from these recent studies? At the very least, each showcases the ability for agrivoltaics to increase land-use efficiency without sacrificing much in the way of either energy or food production. Furthermore, many agrivoltaic configurations appear even to enhance both food and energy production while at the same time reducing the environmental impact from pursuing each activity as a standalone.

While this area of research is still advancing, findings from these particular studies can help to inform optimal designs and standards for emerging applications of agrivoltaics. To date, little support and guidance on best-practice implementation, let alone policy, exists to foster agrivoltaic deployment. Yet if current signals in research hold up, agrivoltaics may help low-carbon energy to become synergistic with, rather than competitive with, other sustainable development goals.

Featured Research

Toledo, C.; Scognamiglio, A. Agrivoltaic Systems Design and Assessment: A Critical Review, and a Descriptive Model towards a Sustainable Landscape Vision (Three-Dimensional Agrivoltaic Patterns). Sustainability 2021, 13, 6871. https://doi.org/10.3390/su13126871

Pascaris, A. S., Schelly, C., Rouleau, M., & Pearce, J. M. (2021, May 5). Do Agrivoltaics Improve Public Support for Solar Photovoltaic Development? Survey Says: Yes!. https://doi.org/10.31235/osf.io/efasx

Barron-Gafford, G.A., Pavao-Zuckerman, M.A., Minor, R.L. et al. Agrivoltaics provide mutual benefits across the food–energy–water nexus in drylands. Nat Sustain 2, 848–855 (2019). https://doi.org/10.1038/s41893-019-0364-5

Horowitz, Kelsey, Vignesh Ramasamy, Jordan Macknick and Robert Margolis. 2020. Capital Costs for Dual-Use Photovoltaic Installations: 2020 Benchmark for GroundMounted PV Systems with Pollinator-Friendly Vegetation, Grazing, and Crops. Golden, CO: National Renewable Energy Laboratory. NREL/TP-6A20-77811. https://www.nrel.gov/docs/fy21osti/77811.pdf.

Andrew AC, Higgins CW, Smallman MA, Graham M and Ates S (2021) Herbage Yield, Lamb Growth and Foraging Behavior in Agrivoltaic Production System. Front. Sustain. Food Syst. 5:659175. Doi: 10.3389/fsufs.2021.659175

Alexis S. Pascaris, Rob Handler, Chelsea Schelly, Joshua M. Pearce (2021) Life cycle assessment of pasture-based agrivoltaic systems: Emissions and energy use of integrated rabbit production. Cleaner and Responsible Consumption, Volume 3, 2021, 100030, ISSN 2666-7843, https://doi.org/10.1016/j.clrc.2021.100030.

Graham, M., Ates, S., Melathopoulos, A.P. et al. Partial shading by solar panels delays bloom, increases floral abundance during the late-season for pollinators in a dryland, agrivoltaic ecosystem. Sci Rep 11, 7452 (2021). https://doi.org/10.1038/s41598-021-86756-4

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Solar power plays an essential role in the clean energy transition, but its land-use requirements put it in direct competition with agriculture. New research on agrivoltaics demonstrates the benefits of combining both solar and agricultural production including increased productivity, water conservation, and local economic development, while also bolstering public support for clean energy.
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After The Megafires: What’s Left And What’s Next

Energy Innovation partners with the independent nonprofit Aspen Global Change Institute (AGCI) to provide climate and energy research updates. The research synopsis below comes from AGCI Program Director Emily Jack-Scott and a full list of AGCI’s quarterly research updates covering recent climate change research on clean energy pathways is available online at https://www.agci.org/solutions/quarterly-research-reviews

Something is clearly different about the wildfires roaring in the western United States. Over the last decade, we have increasingly used terms like “megafires” and “gigafires” (fires that burn more than a hundred thousand, and more than a million acres, respectively) to describe them. They’re staggering, not just in size, but also severity. Fire seasons are lasting longer, and lifelong firefighters are getting mentally and physically burned out.

We know fires have a long history in western montane ecosystems, but the fires of the last couple decades are a new beast. We’re seeing a perfect storm play out – the result of long-term fire suppression initiated by Euro-American colonists, climate change, and more people than ever building permanent dwellings in fire-prone forests (for more on wildfire attribution refer to our previous research review). We’re left with a new reality of increasingly frequent, more intense wildfires, greater loss of property and life, and a multitude of questions about what will be left when the megafires are out.

What kind of ecosystems will regenerate? How long will it take to see new growth? Will these continue to be landscapes humans and other animals can inhabit? For those of us living in the West – breathing thick smoke for weeks on end, watching neighbors and loved ones troop off for months to battle blazes – these questions are deeply personal and increasingly urgent.

The latest scientific research confirms that we must be prepared for a dramatically altered landscape in the coming decades. In 2020, Coop and colleagues published research illustrating how relatively small changes in fire behavior have widespread impacts, converting forests into non-forests over massive swaths of the West. As summarized by Coop, many researchers are forecasting fire-driven conversion of 30 to 50 percent of most western conifer-dominated forests into non-forested shrublands, grasslands or hardwood-dominated ecosystems before 2100 (Coop et al. 2020).

Historically, fire-adapted forests evolved to tolerate low- to moderate-severity fires. Because fires burned on regular intervals, forests were often more open, and understory plants were less likely to grow tall enough to serve as “ladder fuels” (serving as a ladder for fires on the ground story to climb up into the crowns of trees, escalating the fire intensity). Even if smaller younger trees perished in those fires, larger older trees could withstand the ground fires and provide a seed source for trees to regenerate amidst the grasses and shrubs that opportunistically sprout in the wake of fires.

But we’re seeing higher severity fires, in denser forests, over larger areas. As Hagmann and colleagues explore in depth in their 2021 paper, there is overwhelming evidence to confirm changing forest conditions and changing fire regimes. Fires now climb more easily up into the crowns of mature trees, and burn too hot for even thick-barked mature trees to withstand. And because our forests have lost their heterogeneity of ages and structures (see Figure 1), megafires are scorching more uniformly over broader swaths. So megafires are leaving behind tens, or even hundreds of thousands of acres scorched without enough seed trees to contribute to the usual succession of plant species that have historically regenerated after fires in the West.

Even when seed trees persist, soils can be so scorched that their life-giving nutrients actually volatilize into the atmosphere. Soil structure can be so altered that instead of absorbing water they actually repel it, rendering them far more prone to erosion. So even the most resilient of landscapes are left barren and dry after high severity fires. In these cases, it can take decades to rebuild even baseline conditions hospitable enough to support the natural succession of forests. And that’s assuming historical climatic conditions.

Climate change is creating hotter and drier conditions which further deter recovery. Seeds have a harder time germinating and growing to maturation, and fires are more frequent – sweeping through areas still in early recovery stages after the last severe burn.

These dynamics all culminate in what ecologists refer to as conversion – a transformation into a new ecological state, with new dominant species, usually filling different ecological functions. The conversion of a forest to a non-forest may happen as the result of a single large, high-severity fire, or it may happen as the result of post-fire conditions that make the burned area more likely to burn again before forest regeneration can occur (Figure 2).

When dense forests burn, they leave behind partially burned dead and dying trees for the next fire to re-burn in the same area. These secondary high-severity fires can actually burn hotter than the initial fire, killing off any seedlings or young trees and reinforcing conversion. This is especially true at the edges of forests, where trees are often already at the limits of tolerable growing conditions (Parks et al. 2019).

So what can be done? The scale of this challenge is massive, and outstrips current management techniques and budgets. But managers do still have the options to engage in strategic operations, especially in “high value” locations (such as in high-use recreation areas, timber stands, municipal watersheds, or near residential areas). It comes down to a choice between resisting, accepting, or directing conversion.

Coop and colleagues lay out a great framework to help inform that choice:

Use the modeling and mapping research available to assess the likelihood of fire-driven conversion in the area in question
Consider the ecological fallout of a disturbance in the area in the midst of a changing climate
Increase heterogeneity of forests at stand and landscape scales (through mechanical thinning, prescribed fires, allowing certain low- to moderate-intensity wildfires to burn, forestry operations, and strategic tree planting)
Incorporate social science into decision-making to aid managers in an increasingly difficult position to understand societal values and social acceptability of management choices, especially novel approaches that direct conversion

Hessburg and colleagues echoed many of these recommendations in a 2021 paper. They acknowledge the understandable societal resistance to large-scale management techniques – the result of broken trust as a result of extensive logging of old growth forests in the 1900s. But they make the case for intentional and proactive management of western forests in the form of prescribed fires, managed wildfires, and silvicultural treatments.

They argue it is critical to cut through the politicization of forestry management approaches, in order for western forests to better adapt to climate change and high-severity wildfires. They advocate for application of best available science (including Indigenous and western knowledges) in designing intentional management strategies, even though there will be unavoidable uncertainty in that science. On this point, they lean into a discussion about not having the precautionary principle unnecessarily translate into inaction.

Under the precautionary principle, a decision-maker must demonstrate in the face of uncertainty that the most likely outcome is one of no harm. But given the inherent uncertainties at the convergence of changing climate and changing fire regimes, they caution against basing decisions about forest management solely on that principle. This can lead managers to assume a course of non-action, deferring to natural processes alone. Rather, they lay out a series of questions to inform decision-making under uncertainty:

“What are the uncertainties, trade-offs, and likely consequences to U.S., Canadian, and Mexican Indigenous and nonindigenous people, infrastructure, ecosystems, native species and habitats of
1) Restoring active fire regimes to dry, moist, and cold forest ecosystems,
2) Continued fire suppression in these same forest types,
3) Proposed proactive, reactive, and no-action management alternatives,
4) Post-fire forest regeneration under action and no-action alternatives, and
5) Post-fire harvest/non-harvest of the younger fire-killed trees to mimic reburns?”

Ultimately forest managers are entering a new era. The heat is on for managers to counteract the massive threats to forest resilience we’re watching unfold. They will need to find novel ways to replicate low- and moderate-fire disturbances (through selective logging, prescribed burns, and managed burns), promote forest structure heterogeneity, and protect old growth forests and drought-tolerant trees. It will look unconventional, and in reality may be experimental at times – but the alternative of nonaction renders many western forests at risk of conversion, and ultimately the loss of many of our forested habitats.

Featured research

Coop, J.D., Parks, S.A., Stevens-Rumann, C.S., Crausbay, S.D., Higuera, P.E., Hurteau, M.D., Tepley, A., Whitman, E., Assal, T., Collins, B.M. and Davis, K.T., 2020. Wildfire-driven forest conversion in western North American landscapes. BioScience, 70(8), pp.659-673.

Hagmann, R.K., Hessburg, P.F., Prichard, S.J., Povak, N.A., Brown, P.M., Fulé, P.Z., Keane, R.E., Knapp, E.E., Lydersen, J.M., Metlen, K.L. and Reilly, M.J., 2021. Evidence for widespread changes in the structure, composition, and fire regimes of western North American forests. Ecological applications, p.e02431.

Hessburg, P. F., S. J. Prichard, R. K. Hagmann, N. A. Povak, and F. K. Lake. 2021. Wildfire and climate change adaptation of western North American forests: a case for intentional management. Ecological Applications 00(00):e02432. 10.1002/eap.2432

Parks, S.A., Dobrowski, S.Z., Shaw, J.D. and Miller, C., 2019. Living on the edge: trailing edge forests at risk of fire‐facilitated conversion to non‐forest. Ecosphere, 10(3), p.e02651.

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Research shows increasingly frequent, more intense wildfires in the Western U.S. will dramatically shift the landscape over the coming decades, resulting in the conversion of forests to shrublands, grasslands, or hardwood-dominated ecosystems before 2100, but strategies such as prescribed fires, managed wildfires, and silvicultural treatments could help protect forests.
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