Agrivoltaic Technology: Multi-Tasking Land-Use

By Mark Marsh, Research Analyst

Opportunity

Large solar projects are typically designed for the sole purpose of producing energy. Energy-centric planning gives no consideration to the displacement of agriculture or other land development activities. Unused space beneath panels is wasted, adding nothing but additional maintenance costs in the control of unwanted vegetation. However, some project developers and farmers began turning these costs into opportunities by creating mutually beneficial arrangements to manage vegetation by grazing sheep or other small animals under solar installations and around the buffers. This experience led to the obvious question: why couldn’t it work with other agricultural systems?

A Sum Greater than the Whole

Research and practical experience have shown that with appropriate design, combined systems can be more profitable than either solar or agriculture alone. The main reason for this is that these dual-use systems create spatial overlap between the two uses and although neither use achieves 100% economic efficiency, in combination, each use can achieve greater productivity per acre than they can alone.

Too Much of a Good Thing?

One reason for this additive miracle is a property known as the light saturation point of plants. It is the point at which more sunlight only increases leaf temperature and causes plants to use more water without increasing photosynthesis.⁵

A carefully designed agrivoltaic system can create advantageously shifting patterns of sun and shade in the field, optimizing power production when plants might benefit from increased shading during the heat of the day and optimizing plant growth on the shoulders of the day when power production has dropped.

Similarly, the systems can be manipulated throughout the growing season to account for the angle of the sun, the growth stage of the crop or even the timing of agricultural operations.

The benefits of agrivoltaic systems also flow in the opposite direction as the cooling effects of plant evapotranspiration help reduce panel temperatures and maintain their operating efficiency.

Strategies

Three common approaches to agrivoltaic design include increased spacing between rows of solar panels, increased height of mounting hardware and the introduction of tracking actuators. By adjusting row widths, patterns of sun and shade are manipulated to favor the target crop. Increased panel height can create more farming opportunities, allowing the introduction of taller crops, animals and farm equipment. Trading fixed panel mounts for tracking actuators facilitates the daily and seasonal optimization between energy and agricultural production.

Other ideas being explored include bifacial panels, the undersides of which can harvest reflected light. Still another interesting approach involves the development of semi-transparent panels that would intercept and convert to electricity only those wave-lengths of light plants cannot utilize.

Tradeoffs

Utility-scale agrivoltaic systems can potentially increase land revenue, provide income and employment diversification to rural economies and may help insulate them from fluctuating farm incomes by providing more predictable revenue streams.

However, agrivoltaic systems are not without their drawbacks. They add to the complexity of planning and design for both uses. They introduce fixed infrastructure to agricultural fields which may reduce farming flexibility.

Solar power companies and their insurers are still averse to the risks of introducing machinery in close proximity to photovoltaic infrastructure.

Siting utility-scale solar projects can often meet with community resistance. Objections are frequently raised regarding project aesthetics, the loss of farmland and the potential disruption to the broader agricultural supply economy tied to farming.

Nevertheless, because solar leases may provide roughly two to four times more revenue than for example, corn farming, the financial incentives may be sufficient to drive continued innovation and adoption.^6,7

References

1. Solar Energy in the United States. (n.d.). Office of Energy Efficiency & Renewable Energy. Retrieved August 23, 2022, from https://www.energy. gov/eere/solar/solar-energy-united-states

2. National Renewable Energy Laboratory, Ong, S., Campbell, C., Den- holm, P., Margolis, R., & Heath, G. (2013, June). Land-Use Requirements for Solar Power Plants in the United States (NREL/TP-6A20-56290). NREL. https://www.nrel.gov/docs/fy13osti/56290.pdf

3. 3 Reasons Why Nuclear is Clean and Sustainable. (2022, June). Office of Nuclear Energy. https://www.energy.gov/ne/articles/3-reasons-why- nuclear-clean-and-sustainable#:~:text=Nuclear%20energy’s%20land%20 footprint%20is%20small&text=A%20typical%201%2C000%2Dmega- watt%20nuclear,require%2075%20times%20more%20space

4. Margolis, M. (n.d.). Solar Futures Study. National Renewable Energy Laboratories. Retrieved August 23, 2022, from https://www.nrel.gov/anal- ysis/solar-futures.html

5. Avasthi, A. (2005, January 21). Too Much of a Good Thing: Plants Have a Defense Mechanism to Protect Them Against Excess Sunlight. Science. https://www.science.org/content/article/too-much-good- thing#:~:text=Plants%20harvest%20energy%20from%20the,that%20 can%20destroy%20the%20plant

6. University of Nebraska Extension. (2021, November). 2022 Nebraska Crop Budgets (No. EC872). Institute of Agriculture and Natural Resources. https://cropwatch.unl.edu/Budgets/2022/2022-nebraska-crop- budgets-010322.pdf

7. What is the Average Solar Farm Lease Rate? (n.d.). Strategic Solar Group. Retrieved August 23, 2022, from https://strategicsolargroup.com/ what-is-the-average-solar-farm-lease-rate/