Tag Archive for: Agrivoltaics

AgriSolar News Roundup: Agrisolar Pilot Project Results, Vertical PV Research, Translucent Solar Panel Research 

Results of Agrisolar Soybean Pilot Project Revealed by PV Developer 

“French solar developer TSE, in association with Alliance BFC, has unveiled the initial results of a pilot study in France on how solar panels can affect soybean growth. The teams observed solid vegetative growth of the soybeans, with normal flowering, fertilization, and physiological maturation. The six varieties tested presented a diversity of yields: up to 25% difference in yield under the canopy and 19% on the control field.” – PV Magazine 

Oregon Research Studies Use of Vertical PV for Crop Production 

 “There are many different ways to install agrivoltaic arrays. One common method is to raise the array to leave space for farming equipment or livestock to move freely below. Another trending design is to orient the PV arrays vertically, leaving wide open spaces in between the array rows. 

The paper found that an area about the size of Maryland would be needed if agrivoltaics were to meet 20% of U.S. electricity generation. That’s about 13,000 square miles, or 1% of current U.S. farmland. At a global scale, it is estimated that 1% of all farmlands could produce the world’s energy needs if converted to solar PV.” – PV Magazine 

Research Shows Translucent Solar Panels Optimize Crop and Solar Harvest 

“Associate professor Majdi Abou Najm from the Univ. of California, Davis, tested organic solar panels made from translucent material that absorb the blue light to generate electricity, but allow the red light with its longer wavelengths to pass through to the crops below. 

At the UC Davis Agricultural Experiment Station, Abou Najm and his team planted three different plots of processing tomatoes, a common central valley California crop, under a canopy of selective red light, another of selective blue, and a third uncovered plot. 

GNN has reported before on the recent phenomenon of ‘agrivoltaics,’ a practice of growing shade tolerant crops under solar panel arrays. The shade protects the crops from heat stress, while the plants’ transpiration humidifies the air beneath the panels, cooling them down and increasing their electricity output.” – Good News Network 

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The Science of Solar-Pollinator Habitat: Fact Sheet

How current and future research can help us understand the role of pollinator-friendly solar in biodiversity conservation.

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WEBINAR: Crunching Numbers on AgriSolar: Context and Costs of Agrivoltaics in the US

In this first episode of the AgriSolar Clearinghouse webinar series, NREL’s Jordan Macknick, James McCall, and Haley Paterson join us to discuss the context and costs of agrivoltaics in the United States.

Agrivoltaic System: Estimation of Photosynthetic Photon Flux Density Under Solar Panels Based on Solar Irradiation Data Using All-climate Solar Spectrum Model

This study focused on the photosynthetic photon flux density and employed an all-climate solar spectrum model to calculate the photosynthetic photon flux density accurately on farmland partially shaded by solar panels and supporting tubes. This study also described an algorithm for estimating the photosynthetic photon flux density values under solar panels.

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Could Windbreak Effect Significantly Decrease Evapotranspiration in Vertical Agrivoltaics?

This research argues that non-negligeable amounts of water can be saved due to the windbreak effect caused by vertical agrivoltaic systems.

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Crop-driven Optimization of Agrivoltaics Using a Digital-replica Framework

This work contributes to agrivoltaic design methodology through a digital replica and genomic optimization framework which simulates light rays in a procedurally generated agrivoltaic system at an hourly timestep for a defined crop, location and growing season to model light absorption by the photovoltaic panels and the chosen tomato crop.

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Worldwide Research Trends in Agrivoltaic Systems—A Bibliometric Review

This article provides a bibliometric analysis of agrivoltaic topics based on 121 publications indexed in SCOPUS, in which either economic assessments of agrivoltaics, agrivoltaic systems for crops and livestock animals, photovoltaic greenhouse and agrivoltaics with open field are discussed, or its ideas are used to analyze certain locations.

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Case Study: Sunzaun Vertical Solar System

By Anna Richmond-Mueller, NCAT Energy Analyst

Sunstall, a California-based solar installer, is helping farmers harvest the sun twice with their new vertical solar system, known as Sunzaun. The Sunzaun vertical solar system was originally engineered by a company in Germany. After seeing successful installations of the product in Europe, Sunstall decided to bring the design to the United States. The market for agrivoltaic installations in America is growing, but one of the biggest barriers is tied to land use. Concern about installing solar on valuable agricultural land is common, and often increases as the solar system’s footprint increases. Traditional solar installations use a racking system to secure solar modules, which are then tilted to the appropriate angle on a horizontal axis. These tilted systems require a larger amount of land compared to vertical systems. Sunzaun is installed in a portrait orientation between two piles with no racking system involved. The minimalistic design uses holes in the module frames for a simple attachment to the piles without the need for a heavy racking system, while the bifacial modules themselves allow both sides of the panel to produce energy.

Sunzaun’s portrait orientation allows adjustments to be made more quickly during later stages of a project. In systems designed with a landscape orientation, the rails used to mount panels onto the racking system are cut to fit the expected panel size. Should the size of the panel change after all other components have been finalized, the project may be delayed significantly while the rails are reengineered to fit the updated panel size. Thanks to Sunzaun’s unique design, it is easy to adapt to a change in panel size by simply adjusting the distance between each pile. It is even possible to adjust the height of the panels from the ground if needed.

Completed in 2022, the first Sunzaun installation in the United States is located on a vineyard in Somerset, California. Although the vineyard owner already has rooftop solar on the property, an interest in new solar developments and agrivoltaics led to a new system within the rows of grapevines. Composed of 43 450-watt modules connected to a microinverter and two batteries, the Sunzaun system sits on a hillside between rows of grapevines. Only one row of vines needed to be removed to make room for the system, and harvesting equipment is still able to work in the field directly next to the Sunzaun. While it is too early to say for certain what additional benefits the Sunzaun may provide beyond on-site power generation, the benefit of preserving grapevines alone is a significant win for the winery.

As the United States continues to take steps to combat climate change, innovative solar system designs are more important than ever. The Sunzaun’s streamlined design reduces the time it takes to get agrivoltaic projects off the ground. When you factor in the ability to save valuable crops and viable land with a vertical system, the minimalistic approach that Sunzaun offers farmers becomes even more appealing. A successful growing season at the Somerset vineyard will hopefully reveal even more benefits to installing this promising product and encourage others to consider the value of a vertical solar installation as well.

All photos courtesy of Sunstall Inc.

Agrisolar as Drought Protection  

By Asaf Maman and Avi Elkayam, Trigo Solar 

Declining precipitation levels and the associated reduction in arable land can negatively impact rural communities and pose a threat to food security. While utility-scale solar projects reduce greenhouse gas emissions, they can also encroach on arable lands and reduce the yield of rainfed crops. Wheat, barley, soy, corn, and other grains are cultivated in rainfed fields that are vital to food security. As precipitation levels decline and desertification spreads, arable land and farms that produce these crops are in peril.   

As solar energy is employed in the conversion from fossil fuels to renewable energy, hundreds of thousands of square miles of land will include solar development. According to the National Renewable Energy Laboratory, there will be roughly 22,000 square miles of solar in the U.S. by 2035i. It is important to understand that the actual land for solar development must be adjacent to grid or to power demand centers. The growing competition between farming, suburban development, and solar development highlights the potential for agrivoltaics.  

Agri-PV is a solution to this issue. It can significantly improve the cultivation of staple foods that substantially affect global food security by cracking the code and untying the water-land knot. By increasing the amount of water available for rainfed crops, we can increase the amount of arable land and avail a portion of it for sustainable solar development. 

In a series of field-controlled winter wheat experiments, Trigo has discovered an almost linear correlation between the amount of water supplied to cultivated area and the quantity of stem biomass and nutritional value. Based on these findings, Trigo designed an east-west solar array formation and solar table structure to both collect and regulate rainwater for redistribution into a cultivated row below. By increasing the rain capture area from both structures, enclosing, and effectively directing the rain, we managed to control the amount of water and increase it, countering the effects of declining precipitation over years.  

North-south solar array over winter wheat. Photo: Trigo Solar 

Design schematic. Source: Trigo Solar 

This design is focused on economic and efficient deployment of solar arrays that improve rain collection and redistribute water to boost crops growth, counter drought effects, and revive agricultural operations.  

Rainwater catchment design schedmatic. Source: Trigo Solar 

Benefits to this design include:  

  1. Maintaining the same yields from smaller cultivated surface area requires more limited farming operations and lower expenses, which can increase farm profitability. 
  1. Capturing more water and channeling it smartly reduces the risk of drought and the associated annual volatility and provides the farm with a drought shield. 
  1. Increased ground wetness, root growth, and wind shield from the solar rows reduces the erosion and carry away of the upper soil layer, which create irreversible damage to farms. 
  1. Preserved land under the Trigo structure can be used for future land reserve and land rotation. 
  1. The steady income from solar power generation can support farm economics and mitigate farming financial risks. 
  1. The availability of cheap, local, green power can further support many of the farm operations expected to undergo electrification in the coming decade. 
  1. The existence of a water-distribution and cheap-power system changes the economics of farming, potentially allowing the cultivation of second seasonal crop during the dry season.  

These benefits have the potential to create more win-win opportunities for effective cooperation between the agricultural and sustainable energy sectors. 

Trigo will continue its experiments to validate the benefits for major U.S. staple crops at U.S. farms to share the knowledge and promote sustainable mass Agri-PV development.  

Case Study: Soliculture Research Greenhouse

By Anna Richmond-Mueller, NCAT Energy Analyst

When it comes to conversations surrounding energy and water use in the modern world, the agricultural industry’s consumption of both is often at the forefront. As the world’s population continues to grow, humanity is tasked with the challenge of finding ways to meet both food and energy demands across the globe. “I really believe that greenhouse growing is the epitome of sustainable agriculture,” says Soliculture cofounder and CEO Dr. Glenn Alers. Whether it is the ability to greatly increase crop yields when compared to traditional open field growing, or the potential for increased water-use efficiency in combination with hydroponics, greenhouses could play a key role in addressing these concerns. Solar greenhouses also could also play a role in mitigating future energy crises. 

Soliculture began in 2012 as a startup in the Physics Department at the University of California Santa Cruz. Dr. Alers and his cofounder were conducting research on luminescent solar concentrator panels when he realized the technology’s agricultural potential. Luminescent solar panels utilize a luminescent dye that selectively absorbs a portion of the solar spectrum and readmits light at a different wavelength. The dye used in Soliculture panels absorbs the green portion of sunlight with low photosynthesis efficiency and converts it to red light with much higher photosynthesis efficiency. The panels enhance the light quality inside a greenhouse by optimizing the light spectrum for improved plant growth. Moreover, the panels contain bifacial cells that collect the light reflected from the crops planted below them. The red luminescent dye also enhances the power output of embedded cells by 15 to 32%, compared to a conventional panel. 

Installed Soliculture luminescent solar panels.

In 2019, Soliculture began a research project on Whiskey Hill Farms in Watsonville, California, aimed at developing these solar panels for use on hybrid high-tunnel greenhouses. As an active organic farm already growing produce in both field and greenhouse settings, Whiskey Hill Farms served as an ideal host for the project. The Soliculture research greenhouse was constructed from the ground up with help from a local high tunnel installer, measuring 120’ long and 25’ wide upon completion. Additional bracing was added to the roof structure, forming a “queen style” truss to support the weight of the panels. One half of the high tunnel was covered by a semi-clear plastic film that served as the control for the upcoming crop growth study, and the other was covered by Soliculture solar panels. These panels were specially designed for high tunnel greenhouses and had a cell coverage of 42%.  

Interior of research greenhouse with panels installed.

The project hit a temporary snag when waterproofing the panel racking system proved to be more of a challenge than expected. At first, horizontal mounting bars were attached to the tubing of the greenhouse’s roof frame and foam weather stripping was installed between the panels to create a watertight seal. Water was still able to leak through at the corners and where the mounting bolts connected the panels to the roof. Knowing the potential for these leaks to cause erosion and negatively impact crop growth, the Soliculture team returned to their laboratory and created a modified racking system specifically for high tunnel application. This new system used mounting brackets that attached to the bottom of the frame and utilized a rubber “T” gasket inserted between the panels to create a seal. Finally, the plastic film portion of the roof was attached to the panels using an aluminum channel screwed into the panel frame and “wiggle wire” to hold the plastic film in position. With a waterproof roof in place, the crop trail was ready to commence.  

The following crops were selected for planting following the completion of the high tunnel in mid-November: strawberries, red romaine lettuce, red butter head lettuce, cilantro, mustard greens, and turmeric. To ensure the trial’s results would translate to commercial production, the research team used common commercial growing methods throughout the duration of the trial. These methods included drip irrigation with untreated well water, sand filtration, and liquid organic fertigation. By the end of the trial, the majority of the crops grown under Soliculture panels matured close to two weeks ahead of those grown under the clear film portion of the high tunnel. The fresh weight for the under-panel crops was superior as well, with red butter head lettuce seeing the greatest benefit at 145% higher weight. Mustard greens weighed in at 95% higher, cilantro at 35%, romaine lettuce at 32%, and turmeric at 25%. The strawberry fruit showed no statistically significant difference in fresh weight, but the single 5’ by 120’ planted bed yielded more than 350 pounds of fruit by the end of July.  

Crops grown under Soliculture panels.
Crops grown under plastic film.

On top of the very successful crop trial, the power generated by the greenhouse panels was used by Whiskey Hill Farms to power their day-to-day operations. A total of 58 Soliculture panels provided the farm with a 6kW system, which was connected to an inverter. The AC power was then fed back into the farm’s power system, a testament to how greenhouse solar can benefit the farm beyond improving plant growth.  

The field of agrivoltaics is constantly evolving, with numerous researchers and farmers searching for the ideal nexus between the agricultural industry and energy production. Soliculture’s contributions to agrivoltaics is important for farmers who have reservations about growing food underneath and around solar panels. “We haven’t seen any negative effect on plant growth,” Dr. Alers says, referring to the Whiskey Hill Farms project and several other successful Soliculture installations across the United States and Canada. Greenhouse production has always had the potential to help alleviate the water crisis and increase the amount of food grown per acre, but Soliculture’s technology is giving it a bright future in energy production, as well. 

All photos courtesy of Soliculture