Tag Archive for: Solar

Sheep grazing under solar panels.

By Jessica Guarino and Tyler Swanson  

The U.S. agrivoltaics industry continues to grow as the desire to pair solar energy production land uses with pollinator habitats, livestock grazing, and crop production increases. However, while the excitement around agrivoltaics in all its forms blazes a new trail for what solar energy land use can look like, eager landowners and developers face a daunting challenge: state laws and local zoning ordinances that have not considered the possibility that agricultural and solar energy production could feasibly be located on the same tract of land. 

Through Agrivoltaics in Illinois: A Regulatory and Policy Guide, researchers at the University of Illinois Urbana-Champaign’s Bock Agricultural Law & Policy Program analyze both the state and local laws that will impact agrivoltaic development in Illinois. The guide pays particular attention to county zoning ordinances, each of which define solar energy, and set the requirements necessary to develop it, in their own unique way. Agrivoltaics in Illinois allows landowners and potential solar developers to easily understand the requirements to build solar in their county and may also point developers towards counties where solar energy development faces a lower burden from the zoning board. Further, developers can read through the specific definitions that a county has for solar energy, which may have an impact on the development of agrivoltaics. For example, in many counties, a solar farm is the principal use for the land on which it is located, which could have negative implications for a landowner wishing to practice agrivoltaics and retain the tax benefits associated with land being classified as an agricultural use. Meanwhile, other counties state in their zoning ordinances that a solar installation under a specified acreage is considered a “solar garden” and thus is classified as either an accessory or special use of the land. 

Squash growing under solar panels.

Agrivoltaics in Illinois: A Regulatory and Policy Guide, while focused on analyzing the state laws and local zoning ordinances of Illinois, aims to inform all landowners, farmers, and solar energy developers of the types of laws and ordinances that should be taken under consideration when exploring the deployment of an agrivoltaic system. This guide is also a resource for state and local policymakers seeking to understand what impacts existing policies may have on the development of agrivoltaics. For example, the Renewable Energy Facilities Agricultural Impact Mitigation Act is a state law requiring a deconstruction plan for wind and solar energy facilities when they reach their end of life that also provides assurances to the landowners that the land will be restored for agricultural use, which will impact agrivoltaic installations. Additionally, a local official could review the numerous figures and tables in the guide to understand what solar energy requirements are most common, as definitions and requirements for solar energy facilities vary by location.  

As the agrivoltaics industry grows, it will become increasingly important to understand the regulatory framework in which it will exist. Many current zoning ordinances consider solar energy a threat to agriculture and regulate the industry accordingly, which may inhibit the ability of eager farmers and solar developers to deploy the practice. Likewise, state governments have the power to influence the development of agrivoltaics through laws such as the Renewable Energy Facilities Agricultural Impact Mitigation Act. With the legal analysis presented in this policy guide, the authors hope that it will be used by stakeholders to foster informed agrivoltaic regulations and deployment of the practice. 

Photos: AgriSolar Clearinghouse 

Picture 1. Solar panels powering the Solar Oyster Production System (SOPS) platform.

From filtering water to creating habitats for other marine species, oysters are a vital component of the Chesapeake Bay’s ecosystem. On land, they are the center of a rich cultural heritage as one of the region’s most valuable fisheries. Generations of families have made a living harvesting the bivalves, whose reefs were once so large that they posed navigational hazards for ships traversing the Bay. However, decades of pollution, disease, and overharvesting have devastated the oyster population. Modern restoration efforts and harvesting regulations offer a glimmer of hope for the bivalve, and Solar Oysters is making a big impact with its revolutionary oyster-production platform powered by solar.

Prior to the establishment of Solar Oysters, the idea to create a floating solar array came to Mark Rice, President of the Baltimore-based engineering firm Maritime Applied Physics Corporation (MAPC), while he was working on a project on the Chesapeake Bay. A local power plant utilized Chesapeake Bay water to cool the plant, and there was a growing interest in mitigating thermal discharge into the Bay. Rice and his team decided the best course of action was to remove incident solar energy from the water to offset the thermal effluent. They knew solar panels would generate valuable electrical energy while also helping to keep water temperatures down and began designing floating solar platforms to tackle the problem. As they were planning the floating arrays, they realized a source of ballast was needed to weigh down the systems and found an opportunity to help improve oyster aquaculture in the Bay simultaneously. Led by Steve Pattison, the environmental strategy firm EcoLogix Group collaborated with MAPC to provide valuable insight about stakeholder engagement, local aquaculture, siting, and environmental permitting. The two companies formalized their relationship in 2019 with the launch of Solar Oysters LLC. By October 2021, Solar Oysters had raised enough money through private funding to construct the first Solar Oyster Production System (SOPS) prototype—a floating high-density oyster-production system automated through solar energy—in Baltimore Harbor.

Picture 2. Graphic design of the SOPS prototype.

Measuring 40’ by 25’, the platform has 12 375-watt solar panels attached to the roof capable of generating 36 kWh, alongside four on-board batteries with a 14.4 kWh storage capacity. The solar array powers a system of five vertically rotating ladders on timers, each consisting of 23 rungs capable of holding up to five oyster baskets per rung. This provides a maximum capacity of 575 baskets. As the ladders rotate, the oysters are exposed to different water quality parameters, including temperature, salinity, and dissolved oxygen, resulting in uniformity among all ladder basket positions. At the top of the rotation, the baskets are completely out of the water and exposed to sunlight before resubmerging as the next rung peaks. A manual spray wash system is mounted onboard and pulls water directly from the Bay, allowing those tending the platform to clean the baskets and oysters as needed.

Picture 3. SOPS ladder system
Picture 4. Platform manager Emily Caffrey with an oyster basket from the ladder system.

Compared to traditional oyster farming methods, the SOPS platform brings a technological advancement to an industry that has not changed considerably in decades. On farms where the oysters are grown at surface level in floating cages, workers must manually flip each cage over to prevent biofouling. Biofouling refers to the accumulation of organisms such as algae, barnacles, or mussels on the oyster shells and equipment, thus impeding the growth of the oyster population. SOPS greatly reduces the manual labor needed to keep the oysters healthy, thanks to the rotating ladders and spray system. Moreover, the system’s vertical design drastically increases the number of oysters produced per acre. While a traditional float farm may produce between 250,000 and 400,000 oysters per acre, SOPS can produce up to 250,000 oysters on one 0.02 acre-sized barge. This small footprint is an advantage in securing permits or leases compared to a traditional farm that often requires permitting several acres.

Solar Oysters’ first growing season was in partnership with the Chesapeake Bay Foundation as a participant in the Baltimore Harbor oyster gardening program. A grant from the Abell Foundation afforded Solar Oysters the opportunity to onboard spat-on-shell oysters in the fall of 2021. After the 2022 growing season, about 40,000 oysters were transplanted to the Chesapeake Bay Foundation’s sanctuary reef at Fort Carroll, where they significantly helped to advance the Foundation’s oyster-restoration efforts. That same day, Solar Oysters accepted an additional 490,000 spat-on-shell oysters for the upcoming 2023 growing season. Concurrently, seed oysters were being grown to evaluate the effectiveness of the SOPS technology for the oyster consumption market, onboarded at the same time as the first spat-on-shell cohort. After 12 months of growth, the seed oysters measured between 2.5 and 3 inches in length, a size that could take 18 to 24 months to reach using traditional growing methods.

Picture 5. Seed oysters.
Picture 6. Spat-on-shell oysters.

Solar Oysters’ goal is to develop, manufacture, and sell the SOPS technology to organizations focused on oyster restoration or growing oysters for market. In 2023, they plan to continue research on the SOPS platform as they narrow down the best practices for growing oysters on the prototype. Other improvements to the system will include installing a semi-automated spray wash system that replaces the current manual one onboard. The 2023 season will also see Solar Oysters continue to contribute to restoration efforts in the Chesapeake Bay. With such an encouraging first growing season of both spat-on-shell and seed oysters, the technology has the potential to address environmental concerns while also modernizing oyster aquaculture for growers in the Chesapeake Bay and beyond.

All photos courtesy of Solar Oysters LLC.

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 crop.

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.  

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 

In this study, a donor:acceptor polymer blend is optimized for its use in laminated devices while matching the optical needs of crops. The study reveals degradation modes undetectable under laboratory conditions such as module delamination, which accounts for 10–20% loss in active area. Among the active layers tested, polymer:fullerene blends are the most stable and position as robust light harvesters in future building-integrated organic photovoltaic systems.

In this article, researchers evaluated seasonal patterns of soil moisture (SM) and diurnal variation in incident sunlight (photosynthetic photon flux density [PPFD]) in a single-axis-tracking agrivoltaic system established in a formerly managed semiarid C3 grassland in Colorado. Their goals were to (1) quantify dynamic patterns of PPFD and SM within a 1.2 MW photovoltaic array in a perennial grassland, and (2) determine how aboveground net primary production (ANPP) and photosynthetic parameters responded to the resource patterns created by the photovoltaic array. Investigators found relatively weak relationships between SM and ANPP despite significant spatial variability in both. Further, there was little evidence that light-saturated photosynthesis and quantum yield of CO2 assimilation differed for plants growing directly beneath (lowest PPFD) versus between (highest PPFD) PV panels. Overall, the AV system established in this semiarid managed grassland did not alter patterns of ANPP in ways predictable from past studies of controls of ANPP in open grasslands.

This study explores how a matching model can be utilized for empirically planning renewable energy siting using an illustrative case study in Japan. The matching algorithm enables the matching of sites and renewable energy specifications, reflecting the true preferences of local people regarding facility siting.

In this article, researchers in Korea analyze the profitability of agrivoltaics and its implications for rural sustainability. The profitability of agrivoltaics is verified in all studied regions, and the order of profitability and productivity by region are opposite to each other. Researchers suggest that regions with lower productivity may have a higher preference for installing agrivoltaics, implying the installation of agrivoltaics provides a new incentive to continue farming even in regions with low agricultural productivity.

This resource aims to guide informed decisions by landowners, investors, planners, and government officials in considering the planning and siting of grid-scale solar systems in Pennsylvania. The intent is to balance and promote the goals of sustainable income-generation and protection of water, soil, and valuable agricultural land resources.