Tag Archive for: Agrivoltaics

The International Landscape of Solar Farms and Agrivoltaics

Rebecca A. Efroymson, Environmental Scientist, Oak Ridge National Laboratory); and Jonathan M. O. Scurlock, Chief Adviser for Renewable Energy & Climate Change, National Farmers’ Union of England and Wales

Solar photovoltaic (PV) power, the most popular form of renewable energy on farms, is being adopted all over the world. Growers and processors of food worldwide have a long history of using the sun’s energy to produce and dry their crops, and solar PV is adding a modern twist to our relationship with the sun. It is no surprise that some of the best locations on Earth for harnessing solar energy are often ideal places for agriculture and horticulture. However, intelligent design for multi-purpose land use can alleviate real or perceived conflicts between energy and food production. Solar modules can shade crops where light intensity is in excess of crop requirements, reducing water evaporation; they can be mounted on agricultural buildings to power farm business energy needs; and they can export low-carbon electricity to meet wider demands for “green” power and the transition to a “net zero” global economy.

We use the term agrivoltaics broadly to describe any combination of agricultural activity and solar electricity production, but outside the USA, the term usually refers more specifically to the intimate juxtaposition of solar modules and agricultural land use. Examples include PV modules mounted at a height of several meters to allow access to land below by farm machinery or large livestock, where they provide shelter from storms or excessive solar radiation, and the integration of solar PV into greenhouses for crop protection.

We caught up with a range of projects across three continents to report upon their objectives and their future prospects.

Around 30% of British farmers have either rooftop or ground-mounted solar energy. The National Farmers Union (NFU) aspires to the goal that every farmer and grower have the opportunity to become a net exporter of low-carbon energy. The falling capital cost of both solar and battery electricity storage has resulted in a growing pipeline of solar installations across a range of sizes, including large 100-hectare (ha) and 1,000-ha solar farm projects, largely independent of government policy support. The NFU advises farmers that solar PV can be deployed across entire fields, as small, ground-mounted installations around field margins or adjacent to farmyards, on farm buildings, and on domestic rooftops. Developers of solar farms are encouraged by the NFU to follow best practice guidelines for multi-purpose land use, combining energy production, continued agricultural management such as grazing, and creation of wildlife habitat. NFU’s strong preference is for large-scale solar farm development to be located on lower-quality agricultural land, avoiding as much as possible the most productive and versatile soils. Roof-mounted solar systems in Britain continue to offer a sound investment, making between 10% and 25% simple return on capital annually at current electricity prices, depending on how much of the generated power is used on-site. At of the end of 2021, about 70% of the United Kingdom’s 14 gigawatts of solar power generation capacity was located in the agricultural sector.

Multi-purpose land use – sheep grazing and hedgerows of natural vegetation around a large (44-megawatt) solar farm near Haverfordwest in the United Kingdom. Photo Credit: Jonathan Scurlock

In the Netherlands, the Symbizon project at Almere, near Amsterdam, has brought together a Swedish energy company with Dutch researchers and a private organic farm to construct a 700-kilowatt solar park with alternating strips of PV modules and rows of crops. Starting in spring 2023, the production of herbs will be investigated, and potatoes, beans, beetroot, broccoli, and grains may be included in this pilot study. Pivoting double-sided (bifacial) solar modules will catch the reflected light from soil and crops.

Nearby in Germany, Goldbeck Solar is an innovator in solar agrivoltaic structures. The company has developed a system of solar PV arches that slide on side rails, allowing farmers to shelter or expose various crops. Typically oriented east to west for maximum solar energy yield, the arches span up to 9 meters, at a height of 2.5 to 3 meters, allowing a degree of control over temperature, humidity, and light. These agrivoltaic modules can also provide shelter for livestock from extreme weather, such as high temperatures and hail. The modules are currently undergoing trials in the four-year Sunbiose project in the Netherlands, which had already succeeded in growing raspberries under the partial shelter of solar PV modules. 

Agrivoltaics are being tested in East Africa, where their shade can reduce heat stress and water loss, and farmer incomes in disadvantaged rural communities may be improved. An experimental facility opened in 2022 in Insinya, Kenya, through partnership with Universities of Sheffield, York and Teesside in the United Kingdom, the Stockholm Environment Institute, World Agroforestry, the Centre for Research in Energy and Energy Conservation, and the African Centre for Technology Studies. Some 180 PV modules, each 345 watts, have been installed about 3 meters above the ground, allowing a variety of crops to be grown under the shade from the strong equatorial sun. Geoffrey Kamadi of The Guardian reports that benefits include improved yields of cabbage, eggplant, and lettuce; a reduction in water loss; and a reduction in high daytime temperatures and UV damage.

Small-scale agrivoltaic development (less than 0.1 ha) has progressed rapidly in Japan, producing 0.8% of the total solar power generated in the country in 2019. Japan has perhaps the greatest number of agrivoltaic farms to date, with more than 120 plant species being cultivated on agrivoltaic farms. The Solarsharing Network provides a catalog of 27 agricultural crops (Solar Sharing for FUN | SOLAR SHARING NETWORK| Solar Sharing Association of Japan (solar-sharing.org) and their light needs. Innovative crop systems include tea, according to Makoto Tajima and Tetsunari Lida of the Institute for Sustainable Energy Policies.

One pilot agrivoltaic project in New Zealand is seeking low-growing flowering plants like alyssum to attract bees and reflect light up to rows of bifacial PV modules. The high energy demand of irrigation systems can benefit from on-farm solar energy. In New Zealand, as in the U.S., UK, and Australia, sheep and other small livestock graze under solar modules, avoiding the need for mowing. As New Zealand reporter Delwyn Dickey notes, the success of such large-scale agrivoltaic systems (i.e., solar farms) may be determined by an insistence upon dual land use during the consenting process and the willingness of solar energy development companies to adopt dual land use.

Clearly, from small-scale intimate mingling of solar PV with agricultural production to multi-purpose land use in the largest of solar farms, the merits of harvesting the sun’s energy twice are appreciated the world over. The outlook for agrivoltaics is bright indeed.

Luminescent Enhancement for Combined Solar and Commercial Agriculture

This project developed a new racking/mounting system combined with a new specialized solar panel for low-cost implementation in a hybrid high tunnel greenhouse. The project successfully demonstrated that high value crops can successfully be combined with solar electricity production, even resulting in improvements to yields for certain crops.

Luminescent Enhancement for Combined Solar and AgDownload

AgriSolar News Roundup: Tomatoes in California, Agrisolar Research in the Southwest, Symbizon Project in Netherlands 

Research Suggests Agrivoltaics Could Help California’s Tomato Industry 

“Emerging research suggests growing tomato plants below and between solar panels could help the country’s billion-dollar-plus tomato industry, especially in places where it faces increasing stress from heat and drought. Shade provided by solar panels can help conserve water, create humidity, and lower temperatures that can become too much even for heat-loving tomatoes.” – Energy News Network  

Research Shows That Crops and Solar Panels Are Highly Compatible 

“By elevating solar panels far enough above the ground so people, plants, and animals can operate underneath, we can ‘essentially harvest the sun twice,’ says University of Arizona researcher Greg Barron-Gafford. Enough sunlight to grow crops gets past the panels, which also act as a shield against extreme heat, drought, and storms. 

Barron-Gafford and his team were able to triple the yield of chiltepin peppers, wild chiles common to the area, by growing them under PV panels on test plots vs. unshaded control plots; cherry tomato output doubled. What’s more, the soil on the PV plots retained 5 to 15 percent more moisture between waterings. ‘The plants aren’t just freeloading under the solar,’ adds Barron-Gafford; they actually help the panels become more efficient. ‘Every time plants open their pores to let carbon dioxide in, water escapes,’ he explains. This lowers the temperature beneath the panels—the same way restaurant misters make outdoor dining bearable in scorching heat. The cooling effect, the researchers calculated, resulted in a 3 percent bump in electricity production during the growing season.” – Mother Jones 

Symbizon Project Aims to Find New Ways to Combine Agriculture and Solar 

“During a four-year pilot project, Dutch independent research organization TNO, in collaboration with Vattenfall and Aeres University of Applied Sciences (UAS), is developing a sun tracking algorithm that monitors various factors, such as crop yield, energy yield and the effects of herb strips, weather forecast, energy price and soil condition.”  – Vattenfall 

Case Study: Texas Solar Sheep  

In partnership with Lightsource BP, Texas Solar Sheep grazes over 1,800 sheep on a solar site in Deport, Texas. These sheep are grazed in groups of 50 to 75, 250 to –270, and even 500, making Texas Solar Sheep one of the largest Agrisolar grazing operations in the United States.   

All 1,800 sheep are grazed and managed on one solar site, which has 18 individual pastures. The sheep are grazed year-round on the same site. The area gets maybe one snowfall a year, which is not a huge issue for them, as the solar panels provide good protection from elements for the sheep. The farm may buy one stockpile of hay for the winter if they feel it is necessary as a precaution, but stockpiling food is not a great concern on this operation.  

No mowing duties are required on this site, thanks to responsibly managed, rotational grazing of the sheep. There are many weeds that sheep will not eat, so they must be manually removed. After some time, if those weeds can be removed from the site, then there is no need for mowing or the use of gas or diesel-operated maintenance equipment. Graziers mowed this site four times in 2021 and have not mowed at all in 2022 as of the end of September.  

J.R. Howard, owner of Texas Solar Sheep, says it is important for new graziers to know that the client of this operation is the solar site, and the grazier is providing a service to replace mowing on the site. The sheep-grazing service has been shown to provide significant benefits to the solar site, including enhancing the health of the turf, reducing runoff from rainfall, and providing crucial shade relief to both the grasses and the sheep during drought periods like those seen in 2021.  

Photo courtesy of Texas Solar Sheep

Healthy Turf Prevents Runoff 

The site has realized benefits from preventing rainfall runoff as a result of developing healthy turf. There was hardly any runoff after 3 inches of rainfall, due to the enhancement in turf quality from responsible grazing management, according to Howard. Healthy turf is a result of not overgrazing individual areas and managing proper sheep rotation. The sheep are not allowed to eat to the bare ground, resulting in what is known as a healthy turf that allows the land to capture and hold the water when it rains, resulting in less runoff and other associated issues. Howard said the land is back to looking like “normal land” and not “golf courses.” 

Shade Relief for Grasses and Sheep 

During the drought of 2021, the solar panels provided crucial shading for the grasses and the sheep. The grass between the panels that did not have shade did not do as well as the grasses that were getting shade from the panels. “The shade support really helped a lot,” Howard said.  

Sheep typically feed in the morning and then hang out in the shade during the day, which the panels provide plenty of. Unlike goats and cattle, sheep do not damage equipment by rubbing against it, climbing on it, or chewing on wires as some goats do. The sheep can be comfortable under the panels during the day with little, if any, threat of damage to equipment. 

Rotational Fencing  

One challenge that the operation has dealt with is constantly rotating the sheeps’ pasture, which needs to be consistent and on schedule. Limiting grazing to smaller areas more often, as opposed to one large area less frequently, is ideal. However, this approach requires fencing that must be moved regularly. The operation requires “cross fences” to break large blocks of land into smaller pastures. Moving fences is one of the most consistent tasks of the operation, but it is manageable.

 

Photo courtesy of Texas Solar Sheep

Breeding for Agrisolar Conditions 

The solar company allows the sheep owners to breed lambs when they want. The sheep live on the solar site from birth until they are sold or pass away. The sheep are also checked by a veterinarian at various times during their life cycle on the site. Owners breed sheep on site, to “get the ewe they want,” Howard said.  

This selective breeding process is an attempt to breed a sheep genetically superior in parasite resistance than previous generations of sheep. These sheep would be specifically resistant to parasites during the lamb phaseand the lactating ewe phases of their life, which are often when farmers struggle with parasites infecting their sheep. Due to the selective breeding process on this site, the sheep will be more resilient to the conditions they experience in Texas, which includes hot temperatures and prolonged, wet conditions. 

Although Dorper sheep, which originated in South Africa, are genetically capable of handling hot temperatures, they are being breed with Katahdin and St. Croix to enhance their genetic capabilities further—making them the most ideal sheep for agrisolar operations in these climate conditions. 

Photo courtesy of Texas Solar Sheep

What New Graziers Should Know 

New graziers should know that this is not a grazing lease with the solar company but, rather, a grazing service business. As a service business, people with sheep will have a customer that they are providing a service to. This requires graziers to spend more time on-site where they can correct issues quickly. If sheep get out of the fenced paddocks, graziers can get them back to their assigned areas quickly. Sometimes sheep pass away and need to be removed as quickly as possible. Being on-site allows for that. If sheep are sick, they can be attended to quickly. The grazier can also ensure that sheep have constant access to water.  

The solar company also benefits from having Texas Solar Sheep staff on-site regularly. “We are out there more than the solar folks, so we see issues for them, too. It has been an extra set of eyes for them on the solar equipment, so that has been a significant help for them, as well. If they see downed panels, damaged wiring, or even fires, they can report it quickly and get it taken care of,” said Howard. “There is a public eye on this stuff, so we want to make sure we are doing it right.”  

Howard stated that grazing is the future of utility-scale solar. It is important that the first few big sites get it right. With great partners like Lighthouse BP, Texas Solar Sheep has been able to scale up its operation, and is planning for larger sites for the future, meaning more sheep on more solar sites. 

Howard said the family farm had about 300 ewes and having the opportunity to partner with Lightsource BP has allowed them to have extra land to graze and scale up their operation. “We’re not a big landowner, and this allowed us to scale up a lot, to 1,800 ewes.” 

Water Evaporation Reduction by the Agrivoltaic Systems Development

The triple benefits of the AgriVoltaic Systems Development (AVSD) have been well demonstrated, not only for the PV electricity generation but also for reduced water evaporation, enhancing further the benefits of simultaneously crop growth on the same land area. However, the reduction rate of the water evaporation of AVSD has not been investigated in a quantitative way. Therefore, this study conducted experiments to measure water evaporation reduction under the Concentrated-lighting Agrivoltaic System (CAS) and the Even-lighting Agrivoltaic System (EAS). Evaporation containers and pans were placed in the bare soil (CK) under the CAS and the EAS. Our results showed a significant reduction in water evaporation under CAS and EAS. Cumulative soil surface evaporation of CK, CAS, and EAS for 45 days was 80.53 mm, 63.38 mm, and 54.14 mm. The cumulative water evaporation from soil and pan surfaces decreased by 21 % and 14 % (under CAS), 33 %, and 19 % (under EAS), respectively. The slope β1 ∕= 0 of simple linear regression showed a significant positive relationship between evaporation time and cumulative water evaporation. The correlation coefficient in all treatments was more than 0.91, suggesting a robust linear relationship. The feasibility of AVSD could significantly reduce irrigation water, enhance crop growth, and generate electricity simultaneously on the same agricultural land.

Waterevaporationreductionbytheagrivoltaicsystemsdevelopment-1Download

Rainwater Management in Agrivoltaic Systems – Research & Development Potential

Agrivoltaics is a concept in which a piece of land is simultaneously used for both energy and food production by mounting photovoltaic modules at a certain height above (or in between strips of) agricultural land. A local and system-level incorporation of water management is imperative to the sustainable implementation of agrivoltaics. Water raining on the module can be gathered and used for distinct purposes: groundwater recharge, crop irrigation, and cleaning and cooling of the PV modules. This research provides an initial overview of positive and negative impacts for each water use concept and outlines issues that should be taken into consideration and the potential for research and development. Various Managed Aquifer Recharge (MAR) technologies are a way to clean and store the water periodically in an underlying aquifer. Irrigation increases yield within the plant level and therefore increases the system’s output. Thanks to the power supply generated by the PV modules, high-tech irrigation systems can be implemented in agrivoltaic systems; the special adaption of irrigation systems to agrivoltaics poses significant potential for research and development. Meanwhile, the necessity, i.e., profitability of cleaning and/ or cooling PV modules depends on local environment and economic factors. Several cleaning techniques have been developed to mitigate soiling, ranging from manual cleaning to fully automatic cleaning systems. In agrivoltaics systems, the soiling risk can increase. Semi-automatic systems seem to have the greatest potential for agrivoltaics, because they can be used with farming equipment. Multiple cooling techniques have been developed to decrease cell temperature to increase power output, with some of them involving water. Water flowing over the module surface is a promising a promising cooling technique for agrivoltaic applications. Attaching a perforated tube to the upper edge, the entire module can be covered in a thin film of water which cools very effectively (while also cleaning the surface). A closed-circuit system could be created involving the technical components used for rainwater harvesting. The economic feasibility of cooling panels in agrivoltaic systems needs to be investigated. In certain locations, rainwater-harvesting could also be relevant for ground-mounted PV systems.

Roessner_4AO84Download

AgriSolar News Roundup: Agrivoltaic Research in Australia, Solar and Farmland Compatibility, Agrisolar Development in Oregon

Australian Researchers Develop Solar Panels Optimized for Agrisolar  

“University of New South Wales researchers have teamed up with Tindo Solar to develop a line of semi-transparent modules, specialized for agrivoltaic cropping, which will use nanoparticles tuned to capture different parts of the light spectrum. ‘There is evidence you don’t need the full spectrum and some plants will work even better if you provide them with only part of the spectrum,’ project lead and UNSW Associate Professor Ziv Hameiri tells PV Magazine Australia. Crucially, he says, the project will also open a line between farmers, solar researchers and industry, creating the potential for mutual benefits.”  – PV Magazine 

Agrisolar Operations Show That Solar Does Not Compete with Farmland 

“In short, Agrivoltaics is a rapidly growing branch of the energy transition. It is being applied to all manner of crops across the world. All kinds of benefits are emerging, with China even using it to reverse desertification. Not only is it expanding clean energy production, it is providing a vital second income stream for farmers. Banning it would cut off a really important opportunity for Britain’s farmers, at a time when rural poverty is a real issue.” – Green Peace 

Oregon State Develops 5-Acre Agrisolar Project 

“Oregon State University has started construction on a $1.5 million research project to optimize dual-use, co-developed land hosting solar photovoltaic arrays and agriculture. The five-acre Solar Harvest project is located at Oregon State’s North Willamette Research and Extension Center in Aurora, Oregon, 20 miles south of Portland. The 326-kW project is the result of a partnership between Oregon State and the Oregon Clean Power Cooperative, which developed the solar array and financed the construction of the solar array.” – Solar Power World 

Homeowner’s Guide to the Federal Tax Credit for Solar Photovoltaics

This guide provides an overview of the federal investment tax credit for residential solar photovoltaics (PV). The federal residential solar energy credit is a tax credit that can be
claimed on federal income taxes for a percentage of the cost of a solar PV system paid for by the taxpayer.

Guide-to-Federal-Tax-Credit-for-Residential-Solar-PV-9-22Download

Case Study: ENEL Green Power’s Lake Pulaski

Lake Pulaski is an agrivoltaic solar power plant site developed by Enel Green Power that spans over 68.2 acres in Buffalo, Minnesota. This site is one of 16 developed for the Aurora Distributed Solar LLC project in 2017, supporting pollinators, grazing, and an apiary. The layout consists of 34,668 panels at 315 watts each, spanning over 500 individual arrays. The total plant system size is 10.92MW (dc). Each panel has a SolTech single, horizontal axis tracker to follow the sun path and optimize production. This tracker was chosen over the more standard axis-pole trackers due to their ability to allow curves in the array installation to accommodate the rolling landscape. The developers strived to install the system with minimal land disturbance to maintain the landscape and reduce excavation, thus allowing the panels to move with the rolling hills. Panel height was design to be approximately 2.5 fee from the ground at the maximum tilt angle of 45o to allow grazing sheep to pass under without harm to sheep or panels. This sets the total height of each array at a maximum of 10 feet.

Showing how the panel height is appropriate to allow for sheep to graze under panels.
Solar tracking system with grazing sheep

The landscape is grazed once a year near the end of September for one month to reduce the need for mowing, save on labor and gas, and maintain a healthy soil chemistry. Graduate students at Temple University in Pennsylvania are conducting studies on the benefits of grazing, such as soil composition, a reduced mowing, and a reduction in spraying for weeds. Eight of the 16 Aurora project sites are grazed for research purposes. Occasional mowing is required if the area has a high-growth year. Minnesota Native Landscapes (MNL) developed the original native seed profile to help promote pollinator activity under the panels. The final seeding was completed by Westwood Professional Services. MNL also maintains the pollinator and native landscape. Bare-grounded spraying is used to kill off unwanted invasive species, such as thistle. These areas are then fenced off to prevent wildlife and sheep in the area. Soil samples are taken from sprayed and mowed areas for research. Lake Pulaski also promotes the bee population by allowing bee farmers to move their hives next to the site to help pollinate the area and grow healthier bees.

Lake Pulaski Native Landscape
Lake Pulaski Native Plant
Dustin Vanesse from Bare Honey holds up a hive panel covered in honey bees.

Lake Pulaski is not without maintenance needs. The enormity and complexity of the site requires technicians, plant experts, landscapers, and sheep farmers to ensure that the site function as designed. Enel Green Power does most of the technical maintenance, while MNL sprays and maintains the plants. The SolTech trackers require slightly more maintenance than pole trackers, and they can go offline due to storms, sheep knocking the sensors, and other natural causes. Background research is being conducted by ENEL to determine whether the tracking system is worth the extra maintenance. At the end of the site’s service life, which is typically 25 years, the developers hope to decommission the system and return the land to agriculture with richer soil than the gravel alternative and unharmed adjacent landscapes. The research from this site will help quantify the benefits that agrivoltaics can bring to both solar development and agriculture industries.

Watch: Agrivoltaics at Jack’s Solar Garden

Jack’s Solar Garden’s 2022 season caught on film by documentarian Chad Weber of Longmont, Colorado. Hear from our people, see the work that has been done, decide how the future of solar development on America’s farmland.