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Harvesting solar power—and blueberries

Power producer Navisun is looking at the agrivoltaics niche—including building a pilot solar project on a blueberry farm in Maine—to expand its solar power portfolio.

By Tony Kryzanowski

The National Renewable Energy Laboratory (NREL) estimates that by 2030, utility-scale solar farms could cover almost two million acres of land in the United States, some inevitably taking cropland out of production which is a public concern.

But can solar farms and crops co-exist on the same land base in some instances—and both benefit from this co-existence?

Agrivoltaics allows crop and solar power production to co-exist on the same land parcel and could contribute significantly to helping the U.S. meet its renewable targets.

According to an Oregon State University study, converting just one percent of American farmland to agrivoltaics could not only meet U.S. renewable energy targets, but could also save water and create a sustainable, long-term food system.

What has both the renewable energy industry and farmers intrigued about agrivoltaics is the potential to sometimes increase crop production when a solar array co-occupies a site.

On one research site in Colorado managed by NREL, where solar panels were situated over crops such as tomatoes, blackberries and herbs, cooler, more humid microclimates were created, where soil beneath the panels retained moisture longer and vegetation used water more efficiently. In some instances, a 70 percent increase in crop production was reported.

If agrivoltaics proves viable, it could open up new space for solar developers, especially in areas with high volumes of productive farmland and few other land base alternatives.

A pilot project was recently completed on a 10-acre wild blueberry farm in New England, where a 4.2 megawatt (MW) solar array was installed on the same land base of a long-standing wild blueberry operation near the town of Rockport. Maine. This was a first-of-its-kind project installed in the state and is garnering significant recognition.

The pilot agrivoltaics/solar project was recently named a Construction Project of the Year Finalist in the 2021 S&P Global Platts Global Energy Awards.

If agrivoltaics involving blueberries proves viable in Maine, this has national implications as 38 U.S. states currently grow blueberries, representing a $4.7 billion industry annually. Wild blueberries contribute $250 million annually to the State of Maine’s economy, alone.

Originally developed by BlueWave Solar and now owned by independent solar power producer, Navisun LLC, the Rockport Maces Pond agrivoltaics pilot project was installed in conjunction with researchers at the University of Maine Cooperative Extension. The power produced from the site is wheeled through the local distribution level power grid and monetized through several net metering sales agreements.

Navisun has been actively involved in Maine for a couple of years and is benefitting from the state’s net metering credit program. There were no financial incentives offered to construct the blueberry pilot project at Rockport.

Realizing the size of the wild blueberry industry in Maine, the goal of the pilot project was to analyze the viability of incorporating solar farms with existing blueberry farms without doing irreversible damage, as well as developing various potential solar farm designs and construction techniques to minimize damage.

Stephen Campbell, Managing Director at Navisun, was actively involved in overseeing the construction and start-up of the Rockport project. The Massachusetts-based company purchased the project after all the permitting had been arranged by BlueWave Solar.

 The location for the recently completed pilot project was a 10-acre farm near the town of Rockport, Maine, where a 4.2 megawatt solar array was installed on the same land base of a longstanding wild blueberry operation.

"We are long term renewable energy owner operators and we take our task of being environmental stewards really to heart when we try to do these projects," he says. "We’re always looking for interesting angles to give back to environmental stewardship by doing projects where, for example, there are pollinator plantings beneath the array."

He adds that the concept of agrivoltaics is a new and expanding niche within solar development and that Navisun has a number of these types of projects in the works in Maine.

"This is a way—from a solar perspective—where because solar needs to be spread out a little bit, you can achieve a dual use where you can still utilize the underlying productive farm and gain the benefit of putting the solar farm in. It’s a win-win for both the company and the farm," Campbell says.

The site is owned by David Dickey, who receives an annual lease payment from Navisun while also continuing to harvest the valuable wild blueberry crop beneath the solar array, creating a new income source for the landowner.

The pilot project has those involved from the university excited about its potential.

"The potential for this project to pave the way to providing farmers with alternative income streams while still producing the iconic Maine wild blueberry is exciting and we’re thrilled to be part of it," says Dr. Lily Calderwood, University of Maine Extension Wild Blueberry Specialist.

The project was delivered on time and on budget by engineering, procurement and construction (EPC) firm, CS Energy, and it began production at the end of 2021.

"We have a great relationship with CS Energy and we are doing a whole bunch of projects with them," says Campbell. "Their pre-construction team has always been phenomenal. They were able to sit with us early, understand what the different hurdles were, and help us come up with solutions and a really detailed plan of how we were going to do things. They and their sub-contractors bought in, and that was one of the keys to making it a great project."

The project consists of a combination of mono solar modules provided by Hanwha and bi-facial solar modules provided by Jinko Solar to allow Navisun to achieve the power production it requires. They have witnessed some additional production from the bifacial modules, primarily from snow ground cover reflection in winter. The inverters and transformer were provided by TMEIC.

Remarkably, blueberry production increased the first season after construction—more than anticipated despite being disturbed—leaving everyone scratching their heads, and demonstrating the need for continuing research.

"Now they are trying to figure out, why was that," says Campbell. "Was the shade helpful in a way that it was capturing heat? What was the moisture content? It’s a long term play here to try to figure that out and at the same time replicate it so that we can do it at other locations."

Maine blueberry farmer Paul Sweetland (inset photo, above). The Maine solar project was originally developed by BlueWave Solar and is now owned by independent solar power producer, Navisun LLC. The pilot project was installed in conjunction with researchers at the University of Maine Cooperative Extension. 

The point of the pilot project was not only to investigate if solar farm infrastructure and crops could co-exist on the same land base, but it was also a teachable moment for industry to investigate various approaches that maximize production efficiency of the array without impacting the cash crop.

According to Lisa DeMarco, principal consultant and founder of Climate Tech Marketing, portions of the site were divided into three distinct areas to test varying tiers of defined construction procedures, to determine the effects of each approach. Each required vastly differing labor requirements and construction costs. CS Energy, Navisun and BlueWave, together with the University of Maine, developed and implemented individual construction plans for each of the control areas.

Because there was an existing blueberry crop on the property, potential crop damage during construction was identified as a concern. So in the most cautious construction control area of the three being studied, the focus was on methods to limit crop damage. CS Energy invested in nylon landscaping mats to cover the plants and ensured that all staff exclusively walked on the mats. The mats were regularly rotated to not disproportionately impact certain parts of this control area and to allow machines to access necessary locations.

In the moderately cautious construction area, only tracked equipment could be used, and motion was restricted to prevent blueberry damage.

The third construction area featured conventional solar array construction with no special consideration for the blueberry bushes.

The university is monitoring soil quality and moisture, in addition to crop production, in each of the three defined construction areas. Their goal is to create a new playbook for blueberry farmers wanting to maintain their farms as well as host new solar farms. Overall impact is still being reviewed but researchers have reported that the blueberries are recovering better than expected where panels were installed with the most precautions.

Since agrivoltaics is site-specific, developers must plan for construction on whatever site conditions are present and the Rockport Maces Pond site was no exception.

The site was located on the south side of a small mountainous area and the sub-layer was almost all ledge. This required CS Energy to conduct a significant amount of rock drilling to install the racking system. Both the rock drilling equipment and the fixed-tilt racking system was provided by TerraSmart. Track- mounted construction equipment was deployed to install screws in the ledge for the racking system, with the goal of preventing harm to the blueberries.

Another consideration in the various solar array designs was how to harvest the blueberry crop in the presence of the solar racking system. The racking system was designed with fewer leg supports with the bottom drip edge on the solar panels sitting 60" above the ground. This takes both crop harvesting and the amount of snowfall that Maine can get into consideration.

On the five-acre careful construction sites, the berries were harvested using a specially-designed, all-terrain vehicle (ATV) pulling harvesting equipment. On the conventional construction parcel, the racking system was designed and installed so that the berries may be hand-picked.

Navisun is excited about the agrivoltaic opportunity in solar power development and believes it has a lot of industry potential because of the dual benefit it provides.

"We have to start thinking about how we get to the capacity that we need to get to as a country, but doing it in a way that we are not taking farmland or pure forested land out of production," says Campbell. "There have to be other ways to do this. I think that agrivoltaics is a great angle for the industry moving forward."

Q3 2022