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Dual-purpose solar

A new solar power project built over a cranberry bog in Massachusetts is demonstrating how agriculture and solar power can work hand in hand.

By Diane Mettler

Some argue that solar power projects are the enemy of agriculture, and that constructing solar facilities on fields and pastures takes farmland out of use for decades.

There is one simple solution—build the solar facilities above the farmland, keeping the ground below in use.

One such project is in Carver, Massachusetts, where a 1.1-MW solar field, co-owned by Lodestar Energy LLC and Conergy and constructed by S&C Electric Company, was built over a cranberry bog. The shade from the panels actually provides the ideal growing environment for the cranberries below.

"It's such a unique and great project. We think it's a great future for solar in that it has a dual use," says Jeffrey Macel, co-owner of Lodestar. "It's difficult to find sites that people are comfortable dedicating to solar, and when you can have an underlying use that you keep in place, that's really the holy grail of the highest and best use for land."

Jaime Smith, co-owner of Lodestar, says the company stepped in when the original developer had gotten the site under control but hit a roadblock when it came to the regulations surrounding this type of project. "It's not uncommon for this to happen," explains Smith. "A developer goes out, has a concept, gets a number of pieces of the puzzle in place, and then needs some help to get it completed. We've partnered with several of those in the past to help finish the development, finish the financing, and take it across the goal line.

"We hope that it's a model we can continue to deploy," Smith added. "I can name a couple of other [dual] projects, but this is the largest of its kind."

Lodestar worked with the town of Carver and the Department of Environmental Protection to get the go-ahead for the solar project.

As they have many times in the past, Lodestar looked to S&C to construct the solar facility.

"They're a fantastic group," says Macel. "They are an electrical switch-gear and component manufacturer and one of the largest manufacturers in Chicago. They're employee-owned, and we think it's a great model to work with companies that manufacture here in the U.S. and have a great presence.


"They also have a deep knowledge of the electrical industry and project development. And for a development group like us that's small, nimble, and adaptive, it's nice to have a big partner like S&C who has 100 years of experience in this market. They really bring a depth of knowledge and experience."

With contracts signed and everyone ready to move forward, it was the cranberry bog that determined the construction calendar for the project. S&C began construction in the winter, and the facility was fully operational in late-June 2016.

Unlike the highly elevated panels needed on projects where animals graze underneath, the panels for the Carver project only had to be elevated slightly higher than normal. The panels are fixed tilt on post-driven foundations, and the bottom edge is about three to four feet high, with the top edge at seven or eight feet.

One of the challenges of designing the project was flooding, which is characteristic of all cranberry bogs.

"All of the equipment had to be located where it would not be in a flood zone or in an area that would be flooded," says Daniel Girard, director of Engineering, Procurement, and Construction (EPC) at S&C.

"At the same time, when we ran our AC and DC cables for panels, we ran them on the top edge of the panels, taking into account that the cranberry stock was going to be there. We didn't want to dig through the stock and do any damage."

Another unique aspect of the project was the added requirement for the land. S&C laid down protective sheets so that the track machines that drove the posts would not disturb the cranberry vines. S&C also had to accommodate Mother Nature's schedule to ensure that it finished by a certain time of the year.

"You learn about these things as you go," says Girard. "Cranberry vines become more rigid later in the summer. If you wait until July, they become much more breakable, and they're softer and more flexible earlier in the year. Because of that, we got our post driving done earlier in the year."

 The 1.1-MW solar field, co-owned by Lodestar Energy LLC and Conergy and constructed by S&C Electric Company, was built directly over the cranberry bog. The shade from the panels actually provides an ideal growing environment for the cranberries below.

S&C supplied both AC and DC engineering as well as its Vista Under-ground Distribution Switchgear unitsand interconnectivity to local utilities National Grid and Eversource.

The switcgear provides switching and protection through 38 kV, designed to minimize the interconnection costs of a solar farm.

For this project S&C also used Astroenergy 310 and 315, 72-cell fixed solar panels and Solectria string inverters. S&C turned to RBI Solar Inc. for the racking system and used local construction crews with whom they've worked in that area—Skyline Solar LLC and Pastore Excavations Inc. "Normally when we do construction, we always team with one of the local electrical contractors to do the buildout and civil construction," says Girard.

One piece of technology that stood out in the Carver Project was the string inverters. "We're seeing a lot of people go away from central inverters and moving to string inverters," says Girard. "They are much smaller inverters—like 40 kW. The advantage is by having a lot of smaller inverters, if you have a maintenance issue, you lose a much smaller portion of the DC grid and that way maintain more up and running."

Girard says for years people have avoided string inverters because of the extra cost. "Now we're starting to see string inverters' prices come down closer to what central inverters are, which is driving a lot of adoption across the market."

Unlike the highly elevated panels needed on projects on agricultural land where animals graze underneath, the panels for the Carver cranberry bog project only had to be elevated slightly higher than normal. 

Macel agrees with the benefit of string inverters from a maintenance aspect and adds, "String inverters allow for additional shading, and it doesn't affect the production of such a large portion of your facility when you've got shading. We've moved to them almost exclusively. And Solectria is a Massachusetts company and are probably one of the better known string inverters."

Inverters aren't the only new trend happening in the industry. Girard says there are lots of subtle changes going on in solar technology. "The panel size continues to get bigger, which is good, because you get more watts per square foot. We've seen the efficiencies of the panels go up."

Will we see more dual-use facilities like Carver? Girard hopes so. But for companies considering dual-use, there are some important considerations. "You've got to ensure you have a clear path for the electrical system to come in and work out the logistics of how you're going to build the system," says Girard.

"In fact, they may want to review it with somebody like S&C early on and ask, 'What do you think about this?'" he adds. Companies, he says, need to take into consideration not only what's going to happen at the site after construction is finished, but what the company building the facility can do.

"You've got to work together," says Girard. "Of course, you've also got to work with the local folks because there are things such as fire lanes and the like, that the community wants. It becomes basically the three of us having a conversation and a lot of cooperation."

Although these types of dual-use projects take additional communication and some homework upfront, Macel is hopeful his company will be part of more such projects in the future. "We look at the future of energy as developing a clean energy project in a way that's harmonious with existing use, and that's helpful. When we can use farm fields and get the benefits of both the farming and solar, we think it's a win-win."

It's a good time for solar, especially in Massachusetts, says Girard. "This is the fifth project we have developed in Massachusetts with Lodestar, bringing nearly 12 MW of solar to the state.

"The Commonwealth of Massachusetts has some of the most progressive renewable energy policies on the books," he added. "They've set a very forward-thinking solar energy goal for 2020, and every project we do here helps them get closer to that number." Massachusetts has set a target of 1600 MW of solar power installed by 2020.

"Solar energy isn't just for Massachusetts, though," says Girard. "I think when you really look at it, solar has hit parity with natural gas. If PV continues to go down in price, I think you're going to see solar quite prevalent both in Massachusetts and throughout the industry for years."