The system consists of 2,700 PV panels with a string inverter. Womack Electric assembled the array on-shore and deployed it in a shallow area of the lake.

When the fish are biting at Big Muddy Lake in North Carolina, it’s a popular place for recreational anglers. Beginning in 2022, however, fishers, kayakers and elite military trainees began sharing the lake with a 2-acre solar farm on the water’s surface.

The solar array floats on the property of Camp Mackall, a U.S. Army training facility part of Fort Liberty (previously known as Fort Bragg). The photovoltaic (PV) array went live at the end of 2021, generating 1.12 megawatts (MW) of power, which is being fed into a Tesla battery that stores 2 MW. It helps power activities at the base and the nearby community.

The floating array was installed by Womack Electric Co. Inc., Dawsonville, Ga.

To develop the solar farm and its corresponding microgrid power plant, Fort Liberty collaborated with utility company Duke Energy, Charlotte, N.C., and renewable energy firm Ameresco, Framingham, Mass. Womack Electric installed the floating solar system from D3Energy, a Hialeah Gardens, Fla.-based floating solar developer, while it subcontracted for Ameresco on the power plant.

The plant’s Tesla battery energy storage system comes with eight inverters, related switchgear and a 480V to 14.6 kVA transformer. It ties into the power grid with an IntelliRupter fault interrupter to reduce the risk of outages.

Lake-based solar array

Since it was installed, the array has provided carbon-free, on-site supplemental power to the local grid and backup power for Camp Mackall during outages, according to the U.S. Army. It is intended to save energy costs.

Fort Liberty is the largest Army base in terms of population, supporting approximately 140,500 people including active duty and reserve military personnel, their families, civilian employees and contractors, according to the base’s website. It hosts the 18th Airborne Corps, the 82nd Airborne Division and the Army Special Operations Command. The Army was looking for a sustainable source of energy that would benefit the base’s operations and the community while also addressing power reliability problems.

So on Big Muddy Lake at Camp Mackall, the base opted for a solar PV farm that generates the amount of power equivalent to what is needed for 735 homes.

This was Womack Electric’s first solar project. The company is a third-generation, family-owned operation founded by Maurice Womack in 1938. His grandson Todd Womack is the company president and CEO. The EC specializes in power installations for water and wastewater facilities, among other commercial projects. Womack Electric got on-site in spring 2021 to launch both projects at once.

The location was remote and undeveloped. The 15-acre lake features a boat ramp for people coming to fish for bass, catfish, pickerel and sunfish. But that ramp was one of the few structures. The solar array would consume about 2 acres of one side of the lake.

The construction crew installed water access, while Womack Electric installed temporary power, Todd Womack recalled.

He noted that the environment was ideal for solar panels but not the kind used on roofs—there were no standing facilities in the area where rooftop arrays could be deployed. When it came to ground space for solar panels, that would have required cutting down a forested area, which the Army didn’t want to do.

The team built the lake surface system in a shallow area so as to not affect other activities that take place in the lake.

D3Energy delivered the panels and floats, and sent their technicians on-site to support Womack Electric’s installation. The floats are from Houston-­based manufacturer Ciel & Terre.

With the complete array known as Hydrelio, each PV panel must be attached to a float, which snaps to the next with plastic nuts and bolts.

2,700 solar panels

The system consists of 2,700 PV panels with a string inverter. The electricians assembled the array on the shore, and installers cleared part of the bank and built a ramp out of plywood, Womack said.

“We put it together in sections, in four quadrants, one row at a time,” he said. 

The team then pushed out each section and connected it to the next. Each panel is mounted on its own float, and Womack Electric installed additional floats to create a walkway between panels.

The array is anchored to the bottom of the lake at a maximum depth of 15 feet. The work took place over the summer and fall, with the array in place by December 2021, Womack said. The focus throughout the project was on keeping tasks under tight and methodical control.

“The biggest thing[s] for us [were] organization, coordination and quality control. So many pieces had to be managed at once,” he said.

The only issue the crews ran into was underwater, where they had to remove or work around stumps at the bottom of the lake (likely placed there to attract fish).

The finished array also comes with a recloser to respond to events created in the environment, such as impact from a tree limb, so the system can be automatically reset and power restored. The recloser was funded by the Environmental Security Technology Certification Program, which is part of a joint agency consisting of the Department of Defense, Environmental Protection Agency and Department of Energy.

Power plant

Womack Electric’s crew was on-site to connect the array to the new power plant. The plant was built near the lake, from the pad up. Womack Electric installed underground cables between the array and the plant, as well as from the plant to the Duke Energy substation.

The electricians ran a 2,000V DC cable from the array to DC-AC inverters, then 480V to the 480V switchgear. That switchgear then distributed the 480V to a 480 X 12.5-kilovolt transformer, stepping up the voltage into the grid.

“It was running in reverse” from the usual project, Womack added. Instead of pulling power in, the goal was to push power out to the substation so it could be distributed to the Army base or put onto the grid for the community.

For power storage at the plant, Womack Electric installed the Tesla battery energy storage system, which consisted of multiple batteries in a single enclosure weighing about 45,000 pounds and measuring about 25 feet in length. It required two telescopic crawler cranes to offload.

Like most projects during and after the pandemic, the flow of some material was delayed. The switchgear, for example, caused about a three- to four-month delay, Womack said.

For D3Energy, which has floating solar arrays installed around the country, the system was unique in its battery storage and use by a large Army base.

Growing trend in North America

D3Energy has been offering floating solar systems since 2015, said Stetson Tchividjian, the company’s managing director. Today, “We have built and developed the most floating systems in the United States,” he said,

While D3Energy was one of the first players, especially in the United States, floating solar has been deployed in higher volume in Europe, Japan and other parts of Asia. The technology is gaining popularity in North America.

Most installations are intended to help offset power requirements or bring power to relatively remote areas, he said. Locations include everything from water treatment plants to office buildings or government facilities.

While in Asia there are some large sites that generate 100-plus MW of power from floating solar arrays, the focus in the United States has been on smaller, customized sites. However, Tchividjian said the company is in conversations with some large utility players investigating the construction of massive solar farms. 

The snap-in-place, modular makeup means that construction doesn’t typically require heavy machinery.

“We can build these very quickly and very efficiently,” he said, and the benefits are clear for those who don’t have available rooftops or have land dedicated to other purposes.

Tchividjian pointed out that some companies considering solar power worry about the building integrity, insurance concerns or fire hazards with rooftop units. A floating array can be installed in a retention pond behind a building, for instance, that provides the needed space and mitigates their concerns.

Mutual benefits of solar and water

D3Energy asserts that the water keeps solar panels cooler, which ultimately makes them as much as 15% more productive in generating energy. They also gain additional sun rays reflected off the water’s surface.

By not having the panels on land, maintenance will also be easier, Womack said. For instance, land-based systems often experience grass or foliage overgrowth that can shade the panels, which means the installation sites need to be inspected and cleared periodically.

Storing energy at Camp Mackall

When it came to Camp Mackall’s solar farm, D3Energy noted the unique aspect of its battery storage connection. The energy storage capacity will help ensure power reliability at the base, which is necessary for its critical infrastructure.

The life of a floating system is about 25–30 years. While Womack Electric used wet-rated cables, in every other way the system hardware is similar to any solar construction.

“We’ve never been more bullish about floating solar, and we’ve never been busier than we are now,” Tchividjian said.

D3Energy is now working with Womack Electric on similar deployments in the Southeast and elsewhere around the country.

In the meantime, Womack Electric has been on-site at the Camp Mackall array only to provide follow-up maintenance. The electrical contractor is eager to take on similar projects now that it has completed the installation at Big Muddy Lake.

“The biggest thing we were proud of was the organization and quality control we had,” Womack said.

Womack electric Co. Inc.