Buoyant racking turns water into an ideal solar site

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Floating solar projects are scaling up in the United States, and while the technology is still emerging here, it’s not necessarily in uncharted waters. , reaching nearly 100 MW, using blow-molded plastic floats as racking, moorings adopted from the existing marine industry, and anchors similar to those found in ground-mounted solar projects.

Although U.S. installation requirements differ from international regulations, the structural components that hold the panels in place are the same and have been tested to withstand the elements of these marine environments. Provides advantages for deployed solar arrays, such as temperature control.

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“When the panels are cooler, they operate more efficiently, so they can produce more.” Ciel & Tail“The water manager [floating solar arrays] Blocking light prevents algae from growing and evaporates from the body of water. In places like California, Texas, and the Southwest, which suffer from constant drought, water is at a premium, so capping open reservoirs doubles the benefits there. “

International floating solar component manufacturer Ciel & Terre compares these aquatic array layouts to commercial rooftop projects. However, the installation process is unlike any other in the industry.

Securing islands of solar panels

Floating solar projects are usually installed in man-made water bodies such as water treatment plants, hydroelectric dams, quarries, and reservoirs. The first step in installation is securing the anchors and mooring lines that attach to the floating solar array.

Moorings are guided to shore or submerged to the bottom of the body of water. The choice depends on the location of the array and the circumference and depth of the water. If the water is too deep, it can be moored to the shoreline. If it is shallower and the project owner prefers to place the array further offshore, moorings can be attached to underwater anchors. Alternatively, arrays can be used with a combination of both underwater and shoreline anchorages.

Similar to ground-mounted and possibly commercial rooftop solar, floating projects can use penetrating or ballasted anchors. The choice of anchoring is often made by the permitting agency for a particular project. Contaminated soil and overlying liners may prevent penetration of the lake bed, in which case weighted ballast is used. Otherwise, penetration anchors such as ground screws or helix piles work well.

“The anchors themselves are the same ones that are used for other types of fixed-to-the-ground applications, like cell towers and antennas,” Bartle said.

Floating solar power projects are usually installed in man-made water bodies such as water treatment plants and quarries.return

Working on water is new territory for solar contractors, so you’ll need to hire an OSHA-certified captain and either a diver or drilling rig to install and inspect your anchors.

Unlike land-based solar arrays, floating project mooring lines must incorporate elasticity or slack to anticipate water movement. Anchors and moorings are there to keep the array in place, but the water is always in motion. Water bodies fed by rivers have currents, winds cause waves, water levels rise and fall due to evaporation and precipitation, dammed reservoirs can drain or fill, and water can freeze and thaw.

“In some cases, for a hydro dam, it can go up and down 100 feet, so you need a pretty complex anchor assembly to accommodate that,” says Bartle.

Mooring line functionality varies by manufacturer. Ciel & Terre manufactures bespoke moorings and shore-mounted parabolas to suit project needs. Seaflex is an international mooring manufacturer that has been serving the marina industry for 40 years. Their moorings use elastic rubber that stretches up to 30 feet and stays taut when not stretched.

Once the anchor is set, a buoy is attached to the end of the mooring line and waits for the floating group of solar panels.

“It’s a combination of water body owners, EPC contractors and anchors. [subcontractor]the owner of the electrical system, and we will determine the best anchors,” Bartle said.

Assembling the island

Rows of floating panels are assembled onshore after anchors and mooring lines are installed. Hollow floats are connected in series, with secondary floats between each row of panels acting as passageways for maintenance access.

“We assemble the panels to the racking, the racking to the floats, and the floats to each other all on land,” says Bartle.

He likens the process to building something out of Lego or Erector sets. The Ciel & Terre floating solar platform is constructed from high-density polyethylene and manufactured using blow molding, the same process that makes food and beverage containers. Kayaks, buoys and marina docks are also made of the same plastic.

“It’s not a new material, it’s a new use for the material,” says Bartle. “But the product can exist in both cold and hot temperatures, so it can expand and contract without failure.”

Ciel & Terre’s Hydrelio floating solar line includes air 1280 floats. One solar panel is mounted per float at either a 5 degree or 12 degree tilt. While previous models had a built-in tilt, the aiR uses metal brackets and rails to change the angle of the panel. Ciel & Terre floats can be assembled in single or double row configurations, including east-west orientation, depending on wind loads.

Sections of floating solar projects are assembled on shore, dropped into the water, and towed to moorings by boat.return

Especially if the coastline is steep, a ramp should be built to guide the float to the surface. Once the float blocks are assembled, they are launched into the water and tethered to the boat. The blocks are then pulled and attached to the mooring lines and the process is repeated until the entire array is assembled.

“There are other safety and regulatory factors that ground installations and rooftops don’t often have. You can walk to work,” he says. return“It’s a little different here. We try to do as much work on land as possible. We try to minimize work on the water.”

RETTEW, an engineering firm that has designed and built three floating solar projects on the East Coast, recently completed construction of a nearly 9 MW floating solar system in Milburn, New Jersey.First floating solar project Thayerville is 4.4 MW, and Wert said RETTEW is already making preliminary plans for a system about ten times that size.

Floating solar in the US is on the rise, but its price is still not competitive with other rack solutions on the market. Ciel & Terre’s Bartle estimates that floating solar projects cost 10 to 15 percent more than ground-mounted systems of similar size.

“The reality is that it’s more expensive than a ground installation. If you’re doing large-scale solar, you can’t beat a single-axis tracker on a Midwestern farm,” says Wert. “We think floating solar is a very good application anywhere. [ground-mounted is] Not the right technique. “

Extra services such as hiring a boat captain or diver add to the cost of the project, and solar floats take up more space than other styles of racking during transportation, so costs also increase.

However, for customers who do not have sufficient rooftop or land space, floating solar has its own value.NREL research from 2018 claims that more than 24,000 water bodies in the United States are suitable for floating solar projects, and that 27% of those sites could provide 10% of the nation’s electricity.

While it may not be the first choice for every project, there are some applications where floating solar is the best option.

“What I am telling EPC is to look at floating solar as another tool in our toolbox to provide renewable energy to our customers,” said Bartle. “We’re not trying to take market share from other solar products. This is just a complementary product line that the developer and his EPC are excited about. It’s a new frontier.”

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