You may have seen China’s massive solar array floating on the surface of a flooded coal mine in Huainan. Stretching beyond the size of 160 American football fields, it’s a striking sight. Floating solar arrays have also made countries like Japan, Brazil, and Korea their home. Now, projects like this are finally making their way to the U.S.

Most recently, the French company Ciel & Terre recently unveiled a new 252 kW floating solar array in Kelseyville, California. The 720-panel array floats atop a wastewater treatment pond. If successful in producing the expected 415 kilowatt hours in its first year online, it will be the first of many floating arrays in the county as California treks toward its promise to produce only carbon-free electricity by 2045.

Floating solar array in Kelseyville, Califronia from Ciel & Terre
Floating solar panel array recently unveiled in Kelseyville, California

The field of floating solar arrays — aka “floatovoltaics” — stems from the problem that accompanies owning anything: where are you going to put it?

If you want to build solar arrays, you need a place to build them. Not everyone has the sheer roof mileage available to build a system like Tesla’s gigafactory. Let’s not get started on the space required for wind farms. So companies like Ciel & Terre turned to water. It’s a fast-growing industry, predicted to value $584.27 million by 2024.

(Wait. Should we put wind farms on the water too?)

Floatovoltaics array on Yamakura Dam in Japan
Floating solar array located on Yamakura Dam in Japan.

“You don’t think about how much water surface area there is until you look for it,” Chris Bartle, Business Development Manager of Ciel & Terre, tells Inverse. Instead of looking at limited square footage on a roof, he explains, you’re looking at whole acres on water. It takes roughly 3 acres of water surface to generate 1 MW.

The prospect of saving land appeals to businesses as well. For example, a winery would probably rather fill their precious land to the brim with grapes, rather than solar panels.

How Do Floating Arrays Affect the Environment?

It’s still too early to understand long-term effects of floatovoltaics. But so far, the early results are promising. Since the arrays block sunlight from the underlying water, the system slows algae production and evaporation, an important bonus for states concerned about water conversation.

There are still drawbacks. Although the solar panels have proved durable so far, areas with colder climates like Sweden and Minnesota are concerned about how they’ll fare in colder, icier waters. Researchers continue to investigate whether systems that freeze and melt repeatedly across seasons would experience damage.

What’s Involved in Installation?

The cost between a ground installation and a floating installation are comparable, according to Ciel & Terre. Floating installations actually require less heavy equipment, as large ground installations may involve steps like clearing trees.

The floating arrays are made from High Density Poly Ethylene (HDPE) plastic, and use the exact same panels as ground installations and are expected to last over 20 years. To expand in the US market, companies like Ciel & Terre also focus on man-made reservoirs like Kelseyville’s waste management pond, since they often come with fewer regulations.

Upcoming projects include a 4.4 mW installation in New Jersey — which would be the largest in the US to date — and a 1.8 MW setup in California next month.

California winery's flotovoltaics installation
Far Niente, a Napa Valley winery, installed a flotovoltaics system from the company Sharp that set the winery's energy bill to net zero. 

“It’s a hot niche inside a maturing solar industry,” says Bartle.

Correction: A previous version of the story re-printed an erroneous figure from the original press release. It has been updated with additional comment from the study’s author.