Arizona Tribes Explore The Benefits Of Floating Solar

The American Southwest relies on water from the Colorado River for domestic use, irrigation of croplands, and commercial activities. The problem is, there is not enough water to meet the needs of everyone. Las Vegas would wither without it, Los Angeles would need to turn to desalinization to meet its water needs, and greater Phoenix would be unable to sustain its expansion into the surrounding desert without water from the Colorado. Floating solar could help conserve water and supply clean, zero-emissions energy to local communities.

30 miles south of Phoenix, members of the Akimel O’otham and Pee Posh tribes — known collectively as the Gila River Indian Community — installed floating solar panels last November over one of those canals that flows through their property — the first such installation in the US. Moving the water through the canal and the local irrigation system requires a lot of electrical energy. The tribal community expects much of that power to come from the floating solar installation.

Not everyone is a fan of floating solar, however. Various people worry that, by reducing the amount of sunlight that penetrates below the surface of bodies of water, marine life may be harmed. People who fish, water ski, kayak, use stand-up paddleboards, and swim worry the recreational uses of a body of fresh water might be limited by the floating solar panels.

Floating Solar In The Colorado River Basin

Unlike most Americans, who rarely give a thought to where there fresh water comes from, Indigenous  people tend to be keenly aware of the important role access to clean water plays in the health and sustainability of their communities. In addition to making clean energy, floating solar also can reduce the amount of evaporation from lakes and canal. If the technology were expanded to more parts of the Colorado River basin, the amount of water available to the 40 million people who depend on the river could be increased significantly.

At the present time, negotiations are taking place about how to apportion the water in the Colorado River among the various stakeholders. Included in those discussions are the Upper Basin states of Colorado, New Mexico, Utah and Wyoming, the Lower Basin states of Arizona, California and Nevada, various Indigenous communities, and Mexico. Almost all of them will experience reductions in their allotments.

And yet, the idea of using floating solar has not gained traction with the multiple authorities responsible for managing the Colorado River watershed. When Jake Bolster of Inside Climate News contacted Western water managers recently, some said they were open to learning more about floating solar but none knew of any plans to employ the technology other than the Gila River project. A few pointed out that floating solar would be too costly because of the unusual construction methods needed and because the potential water savings would be too small to justify the added costs.

This may strike some as silly. Here is a tactic that can conserve water in an area where demand far exceeds supply, and yet fear of the unknown is stopping those responsible for managing the water shortage from considering a technology that would conserve it. The Colorado River also powers massive hydro power installations at Lake Mead and Lake Powell, both of which are experiencing critically low water levels. By generating electricity, floating solar could take pressure off the hydro stations at both locations and allow the water level in the lakes to rise so more hydro power would be available when needed.

“People in the US don’t know about [floating solar] yet,” Scott Young, a former policy analyst in the Nevada state legislature’s counsel bureau told Bolster. “They’re not willing to look at it and try and factor it” into the negotiations. Prateek Joshi, a research engineer at the National Renewable Energy Lab who has studied floating solar, told Bolster,  “Even though [floating solar] may play a smaller role, I think it’s a critical role in just diversifying our energy mix and also reducing the burden of land use.”.

Floating Solar On Federal Waters

In February, NREL published a study that found floating solar on reservoirs located behind federally owned dams could provide enough electricity to power 100 million US homes if all the available space on each reservoir is used, which is not  likely to happen. However, if only 23 percent of the surface area of Lake Powell was covered with solar panels, it could generate 15 GW of electricity. 28 percent of the surface area of Lake Mead would yield another 17 MW.

Combined, that is equivalent to the output of 32 new thermal power plants. “There’s a lot of power you could get from a relatively small percentage of these Colorado Basin reservoirs,” Joshi said. He added that he has spoken with developers and water managers about floating solar and there is “an eagerness to get this [technology] going.”

There are downsides to floating solar, however. It can cost about 20 percent more that ground mounted solar. The cooling from the water beneath the panels improves solar panel efficiency but because they are not tilted toward the sun, they produce somewhat less electricity than an equivalent solar array on the land. It also increases greenhouse gas emissions if the panels cover more than 70 percent of the surface area of a body if water, according to a study published in January by researchers at Cornell.

The Bureau of Reclamation “has not received any formal proposals for floating solar on its reservoirs,” an agency spokesperson, who added that the Bureau has been monitoring the technology. In a 2021 paper published together with NREL, the Bureau of Reclamation water managers “should be wary of contractors’ claims of evaporation savings” without site-specific studies. Nevertheless, that  report found the Colorado River has plenty of floating solar potential — more than any other basin in the West.

Colorado Studies Floating Solar

In 2023, Colorado passed a legislation that required several agencies to study the use of floating solar. Last December, the Colorado Water Conservation Board published its findings, which estimated that the state could save up to 407,000 acre feet of water by deploying floating solar on certain reservoirs. An acre foot covers one acre with a foot of water, or 325,851 gallons. I would do the math but readers know my difficulties with numbers, so I leave it to you to make the computation. Suffice to say, it’s a lot of water

But the extra costs of building solar panels on water instead of on land has discouraged Denver Water, Colorado’s largest water utility, from considering floating solar. “[It] doesn’t pencil out for us for many reasons,” Todd Hartman, a company spokesperson, told Bolster. “Were we to add more solar resources –which we are considering — we have abundant land-based options.”

The West Side Reservoir Project

Now that the Gila River installation is complete, the tribes are working on a second floating solar project that will cover about 60 percent of the West Side Reservoir with floating solar. That project is scheduled to be completed by July. “Do we know for a fact that this is going to be 100 percent effective and foolproof? No,” David DeJong, the GRIC project director for its irrigation district, told Bolster. “But we’re not going to know until we try.” That body of water is well suited to solar  because it will not be open to recreation.

But part of the money to pay fore the project is scheduled to come from the grants provided by the Inflation Reduction Act. The failed US administration is openly hostile to renewable energy of any kind. At the moment, Inside Climate News says, it is “unclear whether or to what extent the Bureau of Reclamation has slashed its grant programs.”

“Under President Donald J. Trump’s leadership, the Department is working to cut bureaucratic waste and ensure taxpayer dollars are spent efficiently,” said a spokesperson for the Department of the Interior, which includes the Bureau of Reclamation. “This includes ensuring Bureau of Reclamation projects that use funds from the Infrastructure Investments and Jobs Act and the Inflation Reduction Act align with administration priorities. Projects are being individually assessed by period of performance, criticality, and other criteria. Projects have been approved for obligation under this process so that critical work can continue.”

In addition, the government’s yoyo tariff policies involving solar panels could lead to cost increases the community cannot afford. If the West Side Reservoir is completed, it will be part of a larger system that the community hopes will offset all the electrical demand and carbon footprint of its irrigation system.

:The community, they love these types of innovative projects. I love these innovative projects,” said GRIC Governor Stephen Roe Lewis. “I know for a fact this is inspiring a whole new generation of water protectors—those that want to come back and they want to go into this cutting-edge technology. I couldn’t be more proud of our team for getting this done.”

The West Side Reservoir system is visible to drivers on Interstate 10, which is deliberate. The tribes want to advertise the fact that they are addressing water conservation and sustainable energy practices. “It could be a paradigm shift in the Western United States,” DeJong said. “We recognize all of the projects we’re doing are pilot projects. None of them are large scale. But it’s the beginning.”