Coloradans eye floating solar panels to boost water supplies
Colorado River Basin communities, searching for ways to save water in times of drought, are looking to floating solar panels. In Colorado, the solar-powered savings could be big: more than the water used by all of the state’s cities and towns combined.
Reservoirs and canals regularly lose water because of evaporation, which steals about 10% of the overstretched Colorado River’s average streamflow each year. Covering the water bodies nips that evaporative loss in the bud. California, the Gila River Indian Community, and some Colorado towns are experimenting with floating solar panels. At maximum, Colorado could use the arrays to keep 429,000 acre-feet of water from entering the atmosphere — if, and this is a big “if,” the projects can beat environmental, recreational and legal barriers.
“It is a pretty new technology. This is an early look at it,” said Cole Bedford with the Colorado Water Conservation Board, which published a feasibility study on the systems in December. “If this is a route we’re going to go, there’s work to do.”
This Fresh Water News story is a collaboration between The Colorado Sun and Water Education Colorado. It also appears at wateredco.org/fresh-water-news.
Colorado has 1,900 reservoirs that are well-suited for solar array projects, dubbed “floatovoltaics.” The total annual evaporation from these reservoirs is slightly more than 600,000 acre-feet, most of which takes place on reservoirs exposed to hot, dry and windy conditions in the South Platte and Arkansas river basins, according to the state’s feasibility study.
One acre-foot roughly equals the annual water used by two to three households.
Theoretically, if every reservoir that could install solar arrays did so, then water lost to evaporation would drop by up to 407,000 acre-feet, according to the state’s feasibility study. Colorado’s cities and towns use about 380,000 acre-feet of water each year.
The county with the greatest evaporative losses from reservoir sites is Weld County, followed by Larimer, Crowley and Park counties, according to the study.
There are also about 17,000 miles of mainline irrigation canals in Colorado that lose about 90,000 acre-feet of water per year to evaporation. Solar panels on these canals, most of which run through lower elevations and the Eastern Plains, could cut evaporative losses by up to 22,500 acre-feet per year.
“We lose a lot of water to evaporation in the West, but to kind of nail it down in this way … it’s not a small number,” said Bedford, CWCB’s chief operating officer.
Two happy customers in Colorado
In the mountains of north-central Colorado, the town of Walden has about 200 solar panels floating on top of a pond at its drinking water treatment facility.
It was the first floating solar project in Colorado, an experiment to see how the technology performs in climates with extremely cold temperatures. The goal was to provide a reliable power source of 75 kilowatts for the treatment plant in case of an emergency outage on the grid. Wind-power was too expensive to maintain, so the town went with a floating photovoltaic (or “floatovoltaic”) project.
The system, installed in 2018, has been a low-maintenance way to provide certainty around the plant’s power supply, said Mark Russell, Walden’s public works director. It also helped reduce the growth of algae, which would have required more treatment to remove from the drinking water supply.
“If we had the opportunity to do another one, we probably would,” Russell said.
Fort Lupton in Weld County is set to complete its project in 2027, said William Thomas, who works for United Power and is the project manager for the Fort Lupton microgrid project.
“We really want to use this as a blueprint for other communities in our service territory to utilize,” Thomas said.
The project will install 2,000 solar panels on a retaining pond used for emergency water storage in order to produce about 850 kilowatts of energy. With the help of a bank of batteries and other improvements, the project will allow the nearby water treatment facility to supply all of its own power, push extra power back onto the grid, and remain online indefinitely regardless of any sudden emergency outages.
“This is a great land use scenario,” Thomas said. “Instead of taking up valuable land that you might want to build on or that animals might be utilizing, you can stick this in the middle of a reservoir that might be used for other purposes.”
Barriers
Walden, Fort Lupton and the state say the interest is there, but turning the theoretical savings into on-the-ground projects comes with real challenges.
Water bodies need to be near the power grid or some destination that will receive the electricity that’s generated, which limits the number of eligible water bodies. Plus, these projects inherently need support from a lot of organizations, like electric utility companies, reservoir owners, ditch companies and other water managers spread across the state.
For some people, putting solar panel rigs on a reservoir would mar its aesthetic value or limit recreation opportunities. Community support is important to make these projects happen, the state’s study said.
The up-front costs of the emerging technology can be high, and most projects require some sort of government financial aid, the state study said. In Walden, the project’s $400,000 price tag was steep for a town of 600 people.
“There was quite a bit of discussion. I know there were a few letters to the editor saying the town should be spending money on fixing potholes,” Russell said.
A $200,000 state grant — plus knowing the project will pay for itself in 20 years — helped seal the deal, he said.
Generating electricity on top of water could also pose safety concerns even though the closed systems are designed to be around water. While learning how to maintain the system, Russell once went out on the slick floating rig to shovel snow off the solar panels hoping to help them generate electricity. He slipped and knocked a wire as his foot went into the icy pond, he said.
“That’s when we decided maybe it wasn’t a good idea,” he said, adding that he was fine at the time.
The feasibility study also highlighted potential environmental impacts: Covering the surface could change water temperatures, oxygen levels and precipitation patterns, which, in turn, could impact aquatic food webs and fish populations. Birds might try to nest on the panels, which could lead to collision trauma and electrocutions.
And in Colorado, water is closely tied to laws and valuable legal water rights. Water saved from evaporation might not simply belong to the entity that saved it by installing floating solar panels. Depending on the reservoir, it could also be hard to figure out who exactly should own the saved water, the study said.
“I don’t want the takeaway … to be that these are barriers that can’t be overcome,” Bedford said. “The hope there was that these are things that would need to be considered.”