Arizona utilities have long rejected covering canals with solar panels. Here's why that may change

Arizona residents often suggest — to their utilities, the media, their neighbors — that the canals that deliver water from the Salt and Colorado rivers to the big cities ought to get covered with solar panels.

The idea just seems like a natural fit for a place with nearly 300 days a year of sunshine and crisscrossed by wide, uncovered canals carrying precious water that can evaporate under the hot sun.

Utilities have mostly balked at the idea, saying that coverings of any kind on the canals would hinder maintenance on the ditches, and that solar is cheaper and easier to build over solid land. First responders also regularly need to get in those waterways to rescue people and animals.

Salt River Project, which operates most of the canals in metro Phoenix, also has shared concern over installing expensive and potentially dangerous power-generating equipment along canals that are open to the public. Most large solar plants are fenced off.

But the tide might be shifting. The public utility is partnering with Arizona State University to collect data from two sites along its canals to determine how much electricity they might generate and how much evaporation installing solar panels over the water might prevent.

SRP also is considering issuing a request for proposals for a design of how panels might be built over canals.

That would leave it to designers to create something that is safe for the public, cost effective, doesn't interfere with canal work and allows emergency crews access when needed. That likely would mean something high over the entire right of way, but that's yet to be determined.

That design might include panels held by cables, rather than posts in the ground, SRP Director of Water Engineering and Transmission Robert Pane said last week while talking to a group of the utility's board members.

The federal Inflation Reduction Act earmarked money specifically for solar on canals, which doesn't hurt, either.

"We're a perfect candidate for it," Pane said. "We are a water and power utility."

Also of interest to SRP is whether the shade will reduce algae growth in canals as an additional benefit. But Pane said there also is concern the shade could fuel invasive quagga mussels, which can clog water infrastructure.

Once the ASU data is collected and analyzed, and SRP has a design proposal in hand, officials will re-evaluate whether the idea has merit.

"We want a cost-benefit analysis," Pane said.

Why hasn't this happened already?

Pane cited several reasons utilities have dismissed the idea.

One is that building solar panels over canals would require substantially larger structures than the metal posts commonly used to mount solar panels. That will make solar projects built over waterways less cost effective, even taking into consideration the land-cost savings compared with building them over open land.

Pane shared estimates from SRP that indicate the structures to hold solar panels over canals alone would cost more than the photovoltaic solar panels themselves, which is not usually the case when building a solar power plant.

And large solar plants often take advantage of tracking systems that allow the panels to face the sun as it moves across the sky, increasing the amount of electricity they generate to maximize their efficiency.

Pane said the assumption is that solar panels mounted over canals could not use such tracking, which means the system would generate less electricity than a traditional solar plant.

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