Luis Reyes
Oct 23, at 12:30pm ET
Here’s something I didn’t know until I read it this week: the way a California irrigation district gets weeds out of a canal is by dragging a massive anchor chain down the channel. The chain rips the growth loose, the water carries it off, and the district moves on to the next stretch. Low-tech, and apparently it works.
Now picture putting a roof of solar panels over that same canal. The panels shade the water, less of it evaporates, the shade also starves the weeds, and the cool air coming off the water keeps the panels running a bit more efficiently than they would over hot dirt. Everybody wins, right up until somebody has to drag the chain through.
So what do you do with the roof?
The Turlock Irrigation District, which runs 250 miles of canals south of Modesto, has been testing three different answers on its own ditches, and the strangest of the three came in a box from Sydney.
The Australian company behind it, Green Energy Systems, calls the product Solar Waves. In Turlock it’s a single 60-kilowatt array that spans a 21-foot canal and runs about 131 feet along it, according to the company’s own page on the pilot. It was built and wired in a factory, shipped to California already assembled, set down on a rail support built for that one canal, unfolded across the water and plugged in. The company says a small team did the whole deployment on site, and there’s a short video of the array opening up like a paper fan over the channel.
What matters for the chain is what happens in reverse. When the district needs the water, the array gets unplugged, pulled back along its rails and packed together, which clears the canal underneath. Then it goes back out. That’s the entire pitch.
I’ll admit I find that pretty clever. Most solar-over-canal hardware I’ve looked at treats the canal like a roof deck, something you build over once and don’t touch again. This treats it like a garage door.
Solar Power World listed the system on May 1 as a prototype “currently undergoing design field trials,” so this is a test article, not a finished product. And KQED reporters who walked the site on September 4 described accordion-style retractable panels sitting low across the narrow canal, ready to roll up. So the thing is still out there and still being tested.
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That’s what Turlock did with the other two. The fixed canopies at the Project Nexus sites stand well clear of the water on steel, and Weimer told KQED that’s the whole reason they’re up there: the district cleans its canals on a regular basis with equipment, and the panels can’t be in the way. He also said, more or less, that tall isn’t the only way to do it, and pointed out that similar panels in India and Arizona sit low over the water, which leaves little room for the kind of cleaning Turlock does.
So you’ve basically got two choices. Build high and expensive and leave the channel open forever, or build low and cheap and lose access. The folding array is a bet that there’s a third option: build low and get out of the way when asked.
Is that a better bet? Frankly, I don’t know yet, and neither does anyone else. A rail that slides nicely on a demo day is one thing. A rail that’s spent a full Central Valley summer collecting dust, almond pollen and whatever the canal splashes up is another, and I can’t find any published account of the Turlock unit being folded back for an actual cleaning pass. The anchor chain explains why the feature exists. It doesn’t yet prove the feature works at the moment it’s needed.
The economics are the other open question. Green Energy Systems says the Turlock unit was supplied and deployed for less than a conventional ground-mounted solar farm would cost. The company hasn’t put a dollar figure next to that claim, so I’d treat it as marketing until someone with a receipt says otherwise.
Some context, because 60 kilowatts sounds like a lot until you look at the rest of the district. Project Nexus as a whole is a $20 million experiment paid for by the state of California through the Department of Water Resources, and the two fixed canopies together produce a little over 1.6 megawatts. One went up over a 20-foot canal near Ceres in March 2025, the other over a 110-foot canal near Hickman in August 2025, and the narrow site also got 75-kilowatt iron-flow batteries to store what the panels make. We covered the overall project when the state declared it finished back in June.
Weimer called it a “proof of concept” and pointed out that the same district gets 56 megawatts from a regular solar farm in the desert. I read that as a guy being honest about what a pilot is for.
Which means the 60-kilowatt folding array is about 4 percent of a project that’s about 3 percent of one solar farm. Nobody’s lighting a city with it. What the state is paying for is data: how much less water evaporates under the shade, how much less weed growth the district has to deal with, and whether the panels really do run cooler over moving water than over dirt. Roger Bales, the UC Merced professor running the science, told KQED his team has instruments on site measuring temperature, humidity, wind, radiation and evaporation directly. And Weimer said that when the district drained the canal at the end of last season, there was a physical line on the sunny side where the algae stopped at the edge of the shade.
If you’re wondering why cooler panels matter, it’s because photovoltaic cells lose output as they heat up. A canal is basically a long, free heat sink, so the same panel can make a little more power sitting over water than it would over asphalt a few hundred yards away.
A few things are missing from the company’s write-up, and I’d want them before taking the 60-kilowatt number as more than a nameplate. Green Energy Systems hasn’t published a production figure for the Turlock unit, so we don’t know what it actually delivered over a season. It gives a weight and panel count only for its standard 50-kilowatt product, which is a different configuration. And the district’s own project page leaves the retractable unit out entirely, so I can’t tell you exactly when it was installed, only that it’s been in field trials since at least the spring.
That’s not unusual for a prototype. It just means you should read “60 kilowatts” as a label, not a result.
Irrigation districts across the West are quietly working out the same problem from different directions. Arizona’s Gila River Indian Community went with fixed trusses that never touch the water. A Spanish olive oil bottler solved the same kind of conflict by raising its panels 13 feet so the harvester could drive under them. Turlock is the only one I’ve seen that decided the panels should move instead of the machine.
Whether the state builds more depends on a report that hasn’t landed yet. Andrew Schwarz, a spokesperson for the California Department of Water Resources, told KQED in a story updated September 28 that the agency is waiting on UC Merced’s final findings before deciding whether to fund another canal, and that report is due later this year.
Don’t bite your tongue. Speak up.
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