What California is learning from solar panels built over irrigation canals

What California is learning from solar panels built over irrigation canals kqed.org

California solar panels tower over canals in Turlock, proving to save water, produce clean energy and improve local water quality.

371 points•Jtsummers•9 days ago•742 comments•

#california #solar #panels #canals #solar panels #irrigation #irrigation canals #panels built

742 comments

nbf_19958 days ago

It seems like it would be more effective to simply put all the solar panels in a field, and construct a cheap shade over the entire canal no? The supports in the picture are massive and don't look cheap. Also I would imagine the solar array uses more copper than a similar capacity array just built in a field. You can't daisy chain multiple miles of solar panels together, so you need an extra power line to run alongside the whole thing.

Put the solar panels in a field: The solar array uses less copper. The shade supports don't have to hold up solar panels: Shade supports cost less.

The best reasoning they give is that California has insane permitting requirements, and it takes 1/6 the time to build on developed land compared to undeveloped land.

schnevets8 days ago

Anecdotally speaking, I have heard of a massive California solar farm in an undeveloped area that has serious vandalism problems. Junkies will find ways through the fencing at night, strip copper and other materials from panels, and cause thousands in damages and lost energy just to extract enough scrap for a fix.

Nothing short of a face-to-face security response will deter these criminals, so there it is a challenging cost-benefit balance. At least panels in parking lots and other developed spaces have the benefit of witnesses. I'm sure a 20 foot climb up a steel beam over running water is a decent deterrent as well.

swiftcoder8 days ago

> Junkies will find ways through the fencing at night, strip copper and other materials from panels, and cause thousands in damages and lost energy just to extract enough scrap for a fix

I live in a European country, where the phone company hasn't bothered to come remove the old unused copper phone lines in the last 5 years. Thousands of dollars worth of cables running past my house alone, and no one has bothered to go strip it in the night and sell it

This feels like one of those USA problems that would be better addressed by funding decent social services (free healthcare, cheap housing, addiction treatment programs, etc).

yongjik8 days ago

A few years ago, some foreigners entered a subway depot in South Korea, drew graffiti, and left the country before they were caught.

South Korea put a notice on them on Interpol. At least one was arrested (at an airport in Romania), though I couldn't find any follow-up article on what happened to him. I hope he got to tour the inside of a South Korean jail.

A society should be willing to put resources to protect is public infrastructure. In the long run, it will also be cheaper than fixing the same thing a hundred times, everyone enjoying second-grade service, or both.

happyopossum8 days ago

> Anecdotally speaking

First hand experience here - worked with a non-profit that has a tiny solar and battery installation for a light display, and we have had constant theft and vandalism problems with it. It's not even easy to get to - those meth-heads had to work to steal the lead acid batteries and copper wire...

justinator8 days ago

>Nothing short of a face-to-face security response will deter these criminals

Is this one of those, "US only First World country that has this sort of problem" problems?

I can only imagine why?

euroderf8 days ago

Stripping out copper... the USA has joined the ranks of post-Soviet Europe, where such thefts are (or have been at some point) routine. Infra-harvesting.

burnte8 days ago

> It seems like it would be more effective to simply put all the solar panels in a field, and construct a cheap shade over the entire canal no?

No because now you're using land that could be used for other things, which is exactly what this avoids. This takes existing land that loses water and costs money, and makes it lose less water and make money.

skybrian8 days ago

That’s true of everything you build. The cost of land has to be taken into account, but land is much cheaper in some areas than others.

ck458 days ago

The concept of https://en.wikipedia.org/wiki/Agrivoltaics still sounds more promising than putting solar panels on top of the canal.

dietr1ch8 days ago

You are assuming that land is expensive and forgetting that building and maintaining panels over long a canal is harder than building over a large plot.

onlyrealcuzzo8 days ago

You're also not getting the free cooling capacity of the water which makes the panels more efficient - though that probably only drops the total cost 5% or so, but how much extra the heavier supports cost may not be much more...

suncemoje8 days ago

In Switzerland, which is quite densely populated, they even have a pilot project with putting solar panels between rail road tracks:

https://www.swissinfo.ch/eng/emissions-reduction/solar-energ...

brudgers8 days ago

The supports in the picture are massive and don't look cheap.

They look like ordinary “bents” for prefabricated metal buildings which are about the cheapest kind of building per square foot. Made out of steel, they are typically sold at a cost per ton like other steel shapes.

The cost of the scheme is in maintenance. No ground level access. No easy way to service panels in the middle of the roof. And lots of electrical current if you need to do something during day light because solar panels don’t turn off.

So I agree it is a dumb idea but not because of the cost of steel but for the lack of modularity and abundance of inaccessibility.

rsynnott8 days ago

Solar panels are cheap these days; wouldn’t be terribly surprised if they take the data center approach (if a few machines die, well, who cares, deal with it next time a major overhaul is required).

dyauspitr8 days ago

> No easy way to service panels in the middle of the roof

Cherry pickers like they’re used for every other type of infrastructure.

sandworm1018 days ago

>> And lots of electrical current if you need to do something during day light because solar panels don’t turn off.

No. Lots of voltage (potential) but current only if you tap it. Panels will charge to a slightly high voltage state but do not become a problem.

throwaway20378 days ago

    > The cost of the scheme is in maintenance. No ground level access. No easy way to service panels in the middle of the roof. And lots of electrical current if you need to do something during day light because solar panels don’t turn off.

This is classic HN "armchair critic" comment. Yeah, I'm sure the designers didn't think about any of these issues. If they need to clean the panels, they can use a cherry picker. If they need to service the electrical components underneath, they can wait until the canal is drained (usually once per year for cleaning), and, again, use a cherry picker.

lazide8 days ago

While yes, these are cheap for steel structures, calling them cheap overall is silly. They literally cost more than the canal under them to make (assuming basic earthmoving and concrete formwork), especially when you include the cost for the footers.

As a way to save water, maybe. But it makes no sense as a way to make electricity. Someone else did the math, and it was approx $10/watt, which is silly.

happyopossum8 days ago

> construct a cheap shade over the entire canal

That aint' gonna fly - you're going to have engineering requirements for a 100' span wither it's a shade structure or a solar panel. And don't even think about fabric shade sail types of things, nobody is going to want to replace those every 3 years.

>it takes 1/6 the time to build on developed land compared to undeveloped land.

This is not something you can just ignore

mindslight8 days ago

> That ain't gonna fly - you're going to have engineering requirements for a 100' span wither it's a shade structure or a solar panel

Bingo. "cheap shade" is doing a lot of work. Typical for this kind of drive by "I've thought about it for 5 minutes but the people who worked on this project must be stupid".

amluto8 days ago

To be fair, there are fabrics that last a long time. ETFE is an example. A fair comparison should price the solar cover against fabric.

That being said, solar panels are not that heavy, and fabric is every bit as subject to wind loading as solar panels.

Drunk_Engineer7 days ago

Shade structure is not required at all. California has also been experimenting with floating plastic "shade balls" in the water.

walrus018 days ago

The cost of building that steel structure that will hold up against maximum in 100 year wind forces isn't cheap. Large PV panels make very good sails. The trusses look basically the same as you'd see in a large agricultural barn, horse riding arena, etc. Putting the PV panels on empty bare land at a height people can walk around and work with would be considerably less costly.

I would very much like to see a total dollar figure for the example "roof trusses over the canel" structure vs. how many panels it can hold.

It's already true that the ground mounting costs and labor to assemble the ground mount are a huge part of building a large scale PV system.

defrost8 days ago

The UK has covered some water reservoir with floating PV panels.

The article mentioned trialling several systems for covering California canals, I didn't see "floating" mentioned, although:

  Project Nexus tests not one, but three different solar canal models. 

  ... accordion-like retractable panels are positioned low across the narrow canal, ready to roll up at a moment’s notice.

might come close.

Floating panels have the issue of having to flex and perhaps bottom out (if water diverts to parallel canal for maintenance) on a dry canal - but there's less need for heavy steel trusses and a lower wind profile.

dragonwriter8 days ago

> Putting the PV panels on empty bare land at a height people can walk around and work with would be considerably less costly.

What empty, bare land?

If its really empty and bare, there is a reason for it and that reason is probably a problem for building and maintaining PV, and otherwise you have to add the loss of the alternative uses of the land to the cost.

throwaway20378 days ago

    > The cost of building that steel structure that will hold up against maximum in 100 year wind forces isn't cheap.

I'm surprised by this comment. (Is this area known for strong winds?) If your comment is true, wouldn't all warehouses using the same type of standard "bents" also be very expensive? I doubt it.

    > Large PV panels make very good sails.

A quick Google search tells me:[1] "Most modern solar panels can withstand winds of up to 140 miles per hour." For all of the things I have read about large commercial solar panel installations, never once did I read anything about the risk of wind tearing off PV panels. If this were really a serious threat, wouldn't we see regularly local news stories about large PV panels "flying" away in big wind storms? And, yet, I never saw one.

[1] https://www.makemyhousegreen.com/green-guides/can-solar-pane...

AngryData8 days ago

To my eye if you were putting up a few hundred or more of those steel structures, and it didn't require a redesign of the canal retainment around it, it could be built quite economically.

Every extra pylon structure built, especially the first dozen, will be cheaper and easy to produce and install.

asdff8 days ago

You know where the wind blows really damn hard in California? Virtually any open field you can imagine putting these otherwise. Mojave for example is damn windy. That is why they currently host massive wind installations there.

Kuyawa7 days ago

In Venezuela, currently in an unprecedented electricity crisis with daily rationing up to six hours, 10 billion dollars supposed to replace turbines in the main dam that supplies power to the country were stolen with no accountability. With that money you could have installed solar roofs in a million homes serving five million people approximately

Solutions are easy, money exists, political will doesn't

jmyeet7 days ago

Puerto Rico has this problem too and that's US territory. Not as bad for sure. But it has expensive fossil fuel power generation and unreliable infrastructure. It's screaming out for renewable energy.

The key to all this though is that fossil fuels exist to induce demand for weapons. Once you realize that it all makes (depressing) sense.

toomuchtodo7 days ago

Puerto Rico should be turned into a national park and everyone offered incentives, but never forced, to migrate to the mainland. Needed investment is enormous (not just for energy transformation to low carbon generation and storage, but also their water infrastructure) and the population will only continue to decline into the future.

Citations:

https://ourworldindata.org/profile/population-demography/pue...

https://apnews.com/article/puerto-rico-trump-us-solar-energy...

https://apnews.com/article/puerto-rico-blackout-power-outage...

https://welcome.topuertorico.org/stories/water-crisis.shtml

https://www.accuweather.com/en/climate/what-you-need-to-know...

prometheus19928 days ago

>>The state currently generates 62% of its electricity from renewable and zero-carbon sources, with the largest percentage of that coming from solar

62% is pretty respectable for the size of California (same electricity consumption as Spain). I did not know this.

cco8 days ago

And as of the writing of this comment, ~7pm, about 25% of CA's grid is supplied by batteries: https://www.caiso.com/todays-outlook/supply

I was shocked when I saw how much batteries contribute, honestly don't hear about them much but they have scaled a lot in recent years.

culi8 days ago

Amazing what California can achieve when they don't have to deal with constant cease-and-desist lawsuits, eminent domain battles, environmental review challenges, etc (crying in high speed rail)

toomuchtodo8 days ago

https://www.energy.ca.gov/data-reports/energy-almanac/califo...

Flattening the Duck Curve: batteries reach 44% of evening demand in California - https://news.ycombinator.com/item?id=47633698 - April 2026 (5 comments)

alex_duf8 days ago

You might be surprised to know that worldwide, low carbon electricity production is a little above 40%

https://ourworldindata.org/grapher/electricity-mix?tab=line&...

nonethewiser8 days ago

Also the 2nd highest electricity prices in the USA behind Hawaii

pbkompasz8 days ago

Imagine how much more expensive it would be if renewables didn't make up such a big share.

rpaik8 days ago

Yes, I was impressed with this number as well. I wonder when we'd reach 75-80%, but I believe the zero-carbon electricity target is 2045?

happyopossum8 days ago

> and zero-carbon sources

this part of the claim is carrying a ton of weight here... Zero-carbon sources could include carbon dependent sources with paper offsets.

greenburger8 days ago

Electricity sources are tracked by the California Energy Commission, the 2024 report [0] shows the zero-carbon sources that make up this claim are:

  Nuclear     9.92%
  Large Hydro 11.06%
  Biomass     1.94%
  Geothermal  4.60%
  Small Hydro 1.52%
  Solar       21.30%
  Wind        11.89%

2% from biomass is suspect as a "zero-carbon" source, but the rest seems to be reasonably be zero carbon by today's standards.

[0] https://www.energy.ca.gov/data-reports/energy-almanac/califo...

ShinyLeftPad8 days ago

> Harris said he spent a lot of his life in France, where he noticed how trees lined the canals and protected their precious water from the wind and sun

So why not plant the trees?

Sevii8 days ago

They used to do that in Phoenix. There were trees all along the canals. They replaced that setup with a solid uncovered concrete canal system. The issue with trees is that the roots will cause leaks in your canal.

pjmlp8 days ago

Also take care to have trees close to a swimming pool, just like us, they won't say no to a free source of liquid, and many species have quite powerful roots.

Redoing swimming pools due to close by trees seems to be quite common construction work job.

trollbridge8 days ago

Strange how France didn’t have this problem

ghewgill8 days ago

It's a bit of a challenge to get suitable trees to grow in the central California desert.

s_dev8 days ago

Beside water?

aeturnum7 days ago

You could! But this generates power and has the same benefit. Also you do not have to just do one. Plant trees in areas with denser populations and use solar panels when there are fewer people around and beautification is less of a concern.

ShinyLeftPad7 days ago

I'd assume trees aren't just for people, they're probably good for the ecosystem in other ways...

sagarm8 days ago

$20M for 1.7MW of capacity. Over $10 per watt. Recent utility scale installations in California are more like $1/W.

There'd be some cost reduction from scaling up, but 10x is a huge gap to close. This is a waste of money.

wodenokoto8 days ago

> a $20 million state grant paid for both the research and the infrastructure.

Weimer described the project as a “proof of concept” that generates just 1.7 megawatts of energy, a tiny fraction of the 56 megawatts that they generate with a solar farm in the desert.

But the canal site hosts more than just panels. Bales said they “have instruments out there to measure temperature, relative humidity, wind speed, incoming radiation, outgoing radiation, and a prototype instrument to measure evaporation directly.”

It’s not that simple. It’s a research projects that does more than just solar.

So you need to ask “how much of the grant went into the solar-cover”, and set that up against the value produced (water evaporation, water quality, electricity, etc).

What you did is set the price of the entire research project up against one of its output.

sagarm8 days ago

It's fair to note that only some percentage of the costs went to the panels and associated infrastructure, but a research grade weather station costs like $1k. I'm sure the prototype instrument for evaporation cost more; let's say $1M. That still leaves $19M for everything else. Frankly I have a hard time believing the other stuff was anything more than a rounding error.

As for the benefits: $/w already includes the electricity generated. California loses 1-2% of water in canals to evaporation; I think we can safely assume the economic value of preventing evaporation will be negligible when bare panels cost over $5/sq ft.

I look forward to seeing the author's economic analysis in the full report. However, the fact that these were the only numbers in this fluff piece suggests the economics won't be great.

boringg8 days ago

So thats a pilot project - and the benefits aren't supposed to be your 1$/W its comparing the collective of all the goals for the project. So include the water savings and the cleaning costs - then comparing the two of them.

Its also not comparing against utility projects because it isn't utility scale.

naasking7 days ago

> $20M for 1.7MW of capacity. Over $10 per watt. Recent utility scale installations in California are more like $1/W.

It's a) just a trial, and b) not just generating power so that cost isn't factoring in the other benefits.

throwitaway2227 days ago

They prefer to spend $100M on CHIRLA

Read the full thread on Hacker News →

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