California wants to cover its canals with solar panels

Thank you for providing links!

The first one contains a lot of the same doubts I have and points out that this is an exploratory project explicitly because the ROI is unclear.

The second one is a bit strange. Here’s the actual paper [1]. And what they actually studied was “ To address this critical knowledge gap, we quantified the evaporation savings and financial performance of over-canal solar in comparison to over-ground solar on land adjacent to canals”. So they’re assuming leaving the canals uncovered and siting solar power plants on expensive ag land instead of covering the canals cheaply with traditional shade materials and using the savings to build power generation on cheap land elsewhere. Not very convincing to me.

Personally, I think the net benefit will be negative, but I’d love to be proven wrong on this.

[1] https://escholarship.org/content/qt8cj5j07p/qt8cj5j07p_noSpl...

> Does anyone know if this idea is one of those terrible ones or is genuinely feasible?

They've done it India, a country notorious for red tape. Which begs the question: how long will it take California's bureaucratic ineptitude take to screw this up.

The proximity to water cools the the panels which increases their efficiency, there's a lot of sq ft available, and the government already owns the land. It also decreases the amount of water lost to evaporation, and the amount of weeds/plant growth around the canals since there's less sunlight for them.

In this case there's a desire to cover the canals anyway for evaporation reasons. There's a reason you see a lot of solar covered parking: once you're already building the structure to support a cover, it doesn't drive up the structure cost that much to make it racking for solar panels. So this kind of thing can produce a real cost savings, by installing solar in situations where the supporting structure is desirable for independent reasons.

I can’t see anything obviously terrible. Its not small segregated mobile areas like cars, and its something people drive on like roads.

Canals are naturally fairly linear and remote, which seems to imply maintenance is likely to be less efficient than if you had a single compact site with similar area, but it also isn't competing with other land uses, whereas a compact installation would be.

One concern is CA has lots of solar and supply problems are most acute outside of peak solar production times as a result, so without robust storage, massive additional solar capacity may not be as useful as the peak capacity makes it seem. (Though, that also means more off-peak capacity, too, which is useful.)

It has nothing to do with science or even power generation. This is about regulatory compliance. They put them over canals because a canal is not private land. Either they are owned by government or the government has easements for their maintenance and improvement. Canals are also readily accessible for light construction, most all of them having a dirt road alongside. The same principals apply to roads. Governments face all sorts of issues acquiring and building upon new land. But placing something beside, on top, or even within the road surface can normally be done without new permits let along environmental impact statements.

Pros: Reduces evaporation Cools the panes so they’re more efficient Uses otherwise unused space

Cons: More difficult to install and maintain Less efficient for management since the panels are in long thin tracts rather than square ones

Pros seem to outweigh cons in initial pilot deployments

Additional critical benefit: somewhere to run the transmission lines. Tautologically where the water goes so too can the transmission, certainly to connect to the nearest convenient substation.

The cost of solar panels is less than the cost of installing them on a roof in California. I guess the real question is whether it is more expensive to install the panels over a canal or over a roof.

Also, what happens when the canal floods?

I've always wondered just how awful the run off from rain landing on solar panels is as far as those nasty sort of chemicals that we then find out are terribly carcinogenic or disruptive to human health. Same would apply to water condensation forming below the panels and dripping back into the canal.

Given the materials that go into solar panels and the proximity to water that will end up in either the food supply, or inside people; I would hope they at least run some tests.

Stupid question but why not above roadways?

There are already light fixtures and usually power lines going around there. It would block some sun from the black road and that's also a good thing. Sending a maintenance vehicle would be easy as it would be accessible.

The only downsides I can see are:

* It needs to be tall enough so trucks won't hit it. So that might make it more expensive. * It might be stretched over a long distance creating logistic problems with the delivery and efficiencies.

Is there anything basic that I'm missing here?

Solar over canals and reservoirs is a great idea, and the catchy name is floatovoltacis for floating installs on reservoirs. Solar roadways are an absolutely terrible idea.

I think that car placement is still mostly bad idea but it shouldn't be thrown out yet. As PV gets cheaper and cheaper, the financial impediment disappears and it starts to make a small bit of sense.

For a regular sedan, solar panels won't make a car completely autonomous, but one could fit at least 600W of cells, and if parked in the sun all day, that could generate 2-3kWh of power, which is 8-12 miles of range.

Plug in charging would still be needed, but that extra bit of power could be used for temperature control of the battery pack or interior too, while the car is sitting in extreme heat in Phoenix, or outside a garage in North Dakota.

So there's not really a $20 bill on the ground, Mr. Economist? :-) There was no payback because the water kept flowing regardless. But past performance is no indication of future performance, and that realization is starting to dawn on at least a few folks.

There already are reservoirs that are covered to prevent evaporation. See: https://en.wikipedia.org/wiki/Shade_balls

1-2% of the water that goes into the canals is currently lost to evaporation:

https://theconversation.com/installing-solar-panels-over-cal...

So, reducing that is not going to have as big an impact as, say, improved irrigation techniques, or building more reservoirs.

However, it will produce a lot of electricity. (Though probably less per dollar than putting the panels on top of failed farmland.)

In this case there's no eminent domain issues since the government already owns the land the canals sit in, which significantly reduces local governments abilities to stop the proposed projects. Additionally, since it will increase water availability its unlikely that farmers in the central valley will fight it.

I'm already waiting for creative NIMBY counter-arguments.

Local water cycles are already affected though. This is water that has been released from reservoirs and aquifers. Covering the canals with solar panels isn't like covering a natural river and interrupting it's water cycle. It could mean we have less need to use the reservoirs and aquifers... moving the local water cycle to a more natural state.

Preventing evaporation on your aqueducts and canals definitely isn't a bad thing though. That water is precious and you want to lose as little of it as possible.

I'm pretty sure a giant concrete channel has a much larger effect on local water cycles

That doesn't sound very instagrammable.

You'd clearly never make it as a politician.

The fact you got downvoted for saying this shows how little critical thinking is going on around here. If people think this is a good idea, show us the numbers: how much would this cost including running all the cabling, building substations, linking into the grid, adding scaffolding spanning the canals, all for hundreds of miles. Compare that to $1800/kW installed for a normal solar power plant [1] and however much basic shade tarp or shade balls would cost to provide the same evaporation benefit.

And no, I don’t believe “the government already owns the land” is a good argument here. We’re talking about comparing to land cost for a power plant literally in the desert, of which there is an awful lot in Southern California.

[1] https://www.eia.gov/todayinenergy/detail.php?id=48736

I've seen this done by Indian Govt in some regions. It made good press there and I guess some politician decided to cash in on the bump. IMO It makes a little more sense in India tho, because of very hot climate & also the far out places that need electricity are also in teh middle of nowhere needing power so makes marginal sense to put generation closer to the last mile. plus labor is cheap so servicing is not really a problem. In California none of those things are in play so the idea is mostly bogus.

> Given that it hasn't been done yet, evaporation must not be a major issue, so we shouldn't bother.

Because of the droughts and increased population, preventing evaporation has become a lot more important today than it was 50 or even 20 years ago.

> Given that it hasn't been done yet, evaporation must not be a major issue, so we shouldn't bother.

Do you really believe this?

It reminds me of the joke about an economist that doesn't pick up $100 off the ground, because if it was a real bill, somebody else would have already picked it up.

If the expense of the solar panels is not Bourne by the beneficiary of the increased water supply then there was no incentive other than the solar power.

It is done in some places, often with "shade balls"[0]. If doing it with solar panels brings to cost down to ~$0, then why not do it many more places?

https://en.wikipedia.org/wiki/Shade_balls

Not in CA, but where I live there is continuous work on covering canals. A lot of canals were dug a century or more ago and are just ditches, something like 60% of water is lost to evaporation and seepage. The issue is still the cost, the price of water delivery is not generating the revenue to do it all at once. If they can also do solar, they can recoup those costs faster.

The idea isn't limited to reducing evaporation, but for controlling algae. From the article:

> reduce algae growth and the need for maintenance by limiting sunlight falling on the water

Evaporation is an issue, for sure, but so is the cost of keeping algae under control. It makes a lot of sense to trade algae for solar panels even if you have to maintain the solar panels.

I think they are mostly talking about the ones that carry water much (all?) of the year in the central valley, rather than the ones in L.A. proper. So I don't think skaters will have much to complain about.

As a member of that community, I am happy about this (and appreciate the consideration for our happiness - it's not something we're accustomed to).

Forgive me for stating the obvious, but the kinds of canals we skate don't contain flowing water. Sure, there are rivers with engineered concrete river beds in metro areas that might have a smaller channel with water, but the skateable parts are dry (Santa Ana river, Los Angeles River, etc).

Concrete river beds are also more of a novelty than they are enjoyable. The concrete is like corduroy. It takes a lot more effort to move, and when you fall, you leave smeared portions of yourself behind.

The canals the article talks about are much smaller, and typically serve agriculture in Central California with edge to edge flowing water. When dry, those can be fun, but again, they're not the first on my list of fun places to skate (which isn't to say they're not fun, just not as fun as other places). They're full of debris, very rough, and lose their appeal pretty quickly.

Personally, if losing those spots means more efficient use of water, it's a very small price and one I'm willing to pay.