TLDR Would reduce canal evaporation and add ~13GW of solar generation capacity (compared to the current ~20GW of current utility scale generation in the state).
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.
> At some point, the costs associated with conserving an additional drop of water exceed the benefits,” she says. But, she notes, if solar expansion is inevitable, then maybe hanging the panels over canals could tack on some extra benefits that might not come from building elsewhere.
Which is only counting part of a positive, and excluding the value of the electricity.
> cheap land elsewhere
Not really sure where that's going to be in California, what are you thinking?
And then if you use distant land, you have to pay for new transmission, which dwarfs the costs of solar panels and inverters.
Solar hardware is incredibly cheap these days, and getting cheaper by the day. Putting solar panels instead of non-generating materials will miss out on all the benefits of how cheap solar PV has become. We should think about PV panels a lot like microcontrollers: so cheap that they can be thrown into all sorts of applications that would have been shocking 20-30 years ago.
People can get weird about solar panel placement and constantly come up with terrible ideas like putting them on cars (not enough surface area for any real power) or roadways (no!). Does anyone know if this idea is one of those terrible ones or is genuinely feasible?
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.
if you use water to cool down the panels then you should not expect to lower the evaporation. I would say that this would increase evaporation as solar panels reflect less light than water. but this is just speculatio from my side.
Catching the light before it hits the water does reduce evaporation. It does not eliminate it. The water is not used for active cooling. Water has high specific heat and liquid to gas is endothermic. Which is why the water temperature is lower than the ambient air temperature.
Putting the panels over the canals reduces evaporation while cooling the panels. This is proven.
You can't cheat thermodynamics! If it's being absorbed by the panels (rather than reflected) then it's absolutely becoming waste heat. Solar panels look dark blue/black because they're absorbing most of the light that hits them. This is why them overheating is a problem that can affect performance. If they were mirrors they wouldn't overheat at all, but they also wouldn't be able to produce any electricity.
Thermodyamics says that a solar panel is cooler than an equivalent black panel. Some solar energy gets converted to electricity. All of that converted energy does not end up as waste heat. A 100% efficient solar panel would not get hot. Only the inefficiency ends up as waste heat.
Maybe I'm missing something obvious, but by conservation of energy if all of the energy of the sun was converted to heat then no electricity would be produced? Conversely, that fact that panels do produce electricity means that not all of the sun's energy is heating the panel?
solar panels are only partially efficient. if the solar -> electric conversion efficiency is 21%, then 79% of the incoming solar radiation is converted to heat.
The portion of incoming light that becomes electricity is dissipated as heat primarily where it is used (e.g. in an appliance attached to the grid fed by the solar panels), not in the cells themselves. So it's true that a cell connected to an external load will be cooler at equilibrium than one that is disconnected.
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.
Yeah, solar panels have become really cheap. I am looking into covering a flat roof with solar. The support structure (nothing super fancy) will probably turn out to be more expensive than the panels themselves.
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.
> 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 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.
Nothing. The panels aren't intended to contain the water within the canals, they're installed above the water on racks. Aside from catastrophic flooding that might compromise the solar panels' supports, the panels wouldn't be impacted by flooding.
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.
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.
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.
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.
Solar panels are fully encased in glass enclosures, so I'm pretty sure there is no runoff, but yeah putting them above water ways like this does make you think.
The heavy metals in solar panel waste you typically hear of is for discarded and broken cells in landfills iirc.
No - any toxic materials in a solar panel are bound up in the silicon and unable to leech out. Rain is generally good, as it cleans dust off and increases efficiency. Pollution is not a concern at all with solar.
There's a concerted disinformation campaign out there to try to insinuate that solar panels break and then poison the ground. Here's a podcast covering some of it and the funding mechanisms that help push it:
People will believe anything with the right confusing language. Throw in "rare earth minerals" and everybody gets as scared as if you call water "dihydrogen monoxide."
Prevent evaporation sounds like a good idea, but it seems like the payback for that alone must not be much, or else they would have been covered a long time ago (with non-solar-generating materials)?
I'm not saying it doesn't make sense in conjunction with power generation, but that it's probably much less of a benefit.
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.
Bird poo is a big problem to solar panels, and aquatic birds release a lot of very sticky product and will try to land in the panels to rest. This is -the- problem IMAO.
They will need to find how to spray and clean the panels routinely or the panel efficiency will decrease a 30% in no time.
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.
At what point is preventing evaporation a bad thing? I realize that we have already done quite a bit to change when and where water evaporates, but doesn’t moving where, if ever, the water evaporates affect the local water cycle?
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.
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.
If I were to guess as to the motivations of those who downvoted, it'd be because of this statement:
> Just cover the canals as cheaply as possible.
Covering the panels as cheaply as possible is probably not worth the cost. Covering the canals with something that produces energy tips the scales to make covering worth it.
Then there's this part:
> And then put solar panels where it makes sense to put them
I agree with that, and wouldn't consider that worthy of a downvote. But without an explanation of "where it makes sense to put them", it's not very constructive.
Your reply, however, is far more constructive. It probably doesn't makes sense to cover every possible square inch of canal without considering the costs and benefits, or without considering the costs and benefits of alternative solutions.
Keep in mind, the idea isn't only to produce energy. It's about reducing evaporation and maintenance of uncovered canals. Covering panels with just about anything other than solar panels helps reduce evaporation and maintenance, but that's it. If you can cover it with something that can produce energy, then the cost of covering the canals can be offset by the energy produced. Emphasis on "can", because as you point out, it's not as simple as slapping panels down and calling it a day.
I find it ironic that you both are accusing others of not using critical thinking while failing to hold yourself to a similar standard!
At least learn about the project before laying down a mountain of fear, uncertainty, and doubt. Your "concerns" are addressed by other comments in this thread, yet you didn't hesitate to levy them without research or thought.
> The net present value of over-canal solar exceeds conventional overground solar by 20–50%, challenging the convention of leaving canals uncovered and calling into question our understanding of the most economic locations for solar power.
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.
I'm confused. Reading many of the comments it sounds like preventing evaporation is the major reason for this. Given that it hasn't been done yet, evaporation must not be a major issue, so we shouldn't bother.
I was under the impression that building more solar into the grid was the reason for putting up solar panels and preventing evaporation was a side benefit of their placement.
> 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.
> Reading many of the comments it sounds like preventing evaporation is the major reason for this.
That's the important part of the paragraph. I'm not asking about the evaporation, so much as why that's what everyone seems to thing the point of building the solar panels is? I would expect they were going to build them anyways, and the prevention of evaporation seems to be a bonus. But reading the other comments, it would appear that's a wrong assumption.
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.
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.
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.
Right. The LA River is an emergency drainage system that isn't needed much.
Last month, it was needed.[1] The California Aqueduct is usually kept full.
Falling into the California Aqueduct is usually lethal.[2] 30 feet deep, steep banks, and a high rate of flow. It's fenced, but just with ranch fencing.
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.
https://www.asce.org/publications-and-news/civil-engineering...
https://www.nature.com/articles/s41893-021-00693-8
https://app.electricitymaps.com/zone/US-CAL-CISO?wind=false&...