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# California to try tackling drought with canal-top solar panels

California is ready to try out something that could help it save water and generate electricity at the same time: solar panels over irrigation canals. For this proof-of-concept experiment, some 8,500 feet of photovoltaic panels will be installed over waterways just north of Turlock, central California, generating electricity …

## COMMENTS

1. #### 372 miles

By my rough calculations that's how many miles they'd need to cover to generate 1.21 Gigawatts.

1. #### Re: 372 miles

How about one step further, use ocean water and solar panels. Quick web search:

“The theoretical absolute minimum amount of energy required by natural osmosis to desalinate average seawater is approximately 1 kilowatt-hour per cubic meter (kwh/m3) of water produced, or 3.8 kilowatt-hours per thousand gallons (kwh/kgal). The actual SWRO energy requirement in the 1970’s was 7.0 to 9.0 kwh/m3 (26-34 kwh/kgal). With recent technological advancements and innovations in high efficiency pumps, energy recovery systems and overall higher efficiency plants, the actual expected consumed energy has reduced to 2.5 to 3.5 kwh/ m3 (10-13 kwh/kgal)”

1. #### Re: 372 miles

As long as you allow for the waves.

2. #### Re: 372 miles

And dump all the salt at the local fast food joints?

3. #### Re: 372 miles

Pick a unit system and be a dick about it. That kwh/kgal figure is an abomination!

1. #### Re: 372 miles

I don't know - I quite liked it.

Both sides are seriously oddball, non SI units - but both are also fairly well understood (particularly in USland)

1. #### Re: 372 miles

So instead of kwh/kgal would kg/m/s^2 make more sense ?

2. #### Re: 372 miles

Psh. Remember what site you're posting on...

https://www.theregister.com/Design/page/reg-standards-converter.html

1. #### Re: 372 miles

Thank you for reminding our friends of El Reg measurement Standards. ----> on me.

3. #### Re: 372 miles

Pick a unit system and be a dick about it. That kwh/kgal figure is an abomination!

Many years ago, I worked on fire-control software for a US Navy project. It had a bunch of different input devices: INS (3D heading/velocity, location), Sonar (for ground speed), Wind speed/direction, Odometer ticks (also for ground speed), Temperature, and so on) as well as a bunch of data input by the operator (starting lat/long/elev, barometric pressure, and whatnot). Absolutely everything was in metric except for one internal value that was calculated based on various inputs: air density was in slugs/m^3. I asked why, and was told that's just the way it's done in the US Navy.

2. #### How about floating on reservoirs?

<quote>

The solar photovoltaic (PV) system, developed by Israeli startup Xfloat, is designed to move and track the sun while floating on reservoir water. The project is being carried out in cooperation with Mekorot, Israel’s national water company,

</quote>

1. #### Re: How about floating on reservoirs?

Done

https://www.lightsourcebp.com/uk/projects/queen-elizabeth-ii-reservoir-solar-project/

1. #### Re: How about floating on reservoirs?

Yes, this one's a great thing to spot when you depart westwards from Heathrow, or if you are being brought into the airport from the west. :-)

2. #### Re: How about floating on reservoirs?

Done.

https://solarmagazine.nl/nieuws-zonne-energie/i24664/profloating-installeert-5-000-drijvende-zonnepanelen-bij-plantenkwekerij-bernhard

And several other projects.

3. #### Re: How about burning on reservoirs?

Done...

https://www.pv-magazine.com/2019/09/09/japans-largest-floating-pv-plant-catches-fire-after-typhoon-faxai-impact/

1. #### Re: How about burning on reservoirs?

About as smart as putting them in Lake Okeechobee

4. #### Re: How about floating on reservoirs?

Brings up a good point. This will impact waterfowl, whether anyone likes it or not. This in turn means that this project will be held up for 10-15 years by Environmental Impact Statements, attempts to create exemptions, and related lawsuits on all sides. Cost magnitude will be 10-25X by the time it is all settled. The budget allocation will be enough for a 100-foot section after legal fees are paid.

3. #### 13GW

That's an actually useful amount of power.

It's one of those "So obvious why didn't anyone think of it before?" ideas.

But yes in principle max sunlight --> max risk of evaporation so there's a nice sens of tracking.

Now the notion is out there let's hope more organisations roll it out.

1. #### Re: 13GW

2010 was the only time I have been in that area of the world and I mentioned the idea to everyone I met who might pass it on (mainly large land and business owners, and park rangers rather than government officials as I was there on vacation) - the idea originally formed to retain water by covering the canals, but it was obvious to gain electricity by using solar panels to do the shading.

Also panels on stilts on the sides of storm drains to gain electricity from underused land.

1. #### Re: 13GW

Over car parks!

While they wouldn't have the evaporation benefit, think how much less cooling of vehicles by A/C would be required - especially when they have been roasting under the midday sun.

1. #### Re: 13GW

In South Africa (with all its sunshine) there are a number of shops/stores and office parks that do exactly this. The solar panels also provide protection to the vehicles in the event of inclement weather (e.g. hail storms that are all too common in the summer months).

1. #### Re: 13GW

How well do the PV panels stand up to the hailstones?

I'm thinking the golf-balls sized ones I believe SA gets!

1. #### Re: 13GW

Good question. I have 24 solar panels on the roof of my house as well as two solar geysers. We have had no breakages yet (still holding thumbs). I live in Joburg, an area with regular hail storms in the summer months. The nice thing about the storms is they wash all the dust off the panels... it helps improve the efficiency of the cells. In the dry months we have to manually clean the dust off.

1. #### Re: 13GW

Solar hot water is brilliant... we had this in the eighties a couple of thousand kilometres north west of you ;-)

The panels designed at the time were heavy as hell because they actually used glass and steel plating, but it provided some seriously hot water even in winter (although there we still had to backfill with an electric tank heater once the sun set).

2. #### Re: 13GW

I'd also be interested in that. I'm planning to put PV on my roof, but we do get golf ball hail every now and then. I heard that the panels can resist it just fine, but I'd love to find an authoritative source.

3. #### Re: 13GW

There are some nice photos of this coming out of Spain today. They just had a damaging, unfortunate and tragic hail storm.

1. #### Re: 13GW

Unfortunately a young child almost two years old was killed by the Spanish hail - but she would have been just fine if she had been under a solar panel.

2. #### Re: 13GW

"Over car parks!"

The car parks at Perpignan airport have been covered that way for years.

1. #### Re: 13GW

"Perpignan airport"

Sounds like a great idea. I want to propose the same idea to our local airports. I had a look at the Google Earth images of the Perpignan airport in southern France, but I don't see any solar panels on images that are dated 2022. Am I looking at the wrong airport?

https://www.google.com/maps/search/Perpignan+airport/@42.7397636,2.8672996,221a,35y,39.47t/data=!3m1!1e3

2. #### Re: 13GW

And of course you can increase the incident radiation by crash-diving a remote controlled space ship into the heart of a nearby sun, thereby causing massive solar flares... Just make sure that your robotic car park attendant doesn't accidentally end up onboard the stunt ship.

3. #### Re: 13GW

Already being done

https://www.cnet.com/google-amp/news/solar-parking-lots-are-a-win-win-energy-idea-why-arent-they-the-norm/

4. #### Re: 13GW

"Over car parks!"

that is actually done a LOT. The local Walmart has several rows of covered parking with solar panels on top. Not the entire lot, but a significant portion of it. It has to make cost sense though.

Even without the panels, covering the canals with "something" has been discussed for DECADES.

There are many other issues outside of the scope of the article and related discussion, though, that could actually make a MUCH BIGGER difference in water usage and availability... related to the Sacramento river and a certain kind of fish. And maybe better drip irrigation systems for farmers, too.

1. #### Re: 13GW

A lot of reservoirs in California were covered in black plastic balls to stop evaporation

Of course it turns out that making 100Million plastic balls uses a lot of oil / energy /water - but if you are building the solar panels anyway

5. #### Re: 13GW

Are you sure you aren't from EEVBlog, his been saying this over and over especially when pointing at SolarRoadways and going wtf

2. #### Re: 13GW

That IS actually both a useful amount of power, and a good use of a space that otherwise can't really be utilised. Clever.

But.... not sure that the protection from evaporation will help so much with drought. All that evaporated water eventually would have fallen as rain (even though probably somewhere else). So you're only 'exporting' the drought to some other place. Depending on prevailing winds and weather patterns this could be disastrous for some other adjacent area that would get an even more severe drought.

OR it could reduce rainfall in an adjacent area tat is otherwise prone to flooding.

If good enough models can be constructed to anticipate the latter and only cover the canals in those areas it would really be a giant win.

1. #### Re: 13GW

I suppose the evaporation rain cycle also helps purify the water... I've never got why solar evaporators aren't used more to alleviate water shortages during a drought. Data centre... sea water... I mean CDNs are best placed near to undersea cable heads, aren't they? And they're putting power plants near the sea...

4. #### Reduced Evaporation

Now I have limited understanding of the science on this but:

How does covering water with solar panels reduced evaporation by that much?

The ambient temperature is pretty much the same.

The panels have reduced the direct sunlight but on water, it is not sunlight that causes most of the loss, it is wind.

Now I can see that the panels should reduce wind speed to some extent but they may also increase it with a tunnel effect.

In terms of a useful place to put the panels, then I can see that is worthwhile but I am not sure how much of a saving in water loss there will be.

1. #### Re: Reduced Evaporation

The ambient temperature is pretty much the same.

However, the surface temperature as well as the air temperature immediately above it is not

1. #### Re: Reduced Evaporation

Also, its supposed to be floating, so, if the surface area of the float covers most of the water way (directly on the water), there is little surface area for evaporation to occur, which occurs with low temps also, due to low humidity.

1. #### Re: Reduced Evaporation

In the California case they are built on a framework above the waterway if the image is correct.

This will reduce the direct sunlight but not the wind.

I can see how floating panels could be a benefit but these are not.

2. #### Re: Reduced Evaporation

>How does covering water with solar panels reduced evaporation by that much? The ambient temperature is pretty much the same.

The water temperature is a factor in the evaporation loss. And evaporation cools the water. So direct sunlight will keep the water warmer than it otherwise would be (that sunlight energy doesn't just disappear).

One would expect the ground through which the canal flows to keep the average water temperature cooler than it otherwise would be... but complex fluid dynamics are complex, duh, so I wouldn't be shocked if there was a warmer surface layer, warmed by the sun.

https://www.engineeringtoolbox.com/evaporation-water-surface-d_690.html

3. #### Re: Reduced Evaporation

After all the downvotes I researched this some more rather than relying on the experience of what I see in my pond!

Wind & temperature are both critical:

The higher the temperature, as one would expect, the higher the evaporation.

The higher the wind speed the higher the evaporation.

The reason for this is that the in still conditions the air above the water will contain more water molecules as they evaporate, reducing the rate of evaporation (high humidity). If the wind is constantly blowing the water molecules away from the surface, humidity is lower so there is greater evaporation.

I would assume that California is both hot and has some wind, even if it is just a few mph that gives you the worst case.

So, yes covering the water will reduce the temperature (shaded) and reduce evaporation. Crucially in this scheme, the panels are not on the surface but are on a framework over the waterway.

What is rather more interesting is that increasing the depth to reduce the temperature of the water may have a greater effect.

This probably provides the most concise summary without spending hours:

https://www.globalseafood.org/advocate/evaporation-affected-by-sunlight-temperature-wind/

5. #### Isn't this a good "shady" idea in general?

I have been wondering how much the shade thrown by solar panels if mounted as a sort of second roof would contribute to keeping the house underneath more cool.

If I'm not mistaken a double roof (i.e. one to throw shade on the other and an air gap to vent any heat buildup) is already in use in countries far warmer than ours and I even found links that seem to confirm this. The disadvantage is that you need an extra construction and that it needs to be far more gust proof (due to the airgap), but it strikes me that we could take more advantage of those basic physics in play

Sadly it's not going to work on my own house as it's listed, solar panels are apparently not deemed a period feature :). But hey, I also have a man cave shed :).

1. #### Re: Isn't this a good "shady" idea in general?

"Sadly it's not going to work on my own house as it's listed, solar panels are apparently not deemed a period feature :)."

Same here (though conservation area rather than listed), and roof just the wrong size and shape too :(

1. #### Compensation

Is it time that people who are told they can't improve the energy efficiency of their property "due to planning restrictions" are given compensation to cover the extra costs they have to cover?

1. #### Re: Compensation

Wasn't that already baked into the price when the property was bought? Caveat emptor?

1. #### Re: Compensation

Not when the restriction is placed on the property after it has been purchased.

2. #### Re: Isn't this a good "shady" idea in general?

Been contacting local companies and brokers since February this year. So far I have had one vague quote for 23Q2 installation (i.e. full of caveats that the price may change) and another company planned to visit in a week. It's almost as though a 5 bed, south facing house is too small a deal for them!

3. #### Re: Isn't this a good "shady" idea in general?

As far I can see my solar panels are an inch or two above the roof tiles fixed to the joists through the roof proper, I know this cos pigeons get in there to make nests sometimes (yes must be a squeeze), so do I have a double roof? Its been there for 10 yrs so far no problems - except for the WIFI montoring which wont connect to my (sob) eero6 network

4. #### Re: Isn't this a good "shady" idea in general?

Sadly it's not going to work on my own house as it's listed

Two solutions spring to mind. Firstly, solar panels don't have to be on the house roof. Build a verandah or gazebo or something out of them. Put 'em on the shed roof (I realise this isn't doing the "shade the house to keep it cooler" thing). Even a greenhouse - not all panels block all sunlight, and thin-film flexible PV materials are now apparently available which while not as efficient as traditional panels have the potential to be significantly cheaper and can be applied to glass instead of the sorts of security and shading films often fitted.

Secondly, if the problem is aesthetic, there are such things as solar slates which can look very much like natural slate (not cheap mind), though I realise listed buildings can have a range of roofing materials which are not slate!

Disclosure - a friend works for the company I linked.

M.

1. #### Re: Isn't this a good "shady" idea in general?

That was very helpful - I didn't know there were more companies out there making solar slates. I was not inclined to buy anything Musk has his hands in as warranty doesn't seem to be part of his business ideas so good that there's a 'local', so to speak although I my have to see how expensive and troublesome Brexit has made this..

1. #### Re: Isn't this a good "shady" idea in general?

I my have to see how expensive and troublesome Brexit has made this

Assuming you are in the UK, there are some prices on that site, for example:

The standard 500x250 PV Slate unit has a peak output of 28W and an ex-works price of £59.50. Each 500x250 unit replaces four natural 500x250 slates, covering an area of 0.2sqm. That gives PV Slate an overall roof kit price of £294/sqm or £8,449.00 for a 4kW system.

which I believe to be fairly up-to-date. Brexit has affected some prices, but this company does a lot of its own manufacturing. Their biggest problem at the moment (my friend tells me) is sourcing inverters, particularly for larger systems. This isn't a brexit issue, it's the current semiconductor supply problems.

M.

6. #### Switzerland & Glaciers

This Swiss should try this to help mitigate the massive glacier loss as well as help mitigate the loss of electricity brought about the impending closure of nuclear power plants.

1. #### Re: Switzerland & Glaciers

a) It's relatively easy to build structures either on the canal sides to support panels over the canal if the canal is a few metres wide. It's not gonna happen for a glacier that's a few hundred metres wide.

b) on water you can make the panels floating, over ice they have to be supported, so you run into problem (a). Building the supports directly into the glacier wouldn't work since the glacier moves and will break the supports

c) It would be a lot of awful-looking massive infrastructure introduced into pristine mountain areas

If the intention is to cover the glaciers, it's already done with white tarp-like material that combines high reflectivity with looking rather similair to the ice, protecting it without ruining the landscape. Although for space reasons I think it's done only on glacier tongue where there is most melt rather than the entire glacier (covering which would be prohibitive eg Rhone glacier is 16 km2)

7. #### 13GW from four thousand miles of solar panels...

... is about what you could get from ten reasonably large wind turbines. And they wouldn't stop freight running along the canals in barges.

Am I missing something?

1. #### Re: 13GW from four thousand miles of solar panels...

Irrigation canals, never used for freight in the states.

1. #### Re: 13GW from four thousand miles of solar panels...

There were plenty in the east, just not California.

wikipedia.org/wiki/Erie_Canal.

2. #### Probably

the fact that these are irrigation canals, California being California (i.e. dry). Neither the native American or the Spanish population showed much interest in transport by canal and by the time the Usanians arrived they had railroads to do the job.

(Dammit, ninjaed!)

3. #### Re: 13GW from four thousand miles of solar panels...

I'd like to know where you get your wind turbines from ...

I thought the largest ones in the world that have been commercially deployed were rated at about 10 MW ...

1. #### Re: 13GW from four thousand miles of solar panels...

I wondered the same, I watched a video a few months back of physicist Helen Czerski visiting the worlds largest wind turbine, and that was 13MW, but it's a prototype off-shore unit, mounted on shore for testing, so not yet commercially deployed.

I did a quick look up, it's the Haliade-X in Rotterdam port. 260m tall, each blade is 107m long! Seems they expect these to hit 14MW for the production versions.

Looks like they plan to install 100s of these at the Dogger Bank Wind Farm project (along with other similar sized units from different manufacturers), for a total generating capacity of 4.8 GW.

So not even half of the 13GW, and that's going to be the largest offshore windfarm ever built (till the next one of course) :-)

4. #### Re: 13GW from four thousand miles of solar panels...

Am I missing something?

A calculator I think. 13GW is 1000 large 13MW windmills

1. #### Re: 13GW from four thousand miles of solar panels...

A solar calculator?

5. #### Re: 13GW from four thousand miles of solar panels...

Not all irrigation canals are sized for barges.

8. #### Costs and Corrosion

Key paragraph:

"Still, the costs to construct canal-top solar systems can become much more expensive. Among the costs that Indian officials have run into is the need to galvanize panel supports with zinc due to increased risk of corrosion, and finding canals that are not too narrow, which would be inefficient, or too wide, making construction costs too high."

California could instead eliminate its "sanctuary cities" and repatriate its millions of illegal aliens, which would reap promptly greater returns, including profoundly reduced water usage.

1. #### Re: Costs and Corrosion

Think of the MOSQUITOES!!!

1. #### Re: Costs and Corrosion

I am - it was a great aircraft!

1. #### Re: Costs and Corrosion

wooden you know it

2. #### Re: Costs and Corrosion

I suspect this hasn't happened because when it comes to repatriating Aliens, typically either their engines have broken or no-one get through to anyone that can offer them a lift home.

Although you're certainly right about the water - that Alien that looked just like David Bowie turned up a few years ago, he was definitely after the water.

1. #### Re: Costs and Corrosion

The term illegal alien, as defined by U.S. law, is dispassionate. Its context is well understood.

Its deliberate rewording by agenda-driven activists and the media is flagrant propaganda and should be called out as such.

Regarding Bowie's character: The extraterrestrial was not an economic refugee. The United States would likely bend over backward, as much as practicable, to help such an alien and his people, assuming, of course, that they were not the predatory lizards from "V" or the like. The last unhingeable jaw that anyone here wanted to see was Linda Lovelace's.

Good movie (his, not hers)!

9. This article would be interesting and understandable by most if it didn't mention those medieval units used everywhere except in most countries

== Bring us Dabbsy back ==

1. Yes, I was a bit puzzled why you would measure a quantity of solar panels by length (feet) rather than by area (metres squared).....

1. A typical domestic solar panel is 1.85m2 with 370W output (peak).

Using those figures, your 13GW (peak) will be 35.1 million panels, with an area of 65 million m2, or 6500 hectares.

We don't know the width of the canals, but if we're talking 4000 miles ~= 6400km, that means roughly a 10 metre span on average.

What nobody seems to have mentioned is the cost. 35 million panels, even at \$100 each, is \$3.5 billion. That's without 4,000 miles of supporting structure, or the inverters, or the electrical interconnections.

Still - a lot cheaper than HS2, and probably more benefit. (Thinks: train tracks are uncovered most of the time. You could lay solar panels on the sleepers?!)

1. You could lay solar panels on the sleepers. I wonder how many days (hours?) it would be after they were installed that the first person was hit by a train whilst trying to steal them? (Thieves on the line is quite a common a problem. in the UK...)

1. They wouldn't steal them though after they are covered in shit and piss.

2. A typical domestic solar panel

Home-grade solar panels are not used on jobs of this scale.

2. We have many , many, many more problems in this country than what units of measure we are using.

It isn't like there isn't a bunch of agreed upon formulas for converting between them.

10. #### Nexus? Nexux?

Roy, where have I heard that name before?? Or am I going Batty?

11. #### Won't somebody think of the ducks

bouncing off with surprised look on their beaks "it was softer than this last year"!

1. #### Re: Won't somebody think of the ducks

Well, it's California, so the eco-freaks will be out protesting about ecology or wildlife being affected or something.

12. Once completed they will rename to Turlock Undercover Reticulation District.

13. #### Saving water for more abuse?

Irrigation in California, especially Central Valley, is an example of abuse of a scarce resource: water. If there is less irrigation, you need fewer canals for the water and will thus lose less to evaporation.

In the meantime by all means cover the canals. Also, install panels over the fruit trees in the above mentioned Central Valley and elsewhere. This will provide power for the warms and protect the trees

1. #### Re: Saving water for more abuse?

And how do the trees get light on the leaves?

1. #### Re: Saving water for more abuse?

Could install electric lights under the panels?

2. #### Re: Saving water for more abuse?

Panels don't block all the light and you don't go for 100% coverage. See this report (in German but with pictures).

14. #### "enough to irrigate 50,000 acres of farmland"

Great.

That'll be another 10 almond farms in California then.

15. #### GW or GWh?

These panels will not be generating and GW at night so they will need to build lots more Gas generation plant to run on those rare cloudy days and all night.

16. One of the comments above mentions "needing to remove the dust". So, given where these canals run, I would think dust would be an issue. How do plan to remove it and keep the efficiency levels high enough?

1. Maybe give Lu-Tze a call?

17. #### Microclimate?

"Because the microclimate adjacent to irrigation canals is somewhat cooler than the surrounding air, TID said the project will also keep solar panels cool, fighting heat-based efficiency losses. "

Not to rain on their parade, but the reason for the cooler microclimate is due to the evaporative cooling effect of the water.

Assuming the cover results in a greatly reduced amount of evaporation, the microclimates will be greatly reduced in size and delta temp.

On the other hand, having slowly moving water somewhat close to the back sides of the PV arrays does create an opportunity: a network of tubing on the backsides, and the occasional PV powered pump, can circulate water from the cooler canal water, chill down the PVs, and deposit the warmer water back into the canal.

Tests would need to be done to see whether the cooling is worth the extra \$ - maybe just have the little pumps run in the summer?

18. #### Stop Watering The Grass!

Anyone who lived in the States will realise a lot of water is wasted because Americans want picture prefect gardens and lawns.

19. ..... Blah blah blah......

Why not just build a quality 2GW nuclear reactor?

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