Yet another Hacker News

What California is learning from solar panels built over irrigation canals

31 points Jtsummers 17 hours ago 19 comments

nbf_1995 6 hours ago | parent

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.

ch4s3 24 minutes ago | parent

Or better yet, invest in pipes.

imoverclocked 23 minutes ago | parent

Canal sized pipes?

annoyingnoob 19 minutes ago | parent

According to AI, that pipe would only need to be 43 Feet in diameter, only 43 feet wide. Pretty sure they have that at Home Depot.

jimt1234 12 minutes ago | parent

I'm sure it could be done, but it would cost a fortune. My understanding is the canals were built to distribute water to farmers, and conservation/evaporation wasn't really much of a consideration because California had plenty of water back then.

BTW, I used to swim in those same canals around Modesto and Turlock as a kid. So gross.

coryrc 15 minutes ago | parent

What's the lifetime of a "cheap shade"? And the cost to renew it over the same lifetime? And the cost of paying for other land?

... likely less than the ~$13/W this cost to install, but that included NRE for three different styles of panel mounting. Standardizing would cut costs significantly.

BurningFrog 14 minutes ago | parent

There are solutions like this to most of Californias big intractable problems, and they're not done because some California laws and/or regulations make it impossible.

This is one reason I now live in Nevada, where pretty much everything is legal...

walrus01 12 minutes ago | parent

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.

mindcandy 5 minutes ago | parent

My understanding is that "The best reasoning they give" is the entire point. It such a huge issue that it drowns out all of the valid but smaller issues you are pointing out. And, the benefit to the water is just a bonus.

sophacles 4 minutes ago | parent

Power lines are made of aluminum and steel.

I seriously doubt that you can chain even 1/4 mile of panels together without destroying things. Thats already puting thousands of volts and hundreds or thousands of amps through the silicon. If you are making it all parallel you still need wiring between panels that can handle that. The cabling doesn't go away, it just moves.

Wouldn't there still be supports in a feild of solar panels? Are you sure that those supports + the supports for the shade material are going to be less material than the supports for this?

Most shade material wears out pretty quickly. Will their replacement result in more expense, more waste, etc than just putting the solar panels?

Shade material is generally pretty heavy, is it really going to need significantly less robust support? Weight aside, how much of the load those supports are rated for is due to the actual weight of the panels, and how much is for forces from things like wind?

exabrial 16 minutes ago | parent

oof, that is a crap ton of steel. I doubt those panels will ever harvest enough energy to offset the energy use to produce both the cells and supports.

I imagine with cells in that configuration, lifting wind loads are significant which is why it's overbuilt like that.

Perhaps some laminate timber for the cross supports?

Lastly, the US has got to start eating seasonally. The water problem in the southwest is all agriculture: people want to grow baby spinach in January. Unless we figure out a way to create a crap ton of energy cheaply so we can supply industrial sized flows without worrying about the energy cost, we use far more water than we should in California and Arizona.

shagie 9 minutes ago | parent

Electricity is incidental (and a nice benefit) to the goal of "reduce evaporation of water from the irrigation canal and improve water quality".

> > The duo went on to start Solar Aquagrid, an advocacy firm dedicated to reimagining aging canals, and partnered with the Turlock Irrigation District, UC Merced and the California Department of Water Resources to cover small sections of Turlock’s canals with solar panels. The new “solar canal” provides shade to limit evaporation and generates power all in one neat package. They call it Project Nexus, and it operates at the intersection of the state’s need for clean water and energy.

> ...

> 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.”

> When it comes to algae, the panels helped. “Last year when we drained the canal at the end of the irrigation season, there was a physical line on the sun side of the canal that had algae growth and then not algae growth from where the shade was,” Weimer said.

That it's green energy and can help supply the power demand is a bonus.

hn_throwaway_99 8 minutes ago | parent

> I doubt those panels will ever harvest enough energy to offset the energy use to produce both the cells and supports.

While I agree those steel supports are large, that seems insanely wrong to me, but not an expert so curious if someone with more info could comment.

baxtr 15 minutes ago | parent

What is it learning?

seltzered_ 10 minutes ago | parent

When you read lines like "California’s extensive network of canals and aqueducts is the lifeblood of the state, providing clean water to populous cities and expansive farms that wouldn’t otherwise have it." you have to ask how we ended up with these canal systems, what the tradeoffs are in a landscape setup this way rather than one where water infiltrates the ground and stays hydrated, and who owns water rights in California.

Build Soil has some interesting threads on this:

- https://bsky.app/profile/buildsoil.bsky.social/post/3lmeddjd...

- https://bsky.app/profile/buildsoil.bsky.social/post/3mkzybkk...

(note: I'm not trying to totally bash the solar panel project nor some of the key figures involved who've done great work like Dustin Mulvaney, but do think we should think about how we ended up here)

whalesalad 5 minutes ago | parent

I thought this was a pretty awesome video to provide the lore on how water got to Southern California. Growing up in Pasadena I heard the name Mulholland and Eaton (as in canyon) all the time but never realized they were so instrumental in the founding of the city and all the wild shenanigans that went into getting the water from up north to LA.

https://www.youtube.com/watch?v=x-RGL15Skuo