Thread

What California is learning from solar panels built over irrigation canals

372 points · 744 comments · Jtsummers

nbf_1995 · 1790086541 · focus · HN ↗
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.
1. walrus01 · 1790110178 · focus · HN ↗
  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.
  1. throwaway2037 · 1790163080 · focus · HN ↗
    > 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] <a href="https://www.makemyhousegreen.com/green-guides/can-solar-panels-withstand-heavy-winds" rel="nofollow">https://www.makemyhousegreen.com/green-guides/can-solar-pane...
    jyounker · 1790179378 · focus · HN ↗
    > I'm surprised by this comment. (Is this area known for strong winds?)
    Areas of the central valley are legendary for strong winds. A large stretch of the aqueduct (200km?) runs along the valley's West edge. So does the interstate highway I5.
    The I5 has frequent high wind advisories. In the area around Pacheco Pass there are frequently gusting cross winds between 55 and 70km per hour. I use the I5 as my reference here, because I have spent many hours of my life driving it in these conditions.
    > If your comment is true, wouldn't all warehouses using the same type of standard "bents" also be very expensive?
    What makes you think building a warehouse in earthquake country is cheap?
    > 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.
    The statement about solar panels making very good sails obviously true. Everything thin and flat makes a good sail.
    PV panels don't go flying away because people spend a lot of money attaching them to the ground. They're expensive systems, and any installer that didn't make sure they were bolted down effectively, would be sued out of business after the first windstorm.
    PaulDavisThe1st · 1790179876 · focus · HN ↗
    You can meet code requirements on rocky ground with relatively small concrete block anchoring systems. The cost of the blocks plus the metal pipe structure for a ground mount system is typically 10% or so of the total system install.
    If you're on excavatable ground, the cost goes up a little (paradoxically, way more concrete is required to meet code).
    There are also companies do this sort of thing with earth anchors/helical ground screws, which are VERY fast to install, but tend to cost more than the concrete. Nice that they can be (re)moved, though.

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