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.

▲ defrost 12 minutes ago | parent | next [-]

The UK has covered some water reservoir with floating PV panels.

The article mentioned trialling several systems for covering California canals, I didn't see "floating" mentioned, although:

  Project Nexus tests not one, but three different solar canal models. 

  ... accordion-like retractable panels are positioned low across the narrow canal, ready to roll up at a moment’s notice.

might come close.

Floating panels have the issue of having to flex and perhaps bottom out (if water diverts to parallel canal for maintenance) on a dry canal - but there's less need for heavy steel trusses and a lower wind profile.

▲ dragonwriter 2 hours ago | parent | prev | next [-]

> Putting the PV panels on empty bare land at a height people can walk around and work with would be considerably less costly.

What empty, bare land?

If its really empty and bare, there is a reason for it and that reason is probably a problem for building and maintaining PV, and otherwise you have to add the loss of the alternative uses of the land to the cost.

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walrus01 an hour ago | parent | next [-]

In the context of California, land that is not suitable for agriculture because it can't be irrigated, even though it's flat and somewhat accessible by road. California has plenty of it, go drive around near Twenty Nine Palms and you'll see it...

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pixl97 an hour ago | parent | next [-]

And the moment you start building large structures on it everyone and their dog is going to show up and NIMBY it.

	▲	asdff 34 minutes ago \| parent [-]
		Spoken like someone who has never been to the mojave. This is the home to the largest wind turbine installation in the country. But again, if the worry is the solar panels acting like sails, probably not a great site given that wind.

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asdff 35 minutes ago | parent | prev [-]

Now measure the wind at twenty nine palms

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mlmonkey 2 hours ago | parent | prev [-]

> What empty, bare land?

Have you been to Death Valley, my friend? All of Southeastern California is empty, barren land. Death Valley, Mojave Desert, etc.

	▲	asdff 36 minutes ago \| parent [-]
		Guess how fast the wind blows across the surfaces. There's a reason why these places currently host massive wind turbine farms.

▲ asdff 35 minutes ago | parent | prev | next [-]

You know where the wind blows really damn hard in California? Virtually any open field you can imagine putting these otherwise. Mojave for example is damn windy. That is why they currently host massive wind installations there.

	▲	walrus01 26 minutes ago \| parent [-]
		I'm well aware of that, thanks. Ground mount PV is still going to be considerably less costly than this. Partly because it's easier to build, partly because it has many competing companies that sell the basic aluminum rail/hot dip galvanized steel mounting pieces, partly because you can use relatively low cost contractors to do work like install its footings and bolt it together. Having stuff at ground level that can be reached by people on foot or on a 6 foot step ladder also makes doing the electrical work a lot less costly.

▲ AngryData an hour ago | parent | prev [-]

To my eye if you were putting up a few hundred or more of those steel structures, and it didn't require a redesign of the canal retainment around it, it could be built quite economically.

Every extra pylon structure built, especially the first dozen, will be cheaper and easy to produce and install.