this post was submitted on 28 Jul 2024
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Covering large parking lots with solar panels is an idea that goes back decades but in America at least it's an idea that has never really taken off.

What is the reason for that? Is it due to the overall cost or is there something else that keeps Walmart, Target, Costco, Sams Club, Malls, etc. from covering their parking lots with these panels and selling the power?

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[–] [email protected] 2 points 1 month ago

In Central Orange County, CA solar commonly seen covering parking at schools, transit hubs and government buildings. Less common on commercial lots but there are some. As renewable generation is helpful in attaining Leed certification it will become more common everywhere solar is practical.

[–] [email protected] 2 points 1 month ago

It’s happened in some places. The local high school and train station parking lots where I live have them.

[–] [email protected] 1 points 1 month ago

In addition to what has been said already, in many places the cost to upgrade the electrical service to the building to handle the amount of power that could be generated can be as much or more than all the other costs combined. So now the building operators are looking at millions in cost with a potentially 30 year payback period. It just doesn't make sense at that point.

[–] [email protected] 7 points 1 month ago (1 children)

I believe, this is because it's not yet a business model (nor a legal requirement). The first questions is, who even owns the lot and who has to power to make changes? Then, who gets to use the power output? Do you use it on-site or feed to grid? Do the local utility work with you or against you? (Hint: You are competitors now and running a grid is not free.)

That's just speculation, why solar-covered parking lots are not yet build much. The idea totally makes sense. It will probably take a either a startup company that figures out how and sells the solutions to the owners or a local government pushing for more solar.

To those saying, it's cheaper to build on a roof. Maybe, then do the roof, first, if it's feasible. Is it cheaper to build on undeveloped land or farm land? Maybe, if you live in the middle of nowhere or drive a significant distance to do your shopping. Still, plenty of opportunity to build over parking lots.

[–] [email protected] 3 points 1 month ago* (last edited 1 month ago) (1 children)

I've seen other discussions come to the conclusion that rooftop solar on a warehouse size building would be more expensive than the whole infrastructure of parking lot shades. They said that the entire structure would need reinforcement. Not a problem on new buildings, they can be designed to take the extra weight from the start

[–] [email protected] 1 points 1 month ago

A girl I dated works for a company that has a "rubble site," they essentially tried solar on the roof, and it eventually collapsed the roof in and ruined the entire building.

[–] [email protected] 5 points 1 month ago

I think it's because, "drill baby, drill!" attitudes.

[–] [email protected] 7 points 1 month ago (1 children)

There are some parking lots like that around here, though not many. Obviously expense is a large part of it. Photovoltaics get cheaper all the time, but there is all the other gear (inverters, transmission lines), plus the construction costs. Web search for solar parking lot or solar canopy finds a fair amount of data.

I do think solar off-grid is now economically feasible for a modest home. It's easier for a DIY homeowner than for a commercial operator to control costs by scrounging.

[–] [email protected] 2 points 1 month ago (2 children)

Wouldn't all of those costs be offset by the power generated? At least, the solar power would reduce the stores' draw from the grid. At most (depending on the size of the parking lot) the store would feed the grid on sunny days.

It seems to me that investing in the panel canopies, controllers, and modified grid connection would soon pay for itself and then fund the installation of the same for the next store.

[–] [email protected] 2 points 1 month ago

If there was truly money to be made, people would be making it. Never underestimate the dedication of opportunists.

So if it's not happening, it's because the dollars aren't there.

Second question should be, why aren't the dollars there? Is it artificial limitations, like laws about power generation? Is it the cost of the supplies only? We understand that, we can fix the problem.

[–] [email protected] 2 points 1 month ago (1 children)

You have to do the math. That solar canopy ends up costing around $5 per watt to install, apparently. WIth 0.3 solar constant (counting some other factors) that's 2.6 KWH/year per watt of solar, maybe 30 cents at industrial rates. So 15-ish years to pay off. Of course you can change the parameters around and do the math differently. Also hmm, 5% interest on the $5 is $.25 so that kills most of the 30 cents you get back in electricity. Scale this up to a 1 megawatt ($5 million) array for a Walmart sized parking lot and it's not so attractive. It was better a few years ago when interest rates were near zero.

[–] [email protected] 1 points 1 month ago

There's also leverage to make a bulk deal for the panels and installation because it's Walmart or whatever, rising cost of electricity (depending on location) shortening the payoff time, grants and tax breaks for renewable energy, the value of a green energy initiative for a PR push, attracting more customers because their cars can park in the shade.

If they have to design custom canopies, wiring solutions, etc, it would add to the costs a lot.

[–] [email protected] 5 points 1 month ago

Pretty popular in Phoenix

[–] [email protected] 13 points 1 month ago

I wish, we could at least make parking lots not pitch-black. They absorb so much heat in the sun, which makes them unpleasant to walk across and of course adds to cities being overly hot in general.

Two local shops here have their parking lots out of light gray paving stones, which is so much nicer. I'm guessing, they got forced to pave, so that rain water can drain, which is of course also quite a good idea...

[–] [email protected] 2 points 1 month ago* (last edited 1 month ago)

My grocery store has some. I don't know if it's actually economical for them in terms of power, but the shade for the car is nice.

[–] [email protected] -1 points 1 month ago (1 children)

Solar panels are very fragile; the weight of a car driving over them every day would cause them to break really quickly, not too mention the layer of rubber and dirt that will accumulate on them. I imagine the cost of installing and replacing them is also much higher than laying down a regular road surfice.

If they wanted to invest heavily in solar panels, why wouldn't they just either put them on top of the shop building itself, or build a lightweight roof over the parking lot and put them on that?

[–] [email protected] 10 points 1 month ago (1 children)

Pretty sure they mean cover as in like a roof.

[–] [email protected] 3 points 1 month ago

Ah, right. My bad. For some reason my head was stuck on those solar roadway thingies.

[–] [email protected] 20 points 1 month ago (1 children)

Basically solar panels need structural support.

To cover a parking lot, you must build the supports from scratch. To cover an existing rooftop, the structure’s already there.

It’s slightly more complicated but that’s the basic reason.

[–] [email protected] 8 points 1 month ago

Supports are nothing compared to the electrical infrastructure needed to actually use the solar power. Adding solar to a commercial 3 phase switchgear is a massive headache.

[–] [email protected] 50 points 1 month ago (1 children)

One of the Costco locations in Albuquerque has a solar covered parking lot. Inside they have a meter showing how much of their used electricity is from the solar.

[–] [email protected] 1 points 1 month ago

Yeah, places with lots of sunshine are more likely to do stuff like this. I recently visited Tucson, AZ, and the amount of solar panel coverage all over the place was very impressive. Both rooftops and parking lots.

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