[HN Gopher] Solar on Warehouses ___________________________________________________________________ Solar on Warehouses Author : ZeroGravitas Score : 30 points Date : 2023-04-23 19:52 UTC (3 hours ago) (HTM) web link (environmentamerica.org) (TXT) w3m dump (environmentamerica.org) | Animats wrote: | Is rooftop solar used mostly to power air conditioning and | lighting cost-effective for large stores? | epistasis wrote: | It's likely far cheaper than buying the electricity from the | grid, but it will depend on local commercial electricity rates. | Utilities usually have to set up pretty perverse schemes in | order for solar to not be an economical choice. | unixhero wrote: | Well Duh. Isn't this blindingly obvious? | Syonyk wrote: | The short answer is "No, but it sounds obvious if you don't | know much about it." Similar to Solar Roadways - the less you | know about solar or roads, the better the idea sounds. The half | mile gouge down a road near me from a trailer coming free and | riding on the chains until they noticed and pulled over isn't a | big deal on asphalt (they'll fill it next time they chipseal | it), but it would be millions of dollars worth of damage to | solar road tiles. Among many other issues. | | It's the sort of thing that sounds obvious if you don't know | much about the field, and the more you learn, the more things | you realize make it a royal pain in the rear to deal with | unless the structure was designed with solar in mind - and even | then, it's a pain compared to a ground mount array somewhere | close. | | For a big membrane roof, you don't want a ton of penetrations - | which means ballasted mounts. Except they weigh a lot, and the | roof usually isn't built to support them on top of the required | weight for rain/snow/etc. So you need to screw the stuff down | to the roof, but now you have tons of penetrations in a | membrane roof, and if anyone tells you they can do thousands of | those without a single leak, they're full of crap. | | As I talked about in another comment, you can't just run high | voltage DC strings on a roof - you need per panel electronics, | so the normal solution is microinverters, but now you're | pushing 240V around instead of the 1500V you can run on ground | mounted strings, so wiring cost is higher, and Enphase sure | makes their money off their handout in the NEC 2017. | Reliability of microinverters remains an open question as well. | They're not exactly in a good spot for electronics. | | You've got open area, you've got a high current | interconnection, but the rest of it is just a set of thorny | problems that makes it quite a bit more expensive than ground | mount. | hnburnsy wrote: | Both Amazon and Walmart have pulled back on solar due to fires | and electrical issues... | | https://www.cnbc.com/2022/09/01/amazon-took-solar-rooftops-o... | | https://www.cnbc.com/2019/11/05/tesla-and-walmart-settle-ove... | | Might have been a Tesla issue in both cases. | epistasis wrote: | Everybody I know that used Tesla for solar regrets it. Cheap | stuff, but you end up paying for it in the end. | bufferoverflow wrote: | When we installed solar, Tesla's was the most expensive out | of all the proposals. Their solar roof looks very very cool, | but it's definitely not "cheap stuff". | epistasis wrote: | Never heard of anything like that, but most of my | experience is from 2+ years ago. Is your install recent? | Are you sure they were equivalent proposals? If you add | storage, that's no longer just solar, and their storage | offerings are far more expensive than others. | | I couldn't find a local solar installer that wanted to use | the type of cheap inverters that Tesla wanted to use. My | neighbor has to have Tesla come out about once a year to | fix issues. | Syonyk wrote: | I've no idea why you're being downvoted, because it _is_ a very | real issue. You don 't have to burn down many warehouses with | solar before insurance companies start to have a lot of hard | questions and rate increases. In tens of thousands of | connections, it doesn't take a high failure rate on components | before you've got something high resistance. | vasco wrote: | And if you have to evacuate a huge warehouse even once a year | due to these fires, it immediately is not worth it for the | operator. | [deleted] | photochemsyn wrote: | Structural design issues are the problem as other comments note. | If you haven't designed the roof from the beginning to have a | fairly weighty additional structure attached on top, then all | kinds of other problems can arise, from leaks to wind-related | loads and so on. | | Over the long term, it becomes something building codes need to | implement, similar to electrical wiring and plumbing standards: | | https://www.nrel.gov/state-local-tribal/blog/posts/solar-rea... | toomuchtodo wrote: | NJ has code that requires structural loading on new warehouses | to be able to support solar on 40% of the roof. It's just a | matter of getting this into code as soon as possible, so new | buildings are solar ready as old warehouse space is eventually | retired at EOL. | | https://www.jdsupra.com/legalnews/new-jersey-solar-ready-req... | bjelkeman-again wrote: | This would seem to be more common from a business perspective, | but apparently it isn't. This warehouse park, Morgongava, near | Uppsala in Sweden has at least 2.5 MW installed and installing | more. This one of their buildings. | | https://renewablesnow.com/news/swedish-online-pharmacy-apote... | rhdunn wrote: | It's interesting that they are selling the excess to the local | supplier as they will be able to offset the cost faster, and | start making a profit from it sooner. That is, the point at | which the amount of money saved from not paying for the | electricity and the amount gained from selling the excess | balances the cost for the installation. | PaulKeeble wrote: | This happens in residential solar a lot. During the | Spring/Summer/Autumn you will produce 1.5x - 2x what you | consume on any given day but the peak of the power all comes | at 9-10am to 2-3pm. You need large amounts of battery to move | that power to cover the house for the other 2/3 of the day | and that adds a lot of cost and is often similar price to the | solar array. | | One of the best ways to deal with the problem is selling it | back to the grid but how that is done vastly changes the | payback period. Some states do it as a unit exchange so you | sell 1KWh to them then you get that back later when you want | it for no cost. Whereas many do a sale price with a price | half or worse. Which price you can get for that power and | whether its following wholesale (which tends to be peak early | evening and be more during the day than night) can | drastically change the pay off period. | ajsnigrutin wrote: | So, power when you're not at home, the house is empty, it's | warm, and your electric car is with you at work, and no | power at night, when you need to cook, heat and charge your | car. | Syonyk wrote: | Yup. | | This is one of the reasons I've argued in favor of "slow, | at work charging" as the default for EVs. If you put in a | bunch of 240V/16A chargers (3.8kW), as people show up in | the 8-9 timeframe, they start charging, and the bulk of | the charging happens in the ~10AM-2PM window that's after | the morning peak, as solar is ramping up, and before the | afternoon cooling/evening peak. You can even restrict the | chargers a bit more in the morning if needed until off | peak, though I'm not sure this is worth much over just | using dumb chargers that are cheap to install. An average | 35 miles a day driving (in the US) requires ~10kWh, so | you've got a few hours of charging that can swallow an | awful lot of power during the time nothing else is using | much of it. | | It's far better than having to deal with evening and | overnight charging. | ajsnigrutin wrote: | But for that you need every parking space in every office | building equipped by a charger, and somehow have the grid | strong enough to power all that from solar cells which | need to be installed somewhere further away, since an | average office building does not have enough roof space | to charge all those cars. The hours you mentioned are | usually spent at work and the cars are parked there (and | not at home). | Syonyk wrote: | Who said every parking space? I didn't. Even at the | coastal FAANG offices, EVs are still the minority. And | not everyone will be charging every day. It's still fine | to have a lot of non-charging spots - some people have | short commutes and can be perfectly fine charging for | 8-9h once a week (at 3.8kW, that's around 100 miles in 8h | of charging). My experience from the early to mid teens | is that the Leafs fought for charging, and the longer | range BEVs charged if they could, and otherwise didn't | get in the (damned near literal) fistfights over | charging, but if someone showed up early, they'd plug in | for the day. | | If you look at grid demand curves, that "late morning, | early afternoon" time spot is the mid-day low for _most_ | grids. So there 's excess capacity anyway, and if you | look at the "duck curve" sort of graphs, there's a ton of | solar on the grid then anyway. This is only increasing | with time. So we may as well make decent use of it. | | You could also have some lower power, 1440W charger slots | (15A @ 120V) for those who don't need much power - it'll | still make up an average day's driving in 8h of charging, | but since it's literally the same wiring cost and such to | run 120V as 240V, I'm not sure you gain much with it, and | it's now perfectly valid for chargers to coordinate | regarding total circuit demand anyway. | jpgvm wrote: | Has anyone done more detailed numbers on costing of roof mounted | installation vs just putting utility scale solar on the ground? | | I would have thought if the economics were super favourable this | would already be happening by now. | | To me it -seems- like a great idea but while I'm pretty versed in | solar for home scale (diy off-grid setups etc) I have no idea how | the numbers bear out for this install size, grid connection, etc. | notatoad wrote: | we massively under-value land in most cases, which is the | reason that activists push for solutions like this. | | utility scale solar on the ground is economically better, if | you're looking at "the numbers". but utility scale solar | probably means repurposing farmland, because that's the | cheapest land that has enough infrastructure built up around it | to make a utility install easy. and repurposing farmland to | build solar isn't a clear win in terms of overall societal | benefit. | epistasis wrote: | Converting farm land into solar, or even fallow land, seems | like a massive societal benefit. Most farmland is | fantastically unproductive, used for excess corn, soy, or | sugar that we struggle to find uses for. | | Taking even a fraction of the land used for ethanol and using | it for solar would give us enough energy to power the US. And | the ethanol business is a complete make work program. | Syonyk wrote: | > _... but utility scale solar probably means repurposing | farmland..._ | | Great. Let's start by repurposing the land that grows the | corn we turn into ethanol at somewhere around or below unity | EROEI, as a political handout to the midwestern states. | "Burning a megajoule of diesel, to grow enough corn to make | something slightly less than a megajoule of gasoline," is | _not_ a winning solution to any problem but "How to best | hand money to states that happen to have early Presidential | primaries." It's not a bad gig for Iowa (I lived there for a | decade), but neither is it a particularly good use of energy, | fossil fuels, or money. Let's put solar up there, and work | out. | | Once we've gotten rid of the ethanol debacle, we can see | where things are and discuss from that point, but there is a | _lot_ of farmland right now that doesn 't grow human or | animal food, it grows corn that we process rather | inefficiently into ethanol. | algo_trader wrote: | > Has anyone done more detailed numbers.. | | This is usually under "C&I" (commercial and industrial), as | opposed to rooftop or utility scale. | | Try Lazard LCoE report, NREL Solar reports, IRENA renewables, | or use google. | Syonyk wrote: | > _Has anyone done more detailed numbers on costing of roof | mounted installation vs just putting utility scale solar on the | ground?_ | | You're far cheaper on the ground, for a variety of reasons (at | least in most areas). A good ground mount install should be | able to come in around $1/W, and you'll have a hard time | getting roof mount below closer to $1.50 or $2/W installed, and | if you get $2/W, you're getting a great deal. | | If you're doing the work yourself, ground mount for around $1/W | is doable (including the frames), but roof mount I've not been | able to get below about $1.25/W, and that's hard - $1.50/W is | more typical. | | The main difference is that the roof mount system requires | rapid shutdown on (in NEC 2017 and later) every panel, and | you're limited to 600V (though with rapid shutdown | requirements, this is less relevant). For a ground mount system | that's isolated away from random people (fenced area), you can | run up to 1500VDC to the inverters, and this rather reduces | your costs in wiring. You also don't need rapid shutdown, so | you can just run strings of panels (20 or 25x 72 cell panels in | series, depending on the environment). | | Also, if those strings have an arc fault somewhere, you're not | going to burn up much that matters for a big ground mount | install. You'll cook a couple panels, and that's about it. A | fire under the panels on a warehouse is a much bigger deal. | | The main problem you run into with warehouses, though, is that | there's just no good option for mounting. For a flat roof, | they're generally built to exactly the loading requirements for | the area. You don't have the spare PSF capacity for a ballasted | mount, which means that assuming you've got the weight rating | for the panels, you're looking at a _lot_ of roof penetrations | on a flat membrane roof to hold stuff down - and the odds of | some of those leaking is basically 100%. | | Plus it's a royal pain to work on roof mount systems. | jpgvm wrote: | Thanks for the great writeup! The root loading makes perfect | sense when you think about it and in that context makes the | equation much more expensive unless the warehouse could | feasibly use all the power generated (which seems unlikely). | hijinks wrote: | ya till solar hits a tipping point like it is in California right | now. Then the utilities want to set a flat rate based on wages to | stay connected to the grid. | | This will 100% work but we also need battery tech to hit like | 250-300 a kwh for storage is my magic number to get a 40-50kwh | backup and detach from the grid. | krasin wrote: | > we also need battery tech to hit like 250-300 a kwh for | storage is my magic number to get a 40-50kwh backup and detach | from the grid. | | Here you go, a 30kWh 48V battery for $9k ($300/kWh): | https://signaturesolar.com/eg4-lifepower4-lithium-batteries-... | hijinks wrote: | wow thanks.. looks perfect | epistasis wrote: | The storage market has been revolutionized in the past few | years thanks to LFP chemistries, and it's only going to get | better soon. There are massive new US production facilities | coming online, and Bloomberg is estimating that US cell | costs will be $83/kWh, just a few dollars more than Chinese | costs. Add in the IRA tax credits, and the cost will be | less than $50/kWh. Packs will be more expensive than cells, | of course, but the future looks very rosy. I always chuckle | when I encounter the sweet summer children that think that | battery tech is stagnant... | | (Subscription required) https://www.bnef.com/shorts/16235?e | =Insight%20Alert:sailthru ___________________________________________________________________ (page generated 2023-04-23 23:00 UTC)