8 ms·

Solar on Warehouses

76 points by ZeroGravitas 4y ago

bjelkeman-again 4y ago
This would seem to be more common from a business perspective, but apparently it isn’t. This warehouse park, Morgongåva, 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-apotea-goes-solar-608711/ https://renewablesnow.com/news/swedish-online-pharmacy-apote...
- rhdunn 4y ago
  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 4y ago
    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 4y ago
      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 4y ago
        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 4y ago
        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 4y ago
        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.
  - bjelkeman-again 4y ago
    Where I am, Sweden, last year I got 3x the price during the day for my sold electricity, than what I paid at night. So car charging at night and selling electricity during the day.
jpgvm 4y ago
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.
- algo_trader 4y ago
  > 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 4y ago
  > 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.
hijinks 4y ago
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 4y ago
  > 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-kit-30-72kwh-6-server-rack-batteries-with-free-pre-assembled-enclosed-rack-with-door-wheels-busbar-covers/ https://signaturesolar.com/eg4-lifepower4-lithium-batteries-...
  - hijinks 4y ago
    wow thanks.. looks perfect
    - epistasis 4y ago
      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. Could see that pack at half its current price, even in quantities as small as 50kWh. 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 https://www.bnef.com/shorts/16235?e=Insight%20Alert:sailthru
      - hijinks 4y ago
        I guess the idea is just to wait a few years then.
Animats 4y ago
Is rooftop solar used mostly to power air conditioning and lighting cost-effective for large stores?
- epistasis 4y ago
  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.
  - lucb1e 4y ago
    Utilities would have to sell below the raw production cost price before that becomes the case, so that's not very likely to happen.
unixhero 4y ago
Well Duh. Isn't this blindingly obvious?
- Syonyk 4y ago
  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.
  - unixhero 4y ago
    Tha k you for an illumination comment. I learnt some of the intricacies of flat roof mounts. Cheers.
hnburnsy 4y ago
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-offline-last-year-after-fires-explosions.html https://www.cnbc.com/2022/09/01/amazon-took-solar-rooftops-o... https://www.cnbc.com/2019/11/05/tesla-and-walmart-settle-over-solar-rooftop-fires.html https://www.cnbc.com/2019/11/05/tesla-and-walmart-settle-ove... Might have been a Tesla issue in both cases.
- Syonyk 4y ago
  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 4y ago
    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.
    - tomcam 4y ago
      Could you elaborate? I feel like I’m missing something significant. I am imagining people file out, then file back in a few hours later, which seems harmless-ish.
      - scohesc 4y ago
        I would assume downtime in terms of "we're paying all these warehouse workers to stand outside - now we have to send them home and the warehouse is unusable, we don't know if the product inside is salvageable due to potential water damage, etc. etc." Probably a lot easier on the business risk side of things to not have solar on the roof because then the risk for a fire is massively reduced in the first place.
photochemsyn 4y ago
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-ready-building-design-a-summary-of-technical-considerations.html https://www.nrel.gov/state-local-tribal/blog/posts/solar-rea...
- toomuchtodo 4y ago
  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-requirement-7293168/ https://www.jdsupra.com/legalnews/new-jersey-solar-ready-req...
  - cagenut 4y ago
    wow thanks for sharing that link, what a fantastic policy.
- SoftTalker 4y ago
  Yes, and in areas that get snow the roof would need to be strong enough to support the max snow weight plus the weight of the solar gear. I don’t know how much safety factor most buildings have, but many might require additional reinforcement. I know of a city building here where they wanted to install solar and as they got into it realized they would need to hire a steel company to come in and reinforce all the steel roof trusses. That was custom work with welders up on scaffolds and a lot of other work to remove lighting and other fixtures to give them access (and then reinstall it all afterwards). They went ahead with it but with the extra expense it will never be paid back in electrical savings.
gumby 4y ago
By the way, this was the thesis of the unfairly* maligned Solyndra: their collectors were extremely light and encased in tubes. The idea was that they were light and could be anchored without through holes to joists (every through hole in a roof is a leak opportunity for a leak, especially when it’s a retrofit; with the weight of panels on a flat industrial roof you often have to anchor them to a structural member). Also the tube structure permitted airflow so there wasn’t a heat build up nor risk of a “wing” phenomenon. * one political party chose to use Solyndra as a cudgel against a reasonable industrial program. I was always dubious that their thin film approach would pan out, and indeed it didn’t which was what killed the company. But admired their basic thesis, which I still think was sound.
- myself248 4y ago
  For a while, Batteryhookup was selling pallets of Solyndra modules for unbelievably cheap. I think it's difficult to use them on buildings now because the NEC's new rapid-shutdown requirements effectively made decades of solar stuff obsolete (welp so much for the environment), and they're not useful for making solar carports and stuff. But maybe someone with a lot of land...? Anyway, it's a shame. They were a really neat concept and sidestepped a lot of issues that raise the cost of other systems.
powera 4y ago
This misses the point. The limiting factor for solar isn't real-estate. It is inverter production, battery capacity, interconnect, ... basically all of the parts of turning solar energy into grid electricity other than the land for solar panels.
jgelsey 4y ago
The core obstacle is financing - solar traditionally takes a long time to pay back from energy savings, so the financials of solar on warehouses didn't work out. The IRA made it possible to sell the tax credits from solar deployment on warehouse roofs (e.g. https://www.reunioninfra.com/ https://www.reunioninfra.com/) so now solar on warehouse rooftops can make financial sense in many more instances.
Dowwie 4y ago
How are disputes about roof maintenance settled among a roof tenant (the energy company), the tenant of the warehouse, and the owner of the building? If a roof is leaking but repairing the leak will interfere with energy production, how are repairs prioritized? This is an easier situation to handle when there is no energy tenant nor warehouse tenant but rather an owner-occupied who is also the energy provider.
- polygotdomain 4y ago
  It all depends how the leases are written and who's responsible for the solar panels. Since the panels could potentially be the landlord's, warehouse tenant's, or a third party roof tenant's, it could be written up in a variety of ways. The Landloard is going to be the most concerned about it as A) it could potentially effect the base building, and/or B) tenants may take issue with a leak. Chances are the repair would be rolled up into CAM (Common Area Maintenace) charges, which are generally dispersed to the tenant based on an arrangement in the lease (typically % of cost based on % of sq ft of the property). The best chance for it to be handled some other way is if the warehouse tenant and the solar tenant are one in the same. The landlord will still likely be involved, but chances are the tenant will do the repair.
jeffbee 4y ago
When you see something like [1] in the center of a city of 10 million people, that's a lot of potential for energy generation. And the great thing about putting a ton of panels in the middle of the city is it tends to avoid all the transmission issues we have with siting PV facilities way out in the desert. 1: https://www.google.com/maps/@34.0297809,-117.9823821,3248m/data=!3m1!1e3 https://www.google.com/maps/@34.0297809,-117.9823821,3248m/d...

76 points by ZeroGravitas 4y ago

This would seem to be more common from a business perspective, but apparently it isn’t. This warehouse park, Morgongåva, 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-apotea-goes-solar-608711/ https://renewablesnow.com/news/swedish-online-pharmacy-apote...

rhdunn 4y ago
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 4y ago
  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 4y ago
    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 4y ago
      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 4y ago
        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 4y ago
        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.
- bjelkeman-again 4y ago
  Where I am, Sweden, last year I got 3x the price during the day for my sold electricity, than what I paid at night. So car charging at night and selling electricity during the day.

jpgvm 4y ago

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.

algo_trader 4y ago
> 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 4y ago
> 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.

hijinks 4y ago

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 4y ago
> 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-kit-30-72kwh-6-server-rack-batteries-with-free-pre-assembled-enclosed-rack-with-door-wheels-busbar-covers/ https://signaturesolar.com/eg4-lifepower4-lithium-batteries-...
- hijinks 4y ago
  wow thanks.. looks perfect
  - epistasis 4y ago
    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. Could see that pack at half its current price, even in quantities as small as 50kWh. 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 https://www.bnef.com/shorts/16235?e=Insight%20Alert:sailthru
    - hijinks 4y ago
      I guess the idea is just to wait a few years then.

Animats 4y ago

Is rooftop solar used mostly to power air conditioning and lighting cost-effective for large stores?

epistasis 4y ago
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.
- lucb1e 4y ago
  Utilities would have to sell below the raw production cost price before that becomes the case, so that's not very likely to happen.

unixhero 4y ago

Well Duh. Isn't this blindingly obvious?

Syonyk 4y ago
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.
- unixhero 4y ago
  Tha k you for an illumination comment. I learnt some of the intricacies of flat roof mounts. Cheers.

hnburnsy 4y ago

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-offline-last-year-after-fires-explosions.html https://www.cnbc.com/2022/09/01/amazon-took-solar-rooftops-o... https://www.cnbc.com/2019/11/05/tesla-and-walmart-settle-over-solar-rooftop-fires.html https://www.cnbc.com/2019/11/05/tesla-and-walmart-settle-ove... Might have been a Tesla issue in both cases.

Syonyk 4y ago
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 4y ago
  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.
  - tomcam 4y ago
    Could you elaborate? I feel like I’m missing something significant. I am imagining people file out, then file back in a few hours later, which seems harmless-ish.
    - scohesc 4y ago
      I would assume downtime in terms of "we're paying all these warehouse workers to stand outside - now we have to send them home and the warehouse is unusable, we don't know if the product inside is salvageable due to potential water damage, etc. etc." Probably a lot easier on the business risk side of things to not have solar on the roof because then the risk for a fire is massively reduced in the first place.

photochemsyn 4y ago

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-ready-building-design-a-summary-of-technical-considerations.html https://www.nrel.gov/state-local-tribal/blog/posts/solar-rea...

toomuchtodo 4y ago
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-requirement-7293168/ https://www.jdsupra.com/legalnews/new-jersey-solar-ready-req...
- cagenut 4y ago
  wow thanks for sharing that link, what a fantastic policy.
SoftTalker 4y ago
Yes, and in areas that get snow the roof would need to be strong enough to support the max snow weight plus the weight of the solar gear. I don’t know how much safety factor most buildings have, but many might require additional reinforcement. I know of a city building here where they wanted to install solar and as they got into it realized they would need to hire a steel company to come in and reinforce all the steel roof trusses. That was custom work with welders up on scaffolds and a lot of other work to remove lighting and other fixtures to give them access (and then reinstall it all afterwards). They went ahead with it but with the extra expense it will never be paid back in electrical savings.

gumby 4y ago

By the way, this was the thesis of the unfairly* maligned Solyndra: their collectors were extremely light and encased in tubes. The idea was that they were light and could be anchored without through holes to joists (every through hole in a roof is a leak opportunity for a leak, especially when it’s a retrofit; with the weight of panels on a flat industrial roof you often have to anchor them to a structural member). Also the tube structure permitted airflow so there wasn’t a heat build up nor risk of a “wing” phenomenon. * one political party chose to use Solyndra as a cudgel against a reasonable industrial program. I was always dubious that their thin film approach would pan out, and indeed it didn’t which was what killed the company. But admired their basic thesis, which I still think was sound.

myself248 4y ago
For a while, Batteryhookup was selling pallets of Solyndra modules for unbelievably cheap. I think it's difficult to use them on buildings now because the NEC's new rapid-shutdown requirements effectively made decades of solar stuff obsolete (welp so much for the environment), and they're not useful for making solar carports and stuff. But maybe someone with a lot of land...? Anyway, it's a shame. They were a really neat concept and sidestepped a lot of issues that raise the cost of other systems.

powera 4y ago

This misses the point. The limiting factor for solar isn't real-estate. It is inverter production, battery capacity, interconnect, ... basically all of the parts of turning solar energy into grid electricity other than the land for solar panels.

jgelsey 4y ago

The core obstacle is financing - solar traditionally takes a long time to pay back from energy savings, so the financials of solar on warehouses didn't work out. The IRA made it possible to sell the tax credits from solar deployment on warehouse roofs (e.g. https://www.reunioninfra.com/ https://www.reunioninfra.com/) so now solar on warehouse rooftops can make financial sense in many more instances.

Dowwie 4y ago

How are disputes about roof maintenance settled among a roof tenant (the energy company), the tenant of the warehouse, and the owner of the building? If a roof is leaking but repairing the leak will interfere with energy production, how are repairs prioritized? This is an easier situation to handle when there is no energy tenant nor warehouse tenant but rather an owner-occupied who is also the energy provider.

polygotdomain 4y ago
It all depends how the leases are written and who's responsible for the solar panels. Since the panels could potentially be the landlord's, warehouse tenant's, or a third party roof tenant's, it could be written up in a variety of ways. The Landloard is going to be the most concerned about it as A) it could potentially effect the base building, and/or B) tenants may take issue with a leak. Chances are the repair would be rolled up into CAM (Common Area Maintenace) charges, which are generally dispersed to the tenant based on an arrangement in the lease (typically % of cost based on % of sq ft of the property). The best chance for it to be handled some other way is if the warehouse tenant and the solar tenant are one in the same. The landlord will still likely be involved, but chances are the tenant will do the repair.

jeffbee 4y ago

When you see something like [1] in the center of a city of 10 million people, that's a lot of potential for energy generation. And the great thing about putting a ton of panels in the middle of the city is it tends to avoid all the transmission issues we have with siting PV facilities way out in the desert. 1: https://www.google.com/maps/@34.0297809,-117.9823821,3248m/data=!3m1!1e3 https://www.google.com/maps/@34.0297809,-117.9823821,3248m/d...