Clean Power

Published on February 21st, 2016 | by Guest Contributor


62,000 MW of Solar Power Capacity Possible on US Big Box Stores

February 21st, 2016 by  

Originally published on Sustainnovate.
By Henry Lindon

Report: Big Box Stores In US Could Host 62.3 GW Of Solar PV Capacity

Americana “big box” stores could host around 62.3 gigawatts (GW) of rooftop solar photovoltaic (PV) capacity — enough to generate enough electricity to provide for the equivalent needs of roughly 7 million US households — according to a new report from Environment America Research & Policy Center.

Considering that big box stores, grocery stores, etc, use roughly 5% of all of the electricity used in the US — and also the fact that there’s more than 4.5 billion square feet (cumulatively) of rooftop space on these buildings that is well suited to solar energy installations — such an approach to solar energy development has a lot of potential.

The potential is there for the US to meet roughly a quarter of its electricity needs through rooftop solar PV alone, according to the National Renewable Energy Laboratory (NREL).

Here are some further details via a new press release:

* Installing 62.3 GW of clean solar power on America’s big box stores and shopping centers would reduce global warming pollution by nearly 57 million metric tons annually — equivalent to taking nearly 12 million passenger vehicles off the road.

* Producing electricity on rooftops, close to where the electricity will be used, reduces losses that happen during electricity transmission — losses that totaled an estimated 203 million megawatt-hours (MWh), or 5% of electricity sales in 2012. Solar power also reduces costs by producing the most electricity during the sunniest parts of the day, which are often when demand for electricity peaks. This helps utilities avoid firing up expensive, peaking power plants to meet the temporary rise in demand.

* Electricity produced by rooftop panels on big box stores and shopping centers could offset the annual electricity use of these buildings by 42%, saving these businesses $8.2 billion annually on their electricity bills.

* The 10 big box companies with the largest amount of retail space in the US — Walmart, Target, Home Depot, Lowe’s, Sears Holdings (including Sears and KMart), Macy’s, JC Penney, Kohl’s, Costco, and TJX (including Marshall’s and TJMaxx) — have enough rooftop space to host approximately 17 GW of solar capacity on their retail stores, or nearly three quarters of the United States’ current solar PV capacity.

* By installing solar panels on two California stores, Costco reported savings of $300 per day on average over three months.

The report can be downloaded here.

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  • MtnMark

    Here in upstate NY I am seeing Solar going up on flat roofs in droves. And much of it by local installers. The economics here are very pro solar. Too bad Florida does not have the same policies/incentives as NY.

  • Larry

    Even more enticing is the proposition that all “big box” buildings on schools and school buildings (from elementary schools to colleges and universities) fill all their available roof space with solar panels. These are the educators. They could go a long way if the lead by example. Elementary and High schools at the local level could reduce operating expenses substantially (saving local taxpayers money) and the colleges and universities could show that they really are sources of higher learning while reducing their operating costs. Where are the leaders in our educational system?

    • MtnMark

      I agree 100%. Wish there was a program to get solar on all public schools. It’s a win/win.

  • nakedChimp

    This helps utilities avoid firing up expensive, peaking power plants to meet the temporary rise in demand.

    Uh? I think you put the cart before the mule there..
    Just look at South Australia, the Utilit(ies) there want the gas peaker to be part of the net to be able to charge a lot of money.

  • Guest

    Hmm, 62 GW sounds roughly like it might make the equivalent output from about 12-14 large nuclear reactors (@1,000 MWe each). I wonder how much they would compare just in terms of cost and time to build, leaving other externalities aside…

  • Tom G.

    Our communities economy is based on tourism so we only have about 3 or 4 large scale industrial buildings in the whole town to mount solar on. So depending on where you live the availability of roof space can vary quite a bit.

    For about a year I sold solar systems to homeowners and tried to get “big box” and the owners of “industrial buildings” to go solar on their leased buildings. The problem I ran into was this. If I sign a lease and move into that type of building I am required to pay for the utilities I use. Therefor the building owner has NO incentive to install solar.

    While several hundred homes have solar installed in our community and our city office along with some schools DO have solar, I can’t remember ever seeing a single industrial building which is leased with solar installed.

    • Omega Centauri

      That’s a huge problem, and a huge opportunity to whomever can crack it. I think some are trying with third party ownership, the lessee could sign a PPA as part of his rental agreement.

  • Matt

    And big box store are a small portion of the number of big roof ready for PV. Look out a window the next time you take off in a plane at all those empty warehouse roofs.

    • ROBwithaB

      Indeed. I’m sitting in an office in a industrial area right now. On the wall next to me is a large aerial photograph of the area, a bird’s eye view of about 100 warehouse and factory buildings.
      Doing a quick calculation of the roof surface area available, this one industrial area would be able to power a significant proportion of the daytime electricity consumption for the entire municipality.
      Unfortunately, our municipality has no interest in this, and is in any case precluded from buying electricity from anyone other than the coal fired national monopoly.

  • Ross

    Utilities and regulators in the pockets of the utilities will have a harder time thwarting big box stores that want to deploy rooftop solar than they do with domestic rooftop solar users.

    • Omega Centauri

      Especially if at max output the PV won’t cover the momentary power demand of the building. I.E. many of these big boxes would never be exporting power even at noon, so there is no need for net metering.

      Another good case would be the many medical office complexes. They are almost all closed after dark. But, you have the agency problem, doctors rent the office space, not own it.

  • jburt56

    You can put a lot of batteries in empty big boxes.

  • ROBwithaB

    I believe that commercial and industrial PV installations are going to power the growth of solar for the next decade.
    Once the numbers make commercial sense, every property manager is going to be phoning to get quotes.

    For so many reasons, it just makes sense.

    • Omega Centauri

      So much retail space is rented/leased, so there is a bit of an agency problem which needs to be overcome. This is similar to apartment buildings, the renters could benefit from cheaper power costs, but probably won’t go far higher rents to pay for it, and the landlords don’t want to pay for it.

      • ROBwithaB

        This is exactly the problem I have been grappling with for the past few years, as a commercial/industrial property manager in South Africa. Trying to model a business case for “landlord solar” is what brought me to CleanTechnica in the first place.

        I have run the numbers multiple times for multiple different scenarios. Have been closely monitoring the technology and the economics for a couple of years now, watching hardware prices decrease, utility tariffs increase and installers become more professional and knowledgeable. While waiting, have been checking out (and helping to refine) various mounting systems. (As a landlord, a chronically leaking roof costs me far more than I could gain from cheaper electricity.)

        I believe that the breakeven point is now imminent, especially with another 17% increase in utility tariff proposed for this year.

        The solution would be to register as a bulk purchaser of electricity from the municipality/utility, and then re-sell that electricity to the individual tenants. I’m not sure if this is allowed in many jurisdictions. If not, we should be lobbying aggressively for such ability, because it is key to significant commercial rooftop installations, IMHO.

        This model works especially well in a multi-tenant building, as the loads tend to average out, leading to better forecasting of maximum demand peaks. Also, a vacancy here or there doesn’t affect the total economics that much. There’s always “customers” for the “product”.
        It’s possible in many areas to buy electricity at a bulk tariff and resell at a retail tariff. The tenant pays no more than they would if they bought the power directly from the utility. But there is still some margin in it for the landlord, which would help to subsidise the installation of the PV system.
        Where I am, the discounted consumption tariff is coupled to higher fixed charges related to maximum demand. The ability of batteries to shave the peaks off the maximum demand suddenly makes some battery storage viable too.

        There are very significant advantages to commercial-scale rooftop PV. The most obvious is that one can negotiate significant discounts. In fact, it is quite possible to import full container loads of panels directly from China. At a bigger scale, everything just gets much cheaper per unit.
        The labour rate drops dramatically, as it is obviously much easier to lay down hundreds of meters of track in straight lines onto a large roof than trying to jigsaw-puzzle panels onto the various angles of a residential roof.
        There is only one permit required, only one electrician to connect it all up, only one engineer to sign off on the structural design. Roughly the same cost as for an installation one 20th the size.
        Big economies of scale all around.

        For malls, airconditioning is one of the main operating expenses. This expense is reduced radically by the shading that the panels cast onto the roof.

        There are no “marketing costs” at all. The tenants don’t care where the electricity comes from, as long as it works. In fact ,many businesses would be only too happy to boast about their green cred on the annual report.

        But the financial payback is not actually the main reason for me to go ahead with this. In South Africa, the biggest advantage to self-generation is that it gives some control over outages (what our monopoly utility euphemistically refers to as “load shedding”). I am finding that the economics of the situation are weighted more heavily in terms of avoiding lost productivity due to load-shedding. A small business that turns over R1m a month (to achieve a nett profit of say R100,000) loses approximately R5,000 per hour that the lights are off. (And that tends to come mostly off the bottom line. Sure, they could just send everyone home, but they still need to pay rent, monthly salaries etc.)
        For many businesses, the cost of losing an hour’s worth of business is thus greater than their electricity bill for the entire month. And because the load-shedding is erratic, the actual disruption tends to last longer than the outage itself. People shift meetings etc in anticipation of “scheduled” load shedding, and then it doesn’t happen. Or power is scheduled to go out from 2-4pm, and the manager gives everyone the afternoon off, but the lights come back on again at 2:30. That sort of thing. Very disruptive.

        Quite a few tenants have their own generators, and many landlords install large central generators. But there are very significant disadvantages to diesel-fuelled generators. And so we’re back to the solar + storage hybrid system….
        Most of the power would be generated by solar. For peak shaving, a large central battery. For blackouts, a smaller (Powerwall type) battery in each premises. Tenants can elect how much backup they need. Landlord installs one or more battery packs as required in each premises, in exchange for a nominal monthly ‘rental” fee, of perhaps R1,000, which can be amortise over 5-7 years. The peace of mind is worth it for the tenant, and they don’t need to worry about installation costs, electricity compliance certificates, etc. If they change their mind, I can simply use the battery elsewhere.

        At some point in the future, if we get some kind of feed-in tariff, it may become viable to over-produce. Until then, the PV on the roof would be sized to provide about 90% of typical usage, with the rest supplied by the municipality.

        I realise that South Africa is a “special case” due to our unreliable grid, but it’s a pretty significant economy. And once you start looking about, you’ll find a lot of the other emerging economies have similar constraints. Many GW of PV can be installed NOW, without any subsidies needed to make it viable.

        I’m deep into the rabbit hole on this one, doing the homework on installing a solar system of approx 400kW. Have installed a small guinea pig system in the meantime. All the components wired up in the configuration as set out above, with the feed-in priority protocols programmed into the inverter. Two different banks of panels, on different roofs, to determine optimal time-of-day mix of north facing and west facing roofs. Will be monitoring variables for an entire calendar year. Also time-lapse footage of the targeted roof areas, to ascertain exact seasonal shadow patterns.

        Have learned a lot from the resources on this site, and especially “the community”. But now it’s time to start learning by doing. Might even make all the data publicly accessible online, if anyone is interested.

        • JamesWimberley

          Great comment. I’m sure there must be plenty of building managers like you al over the world waiting for the price to drop to the point where the business case becomes a no-brainer.

          SA is not a special case for grid unreliability, in the world context. The Indian grid for instance is notoriously unreliable, and backup generators are standard. Generalise this to Indonesia, Pakistan, Mexico, Turkey ….

          One problem with big-box solar is that in the USA the companies can go renewable at less hassle by signing a PPA with a utility wind or solar farm. The price differential has to drop, not just the price. I suspect with others that the solar car-parks will take off first because the sites are standardised.

        • Omega Centauri

          Sounds like you are trying to make a serious go at it. How much do people want the backup capability? Are they OK with not being able to fully power through ALL outages from PV plus batteries. Because for any long outage, or cloudy-day outage, the storage system won’t be large enough (or pre-charged enough), to fully ride through normal demand. But, if that is OK, i.e. calculated cost of occasionally not having enough is still lower than frequently having none. If they really want fully reliable, they will still need a genset, -but hopefully the savings in fuel/wear on the system will still make the PV worthwhile.

          • ROBwithaB

            I don’t think ICE generators will be required. The “savings” on the system are thus absolute. Part of the trial program I am running at the moment will include a very thorough assessment of the individual and collective demand from all the tenants, over the course of an entire year.
            My gut feeling (based on the data I already have) is that MOST tenants would be able to power through any scheduled load shedding, with only minor disruption, for a small additional cost in batteries. A smaller number would face perhaps four hours per year of interrupted business, which could be anticipated at least a few hours in advance. (Unseasonal overcast weather for multiple days, coupled with unscheduled longer duration load-shedding.)
            There is probably only a single tenant who would actually still be significantly affected by load-shedding. A printing business that requires serious amps for banks of UV lights. But the sheer magnitude of their power demand makes any kind of multi-hour solution prohibitively expensive in any case. A generator that could do the job would cost about the same as the printing equipment. But would stand idle for about 95% of the time. Almost doubling the fixed costs on every job. And even if one could afford that low capacity factor, the diesel-fuelled kWh would come in at about 4 or five times the price of grid electricity, which would exceed the profit margin on the printing job.
            But what a (large draw, low capacity) battery CAN do for them, is give them a few minutes to shut down the machine properly.

            The PV will pay for itself by generating power for about 6 hours a day, 300 days a year, and sold to the tenants directly beneath the panels, at retail rates. Not only during outages. The fact that a hybrid system as envisaged can cover most of the demand during an outage is just a
            bonus. A big bonus.
            We don’t get that many cloudy days where I am. And the hungriest loads are for aircon and compressors on cold storage rooms. Which tend to work the hardest on hot sunny days. In summer.
            So far, so good….

            The SA grid outages (at this stage) are quite “organised”. Basically, within each municipality we have rolling blackouts, by substation, according to a schedule. In our area, that means we are usually hit with an outage from 4pm to 6pm, every second day, during a “normal” cycle. (What they call schedule 1. All very “proper”, almost as if it’s acceptable.) Once it gets to level 2, there would be an outage every day. Level 3 would be two outages every day, each of 2 to 3 hours. Something like that.
            This is generally limited to a period of a few months during the coldest part of winter.

            So, even in a completely disruptive, economy-shredding, rolling blackout, worst case scenario, there might only be about 150 charge discharge cycles per year. That’s a number that is well suited to the new generation of batteries.

            And at least one knows that any outage is limited to about 3 hours. Which one can plan for. And with a 3 hour period in between to charge up the batteries again, it doesn’t require excessive charge rates. So again, quite well suited to batteries. Also, bear in mind that most of the time in (subtropical) winter, the sky is perfectly clear and aircons are turned off. So the PV should still be producing, and the batteries might not even be required. Even if they are, they would probably only be required to “fill-in” a portion of the demand. Which means that the actual deeper discharge events will be very limited.

            (Of course, all of this assumes that they know what they’re doing, and we don’t get any unforeseen events that push us into level 4. Because *ominous horror music* THERE IS NO LEVEL FOUR. daaDUM daaDUM.)

            There is a significant amount of demand response that can be activated. The idea would be to wire up the DB in each premises so that the input from the (local, in unit) battery/ inverter only feeds certain circuits. The hot water geyser and aircons are always on their own circuits in any case, so its easy to avoid them. The big 400W mercury vapour lights in the warehouse can also be separated out, with a few LED emergency lights on the battery circuit for when the power fails. Or, the tenants are welcome to replace the vapour lamps with LED lamps in some or all of the fittings.

            There are some grey areas when it comes to the whole question of “but who pays for that?”. For instance, if the aircons are deactivated during a blackout, it wouldn’t be so bad if the offices were well insulated and could “store” the cold air effectively for a couple of hours. In fact, the requirement for aircon in the first place wouldn’t be so great if the insulation were good. So it makes a lot of sense to put down a couple of layers of insulation material on the office ceilings, which tend to be just underneath the IBR roof sheeting. Big energy wastage going on there, and begging for a permanent solution.
            The tenant would obviously get the benefit of lower electricity bills, but wouldn’t really have an incentive to spend money improving someone else’s property, if on a short lease.
            A similar argument can be made for low- energy LED lamps, blocks of transparent polycarbonate roof sheeting to let in more natural light, and so on.

            In my own case, I have basically decided that if it is the right thing to do, then one must do it. In many instances, it is probably not worth arguing about. the amounts concerned are mostly trivial, compared to the capital already invested in the buildings.

            Anyway, without meaning to bore anyone with the minutiae of the entire system, I think it is quite possible to make an economic case for PV in a “landlord” situation, even without subsidies. Especially if there is an added benefit to be gained from greater grid reliability.
            And it is quite possible to make the case for battery storage for frequent short-duration power outages for business tenants.

            The one thing that still requires some tweaking is: How do I send a signal from my central “power hub” to the individual premises, to inform them to cut back on their usage during times of outage? If the feed from the municipality and the solar panels and the big peak-shaving battery is all going into one big central inverter, and yielding a nice smooth output that distributes to the individual tenants, how do the local inverters even know that they are sucking juice from my battery?
            The idea is to make the tenants largely responsible for providing their own load-shedding backup, by hiring however many Powerwalls as they may require. In addition, they may also choose to reduce usage to limit the amount of storage required.
            But unless I can somehow signal to the tenants’ inverters that they should switch over to their own batteries, how do I prevent them from completely draining my battery?
            And how would I send a similar signal when the maximum demand threshold for the complex has been reached? I would want to limit the amount of work that the main battery needs to do, but need to be assured that we NEVER exceed the limit. (A single spike could double or triple the monthly connection fee, rendering useless all the “savings” from the bulk consumption tariff.
            Do I even need the big battery between the main incoming utility meter and the individual tenant meters? In effect, I would be acting liking a mini-utility, and would want to send out a “pricing signal” out across the network.
            This is one big detail that still needs to be resolved…

            P.S. Nobody is forcing anyone to read these posts of mine. I share freely of my plans and progress. If people find it useful or interesting, that’s cool. If not, also cool. Typing stuff out like this helps me to refine my ideas and makes it easier to identify potential problems.
            If someone has already solved all these “agency problem” issues, please send me a link, so that I can save everyone (but especially me) all the brain overload.

      • ROBwithaB

        Apologies for the lengthy answer, but I have been giving this a lot of thought over the past few years, and I believe I have substantially solved the problem.
        The business model is quite sound.

  • Tom G.

    Where I live in the desert Southwest we are usually fighting the heat about 9 months out of each year. Here we seen lots of parking lot solar instead of roof top solar since having shade to park under is something most people really value. Even our HIgh School which once had planned to have rooftop solar is now installing ground mounted solar.

    No roof penetrations, no leaks and shade. It doesn’t get any better, ha ha. And we have 10’s of thousands of square feet of parking lots which could be covered with solar.

    • Omega Centauri

      I’d like to hear how that’s going. Maybe you can get the managers in this site interested if you want to write about it.

      Where I live we have about 3MW, but all is in the government sector (high schools, and city rec center). We have a lot of retail space, but zero canopies for retail parking. I think the resource size of retail is a lot greater than for government sector, so if it could be aggressively utilized it would be a very big deal.

    • Brent Jatko

      Not surprising that parking lot shade is a valuable perk. I’ve heard tales of drivers in Arizona using oven mitts with little lobsters printed on them to hold their steering wheels.

      • Tom G.

        So true Brent. Been there and done that so to speak 🙂 Arizona is probably the only place where auto parts stores carry white steering wheel covers as price leaders when you walk in the door. Also high end car or truck seating is not considered to be leather but rather fabric. You have not lived until you have sit on leather seats in a pair of shorts on a sunny day, ha ha.

        But 9 months out of the year the Southwestern deserts have a lot to offer other than just being an awesome location to install solar. For some people there is beauty in those brown hills and odd shaped cactus. Have a great day.

  • wildisreal

    It would be awesome if someone developed a product that could easily stack on big box stores without requiring penetrations or ballast. Oh…yeah.

    • Martin

      Check out the Mosaic Center in Edmonton, Alberta. It has a 200 kW system on the roof, ballast- yes, penetrations- no. It is also a Net zero building, uses PV, energy efficiency, geo exchange with heat pumps, it is a 30.000 square feet office building.

      • wildisreal

        My comment referenced good old Solyndra…a company turned into political theater without the media ever bothering to report they manufactured a radical and experimental product. A standard solar company they were not.

    • ROBwithaB

      How did it work?

      • wildisreal

        They built PV cylinders held just above the roof with lightweight racking. The cylinder design allowed wind to flow past them without creating any upward lift (thus no ballast or penetrations required). Pretty slick idea (with higher up-front manufacturing capital costs obviously) but that is not what they are remembered for.

        • ROBwithaB

          Thanks. Hadn’t seen this before.
          Looks like a bit of an over-complicated solution, methinks.

          Maybe on old, flat, bitumen-sealed roofs it woulda made sense, but those are probably not optimal candidates for PV. It’s not like there’s a shortage of empty roof space waiting to be covered in panels.

          In the future, I can foresee that many buildings will be designed from the get-go to be solar-ready.

  • newnodm

    With solar prices falling, some business may figure that the last year of the full ITC is the optimal entry point.

    • ROBwithaB

      Even without subsidies/credtis, the optimal entry point is imminent in many areas.
      In a market where the price of the machine (PV) keeps dropping and the price of the product (electricity) keeps increasing, the time-value-of-money modelling can become horribly complex. According to some arguments, the best time to install a system would be never, as the economics next year will always be better.

      But in practice, business doesn’t generally work that way. If I can save money now, it makes sense now.
      Once payback periods, with interest cost, fall into the 7-10 year range, you can get a better return by installing PV on your existing building than by building another building somewhere else.
      Expect a LOT of commercial installations over the next few years.

  • Frank

    Anybody have any idea how much having solar pannels blocking the sun from hitting the roof would reduce AC load for a roof with average insulation?

    • Martin

      I had the same thought.
      At the same time all those if all those parking lot would be covered with PV as well, more power production and shading for cars, trucks etc and less of AC used after the shopping trip.
      Higher day time use of electricity: schools (flat roofs) office buildings, warehouses, plants, etc and their parking lots, parking lots-bigger than the buildings.
      All those already build up areas perfect for PV.

      • Freddy D

        Indeed, if someone can drop the installed cost of commercial parking lot canopy PV systems, this should be an immense market; probably several times the 62GW of big box roofs since parking lots apply to every kind of business and office and government building.

        I’m guessing that the installation on big box roofs is much simpler and therefore cheaper and more competitive at the moment.

        • PaddyB

          The cost of canopies for parking lots is coming down thanks to low steel prices and innovations such as SolarCity’s ZS products which integrate them cost-effectively with solar panels. It would be win-win if these could be widespread: businesses would gain sales as customers would be more drawn to stores with canopies which keep their cars cool. And solar revenues would offset the bulk of the costs of their installation / maintenance.

          • Otis11

            And don’t forget airport parking… people already pay a premium for covered airport parking. Why not make them generating spaces too?

      • Omega Centauri

        True. But unfortunately the cost of building the elevated mounts over parking lots is pretty high. So compared to the cost per watt of either a ground mount, or ballasted flat roof systems, its pretty pricey. I hope someone comes up with a major breakthrough in the cost of overhead mounting. But, until then don’t expect to see a lot built.

        • Jamset

          I thought ballast means rocks under railway tracks.

      • egriff5514

        Aren’t NRG putting in solar over car parks in California at building used by Kaiser Health?

    • Omega Centauri

      Probably not as much as you would think, simply because in most hot locales such roofs have been painted white.

    • AC Tesla

      That’s an impossible question to answer. Far too many variables. Depends on the rooftop, how many solar panels, how much sun, how much shade? Where is at? Seattle or Phoenix?

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