12VoltInstalls
life passes by too quickly to not live in freedom
It is fun watching you develop this!
5 years is a reasonable ROI imho. It’s hard at your scale to get anything much faster that isn’t being sold value-added.
35,000 SF Commercial Office Building
- Thread starter mciholas
- Start date
5 years is a reasonable ROI imho. It’s hard at your scale to get anything much faster that isn’t being sold value-added.
Way out of my wheelhouse but I’d be interested to follow along a 3 phase sol-ark design
Seems you quickly honed in on one of the more likely simplified yet robust choices and for your needs doesnt seem to get much “easier”
Seems you quickly honed in on one of the more likely simplified yet robust choices and for your needs doesnt seem to get much “easier”
Mike 134
Solar Enthusiast
Just following eating popcorn while the OP seeks advice on a commercial scale system on a DIY site.......
wpns
Solar Joules are catch and release
Indeed, and as you've noted, the rules change all the time...
HarryN
Solar Enthusiast
Looks like a nice project and building.
Grid sourced electricity is almost always going to be the most expensive during the summer in mid / late afternoon. It might come as a peak demand charge, TOU or other, but you are always going to be fighting that August 2pm - 8 pm time frame.
The other big demand point for a commercial building can be morning - 7 am - 10 am.
My suggestion is to focus on just making power during those times of day to the max extent possible if your goal is a reduction in your power bill. If you also want to add resilience so that a grid outage does not impact critical operations, then the battery back up can be at least partially justified based on that aspect vs a real ROI from power savings.
Grid sourced electricity is almost always going to be the most expensive during the summer in mid / late afternoon. It might come as a peak demand charge, TOU or other, but you are always going to be fighting that August 2pm - 8 pm time frame.
The other big demand point for a commercial building can be morning - 7 am - 10 am.
My suggestion is to focus on just making power during those times of day to the max extent possible if your goal is a reduction in your power bill. If you also want to add resilience so that a grid outage does not impact critical operations, then the battery back up can be at least partially justified based on that aspect vs a real ROI from power savings.
Hedges
I See Electromagnetic Fields!
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I am, but common sense economic considerations should be applied, except for hobbies.
Not all engineers can make good decisions.
Does this mean 1:1 net metering during each month? And the 25% of retail credit for exports is only applied for carryover to the next month? (I note "Excess").
That certainly makes it easier to size and get value from.
There was a time when the PV industry was driven by solar companies getting cheap money, putting solar on commercial rooftops with a contract letting the utility customer buy from them cheaper than from the utility. When money dried up during the financial crisis, price of PV crashed. Now, they offer similar contracts to even less financially sophisticated homeowners who often get a raw deal.
"· Battery Ready for DC Coupled and AC coupled system
· Support backup power and dark start operations
· With Rapid shutdown solution & AFCI integrated"
If you go for that, you can have battery backup of critical loads.
Given the NEC rules for ESS, may be easier to get permitted without battery, add it later.
Alternatively, EG4 18kpv + PowerPro offers UL listed ESS.
When an inverter sells new for $0.13/W, I do have my concerns whether quality is good enough. Of course if it dies, easy to swap a box.
teal95
Solar Enthusiast
Following along to learn as I'm doing something vaguely similar, although mine's still a hobby. I have 4x EG4 6500ex for making 208v 3 phase. They were discontinued soon after I got them so while they still have refurbs they're unlikely to have them once the CFO approves more funds. I also have a SolArk 15k, 60 kWh of batteries and currently 20kW of panels. SolArk is operational and 3 phase is in progress.
Thanks, designed it myself and there are very few things I would change now 10 years later.
My utility doesn't have TOU charges of any kind that I am aware of. The electricity is predominately generated by a coal power plant. I joke that my EV is solar powered, but it was sunshine from millions of year ago stored as coal.
Since I don't have TOU type rates, there's no need to try and shift load.
Backup is either the entire building, which is cost prohibitive just from the switch gear, batteries, and inverters required, or just to backup the server room, which we already do and would be cheaper to augment by itself. Power reliability is high, about 1 outage per year and nothing in excessive duration so far.
Mike C.
Last edited:
No, it is "instantaneous" import and export. The meter reads the amount of power that imports separately from the power that exports.
The utility then computes the charges for the import power with all the factors (meter charge, energy, fuel charge, demand charge, etc). It is what your bill would be if you paid for the import only.
Then the utility computes the export credit. If that credit is LESS than your import charge, you pay the difference that month. If the credit is MORE than your import charge, you pay nothing and the excess credit carries forward to the next month.
What this means is you can have a really big summer period, build lots of credit, and then spend it during the winter.
In order to zero out your bill overall, you need about 4 times the energy for export and you import. You always want to use the power locally first as that is 100% credit (no import KWH needed) but you can't do that without the sunshine unless you have a battery, and the battery costs money and wears out eventually.
My thoughts exactly.
I actually missed the "battery ready" part of those inverters. he batteries are good for powering the load when the grid is up, but they don't work for backup unless you add their transfer switch which is 500 ms, thus too slow to serve as a critical loads backup. Thus the batteries are only about optimizing energy delivery for lowest cost. I'm probably better off just putting in more panels and pushing more export than buying batteries, particularly if they don't get me backup.
In that case, all I need are grid tie inverters with no battery capability at all. Microinverters would do it, but cost so much, so some inexpensive string inverter is all I need. Since I have not sunk so much money into those, I can replace them at some future date with a hybrid if I want and save the panel array.
One way to treat this problem is to install 6 or 9 units (since I need to do them in triples for phasing), and then buy 1 or 2 spares in stock. One goes bad, swap it. The cost of the spares is still less than the premium for some other units.
I can also probably fix units like this since we are an electronics company and have our prototyping and rework tools for circuit boards. We usually work on small stuff, though.
Mike C.
Dagoth Ur Does Solar
Solar Enthusiast
The cost of using grid to run that building seems stupendously cheap. I some months pay 1/5 that for my small residential home. I can't imagine doing a full solar with battery build out would be economical in OP's situation.
The building was designed from the start to be highly energy efficient. I use on average only 2500 KWH per month to heat, cool, ventilate, and produce hot water for the building. This is due to the geothermal heat pumps and super insulation. That is an average of 3.5 KW power to heat and cool my 35,000 SF, or 0.1 W per SF.
The nominal industry standard is 400 SF per ton of cooling, I have 833 SF per ton, less than half. And it is plenty, I don't think my geothermal units have ever used 2nd stage in the entire 10 year history of the building, so I am operating well above 1000 SF per ton in first stage.
The DoE estimates the average office building uses 0.85 W per SF for heating, cooling, ventilation, and hot water, so my building is about 88% less energy to do that than the average office building for those same functions. I think my building could be among the most energy efficient that exist.
When I built the building 10 years ago, we looked at solar briefly, but the cost and technology wasn't ready. Things have gotten so much better in recent times, far more value for the dollar.
The money isn't all of it, there are community, social, and marketing value to my building being more energy efficient.
Right now my thinking is a bunch of solar panels and a bunch of inexpensive grid tie inverters. If that works, it is low maintenance, low monitoring effort, and low install effort. This was not the way I was leaning when I started, but kicking around ideas is what forums are for.
My leading inverter choice is the Growatt 11.4 KW (which is ~10 KW when doing 208 VAC). About $1500. Any other choices? Doesn't need to have battery capability at all, so that feature on the Growatt isn't that interesting.
Mike C.
For this scale of professional building one would normally hire a professional designer and contract it out properly.
You shouldn't be fussing with volunteers and amateurs on a DIY forum unless your business employs a lot of skilled electricians and you plan on doing it yourself.
You shouldn't be fussing with volunteers and amateurs on a DIY forum unless your business employs a lot of skilled electricians and you plan on doing it yourself.
HarryN
Solar Enthusiast
My assumption was that your "demand charge" was due to summer time HVAC, which is probably true for most buildings, but perhaps not yours.
My father had a small business in OH many years ago and that demand charge was hit on hot summer days and for him was a big part of the electrical bill, as he had walk in coolers and a large amount of refrigerated frozen food cabinets.
Again speculation on my part, but it sounds like the geothermal system pumps might be one of your significant uses of power? if so, then a power system that is focused on just running these pumps might be interesting.
You could also install roof top water evaporation - which may or may not help given how reflective that white surface already is.
My father had a small business in OH many years ago and that demand charge was hit on hot summer days and for him was a big part of the electrical bill, as he had walk in coolers and a large amount of refrigerated frozen food cabinets.
Again speculation on my part, but it sounds like the geothermal system pumps might be one of your significant uses of power? if so, then a power system that is focused on just running these pumps might be interesting.
You could also install roof top water evaporation - which may or may not help given how reflective that white surface already is.
If I had done that with my HVAC system, it would have turned out to be a mess. We definitely did it differently than the pros would have following their cookbooks. We designed it and hired an HVAC company to install it per our plans.
We would design the solar system and we would hire an electrician to install it. This is vastly simpler than the HVAC system, it just isn't that big a deal. The prime effort is to figure out the system architecture to fit the goals.
In simplest terms:
Add 200 A 3 phase back feed breaker to main panel, goes to AC combiner panel for all the inverters. Each invert feeds the combiner panel. Each inverter has strings of solar panels. Solar panels mount to standing seam roof with rails mounting seam clips. Appropriate wiring and conduits. That's pretty much it. I don't need to change any building wiring at all.
Mike C.
Hedges
I See Electromagnetic Fields!
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What kind of roof? Mounting of panels is most of the cost and work.
I like SMA, so this is what I'm planning to install for a couple people:
www.sma-america.com
The 11.4kW model is due out end of the year.
Prices will be around 3x the one you're looking at, and HV batteries from BYD will be 2x the price of some 48V batteries.
I don't know if SMA's new products are as good as early models. I find documentation lacking for their HV battery inverter, and it is behaving erratically.
Their older GT PV and LV battery inverters are great. But you are probably required to get new grid-support features. If you did zero-export, you might have greater flexibility.
Make sure you won't be pushed onto an unfavorable rate schedule when you install solar.
I like SMA, so this is what I'm planning to install for a couple people:
Discover the Sunny Boy Smart Energy | SMA America
The hybrid inverter at the heart of the SMA Energy System, with three backup options: Sunny Boy Smart Energy ► Discover now!
The 11.4kW model is due out end of the year.
Prices will be around 3x the one you're looking at, and HV batteries from BYD will be 2x the price of some 48V batteries.
I don't know if SMA's new products are as good as early models. I find documentation lacking for their HV battery inverter, and it is behaving erratically.
Their older GT PV and LV battery inverters are great. But you are probably required to get new grid-support features. If you did zero-export, you might have greater flexibility.
Make sure you won't be pushed onto an unfavorable rate schedule when you install solar.
HVAC averages 2500 KWH per month, rest of building is 6500 KWH per month (lights, computers, equipment).
The demand charge is due to HVAC units randomly being on at the same time, and maybe some piece of equipment (like the 5 KW temp chamber). This is more likely to happen in the summer than winter, but it can vary.
In reviewing the rules, it is the highest 15 minutes of usage in the month, or 60% of the highest usage in the past 3 months, which ever is largest. My usage is usually never triggers the 3 month clause.
My average usage is 12.5 KW and my demand numbers run 22 to 32 KW. So really not that high a peak to average ratio. It isn't like we are turning on an electric arc furnace or something.
No, the loop pumps are variable speed and use only about 75 watts each, there are 9 of them, each unit has its own. They all share a common header system so when only one is pumping, very low pumping losses due to low fluid velocities In this picture, 5 of the 9 units are running, which is unusual. You can tell by the flapper valves being open in the clear check valves. One unit isn't hooked up yet, unit #6, valves are closed.
Pipes in the background go into the ground to the wells, pipes going up to the ceiling go to the HVAC units.
I couldn't get the HVAC guys to build this, and a plumber wouldn't touch it, so I built the header system personally. Works fantastically. Thus I am not afraid to charge into commercial scale work with DIY vigor.
White roof was chosen specifically for solar reflection. An evaporation system would be pointless and wouldn't make any measurable difference.
Mike C.
Kingspan KingSeam insulated metal panels:
They are the second part of the energy usage story, very well insulated. The building is insulated like a refrigerator, two metal skins with foam between them.
You can buy standing seam clamps to which you mount rails to which you mount panels. So there is some cost for the hardware but the install is rather simple. There is even direct panel to seam clamps, but that doesn't seem like the right thing, I think having rails and elevating the panels off the roof a bit would be wise.
I considered some sort of tilted mount on the roof which would improve panel effectiveness, but the cost for the mount would exceed the cost of the panel, and putting more panels up to compensate is cheaper (and probably less subject to wind damage). I have the space for ground mount, but the cost of the mount and possible vandalism makes that less attractive. It would be simpler for RSD stuff, though.
Seems like a direct competitor to the Growatt. Worth looking into. Also has battery connections. Guess those must be moderately easy to provide.
That's a factor in the decision process, of course.
The rules are fairly well known at this point. I am DGS (demand general service) rate, and solar adds the EDG (excess distributed generation) rider.
I will, of course, run that all to ground to be sure.
Mike C.
Hedges
I See Electromagnetic Fields!
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Hardly a "direct competitor". SMA invented the grid-interactive PV inverter. Also the transformerless grid-tie inverter.
Back in the early 2000's when I put in mine, California was giving rebates. SMA was > 50% of all installs. About 20 other brands made up the other < 50%.
But competitors have gained ground. SMA still sells, maybe the MW scale equipment is a more important business now.
Fronius is another quality German brand. They also have 1000V inverters of moderate wattage (one forum member installed 3), so could be good for your scale of system.
SMA has 3-phase inverters, but they're 277/480V. Best to avoid adding transformers.
I like the idea of 3-phase, because then zero ripple on the capacitors. With 3x single phase inverters, each carries 60 Hz ripple.
SolarEdge has been popular, but with what I've heard about failure rate I would avoid it.
Enphase is popular with installers. No particular number of panels has to face a particular direction.
But I agree HV string is the way to go. And you can parallel strings of different orientation, get flatter production curve.
Be use to use all genuine Stabuli MC4 connectors, they invented it. Or at least mated interspecies pairs that are UL listed. Unless you decide to cut off, crimp, waterproof heat shrink like some people say. (look up Walmart rooftop fires.)
Back in the early 2000's when I put in mine, California was giving rebates. SMA was > 50% of all installs. About 20 other brands made up the other < 50%.
But competitors have gained ground. SMA still sells, maybe the MW scale equipment is a more important business now.
Fronius is another quality German brand. They also have 1000V inverters of moderate wattage (one forum member installed 3), so could be good for your scale of system.
SMA has 3-phase inverters, but they're 277/480V. Best to avoid adding transformers.
I like the idea of 3-phase, because then zero ripple on the capacitors. With 3x single phase inverters, each carries 60 Hz ripple.
SolarEdge has been popular, but with what I've heard about failure rate I would avoid it.
Enphase is popular with installers. No particular number of panels has to face a particular direction.
But I agree HV string is the way to go. And you can parallel strings of different orientation, get flatter production curve.
Be use to use all genuine Stabuli MC4 connectors, they invented it. Or at least mated interspecies pairs that are UL listed. Unless you decide to cut off, crimp, waterproof heat shrink like some people say. (look up Walmart rooftop fires.)
12VoltInstalls
life passes by too quickly to not live in freedom
Having been employed in the past as a facility manager ~65,000 square feet, and having pulled off several feather-in-cap efforts electrically and structurally that passed inspection rigor that included federal standards (due to the medical nature of the organization) i can say for certain it is not only 40% to 75% less expensive to “self-design” and manage a project; only hiring engineers and contractors to verify designs, acquire permitting, and perform the work; but also you don’t find yourself asking, “why do we now need this ______?” And then having to scramble to discover they are merely creating equipment sales and extra revenue on labor.
That sortof alludes to the stigma and stereotypes of “diy” being clunky or unskilled or whatever. Competence, however, isn’t exclusively obtainable by “professionals” but rather competence is often more readily obtained by diligence.
I see no problem with this. Thomas Edison, Henry Ford, Nikolai Tesla developed things without relying on someone else to figure it out
and this proposed system has way less challenges than they faced. I love that thinking- and in spite of obtaining excellent quality at a high price the high-priced units can still fail on their own or perhaps with help from lightning or whatever.
My suggestion would be, however, to have at least four spares in stock. The instant swapability of like for like and low cost of the units is too attractive. Not only that, at the speed of the market and technology say six years from now nothing like your units may be available at any price. So when one a whole triplet set feeding your phases decides to conk for some unforeseen reason you can be back up and running in a few hours or less, and not be figuring out what equipment to integrate.
Just my thoughts. I’ve never done anything at your scale with solar.
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