Specifications Help Request for 100KW installation

**J.P.M.** · 03-12-2022, 12:23 AM

Originally posted by SteveCronk

Hi,

I'm trying to buy an all-in-one system for my company to install when we move from a 4,300 sf rented space to a 10,000 sf purchased building. I've done a decent amount of research, but would not consider myself an expert. I'm looking to pay someone to write an RFQ (Request for Quote) for me, so that I get what I need to maximize our roof space and fill our power needs. This would be a hybrid system.

Here's what I'm looking at:

-Building faces exactly south in St. Paul MN.

-Usable flat roof size in 100% sunshine all day is 4730 sf or 440 sm. No trees, no tall buildings touch it.

-There is a lower level that is partially shaded later in the day, but I think enough of it can be considered sunny to bring the available sf up to 7168 sf or about 600 sm.

- I've been told 600 sm is what would be required to hold a 100kw installation.

Since we don't have a utilities history in the space, I don't know how many kwh we will need. Roughly, I think we currently use 1000kw/mo based on my landlord's electric bill. 44,000 sf building, he used 9320 kwh/January, I rent 1/10th of that, etc. = estimated <1000kwh.

The new building is over 9,000 sf, so double, let's assume 2500 kwh/mo max electric usage = 17000 watt installation.

I have lots of roof left over to switch the gas heat over to electric, then.

I'm told I will need 300,000 to 400,000 BTU to heat the place X .293 Watts/btu = 117,000 watts.

Running all lighting, production tools, computers, heat -- all of it -- will require something around 130,000 watts.

A) Did I do all those conversion right?
B) Is there any reason why I wouldn't just fill up that roof with a 100,000 watt array?
C) Is there an expert or two on here who would allow me to pay them to write my RFQ that I will send to several Alibaba companies who supply industrial kits of this size. I HAVE EXPERIENCE buying commercially off Alibaba as well as importing industrial machines from China. So far, quality has been better than expected. I can also clear my own customs. I know I need PERC, monocrystaline panels with tempered glass and an inverter and batteries with a good BMS...but...this is not my thing and it would be good to have someone who knows the right way to write this.

Some examples of these systems that come in a shipping container which literally has one grid connection plus the solar set up:

https://www.alibaba.com/product-deta...2ce83e5fPLrWLF

Since this would sit in my parking lot, and since I have a good commercial 3 phase qualified electrician, I am more than ready to install the panels on the roof myself. But I'm looking for a little guidance. steve@torpedobags.com

Educated guesses on your questions:
1.) Mostly. but that's less than a good surface scratch of what's required.
2.) Yes, lots of them, particularly in an area with snowy northern winters. Wind loading on tilted arrays and snow removal and /or snow covering on panels and itsseffects on system output being only two such considerations, not to mention several hundred or more holes in a flat roof.
3.) Maybe, but regardless of any consultants you may contract with, and not passing opinions on the efficacy of solar energy applications in the Twin Cities area, from what I think I may know, it seems like an idea that has more details than may be worth the effort to work through. There's a lot more to applications such as this than you may think you know.

I have no idea of the particulars of your application beyond what you've written, but as a general comment and with some exceptions, the farther an application is from the equator and also the less sunny the area, the harder it is to make alternate energy a viable method to power or heat something, usually and commonly because the economics can't be made to work. Those who are often of the inexperienced and solar dreamer set usually won't tell you that either because they drank the tree huggers' kool-aid or haven't figured it out yet, or both. Process economics or engineering economics do not tend to be such folks strong suit. Many, if not most larger commercial solar projects can only be made to look cost effective because of local, regional or federal largess or incentives.

How many hundred kW scale PV projects have more than 10 years operating experience in the twin cities area ? I'd seek the owners of such systems out and ask to have a chat with them.

Lots of folks (consultants) will take your money. While most of them are often well meaning, most are also less experienced in the world of industrial equipment, its procurement, application and installation with most of them gravitating to the fringes of engineering/consulting work because they couldn't cut the mustard doing real engineering or they stay in academia as mostly one trick ponies.

I'd begin by contacting contact several established licensed electrical contractors in the area who have sold solar for at least 5 years and are still selling solar and have a chat with them as well. With what reads like your PV knowledge and experience level, this doesn't read like a DIY project that's destined for success. Those with other sources of income besides PV have a higher probability of being around in the future if needed. Tt this time PV seems to be undergoing a bit of a shakeout and assault from the POCOs over net metering. Vendors who were around before PV got hot 10-15 years ago will likely have the best probability of being around after the blood letting.

NOMB, but I'd get more informed about the prospects for success as well as the limitations of solar energy technologies before I got more serious.

Welcome to the neighborhood and the forum of few(er) illusions.

**bcroe** · 03-12-2022, 12:58 AM

You have the right idea, research and run the figures. I have
been doing solar electric and heat for 9 years on a smaller scale,
in northern IL 42 deg Lat. Here are some of my thoughts.

Good panels are rated something like 16 watts per Sq Ft absolute
peak. So your best roof sounds like 70KW. But there are a whole
list of factors that keep you from coming near that on average.

Panels need mounting, wiring, and probably safety spaces. Those
will cut your Sq Ft. Then you are on a flat roof, so the angle of the sun
will cut energy delivered by something like the cosine of your lattitude.
That is at solar noon, it will be even worse other times. In fact you may
have only several hours a day with significant generation. Then expect
to lose something like 10% in inverter DC to AC conversion loss before
it gets to the load.

My next problem is snow. On a flat roof with little extra space, it will just
stay there till warmer weather comes, killing output. Here ground mounted
panels are mounted at steep angles so much snow can clear itself, and the
rest can be cleared by hand. You would not have the space or the labor
resources to do this on your flat roof. Ice, I can do nothing till good sun
eventually melts it.

The next problem here is clouds, how are yours? Even the lightest clouds
will knock down output, medium might give you 15% output, heavy could
shut the system down. That smoke from the left coast fires had more effect
than you might expect.

Shade is devistating, but less a problem if it does not occur during those
several good hours around noon.

Another problem is managing the solar energy. The most economical and
efficient way to do that is with Net Metering. The Power Company here is
used as a 100% efficient, infinite capacity, zero cost and maintenance,
battery. Batteries cannot come close, and large enough to do anything on
your scale will have a list of problems, including cost, maintenance, space,
safety, and the EPA. Here Dec generation is a third of June generation, and
storing half a year of energy till it is needed only works with Net Metering.

So check what an installer could really install, and run sun simulations on the
real annual energy collected. Contact your PoCo and see what your scale
installation options are. You will need a contract. The installation you
describe must support not only the equipment, but also the most severe
HVAC load. My feeling is, your expectations need adjustment.

Heating electrically is another problem. I can do it because my Heat Pumps
multiply the input enegy several times to heat the buildings. At your lattitide
air to air HPs would not work at the lowest temps. A quite large buried geo
thermal HP could do it, at very considerable cost.

Bruce Roe

**SteveCronk** · 03-14-2022, 02:32 PM

Thanks, Bruce and JPM. I'm not terribly concerned about snow if we're hybrid. We seem to get very little snow these days, and there is no shade up there. It would melt pretty quick. I'm probably more concerned about sunny / cloudy days. I'll dig into the Net Metering thing, and I have 4 locals I can contact to get a better idea of output at 45 latt, 2 being guys who work for installers, and the other 2 put off grid installations up on farms.

The current electric bill for this place is close to $6,000 a year, gas heat is about that as well, but the whole HVAC needs a reboot install. If I can save $10K a year, with the handicaps you've outlined, and get this installed for under $100,000, it seems worthy of further investigation.

**richmke** · 03-19-2022, 04:10 PM

Unless you are doing it for clean energy purposes, pencil out the cost of gas vs solar electric heat. In St Paul, you will need gas backup for cold days, so now you are just looking a fuel cost savings vs entire cost of solar and electric heat pump.

You may need an engineer to determine if the roof can hold the weight of all the equipment.

Lots of companies (big box stores) are putting solar on their roofs.

Specifications Help Request for 100KW installation

Specifications Help Request for 100KW installation

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