The More I read the less I seem to understand, but here it goes 10,820 Amps @ 24 Volts Really?

[drmcland]

I have a small shop. 3D printing Business
Fluorescent Light/s 80 watt (110 v) ( on A/C Circuit)
12 - 3D printers (250 watts each) 3,000 Watts Divided across ( 2 Circuits)
1 Floor Model A/C 1370 Watts (110 V) (1 Circuit)
Grand Total per hour 4,450 Watts (roughly 40 amps @ 110V)
Total wattage for 24 hours (24 x 4,450) = 106,800 estimated (107Kw) Per Day

Now for the fuzzy logic
Some days the printers and A/C are running 24/7 other times just A/C and a few printers

Per solar calculators I can expect about 5.5 hours of full sun per day, based on my location (N Texas)

If I am doing the math right I would need a monster of a solar system to provide 4,500 Watts per hour (rounded up) to my equipment just to come on, but this says nothing to charging / using batteries for off grid the other 18 to 19 hours per day or cloudy days.

Calculator URL - https://www.donrowe.com/power-inverter-faq-a/258.htm#how_long
(20 x (Battery Capacity in Amp Hours) / (Load Power in Watts)) / 2 = Run Time in Hours
(20 x (450 Amp Hr) / 4500) /2 = 1 Hour of Run Time (Perfect World)

So to get 24 Hours of Run time (I would multiply the 450 Amp Hour x 24)?

In short, I would need more Solar Panels than I have Sq ft of roof
30V Panel @ 200 Watts - (Not to mention the ability to fully recharge the batteries in 5.5 Hours)

Am I wrong here? I hope so,

 

[svetz]

The trick is the duty cycle and that while your gear might say it's 250 watts... that could be a max rather than what it draws on average.

So, duty cycle is the ratio of hours on vs off during a day. For example Air conditioners don't run 24x7 (Might be close in Texas though! ;-)
You can see an example of an energy audit in this post.

The way to know the actual power consumption is with a power meter.

 

[drmcland]

Thank you,
The A/C does cycle yes,. But since these are 3D printers, they have a heated bed and of course nozzle,
So the A/C does stay on most of the time, with very short cycle times

DRM

 

[Ampster]

4500 Watts is not a monster solarpanel system. How much square footage do you have on your roof? Also it is easier to calculate everything in Watts or kilowatts. Your electricity is billed in kiloWatt hours. A good starting point is to use your monthly kWh usage as a target.

 

[gnubie]

He'd actually need about 22kW of actual production during the 5 hours of sun exposure to cover 4.5kW of hourly consumption, but given that across that 5 hours of sun he has mentioned his system won't be at peak I'm taking a stab that all things considered, sun angle etc, he may well want 30kW of panels. Not impossible but most houses don't have a roof layout that can accommodate that sort of capability due to different slopes etc. My own roof is pretty good for solar with ~12.5 metre long unbroken runs, even so I'd be pushing it to get that sort of array on the roof.

*edit*
change length of roof, and not sure why I assumed it was a complex roof since it's commercial property probably so it might well have a simple barn like or flat roof.

 

[Ampster]

30 kW of solar is a monster system compared to 4.5 kW. Do we know the 24 hour kWh consumption?

 

[Forbisher]

Thank you,
The A/C does cycle yes,. But since these are 3D printers, they have a heated bed and of course nozzle,
So the A/C does stay on most of the time, with very short cycle time

Why are you converting your grid powered shop to solar?
How many square feet in your shop?
Air conditioning in Texas 24 / 7 will be expensive on solar.
How much are your power bills per month and yearly? All your past power useage is on your bills.

 

[drmcland]

Thanks all,
this is the total for the house and shop.

 

[Steve_S]

I feel I should point out. You have to calculate based on the Average Available SUN HOURS which are lowest in December & highest in June, generation potential should be calculated for Low Sun Hour periods. Examples from Dallas below.

!-1 Solar Panels will never generate the total Watts they are rated for, that is only in a lab. 80% is average optimistic.
!-2 Solar Panel Angle & Direction have an instant effect on performance as well. Proper alignment is essential.
See here to convert your Roof Pitch to Angle to determine if your roof's pitch is even close enough to the correct angle required.
https://www.barntoolbox.com/roof-pitch-angles.htm
!-3 Number crunching: 4500W ÷ 120VAC (not 110) = 37.5A rounded up to 40A. = 120VAC/40A.
4500W ÷ 24V = 187.5A (pretty much the max for 24V)
4500W ÷ 48V = 93.75A acceptable range. MInimum 5Kw Inverter/Charger suggested, 6Kw (6000W) more appropriate.
(Pure Sine Low-Frequency Inverter ONLY, LF is capable to 3X surge)

LFP Capacity consideration: LFP can go to 100% DOD but for longevity & performance most will only use 80% DOD.
24V/100AH = 2400Wh/2.4kWh (1920 useable @ 80%). 48V/100AH = 4800Wh/4.8kWh (3840 useable @ 80%)

Currently, the most popular cells are the 280AH units (best bang per buck). 1, 48V pack requires 16 cells and a 16S-BMS.
Free Shipping to USA &16Pcs 3.2V 280Ah Rechargeable Iron Lithium Battery Lifepo4 Battery for Solar System for EV
$ 1,706.02 total. https://www.alibaba.com/product-detail/Free-Shipping-to-USA-16Pcs-3_1600066773779.html
A BMS can run from $125.00 up, a respectable one would be around $200.00
Round it to $2,000 per 48V/280AH pack including fuse, box and required bits. * FYI: Battleborn 12V/100AH drop-in replacement batteries = $900ish
48V/280AH = 13,400Wh / 13.4kWh. 10,700wh/10.7kWh @ 80%

108,000 Wh / 108kwh (24hrs X 4500W) based on your calcs, says you require 10 packs per day with no autonomy (extra days of stored power in case unable to generate/charge)




SOURCE: https://weather-and-climate.com/average-monthly-hours-Sunshine,dallas,United-States-of-America


SOURCE: http://www.solarelectricityhandbook.com/solar-angle-calculator.html

 

[drmcland]

Outstanding write up, yes sir, I have come to the right / correct source.
Back soon with more questions

 

[Steve_S]

Outstanding write up, yes sir, I have come to the right / correct source.
Back soon with more questions

Also consider that conservation is far cheaper than generation & storage.
Fluorescents convert to LED as well as other lights.
Possibly the AC unit can be improved with a higher efficiency model ?
Are the 3D Printer power supplies optimal or could there be more efficient power supplies ?
Any other electric devices/appliances which may be used occasionally that you have not allowed for ?

Is there any shading of the building from the sun ?
Do you have a white roof or black roof (it makes a difference) ?

You mentioned using your roof for solar panels. There are various ways to mount panels onto a roof, depending on the roof type & structure. One must be quite cautious about doing this right, else you could create a nightmare of a roofing problem, I have seen this happen to folks and it simply ain't pretty. For Example, an asphalt shingled black roof that's already 10 years old, showing it's age, would not be a good candidate to mount panels over, you still need a good solid roof under the panels. Up here recently a few folks have done a reroof with white seamless tin and used bi-facial panels to gain the extra bit of wattage per square foot.

 

[Hedges]

Thanks all,
this is the total for the house and shop.
View attachment 18992

Not a full year's data, so maybe August/September will be higher, but this peaks at 5000 kWh/month.
That's 167 kWh/day, 6.9 kW average draw. About 50% higher than your estimate? How did that happen?
Normally rating plates and specs on equipment is higher than it draws (except instantaneous surge starting a motor.)
Annual kWh labels on consumer appliances on the other hand represent average, normal occasional use and typical ambient temperatures for cooling equipment.
Good that your consumption is less in winter, when there is less sun. But PV production may peak in the spring and fall when cooler, be reduced in the heat of summer when consumption is maximum.

Your usage as shown is about twice what my system produces. If your consumption was constant throughout the day, the draw from batteries at night would be 6x what my (14 kWh usable) battery could supply. If only the printers and not the A/C ran at night then 4x my batteries.

To run 7 kW for 12 hours without sun would take 1750 Ah at 48V of usable capacity. Lead-acid (AGM or wet-cell forklift batteries) you might cycle 50% DoD, so 3500 Ah @ 48V. AGM might need replacement in 3 years, not sure how many cycles a forklift battery lasts but I think much longer. Lithium last longer than AGM but retail (non DIY) prices are proportionately higher.

Such a system size is quite doable with SMA Sunny Island. The battery capacity is within their 100 Ah to 10,000 Ah range. Output power could be met by two Sunny Island, which would support 120/240 VAC @ 50A. Each can produce 3500W at 50 degrees C, 2200W at 60 C so you might need four if not air conditioned. This is for producing power from batteries.

Their battery charging limit is 110A, so two would put 10.5 kW into batteries. (PV panels on Sunny Boy which produces AC.) With four Sunny Island, 21 kW into batteries. With all panels at one fixed orientation, 5.5 effective hours or 115 kWh during the day, About enough to make it through 12 hours with no sun. Orienting some panels toward morning summer sun and some toward afternoon summer sun would be even. Additional PV capacity with DC charge controllers could be added.

Total of 440A charge current, or a bit more with DC chargers into 3500 Ah is 0.13C, may be slightly higher than desired. A 5000 Ah to 7000 Ah battery might be suitable (but does not give you the suggested 3 days operation without sun, rather a couple days.)

Now our usual suggestion: How about no batteries, rather grid-tie; is net metering available?
If not, how about a "no-export" system with PV producing most if not all power while the sun shines, but running off the grid at night?
PV is cheaper than grid in my area, probably parity with grid in Texas. Batteries are more expensive than grid (considering cycles to wear out and replacement cost.)

250W per printer isn't a large number, but 12 of them adds up. Is that waste heat from electronics that must be removed? Or heat loss from something that needs to be kept hot? For the latter, can you modify with better insulation? For the former, can you keep electronics cool enough with fast moving forced air, taken from the hot outside and filtered? Is swamp cooler effective there?

 

[drmcland]

Starting new Thread based on what I have learned
thank you all

DRM