Below is, by the posters own admission, eight hours use for work shop
and house.
According to the numbers supplied, after an amount of prodding, we can
break it down to this.
Welding use;
100min / 60 = 1.6 hours X 5kW = 8000kWh / 24 = 333Ah
House use;
4000Wh / 24 = 166.6Ah
Input;
12000Wh / 24 = 500Ah
Total;
333Ah + 166.6Ah = 499.6Ah
The point of interest as far as "Workshop In An Alternate Home power
Environment" is concerned is the actual energy use involved.
The system in question that supplied this has a battery bank of 1200 Amp
hours.
499.6 Amp hours use is the equal of ~ 42% of the batteries capacity in,
it must be noted, 8 hours.
If the house load is constant at 166.6Ah for the next eight hours the
total use for the day would be 666.2Ah.
This is more than half the batteries capacity.
So if you live next door to Wayne you too can can bodge up a system that
will allow you to work while the sun shines.
BUT; If you live in northern California or Maine or Idaho or Florida, in
fact almost anywhere else, you will have to pay very close attention to
your numbers when you set out to design a system for your use.
>> wmbjk wrote:
>>
>>> wrote:
>>>
>>>> wmbjk wrote:
>
>
>
>>>>> Here's a sample day's work (yesterday's) in an off-grid workshop. The
>>>>> project was building the last 2 of 5 scissor trusses for a friend's
>>>>> aircraft hangar. All material was scrap - chords of 2" and 1.5"
>>>>> schedule 40 pipe. Long braces from T posts, shorter ones from 5/8"
>>>>> sucker rod. Most of the material was cut a few days ago. I wore out 3
>>>>> chop saw blades (medium quality ones) which should give you an
idea of
>>>>> run time. The trusses are 40' wide, but built in halves. Each half
>>>>> took about 30 minutes to lay out and prep, including about 15 minutes
>>>>> use of a 4" side grinder. Then 26 welds per side, flip, another 26
>>>>> welds. Layout, prep, and welding - about one hour total per half,
with
>>>>> a long break between each one to cool off. I built 4 halves,
about 100
>>>>> minutes welding for the day. I didn't check the current draw, but the
>>>>> machine was set at 280 inches per second, 18 Volts, with .035" solid
>>>>> wire. Perhaps 5kW input. Charging rate was medium, there was good
sun,
>>>>> but almost no wind, which was nice because I could leave the shop
>>>>> doors open. When I quit for the day, my wife commented that battery
>>>>> state of charge had dropped 6 Amp hours, and that she'd used the
AC in
>>>>> the office for a couple of hours. On this project, like most others
>>>>> here, there wasn't any penalty for being off-grid, which is way cool
>>>>> IMO.
>>>>>
>>>>> Wayne
>
>
>
>>> <the Blunder From Down Under wrote>
>
>
>
>>> Ah Wayne, it looks like your saying 5kW for 1.6 hours and claiming that
>>>
>>>> it equates to 6 amp hours.
>>>>
>>>> Would you like to refrase that amd perhaps look at the maths.
>>>>
>>>> You use of units may be suspect. And your numbers would suggest
that you can only work when the sun is out.
>>>>
>>>> 5Kw input for 1.6 hours at 24V looks suspiciously like 333Ah.
>
>
>
>>> I started at about 8AM, and I finished up at about 4PM. During that
>>> time, 2000 Watts of tracked PV was doing its job, along with a tiny
>>> bit of help from 1300 Watts of wind generator in the AM. Duh!
>
>
>
>> 5kW input wonderful. Yes I made a mistake, I used 100 minutes when
in fact you meant 8 hours. Sorry. So this would be 5kW for 8 hours which
is of course 40kWh which is 1666.66 Amp hours. Is this your wonderful
two days autonomy at work.
>
>
>
> No you Baron of Blunders, the largest part of the shop consumption was
> (about) 5kW for 100 minutes.
Welding;
100min / 60 = 1.6 hours X 5kW = 8000kWh / 24 = 333Ah
You had the demand part nearly right the
> first time. You simply neglected to account for the balance of the
> demands (all the house loads, about 4 kWhrs),
House;
4000Wh / 24 = 166.6Ah
and the *entire* supply
> side (about 12 kWhrs).
Input;
12000Wh / 24 = 500Ah
Total;
333Ah + 166.6Ah = 499.6Ah
Hmmm no deficit here.
Well Wayne you have claimed a 150Wh deficit. I may be a bit of a skeptic
here, but, some how I just can't see that all the other things you would
do in a workshop for the task would only use 150Wh. It looks like you
you did 100 minutes of welding then watched TV for the rest of the day.
You also claim 12000Wh input. What is this based on. Being summer in
your part of the world + the fact that hot panels have a reduced output
can it be that you are simply multiplying the rated output of the
panels by six. What was the logged input for the day? Surely you monitor
your system? Or is all of this just a guess?
Why you're now trying to multiply the short
> term shop power demand by 8 hours is between you and your therapist.
In fact you said "I started at about 8AM, and I finished up at about
4PM." This is some what longer than 100 minutes. With an input of 5kW.
The question remains; Can you make a coherent accounting of your energy
use/input for the day?
You see, if Too_Many_Tools is to set up an off grid workshop he might
find the actual numbers useful in deciding what he will do. How much
grinder time is 150Wh. It's just that 100 minutes work and the house
seems like you think that 100 minutes a day is a good days work.
I will give you as many attempts as you need to make sense. OTOH I don't
think you can balance your numbers. Surprise me.
>
> Face it man, you're busted. If there's a responsible authority
> controlling solar installers in your area, reading such a fundamental
> lapse in critical thinking by someone in their charge, then the writer
> would at the very least be called onto the carpet for remedial
> training. Not that such would do much good if he hadn't gotten the
> basics down after 20 years.
>
>
>> The biggest blunder - YOURS.
>
>
>
> Sure George, a system that can supply a day's use of workshop and all
> the house loads as well, and come out with a 150 Whr deficit is
> obviously just one giant blunder.
>
> Get help man.
> Wayne
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