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Maybe the OP is not interest in Solar? maybe just an emergency UPS system with longer hours tie with the grid. I used to do this before I got into solar. I have 2 APC backup 1200 connected to 4 deep cycle batteries that serve me about 3 hours electricity for the computers and the lights when the grid power is down. when the grid power come back. it charge back the battery.
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OK. So eliminate the solar panels and drop the $115k cost down about $25k. That is still about $90k for a UPS system that has maybe 4 to 5 years of life if he takes care of that giant battery bank.
For that size electrical load using a generator will still be cheaper than a battery back up system.Comment
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Yes makes sense and you guys are quite right about the cost. The aim is to have a cost comparison and a feasibility of the system.
I have done a bit more number crunching and the total peak power required for 1 hour is 27.3 Kwh
The system offered was the following:
16 Exide 220AH batteries (not deep cycle) connected to an APC 30kva UPS (Used unit) 192 volt system costing about $5k. Suppose these run for 1 year max.
The diesel cost is about $20-$24k for 1 year.Comment
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Lets start at the beginning. What is your daily load calculations? You now state you have a load of 27.3 kw for 1 hour or do you mean you have a 27.3kwh load for X hours?
Next. What voltage are those Exide batteries? If you have to parallel more than a couple of them you will have a system that will not properly charge or discharge evenly which will shorten their lifespan.
Next. How many times will you need to use this UPS system? If it is once in a great while the batteries should be ok if you keep them charged. If you need to use them weekly you will probably exceed the number of cycles they were designed for since they are not "deep cycle" and they will fail quickly.
Again start with what load you really need to power (lights, fans, pumps, etc) and for how long. Without that info you really can't design or size your battery system.Comment
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Well the total outage for any given day will be about 12 hours. The outage does not happen continuously. The total power load as I calculated is 27.28 Kwh for 1 hour. For 12 hours 27.28*12 (Take away pumps or any other motors which only run for 3 hours a day)?
Yes I am aware of that.
Well this is how I worked out the total load: Let me know if I am on the right track.
Watts
110*23 = 2,530 (Lights need to be on all the time)
9*1150 = 10,350 (Some Fans need to be on all the time)
3*750 = 2,250 (Only on partially)
2*1500 = 3,000 (Pumps run for about 3 hours a day)
6*1150 = 6,900 (Only on for about 3 hours a day)
1*2250 = 2,250 (Only on for about 3 hours a day)
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---------27,280
So if the above run for one hour it will be 27.28 Kwh right? And if the back needs to be for 12 hours then 27.28*12 (Take away pumps or any other motors which only run for 3 hours a day)?
The batteries are 12 volt dc 220AH
The outage happen every other hour in the worst case scenario.
Thanks
Shah.Comment
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That's = 327 Kwh = 27.26 Kw x 12 hours, which means you need a minimum 654 Kwh battery. At 192 volts = 3400 AH or 256 batteries. So what good is a 192 volt 220 AH battery going to do besides be destroyed the first time you try to use it. Your price tag just went from $5000 to $80,000. The fun part is since they are not Deep Cycle batteries you get to replace them every month or two from abuse. .
Now is that what you want?MSEE, PEComment
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Well not what I had in mind but it is good to learn about alternatives and their feasibilities.
I have built a model based on your way of calculating the battery bank. Not sure how to share a Excel spreadsheet.Comment
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You do not need a spreadsheet, just post your numbers
Wattage
Hours
Battery voltage
That is all that is needed. You already gave me that with 27.28 Kw connected load for 12 hours, 27.28 Kw x 12 hours = 327Kwh. Which means if you intend to discharge the battery to 50% DOD means you need a 654 Kwh battery capacity. 654 Kwh / 192 volts = 3400 Amp Hours. 16 of the batteries you intend to use falls way short as it would take 256 of those batteries. A complete misapplication. You would be looking for 2 volt 3400 AH Deep Cycle batteries and at 192 volts you would need 81 wired in series.
Now here is the real kick in the pants. Your UPS would not be capable of charging the batteries. a 30 KW UPS using 192 volt battery comes with 200 amp rectifier. To carry the intended load and recharge the 3400 AH battery you need in 12 hours will require 400 amp rectifiers. UPS are not made to do that.
UPS and UPS batteries are not designed to do this. A UPS is made to carry the load infrequently on emergency basis only long enough to get a generator started up and running to carry the load. By emergency I mean the ocassional power outage from 1 to 3 times a year, and the generator comes online within a minute or less.
UPS batteries like the one you selected are not made for Deep Cycle application. They are designed for a very short shallow cycle occasionally. You force them into daily cycle service to 50% DOD they will be toast in a few weeks on two months at best. Your plan is not going to work. Industrial and commercial applications require industrial solutions using NG, coal, or nuclear energy.
Just based on the UPS size of 30 KVA and 192 volt battery I bet your UPS is only capable of having a 200 to 300 AH battery or enough to last about 20 minutes at full rated load. That is how they are designed. They are not designed to carry rated load for 12 hours or even a single hour. It could be done, but no one would buy them because a generator is far less expensive.MSEE, PEComment
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Yes this all make sense to me now.
I hope some day the technology allow us to generate our own energy at a reasonable price!
Thank you Sunking and everyone else for a great deal of information.Comment
...I was only looking at this as I will spend about $20k to $24k a year on diesel!
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