I wouldn't go that far.
Since you're not in the US, the question becomes "What are the economics for grid-tie solar"?
Usually when the response is "if you have grid available use it, and don't do off-grid solar" that's because batteries+solar panels are basically impossible to get to be same $/kwh as what you pay for grid power.
But since you're going to have batteries no matter what, that changes the equation. Now it's just what do solar panels (and appropriate equipment) bring to the table.
And not knowing where you're located and how the POCO rules and local laws work for power generation it's impossible to make even an educated guess on whether it's economical.
Same with your house - if you're going to have batteries anyway, then adding solar panels may be economical ( worth the additional cost).
For the business end - I'd make sure that whatever you do is compliant with the equivalent of OSHA laws/regulations.
And I'd plan on paying an engineer to design the installation.
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Hello Jason,
Thank you for the welcome.
Been lurking here for quite some time now - just reading and following along.
I have two real world needs.
1/ I need to power a communications system. Load is 6Kw today. Its a new installation so growth over time will happen. Grid power is not great. We get daily load shedding - so our grid power goes down every single day without fail. Mostly for 8 hours at a time, but sometimes longer (12 hours) and sometimes we can be "load shedded" twice for 8 hours at at time in a 24 hour period. The building has a 3 phase genset that is brought online when power goes off but sometimes it does not come on. Mostly it does but on the odd occasion it does not. So i need to put in a fairly big battery bank.
My loads are all 220v - not 48v telecom. So i need to run a decent inverter and need N+1 redundancy, hence looking at Exeltech. From what i have been able to find nothing is better then Exeltech - wave forms i have seen show Exeltech as the best out there. Exeltech can do 48v, 96v or 144v.
I need a BIG battery bank to get as much UPTIME for the 6Kw load as possible. I would want at the very very least, 4 hours UPTIME on battery. If the genset does not come on, 4 hours is not going to save the day but it gives us time to scramble to get something going in time (one hopes)
So batteries.........
Cant use FLA as its inside a server room. So AGM's. OR LiFeP04?
Leaning towards LiFeP04 for a number reasons one of them being weight is an issue here - cant run 4 tons of Pb which is what i have seen with BIG 2v batteries in a 2500AHr 48v setup. We are on the forth floor of the building and the owners are already antsy about us putting our big antennas on the roof because of weight - and the antennas don't weigh 4 tons, so......
At 48v we will have no choice but to run several strings and as far as possible i want to avoid parallel strings.
Hence considering going to 96v or 144v - to get a decent amount of power in the system without using parallel strings - LiFeP04 to cut down on weight and space requirements - not to mention the sustainable current draw these things can give out, only needing a PSOC etc. Also with sometimes only having an 8 hour (sometimes less) window of grid power available to charge with before the next round of load shedding hits, being able to charge at C1 or C2 if needed is a bonus. I am NOT even remotely considering solar charging for this - i have the roof space but as i have read over and over - if we have grid - use it and forget all about solar. My wife is a rabid tree hugger/greenie so this does not go down well but it is what it is.
I can run a 3 phase charger if needed. I would like 2 x chargers for redundancy.
so 48 x 3.2v LiFeP04 cells = 144v system. No parallel string. Staying between 80-30% SOC means we can get 50% of the rated amp hours of the battery. Looking at 700Amp/Hr or 1000Amp/Hr cells. 1000amp hours at 144v is a LOT of power.
This is for comms. Sometimes we get load shedded for an 8 hour period twice in 24 hours, sometimes during load shedding the standby genset does not come on. Sometimes there are Diesel shortages so even if the genset does come on it runs out of fuel. Its a mess. The only thing we can do is put in as much power as we can afford and we cant have too much given the flakiness of the situation here. Budget on batteries is 30K USD so probably 700Amp/Hr cells.
2/ Home system - all the same issues except the loads are not mission critical but still nice to have a big reserve of power available and still want to avoid the parallel strings. At home its probably better to stick with 48v to keep it simple and i WOULD want to do solar there but given its best to stay under 50v if possible, and at home there is no REAL need to go above 48v, charging with solar is not an issue so can forget the charging big voltages with solar part of this. I did not realize over 50v was an issue but given the reservations being raised so far it looks like forget bigger voltages at home. It seemed the higher the voltage the better the efficiency but i see now, only up to a point
Any input gratefully accepted.Leave a comment:
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Howdy sammy sparrow and welcome to Solar Panel Talk.
I am not a designer. However I know when you go over 48 volt it opens up a can of worms from a rules and regulations perspective. My brother has a hybrid system that is 120volt, (60 x 2V batteries) this was done as he has 3 phase equipment that needed it. I think unless you have high drawing appliances ( 3 phase) you just dont need to go over 48 volts and incur the extra hassles that that can bring.
There are much more knowledgeable people around the place that might chime in, is this a hypothetical question or do you have a real world solar system in mind if so what is it, re charging issues , YES, you need to have enough PV (asuming you are talking PV) to charge the batteries back up and I think special CC that can do over 80 amps (not totally sure on that bit)
CheersLeave a comment:
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OK thats a good reason in the USA.
What if you live in Utopia? What if the NEC is not part of your world?
What are the different aspects to the battery setup over 50v?
Apart from "Code" issues, what are the practical day to day issues one must consider?Leave a comment:
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Because going over 50V changes what you have to do with batteries if you are doing an NEC compliant install (which if you're doing it in USA you want to be NEC compliant.)
NEC 690.71
(B) Dwellings.
(1) Operating Voltage. Storage batteries for dwellings shall have the cells connected so as to operate at a voltage of 50 volts, nominal, or less.
Exception: Where live parts are not accessible during routine battery maintenance, a battery system voltage in accordance with 690.7 shall be permitted.
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96 or 144v instead of 48v
Wondering if going to a higher voltage battery pack makes sense. The inverter system i am after (Exeltech) offers 12,24,48 and 96v as standard (pick one). They can do custom voltages. So 144v would be possible.
Reason for higher voltage is to be able to run one string of batteries in series so as to to get higher amp/hr capacity without running parallel strings of batteries. Down the road if we need to add more capacity then we would only need to go to one parallel string etc.
What are the practical issues in going to say, a 144v inverter system?
Any issues charging a higher voltage bank from solar array?
If the inverter comes configured as 144v and i get a charger that can do the 144v charging, what other issues are there to think about?
Why are higher voltages not more common in general for off grid and back up power systems?
Leave a comment: