End of grid lost in the wild installation

znourf

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Mar 15, 2017
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Ok so my wife andi have just bought a house in Sweden.
We are at a few miles from anyone and we are at the end of the line of a near8kvpower line.

But the line isn't buried and we are right in the middle of the forest. Worse between us and the higher voltage line there is a holiday town that is used in the summertime . But also for Christmas. And a few other festivies.

So if there is a storm a tree gets blown over and since we aren't priority there is a power shortage for 4-5 days.
Same if there is a lot of snow , then it can last a bit longer because access is hard.

The most annoying through is the voltage drops on the line. I used a triphased voltage recorder for 5 days and the voltage is hectic. with 50 volt lows when the pump from the well (3kw triphased pump) or the reversible heating/ AC starts up (4 kw)
.
The old owner was bothered with his computer crashing so he had to invest in a UPS. The oven and electric heating didn't heat much on some occassions. Or in some cases the voltage would go so low that the counter would cut . Now since i haven't seen it myself it might be the transformer who has a cut of when the voltage drops too low.

So here is my plan.

Build a 18650 based powerwall 14S50 to 100p haven't decided yet , can get NCR18650GA for 3.20 /piece for 1400 pieces; but firstgot to install my workshop , mill , lathe and other tools like a spot welder to make 18650 packs,to see what it will use up on a normal day since i work from home.

I also have a 7kva diesel generator (triphased) that i would like to use in case oflack of sun like in winter where we only get 3-4 hours of decent sunlight or simply if i'm using a lot of energy and the packs are low or i consider using up lots of power in a short time.

I'm planning oninstalling 2 to 6kwh solar panels (depending on the consumptiontaht i will mesure)on the roof which is like 90 m straight to the south. Or a solar flower or 2in the garden

And maybe a few bladlesswind turbine (vortex bladless) if the municipality is ok with it and if there is enough wind in the year.

Then i will need to find a way to cope with the voltage issue.

Now i was thinking of coupling a 500 farad ultracap bank to the batteries to solve the issue of sudden current draw but is there an inverter that can allow using on grid and off grid power at the same time to regulate the voltage ?
Can i have on a clowdy day the generator start up if the batteries are to lowand still have the solar panels help charge up?

Having fiddled a bit with ultra caps i was thinking of using a seperate inverter that can cope with large voltage drops and still send out a triphased current but then comes the question of charging and balancing the ultra caps. i can do it with resistors or a few fets and use a programmable li ion chargerbut is there anything out there that is made for this out of the box ?

Is there any system out there that can manage starting a generator ? i guess yes .

So any insights, help advice , links or names would be great.

thanks
 
Tjena!

Yes there are inverters that take care of on-and off grid at same time. That can sell back if needed and use from battery. Ie it can combine what ever you have incoming. In your case it might not be needed to sell back to the grid and if so its a lot cheaper to go with an off grid system directly.

Most off grid system will be able to combine from pv + battery + grid depending on you have set it up.

The generator is the question. You can have an transfer switch on the inverter that you switch between grid and generator for instance. Or you can just hook up a big charger to the generator to feed the battery bank directly. You got endless choices there :) But transfer switch hooked up on the grid-part will solve it. Either automatic or manual.
If you make sure your bank is big enough, the charging from the generator will work better since you dont have to start it every other day. I recommend to have several days worth of capacity in the bank if needed... Winter days in Sweden arent the best :)

Personally i see no gain in capacitors. I rather prefer to just make sure that spend that money on bigger capacity bank instead. If your bank can not cope with the max load you have bigger issues from start that a cap-bank wont solve. And the initial surge is something a decent inverter will handle. Of course the cap-bank will help out if you got them kind of for free.. But if not look into how much extra it cost to add extra cells to the bank.

There is several boards/systems on ebay among other sites that do balance the caps. Take a look at them if you go that route.

Personally im using MPP stuff. They are so called cheap stuff but so far they have worked great for me. I have one 10kW Hybrid 3phase inverter. Hybrid means it has battery including grid-tie -> can sell back to grid.
I also use a PIP4048 that is 4kw nom and 8kw max 1 phase. Can be connected as 3phase if you buy 3 of them. Both above can be paralleled to have more juice.

Triggering external gen is no big problem. Either you go with a system that handle it from the start or build something on your own.

My last thing is about the cells. Tips: Take a look at LiFePo4 for instance. A lot more cycles.... Yes more expensive but if you go and buy new LiIon or others you can also check LiFe.

/D (Smland)
 
The system you need is termed "double conversion" in the UPS world.
Grid/solar power goes into the battery, an inverter is driven off the battery.

I'm certain Victron Energy have a suitable inverter for your needs, they are used on things like boats were grid power may not be available.
 
I've read a bit about Victron equipment that will seamlessly kick over to battery power when grid power drops, acting like a UPS. They can also switch on a generator when required. Very clever indeed. Up to 6 inverters can be connected in parallel or, if required, three in parallel for three phase power.

Victron may be expensive, but you get quality for the price.
 
yes i ve already looked at victron. It s more of a ready packed solution. a bit less diy which is what i m looking into. i ve just got to get the numbers on. regarding SoC DoD of 18650 li ions like the 18650ga or if there is a better suited element and saft li ion that have an excellent cycle life but are more expensive.
regarding lifepo i find strange information between 18650 like and industrial grade this getting silly. on one side they lasr 6 - 7 k cycles ont the other 18650 lifepo don t do any better than 1 - 1.5k. are they simply low tech?

And when it comes down to making a equivalent 48volt battery i can hardly find cheaper to the kw than 18650 li ions even bought new.
except lead battery but then to get the same amount of "usuable" power and energy you need to oversize it compared to li ionand it then costs more.
my calculus is more based on what is the best cost / cycle life. at least li ion don t let you down like lead and a li ion that has lost 20 % of it s capacity isn t useless since it usually continues to degrade at a near linear level.
though when it starts to go faulty then you loose the elements and it then goes all downhill very fast.

now i can find all kinds of information about 18650 cycle life. some can be foynd on pubmed some are sae papers.


some simply put once the math done explain that a cell can last for way longer if you use it chargedfrom 60 to a discharge to 40 %. but when i do my maths it seems to me that at the end unless you keep on charging above 4v what ever the SoC and DoD you simply get the same amount of energy out of the cells.
 
the znourf said:
yes i ve already looked at victron. It s more of a ready packed solution. a bit less diy which is what i m looking into. i ve just got to get the numbers on. regarding SoC DoD of 18650 li ions like the 18650ga or if there is a better suited element and saft li ion that have an excellent cycle life but are more expensive.
regarding lifepo i find strange information between 18650 like and industrial grade this getting silly. on one side they lasr 6 - 7 k cycles ont the other 18650 lifepo don t do any better than 1 - 1.5k. are they simply low tech?

And when it comes down to making a equivalent 48volt battery i can hardly find cheaper to the kw than 18650 li ions even bought new.
except lead battery but then to get the same amount of "usuable" power and energy you need to oversize it compared to li ionand it then costs more.
my calculus is more based on what is the best cost / cycle life. at least li ion don t let you down like lead and a li ion that has lost 20 % of it s capacity isn t useless since it usually continues to degrade at a near linear level.
though when it starts to go faulty then you loose the elements and it then goes all downhill very fast.

now i can find all kinds of information about 18650 cycle life. some can be foynd on pubmed some are sae papers.


some simply put once the math done explain that a cell can last for way longer if you use it chargedfrom 60 to a discharge to 40 %. but when i do my maths it seems to me that at the end unless you keep on charging above 4v what ever the SoC and DoD you simply get the same amount of energy out of the cells.

Why not consider Winston LiFePO4 cells. The figures suggest a greater cycle life, especially if you don't exceed 80% DOD. The price per cycle per Ahis quite good from the research I've done. That's the way I'll be heading for my off grid system, along with a DMPPT450 and SBMS120 fromElectrodacus.

My 18650 Li-ion system is for down lights and 12-24v Internet and weather station gear.
 
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