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Author Topic: Easterdown Off Grid - Generator Question  (Read 22691 times)
V
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« on: November 26, 2013, 08:35:26 PM »

Easterdown phase one is nearly water tight (SIPS being cladded today) -


And I'm looking at the following spec for the electrical system:

6840 kW Solar
Sunny Boy 5000 GTI
1000aH FLA (48 volt system)
Victron or Sunny Island (not yet decided)

Sadly it looks like the right 'Mister Lister' isn't going to come along, so we are looking at an alternative Diesel Generator. SMA thought a 5kva Generator would be OK.

Any thoughts? Can we get by on 5kVA?

At the moment it looks like we'll be going into the cabin (as we call it) with the batteries and a generator.

All opinions greatly appreciated.

Vickie



* Cabin2.jpg (64.11 KB, 800x550 - viewed 373 times.)
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9.7 kW of Solar PV, 3x 3000 SMA Sunny Boys, 1x SMA Sunny Island  8.0 and 1848 aH (C10) of FLA - 3.3kVA Honda generator converted to LPG
camillitech
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« Reply #1 on: November 26, 2013, 09:20:01 PM »

Don't be impatient, you're building your dream home, however if you really can't wait then this is what you need http://www.ebay.co.uk/itm/lister-petter-diesel-generator-ts2-only-572-hours-415-240-single-phase-3-phase-/221324276457?pt=UK_BOI_Industrial_Tools_Generators_ET&hash=item3387f472e9 though you could do better if you wait.
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
V
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« Reply #2 on: November 26, 2013, 11:22:00 PM »

Sigh.

It isn't impatience. It is just a matter of running out of time.  The idea to build in two phases came about because we wanted to help our wonderful landlady who has been bravely adjusting to the sudden, untimely death of her partner. She knew it was likely that she would need to sell the house we are renting, or come back here to live herself. We werenít keen to live in a caravan. We werenít keen to rush the design. We didnít want to stand in her way. So we asked our architect if there was some way to get on site quickly.

But in the course of this 'extendable permitted development' idea we realised we had enough design to apply for planning permission even though it is possible the design may change a lot. It doesn't change that we still need and want to help out our landlady.
 
This means that we need to have a lot of the infrastructure in place pretty soon, like the off grid electrics. So we are thinking about batteries plus charger plus maybe:

http://www.justgenerators.co.uk/pages/hyundai-dhy6000se-generator.htm

Wasn't sure if this would keep our lovely new FLA's charged enough in January/Feb.

V.
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knighty
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« Reply #3 on: November 27, 2013, 12:23:23 AM »

personally.. if you can't get the right generator for the job yet (a nice old Lister) you might as well get a cheap (bit crappy) little petrol generator...

a couple of kw will do to get you going, you'll just have to run it for a lot longer


it won't be as efficient, but it'll be £1000 cheaper which will buy a lot of fuel...

then in a couple of months from now when the right generator comes along you can grab it with both hands



EDIT: found this
http://www.ebay.co.uk/itm/Lister-diesel-generator-3-5-kva-excellent-original-condition-engine-/251383019500?pt=UK_BOI_Industrial_Tools_Generators_ET&hash=item3a879877ec


also how long it will be before you get your solar panels installed and your expected output... there's a website I can never find/remember the name of, it's something like pveits.com I'm sure someone will be along soon to provide a link...

I'm wondering if with 6.8kw of pv installed if you'll need a generator at all (apart from emergency backup).... which means you could just get a cheap little portable one and keep it forever.. it would save you some time/space/money/maintenence ?
« Last Edit: November 27, 2013, 12:30:36 AM by knighty » Logged
camillitech
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« Reply #4 on: November 27, 2013, 06:34:46 AM »

Knighty speaks with much wisdom, sure that generator will work http://www.justgenerators.co.uk/pages/hyundai-dhy6000se-generator.htm but it's a 3000rpm screamer and will be scrap in less than ten years. It's self contained which is an advantage as you won't need to build a shed for it, just a lean too or something would do. It'll probably be quieter than a Lister and certainly much lighter and is a 'plug and play' machine, so I suppose you could just buy it and 'go'.

Good luck, Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
V
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« Reply #5 on: November 27, 2013, 08:46:01 AM »

Thank you both so much. Space hopefully isn't an issue, I think:
Secure storage built in one bay of the barn that has concrete floor:


and finished structure, insulation and timber cladding in progress:


I'm trying also to understand the relationship between generator kVA and amp-hours. If the battery bank is wired up to be 48 volts 1000aH, and if we are using 6 - 9 kwa  per day, worst case, is that:

48v x 1000ah = 48kW
discharge only by 20% = 38.4kW
At which point generator switches on and if:
Generator 3.5kVA then approximately 3 hours to recharge
Generator 5 kVA then approximately 2 hours to recharge
Generator 7 kVA then approximately 1.5 hours to recharge

??
Thanks,

Vickie



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« Reply #6 on: November 27, 2013, 09:39:53 AM »

if you take the battery bank down to 20% of charge it won't last very long...

if you keep it above 40% it'll last a lot longer (a lot lot longer)

and you don't really want to load your generator past 80% of full load to keep it efficient/healthy

a long slow charge is better for the batteries too


any idea when you'll get your solar pv in ?  this is the important bit... if it'll be soon then the generator only needs to be temporary, if it's going to be a long time then you really need a proper generator setup

I'm guessing once you have your PV in you won;t need a generator at all
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« Reply #7 on: November 27, 2013, 10:11:28 AM »

Hi ,
     Knighty put up a link to a nice Mister Lister,£800.00 or so.If it was anywhere near your place you should grab it immediatly3.8kw from a lister is worth more than a bigger kw from other models(dont ask  Grin). Then If you see the Lister of your dreams you will be able to sell the £800.00 one and not lose any money on it.I have a silent running one just like Paul put up on that link.Mine has been used for a few years now and I cannot complain.It does buzz aloing at 3000rpms but you can barely hear it from 100ft away.If noise is an issue then this might be the answer but the Lister Knighty put up would be the proper job.
                  Biff
 NB,
We have run our silent 5kw geni for the first time since the beginning of the summer,She says over 5 months ago.It started up with very little hassle,Just a loose comnection to the battery,First turn and away it went.It drank 4.5 ltrs for 6 hours running, but only has an approx load of 2kw.It is not a Lister by a long shot but it seems to be very reliable.It cost approx 750 euros delivered here.It came out of the crate half full of diesel,full of oil.Just turn the key and away it went.
« Last Edit: November 27, 2013, 10:19:05 AM by biff » Logged

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« Reply #8 on: November 27, 2013, 10:28:49 AM »

if you take the battery bank down to 20% of charge it won't last very long...

and you don't really want to load your generator past 80% of full load to keep it efficient/healthy

a long slow charge is better for the batteries too

Have I misunderstood? If I take the battery bank down from 48 to 38.4 this doesn't keep the battery bank at 80% ?

How do I avoid loading the generator? Can this be done using a setting on the charger?

Hi ,
     Knighty put up a link to a nice Mister Lister,£800.00 or so.If it was anywhere near your place you should grab it immediatly3.8kw from a lister is worth more than a bigger kw from other models(dont ask  Grin). Then If you see the Lister of your dreams you will be able to sell the £800.00 one and not lose any money on it.I have a silent running one just like Paul put up on that link.Mine has been used for a few years now and I cannot complain.It does buzz aloing at 3000rpms but you can barely hear it from 100ft away.If noise is an issue then this might be the answer but the Lister Knighty put up would be the proper job.
                  Biff

Shepton Mallet is pretty close. May just give them a ring in a moment.


any idea when you'll get your solar pv in ?  this is the important bit... if it'll be soon then the generator only needs to be temporary, if it's going to be a long time then you really need a proper generator setup

I'm guessing once you have your PV in you won;t need a generator at all

We have wondered about that. But it is December. This is the PVGIS site with our (hopefully) parameters in.

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« Reply #9 on: November 27, 2013, 10:33:56 AM »



48v x 1000ah = 48kW
discharge only by 20% = 38.4kW
At which point generator switches on and if:
Generator 3.5kVA then approximately 3 hours to recharge
Generator 5 kVA then approximately 2 hours to recharge
Generator 7 kVA then approximately 1.5 hours to recharge


Vickie

This bubble needs bursting, sorry.

Recharging bats is not a simple matter of amp rating of charger times hours of charge.

1, The charger will only do its rated amount when the battery is quite flat (IE the bulk phase so up to about 80-90%, the remaining 10-20% will take about the same amount of time again).
2, After the bulk phase the charger output reduces drastically.
3, The absorb phase takes TIME not high amps.
4, Using the gennies peak output times the time it is running is forgetting all of the above PLUS the inefficiency of the charger PLUS the inefficiency of the charge process.



Recharging FLA batts to 100% takes TIME lots of TIME.

Failing to recharge to 100% often enough will reduce the bats total capacity quicker.

So a daily charge of a few hours is ok but you then need to consider a weekly charge of 8-10 hours ish.

Plus a monthly charge doing an EQ which needs to be done after a full absorb so think 10-12 hours ish in total.

Ideally what you need is a large genny & charger for the bulk phase & a small genny & charger for the absorb & EQ phases.
« Last Edit: November 27, 2013, 10:43:58 AM by Justme » Logged

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Total bank 4350 amp/h 5C
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« Reply #10 on: November 27, 2013, 10:39:13 AM »

Vickie

With a 6480 Kw PV system you will have no problem keeping your batteries charged!  Grin
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« Reply #11 on: November 27, 2013, 10:39:41 AM »


Have I misunderstood? If I take the battery bank down from 48 to 38.4 this doesn't keep the battery bank at 80% ?




First a 48v battery bank is not 48v when full its more like 51.2v

Second 38.4v is going to KILL you battery is very short order.
(unless under heavy load & it recovers when the load is removed to above 48v)

You dont use 48v to 0v as the working range to calc your SOC or DOD.

Your ideal min voltage is more like 48.8v which is equal to 50% SOC / DOD
SOC = State of charge
DOD = Depth of discharge
You seem to be mixing them up.
80% SOC = good
80% DOD = bad
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1200watts solar 120vdc
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24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h 5C
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« Reply #12 on: November 27, 2013, 10:42:59 AM »

Knighty speaks with much wisdom, sure that generator will work http://www.justgenerators.co.uk/pages/hyundai-dhy6000se-generator.htm but it's a 3000rpm screamer and will be scrap in less than ten years.

That genny will have a life of less than 2000 hours before the engine needs major work that will cost more than its worth to fix. Even the next range (Pramac P6000s) up that costs 3 X as much will only do 4000 hours (better engine) before needing major fixing.
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1200watts solar 120vdc
FX80 Solar controller
Victron 12v 3000w 120a
6kva genny
6 x 2v cells 1550amp/h 5C
24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h 5C
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« Reply #13 on: November 27, 2013, 10:52:43 AM »

I think Vickie is suggesting discharging to a capacity of 38.4kWh not Volts
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« Reply #14 on: November 27, 2013, 11:08:22 AM »

I think Vickie is suggesting discharging to a capacity of 38.4kWh not Volts

I think that's what I meant. Sorry, I don't have the language of all of this yet.

That if the Battery bank rating is:

48 Volts 1000aH then IxV=W, 48 x 1000 = 48 kiloWatts

If our requirement is 9 kiloWatts to run house, fridges etc. for 24 hours then we will have 'removed' (??) this from the batteries, is it right to say

48 kW subtract 9 kW is 39kWatts left

39 kiloWatts divided by 48 volts leaves 812.5 amp hours in battery meaning we've removed approximately 200 ah, leaving 80 percent of charge in batteries?

Is this right thinking?
« Last Edit: November 27, 2013, 11:35:38 AM by V » Logged

9.7 kW of Solar PV, 3x 3000 SMA Sunny Boys, 1x SMA Sunny Island  8.0 and 1848 aH (C10) of FLA - 3.3kVA Honda generator converted to LPG
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