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Author Topic: Easterdown Off Grid - Generator Question  (Read 23375 times)
offthegridandy
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« Reply #15 on: November 27, 2013, 11:59:55 AM »

Hi V,

hope my 2 penny worth will help a bit.

First off your rate of battery charging from the genny; you need to bear in mind that nothing is 100% efficient.  By the time you've created 240VAC then converted it to 48V dc you'r getting losses all the way. 

Max genny size.  The max rate of charge for 1000Ahr set of cells is going to be 100amp per hr so in theory a 5k genny would do.  I would give consideration to sizing the genny to support your max likely load.  Not the normal house but something that  can be battery charging plus run a excess load (eg a welder). I'd recon on about 8KVa from what you've told us. Ignoring solarPV, if you discharge to about 45 V then I would predict about 5 to 6 hrs to fully recharge the cells.

Now consider this, with PV charging the cells as well you need to have an inverter charger and solar controller that are capable of recognising each other s existence.  If not you can end up with a situation where the cells start a genny charge cycle say early morning, then the sun starts the PV supplying. The inverter charger doesn't "see" the PV input and merrily runs a full charge taking 6 hrs even though the sun is shining.  I used to have this scenario with our old Trace inverter/charger.  I now have Outback FM80 PV charge controller and Outback inverter/charger and the charge rate gets modified to reflect the PV input.  Of course you can pratt about turning the genny of manually but I have to have a system that runs automatically with out attention.

By the way, get the Lister that Paul found if you can.  These are serious bits of kit not toys. Cheap to run, reliable, easy to repair.  Do filter changes by the book(ish) say every 400 hrs. Even if everything else fails you can run the house/freezers whilst waiting for spare parts.

Andy
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8 KVA Lister TS2 Startamatic Genny
24 Volt 1000amp battery bank
Outback VFX3024
4.6 Kw PV array ground mounted
Outback Flexmax 80
2 X Flexmax 30 PV CC
2.5 Kw WT H Piggot design 4.5 Mtr Dia AC coupled
12 Mtr free standing Tower.
u/floor heating from oil boiler cross linked to 12 K wood stove
V
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« Reply #16 on: November 27, 2013, 12:13:26 PM »

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'
If I'm reading that correctly it's cheaper than a Honda half the size? What's the catch (aside from "it's not a Honda"  Wink), or am I just looking at the wrong things?

Quandary is:

Have contacted 3.5kva Lister man, feel I MUST see it actually running with a load on it or I'm just a 'stupid head'.

BUT may miss it.

5kVA Hundai - simple, has a warranty, it may be throwing 1000 pounds at a 1 year solution.   wackoold

But you all think a 3.5 kva lister is as appropriate as a 5kva generator? Because of the 1500 vs 3000? or Huh

Many thanks for all replies so far. All opinions and insights gratefully received.

« Last Edit: November 27, 2013, 12:52:26 PM 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
Justme
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« Reply #17 on: November 27, 2013, 01:27:36 PM »

Yes your numbers make sense now.

Down side to keeping to the 80% SOC is that your charge will always be in the absorb phase & not the bulk phase. As said earlier absorb charges are limited the amps that the battery can absorb so are much slower & more inefficient (electrically & for running the genny under low loads, ideally you want the genny loaded to about 75% of its constant output level) than the bulk phase.
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Navitron solar thermal system
30 x 58mm panel 259L TS
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
V
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« Reply #18 on: November 27, 2013, 02:20:42 PM »

Thank you so much for taking the time to look through my numbers, I apologise that I don't really know how best to express these ideas, thank you for putting up with me.

So may I check what understand from this?

If I take 200 aH out of the
batteries in given day, with the ?? (whichever 5 or 3.5) kVA generator I will be running an 'absorb phase'. Would I need to program the charger (Victron or SI) to recognise an absorb phase of a certain amount or duration?

If 3.5 kVA Lister, then what would the load (the batteries plus charger, I assume) look like to the Lister?  Would the load need to look like a 2kW load to be 75% of the output level?

Just trying to understand. Grateful for all help.



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knighty
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« Reply #19 on: November 27, 2013, 02:49:38 PM »

you just need to buy the right inverter (to convert your 48v at the batteries to 48v for the house)

the right one will do everything automatically,

if the batteries get too low, it'll start the generator, then stop it when they're full

(it'll also do an equalisation charge which you need now and again... not technically right but just imagine this is where the batteries are a bit overcharged to make sure they're all full and healthy)

you can also set/program in the charge rate, so you can set the max to however many amps you want

I don't have any personal experience with these... but a lot of folks here do and should be able to recommend the right one to buy
(I'd hate to recommend the wrong one)



all this said... is there no way you can speed up the PV install ? - if you use the generator for a year you're probably going to end up close to 3000 out of pocked you wouldn't have had to spend
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offthegridandy
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« Reply #20 on: November 27, 2013, 03:07:09 PM »

Sorry V if I'm asking something you've already covered; but do you envisage having mains power eventually.  I see you spec for a Grid tie inverter.  You will need an inverter/charger.  If you are not going to have a grid connection then I would not assume that you'll never need a genny.  Plan on the basis that things can fail.  If you rely soley on having PV and component fails then your freezers and income fail too.  So if you are to have a genny get a lister.  It is less likely to fail than anything else available.

Even Biff with WT and solar still keeps a genny to hand. But there is no point having a stand by unit that don't start the time you need it.

Andy
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8 KVA Lister TS2 Startamatic Genny
24 Volt 1000amp battery bank
Outback VFX3024
4.6 Kw PV array ground mounted
Outback Flexmax 80
2 X Flexmax 30 PV CC
2.5 Kw WT H Piggot design 4.5 Mtr Dia AC coupled
12 Mtr free standing Tower.
u/floor heating from oil boiler cross linked to 12 K wood stove
V
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« Reply #21 on: November 27, 2013, 03:24:25 PM »

Not a problem, just so grateful for the help and insights.

It is unlikely we will ever have a grid connection although our neighbours, the Soil Association, had been thinking to bring one to the neighbouring farm, but this is now looking unlikely.

I think the reason we have been given a spec for the Sunny Island and Sunny Boy is to do with the feed in tariff, not that this is terribly important. Isn't the Sunny Island or Victron the inverter charger bit?

Open to hear about alternatives. And yes, we absolutely need a generator. But someone this end is telling us we need a fisher 12kVA and that seems a bit excessive.

And re: the 'when' of the PV install, I think we are talking month(s) not a year. It depends on whether I can convince the planners that a 24 panel ground mount array (as opposed to the roof mount we currently said we'd do) at our remote smallholding is permitted development. We weren't clear that this was necessary at the time and the plans went in without it.
« Last Edit: November 27, 2013, 03:36:44 PM 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
AlanM
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« Reply #22 on: November 27, 2013, 03:56:49 PM »

Your pv going through a grid tie inverter will back feed through your inverter charger, rather than triggering the charger. So it is actually connected via the consumer unit and then back into the inverter(not the GTI one) via its AC out and from there into the battery via the Dc cables. This is different from when you start the genny, It is connected to the AC in side of the Inverter/charger and then the charger does its thing.
This is how my system is configured, using a Victron Multiplus, not sure about Sunny islands. The victron has a programmable relay which can do gen autostart.
The FIT is useful. At the least it will cover your sytem costs eventually, or pay for some diesel for the gen.

Alan
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« Reply #23 on: November 27, 2013, 04:05:54 PM »

The FIT is useful. At the least it will cover your sytem costs eventually, or pay for some diesel for the gen.
Alan

Thanks for this. That was our thinking, that the FIT would pay for our diesel. Just out of curiosity, do you have an opinion on what size of generator we might need?

Vickie
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Justme
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« Reply #24 on: November 27, 2013, 04:27:35 PM »

For everyday use you need one capable of coping with the inverter chargers at full output (lots of chargers have a PF of less than .7 so factor that in too, oh & get used to working in kVa not watts especially with Victron stuff) plus cover any base loads that might be on at that time.
(we tend to load up the genny when it is on doing washing & any other heavy loads especially in winter when solar power is thin on the ground, in summer we make more than we need so only run the genny if absolutely necessary)

For emergencies (like battery or inverter failure) you need it to be able to cover all of your loads.

Best would be two, one big one for emergencies & one smaller for every day usage.

How big an inverter are you planning on?
(not the solar to mains one but the battery to mains one)

Again there are two ways to go.

1, Large enough to cover all you loads at once.
2, Sized to cover most daily loads but with the abillity to merge the power with the genny for peak loads.

Have you done a power audit to see exactly how much energy (kWh) you will use per day & also what the peak amount of power (watts) will be?

Just knowing your total daily consumption is not enough.

You could have a 3kw pump that runs for 10 mins so only uses 0.5kWh but would need a genny of about 12kw to start it.
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Navitron solar thermal system
30 x 58mm panel 259L TS
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
biff
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« Reply #25 on: November 27, 2013, 04:54:08 PM »

Hi V,
       Just when you were settling down to get your head around all the figures,I come along and upset the applecart.
  These chargers,controllers,etc,etc,, are expensive. They demand a minum of 5kws to drive them,
    However,If you had Knighty,s Mr Lister connected to that PMG that Puddenbag has for sale,set to ratio and driving the PMG at 400rpms.It would charge your batteries to whatever voltage you set the controller to.
              This would mean that your batts could be charging nicely while Mr Lister is running 2kw into the house.It is not as complicated as it seems,it is just that the PMG dleivers 48 to 60volts necessary without all the hassle of an AC charger.
               Biff
   
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« Reply #26 on: November 27, 2013, 05:07:20 PM »

For everyday use you need one capable of coping with the inverter chargers at full output (lots of chargers have a PF of less than .7 so factor that in too, oh & get used to working in kVa not watts especially with Victron stuff)

Not quite sure how to do that, is it KVa x power factor?

How big an inverter are you planning on?
(not the solar to mains one but the battery to mains one)


One quote suggests Victron 48DC VE 5kW I/C
Other suggested Sunny Island 8.0H and Sunny Island Charger 50 (around 2kWp) Huh

Have you done a power audit to see exactly how much energy (kWh) you will use per day & also what the peak amount of power (watts) will be?

Just knowing your total daily consumption is not enough.

You could have a 3kw pump that runs for 10 mins so only uses 0.5kWh but would need a genny of about 12kw to start it.


On our audit we looked at various scenarios with peak power. One being 'if everything was on at once' which is a bit silly. But things that could just go on - ie fridges and freezers comes to 2178. We know that the big pump "needs 2Kw for 4 seconds when starting up through the capacitor." The well pump is rated at 675 watts and I've left a question for his office regarding its startup power. This brings the unavoidable peak clash to about 4.2 kW, possibly?

Thanks for looking at this,

Vickie

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« Reply #27 on: November 27, 2013, 05:10:14 PM »

Hi V,
       Just when you were settling down to get your head around all the figures,I come along and upset the applecart.
  These chargers,controllers,etc,etc,, are expensive. They demand a minum of 5kws to drive them,
    However,If you had Knighty,s Mr Lister connected to that PMG that Puddenbag has for sale,set to ratio and driving the PMG at 400rpms.It would charge your batteries to whatever voltage you set the controller to.
              This would mean that your batts could be charging nicely while Mr Lister is running 2kw into the house.It is not as complicated as it seems,it is just that the PMG dleivers 48 to 60volts necessary without all the hassle of an AC charger.
               Biff
  

Would Mr Lister be putting 2kW into the house via the Charger? Would this be AC? Sorry to be so stupid. And Hyundai can't do this?

and this PMG, do you mean this - http://www.navitron.org.uk/forum/index.php/topic,21474.msg247923.html#msg247923 ?

I'm intrigued. And isn't that what an applecart is for?
« Last Edit: November 27, 2013, 05:24:52 PM by V » Logged

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biff
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« Reply #28 on: November 27, 2013, 06:53:19 PM »

Rite,!
     Now this is not what you call a done deal but it is very very possible.
                     You have your Mr Lister running normally.Running the house through the AC,however,A PMG,similar to neils or even neils, has a pully fixed to the shaft which gives it a rpm of 400 while the gen is turning at 1500rpm.
         So the PMG will be pumping out a healthy 1kw charge through its normal wind turbine controller.This will keep the batt volt up to the max and give your batts a nice charge in direct DC over a period of 4 to 5 hours .Meanwhile your AC side will be performing as usual,so when the time comes to switch over to batt power you should find them full.
     Now when the batts reach the required dump load voltage,say,58.9 ,the controller relay will redirect the charge to the dump load but in this case instead of doing that,it will switch off the geni and switch over to batts.When the voltage drops down low enough,the relay fires up the geni and you are off charging the batts again.
 I know,,Sheer genius ,did I hear you say? tomatosplat. Did I do this myself,?  Errrr no, but I nearly did.
   I know that some of the members will throw themselves back in their chairs and screech about those round things that footie players kick round the field.But my intentions are honorable.I am cutting nobody,s throat but my own.I think I have dug myself a fine hole.(tunnel)
                                                             Biff
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AlanM
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« Reply #29 on: November 27, 2013, 07:46:34 PM »

hi, re the size of your genny, it really depends on your load sizes, as others have said. That said, with the victrons (and possibly others, I dont know, but someone else will) there is power assist, where the victron will boost the Genny supply to cover peaks. For example, Genny on and supplying 2.5kw, you switch on 4kw load, the victron will stop charging, and immediately boost the genny output by 1.5kw from the battery. Depending on the size of the multiplus, you can therefore boost the generator output, which means you do not necessarily require a big generator.
As it happens, mine is the Multiplus 48/5000/70 which i think is the one you mentioned. Its peak output is 7800W, with continuous at 4250W. As for the generator, I have Lombardini diesel, running as i type... Winter gloom Sad but i have in reserve a Mr Lister TS2 which is a 6.5kw model. I need to build it a house first, before it moves in.

Alan
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