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off grid fisheries solar power


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Hi 

I am not so experienced in solar I just have  2years working experience going to 3 years in March next year.

I need help with the best solution for 4.1kw total load (water pumps for the fishery) and runs 24hrs. The owner would like to go complete off grid because he is spending quite alot on utility bills. Below is the load and running hours needed 24hrs.

Air blower 1.1Kw

Air blower 0.75kw

Water pump1.5kw

Water pump 0.75Kw

Regards 

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Cool info @Clement , as you noted you do have some experience so here is a couple of questions that should get us/you started ..

  1.  What is the total "peak load"?
  2. How long wil each unit run , day time - night time? , What would you say is the the total kWh that you would need if you have the time that each unit wil run.

What you are asking now is how long a piece of string is and no one would be able to tell you that , rather take the approach of creating a design of sorts and run it by the members the experience will give you an edge over possible competitors in the future. 

Looking forward to see your first go at this!!  

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4.1kW x 24hr = 98.4kWh per day (ouch!), call it 100kWh so you will need about 20kWp array. So a real cheapo solution would be as follows;

  • 6x Axpert MKS 5k in parallel (for the panel capacity, not for the output power which will be way overkill),
    • about R60k
  • Each Axpert with 10x 315Wp panels = 3.15kWp x6 = 18.9kWp (not quite 20kWp but close enough),
    • about R150k
  • Assume 8hr solar day and 14hr solar night, so your battery bank must carry you for about 14hr's on average.
  • 4.1kW x 14h = 57.4kWh supplied by battery, if you use lead acid and limit it to 50% drain you will need 120kWh battery bank.
  • 120kWh / 48v = 2500Ah battery bank,
  • Ritar make a 2v 1500Ah battery for R4000 - you will need 48 of these for a 3000Ah bank
    • about R192k

That's about R402k, plus R48k for installation sundries and R50k for me that's about R500k - sounds like a bargain!

Note that this wouldn't be Off-Grid but Grid-Assisted (not grid-tie, you wont be feeding any power back anywhere) so that the Axperts can take power from the grid when needed. You will get probably 80% of your power requirement from the PV system with the grid helping out with the other 20% on them dark and dingy days.

If it was me I would want to save R10k a month on the utility bill to make capex worthwhile - I reckon you will save 2500kWh per month so your power cost must be R4/kWh or higher to give this system the green light - if not then just pay the utility bill.

Sounds like a blast, have fun:D

 

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Good morning.  Apologies I wa offline.

1 hour ago, Chris Hobson said:

Morning Clement

You must just confirm whether the equipment is single phase or three-phase. It makes no difference to @pilotfish's proposal (which I like) but will influence how you implement it.

Hi Chris morning.

Yes all the equipment are single phase. Let me study through @pilotfish' s proposal.

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9 hours ago, pilotfish said:

4.1kW x 24hr = 98.4kWh per day (ouch!), call it 100kWh so you will need about 20kWp array. So a real cheapo solution would be as follows;

  • 6x Axpert MKS 5k in parallel (for the panel capacity, not for the output power which will be way overkill),
    • about R60k
  • Each Axpert with 10x 315Wp panels = 3.15kWp x6 = 18.9kWp (not quite 20kWp but close enough),
    • about R150k
  • Assume 8hr solar day and 14hr solar night, so your battery bank must carry you for about 14hr's on average.
  • 4.1kW x 14h = 57.4kWh supplied by battery, if you use lead acid and limit it to 50% drain you will need 120kWh battery bank.
  • 120kWh / 48v = 2500Ah battery bank,
  • Ritar make a 2v 1500Ah battery for R4000 - you will need 48 of these for a 3000Ah bank
    • about R192k

That's about R402k, plus R48k for installation sundries and R50k for me that's about R500k - sounds like a bargain!

Note that this wouldn't be Off-Grid but Grid-Assisted (not grid-tie, you wont be feeding any power back anywhere) so that the Axperts can take power from the grid when needed. You will get probably 80% of your power requirement from the PV system with the grid helping out with the other 20% on them dark and dingy days.

If it was me I would want to save R10k a month on the utility bill to make capex worthwhile - I reckon you will save 2500kWh per month so your power cost must be R4/kWh or higher to give this system the green light - if not then just pay the utility bill.

Sounds like a blast, have fun:D

 

Thank alot for that feedback and I will try to put figure together and see th total cost for the system. I will study through and give it a thought . Client is likely to get some financing from a bank and needs a proposal.

Thank once again.

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3 hours ago, Chris Hobson said:

You must just confirm whether the equipment is single phase or three-phase.

At 4.1kW total load it wouldn't matter whether it was arranged 1phase or 3phase, because you will have 24kW available if 1phase or 8kW per phase if arranged 3 phase.

I would go ahead with 3 phase arrangement and install equipment as follows;

  • Red Phase - 1.1kW air blower
  • White Phase - 1.5kW water pump
  • Blue Phase - 0.75kW air blower + 0.75kW water pump

This way you will have nicely balanced phases, plenty capacity to accommodate starting currents, and you can still use a 3phase appliance in future should the need arise - but to do this your grid supply will need to be 3 phase. If not then arrange as 24kW 1phase system - no problem.

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I know the client wants to go completely off the grid, but I think you should do the math for a grid-tied system as well. Those generally cost way less and repay a lot faster.

One 5kva Fronius and a slightly oversized array. You could probably offset your daytime costs at under 100k ZAR (ie a fifth of the cost) and possibly still cut 30% off the bill. Thumbsuck. If the meter is an old style disk meter that can spin backward (evil evil... I know)...

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6 hours ago, Clement said:

Thank alot for that feedback and I will try to put figure together and see th total cost for the system. I will study through and give it a thought . Client is likely to get some financing from a bank and needs a proposal.

Thank once again.

Just a quick one .I just noted that the 5kva axpert parallel configuration x6 units recommends 1200Ah battery bank and you proposed 3000Ah which is attainable by means of using 1500Ah x2.is it ok to have two groups of 1500Ah considering the recommended is 1200Ah for 6 units parallel operation?

Thanks

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16 minutes ago, plonkster said:

I know the client wants to go completely off the grid, but I think you should do the math for a grid-tied system as well. Those generally cost way less and repay a lot faster.

One 5kva Fronius and a slightly oversized array. You could probably offset your daytime costs at under 100k ZAR (ie a fifth of the cost) and possibly still cut 30% off the bill. Thumbsuck. If the meter is an old style disk meter that can spin backward (evil evil... I know)...

Great idea.does the 5kva fronius have a battery backup provision? Grid tie will work perfectly when grid is  present but he is also trying to avoid the use of generator when grid is not present. 

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Note that the Axperts in parallel share 1 common battery bank.

The Axpert MKS 5K can charge at up to 80Amps, so 6 in parallel can charge at max 480amps which is over 15% of the 3000Ah bank rating - I would be happy with this scenario. I think the recommendation has to do with charging of some AGM which require a high initial current of 20% of rating, the OPS batteries suggested dont have this requirement so it is a blanket "cover our arse" recommendation in my opinion (but my opinions have been known to be way off on occasion).

Also you would set ICC software via your Victron BMV-702 to never discharge beyond 50%, so while you have a 3000Ah bank you would only ever require the charger to recharge 1500Ah.

 

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4 minutes ago, plonkster said:

My personal opinion is that If I'm spending 200k+ on batteries, I'm not using friggin Axperts.

 

3 minutes ago, plonkster said:

It's a pure GTI. No backup.

So when the grid goes down and the fancy Fronius shuts off and all the fish are flopping around gasping for oxygen, with eyes bulging and gills turning purple with moments to go before they die - then the client runs out and buys 100k diesel generator wishing like hell that Clement had sold him a solution with some backup:huh:

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Just now, pilotfish said:

fish are flopping around gasping for oxygen

Surely he has a solution in place for this already, or maybe fish doesn't die the moment the pump goes off? The goal of the project is to reduce costs if I understand correctly (though backup may be a handy side effect). In terms of bang for buck, when purely talking cost reduction, few things beats a GTI. I'm just saying he should run the numbers for that side as well, and it does depend on the assumption that either the fish won't die if the power is out for a bit... or he already has a 5kw+ generator around.

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1 minute ago, Clement said:

Great idea.does the 5kva fronius have a battery backup provision? Grid tie will work perfectly when grid is  present but he is also trying to avoid the use of generator when grid is not present. 

Or 

 

Just now, plonkster said:

It's a pure GTI. No backup.

Oh ok I get it.. meaning in this case I can use infini solar 10kva considering it can operate in grid tie with battery backup? I understand I can load it to about 15kw pv array. If I was to go by @pilotfish proposal of using 1500Ah 2V batteries (3000Ah) at 50% DOD I would get about 15hrs on battery backup  and given 8hrs of sunlight meaning somehow 10.9kw would charge the batteries. While 4.1kw goes to the load. I would save on 5kw pv cost from @pilotfish's proposal of using axpert x6 units.

Is that workable?

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13 minutes ago, pilotfish said:

 

So when the grid goes down and the fancy Fronius shuts off and all the fish are flopping around gasping for oxygen, with eyes bulging and gills turning purple with moments to go before they die - then the client runs out and buys 100k diesel generator wishing like hell that Clement had sold him a solution with some backup:huh:

That's my concern with a GTI. I guess Infinisolar would get me around alot better.just need to understand better.

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Just now, Clement said:

infini solar 10kva

I'd be okay with using an infini, yes.

It feels all wrong to me to put 6 Axperts in parallel (they are around 8k a pop, so that's almost 50k worth of inverter) when you can buy other inverters -- better inverters -- for the same price. You could put in two Goodwe hybrids, a large infini, or even a 5kva Multi (admittedly that will cost more, external MPPTs) for not much more.

A 5kva Fronius is like 30k... I know it has no backup, but if the grid is dependable and line rental isn't too insane... ?

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5 minutes ago, plonkster said:

Surely he has a solution in place for this already, or maybe fish doesn't die the moment the pump goes off?

I'm sure he does, my reply was intended as light hearted. A Builders Warehouse gennie capable of the job will cost about R6k.

Note that my proposal was a kick-off point because no-one else has responded - I don't doubt that there is much better solutions available , although I don't think that Grid-tie is one of them if the project is in in RSA, because authorities go out of there way to make if uneconomical unless you are prepared to "wind the old clock back" which is a criminal offence.

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9 minutes ago, plonkster said:

Surely he has a solution in place for this already, or maybe fish doesn't die the moment the pump goes off? The goal of the project is to reduce costs if I understand correctly (though backup may be a handy side effect). In terms of bang for buck, when purely talking cost reduction, few things beats a GTI. I'm just saying he should run the numbers for that side as well, and it does depend on the assumption that either the fish won't die if the power is out for a bit... or he already has a 5kw+ generator around.

He's got a 7.5kva generator and ATS already.

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16 minutes ago, Clement said:

Yes am in Zambia

You will need to investigate the grid-tie conditions in your area before heading down this road.

In Joburg where I live you will get 42c for feed in, and charged Time Of Use rates for consumption. Based on the 8hr/14hr split, of your 14hr consumption period you would be charged 302c for 3hour, 125c for 3 hr, and 90c for 8 hr.

[302 x 3]+[125 x 3]+[90 x 8] = 2000/14 =143c average (we can do this because of the constant load, domestic setup is MUCH more complicated calculation).

The ratio of feed in to consumption charge is 143/42 = 3.4

In order to break even on your utility bill under these conditions you will need to produce the following; [4.1 x 8 = 33kWh] + [4.1 x 14 x 3.4 = 195kWh] = 227kWh per day as apposed to the 100kWh per day in the initial proposal.

  • Now you need 45kWp (R375k)
  • and 3x InfiniSolar 3p 10kW in parallel (R150k)
  • 25kWh battery to give you about 3hr backup (R60k)
  • 300m2 structure required for your 150 panels
  • Installation sundries thumb-suck (R60k assuming 300m2 structure mentioned above is already available)

That is a budget of R645k, or you could go with 1st proposal (using something other than Axpert of course:ph34r:) and invest the extra R200k to pay for your replacement batteries for the rest of time. 

 

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im curious here

I have one inverter 4kw which can run my house and my pool pump off solar during the day . what about have a single inverter ,say for argument sake a  four 3kw inverters  running  each of the four  items since they are all single phase and  again four battery banks  since they may be spread out over a large area. or maybe two 5 kw inverters running 2 items and two battery banks . they should be able to handle the start up currents  but maybe not start them up at exactly the same time . this also allows for  breakdowns  and if you lose an inverter you don't have to shut down every thing , so get an extra spare inverter and swop it if you do have a problem. to me this covers most bases

wouldn't this also make the battery banks easier to maintain / handle  as nobody really likes to parallel to much.?

 also I see  no lighting mentioned,  just saying

you could run off solar during the day and power  at night  and so still have savings like the grid tie so at the end of the day you are saving

just another quick thought  . the axpert V series has a self consumption mode  and a grid tie feature

cheers

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