Full off-grid system

Colin62

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Yeah, when I typed the 8kW it immediately looked a bit stupid, because I don't and probably never will have any single thing that draws that. But I might get close to that in total in my workshop at point in time*, it would be nice to know that I'm drawing off both inverters and not hammering one while the other is almost idle.

I was trying to get a feel for whether I would need to balance the load across the two inverters myself or if they would provide a single feed into the board and I can use it anywhere that I need it.


* At the moment, I manage to run all the equipment I need (lathe, dust extractor and compressor) off a single 15A breaker, mainly because most machinery draws well under the maximum rated power most of the time. The ony time the breaker has tripped was when one of the windings in the dust extractor motor burnt out.
 

itareanlnotani

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Good point, but ideally I'd like to come in under that - to be honest I got a hell of a surprise when I ran the numbers on the cable size and price.




One thing I'm not sure of is how the parallel mode works. Does each inverter have it's own panels and each supply a 5kW load or does one set of panels feed them both and they combine their outputs for a single 10kW load.

In other words do you have two 5kW feeds, or one 10kW feed into the house?


100k for batteries. (20kw odd)
50k for panels 9KW
50k for 8KW inverter + misc other bits

= 200K for a

9KW of panels
20KW storage
8.8KW inverter.

Would be more than adequate, unless you needed 3 phase.
 

Colin62

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Thanks.

No need for three phase - if I do, I’ll probably use a VFD for that.
 

Colin62

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Changing some of your motors to vfd driven could aslo be less strain on inverter .
Especially that extractor ?
That’s a good point. I suspect I need to replace the one I have now with something a little more robust at some point, and when I do, I think 3 phase and VFD will be the way to go.
 

Colin62

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Changing track slightly, I’m playing around with plans and floor layouts in my head at the moment and was wondering what sized room / cupboard I should allow for the inverter and batteries. I could just shove it in a corner of the garage, but give that I’m doing a greenfield project it makes a lot of sense to include a ‘power room’.

I’m also wondering if a generator can share a room with the inverter or if that’s best given It’s own spot.
 

Benedict A55h0le

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Remember to take into account the new taxes for solar systems in SA. Soon we will be paying more for the "grid availability levee" than for the actual elec we use.
 

signates

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Remember to take into account the new taxes for solar systems in SA. Soon we will be paying more for the "grid availability levee" than for the actual elec we use.
It's not directed specifically at solar though. Everyone will be paying this irrespective whether you have solar or not.
 

RonSwanson

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Changing track slightly, I’m playing around with plans and floor layouts in my head at the moment and was wondering what sized room / cupboard I should allow for the inverter and batteries. I could just shove it in a corner of the garage, but give that I’m doing a greenfield project it makes a lot of sense to include a ‘power room’.

I’m also wondering if a generator can share a room with the inverter or if that’s best given It’s own spot.
2mx2m should be minimum, 3x2 would be better. Ventilation (and possibly cooling) may also be needed.
For greenfields, I wouldn't place the genny in the same room unless you are assured of a good air supply, cooling and a pipe for exhaust, it generates heat and noise, and needs space for regular maintenance.
I would rather place it in its own silenced enclosure, adjacent to the power room (DC cables are expensive) and have a 80 - 110mm pipe going into an underground silencer, then out again.
 

Colin62

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Remember to take into account the new taxes for solar systems in SA. Soon we will be paying more for the "grid availability levee" than for the actual elec we use.
I speak under correction here but AFAIK it’s going to be a line fee for people with grid connections and low to no usage due to solar, and I’m hoping that I’ll escape that by not having a connection or line to pay a fee on.

Whatever happens, my payback is immediate as the off grid system will cost less than having a grid connection installed, so I don’t need ten or fifteen years to see a benefit.
 

Colin62

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2mx2m should be minimum, 3x2 would be better. Ventilation (and possibly cooling) may also be needed.
For greenfields, I wouldn't place the genny in the same room unless you are assured of a good air supply, cooling and a pipe for exhaust, it generates heat and noise, and needs space for regular maintenance.
I would rather place it in its own silenced enclosure, adjacent to the power room (DC cables are expensive) and have a 80 - 110mm pipe going into an underground silencer, then out again.
Thanks. 3x2 is definitely doable and there’s nothing worse than running out of space to work.

The genny may end up in the garage and only get connected when needed (which is hopefully never). The plan is to spec the system so that the genny is a backup in case of a fault or really, really bad weather.
 

wingnut771

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I speak under correction here but AFAIK it’s going to be a line fee for people with grid connections and low to no usage due to solar, and I’m hoping that I’ll escape that by not having a connection or line to pay a fee on.

Whatever happens, my payback is immediate as the off grid system will cost less than having a grid connection installed, so I don’t need ten or fifteen years to see a benefit.
How can they charge a "ready to install" fee and then still charge you couple of 100k to do the installation?
 

Benedict A55h0le

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I speak under correction here but AFAIK it’s going to be a line fee for people with grid connections and low to no usage due to solar, and I’m hoping that I’ll escape that by not having a connection or line to pay a fee on.

Whatever happens, my payback is immediate as the off grid system will cost less than having a grid connection installed, so I don’t need ten or fifteen years to see a benefit.
You still need to register that off-grid system and pay the new grid availability fixed levee. I hear what you say that the initial cost is lower. But a hybrid will allow you to claw back some R buy uploading surplus.
 

Colin62

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How can they charge a "ready to install" fee and then still charge you couple of 100k to do the installation?
The couple of 100k to go on-grid is mostly from a 200m cable run (needs to be a huge cable to keep voltage drop within spec). I don’t have an actual figure from the municipality for a connection, but assume it’ll be more like a couple of 10k for that.
 

Colin62

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You still need to register that off-grid system and pay the new grid availability fixed levee. I hear what you say that the initial cost is lower. But a hybrid will allow you to claw back some R buy uploading surplus.
I’ll seriously consider registering... Promise

A hybrid system means buying and laying a huge cable and I’ll not make that investment back before I die. I suppose when my pension runs out I could dig the cable out, sell the copper for cash and stave off having to eat cat food for a few months.
 
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