10Kw Pv System

[wozz]

Now ive got your attention calm down, its for a project so not real life as such.  

Ive got to specify the system and give reasons ect.  

I havnt designed a system outside of the classroom, and I last in the classroom a few years ago learning about this.  

Ive allowed for a 3phase circuit from the main board (MCCB), from memory does a PV circuit have tighter VD requirements than a standard circuit? 

Also which manuf would be good to start looking at, information being easy to get hold of being the main priority?

Also is there any software tools to help me?

Cheers for any input. 

 

[Sidewinder]

I can't remember the value, but yes VD (rise) is tighter on PV

 

[ProDave]

The problem with VD (rise) on a high power solar Pv can often be out of your control.

As well as taking into account VR (volt rise) in your own wiring, you need to know the loop impedance of the supply to the property.

There have been cases where Solar PV systems trip out on over voltage due to a high loop impedance at the supply. Add that to the fact in many places the supply is still in the order of 245V, there's sometimes not a lot of headroom to allow for volt rise.

If this is a classroom exercise then you need to specify a maximum supply voltage, and maximum supply loop impedance which will both need to be tested before installation to be sure it's going to work.

 

[wozz]

Supply is 400/230v TNCS 0.08Ze.  So i would assume a network impedance of <0.08.  Cant remember voltage rise being taught i may have been day dreaming.  

 

[wozz]

10kW total.  

Haha i was hunting around in files for the DTI guide when i got back to the desk with it i refreshed and you had posted a link for it! 

The 1% is what i vaguely remembered, I will aim for that.  

 

[wozz]

Used a Ib of 16/phase, got 1% easy and have a Zs of 0.21.  Placed the inverter centrally on roof (flat roof).  

Used the link to do a design, one problem i dont seem to be able to include the dimensions of the roof so unsure if the actual system would fit!

 

[wozz]

it logged me out and wouldnt let me back in, I chose sanyo HIT ones as i thought they were fairly high output to try to keep array as small as possible.

Im away for a couple of days with limited internet so will be back on this on wednesday.  

Yes i think i will spec each part and give data sheets including some sort of flat roof mounting, do some string calcs justify choices and thats about it.

 

[binky]

thought you didn't believe in PV Wozz :^O

 

[binky]

Sanyos have a higher voltage output than normal. This may cause a few problems with string calcs and balancing out inverter inputs, but then, that's all good experience for you Wozz. I think you would be better off using a panel like ET 250W, as this is the sort of unit most commercial systems use ie cheap and low spec. As far as the VD goes, it is tighter than normal due to long running periods at high power levels, but 10kWp is only a domestic shower - it's not a power station! As rule of thumb, I tend to think of a cable size I would use for a normal circuit, then go up a size, but that's more to minimise transmission losses up to Generation meter, than any need for a bigger cable half the time.

 

[steptoe]

the VD becomes an issue if your inverter needs to push out too much to overcome the incoming voltage at origin,

if that makes sense,

ie, SMA shut down at 263 volts, so if your inverter needs to push this out to allow for VD at origin then its not going to work.

 

[steptoe]

whats a volt between friends?

:|

 

[binky]

he's just picky :^O

actually here's a thought that paddler can answer whilst he's clearly bored and got nothing better to do - one thing I haven't tracked down yet (mostly cos I fit domestic singlephase systems) is what 3 phase inverters transmit down the neutral - I always size cable for full ampage in the neutral run, it's good for efficiency of sytem anyway, but if inverter is outputting a balanced 3 phase output, is that overkill.

 

[wozz]

I don't have the dimensions on me working away. They are the same drawing I sent you before, or google 2396 project plans. Should be home later.

 

[wozz]

The roof measures 30m x 13.2m . Would I have to be looking at the higher end output panels for this?

Any recommend on a mounting system of manuf to go after for info?

Obviously being a cautious designer (hahaha) I want to leave at least 1m around the perimeter for a walkway for maintenance of the panels / inverter, which will also be outside hopefully.  

I will mention handrails / man safe system although wont go into it as the drawings dont show access to the roof. Also i will mention bonding implications if LPS is installed.  I take it if I choose a transformer less SMA inverter I dont need to consider bonding of the array frame with a TNCS supply? 

 

[wozz]

Fantastic canoe will reply a bit later with relevant info. 

 

[binky]

with that size roof 10Kw would be lost in middle. Can get 50kW on there without too much trouble.

Lots of 250w panels around, just pick one. Rail system, I always use Schletter, you'll have to sign into site, but they have planning tool on there which also gives wind loadin scenarios etc etc. As for safety, you would want a scaffold hand rail and one access point. pretty standard stuff.