Dont Laugh, A Couple Of Stupid Pv Questions

Hi all,

I have been doing some PV installs in Northern Ireland for a local outfit just over the border (I am in the South)  Anyway to my questions.  As the title says, please don't sit there smirking and shaking your head.... :facepalm:

1 If a PV works by putting out a voltage slightly higher than the supply, then the power goes 'out' if not used, thats fair enough.  Now if you had a number of houses close together could you have a situation where each inverter has to jack the voltage up to fight against the neighbours' inverters, if you follow what I mean.  Could this spiral up till all inverters shut down?

2 They tell me that your exported energy, if any, goes out on the street and gets sucked in by someone else.  Again that sounds fair enough.  However, I have fitted PV on farms where the only house on the transformer is the one on which I am working.  Now if the farm is using say 3kW but the inverter is making 5kW then the excess must flow in to the transformer and 'out' the HV side. 

Great forum by the way, it has been good watching it all develop...

1 yes, in theory

thats why you are supposed to inform DNO [is it stil NIE? ] if there are > x amount of installs in proximity

2 dunno, but I would suppose so, if you are generating more than you are using

3 I do hope you are declaring your earnings to HMRC and not tax dodging over the border in Eire,,,,  

steptoe said:

1 yes, in theory

thats why you are supposed to inform DNO [is it stil NIE? ] if there are > x amount of installs in proximity

2 dunno, but I would suppose so, if you are generating more than you are using

3 I do hope you are declaring your earnings to HMRC and not tax dodging over the border in Eire,,,,  

Click to expand...

Dont want to discuss number 3.... :innocent

BTW, you are obliged to declare your earnings in your country of residence...

It is indeed.

DNO [is it stil NIE? ]
Oops. Messed up the quote function!

Not sure how the inverters avoid the catastrophic raising of voltages on the grid, but it never seems to happen. DNO like PV outputs limited to 25% of network capability (think it's what their transformers can handle back-feeding), so any PV feed into grid I suppose is quite 'watered down'

DNOs hate PV.

On a bright day, they can artificially push an extra couple of volts onto the feeder radial - which may put the end-of-line client at / over the +10% limit - yet they can`t change the tappings, bacause, when the sun goes down, they could be close to ( or below) the -6% - theoretically, according to a commercial LV DNO fitter.....Mind, he also said they don`t like wind either - unless the wind & PV are tied into the 33K or above grids

the DNOs don't like anything much! :^O

True.

M107 may be able to answer this - which was said to me today......

If there is a house fire, the brigades won`t hose the roof down, if there`s PV on it........????

I sort of see the point - there is apparently a spray that can stop the DC output from the panels.........like a tarry substance.........anyone heard of this??

kme said:

True.

M107 may be able to answer this - which was said to me today......

If there is a house fire, the brigades won`t hose the roof down, if there`s PV on it........????

I sort of see the point - there is apparently a spray that can stop the DC output from the panels.........like a tarry substance.........anyone heard of this??

Click to expand...

we actually brought this up on an assessment once [when I was a QS] about fitting firemans switches and it was shot down by niceic as a waste of time,

******* dicks.

I actually don't see how it would really help paddler - FB shut off house electrics as a matter of course, which shuts down inverter, and shuts down system. But fire switch or not, the panels are still Live regardless. The only system that offers safe voltage DC is solaredge.

they still won't put a fire out anywhere near the roof. Simple answer is to spray with foam, but I don't know how many fire engines carry such stuff.

The ones that put the fire out in the unit next to mine the other night did!

binky said:

they still won't put a fire out anywhere near the roof. Simple answer is to spray with foam, but I don't know how many fire engines carry such stuff.

Click to expand...

I believe you will find they carry "foam concentrate"

Correct.

AFFF - "aqueous film forming foam".

its amazing stuff to use - they have a "branch" which goes into the high pressure pipe, and uses a venturi to mix the concentrate with the water. 

http://library.rbfrs.co.uk/TROVEPROGS/TroveAMUp.aspx?/IS=34979274/LI=Document/ID=40/OS=2/DI=12693/PA=295/HL=4/PS=295/RW=1600/RH=1200/CD=32/VD=DocLib/WV=7/ST=ad/AC=BU/FI=24/AM=Mozilla/HU=EmptyURL