Reverse Energy Flow

[Les Macaulay]

I know nout about PV systems.
Is it possible that the system, when there is nil demand by the consumer, can feed energy back into the supply?
I believe there are two energy meters used.
Sorry if this basic thing has been asked before.

 

[Richard Burns]

PV is designed to export energy.
So long as you normal meter is compatible it will not rise whilst the PV is exporting energy.
You also have a generation meter that shows how much energy is generated by the PV and (unless you have an export meter as well) a certain amount is classed as exported the rest is assumed used int he home.
If the system is under the feed in tariff then you get paid an amount per unit generated and an additional small amount for the energy exported.

 

[Les Macaulay]

PV is designed to export energy.
So long as you normal meter is compatible it will not rise whilst the PV is exporting energy.
You also have a generation meter that shows how much energy is generated by the PV and (unless you have an export meter as well) a certain amount is classed as exported the rest is assumed used int he home.
If the system is under the feed in tariff then you get paid an amount per unit generated and an additional small amount for the energy exported.

Thanks for that, Richard. Is it true that some energy meters do reverse while the consumer load is low as the PV system actually feeds into the supply? I have a friend electrician who thinks this cannot happen.

 

[Earthstore]

Yes, some do, if they are tho old "dial" type and they have a picrure of a cog with a latch on it they do not go backwards, also some modern meters have anti tamper built in to them and the letters RED (reverse energy detected) can show, some of these will actually add the export to the import too.
If your meter does go backwards you should notify the DNO/Energy provider to have your meter changed because it is fraud if your meter is going backwards and you could be liable to prosecution.

 

[TedM]

Older meters can spin backwards during periods of net export and these usually get changed pretty quickly if PV is installed. There are also some modern meters that have an anti-tamper feature enabled that will clock up export as if it is import and anyone with one of these and PV needs it changed, or re-programmed, pronto. Most modern meters will simply ignore the export but may indicate 'rED' (reverse energy detected) while it is happening.

 

[Les Macaulay]

Older meters can spin backwards during periods of net export and these usually get changed pretty quickly if PV is installed. There are also some modern meters that have an anti-tamper feature enabled that will clock up export as if it is import and anyone with one of these and PV needs it changed, or re-programmed, pronto. Most modern meters will simply ignore the export but may indicate 'rED' (reverse energy detected) while it is happening.

Thanks again, Ted.
What would happen to the energy surplus, generated by say many consumers with arrays in the locality, during high sun shine while very few consumers are needing energy and are out at work (i.e. little or no demand). Does surplus energy find its way back via distribution transformers to a point in the system that does have load connected and can therefore consume the energy.
I do believe that a transformer will function in reverse. In other words how far back into the distribution system can the surplus energy flow?

 

[Les Macaulay]

Thanks for your input, Earthstore.

 

[7029 dave]

Thanks for that, Richard. Is it true that some energy meters do reverse while the consumer load is low as the PV system actually feeds into the supply? I have a friend electrician who thinks this cannot happen.

Yep, the old dial meters will go backwards they have no back stop facility.

 

[Worcester]

Hi Les,
Yes, hence the DNO G83/2 Stage 2 procedure for multiple connections - what's the reason behind your questions, we may be able to point you in the right direction for all your answers, - here is a good start:
ENA - Distributed Generation Overview

In practice you will find all your answers there

Have a good bank holiday's reading, when you've done that, if you still need clarification do come back and ask.

 

[rdo]

Hi. Having got the PV system installed recently I realised that I'm among those lucky with a meter spinning backwards. Nothing unusual apart from the fact that my property is a new built one (2014) and my neighbours have digital meters installed. What are your recent experiences with how suppliers are managing such issues?

 

[Tuck]

Are you saying that you have an older analog meter then (i.e. non digital)?
If so, refer to above posters, you need to let your electricity supplier know, and they will normally change it over to a modern digital meter pretty quickly (free of charge). Either way a quick call to your supplier/ FIT supplier should clarify, it may be that you have a meter that scrolls though several readings for example.

Also I am guessing that you have a larger system than 4kWp if you are net exporting at this time of year (or almost none of the house is in use, i.e. no fridge/freezer etc ticking over)?

 

[rdo]

It's a 4kW, but when there's a sunny weather it's generating around 1kW, hence much more than the fridge consumes, it's why I realised.
SP failed to set up my account as yet despite a number of calls. They're total rubbish so far, so I'd rather send them an email to have an evidence (I've registered FiT somewhere else).

 

[Tuck]

Sorry, I should have clarified. I meant the daily totals, yes at peak times it will still produce more, but over the day i would be surprised if you produce more than a few KWhrs a day average (at this time of year), and would likely be using a similar amount just from tick over, given that its nearing the shortest daylight hrs of the year and therefore you are likely to be using more lights for longer etc.

As to the FIT, when did you send the application form (MCS certificate, EPC, MPan etc.)?

Normally they reply pretty quickly letting you know you are in the system and that they have received your application. From that point (assuming they have your start date and starting generation meter reading) this is what they base future payments on, normally they then send a contract outlining the FIT scheme and there T&Cs for you to read and sign and return.

But basically as long as they have all your relevant info and you have keep a record of them receiving it, its backdated from there. If i recall correctly i think they have 4-6 weeks to set up your FIT from when they received your application, though don't quote me on that. if you haven't heard anything after a few weeks give your FIT provider a call, or drop an e-mail/ call to your PV installer and ask for some advice if that fails.

Hope this helps