Specification for a Solar System

Reed_Richards

Dolor said:

I assume that you have the relevant G100 certification?

If by "relevant" you mean none (that I am aware of) then the answer is yes.  Otherwise you will have to explain what you mean in more detail.  My electrician fitted a form of isolator on the circuit so the lights go off momentarily then come back on if that is what you are worrying about.  It was done during the complete re-wiring of the house so my electrician may have self-certified, if that is permitted.   

Martyn1981

[Deleted User] said:

Reed_Richards said:

I have my battery on the DC side of the inverter.  I don't know if that helps with "islanding" but my inverter, made by Goodwe, will do this.  I have the lights, fridge freezer and router wired to the "island"; no point in trying to run the whole house as that would drain the battery too quickly. It works if I turn off the power at the mains; I am still waiting for the power cut that will really put it to the test.

I assume that you have the relevant G100 certification?

Q1. Do I assume you mean the house wiring, as the batts will be covered by the UK / DNO certification of the inverter, as it will restrict maximum export of PV + batts. Have I got that right?

Q2. So the real question regarding DNO compliance, is how does the inverter/kit break the connection of the house to the grid, when circuits are being supplied from the inverter? I'm reading RR's comment to suggest that these aren't separate circuits. Am I right in thinking that the PW2 Gateway 'physically' breaks the house's connection to the grid via (and don't laugh), a great big switch, allowing islanding on the same circuits, rather than requiring a separate dedicated circuit for lights, freezer etc? Hence the DNO G100 compliance?

Actually, that's made me remember something, doesn't the PW2 have a socket, so that you can plug in crucial devices, such as the freezer, again, being entirely separate to the grid tied circuits?

Sorry for all the questions, just love to learn.

QrizB

Apologies to @Grumpy_chap , this is getting off the topic of what a good PV system for his house looks like and should cost.

Reed_Richards said:

I have my battery on the DC side of the inverter.  I don't know if that helps with "islanding" but my inverter, made by Goodwe, will do this.  I have the lights, fridge freezer and router wired to the "island"; no point in trying to run the whole house as that would drain the battery too quickly. It works if I turn off the power at the mains; I am still waiting for the power cut that will really put it to the test.

It sounds to me as though @Reed_Richards has a hybrid inverter with a UPS output and his electrician has wired his supported circuits to that output, possibly via a contactor that switches them from the grid supply in the event of an outage (hence his mention of the lights going out, then coming back on).

Martyn1981 said:

Q2. So the real question regarding DNO compliance, is how does the inverter/kit break the connection of the house to the grid, when circuits are being supplied from the inverter? I'm reading RR's comment to suggest that these aren't separate circuits.

In RR's case, if I've guessed right then when the grid fails the UPS supported circuits are physically disconnected from the grid by the contactor.

Am I right in thinking that the PW2 Gateway 'physically' breaks the house's connection to the grid via (and don't laugh), a great big switch, allowing islanding on the same circuits

If you have a big enough battery and inverter (and I guess a PW2 is big enough), you can switch the whole house from grid to UPS-suppported in the event of grid failure.

(I've never quite worked out what happens to your "earth" in a typical UK TN-C-S installation if you switch from grid-connected to island. Normally your earth is derived from the incoming neutral, but if you're off-grid this seems a bit dodgy. Do you have to establish a local earth and switch to a TN-S system? [You can tell I'm not an electrical engineer!])

Reed_Richards

Further apologies to @Grumpy_chap , I hope this side-track is useful.  To the best of my knowledge the explanation provided by @QrizB is correct.  We had to dig a trench for a bigger capacity cable to the garage and my electrician took that opportunity to install a local earth. 

Grumpy_chap

Please don't apologise - I have gained some direct information related to my query and am learning more beyond that. 

The notes about G100 and technicalities with regard to "islanding" are very useful, especially as "islanding" is something I want to be able to do.

An earth spike is pretty easy to install.

I wonder whether Elon would offer a discount if I buy a PW2 plus a TM3 / TMY at the same time?

[Deleted User]

QrizB said:

Apologies to @Grumpy_chap , this is getting off the topic of what a good PV system for his house looks like and should cost.r

Reed_Richards said:

I have my battery on the DC side of the inverter.  I don't know if that helps with "islanding" but my inverter, made by Goodwe, will do this.  I have the lights, fridge freezer and router wired to the "island"; no point in trying to run the whole house as that would drain the battery too quickly. It works if I turn off the power at the mains; I am still waiting for the power cut that will really put it to the test.

It sounds to me as though @Reed_Richards has a hybrid inverter with a UPS output and his electrician has wired his supported circuits to that output, possibly via a contactor that switches them from the grid supply in the event of an outage (hence his mention of the lights going out, then coming back on).

Martyn1981 said:

Q2. So the real question regarding DNO compliance, is how does the inverter/kit break the connection of the house to the grid, when circuits are being supplied from the inverter? I'm reading RR's comment to suggest that these aren't separate circuits.

In RR's case, if I've guessed right then when the grid fails the UPS supported circuits are physically disconnected from the grid by the contactor.

Am I right in thinking that the PW2 Gateway 'physically' breaks the house's connection to the grid via (and don't laugh), a great big switch, allowing islanding on the same circuits

If you have a big enough battery and inverter (and I guess a PW2 is big enough), you can switch the whole house from grid to UPS-suppported in the event of grid failure.

(I've never quite worked out what happens to your "earth" in a typical UK TN-C-S installation if you switch from grid-connected to island. Normally your earth is derived from the incoming neutral, but if you're off-grid this seems a bit dodgy. Do you have to establish a local earth and switch to a TN-S system? [You can tell I'm not an electrical engineer!])

Reading through the Goodwe brochure some of their inverters are G100 compliant which is what I was asking in a clumsy way. In my case, all power to the home is routed through the PW2 Gateway as is all exported power. When Grid power fails, the Gateway isolates the home from the Grid but it still allows everything in the home to be powered from any PV Solar output and the PW2. I assume if PV Solar was outputting, say, 3 kWs then I could charge an EV at 7.2kWs  (with up to 5 kWs coming from the PW2) but I confess that I haven’t tried it. If the battery is at less than 100% SoC, and there is excess solar,  then the battery will charge. If the battery is full, then I wait to see what happens to the solar output on a sunny day. My 4 grid outages have all been at times when the PW2 wasn’t at 100% SoC and power to the home was a mix of solar and battery.

PW2 and Tesla EV owners get, I think, a £500 credit if they move to the Tesla Energy Plan.

Grumpy_chap

[Deleted User] said:

PW2 and Tesla EV owners get, I think, a £500 credit if they move to the Tesla Energy Plan.

Thanks - I never knew there was a Tesla energy plan - it looks good though.  Current incentive is £50 for just PW2, or £200 for PW2 plus a car.

Martyn1981

Grumpy_chap said:

Please don't apologise - I have gained some direct information related to my query and am learning more beyond that. 

The notes about G100 and technicalities with regard to "islanding" are very useful, especially as "islanding" is something I want to be able to do.

An earth spike is pretty easy to install.

I wonder whether Elon would offer a discount if I buy a PW2 plus a TM3 / TMY at the same time?

Thanks for that, it is interesting isn't it.

I've actually seen a PW2 'take over' twice. Once on an episode of Tesla Time News, where a tree fell in the garden of the father / son team as they were filming an episode, and there was little more than a flicker. They left it in to show their surprise at what had just happened outside, and the seamless transition to battery power.

The second was not quite as impressive, when Robert Llewelyn (Kryton) of Fully Charged had his PW2's and Gateway installed and tested, and I think it took about 10s for the batts to 'take over'. [It might have been that vid where I seem to recall the engineer explaining that the Gateway physically switches from the Grid, breaking the connection ..... or I've completely misunderstood it.]

No idea if the difference was just one of those things, or if UK kit, rules and regs, result in the difference, but either way, extremely impressive.

Just a shame the PW2 (and probably PW+) is so expensive, maybe it will finally get cheaper when (or if) Tesla battery production/supply overtakes demand. And in the US now, you can only get Tesla PV products if you also buy a PW, which may further complicate the issue and pricing.

Grumpy_chap

Grumpy_chap said:

Thanks for the additional information @QrizB and @[Deleted User].

Home is West London, so I have sent some enquiries to the people QrizB used (they drive past me from Kent to get to QrizB in Berkshire), Tesla (probably going to be expensive), two companies from YouGen plus one from an internet search.  With a 50% response rate, that will mean 2 or 3 budget proposals to compare with the Council "scheme".

Hopefully the proposals will give enough extra information to allow some kind of assessment to be done before the next steps.  Certainly more than the Council "scheme" offering to do "something for some money".

Fingers-crossed.

The first of the companies I sent the enquiry to called and made contact this morning - it was one of the companies identified from an internet search engine.  I thought that was quite good response time given that it is a Bank Holiday.  This particular company has said they cannot offer a quote because I have a rear-dormer loft conversion with flat roof and solar cannot be installed to a flat roof.

I assume that is just this company that cannot offer a flat-rood installation, not that solar is not viable at all with flat roof.  There must be many people seeking to install solar on a flat roof.

Reed_Richards

There might be an issue with planning permission for solar panels on a flat roof:

"All the following conditions must be observed:

• Equipment on a building should be sited, so far as is practicable, to minimise the effect on the external appearance of the building and the amenity of the area."

So on a flat roof the panels will have to be mounted on a frame which will significantly alter the external appearance of the building.  There is also the issue of what happens in strong winds; the mounting frame will need to be firmly attached to the roof.