Starting from scratch, new design for grid-tied PV system, 8.5kW panels, 14.5kWh storage, 8kW inverter. G99 Form

[Smallholder]

The update to our previous electricity tariff has given me the push I needed, to crack on with getting solar on our house.

I've made off grid solar systems before, but never done anything grid tied, and never anything of this scale. So I'm not completely clueless, but also realise I have a lot to learn. Please go easy on me!

 

The system I am planning will sit on a flat roof. Panels sitting at about 15 degrees. Thinking I'll use 20x 425W panels. The reason for this being, it's the max I can fit on the roof.

Then I was thinking of using 3x PylonTech US5000 4.8kWh 48v batteries, and a Victron Quattro inverter (either 10,000VA or 15,000VA).

 

I realise I'll need to go the G99 route. I'd ideally like to do 99% of the work myself.

I'd like to export, so I'm keen to ensure my actions don't preclude this. I would like to create a system that can be configured to export at peak times.

I realise I may not be able to export at the full inverter load.

 

We currently have gas for DHW and heating, but interested in switching to electric. We have 2x EV's. Current we are consuming about 20kWh per day, with 50-60% of that off-peak (EV charging) 

 

So my questions are:

 

1 - Is it possible to install a system like this on your own. Not in terms of technical ability, but in terms of regulations etc.

 

2 - In term of the system spec, do you think I'm heading in the wrong direction with any part of the spec?

 

3 - Any advice in terms of the G99 form? I contacted 2 companies that advertised they they could help specifically with this part. 1 replied, and said that I should be fine to do the application myself.

 

Many thanks in advance!

[Smallholder]

[Marvin]

3 minutes ago, Smallholder said:

1 - Is it possible to install a system like this on your own. Not in terms of technical ability, but in terms of regulations etc.

As I understand it:

 

No and yes. If the work is done to the correct standard following planning and building regulations and signed of by an electrician and approved by the DNO then yes.

[Marvin]

9 minutes ago, Smallholder said:

2 - In term of the system spec, do you think I'm heading in the wrong direction with any part of the spec?

In my experience no and yes.

 

I would recommend trying to obtain as much PV as possible.

 

However, 8.5kW of panels will not produce 8.5kW at peak performance on a 15 degree roof in Somerset, and there is always a loss converting energy from DC to AC.

 

Have you used the PGIS Web site to understand what you would typically produce over each month? 

 

https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html

 

We produce about 1/4 of the output in the winter compared to the summer.

[Marvin]

3.

 

The application is not that bad. For ours there was a charge and we had to wait a few months for a reply.

[SteamyTea]

17 minutes ago, Smallholder said:

In term of the system spec, do you think I'm heading in the wrong direction with any part of the spec

Maybe.

Have you a time series of your current energy usage?

If you know how much energy you use, and when you use it, you can work out the best compromises.

 

As you have EVs, you already have 100+ of storage, pump it all into them, going to work out cheaper than the alternatives.

[Marvin]

We charge our EV 95% from the PV, however the car is at home most of the time during the day. 

 

Plus 1 on @SteamyTea comments.

The devil is in the detail.

[DougMLancs]

You’ve said you’re keen to export but if you go the DIY route then you’ll have to give it away for free since energy companies will want an MCS/Flexi-orb certified installation (MCS for Octopus for the best export rates). Sounds like you’ll be self-consuming most of your production anyway though.

[SteamyTea]

1 minute ago, Marvin said:

We charge our EV 95% from the PV, however the car is at home most of the time during the day.

If you did not have PV, I bet you would charge it at night on some short lived Octopus tariff.

 

A reasonable EV will use about 0.25 kWh/mile.

My car, running about, does about 0.8 kWh/mile.

Cheap night electricity is between 5 and 15p/kWh, let's call it 10p.  Diesel is around 16p/kWh.

So 2.5pmile against 13p/mile.

Going to be hard to beat that kind of price difference.

It does depend on how many mile you travel a year.  I do lots, others very little.

[Marvin]

25 minutes ago, Smallholder said:

I would like to create a system that can be configured to export at peak times.

This is the aim of every energy producer. Electricity is difficult (ok, easy but expensive) to store and usually requires converting into something else waiting and then converting back again.

 

 When you think of use, low and slow is easier to supply.

 

We produce too little in the winter and too much in the summer. We produced too much for some of  October last year and then started again in April this year.

[joth]

45 minutes ago, Smallholder said:

Then I was thinking of using 3x PylonTech US5000 4.8kWh 48v batteries, and a Victron Quattro inverter (either 10,000VA or 15,000VA).

 

I realise I'll need to go the G99 route. I'd ideally like to do 99% of the work myself.

I'd like to export, so I'm keen to ensure my actions don't preclude this. I would like to create a system that can be configured to export at peak times.

 

 

Victron Quattro is very powerful for a fully off grid or seamless grid failover, however it's complicated to use this for grid-tie operation as you also need to conform to the various standards around anti-islanding etc. Some info on the page below, but sounds like you need the MultiPlus rather than Quatro variant? 

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/system-design.html#UUID-7c21d64c-8be3-5162-abc8-027577d36a7a

 

Will you have a backup second AC source (generator?).  This seems to be where the quattro really comes into its own.

 

Controlling the inverter to only export (some amount) at peak times is highly inverter dependent, but of all manufacturers I'm sure with Victron there's some way to do it in local config (i.e. without involving a cloud portal being online, SolarEdge looking at you).

As others say, you won't get paid ££ for your efforts, due to the MCS cartel.

 

Anyway good luck keep us updated sounds a great project.

[Marvin]

Hi @SteamyTea

 

Slightly off topic but probably of interest to @Smallholder

 

Our car does about 5000 miles a year we're getting about 4.5 miles a kWh and travelling at an average of about 23miles an hour (so the car tells me)

So 5000 divided by 23 so that's about 217 hours a year being driven. We mostly drive during daylight so say 200 hours of daylight driving. Our typical amount of time away from home on each journey I have no data for, however thinking about it I would say an additional 1.5 hours of away time for 1.5 hour travel 

In summary the car is away from home about 400 hours a year (with a few exceptions) 

 

My point is that the car spends about 90% of daylight hours attached to the charger and this, along with low milage and short times away, means it works for us.

 

[SteamyTea]

1 minute ago, Marvin said:

Our car does about 5000 miles a year we're getting about 4.5 miles a kWh and travelling at an average of about 23miles an hour

I forgot you are on the IoW.

Max speed is what, 40 MPH.

[Marvin]

27 minutes ago, DougMLancs said:

You’ve said you’re keen to export but if you go the DIY route then you’ll have to give it away for free since energy companies will want an MCS/Flexi-orb certified installation (MCS for Octopus for the best export rates). Sounds like you’ll be self-consuming most of your production anyway though.

Hi @DougMLancs

 

Yes I forgot about the fact that we give away our excess...

@Smallholder please note.

 

However the whole system we have - 5.12kW - except for my labour, cost about 4k and assuming it all lasts for 7 years that's about £1.60 a day.

[Marvin]

3 minutes ago, SteamyTea said:

I forgot you are on the IoW.

Max speed is what, 40 MPH.

NO! 

Er... we have 970 metres of dual carriageway in Newport!

It's just we enjoy the scenery 

[Marvin]

Hi @SteamyTea   

 

https://www.cornwalllive.com/news/slowest-road-cornwall-average-speed-2601431

 

 

[SteamyTea]

22 minutes ago, Marvin said:

It's just we enjoy the scenery

We have people like that down here. The 7 month invasion is on now.

[SteamyTea]

22 minutes ago, Marvin said:

Hi @SteamyTea   

 

https://www.cornwalllive.com/news/slowest-road-cornwall-average-speed-2601431

 

 

Tragically, not 100 yards from where that picture was taken (in the news article) a school kid got runover and killed this year.

That same road was also the third most polluted road in the UK a few years back.

 

[ProDave]

To export and get paid for it, requires an MCS install.  Why do you WANT to export?

 

A PV system with batteries should be all for self use imho with export set to 0.  That is perfectly legal for an electrician to wire up and as long as you have notified the DNO.

 

The DNO rules seem prehistoric that they only look at the inverter power and assume that is what you WILL export and that is what they give permission for (or not)

 

Try a G99 application for what you want and see what they say.  Report back if they talk about charging you network upgrade costs, they should not be doing that any more but have yet to hear how people get on under the new rules.

[Smallholder]

3 hours ago, Marvin said:

As I understand it:

 

No and yes. If the work is done to the correct standard following planning and building regulations and signed of by an electrician and approved by the DNO then yes.

Great stuff, thanks! I'll take that as a win.
I head read elsewhere online that this was possible, but great to get a confirmation.

[Smallholder]

3 hours ago, Marvin said:

In my experience no and yes.

 

I would recommend trying to obtain as much PV as possible.

 

However, 8.5kW of panels will not produce 8.5kW at peak performance on a 15 degree roof in Somerset, and there is always a loss converting energy from DC to AC.

 

Have you used the PGIS Web site to understand what you would typically produce over each month? 

 

https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html

 

We produce about 1/4 of the output in the winter compared to the summer.

I am certainly familiar with the kind of output I can expect, having relied on a 2.5kW PV system on our smallholding for the last few years.
Yes I have modelled the output using this tool, so I have an idea of what to expect. It's a great tool!

As I said in the post, and showed with the 3D model, this is really the max number of panels I can fit on the roof space available. I could just about get more panels on another roof, but figured there must be a law of diminishing returns that says beyond a certain point, the cost of the larger array doesn't really make sense. Plus it will cost more!

[Smallholder]

3 hours ago, SteamyTea said:

Maybe.

Have you a time series of your current energy usage?

If you know how much energy you use, and when you use it, you can work out the best compromises.

 

As you have EVs, you already have 100+ of storage, pump it all into them, going to work out cheaper than the alternatives.

 

I have not yet gone this far with the consumption data, but I certainly could. Though our daily lifestyle is so unpredictable that I'm not sure I would get a lot from the data? I figured the battery storage almost covers a whole day of consumption, so that should set me on the right track...

 

I'm just wondering what changes I might make to the suggested system, if I did have more detailed data? I guess I could reduce the number of panels if it somehow pointed towards that... The inverter I guess might want to change, but I'm not sure how I'd reach this conclusion. The inverter(s) I'm looking at would be a good size to ensure I could export at a sensible rate, and if needs be, charge from the grid off-peak.

So I suppose the only thing I might be pointed towards, is changing the level of battery storage. Do you agree with this assessment?

[Smallholder]

3 hours ago, DougMLancs said:

You’ve said you’re keen to export but if you go the DIY route then you’ll have to give it away for free since energy companies will want an MCS/Flexi-orb certified installation (MCS for Octopus for the best export rates). Sounds like you’ll be self-consuming most of your production anyway though.

 

Is that definitely the case? That Octopus would demand MCS cert?
I had read online from people that had said they self installed, and were exporting to Octopus.

Some of the year we would definitely be self consuming most or all of the power generated, but in the summer there should be a decent excess.

Model shows over 1000kWh per month in summer, and only consuming 5-600kWh. 

[TonyT]

Get over to the Camelot forum, Nowty and Joeboy have the systems you are looking at and Nowty is very clued up on all the G99,G100 etc 

[Smallholder]

2 hours ago, joth said:

 

Victron Quattro is very powerful for a fully off grid or seamless grid failover, however it's complicated to use this for grid-tie operation as you also need to conform to the various standards around anti-islanding etc. Some info on the page below, but sounds like you need the MultiPlus rather than Quatro variant? 

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/system-design.html#UUID-7c21d64c-8be3-5162-abc8-027577d36a7a

 

Will you have a backup second AC source (generator?).  This seems to be where the quattro really comes into its own.

 

Controlling the inverter to only export (some amount) at peak times is highly inverter dependent, but of all manufacturers I'm sure with Victron there's some way to do it in local config (i.e. without involving a cloud portal being online, SolarEdge looking at you).

As others say, you won't get paid ££ for your efforts, due to the MCS cartel.

 

Anyway good luck keep us updated sounds a great project.

 

Great info, thanks very much!

 

I heard there is a bit of a faff in terms of which Victron inverters are approved for the G99 application, and from memory the bigger Quattro units are, but not sure about the larger Multiplus models. I'll have a look...

 

Yes it looks like the largest Multiplus that's ENA approved is 5000VA (4.4kW). So in summer I'd not be able to export anywhere near as much as I'd need to.