Newbie Advice Sought

[kla456]

Hello Forum, I joined this morning.
I would appreciate some advice.

What I have:
Passiv House refurbishment (2014)
Small EV with 16kW battery (2014)
7.4kW PV with 2x Immersuns diverting to 2x hot water cylinders (2016)
8 kW heat pump running at 30 degrees (2019) - gas disconnected
Wife with cleaning fettish (banks of washers, dryers, a fleet of floor cleaners)
Total electricity usage 16,000 kWh, generating 6,500 kWh, minimal export
Octopus GO with 5p rate (just this week)
Very small share Ripple - missed the recent deadline to increase

What I want:
Additional EV with 78kW battery towards end 2021 replacing diesel car doing 25k miles.
Get to 2050 standard of nett zero, but DNO is limiting me to 4kW PV expansion and 7.4kW export limit (or switch to three phase)
I am interested to join a group to replicate Ripple (asked Ripple if interested but they dont answer)
I am focusing on more energy instead of managing my usage because I expect price of electricity to increase and management tools to get better.

Looking forward to your advice.
Thanks in advance.

[Joeboy]

Welcome, ripple will be announcing WT2 soon, pre Autumn I think.

You can if you wish install batteries up to your financial limit being charged from your existing array up to your PV DNO max allowed. All good, then there is potential to add further PV which will splice in as a T Piece running from the new array to batteries as a fused spur as dc to dc connection avoiding your existing grid linked inverter and DNO limits as you are not exporting ftom the battery stack and if you are it's within DNO limits of grid tied inverter. Just harvesting the solar and storing it. Export limit is unaffected.

[Stinsy]

Welcome. Think you’ll find yourself very much at home here from the description of your past projects!

The DNO export limit is annoying. However it limits your inverter capacity not the size of your solar array. There are two ways around this:

1) You oversize the array compared to the inverter. It is typical to have a 4kW array and a 3.6kW inverter (but the same logic applies to any size). This means you generate more power at the beginning and end of the day and in overcast conditions, but lose out on anything over 3.6kW in the middle of when it is sunny. Solar panels are cheap!

2) You buy some batteries. You can have as big an array as you like and the DNO has no say so long as you feed the power into batteries. The DNO limit would apply to the power coming out of the batteries. In fact your current setup would benefit greatly from batteries even without additional solar, not only could you use the power generated in the daytime to power your house overnight, but you could also charge the batteries from the 5p rate in winter to power your house during the more expensive hours.

I’m in a similar position to you. My smartmeter is installed on Thursday this week (after nearly 2 years of waiting) and I intend to use the Go tariff. I have much less space than you, so much smaller array and only a small opportunity to expand it. I also have a 10kWh PHEV, but have ordered a 77kWh EV (due for delivery in December (hopefully)). However I have 3x my installed kWp of solar in kWh of batteries.

I’d say: go for option 2.

[nowty]

Hello Forum, I joined this morning.
I would appreciate some advice.

What I have:
Passiv House refurbishment (2014)
Small EV with 16kW battery (2014)
7.4kW PV with 2x Immersuns diverting to 2x hot water cylinders (2016)
8 kW heat pump running at 30 degrees (2019) - gas disconnected
Wife with cleaning fettish (banks of washers, dryers, a fleet of floor cleaners)
Total electricity usage 16,000 kWh, generating 6,500 kWh, minimal export
Octopus GO with 5p rate (just this week)
Very small share Ripple - missed the recent deadline to increase

What I want:
Additional EV with 78kW battery towards end 2021 replacing diesel car doing 25k miles.
Get to 2050 standard of nett zero, but DNO is limiting me to 4kW PV expansion and 7.4kW export limit (or switch to three phase)
I am interested to join a group to replicate Ripple (asked Ripple if interested but they dont answer)
I am focusing on more energy instead of managing my usage because I expect price of electricity to increase and management tools to get better.

Looking forward to your advice.
Thanks in advance.

My goodness are we from a parallel universe ?

What I have
Haven't quite got the Passiv House, but working towards it.
Have a small EV 30kWh battery.
Have 12kW of PV with 2 x immersuns, export limited to 3.6kW.
Heatpump is actually badged at 8kW but measured at closer to 6kW. Still have the gas I'm afraid but massively reduced it.
Got the SWMBO with the cleaning fetish, washing machine on 24/7, insists on 50 degree washes and steam irons everything.
Total electric usage 15,000 kWh, generating 10,500 kWh, minimal export apart from July and Aug.
Octopus Go Faster with 5.5p rate for 5 hours (20.30 to 01.30), I'm on a special trial and my peak price import is only about 50 kWh a year.
3kW of Ripple turbine. - YOU DEFINATELY WANT MORE OF THE NEXT ONE
Big 50kWh home Battery. - YOU DEFINATELY NEED ONE OF THESE (well maybe not quite as large)

What I want
A long range Tesla Model 3 to replace the dirty diesel. (waiting till I can access my pension pot for that).
I am expecting electricity price increases, because of, Nukes decreasing and new ones cost a bomb, commodity price increases, price needs to stay high for returns on further renewables. Also believe gas will be loaded up with carbon taxes which will feed through to leccy generation price.

------------------------------------------------------------------------

Not much to add to the other comments,

12kW of PV inverter power (along with my 6kW battery inverter) is about as much as my export limiting system (SMA Sunny Manager) can cope with on a single phase. Don't worry too much about the export limitation, you don't lose too much and the times of year you lose it you generally have more than enough, especially if you install a battery system to soak up all the excess leccy.

DC connection to batteries via solar PV and charge controllers is another way round the DNO limitations.

I don't understand your comment, "I am interested to join a group to replicate Ripple", could you elaborate ?

[kla456]

Hello Forum,
Thank you for your replies. I am replying to you collectively.

I am pleased to be in contact with nowty again - he advised me to repair a burnt-out Immersun in another forum. I also saw a guarded reference to Ripple in one of his posts which led me there.

The main idea is how to get around DNO restrictions - this is new to me and could be very useful. Is it necessary that batteries are installed to use this workaround? Does the DNO restriction apply to the inverter and not to the array? Will the inverter limit the export to the DNO restriction without problems? What happens to any over-generation that is surplus to battery capacity? Is it somehow spilled on-site? What are charge controllers (nowty)?

Another idea is to size the array for the back season because PV is relatively cheap. I like this, but is it necessarily coupled with battery storage?

I am a bit slow to introduce batteries. I just think they are an expensive energy management tool. I prefer to buy more generation at this stage, while better energy management tools are coming available. For example, Octopus GO (with one email) introduced a major energy management efficiency. KIA EV6 (77 kW battery) will come with a back-charging capability. It might only be 3-pin socket initially (not sure) but you can see the possibilities. I do appreciate that batteries bring independence from the grid and that Octopus can (with another email) withdraw GO at any time

I believe that Ripple will be the next big thing. Some life experiences have taught me to try to be the jockey or the horse, not the punter in the stands. I am interested to participate in a new start-up for this concept and I expect more innovation will come with this concept.

Please correct me where I may have misunderstood your replies.

[nowty]

Your hardly a newbie with your set up apart from the batteries.

So lets begin with your system, you appear to have 7.4kW of PV, but what size and model of inverter(s) do you have ?

Do you currently have any sort of export limitation now ?

Do you currently have approval for 7.4kW export ?

Do you currently get FITs and therefore a generation meter ?


The DNO has no authority to tell you how much PV panels you can have. The DNO does however, care about how much inverter power is connected to the grid irrespective of how many panels you have.

All new installations need to be in line with G98 (if under 3.68kW and used to be G83), but in your case G99 (similar to the old G59) and export limitation in line with G100 (thats new).

It is possible to install a second system and replace the existing inverters with something which will allow export limitation. That's what I did, I had a FIT grid tied system, a second FIT offgrid system and I added a third non FIT grid tied system in the re-design. I used SMA inverters and a Sunny Home Manager 2.0 which allows up to 3 PV inverters and one Sunny Island battery inverter and includes G100 compliant export limitation.

The alternative is to leave the current install as is, and install an AC coupled battery inverter (which is G100 complaint), like a Lux, Sofar, Goodwe, etc. Most folk use them with a stack of modular Pylontech batteries. The battery inverter acts like an Immersun but takes precedence and dumps excess solar power to the battery stack or discharges from the battery stack to prevent imports from the grid. You can then also add another solar array via a DC charge controller which converts the DC from the second PV array and acts as a DC battery charger to the battery stack. You just T it in (as Joeboy said). There is no overspill of energy as the charge controller just throttles back on the power from the PV if the battery is full. It messes up the stats on the battery inverter but apart from that it usually works.

I do it from Sept to March for that little bit EXTRA with 4 temporary panels on my decking area.

Joeboy does it all year round.

It can be a bit of a balancing act as you need to dump power into things like an EV, Hot water tank, or storage heaters to keep the batteries from being full so the second array keeps the power flowing via the charge controller. I use the boost function on the Immersuns to dump power into things.

[Mr Gus]

Nowty & co.

I for one think the info in this thread ought be put elsewhere as a clearly titled info piece on how to get round the DNO with solar (or similar) & easily found as a bookmark

It is informative & needs more access to help resolve common issues.

[Stinsy]

Is it necessary that batteries are installed to use this workaround?

Batteries are not necessary. However the fickle nature of solar makes them a very good idea. Imagine the sun is out and you’re generating decent power, most-of-which is going to the grid. Then just as your washing machine heating element kicks in, a black cloud comes over. A small battery pack (or “stack”) would even out these fluctuations and mismatches in timing. A bigger pack would get you through the night with no grid usage at all, and maximise the benefit of the cheap rate.

Does the DNO restriction apply to the inverter and not to the array?

Correct. The DNO is concerned about grid stability. Imagine a small village with a very old, undersized, grid connection. If every house suddenly added 10kWp of solar then the local transformer / supply cabling could become overloaded on the sunniest days. They are therefore only concerned about your maximum inverter capacity. Power capacity in excess of inverter capacity or that is fed into batteries is none of their concern.

Most talk is about 3.6kW (per phase) because that is the limit at which you don’t need permission from the DNO (under G83 you need to inform the DNO but they have no ability to say no). Many people cannot be bothered with an application for larger inverter capacity (G59) or such permission has been declined.

Will the inverter limit the export to the DNO restriction without problems?

Yes! The only thing to be careful of is string voltage, you must not go over your inverter’s max string voltage. However you can avoid this by paralleling strings. By doing this you can go as big as you like.

What happens to any over-generation that is surplus to battery capacity? Is it somehow spilled on-site?

Nothing happens, the power isn’t generated. Imagine a disconnected solar panel left in the sun, it isn’t doing anything until a load is attached. The voltage is there, this used to be called “electrical potential” which think is a helpful concept, but seems to have fallen out of fashion. Think also about a normal domestic socket. It can deliver 13A/3kW when you connect a lamp it draws only a small amount of power the rest isn’t “wasted” you don’t need to use it all.

Do an internet search for “oversized array” for more info.

What are charge controllers (nowty)?

A “charge controller” sits between the solar panels and the battery pack. They are frequently built into all-in-one inverter/chargers, but they can also be separate devices.

Another idea is to size the array for the back season because PV is relatively cheap. I like this, but is it necessarily coupled with battery storage?

I’m not 100% sure what you’re getting at here. But if I understand correctly then yes, this is that an oversized array does. You typically get 25% of your kWp in bright/overcast conditions. So a 4kWp array connected to a 3.6kW inverter would be generating 1kW. Whereas an 8kWp array connected to the same inverter would be generating 2kW (in sunny conditions both arrays would be generating the inverter-limited 3.6kW).

I am a bit slow to introduce batteries. I just think they are an expensive energy management tool. I prefer to buy more generation at this stage, while better energy management tools are coming available. For example, Octopus GO (with one email) introduced a major energy management efficiency. KIA EV6 (77 kW battery) will come with a back-charging capability. It might only be 3-pin socket initially (not sure) but you can see the possibilities. I do appreciate that batteries bring independence from the grid and that Octopus can (with another email) withdraw GO at any time.

You definitely seem to be “battery hesitant”, and batteries are expensive there is no getting around that. However I’m surprised you’ve gotten this far without adding them. The Go tariff matches up with batteries perfectly meaning the batteries earn their keep even on days when there is precious little solar to be found.

A Zappi car charger is also something you should look into. It works like your solar diverters on your hot water tank putting power that would otherwise be “spilled” into the grid into your EV battery,

[Joeboy]

Is it necessary that batteries are installed to use this workaround?

Batteries are not necessary. However the fickle nature of solar makes them a very good idea. Imagine the sun is out and you’re generating decent power, most-of-which is going to the grid. Then just as your washing machine heating element kicks in, a black cloud comes over. A small battery pack (or “stack”) would even out these fluctuations and mismatches in timing. A bigger pack would get you through the night with no grid usage at all, and maximise the benefit of the cheap rate.

Does the DNO restriction apply to the inverter and not to the array?

Correct. The DNO is concerned about grid stability. Imagine a small village with a very old, undersized, grid connection. If every house suddenly added 10kWp of solar then the local transformer / supply cabling could become overloaded on the sunniest days. They are therefore only concerned about your maximum inverter capacity. Power capacity in excess of inverter capacity or that is fed into batteries is none of their concern.

Most talk is about 3.6kW (per phase) because that is the limit at which you don’t need permission from the DNO (under G83 you need to inform the DNO but they have no ability to say no). Many people cannot be bothered with an application for larger inverter capacity (G59) or such permission has been declined.

Will the inverter limit the export to the DNO restriction without problems?

Yes! The only thing to be careful of is string voltage, you must not go over your inverter’s max string voltage. However you can avoid this by paralleling strings. By doing this you can go as big as you like.

What happens to any over-generation that is surplus to battery capacity? Is it somehow spilled on-site?

Nothing happens, the power isn’t generated. Imagine a disconnected solar panel left in the sun, it isn’t doing anything until a load is attached. The voltage is there, this used to be called “electrical potential” which think is a helpful concept, but seems to have fallen out of fashion. Think also about a normal domestic socket. It can deliver 13A/3kW when you connect a lamp it draws only a small amount of power the rest isn’t “wasted” you don’t need to use it all.

Do an internet search for “oversized array” for more info.

What are charge controllers (nowty)?

A “charge controller” sits between the solar panels and the battery pack. They are frequently built into all-in-one inverter/chargers, but they can also be separate devices.

Another idea is to size the array for the back season because PV is relatively cheap. I like this, but is it necessarily coupled with battery storage?

I’m not 100% sure what you’re getting at here. But if I understand correctly then yes, this is that an oversized array does. You typically get 25% of your kWp in bright/overcast conditions. So a 4kWp array connected to a 3.6kW inverter would be generating 1kW. Whereas an 8kWp array connected to the same inverter would be generating 2kW (in sunny conditions both arrays would be generating the inverter-limited 3.6kW).

I am a bit slow to introduce batteries. I just think they are an expensive energy management tool. I prefer to buy more generation at this stage, while better energy management tools are coming available. For example, Octopus GO (with one email) introduced a major energy management efficiency. KIA EV6 (77 kW battery) will come with a back-charging capability. It might only be 3-pin socket initially (not sure) but you can see the possibilities. I do appreciate that batteries bring independence from the grid and that Octopus can (with another email) withdraw GO at any time.

You definitely seem to be “battery hesitant”, and batteries are expensive there is no getting around that. However I’m surprised you’ve gotten this far without adding them. The Go tariff matches up with batteries perfectly meaning the batteries earn their keep even on days when there is precious little solar to be found.

A Zappi car charger is also something you should look into. It works like your solar diverters on your hot water tank putting power that would otherwise be “spilled” into the grid into your EV battery,

A damn good explanation, the only thing I would add is that the saying 'make hay while the sun shines' is relevant. It's best to have somewhere to store the hay until you need it. I've ran my system 3 ways. Pv only, pv+batteries, pv+2nd array, pv+2ndarray+more batteries. Without a doubt it just kept getting better and better and I would not step back down from 4th version.

[nowty]

A quick note to clarify a couple of things Stinsy has said in his very good explanation.

Is it necessary that batteries are installed to use this workaround?

If using an oversized array, then batteries are not necessary, but then it comes down to whether you get FITs or not, as the solution could be quite complicated, thats why I have asked that question. You do not want to risk invalidating a FIT contract if you have one.

If using the workaround by using a DC charge controller to add extra PV, then yes you need batteries.


Does the DNO restriction apply to the inverter and not to the array?

G83 and G59 no longer allowable for new installations if you want to go down the official route. G83 was replaced with G98 and G59 was replaced by G99. Most second hand inverters don't have the new settings, so they are usually now installed under the radar or used to replace an existing failed unit.

I am a bit slow to introduce batteries

If you are going to get the maximum out of an oversized array then batteries are almost essential. Your talking about buying a bigger EV circa £40k+, so what's the deal with not spending £5k or so on a home battery ?

If you don't have a battery its use it or lose it, with a battery its you can store it and use later. Also charge it at cheap rate in Winter. If you buy more of Ripple when he next wind turbine project starts, that makes cheap rate charging even cheaper.