"Looking for a PV and EV solution"

Coastalwatch

frozen_wastes wrote: »

I'm reading this post with interest, as my eventual plan will be to replace my Diesel with an EV (next 3 years or so, so my thought is that I want to generate as much juice as I have space for.

I've been measuring up on my roof and I'm able to get 28 LG NeON2 panels on my roof in a 4x4 configuration facing SSW and a 4x3 config facing ESE.

That's 9.24kWP (330W per panel)! That's about 10MWH annually, or about 37000miles in a Tesla Model 3. That's how I think of such numbers!

So this DNO restriction at 3.68kWP interests me. Is the restriction on the power **exported** through their meter, or the *generating capacity* of the system (i.e. The DNO doesn't care if it's consumed on site, or even if the generating capacity is not running at all - they only care if there's an electrical connection to their grid).

I know, there's no FIT metering with that solution, but FIT's will disappear by the time I get a PV array commissioned on my roof so that's eventually going to be a non issue.

But either way, I think the amount being charged to get DNO permission for connecting large PV arrays will be such that technical workarounds will end up being more cost effective.

Hi F W and welcome to the thread.

Afraid I'm not able to advise in any way other than what I've experienced in the process so far and certainly not from a technical background. However, with regard to DNO permission and it's apparent cost I can only advise that in my case the installation company have handled it entirely with no cost to ourselves. While in some cases it may be a problem due to the local infrastructure and cost maybe involved I found that several companies actively tried to dissuade me from having anything other than a 4kwp system due to the dreaded DNO or even local council in one instance. In fact, having previously agreed on a 26 panel array, when the installation guy arrived he felt he could get another four panels on if I wanted. So we did, once having checked with the office that the Inverter would accommodate them!

As for not going for the panels now while FIT is still available then, why not. You could have your cake and eat it providing the company you choose and your negotiating skills are up to it. Your roof seems almost ideal for the system you propose, although others are perhaps better placed to judge than me. Either way you've come to the right place, I'm sure others will join in to ease your path along the way. Good luck.

Martyn1981

frozen_wastes wrote: »

I'm reading this post with interest, as my eventual plan will be to replace my Diesel with an EV (next 3 years or so, so my thought is that I want to generate as much juice as I have space for.


I've been measuring up on my roof and I'm able to get 28 LG NeON2 panels on my roof in a 4x4 configuration facing SSW and a 4x3 config facing ESE.


That's 9.24kWP (330W per panel)! That's about 10MWH annually, or about 37000miles in a Tesla Model 3. That's how I think of such numbers!


So this DNO restriction at 3.68kWP interests me. Is the restriction on the power **exported** through their meter, or the *generating capacity* of the system (i.e. The DNO doesn't care if it's consumed on site, or even if the generating capacity is not running at all - they only care if there's an electrical connection to their grid).


I've got a few design ideas to get round this system. One is to have a single inverter between the DC and AC networks limited to 3.68kWP. Then I could have heavy consumers on the DC network, such as a battery or DC car charger.


I know, there's no FIT metering with that solution, but FIT's will disappear by the time I get a PV array commissioned on my roof so that's eventually going to be a non issue.


The other thought is a split system - 3.68kwP grid connect on one array, and an Islanded system on the other. The thought in my mind is that it should be possible to have a three way automatic switch that swaps your house consumer unit between the grid connection and your islanded system. Technically you wouldn't be connected to the grid - the switch can be thrown at the 0 Volt crossover as soon as it detects that their's enough juice being generated by the Islanded array to supply the load.


But either way, I think the amount being charged to get DNO permission for connecting large PV arrays will be such that technical workarounds will end up being more cost effective.

Good questions, can I throw out claims without links as I need to run in a bit (I've got a boarded guide dog with bad eyes, and an angry feral cat at a rescue center I have to look after), but will chart later properly.

So, straight off, you can ask the DNO for more export permission, the 3.68kW is the standing rule, after that applications need to be made, you might get more, I have 5.9kW permission.

Next, would three phase be viable? It'll cost a lot for the upgrade but would give you 3x3.68kW.

You are right to consider export v's generation. The DNO does not care how much PV you have, nor how much generation you get, they care about what you send out onto the local network.

So do some research, there are commercial systems (try EMMA GVS) for background reading, this limits export, not generation, so thereby takes account of any on-site consumption before getting the inverter(s) to cap. I'm not sure if there are any DNO approved domestic systems, but worth a look.

I do know that DC batt systems are available, these will send any unwanted generation to the batts for later use, rather than converting to AC there and then, so let's say the batts can be charged at 2kW, then (ignoring AC/DC conversions, losses etc) let's just say you could generate 5.68kW, as only 3.68kW AC would be produced.

You won't lose FiTs on a DC system as it will be clocked up by the FiT meter when it is discharged through the inverter for use, however the battery efficiency losses will lose FiTs, but that's not too bad.

You could go for multi systems but you may need to have different leccy systems in the house with dedicated uses to avoid any chance of DNO issues.

No idea if an EV can be DC charged at home, I know that DC fast charging is provided at rapid sites, no idea if home systems exist, but would be interested to know.

You say 9.24kWp and SSW + ESE, is that correct? Just checking as usually there's a 180d difference, not 90d, so presumably a hip roof or similar?

So, let's assume they generate at similar times as they are not 180d apart, so total guess let's knock 10% off for max output, then my usual guess at a hot panel sustained max of 80%, gives us a peak of around 70% of kWp = 6.5kW. that's way too high to ignore capping, so yep you do need to think this through carefully, but can I annoyingly state that's it's not a bad problem to have, I'd love to have that much too much generation. So the problem is the solution, so to speak. Should be an interesting discussion. Back later.

frozen_wastes

Martyn1981 wrote: »

So, straight off, you can ask the DNO for more export permission, the 3.68kW is the standing rule, after that applications need to be made, you might get more, I have 5.9kW permission.

Thanks for your feedback. I'll try asking and see what they say. There's one person on my street already with a 14 panel array, so that may make it more difficult to get permission. My expectation was that any kind of authority wanted money first to a question like that before giving an answer back.

Martyn1981 wrote: »

So do some research, there are commercial systems (try EMMA GVS) for background reading, this limits export, not generation, so thereby takes account of any on-site consumption before getting the inverter(s) to cap. I'm not sure if there are any DNO approved domestic systems, but worth a look.

I was having a look at the solar edge inverters. They have export limitation as seen on Page 35 of the brochure:
https://www.solaredge.com/sites/default/files/residential_catalogue_eng.pdf


They also have DC batteries coupled to the solar DC network (Page 25), which was the kind of topology I was looking for.

Martyn1981 wrote: »

Next, would three phase be viable? It'll cost a lot for the upgrade but would give you 3x3.68kW.

I suspect that three phase would mean that two extra transformers would have to be installed at the nearest 11KV line, and two new 240V electrical cables would have to be buried underground from that station to my house. I can't imagine that being cheap at all. I think power management solutions in my house is far more economic.


But that said, Tesla do offer 15KW three phase car chargers. I've often thought that 10KW chargers would be needed for overnight charging once 100kwH batteries become the norm in EV's.


But I was thinking that a DC car charger would naturally be a good candidate for also helping to limit the export power through the invertor. You also reduce losses by avoiding conversion from DC --> AC --> DC. But I've not seen a domestic solution that offer's DC car charging.

Martyn1981 wrote: »

You say 9.24kWp and SSW + ESE, is that correct? Just checking as usually there's a 180d difference, not 90d, so presumably a hip roof or similar?

I live in a T shaped bungalow with two roof ridges perpendicular to each other. I live in NE scotland, and one of my other villagers has got a 12x Panel array using the LG Neon 2 panels (6 facing E, and 6 facing W) He's generating 3.4MWH annually, so I reckon that 8-10MWH would be doable for me.


One achilles heal that doesn't seem to be solved yet is grid blackout. It's not a major problem where I live, but all the solar inverters have anti-islanding systems to shutdown your generation. Very annoying when it happens. When I go back to page 25 of that brochure I linked above, my immediate thought is that the meter on the main grid incomer could also bedeveloped into an automatic isolator, thus allowing your property to work off-grid, and protecting the grid from your power source.


A lot of people in Florida weren't happy when hurricane Irma came through and knocked out their domestic solar systems. So I'm hoping the manufacturers wake up to that problem and develop a solution for that situation. I'm aware that Enphase has a micro inverter that keeps generating in a blackout, so that sounds promising.

Martyn1981

frozen_wastes wrote: »

I suspect that three phase would mean that two extra transformers would have to be installed at the nearest 11KV line, and two new 240V electrical cables would have to be buried underground from that station to my house. I can't imagine that being cheap at all. I think power management solutions in my house is far more economic.

Hiya, still running around, and have MSE friends coming over later (turns out not everyone on T'internet is an axe murderer in disquise), but everything you've posted makes sense, certainly interesting to me, as I know of it, but not necessarily about it all. I'm more of an interested (nosey) bystander.

Your DNO might, just might be willing to have a friendly informal chat with you. They can only OK an application from an appropriately qualified sparkie, but they should be able to tell you if it's gonna be a no. If it's not a definite no, then that would then suggest a possible yes IYSWIM.

Regarding 3phase, I'm way out of my depth here, but your street should have 3 phase, with every 3rd house on one phase, 1/3rd on another, and so on. I've no idea if that changes anything, and TBH I suspect the ideas a no go anyway due to cost, but perhaps something worth mentioning if you are having a nice chat with the DNO.

Bye for now.

EricMears

frozen_wastes wrote: »

But I was thinking that a DC car charger would naturally be a good candidate for also helping to limit the export power through the invertor. You also reduce losses by avoiding conversion from DC --> AC --> DC. But I've not seen a domestic solution that offer's DC car charging.

Main problem with that is of course that generation (& hence FIT payments) is based on readings of an AC generation meter.

FWIW, I have both PV and a BEV but very seldom bother to charge the car with solar power. I can't reduce the car's charging rate below 10A and very seldom have that much 'free' electricity. Hence I invariably use E7 to charge the car and use SP to run washing machine, dishwasher etc.

Ectophile

My Solax inverter has an islanded mode for power cuts. It's manually operated. If the power goes out, I have to crawl into the meter cupboard to operate a switch. This disconnects the main house consumer unit from the grid, and connects it directly to the inverter. Once I do that, I'm running off solar and/or battery.

Rather oddly, when the power comes back on, it automatically turns off islanded mode, blacking out the house again until I set the switch back to its normal position. I could probably disable that by flipping the breaker in the small consumer unit that feeds the inverter, so it doesn't know the mains is back on until I want it to.

So far, I have never needed islanded mode.

mickdann

Hello Dave, your device sounds interesting, would you be able to send me details too please?

Dave_Fowler

mickdann wrote: »

Hello Dave, your device sounds interesting, would you be able to send me details too please?

PM sent


Dave F

Coastalwatch

So, having had a PV array installed late April and enjoyed nearly three months of abundant generation I became rather frustrated that 90% of it was going to the grid. Having trawled various websites and publications for an as new 40kWh Leaf without success I found a Nissan Dealership offering a very good deal on a brand new N-Connector. Coincidentally a few days later another dealer phoned offering a second hand Zero, Special edition, with 2k on the clock for approx £1k less! Having already committed to the former we were saved from the problem of wrestling with which to choose!

It was delivered yesterday and to date we're delighted with it, early days as yet I know. A Zappi is on order although the granny cable connected via a three pin plug topped the battery up with approx 8kWh of Solar power over a sunny four hour period yesterday.
A heartfelt thanks to you all for the advice so freely given(and mostly adherred too) without which I doubt we should have got this far.
Just home storage, V2H and ASHP to sort.

Patience, patience I hear you say.:beer::A

Coastalwatch

The Zappi was installed today and while I've still to understand much of it's workings I've been able to set a security code, so that it is unlikely to be used in our absence and also set the Eco + setting to use 100% green(solar) energy only. Guess we'll learn and use other features as time and necessity arise!
Interesting that the lcd shows solar output in real time whether charging or not!