Alternative solar supply available at point of use Domestic kitchen

 Anne Otis 

Research how grid tied systems work and how manufacture's have designed equipment to ensure that PV generation can be fully utilised, as a grid tied system will be far more practical and efficient.

Take for example the settings on this electric vehicle charger when it is controlled by a bidirectional current clamp on the meter tails.

1. Fast - Charger will work at full capacity
2. ECO - 6A will be provided from the grid and any excess solar power will be sent to the charger
3. ECO+ - Charger will only use excess solar (requires 6A excess to start the charge)

Option 1 will ensure that the vehicle is fully charged at a specific time, utter regardless of the time of day or the weather, it will use all the available PV generation and only draw what is required from the grid over the level of the available PV supply, so nothing may be drawn from the grid on a sunny day when there is little other usage around your home, depending on how the charging is regulated.

Option 2 will ensure the car does fully charge, but you cannot predict when it will be fully charged, because the total charge time is dependent upon the PV generation. 6 amps is the minimum charge rate for an EV, they will not charge below that, it will take whatever is available from the PV, so if 6 amps is available from the PV that is where it will get it from it will not take it from the grid, but will then ramp the charge up to make use of any additional PV generation, which might only be a couple of amps or may be more.

Option 3 will never take anything from the grid, but there is no guarantee the EV will charge at all on some days particularly if you are using other loads, there is inclement weather or it is dark.

The design of the EVSE is practical and allows for the best use of electricity from PV without separating the system into grid and off-grid.

support.projectev.co.uk/.../4411132985747-How-to-use-Solar-mode-on-your-Project-EV-Car-Charger

Sparkingchip said:

Research how grid tied systems work and how manufacture's have designed equipment to ensure that PV generation can be fully utilised, as a grid tied system will be far more practical and efficient.

Agreed!

hello  welcome to the show  Chris  Most useful to address specifics  PV generation can be fully utilised ? Sound a little corporate speak  ?

Lets give it a go  Questions 

Sun and moon: If moon  there is no PV ? Mostly you have nothing in  peak hours.?  Just grid  ? Unless you have storage battery ? 

Ok so you have to charge it ?  Is that PV by day ?  Or is it also grid charge in case :Is that Off peak electricity for that ? Can we believe that ? 

And how exactly do you size that battery capacity ? 

Grid tie So now you must have import export meter ? AND G9 xx anti islanding in case of power cut ?

Your installation  costs and kit are rising ? 

Excess solar energy If you have it would surely just waft around your home system hopefully being absorbed by some standby thing you have left on during the day ? 

Its chance? 

EV charging is irrelevant ? Just another  load on system .  Anyway I am in the city no point of having a car at all 

And now we must face how we see the future cost of electricity You cant really think its going to come down ? . Possible power poverty ? 

Submit with my scheme the consumer has control  System  KWhr  size can be much smaller Can always expand if wanted

If theres a power cut this system is still on line  No anti islanding required .

Makes full and clear use of PV availability  No hidden  small print. Summer and Winter.  Scale for winter summer is abundance   

Measure of real independence  ?  Its simple  :  sense ? 

All comments welcome as ever . Useful to be specific in criticism  

ciao 

Ms O 

hello  welcome to the show  Chris  Most useful to address specifics  PV generation can be fully utilised ? Sound a little corporate speak  ?

Lets give it a go  Questions 

Sun and moon: If moon  there is no PV ? Mostly you have nothing in  peak hours.?  Just grid  ? Unless you have storage battery ? 

Ok so you have to charge it ?  Is that PV by day ?  Or is it also grid charge in case :Is that Off peak electricity for that ? Can we believe that ? 

And how exactly do you size that battery capacity ? 

Grid tie So now you must have import export meter ? AND G9 xx anti islanding in case of power cut ?

Your installation  costs and kit are rising ? 

Excess solar energy If you have it would surely just waft around your home system hopefully being absorbed by some standby thing you have left on during the day ? 

Its chance? 

EV charging is irrelevant ? Just another  load on system .  Anyway I am in the city no point of having a car at all 

And now we must face how we see the future cost of electricity You cant really think its going to come down ? . Possible power poverty ? 

Submit with my scheme the consumer has control  System  KWhr  size can be much smaller Can always expand if wanted

If theres a power cut this system is still on line  No anti islanding required .

Makes full and clear use of PV availability  No hidden  small print. Summer and Winter.  Scale for winter summer is abundance   

Measure of real independence  ?  Its simple  :  sense ? 

All comments welcome as ever . Useful to be specific in criticism  

ciao 

Ms O 

Sun and moon: If moon  there is no PV ? Mostly you have nothing in  peak hours.?  Just grid  ? Unless you have storage battery ? 

Agreed.

Ok so you have to charge it ?  Is that PV by day ?  Or is it also grid charge in case :Is that Off peak electricity for that ? Can we believe that ? 

With a grid-connected system you have both options. Conventional fixed-hours off peak is indeed an option, perhaps more attractive are the likes of Octopus's Agile tariff, based on a smart meter, it follows the per-half-hour wholesale prices - which sometimes can be very cheap - occasionally negative unit prices (you're paid to consume electricity). All part of the brave-new-world smart grid idea to help balance demand with supply whatever times of day. 

And how exactly do you size that battery capacity ? 

Ah, that's one of those six million dollar questions. It's a classic case of diminishing returns - the first kWh will be well used and pay for itself quite quickly - the 10th kWh will be less well used, and the 100th kWh only used a few times a year, and you'd still have some risks of no power during a long power cut. About 1 days worth of consumption is roughly where most commercial products are. Per kWh batteries are disappointingly expensive - how deep are your pockets?

Grid tie So now you must have import export meter ? AND G9 xx anti islanding in case of power cut ?

You probably don't need an export meter unless you want someone to pay per unit for what you export (my grid tied PV system ran on an old spinning disc meter under the FIT for 10 years) - the only requirement is that the meter isn't allowed to run backwards (and for payments the FIT just assumed you exported 50% of generation). If you want power during a power cut, then yes you'd need an islanding relay and appropriate controls (but compared with everything else they're relatively simple).

Your installation  costs and kit are rising ? 

You pays your money and takes your choice of course. Grid tied is probably simpler to install (least disruption to the existing installation and no duplication of circuits, and side-steps problems with the protection of d.c. cables in odd situations), but yes, does require equipment with a little more sophistication.

Excess solar energy If you have it would surely just waft around your home system hopefully being absorbed by some standby thing you have left on during the day ? 

If electricity "wafts" about, you've got some very serious problems with you installation. With a grid-connected system any excess is exported (unless there's a power cut of course). With an off-grid system it's either diverted to something useful (an immersion heat is a common one) but that requires extra equipment, or the PV charge controller shuts down once the battery is full (so a complete loss of generation). You could leave some small appliance on the off-grid sockets permanently to reduce the changes of that happening perhaps - but you then reduce the energy available when you want it (and the small appliance stops working once the battery is flat). Many people go on holiday for a fortnight during the summer - which can be a surprisingly large percentage of the available solar power, without the significant loads being available.

   - Andy.

guys  Can we please focus on the question I came here for: 

forgive my maybe rant : You can regard this proposal as  possible productive new solar harvest solution or Heresy to the status quo:

The relative merits aside (for now)  

The question remains if I am to give this a real go :

Can this proposed system ( as attached ) pass muster to be in accord with " the regs"  Which I submit  to the collective wisdom of this forum for their kindly assessment 

In particular  regards to the earth system ( and the earth rod.  Given that all normal protections  are applied to the inverter /battery system. And so ignore 

In other words If I employ a local "sparks" to facilitate connections / test and sign off  Will there be any unforeseen surprises   Contradiction to the regs. Last minute full stop.

Be assured None to be held accountable for any views expressed . No quoting beyond this forum 

Obviously  foolish to invest and find at the end it is unsafe and no go .

Other observations to practical completion 
Testing of the earth rod Can a normal IET qualified person do this  Used to be the norm that domestic EV charge points had earth rod . Can I assume that whatever regulations applied to the installation and testing this would be therefore the same for the proposed earth rod here ?   presume I will not need the National Physical Laboratory to come and test it ? Can be done by most electricians  

TNS  Have heard : In general  this DNO supply cable is ageing and breaking up: Its earth connection back to source may no longer be secure So some new recommendation for owners to install this very earth rod for future reliability ? So that implies approval ?  Can I get the DNO to pay for it ? ( LOL) 

Look forward to all guidance any of you may kindly offer .  If its unsafe I will not do it. But do need to assess costs  practicalities to begin

Other : Th cabling distances are large because  I have made a personal decision  not to have a volatile lithium battery in the house  So its going in the garage at back of the garden  Underground Cabling would be SY semi armoured run in pvc pipe. 

Colder  Ms O 

PDF

Anne Otis said:

TNS  Have heard : In general  this DNO supply cable is ageing and breaking up: Its earth connection back to source may no longer be secure So some new recommendation for owners to install this very earth rod for future reliability ? So that implies approval ?

One option if you lose a TN-S earth is to convert to TT. However, the DNO is more likely to link N and E, which may be underground and not apparent at the intake. It follows that the safest approach is to assume TN-C-S.

TNS  Have heard : In general  this DNO supply cable is ageing and breaking up: Its earth connection back to source may no longer be secure So some new recommendation for owners to install this very earth rod for future reliability ? So that implies approval ? 

I think there's been a bit of Chinese whispers on that one. There is indeed a recommendation for an additional electrode these days on TN systems - but it's less to do with ageing TN-S cables, than with the ability of a simple fault on the 'new' TN-C-S (PME) system that can make the "Earth" connection hazardous live. (A problem that was previously mitigated by bonding to metallic water and gas pipes, but these have mostly been replaced by plastic). And no, no chance of getting the DNO to pay for it!

Can this proposed system ( as attached ) pass muster to be in accord with " the regs" 

In my option, yes it can be done. The details will have to be right (some of what you suggest might need adjustment), but nothing fundamental to object to I think. There are plenty of dual supply and off-grid system out there.

Underground Cabling would be SY semi armoured run in pvc pipe.

That's another detail that might need adjustment. SY generally isn't intended for underground use (as ordinary PVC sheaths can absorb water) and the steel braid isn't rated for use as a c.p.c. (and it doesn't comply with any recognised BS, EN or IEC standard).

As far as the local sparks is concerned, that rather depends on the individual. What you want isn't a "normal" domestic setup and may well be beyond the experience or even competence of some otherwise perfectly competent installers. Like anyone else no electrician knows everything about everything.  Someone who specializes in off-grid or UPS systems may feel more comfortable.

   - Andy.

SY cabling  It does need to have flexibility for radius bend  Ordinary armoured cable doesnt bend ?  ... OK Know you recommended something before  Can you point me to a supplier for your recommendation . I would run separate " containment pipes for dc / ac / and data cable  ( battery level)  anything wrong with solvent cement drain pipes  already laid some ?  Your comment pvc absorbs moisture I think now I understand old suppliers nervousness over underground pipes 

want to recommend a suitable " sparks/ consultant ? South London Wimbledon area  ( not the posh bit)  Ms O 

AJJewsbury said:

In my option, yes it can be done.

It's worth looking at Chapter 82 and the requirements for this type of system.

There are provisions in place already in British and International standards, and I'm a little concerned we are trying to "crowbar" a different kind of product in here that doesn't meet all of the necessary requirements for that kind of system.

Anne Otis said:

anything wrong with solvent cement drain pipes  already laid some ?

What size are they?

It's worth looking at Chapter 82 and the requirements for this type of system.

Humm, sort of. Chapter 82 seems more to be concerned with grid-connected systems - whereas what's being proposed here is to my mind more like a distinct system sitting alongside but independent of the grid supply - more like a UPS system (but with the battery charged from PV rather than the mains) - and 82 makes the point that UPS system aren't considered to be PEI (823) because it "is only to supply downstream critical loads and not capable of reverse feeding into the public network and/or current-using equipment in the upstream part of the electrical installation".

I think most of us here are of the opinion that a grid-connected system would be a more "modern" and "user-friendly" approach in a general domestic situation, but in this case it's not what the customer wants. The proposed system may have some definite advantages that the customer thinks valuable - a relatively simple system that more open to education and experimentation. It would be much more obvious how it's working (or not working); and side-steps some of the complexity (G98,G99 etc) needed for grid-connected systems. It might even work out a little cheaper as some of the complexities of having to deal with grid-fail etc aren't needed.

In some other situations, the proposed system would make perfect sense - I've seen something very similar on a narrow boat - providing 230V a.c. to a few appliances when moored somewhere that doesn't have a shore supply hookup (although that one was charged by a dynamo on the main engine, rather than PV). Some more modern units have an auto bypass so supply things from the shore supply if it's available, but I don't see any need to force people down that route if a simpler arrangement is satisfactory to them. I can imagine a caravan or camper van wanting a similar setup - and you really wouldn't want to go for a grid-tied situation there, when it can be plugged into a random installation that likely has no provision for accepting reverse feeding (let alone via a plug that would have its pins exposed when unplugged).

I'm a little concerned we are trying to "crowbar" a different kind of product in here

I do share some concerns there - there are certainly a lot of details that have to be got right. I have a decent suspicion that many inverters out there (especially of the smaller/cheaper variety), like many of the smaller petrol generators, are only intended for supplying a single appliance and won't be easily made suitable for supplying multiple appliances through a fixed installation (won't accept an N-PE link etc). I'm sure there is suitable equipment out there (for entirely off-grid homes etc) but suspect it's not cheap.  Likewise the arrangement for long and/or buried cables still needs some work. Lots of information is still missing, but I still have worries about impact/shock protection for any LV d.c. on an unearthed system (whether PV or battery) as well as v.d. to/from the battery if the thought was to have the battery in the outbuilding and the charger and/or inverter in the house. The choice of LV or ELV for the battery, probably helps one problem but hinders the other. Maybe no simple solutions, but that doesn't mean it can't be done.

   - Andy.

AJJewsbury said:

and side-steps some of the complexity (G98,G99 etc) needed for grid-connected systems. It might even work out a little cheaper as some of the complexities of having to deal with grid-fail etc aren't needed.

If you intend to operate the said inverter in parallel with the grid at any point, then G98/G99 must be complied with (according to ESQCR). If the inverter is set up as a simple grid-connected inverter, that may be OK ... but I'm not sure about the consequences for "backup" operation as per earlier posts.

"Side-stepping" something because it's difficult, or doesn't fit with the product as provided, is not really a good enough reason when we have specific legislation and standards (there's a reason things say what they do).

I still think it's worth looking at how the particular inverter is designed and arranged, to determine whether:

• It's possible to actually earth one of the live conductors of the "backup" (I know it's not in some designs); and
• the arrangement conforms to ESQCR for the operation in island mode.

One of the issues with answering questions in forums like this, is we aren't always told all the facts about a particular installation, so please forgive my apparent pedantic approach.

AJJewsbury said:

and 82 makes the point that UPS system aren't considered to be PEI (823) because it "is only to supply downstream critical loads and not capable of reverse feeding into the public network and/or current-using equipment in the upstream part of the electrical installation"

Well, if the inverter is a UPS then it will have a Declaration of Conformity to BS EN IEC 62040 series for that functionality ... otherwise, you would have to consider making a statement about its use in line with Regulation 511.2 ...

Having said all that, there may not be an issue with this particular product/application ... it may well conform to IEC 62040 and be suitable for use as a UPS ... I just don't know at this point.

worries about impact/shock protection for any LV d.c. on an unearthed system ..

Oh please expand  Expecting the solar panel dc will be in order of 100V or so :  48V battery. :   Dont think unusual ? So what normal  protections would be usual please ? 

Reckon I would run earth to solar mount "belt and braces".  Reckon bury a 3 core 10mm cable for ac side with the earth core as  link  inverter N/E to  DNO TNS MET ?  

FYI 

Plastic weld drain  pipe already partially run : 3 lots separated  50mm 30mm and aluminium under floor heating tube for  data cable  

I am going to need local expertise. If any suggestions 

Ms O 

PS reckon the energy future outook  is precarious at best . Reckon some off grid  mix could be wise . And simple maintenance.