Can I hope for some kind of indication the earth proposal is in fact SAFE 

It certainly look sensible in principle to me. At this distance I can't guarantee it's SAFE (there could be all sort of minor looking details that could get in the way that I can't see - such as arrangements for ADS) but I can see nothing in the earthing arrangements per se to object to so far.

... on second look at the diagram I notice it seems to be proposed to locate the battery storage system in the loft .... there have been some very recent discussions about that .. and a new standard published (PAS 63100 I think) which might have potentially moved the goal posts a bit on that score. (Who said cutting edge technology wasn't exciting (or even infuriating)?)

  - Andy.

thankyou AJ OK then I have confidence to proceed >  Be assured I am not holding anyone here for a verdict   Will leave that to my electrician sign off  when I finally contact : 

So many obstacles : Yes Volatile  lithium batteries Batteries in the house has been a concern would prefer in garage alas at end of garden . some 20m.  Apparently there is a no  to sending 200V dc or so underground  No shock protection against DC?  

Contacted my home insurance company : Disnt care about fire risk : I made sure they understood issue was about batteries in house not roof solar panels 

Is there a practical solution :  Do please let me know  Solar suppliers seem just menus take it or leave it . In the Loft.

ciao Ms O 

So many obstacles : Yes Volatile  lithium batteries Batteries in the house has been a concern would prefer in garage alas at end of garden . some 20m.  Apparently there is a no  to sending 200V dc or so underground  No shock protection against DC?

Indeed - hence the more usual design solution of using a.c. between the house and garage in that situation (PV inverter in the house to convert d.c. from the panels to AC then the battery system converts a.c. to d.c. to charge the batteries and inverts back again to a.c. when supplying loads). With a conventional grid-tied solution is comes out in the wash.

In the Loft.

Unusually for BSI, PAS 63100 is available as a free download so you can see for yourself - https://knowledge.bsigroup.com/products/electrical-installations-protection-against-fire-of-battery-energy-storage-systems-for-use-in-dwellings-specification?version=standard

  - Andy.

Hello Andy  "conventional grid-tied solution it comes out in the wash." I know you guys dont get this but as a punter if you contact solar suppliers . The glossies just look like greenwash to me.  

Love some simple answers ...  

 To begin  to size: no of panels / and number of sunlight hours I need in my area to boil  my ketlle ?  To run my washing machine for one hour . ?  ( No battery) thats the starting point. 

Can I switch a battery bank in and out  ( myself) according to time of year ? 

etc  ciao  Ms O  

The figures quoted for payback time on solar installs can be wishful thinking.

But a properly installed system requires no effort at all by the householder.  My inverter sorts everything out for me.  If there's spare solar power, it charges the battery.  If the battery is full, the excess goes to the grid.  If I need more power than the panels are producing, then it uses power from the battery.  All I need to do is log on from time to time and check everything is working.

The only thing I have ever had to do is reset the battery pack one time when an RCD tripped, the battery pack went flat, and the battery didn't want to turn on again to charge the next day.

Anne Otis said:

no of panels / and number of sunlight hours I need in my area to boil  my ketlle ?

With the latest 450W panels, about 7.  If the sun is in exactly the right place in the sky.  It only needs to be sunny for about 5 minutes while the kettle's on.

Anne Otis said:

To run my washing machine for one hour . ?

About the same, but the sun needs to be out for an hour.  Washing machines take most power at the beginning of the cycle.

Anne Otis said:

Can I switch a battery bank in and out  ( myself) according to time of year ?

Why would you do that?  My battery is connected 365 days of the year.

oh answers ??   ok  Can you be our Martin Lewis for real solar data ?  Can you calc for me ? 

Thought summer Boil kettle run washing machine ... u wave    other bonus : Dare I think oven ? Not all same time of course  

Batteries expensive  Extend life   As summer to autumn  switch  in one battery /  autumn to winter  switch  in another  ( x 2 )  

I will be reliant on grid  in the dim months .. and other times for sure .

But I would  have real time know of where it comes from and directing day to day to where it is being used.  Proposal is plug and play  My choice . You have an algorithm ?

Ms O  

My kit is entirely commercial off-the-shelf (COTS).  It's 18 Shűko panels, which are now totally obsolete as they are only rated at 190Wp each.  Then a more modern Solax inverter and an LG Chem battery*.

The exact details of how it all works together is dependent on the inverter and the battery management system in the battery box.  I don't know exactly what's going on.

Loosely speaking, it works like this:-

Are the panels generating more power than the house is using?

  Yes...

    Does the battery need charging?

      Yes...  Generate enough AC power to match what the house is using, and charge the battery with the rest.

      No...  Just generate AC.  The excess will go to the grid.

  No...  (and this includes at night)

    Is there any charge left in the battery?

      Yes... Use that to generate more AC.

      No... Tough, you're using grid power.

In practice, it's more complicated than that.  Charging the battery needs to slow down when it gets near 100%.  The inverter is limited to 3.6kW (and the panels to 3.4kWp).  The battery won't discharge more than about 2kW.

I'm relying on the battery management system (BMS) to protect the battery from over charging the battery or letting it go completely flat.  The BMS lies to the inverter.  When the inverter thinks the battery is completely flat, there's actually about 10% left.

*Luckily, the battery hasn't caught fire yet, even though it's made by LG Chem.  Their batteries are noted for their ability to spontaneously combust.  Last time I checked, the pack I have wasn't on the recall list.

My kit is entirely commercial off-the-shelf (COTS).  It's 18 Shűko panels, which are now totally obsolete as they are only rated at 190Wp each.  Then a more modern Solax inverter and an LG Chem battery*.

The exact details of how it all works together is dependent on the inverter and the battery management system in the battery box.  I don't know exactly what's going on.

Loosely speaking, it works like this:-

Are the panels generating more power than the house is using?

  Yes...

    Does the battery need charging?

      Yes...  Generate enough AC power to match what the house is using, and charge the battery with the rest.

      No...  Just generate AC.  The excess will go to the grid.

  No...  (and this includes at night)

    Is there any charge left in the battery?

      Yes... Use that to generate more AC.

      No... Tough, you're using grid power.

In practice, it's more complicated than that.  Charging the battery needs to slow down when it gets near 100%.  The inverter is limited to 3.6kW (and the panels to 3.4kWp).  The battery won't discharge more than about 2kW.

I'm relying on the battery management system (BMS) to protect the battery from over charging the battery or letting it go completely flat.  The BMS lies to the inverter.  When the inverter thinks the battery is completely flat, there's actually about 10% left.

*Luckily, the battery hasn't caught fire yet, even though it's made by LG Chem.  Their batteries are noted for their ability to spontaneously combust.  Last time I checked, the pack I have wasn't on the recall list.

That's why off-gridders always have batteries.

Indeed. And in a conventional grid-tied system, the consumer in effect uses the grid as a battery - sometimes exporting spare power to the grid, other times drawing power back. The need to balance supply with demand is quite a difficult problem if you don't have instantly accessible storage.

On the supply side, as mentioned power can reduce very significantly at a moment's notice. This is from my PV monitoring system from a couple of days ago  (yellow is PV generation, blue is consumption, light blue where they overlap):

then on the other side of the equation, remember that loads aren't nice constant things. Motors need extra "starting" current, even simple heating elements will draw more current when they're switched on - things that are often not clear from ratings plates.

   - Andy.

guys   AJ Simon and all sorry delay  : conclusions 

Proposed alternative solution to standard grid tie solar.  Partial off grid with independence 

I want to do this Believe viable alternative Sadly remain on my own .

Taken a long time to reach at least no objection to proposal is actually safe. For which  I thank all you guys for help 

Confidence to proceed hits another stumble  Volatile Lithium batteries in your house. 

Thought long and hard.  Given what we now know. I dont think I could sleep with those inside  Even with a fire canister next , 

The solar industry chooses again to ignore:  No solutions on hand 

I have not given up . Another hurdle I will find a way and prove  all my my doubters wrong  

All best  thanks again  to so many here in this forum who got me at least this far  Earthing. 

ciao Ms O 

If you don't like lithium ion, then you could go old-school and get lead acid batteries.  There are batteries that are specifically optimised for off-grid use.

Or the newer technology is lithium iron phosphate (LiFePo or LFP).  These are still lithium, bur are much less flammable than lithium ion.

Simon Barker said:

These are still lithium, bur are much less flammable than lithium ion.

I understand from the experts that investigate battery fires there are risks associated with the off-gas vapour from LiFePo or LFP igniting. A difference from lead-acid, though, is that the off-gas vapour might be heavier than air.

simon  Andy  G:k   

Thanks again : Lead acid  might have to lift the roof and crane them in  LOL  

Read PAS Is  it pointing to building fire regs  inclusion  soon ?  

Thinking place inv / batteries  on outside wall  Perhaps we just need a larger computer case with a fan  in it ?  Global warm maybe high temp is the enemy to life time Not cold .   None is addressing. 

None of this would be needed if I could simply place the thing in the garage . Foiled again by the the regulatory conspiracy to forbid  DC cables beyond 5 cm !   No protection technology available .  Though my solar supplier had no qualms about it over 20 m  Just wont guarantee .... 

The small print taketh away.  

Not given up yet but time runs out.

Andy "in a conventional grid-tied system, the consumer in effect uses the grid as a battery " 

 Really pull the other one ?   Buy hey 

all the best 

Ms O 

I think what was meant was

in a conventional grid-tied system, the consumer in effect uses the grid as a battery place to dump excess power into and then later to take power from to tide over whenever  the demand exceeds local generation.

 Perhaps more like a savings account at the bank, than a battery but for kilowatt hours, not money.

Well, and money too - depending on the contractual details

Mike

 Hmm   Can we just be clear 

The grid does NOT store energy :  If you want  it  ( even what you have regenerated) you wail have to pay for it ? 

Intrigued to know how this savings account  works ?

So all the solar grid tie ads had to be taken back to reflect : If your are out all day you will have to pay standard  tarrif  (because your solar has gone   somewhere and its dark  Never mind  Should have read the small print . 

Grid is not a public utility : It is a private business run for private profit  Like Thames Water. with Turds 

Love details of proposed  grid "savings account" 

 Convinces me more to go at least partially off grid .

Ms O 

Better get the batteries installed before they change the rules!  Building regs aren't retrospective.

well maybe tthe grid is more like a payday loan then.

My point is that banks don't store your money either - its not like they have a shoebox per customer stuffed under a big bed out the back (its not really like the bank in this sketch)

Rather they actually lend your money out to someone prepared to pay more for it who uses it there and then, and then when you ask to take your  money out, actually you some get money that someone else recently paid in.

The grid is much the same. The excess electricity you put in supplies someone else's load at that moment , and you get paid for that. The electricity you take out at other times when clouds cross your solar panels, you pay for in the normal way

A real example a colleague of mine uses https://octopus.energy/smart/intelligent-octopus-flux/

and that system charges the batteries in his garage  from solar panels when it can, and when solar power is weak, then charges from the grid when it is cost effective to do so, and he exports to the grid at times of high demand and gets paid over the odds for it - usually early evenings. So far on average over any one month the company have been paying him more than he pays them, even in the winter....

Mike.

The grid does NOT store energy :  If you want  it  ( even what you have regenerated) you wail have to pay for it ?

Physically it does works that way, Yes there are payments involved - but that's political rather than physical. In other parts of the world exports are handled by simply letting the meter run backwards - so you would get back what you put in for free. Here there are payments involved, but it's not a one-way street - you also get paid for what you export (most smart export tariffs are offering around 15p/kWh at present). As Mike pointed out, time-of-day tariffs are available (anything from old E7 to Octopus's agile) which means it's possible (if not always convenient) to be paid more per kWh for what you export than what you'd pay for import.

On the other side of the coin, storing electricity in a battery isn't exactly free either - the capital cost is high and the number of charge/discharge cycles limited before the battery needs replacement. Some back of an envelope calculations a while ago gave me a very rough rule of thumb that it cost 10p to store 1kWh in a home battery.

  - Andy.