So now I have a solar PV system how do I make the most of it???

sly_dog_jonah

Hi Dave,

In case 1 I suspect the reason is reflection from the snow rather than off the clouds.

In case 2 I think it's down to refraction (bending) rather than reflection (bouncing).

John_Pierpoint

Anyone know which part of the spectrum is most useful to the PV panels?

By definition in a clear blue sky the panels get the benefit of direct sunlight plus a bit of predominately short wave (blue) radiation from the rest of the sky,

Perhaps those whose panels are on a beach front (South) coastal property could get some significant reflection from the sea.
[I have fond memories of my office worker body arriving on a beach in Cuba and thinking "this sun will fry me in a trice", so for the first session I sat and read well into the mouth of a convenient cave - still got all over sunburn though]

John_Pierpoint

I have some misgivings about the response of my "historic" electrical system, now that it has an extra 3Kw input.

Picture this:
I live in a house rewired in the early 1970's. It has wire fuses and one large old brown earth leakage circuit breaker.

The PV panels were provided with their own mini "consumer unit" - the sort that would be added if one built a garage/workshop. This has a miniature circuit beaker and to be sure its own earth rod.

We have a free standing but of course hard wired electric cooker. It was new circa 1980 and inherited from the in-laws when they bought their brand new dream retirement home - which came complete with a fitted kitchen. The cooker is the "bling" product of an Italian stylist, rather than a German engineer, if you know what I mean. So with 4 ceramic rings, two ovens and a grill, it is capable of overloading its 30 amp wire fuse. For this reason there is some sort of link that prevents the eye level grill and the eye level oven (which share the same "box") from being turned on at the same time.
It was about noon and we were expecting guests for lunch, DW had cooker going full power and I just happened to be sitting at the top of the the loft ladder from the kitchen to my attic "office" admiring the inverter; having been sent into my "attic" office to hide some junk from our guests.:

- "woo..." from DW.
- "thumnp..." from cooker.

DW had accidentally tried and succeeded in turning on both grill and top oven at the same time and, it was pretty obvious, that the whole cooker had shorted to earth somehow via the grill knob.

- "don't touch it, let's turn it off at its mains switch".

It is not exactly clear what happened BUT in the hall cupboard there was smoke still misting from the earth leakage circuit breaker, it appeared to have worked, in that the slider had dropped out, in theory cutting off the the electricity supply that comes into the house in this order -> company fuse -> modern (flashing) meter & aged mechanical time clock -> Earth leakage circuit breaker -> heavy duty new junction box -> left to the new consumer unit and right to the old fuse box.

However the inverter was still generating!!!!!

So perhaps it was just coincidence. Perhaps this was the first time the aged earth leakage circuit beaker had perhaps been require to handle such a massive failure to earth? But was the extra 3kwp available that kept coming the last straw that has welded the insides of the circuit breaker?

Producing lunch was the priority, so I turned off the mains and each of the two strings of panels before taping off the faulty knob for the grill "resetting" the earth leakage circuit breaker and discovering that the 30 amp fuse had been forced to blow to cut off the short in the cooker.
So I repaired the fuse, turned the inverter back on and the lunch hardly noticed the 20 minutes of drama or should that be trauma:D.

Everything has been running as normal since and I have not had time to investigate [it is against the regulations to investigate your own wiring and cooker these days I think?]

Watch this space as I have to haggle over the costs of modernising my fuse box arrangements.

EricMears

John_Pierpoint wrote: »

it is against the regulations to investigate your own wiring and cooker these days I think?

It's a pretty grey area !

It would probably be against Part P of the building regs for you to install a new circuit including a new CU but repair of existing circuits shouldn't be and 'investigating' isn't even the same as installing. I think wiring regs still refer to a 'competent person' without ever defining who that includes ! Only real test is that if it all blows up after you install it you probably weren't 'competent'

The 'extra' earth rod should be a separate earthing point for the solar panels which is independent of the "board's earth" rather than an attempt to 'beef up' the normal earth. The theory is that a DC fault from the panels might just mess up earthing for the neighbourhood (far fetched as that probably sounds).

If the solar panel system was still generating when the ELCB had turned off, it sounds as though the new cu for that system has been connected to the mains before the ELCB rather than after as you describe (or else the ELCB isn't CBing !)

Martyn1981

sly_dog_jonah wrote: »

Hi Dave,

In case 1 I suspect the reason is reflection from the snow rather than off the clouds.

In case 2 I think it's down to refraction (bending) rather than reflection (bouncing).

Can I show my ignorance here. I also assumed that higher afternoon generation was from reflection. Like D&D, I'm ESE and generation for the past week has been great, but once the sun has passed over the roof, it's dropped to about 200W or less. Yesterday however, it was generating 400 to 500W right up to 5.30pm, and 100W close to 6.30pm.

I don't know the correct term for this, reflection or refraction, but it's definitely more when the sky is whiter. We had a stunning clear blue day, early winter (I think), fantastic generation, but the moment there was no direct sunlight on the panels, my systems actually shut down (first time I've seen that, hasn't happened since yet, as it was a perfectly clear sky). Inverters valiantly kept flashing and clicking away for an hour or two, but never staying on for long, or generating anything more than 10W or 20W.

Perfect weather therefore for me, is clear blue sky till 3ish, followed by medium thick white cloud - sorry West'es!

Mart.

zeupater

Martyn1981 wrote: »

Can I show my ignorance here. I also assumed that higher afternoon generation was from reflection. Like D&D, I'm ESE and generation for the past week has been great, but once the sun has passed over the roof, it's dropped to about 200W or less. Yesterday however, it was generating 400 to 500W right up to 5.30pm, and 100W close to 6.30pm.

I don't know the correct term for this, reflection or refraction, but it's definitely more when the sky is whiter. We had a stunning clear blue day, early winter (I think), fantastic generation, but the moment there was no direct sunlight on the panels, my systems actually shut down (first time I've seen that, hasn't happened since yet, as it was a perfectly clear sky). Inverters valiantly kept flashing and clicking away for an hour or two, but never staying on for long, or generating anything more than 10W or 20W.

Perfect weather therefore for me, is clear blue sky till 3ish, followed by medium thick white cloud - sorry West'es!

Mart.

Hi

That's the result of both refraction and reflection within the cloud structure itself .... thin layers of cloud act as a diffuser therefore indirect irradiation strikes the panels where in extremely clear sky conditions the panels would be in full shade ....

HTH
Z

John_Pierpoint

EricMears wrote: »

The 'extra' earth rod should be a separate earthing point for the solar panels which is independent of the "board's earth" rather than an attempt to 'beef up' the normal earth. The theory is that a DC fault from the panels might just mess up earthing for the neighbourhood (far fetched as that probably sounds).

If the solar panel system was still generating when the ELCB had turned off, it sounds as though the new cu for that system has been connected to the mains before the ELCB rather than after as you describe (or else the ELCB isn't CBing !)

That is interesting, the installer of the PV panel also strapped the new earth to the copper rising main - not sure if that is an effective earth or not, as underground it is a black polythene pipe.

I was thinking it might be useful if both the new and the existing earths were strapped together, but perhaps not from what you say.

[My only experience of an earth or rather the lack of an earth, was when the combine harvester driver scraped the earth wire running down the pole outside, to earth the so called "neutral":
That upset the balance of things, when my neighbour started up his big compressor, my Earth Leakage Circuit Breaker helped out by recognising the surge in the black neutral wire as a fault and protectively turning off my electricity.
This was happening every day in the winter soon after 08:00, and most days after we had left for work, it took me some time to realise it never happened on a Sunday. ]

(or else the ELCB isn't CBing !)It is not now, after Sunday's smoke in the cupboard incident, so I will need to get someone to look at the situation. Even I think that the ELCB is an improvement in technology, even when you sometimes get false positives. [I think my late mother managed to live all her life in a property without one, but 30 amps is quite enough current to start a fire (or kill a human) without blowing a fuse.]

Unfortunately the house wiring is a bit like telephone extension wiring -
now the electricity company's responsibilities stop at the meter, just as BT's phone responsibilities stop at the master socket.

It is all happening this week, I have an appointment with my power supply sub contract engineer - perhaps installing PV panels in a 40 year old electrical system seeks out the existing weaknesses - the time clock on my "Economy 7" is now on its last legs.

EricMears

John_Pierpoint wrote: »

That is interesting, the installer of the PV panel also strapped the new earth to the copper rising main - not sure if that is an effective earth or not, as underground it is a black polythene pipe.

I was thinking it might be useful if both the new and the existing earths were strapped together, but perhaps not from what you say.

I was pretty astonishd when my panel installer announced he had to provide a new earth. I could see some merit in what he was saying for 'normal' houses where the REC really do provide an earth point but our house is fed from a transformer on an adjacent pole carrying 11kv and its earth and neutral are provided from a couple of earth rods & a bit of copper netting buried at the foot of the pole. Quite how our 'independent' earth rod 40 metres away makes any difference I really can't see. If both earth points are good ones then surely they're effectively joined together anyway.

In your case, he's obviously attached his new earth to your water pipe for 'bonding' rather than actually expecting the supply pipe to provide any extra earthing. I'd guess he realised pipework wasn't earthed and the bonding should ensure that all parts of the house are at same potential. Bonding isn't something that applies here - no gas pipe and all water pipes are plastic.

John_Pierpoint

Come to think of it, traditionally in Essex the cold water taps are all directly off the rising main. [Unlike metropolitan London where there was only one obscure cold tap directly off the rising main and all the other cold taps came from the tank in the loft] So bonding my rising main is probably bonding the rest of the system via the bath or sink mixer tap and bypassing the "fold it up and push it through the hatch" plastic option of a holding tank in the loft.

All my pipes are copper, apart from the tap in the yard; that is one of those that regularly freezes back into the ground, black plastic jobs.

John.

PS Firsts small shower of rain for about a month today = a production graph that does not look like a bell curve or a hedgehog but 9 kWh of "The three peaks". The middle one was a really Disney Land of a peak with a record peak value for output watts, given what must have been surrounding clouds with reflection/refraction.

davidanddeirdre

Martyn1981 wrote: »

Can I show my ignorance here. I also assumed that higher afternoon generation was from reflection. Like D&D, I'm ESE and generation for the past week has been great, but once the sun has passed over the roof, it's dropped to about 200W or less. Yesterday however, it was generating 400 to 500W right up to 5.30pm, and 100W close to 6.30pm.

I don't know the correct term for this, reflection or refraction, but it's definitely more when the sky is whiter. We had a stunning clear blue day, early winter (I think), fantastic generation, but the moment there was no direct sunlight on the panels, my systems actually shut down (first time I've seen that, hasn't happened since yet, as it was a perfectly clear sky). Inverters valiantly kept flashing and clicking away for an hour or two, but never staying on for long, or generating anything more than 10W or 20W.

Perfect weather therefore for me, is clear blue sky till 3ish, followed by medium thick white cloud - sorry West'es!

Mart.

Mart, well said, I could have put it like this in the first place. Why didn't I?
I am happy with overall PV results despite less than ideal direction, we achieved well over the predicted output for our first year.