Solar Panels Query

[Nix]

If you can get hold of any of the installer's documents/quotations/etc?

Even though it is a grid tie affair, you can still tap into it for a temporary back up without touching their equipment but it is better to be able to access the panels for a long sustained back up for obvious reasons. I've got an idea for easy panel access but still need to know some details...

[River Song]

OK - I've got a little more information but not a lot.

The Solar Panels are to be installed 2nd week September

Solar Panels on roof go to inverter in loft. No idea of size or spec.
There is also by the inverter some kind of AC/DC switch / Isolator.

From there is is fed to the mains/grid.

In the event that Grid fails then I have nothing. Ideally, after the installers have left, :-)
I would like to take a spur of some kind and charge some batteries and then run some 12v circuits
for fridge etc etc etc

I must admit its nice to have someone else pay for this lot. I don't mind paying for the extras.

The guy says the idea is to run as much electricity as possible during the day when its free
but how do you know that you are using too much and therefore paying for the extra?

it's all far too technical for a blonde ;-)

[Nix]

I reckon the best thing is to get specifics from the installers themselves. Need to know the voltage of the panels they're using which I'm 99.9% sure will be 24v, then what will be the configured input voltage to the grid tie inverter. Check what size cables they've got and that they're using MC4 connectors. Also, from your end, what exactly are you wanting to power? We can work it from there...

[Binnie]

(22 August 2013, 17:57)BeardyMan Wrote:

(21 August 2013, 21:29)Highlander Wrote: Although leisure batterys are ok, they dont recommend them [ in a perfect world] leisure batterys are designed for starting things there are deep cycle batterys designed for this job that do the job better, if you have the time and money to spend in preperation

I have just bought a bank of 6 batteries at just under £800....
http://www.ebay.co.uk/itm/27TMH-Trojan-B...4174804279

A leisure battery is a deep cycle battery? They're used in narrowboats/caravans etc

Someone told me that the best ones you can pick up for the price are used golf cart batteries.


To hook your panels into a battery bank instead of the mains you need to drop back to a basic PV - Charge Controller - Battery set up. So into the loft, where the connectors from the PV panels terminates in the inverter you have in the roof, swap this with your charge controller, then feed that into the batteries.

Of you could be really fancy and stick a switch/relay in there (before the inverter / charge controller) and divert the flow of electrickery wherever your heart desired.

Deep cycle batteries are batteries that tolerate long discharge periods, automotive batteries don't like being discharged that much, and fail quite quickly.

Traction batteries (golf carts, forklifts etc) and leisure batteries (boat/caravan) are both "deep cycle" batteries, designed to be discharged for long periods.

HTH

[Highlander]

(23 August 2013, 12:56)River Song Wrote: The guy says the idea is to run as much electricity as possible during the day when its free
but how do you know that you are using too much and therefore paying for the extra?

You cant really answer this River, if you have a 3kw system, which it probably will be, [ we need to know how many panels when you know], then if the sun is blazing, you could be producing 3kw at any one time,.. then you would be hard put to use more than you are producing

As the days get less sunny, you will get less energy free,..etc, etc

But remember that you still pay your electric bill as normal,.. so if your bill was normally £600 a year and we have a good summer, your bill will be considerably less ,.. you will still have a bill though, because you will bound to use more in the winter than you produce

Last year we produced more electric than we used, and made over £400,.. but of course we also get paid the tarriff at 43p per unit,.. that money will go to your landlord,..[ well its not that much now, its something like 20p per unit ]

[Nix]

(23 August 2013, 17:36)Highlander Wrote:

(23 August 2013, 12:56)River Song Wrote: The guy says the idea is to run as much electricity as possible during the day when its free
but how do you know that you are using too much and therefore paying for the extra?

You cant really answer this River, if you have a 3kw system, which it probably will be, [ we need to know how many panels when you know], then if the sun is blazing, you could be producing 3kw at any one time,.. then you would be hard put to use more than you are producing

As the days get less sunny, you will get less energy free,..etc, etc

But remember that you still pay your electric bill as normal,.. so if your bill was normally £600 a year and we have a good summer, your bill will be considerably less ,.. you will still have a bill though, because you will bound to use more in the winter than you produce

Last year we produced more electric than we used, and made over £400,.. but of course we also get paid the tarriff at 43p per unit,.. that money will go to your landlord,..[ well its not that much now, its something like 20p per unit ]

Absolutely right.

You should have a meter you can refer to at any given time to see what's happening with your system. On cloudy days it'll change from moment to moment. During a dark winter's day, you'll struggle to see any advantage other than trickle charging your battery bank but on a bright summers day, you'll have so much excess, you'll struggle to use it!

[Skvez]

River Song,

Given that this isn't your house you should probably avoid messing with the system at all before SHTF.
For after SHTF you can ignore the whole system except the panels where you have a lot of pre-fitted panels on the roof.
You will then need to re-wire the panels and supply a charge controller, batteries and either DC wiring or an inverter (possibly both).

You really need to discover the nominal Voltage of each individual panel.

A "3kW system" will never produce 3kW in the UK, even on a sunny cloudless day in July at noon.
The biggest mistake people make with solar is to expect it to produce 100% of what it's theoretically rated to be capable of producing.
I did a post a few years ago on a solar panel I few into a data acquisition system recording data every 10 minutes across a whole year. It shows realistic levels of power expected in the UK compared to the panels rating.

Even if you were getting 3kW, it's very easy to exceed 3kW with a cooker or an electric shower.

[Highlander]

(26 August 2013, 17:10)Skvez Wrote: River Song,


A "3kW system" will never produce 3kW in the UK, even on a sunny cloudless day in July at noon.

Last year, we had one of the best sunny summers for years, and our 3.6kw system did once read 3028wh

[Nix]

This will sound a bit weird but solar panels are actually more efficient on a cold sunny winter's day than a hot sunny summer's day.

I've recorded 1.4kW on a sunny but cold May day this year from my 1.25kW system.

[River Song]

It still remains very difficult to get accurate information from the installers.

The proposing to install 12 panels on the roof.
Voltage they say around 400v DC
Into an inverter of some kind and then into the grid.
There is also an isolator for some reason.

I've been told that if the grid is down then i get nothing.

Ok so this is where I need some help.

I can't do it until after it is installed but I certainly dont want to wait until TU

so what can you suggest?

Possible some form of charge controller?? Going to 2 x deep cycle batts
running some form of 12v circuits in the house?

Any ideas? Can you point me to some authorative resources I can read?

Cheers