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

pwllbwdr

grahamc2003 wrote: »

If you want a rough estimate of the savings solar will give you with your setup, probably the easiest way is to do it graphically (a few years ago I would have easily calculated it analytically making reasonable assumptions - anyone care to have a bash?).

If you want to try it, get some graph paper, and plot time on the x axis and power on the y. Assume the average or typical output for your panels - probably a Gaussian (or normal or bell curve), start at 06:00 with 0kW, then plot to get your kWp (or 70/80% of it) at 12:00, then back down to zero at 18:00 (Just draw a bell shape hitting those points). Next, plot on top your AGA load, approximated by a 2.6kW load on half the time (say 1 hour on, one hour off, all through the day - so you get a superimposed square wave.

The graphs will show (roughly, under those assumptions) how your generation will cover your load, and the area under both the Aga load (the square wave) and the solar generation (the gaussian) will, give you the energy covered (in kWh), so simple to see how much that saves you (by multiplying by your cost/kWh).

From that basic approach, you can refine it to death - first refinement would be to estimate your background load (I'd assumes 100W in my case), and offset the aga load by that.

(BTW to preempt responses from various quarters, this is an estimate, not an exact science, and it won't produce an exact answer, but it wil produce an indication of likely savings - there are thousands of refinements can be made to get a close approximation to the answer.)

Thanks Graham - worth doing, but I'll do the sums properly (I'm a physicist).

grahamc2003

pwllbwdr wrote: »

Thanks Graham - worth doing, but I'll do the sums properly (I'm a physicist).

'Properly' is a bit debateable here - if I could remember the calculus required I'd prefer that method too, but I have a lot of time for geometry, simply because it was the only maths available for several centuries. Incidentally, something I found interesting (not sure if it's common knowledge or not), the integration sign is a stretched 'S', for sum, or 'area under the curve', indicating its derivation from geometry.

Anyhow, if you have a go using calculus, I'd be interested in seeing the solution.

adrian2

Hi All

Does anyone know if you can add panels to a solar system, we currently have a 4kw system with 16 panels.

Thanks in Advance

Adrian

macman

Yes, if roof space and alignment permits. But remember that you'll get a lower FITs rate beyond 4Kw, so I doubt it'll be worth it-depends on the no. of extra panels
You may also need a higher rated inverter.
Unless you're talking of many more panels, I can't see the payback, especially as the whole system will have to be recertified at the currently applicable lower FITs levels.

zeupater

macman wrote: »

Yes, if roof space and alignment permits. But remember that you'll get a lower FITs rate beyond 4Kw, so I doubt it'll be worth it-depends on the no. of extra panels
You may also need a higher rated inverter.
Unless you're talking of many more panels, I can't see the payback, especially as the whole system will have to be recertified at the currently applicable lower FITs levels.

As above plus ....

.... the question of whether the expansion will be in the same year as the original installation as well as involvement/permission of the DNO for installations >16A.

HTH
Z

rogerblack

grahamc2003 wrote: »

'Properly' is a bit debateable here.

Doing it using integration of averages is the very improper way to do it.

http://www.pvoutput.org/intraday.jsp?id=3744&sid=2940 - for example.
With a bit of scripting, you can download 10 minutely intervals from a site near you.

This lets you do more accurate what-ifs.

Martyn1981

zeupater wrote: »

As above plus ....

.... the question of whether he expansion will be in the same year as the original installation & involvement/permission of the DNO for installations >16A.

HTH
Z

I'm probably confusing myself here, but I thought the 'change inside 12 months' bit, was dropped last year?

The result now being, that if the Total Installed Capacity of the system is increased by adding an extension then the 4kW system will continue on the existing tariff and the new part will be paid at whatever the tariff is at that time, and appropriate to the cumulative total. This could be repeated for extension after extension, each being rated at the then current FIT, but against the cumulative kWp total.

Each part will run for their own 25 year term. If you only have a single meter then the readings will be pro-rated between the two tariffs.

E.g. If another 3kWp was added to the existing 4kWp, then the original system rated at up to 4kWp will stand as certified. The second system of 3kWp would be rated, separately, at the lower 4 to 10 rate (since cumulatively it is part of a7kWp system).

Issues regarding inverters and DNO would of course need serious consideration.

Mart.

macman

So you are saying that it is possible to apply a split rating to one system, or effectively have it treated as two separate systems, but with a cumulative total applicablefor the combined kW rating?
I wasn't aware of that.
Would that not then require a separate export meter for each extension, and a separate meter reading?

John_Pierpoint

Physically you can, if the roof is large enough; you would almost certainly need a bigger inverter, but your FiT provider and the operator of the local net work might spot the anomaly; expect hassle at some point even if by using a high percentage yourself, with clever monitoring kit, you were not at risk of de-stabilising your local bit of the grid.
"The regulations are the regulations we cannot have every Tom !!!!!! and Harry churning out local electricity."

The thought has occurred to me, as I don't face due south, could I put up 20 instead of 18 panels.
In theory I even have an inverter designed for California that is capable of throwing ways excess power if needed.

The panels these days, especially Chinese ones, are getting very cheap.

Mind you that said, I remember having a similar discussion years ago about a starter level mini computer/word processor - in the days "before PC" when there was still a central processing unit and some terminals.

Though there were three levels and three prices. In reality everyone got the expensive version but it was down graded for those skinflint installations, until such time as they paid for "an upgrade".
The upgrade simply involved putting a few new connector wires inside the cabinet.

teachergirl

Aaaarrgh just posted a long reply and then lost it:mad:

Gist of it was very sunny in Essex today after a poor week. Have generated over 19kWh already and there are still a few hours to go. At one point I had the washing machine and the tumble dryer on and I was still exporting. Now I know things change in the cycle and a cloud could come over but my hubby and son have just come from skiing and there was a mountain of washing and drying which needed to be done . I'm just glad that it cost me at lot less than before I had solar panels. Better go and do the ironing before it gets dark!!!!!!!!:D