Solar Electricity generation

[NikNak]

Bob....


Your last posting on this subject seemed to be around 18 months ago.... any update, news, etc you'd care to share with us..? I've tried your 'link' but it doesn't seem to work...

We too are doing our 'bit' to be green, new condensing boiler, loft and wall insulation, low energy bulbs, 7 (yes 7) water butts, thick lined curtains, eco f/freezeer, eco washing machine, blah blah blah...... and are now thinking about some PV solar panels as the prices seemed to have dropped enormously over the last year.

Just had a quote to supply and install 14 x 250w panels i.e. a 3.5kw system, for a smidgen under £5k. The only thing the quote doesn't seem to include is a gadget to tell you how much it is generating 'now' so you know its the best time to use all that free 'lecky, so i shall ring em and ask if that's included too.



Nick

 

[Dibs-h]

I'm no longer active on this forum. If you want to contact me try [email protected]

I don't think Bob visits anymore.

HIH

Dibs

 

[Harbo]

He's also on holiday.

Rod

 

[DrPhill]

I have had solar pv for 18 months. Some points:
(1) Ignore the reduction of consumption term in the cost/benefit analysis. Unless you have heavy leccy use that you can shift to sunny days. Mosy of my leccy is consumed when the sun is not shining.
(2) Investigate an export meter. I wish that I had. We use very little electricity, probably less than half of what we generate, so that we are losing a bit of the feed-in tarriff.
(3) Generation seems to be approximately what was predicted, except that this year has been very wet. We are tracking to 10 year payback.
(4) Calculating payback confuses my poor little brain. I calculate two values:

• 
  *(i) How long before the cash gets payed back assuming no loss of interest and no inflation. This is a simple but misleading measure that just compares quidspent with quidsgot. This figure implies a quicker payback, as payments rise with inflation.
  *(ii) Return based on leccy units. I spent 25000 leccy units worth of quids to get the thing installed. Since leccy units are (roughly) inflation linked I calculate how many leccy units I have been payed for. This is the figure that implies a 10 year payback. This may or may not be more accurate than the former.

(5) The income from the roof is ignored by both the taxman and the benefits means-test (not that the latter helps me). That increases its value relative to savings interest which is taxable (unless in an ISA etc).
(6) Move the TV ariel from above the solar panels to avoid a drop in generation due to doppings.......

HTH

Phill

 

[dickm]

£5k for an installation of that size sounds VERY good. We paid a lot more for a 3.9kW installation two years ago, but at least we get the 43p feed in. Total generation this year was about 5% down on the first year, but we haven't had a summer! Best generation was actually in May and October - June to September were a washout. Daughter in the next village has a newer installation, using (I think) Sanyo panels which appear to be more efficient than our's - their generation this year was 5% over prediction, so it may be worth checking what spec of panel your installer is offering.
Agree that it's difficult, but it's not impossible, to push more of your consumption on to the panels. If your wiring and appliances are all reliable, it may be worth putting things on timers to run them during the day, even if you are not in the house.
We decided not to go for an import/export meter as we still probably use more than 50% of generation.
We are on track for a 10year basic payback too.
One thing probably worth doing is looking at maintenance contract; it's not clear how long inverters etc. will last, and difficult to know if panel performance is degrading over time. A good installer should cover these things at an annual inspection.

 

[Eric The Viking]

The scam, er, scheme has ended. The gravy train (for the installers) is hitting the buffers: it's now a buyer's market.

 

[Benchwayze]

As we are discussing Solar Panels:

My house ridge runs directly N/S. So:

Do you HAVE to have the panels on your roof or could they be fitted on the flat garage roof, at 45 deg lean-to against my South facing house wall?

TIA

 

[wobblycogs]

As long as they point at the sun and have a clear view of the sky you can fit them anywhere. We're planning on putting them on a flat roof - once it's been built.

 

[Benchwayze]

Thanks Wobbly.
I take it the best plan is to have them on a driven, equatorial mount then.

I could put them on the East facing pitch of the roof, with a full 180 degrees of clear sky, but after dinner time, the old Earth has rolled around a bit; whereas, in the summer, and on the South facing gable, they would get Sun for almost all of the day.

Cheers again.

 

[dickm]

Oddly enough, just noticed that a house in the next village with a ridge running north-south has just had eight panels fitted on one side and eight on the other. It would need either two inverters, or one that will accept more than one array, but is probably quite an efficient arrangement.
A friend down in Yorkshire who has a reasonable amount of land has had his panels ground mounted, which works really well because you can optimise the angle to the horizontal. But he hasn't (yet ) installed a rotator as well.

 

[Benchwayze]

Thanks ****.

On the West-facing pitch there is no view other than next door's roof! That's the side planning would have had me fit a dormer for a loft conversion BTW!

A rotator I presume is a driven, equatorial mount, (as per Astronomical Telescopes.) to counter the Earth's rotation, so as to remain trained on the desired object. In this case, the Sun. I think I'll just lean them against the bathroom wall, beneath the window. !!

 

[Robbo3]

To come in late on this subject..... my 2.1k system is now 14 months old & has given me a cash return of approx £1000 plus lower bills over that period.

I obtained three quotes & asked a number of questions about the system. Below are the answers that I got.
Although I didn't know until he arrived, the installer I chose was a school friend & he confirmed these answers.

East & west facing arrays are approximately 15% less efficient than south facing arrays.
The system accepts input from each panel at the rate of the lowest performing panel, therefore if your panels face a mixture of directions it drags the overall efficiency down. This can be overcome with a second invertor but probably not worth it due to cost.

Replacement costs : Invertor £800, photovoltaic panel £200.

Remember the panels are photovoltaic meaning that they convert light into electricity, Don't get them mixed up with solar heating panels which rely on gaining as much heat as possible.

In our area planning permission is not required for roof mounted systems (excluding listed buildings etc) but planning permission is required for a ground array.

HTH
Robbo

 

[misterfish]

The system accepts input from each panel at the rate of the lowest performing panel, therefore if your panels face a mixture of directions it drags the overall efficiency down. This can be overcome with a second invertor but probably not worth it due to cost.

We' ve got 15 panels but due to roof shape and size they couldn't all be mounted with identical orientation so they are divided into 3 batches of 5 panels, Rather than having 3 invertors we have a single multistring convertor that allows each group (string) of panels to be processed separately.

As for actual production - last year we produced 119% of the expected certificated calculated value for our system. This year, despite the poor weather we have produced 111% of what would be expected to date.

The vital requirement fo PV is to ensure that shading is kept to a minimum - in our case early in the morning.

Misterfish

 

[gregmcateer]

We've just got 6 x 250w panels due to roof shape. Probably could have squeezed more on if risked wrath of authorities.
Even so, we have cut our leccy cost by nearly 40% over this shockingly poor year AND had back a bit under £400 in FIT (feed-in tariff) payments - So I am pretty happy with them.

 

[dickm]

One thing it's worth noting is that councils are supposed to allow PV panels without any problems, unless they are on a listed building. Certainly up here, they are deemed to be "permissible development". The directive from Govt to that effect is one of the few examples of Westminster actually having any interest in green issues.

 

[Robbo3]

We' ve got 15 panels but due to roof shape and size they couldn't all be mounted with identical orientation so they are divided into 3 batches of 5 panels, Rather than having 3 invertors we have a single multistring convertor that allows each group (string) of panels to be processed separately.

Interesting. How much more expensive was a multistring convertor?

Our property is 'L' shaped with south & west facing legs of equal length. One company wanted to put panels on both roofs with two invertors, but I wasn't interested & didn't pursue it any further. I wish that perhaps I had now.

Robbo

 

[misterfish]

Our system uses a Fronius IG30 inverter - and each of the three strings of panels feeds into it with its own cables. I think the current cost of an IG30 is about £950. Although our panels all face in the same direction (SSW) there are 5 on the main roof and 10 on the flat roof with each of the groups of 5 at a different angle. This layout was only decided after a very thorough survey using a specialist solar meter and software that measured the light levels all over the roof and which took account of all potential shading from chimneys, gables etc as well as other light reflections. The survey took about three hours and assessed the potential generation throughout the year.

Misterfish

 

[NikNak]

Well..... we went for it... :shock:


A 3.5kw (14 panel) system, facing roughly SE'ish (but probably a tinsy bit more to the E), fully installed and g'teed for...... £4600


Here's a few piccies for you to see....

would have preferred a 'portrait' layout as they call it, but would only have got 12 panels on. So they suggested this layout for 14 panels, and i must admit it sort of 'suits' the roofline....

The SMA Sunny Boy inverter is mounted in the garage, which is approx 20 - 25 mtrs from the panels, and the mains consumer unit is approx 2.5 mtrs the other side of the garage wall in the little room downstairs.

The green light on the display panel is showing its 'generating', and the blue light is the bluetooth 'activated' light i.e. the comp is downloading the data as seen in the last chart pic (the software is freely available from the SMA website).


We've got one of those 'Owl' thingamys in the kitchen, been there for nearly 3 years now, and shows how much 'lecky we're using etc. funny thing is, its started to do weird things now this is up and running...... as in it goes UP when lecky is being produced, and then down when we turn something on... :shock: (i've searched Owl's website and it seems this is normal, we will need 2 gadgets now if we want to monitor 'realtime' whats being produced and whats being used, without resorting to turn the comp on and use the SMA s/ware).

I know its only been 3 days since install, but must admit so far we have not regretted it and looking forward to the summer...



Nick

 

[dickm]

Can't quite read the scale on your graph - what is the peak generation on that day? And what is the (rough) slope of your roof? Somewhere I've seen it suggested the panels should be at latitude plus 5 degrees. Difficult on a bungalow in Northern Scotland, but probably OK for a house in the sunny south.

 

[NikNak]

Hi,

peak on that day (1st day of generation...) was 1.668kw, total for the day was 4.874kwh

slope.... ummm... 30° ?? ish :? (if i was any good at maths i could work it out... maybe... )



Nick


oh, meant to say... each of the 3 days so far have started with quite a heavy frost which (although still generating) takes quite a while to clear from the panels.