Solar Electricity generation

[dickm]

What are the practical aspects of installation from the cabling point of view? Distance from panels to meter, capacity etc.

Not sure about the total distance that is acceptable, but my guess is that only the distance from panels to inverter is critical, because it's lower voltage/higher current. Our inverter is in the loft, about 3 feet below the panels, and that seems to be the preferred arrangement. Then from there down to the meter (by the consumer unit, but I guess it can be anywhere convenient) it's standard 240V 2.5mm2 cable. So could probably be quite a long length. (I assume you mean current capacity?)
Our panels are Moser Baer, which despite the germanic sounding name are actually Indian.
Labour was less than 5% of the cost of the installation - the hardware is the expensive bit.
We used a local-ish installer, E-motion Energy, based in Stirling, but they have branches in Birmingham and Belfast and possibly elsewhere. I'd recommend anyone interested at least to try them, as they seemed to be keen and were not out of line on cost.
It's interesting that we are now getting a steady stream of offers to install Solar PV from others getting in on the act.
Like Bob, I'm assuming/hoping the system will outlive me, so the residual value is of academic interest only.

 

[9fingers]

I did look at solar water heating and rejected it on the grounds of
1) much lower payback rates on capital employed (A friend has spent £4000 and is saving £200 pa and will be fortunate to live another 10 years))
2) The system would have to be on my house roof and that is shaded by next door whereas the PV system can go on my workshop roof which is not shaded.

Bob

In our case the Solar Option can't really go on the house as it's E-W facing whereas the shed roof is S facing and slightly closer to where the "tank" will live as opposed to roof (3 stories up).

I'll have to dig out the spready again and see what the savings are likely to be. The marginal cost for us to go solar would be <£2k and the potential savings far more than £200 (probably double) so for us.

Cheers

Dibs

I think my pal paid too much for his system but he is not a diyer or aware of what things would cost. he did get a dirty great thermal store installed in the loft as well as the panels

There is only him and his wife and he admits he can't use all the hot water that a 20 tubes system produces.
A family with kids would use a lot more DHW so I agree the payback will likely be much better for you.
Also i think you are allowed to install some of it yourself for further saving.

PV systems must be installed my register installers in order to qualify for the FIT and the 5% vat rate.

Bob

 

[9fingers]

What are the practical aspects of installation from the cabling point of view? Distance from panels to meter, capacity etc.

Not sure about the total distance that is acceptable, but my guess is that only the distance from panels to inverter is critical, because it's lower voltage/higher current. Our inverter is in the loft, about 3 feet below the panels, and that seems to be the preferred arrangement. Then from there down to the meter (by the consumer unit, but I guess it can be anywhere convenient) it's standard 240V 2.5mm2 cable. So could probably be quite a long length. (I assume you mean current capacity?)
Our panels are Moser Baer, which despite the germanic sounding name are actually Indian.
Labour was less than 5% of the cost of the installation - the hardware is the expensive bit.
We used a local-ish installer, E-motion Energy, based in Stirling, but they have branches in Birmingham and Belfast and possibly elsewhere. I'd recommend anyone interested at least to try them, as they seemed to be keen and were not out of line on cost.
It's interesting that we are now getting a steady stream of offers to install Solar PV from others getting in on the act.
Like Bob, I'm assuming/hoping the system will outlive me, so the residual value is of academic interest only.

DC voltage from a string of panels is in the range 200 -700 volts depending on no of panels and light levels.

Inverters tend to be most efficient in the 400-600 volt range.
Installation manuals tend to suggest max voltage drop of 1 volt at maximum smoke and indicate 4mm cables for my 2kw system. My max panel current is spec'd at 8 amps.

Bob

 

[RogerS]

Thanks, Bob.

 

[9fingers]

Well it has finally happened. The Solar electricity system is now installed.

A clear southfacing roof

now looks like this

And some clear wall space

Now looks much more impressive!

Since installation the weather has been pretty dull and although the system is generating some power, it is nowhere near it's full potential. I'm collecting data and once I've got a reasonable amount I can post some charts.

So far so good!

Bob

 

[RogerS]

I've always been a bit bemused how you can 'push' your volts into the grid. Surely you have to be 0.00001v higher in potential than the grid? But then if your neighbour is also 0.00001v higher, you'd need to be 0.000011v higher but then he'd not work..... :?

 

[9fingers]

The inverter monitors the grid voltage and phase and manages the infeed automatically by trying to generate at a slightly higher voltage than the local sample of the grid
In practise, it pays to arrange to consume the power (usefully, of course) yourself rather than let the grid have it.

The finances are crazy.
You get 43.5p per kwhr generated.
You get a further 3p per unit exported. However they cannot measure how much you feed into the grid so they assume 50% and also don't mind if you consume it all yourself.
So bottom line is you get 45p per unit and can potentially save the same number of units off your normal bill ie another 10-11p per unit.

I told you it was crazy! Must have been designed by a politician!!

Bob

 

[bugbear]

Im still not 100% clear on the investment though - it still feels like a long term investment with a significant number of years until you've broken even.

Surely that's what you'd expect?

BugBear

 

[bugbear]

I've always been a bit bemused how you can 'push' your volts into the grid. Surely you have to be 0.00001v higher in potential than the grid? But then if your neighbour is also 0.00001v higher, you'd need to be 0.000011v higher but then he'd not work..... :?

The same logic applies if there's more than one power station ... in the UK !

I think we can safely assume "they" have found a solution...

BugBear

 

[RogerS]

I've always been a bit bemused how you can 'push' your volts into the grid. Surely you have to be 0.00001v higher in potential than the grid? But then if your neighbour is also 0.00001v higher, you'd need to be 0.000011v higher but then he'd not work..... :?

The same logic applies if there's more than one power station ... in the UK !

I think we can safely assume "they" have found a solution...

BugBear

I know..but I wish I knew how. Can't see how Bob's inverter 'wins' over everybody else's inverter.

Interested also to learn more about the cost benefit equation/payback period.

 

[9fingers]

As far as costs and payback are concerned, I only have estimates.
The system cost £8600 and is predicted to 'earn' £900 to £1000 in a year and the FIT is indexed to RPI, and the electricity cost saving is linked to energy prices obviously.
Ironically I have just reduced the latter by changing to what I hope will be a cheaper supplier yesterday!

Bob

 

[RogerS]

So is that 'income = £900-£1000' a year PLUS saving on the electricity bill?

If so have you done any calc, Bob, on what % of electricity you might save ?

 

[9fingers]

No, that figure includes the estimated saving on the leccy bill. To maximise the saving I need to find ways of gearing my consumption to the peak generation pattern of the PV system. Ways to do this are not yet obvious but I'm thinking about it!

Whatever happens, I will still get the 45p per unit, managing to maximise the further 11p per unit is the challenge. Things like charging batteries to run the lighting at night does not make sense due to further capital outlay needed. I need to be in the workshop sawing up lots of wood in the middle of summer days I guess!

Bob

 

[bugbear]

Interested also to learn more about the cost benefit equation/payback period.

If George Monbiot's number's are right, it's currently a bonanza if you can afford the capital outlay;

http://www.guardian.co.uk/commentisfree ... NTCMP=SRCH

BugBear

 

[9fingers]

Interested also to learn more about the cost benefit equation/payback period.

If George Monbiot's number's are right, it's currently a bonanza if you can afford the capital outlay;

http://www.guardian.co.uk/commentisfree ... NTCMP=SRCH

BugBear

I don't disagree with the points made in the article at all.
I looked at the scheme with some disbelief in the beginning but when I saw that companies are establishing themselves to put up the finance and reap the FIT for themselves whilst giving the householder the right to any electricity generated, I dug deeper.

I am relatively recently retired and lucky to have a lump sum from my pension. However with (real) inflation at 5 or 6%minimum and poor rates of return from the bankers (silent W) I am slowly losing buying power that I might well need in later life. It seems a no-brainer to invest some of my lump sum in an asset that can earn me some real return.

For anyone thinking of doing the same, do it sooner rather than later. The value of the FIT for NEW sign ups will start reducing by 7% per annum from either April 2012 or sooner if the take up is greater than predicted by the 'plan'.
Once you have locked into a scheme, that installation (who ever owns it) will get payments indexed by RPI (upwards as things are at the moment) whereas FIT for new schemes will reduce.

Bob

 

[Eric The Viking]

Can't see how Bob's inverter 'wins' over everybody else's inverter.

Interested also to learn more about the cost benefit equation/payback period.

I'm grossly simplifying, but consider that most mechanical electrical generators can operate as motors too.

Mechanical force is converted into electricity, but if you take that force away, the generator becomes a motor instead, and rotates in the other direction. The point at which the nett energy transfer is zero will be a certain RPM for each genny. Go slower and it's a load, go faster and it's a generatior.

I'm not considering AC frequency, 3-phase etc. above, as it gets a lot more "interesting" than that, but that is sort-of how it works.

There was an incident around 1978 or 1979, when the then CEGB got it wrong in the middle of a hard winter's evening and brought up a power station accidentally out-of-phase with the rest of the grid. Immediately the breakers closed it became a load (the generators ran as motors), and they couldn't re-open the breakers as the current surge welded them shut. It blacked out a large part of East Anglia (I was in Lowestoft that night and remember it well), and the station concerned was badly damaged.

Cheers,

E.

 

[slimshady]

I wonder if I can put in a small'ish number of panels before the FITs change and then increase the panel count in later years.?

Alex.

 

[9fingers]

I wonder if I can put in a small'ish number of panels before the FITs change and then increase the panel count in later years.?

Alex.

I don't think this will work. The installation has to be done by an accredited installer who registers your system online and they issue a certificate that describes your system.
Additionally, you have to describe your system on the FIT application form including the power output.
Nice try!

Bob

 

[dickm]

I looked at the scheme with some disbelief in the beginning but when I saw that companies are establishing themselves to put up the finance and reap the FIT for themselves whilst giving the householder the right to any electricity generated, I dug deeper.

I am relatively recently retired and lucky to have a lump sum from my pension. However with (real) inflation at 5 or 6%minimum and poor rates of return from the bankers (silent W) I am slowly losing buying power that I might well need in later life. It seems a no-brainer to invest some of my lump sum in an asset that can earn me some real return.

For anyone thinking of doing the same, do it sooner rather than later. The value of the FIT for NEW sign ups will start reducing by 7% per annum from either April 2012 or sooner if the take up is greater than predicted by the 'plan'.
Once you have locked into a scheme, that installation (who ever owns it) will get payments indexed by RPI (upwards as things are at the moment) whereas FIT for new schemes will reduce.

Bob

Exactly the same for me, Bob. If you can tie up the cash for a few years, you should be in profit after that, and getting a useful income before.
Best if you live in the south, and have a south facing roof with a pitch of at least 45degrees. Not as good up here if you have a low pitch roof. We need a steeper pitch anyway (latitude plus 5 deg is recommended) so we don't get as much light per unit area, and the snow lies on the panels because of the low angle. Did wonder before last night whether we should think of getting our panels moved so they are mounted more steeply on frames on the roof, but thought better of it as the gales blew in!
Still waiting for our first payment from SSE, though.

 

[9fingers]

I now have generation data on line for anyone to look at and play with in excel or whatever takes your fancy.
The following is the readme file which include the ftp link and an outline of the system.
Have fun. if you get asked for a username or password then leave blank and hit return

Bob

The files in the directory SBEAM hold power generation data for my solar panel system.

The system comprises 10 x 235w Sharp solar Panels and a Sunnyboy SB2500-30-HF inverter feeding the grid.
The panel area is 16.5 square metres and faces due south at an elevation of 30 degrees.
The location is 50.98723 North, -1.47665 West in the UK.

A SunnyBeam Bluetooth logger captures a generation file around midnight GMT for the preceding day.
In addition, the total power generated that day is added to a monthly cumulative file. Each month an
additional monthly cumulative file is created and the daily detail data files are removed.
Files are in read only CSV (comma separated Variable) format which can be opened in text editors such as
notepad or spreadsheets such as MS Excel and Open Office Calc.

Daily file names are in the format yy-mm-dd.CSV and monthly file names are yyyy-mm.csv

To access the data, point your browser to ftp://86.16.36.255

I can be contacted at [email protected]