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PV Solar Panels
 Started by  October
 14 Oct 2009, 11:10 AM

Knowing very little about PV panels, I have been browsing the web and reading suppliers' brochures. Confusing - so I would like to ask
1. Are the PV panels or cells all made by the same one or two manufacturers ?
2. Is there anywhere a "best buy" report on PV panels ?
3. All the literature seem to refer to "near perfect" installations - eg south facing roofs at an angle equal to the latitude of the property. (Although the Marley brochure states almost any declination between East and West is satisfactory.)
Can anybody describe how they get on with a "less than perfect installation".
Mike O.
Even if you plan to DIY my advice would be to talk to some local installers - say three - who'll be able to survey your house and discuss sizing and costs. If you look at the yougen website
you can search for reccomended installers in your area.
PV panels are made by many different manufacturers including global giants like Sharp, Kyocera and BP although they may be badged as one product but made by someone else. There are several different types of PV panels; moncrystalline, polycrystalline and thin film (there may be others) and there are different efficiencies and of course costs. Have a look again at the yougen website suggested above for a more detailed explanation of the different technologies. I don't know of a best but report on PV. It would be extremely difficult to compare different PV technologies and system sizes - its not like doing a best buy of washing machines or cars! Some PV systems can be sized to feed surplus power into the grid while smaller systems may simply charge batteries.
Regarding the less than perfect installation have a search on the green building forum for information on tracker arrays which follow the sun and greatly imrove efficiency even in less than perfect settings.
If you can get the price right why not look at PVT, combined theremal and PV. I saw some advertised at about 7k per kWP installed, but when I looked into it this was only for larger systems.
It is meant to increase solar PV yield as the hotter conventional PV gets the lower its efficiency.
If you do DIY Julian, are you still able to claim government subsidies either now or in the future? I'm particularly thinking of top-up tarrifs for selling back to the grid.
I am not an expert. As far as I understand that they would apply but the government's Clear Skies/LCBP/MCS scheme grants (c. 2,500 before 1.4.10) won't.
No grant is available for self installed systems, and there is a question over whether the feed in tariffs apply unless the system is MCS approved. Although I might have got that wrong.
Angle of inclination.jpg (170Kb)  
I've got a table, which I'll try to attach to this post, which is useful. It shows that due South, with the panels at an angle of 30-40' is 100%. If you're facing SE or SW this drops to 96%. If you're due East or West, this angle is only 85%, but you can increase the efficiency to 90% by dropping to horizontal.
We've just had our system (SW) installed, and we chose the installer who had a wide experience of different panels and inverters, and was able to give us a considered view as to the best combination for our circumstances. We have Mitsubishi panels and Fronius inverter, but his quote for the SE face used Sharp panels. For situations with a lot of sun (like S facing in Cornwall) in would have gone for Sanyo panels.
With 2500 grants available only until March, and the FIT coming in in April, there is a great window of opportunity to buy now, when you get both benefits. PV installers are expecting a big rush in first quarter of 2010!
You might have a look at It's organised by National Energy Foundation, and has information about homes where people have retro-fitted various energy saving devices. All the homes are open to the public on occasions, and so any PV owners here would probably be prepared to answer specific questions about their results.
PS to earlier post - for PV it is worth being a bit flatter than your latitude, to maximise the summer results, although this worsens your winter figures - but they are less anyway. For SHW the converse is true, raising 45 to 50 in the winter is more useful than raising 60 to 65 in the summer.
@ October:
Check the www. for "top 50 solar". There you'll find hundreds of suppliers, manufacturers and installers.
Try the different flag symbols (English, German, ect...) to check the international prices. The smaller the market the more expensive they're.
There is a good magazine called "sun, wind&energy", they're publishing regularly a "PV map", showing manufacturers world wide. There are hundreds , not only the two you've heard about.
Re Angle of inclination
I cannot see how shallower angles than lattitude can be more efficient than lattitude angle
Panels mounted at the lattitude angle will only see the sun shines at right angles once a year and all the rest of the time it will be shining at an angle to the panel reducing its effective capture area
It must be the case that a panel mounted at an angle steeper than the lattitude angle will operate better
Typical modern roof angles of 30 or 35 give lower capture results
solar pv and solar thermal are equally influenced by angles
Re angles. The chart I gave was provided in good faith - I didn't devise it. Having run the disclaimer, you're right that at any angle the panel is only normal to the sun once a year. By changing the angle, we're trying to be as close as possible, at the most important time. For instance, so-called Dutch greenhouses have the sides at about 10 off the vertical, so that with the low winter sun they are closer to right angles (getting more heat in) and with a hot summer sun they are further away (reducing over-heating). But you'd need to talk to a mathematician to fully understand the sums. That's why we do different things for SHW and PV - for SHW you want to maximise the winter performance, knowing that a reduction in the summer performance isn't critical. With PV you want to maximise the summer performance, since you can store (or sell) the excess electricity.
Having said all of the above, if you're on a roof it is hardly worthwhile spending any money on changing the angle - the increase in performance won't be critical. It's only worth thinking about if you're actually building a frame to hold the panel on a flat roof, or the ground.
There is a function available on the i-pod which will tell you more about the correct angle then any chat in the www
See here

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