Install PV panels flat or at 30 degrees on roof ?

[2ndBillericay]

We are looking in to placing some 180w to 250w panels on our scout hall roof and have a limited space flat roof. I was wondering what the general feeling was regarding the mounting angle.

If we use the ConSole mounts we can have a panel every 2.5m (1m for the Console & 1.5m gap to stop shading) as opposed to spending the money and buying bigger pannels and flat (little slope to drain) mounting the panels on a frame.

i think we will loose about 10% from having a flat installation but we will get more units on the roof for our money.

thanks

2nd Billericay
the solar scouts !!!

[rogeriko]

Go to http://sunbird.jrc.it/pvgis/apps/pvest.php  and double click on your location and you will see panels should be installed at 37 degrees. That means you will need about 2 meters in between to avoid shading.

[alank]

Have a look at the Mastervolt PV System Calculator - it's a free download from:

http://www.mastervolt.com/view_product.php?lang=2&section=solar_grid&prggr_id=1159&prg_id=1102&pro_id=5920

You can put various values into the spreadsheet and see how output is affected.

For best results you need the panels to be free of shading of any kind, south facing and at an angle of about 30 to 40 deg.

The angle will also keep the panels cleaner.

[JohnS]

If you have the panels at an angle, you will need planning permission.  If they are flat and not more that 200mm above the roof and you satisfy the standard requirements, you should not need permission.

[rogeriko]

If you install the panels flat you will have virtually zero output when the sun is low because the surface acts like a mirror and the suns rays do not penetrate the glass. I have tilted up the panels on 3 houses here in greece that were installed flat because of no output whatsoever in the winter months even on sunny days (about 20 watts from a 220 watt panel) After tilting up 30 degrees full power!!

These panels produced nothing during the winter

[2ndBillericay]

Thanks for the info Guys, the speed was amazing.
If i have used the sites correctly i get the following data :-

Month   Irradiation at inclination: (KWh/m2/day) 60% efficiency Area    Generation Revenue   
   0 deg.   25 deg.   Difference   0 deg.   25 deg.   19.5   0 deg.   25 deg.
Jan   0.708   1.101   64%                0.4248   0.6606   19.5    £3.40     £5.28
Feb   1.321   1.846   72%                0.7926   1.1076   19.5    £6.34     £8.86
Mar   2.245   2.725   82%                1.347   1.635   19.5    £10.77     £13.07
Apr   3.657   4.097   89%                2.1942   2.4582   19.5    £17.54     £19.65
May   4.524   4.691   96%                2.7144   2.8146   19.5    £21.70     £22.50
Jun   4.833   4.862   99%                2.8998   2.9172   19.5    £23.18     £23.32
Jul   4.841   4.959   98%                2.9046   2.9754   19.5    £23.22     £23.79
Aug   4.146   4.507   92%                2.4876   2.7042   19.5    £19.89     £21.62
Sep   2.835   3.394   84%                1.701   2.0364   19.5    £13.60     £16.28
Oct   1.711   2.313   74%                1.0266   1.3878   19.5    £8.21     £11.10
Nov   0.878   1.334   66%                0.5268   0.8004   19.5    £4.21     £6.40
Dec   0.511   0.789   65%                0.3066   0.4734   19.5    £2.45     £3.78
Year   32.21   36.618   88%                9.326   21.9708       £154.51     £175.66

this seems wrong against the data from the Segen calculator. !! See below

Estimated Annual Energy: 1,700 kWh
Note: The figures below are based on the proposed feed-in tariff which applies from April 2010.
Typical Sale Price:          £0.10/kWh The typical price that your electricity company charge you for each kWh you buy.
Proposed Feed-in Tariff:  £0.413/kWh The price you get for every kWh you generate.
Guaranteed Buy Price:    £0.03/kWh The price your electricity company pay you for every kWh you export.
Percentage Own Usage:  0 25 50 75 100% How much of the generated energy you expect to use yourself.
Annual Saving:              £172.13 How much your annual electricity bill should reduce by.
Annual Income:             £714.85 How much each year you will earn.
Net Annual Revenue:     £886.98 Your combined annual saving and income.

[billi]

hi

Schletter provides a fixing idea for flat roofs an panel angles from 5-7 °

http://www.schletter.de/en/flat-roof/35-trapezblech-mit-pfetten.html

There are quite a few people in Germany  that chosen  flat installation  instead of angle the PV on flat roofs

Dirt and snow are a problem and panels with no frame or a neap frame are preferred

Here i searched for  pv owners ( click on owners to find out more ) with close to 0 angle

http://sonnenertrag.eu/suche.php?month=2&month1=2&year=2010&year1=2010&datenimport=alle&country=1&bundesland=&postcode=&city=&kfz=&district=&inbetriebnahme=&leistung=&leistung2=&neigung=1&neigung2=10&ausrichtung=&ausrichtung2=&nachfuehrung=3&hersteller=&modultyp=&modulart=&wechselrichter=&kosten=&kosten2=&extd_filter=y&search=search


billi

[djh]

If you fix them flat, you will need to clean them often