Solar Panels - Non Southerly Roof

robbo100

Hi there,

I have been thinking about investing in PV cells on my roof for a while, but my main roof does not face south, in fact it points 70 degrees off (facing 250 degrees to be precise).

Is there an equation I can use to calculate how much of a reduction in efficiency this will cause me if I were to get any PVs, or can anyone give me an estimate based upon their own system's efficiency? Or is it just not worth it?

Thanks

Robbo100

johntheexpat

The inclination of the roof is important too.

By 250 degrees I assume that is almost west.  So, copying from a little table I have:

Assume 100% is gained from a 30 degree inclined roof, pointing due South.

For a roof pointing due West:

Inclination of roof  (efficiency % )

0  (91)
16 (89)
30 (84)
45 (78)
60 (70)
90 (50)

From the same place (When my scanner works I'll copy the whole thing and post it)

For a nominal 3KW max installation, (or 3KWc as the French say) they would expect an installation in the North, so Starsbourg Paris Caen etc to produce between 2700 and 2900 KWh per year if it is facing due south with an inclination of 30 degress.

So, if you had a west facing roof with an inclination of 45 degress in the North of France/South of England, you could expect to generate 78% of 2800 KWh which is about 2200KWh

IronGiant

Wow, I was going to guess   

My worry is that he won't get any sun shining directly on the panels until the sun is (say) 30% above the horizon, and he won't get full on sun until late afternoon.

I'd have guesstimated only 30-50% of a south facing installation.

Hope I'm wrong

robbo100

Thanks chaps.

I have to say, that looks to be much higher efficiency that I expected!

Maybe it might be worth doing after all!

Robbo100

IronGiant

I'll try and take some notes of during the day input.