Martin Brown wrote:
On 25/05/2012 13:34, The Natural Philosopher wrote:
Martin Brown wrote:
On 25/05/2012 11:09, harry wrote:
On May 25, 8:22 am, Martin
wrote:

Any partial shading of the array severely compromises output.

The inclination of the PV panels deemed best is for maximum annual
production. If they were any steeper, ey might work better in Winter
but Summer /overall production would be reduced.

Partly true. The optimum angle is a function mostly of azimuth and
latitude with a tiny correction for ambient summer temperatures. The
array in the UK is better off pointed to get maximum capture cross
section in early May rather than mid June.

Pure S facing at mid summer suns elevation is 113.5-latitude
Pure S facing at mid winter suns elevation is 66.5-latitude

Take UK average latitude as 53.5 degrees and you get
summer elevation 60 degrees (30 degree pitched roof)
winter elevation 13 degrees (77 degree pitched roof aka leaning wall!)

In practice something around 40+/-5 degrees is close enough.

in reality you are nest to optimise for summer sun as they produce so
little in winter you might as well not have them at all.

Well really you might as well not have them, at all from a UK
perspective anyway...

On that at least we are agreed. If the price eventually falls enough

It wont.

then they will become truly cost effective

Not even then.

but that will happen first in
sunnier equatorial and sub tropical climates. We in the UK and in
Germany for that matter live to far north to be worthwhile.

Solar panels or better small wind turbines make sense for some remote
off grid applications where modest power is required. Please go round
the bend signs in the UK are a notable failure since they are all
completely stone dead on frosty winter mornings (when they are needed).


They are all completely dead here even when powered by windmills as well.

They don't work. Last year in mid summer someone went straight on:


No intermittent renweable 'works'

http://www.gazettelive.co.uk/news/te...4229-26955401/


The bend sign was almost certainly working properly at the time.

Geometrical losses scale as cos(angle) which roughly tranlates to
- (theta^2/66) % where theta is the angle between the sun and the
normal to the PV array. Eight degrees away from optimal you lose ~1%.
It isn't worth losing any sleep over minor alignment errors.

The inclination of solar thermal panels deemed best is that for
maximum Winter production.
Because any surplus in Summer cannot be exported as with electricity.

The optimum is when it can provide all required domestic hot water for
the largest proportion of the time. Steeper than for PV but by no
means as near to vertical as optimum for winter would imply. Somewhere
between 45 and 60 degrees based on a quick back of the envelope job.

The FIT distortion for PV means that people do not install SHW anyway.

However I have seen them (PV) performing at max with sun quite low in
the sky when the sky has been very clear. (Eg, after heavy rain has
cleared all the atmospheric moisture.)

A PV on a fairly steep roof in mid winter on a clear day the cold
compensates somewhat for the low solar angle, but can do nothing at
all about the incredibly short period of useful daylight in winter.

We are too far north for solar to be anything other than a novelty toy
and tax dodge due to incompetent government market distorting FITs.

Well you got that bit right. Its all about Germany creating solar panel
jobs. That's all going tits up now anyway as they solar companies are
going bust and being undercut by cheap Chinese imports.

Same with the immense amount of oilseed rape planted this year which
seems to be a result of the German biofuels scam driving prices up.

yup. Our farmer chuckles all the way to the bank.
His gain, your loss in terms of increased wheat prices.



I bet you see accusations of dumping and an EU trade barrier erected
shortly. Or a scrapping of renewables in Germany.

I bet on the former. YMMV

Depends if the Euro survives the summer.
The Germans have made a total utter balls up of everything they have got
politically involved in since forever.




Mind you the new Germann minister of power is a big fat balding ex
lawyer.

http://www.world-nuclear-news.org/up...12_250x167.jpg


So we are bound to get really clueful policy right?

More likely some very complicated laws that keep lawyers in business

well, yes.


--
To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
that they know how little is really possible -
and how hard it is to achieve it.