It could even be lower than that given that about 1 in 10 of them are
typically dead in the water at any one time and a particularly bad
installation near me it is more like 2 out of 3 dead most days.
Part of the problem is that when the wind does blow power generated
scales as the cube of the windspeed up to some limit when they are
forced to feather the blades for their own protection. Unless they are
installed in pretty windy locations their capacity is somewhat wasted.
The catch is that the best places often lack grid infrastructure to
carry the generated electricity away to where it is needed. Result is
you can have wind farms paid *not* to feed their power to the grid!
I have to agree.
The FIT system *is* crazy and being milked for all it is worth to farm
the grants to make money rather than the wind to make electricity.
No one says they "can't" generate. They simply do not regularly generate
to the levels claimed when they are installed. And of course no wind or
too much wind and they don't generate at all. It is very unlikely even
in the current weather that all windmills will be experiencing the same
wind levels across the UK. E.G. our max wind speed last night was 55 mph
but mostly sat around 10-20
I expect they get paid for installed capacity rather than supply. I have
seen "green" solar energy panels on the roof of a new "green" eco
building in woodland where they only get sun on them at all in high
summer and parts are always in shade (which ruins efficiency).
We have loads of those active "please go around this dangerous bend"
signs up here in North Yorkshire. They don't make a bit of difference!
Unfortunately they are all dead in the water on frosty winter mornings
and even when they are working it doesn't stop morons from doing this:
This happened in mid summer when the active signage *was* working.
To be fair it is a fairly tight 40mph bend after a long straight.
If you read the article, it actually says that pointing the panels West
reduces the totsal output, but increases it in the evening, when the
householder turns on the air conditioning, so that more of the power
generated is consumed inside the house, and less is exported.
It depends which way the ground is sloping.
If there is high ground to the East, sunrise is later.
Also sea air is often hazy.
As they are way to the South of us, the panels will be nearly flat so 5%
will be about right.
In the UK 35 degrees is optimum. You would loose a lot more by going away
If your aim is to maximise subsidy, rather than to produce the maximum
output when it is likely to be needed most, then 35 degrees is a good
compromise angle for fixed panels for much of the UK. It is not the
optimum angle, which varies from day to day and upon actual location; 35
degrees is near enough the optimum angle for May and July in Brighton or
for June in Aberdeen. For December, the optimum angle is around 80
degrees in Aberdeen and 74 degrees in Brighton.
Most people put them on the roof so have no option as to
Surprisingly in the UK worse possible option (Eor W facing and vertical)
gives a reduction of around 50% if there are no other adverse factors.
The OP was from Texas ISTR so the azimuth would have less importance than
with us up North
On the equator, the panels would simply be horizontal.
I would have thought that North facing would be the worst possible
option in the UK. However, assuming the panels are facing somewhere
between SE and SW, then vertical would give near best output in mid
winter in Aberdeen. It is only bad if the aim is maximising FIT income.
That is only optimal at the equinoxes. At other times, the optimal angle
varies from +24 to -24 degrees.
The optimal solution is a two-axis tracking system. Compared to that, in
the UK, the annual energy that can be collected by a fixed panel is up
to 70%. Changing the angle twice a year will collect an additional 4%
but more changes only bring marginal benefits: about a further 0.5% for
changing four times a year. All figures are approximate.
But if the ability to adjust is built-in and automated, what could be
achieved? That is, tracking through the day.
(Yes, I do realise this is not exactly practical when the panels are
stuck directly to a roof. :-) )
<fx looks up>
Well if fixed gives 70%, and tracking gives 100%... I'll leave that as
an exercise for the student :)
Of course if you do track you'll either have to move the array as one
unit, or have shading problems.
The original paper by chance shows a 2% better result for the period
examined but the statistics on a small sample are well within the noise.
If you count the appalling statistics that the original paper used as
"evidence". The greenwash blog postings have become ever more divorced
from reality as this story has propagated away from Austin Texas.
Worth going back to the horse's mouth...
Is a reasonable dissection of these lemmings jumping off cliffs from the
original authors of the paper that started this lunacy.
The thing it does say is that from a payback perspective if you live at
a hot low latitude where aircon in late afternoon affects the dynamic
electricity pricing then it may be cost effective to point the array
westwards (*and* also alter the slope angle). I reckon based on their
numbers pointing it WSW to SW should optimise returns.
The trouble is saying they should face south doesn't take weather into
If you frequently get early morning mist/fog you may well be better off
facing West where the mist/fog will have burnt off.
You really need to fit a tracker if you want the most output.
PS, just to start a debate, as panels produce less as they get hot
should they be water cooled by spraying water on them?
I have just noticed something else *VERY* odd about their graphs. The
houses with West facing solar panels seem to use more electricity
overall than the ones with South facing panels. eg.
Midnight 1.5kW vs 2kW
8pm 2.5kW vs 3.2kW
This suggests that the study is extremely badly executed with unmatched
samples and its conclusions such as they are completely invalid.
Incidentally if the west facing PV was doing what they claimed then it
would move the cross over point from 16:30 to a later time. If anything
it looks to me like it moves earlier! So I reckon most of their claims
are complete and utter bollocks.
Perhaps SW or maybe even WSW to allow for local morning fog but the
original article also fails to mention that in doing this you also have
to make the elevation angle lower to optimise the pointing.
There are some hybrid ones that have a heat exchanger on the back of the
solar panel to make hot water. So far their complexity and weight has
made them less appealing since there is only so much hot water you can
use. I have seen bright cold UK winters days generate an impressive
amount of power considering the low elevation of the sun - quite close
to the theoretical limit allowed by the geometry. By comparison their
efficiency is much worse when the array is baking at 70C in mid summer.
In very hot climates just having a second skin over the roof with an air
gap in between slows heat ingress noticeably. Even more so if the back
side of the array has a mirror finish.
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