Solar Panels ?

House fitted with 4KW of solar panels
In brilliant sunshine, such as we have had over the past couple of days, what prevents solar panels producing the full permitted 4KW. Down to 2KW now.
A few days earlier, when not as hot, solar panels were producing 3.73KW.
Kindest regards,
Jim G
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Angle of the sun (time of day).
Dust on the panels (my car seems to have a thick layer of yellow pollen or sand which has built up over a few hot days of non-use).
Of course, there's also the possibility of a fault.
Also, it's light, not heat, which generates electricity.
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Andrew Gabriel
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On 25/05/2012 00:20, Andrew Gabriel wrote:

And crucially heat decreases their efficiency although not normally by factors of two. You should measure peak output when the sun is aligned with the axis of your collectors (roughly same time each day).
Then you have a comparable number. It is possible you have a dodgy panel that is misbehaving under thermal stress or they are covered in pollen and dust at the moment.
Any partial shading of the array severely compromises output.
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Martin Brown
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On 24/05/2012 23:42 the_constructor wrote:

Temperature. The hotter they get, the less efficient they are.
I got peaks of over 4kW out of our 3.99kW system a few weeks ago when the sky was clear but the temperature low. On similarly bright but warm days now, the peaks are around 3kW.
Overall, with the longer days, I'm getting in excess of 25kWh each day.
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F




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F wrote:

Oh and the other thing is the SPIV factor.
spiv stands for "Solar Power 'Investment' Vendor".
where an average of 100 watts becomes 'up to 4KW' etc. etc.
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Is the right answer. Panels have power TC of about -0.4 to 0.5% per degree C, and the panels will get hot, maybe 45-50 C hence, on a hot day, peak output can be 20-25% below peak output on a cool day wit sunny spells.
There's even a specification for it, NOCT - nominal operating cell temperature.

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the_constructor wrote:

lack of pixie dusrt.

sun angle.
And lack of cloud cover. They work on sunlight, not air temperature . You may have noticed they produce nothing at night.
Even when its a warm one.

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In message

Harry - do you understand what makes the sky blue?
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geoff

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On 27/05/2012 12:57, geoff wrote:

And he is factually wrong to boot. To get absolutely maximum output from a solar array requires a clear blue sky path to the sun and the largest amount of thin white cirrus cloud everywhere else. Enough to scatter light that was destined to hit somewhere else onto your PV.
White clouds are *brighter* than blue sky in every universe but Harry's.
If you have the option since mirrors are cheap and solar PV device expensive a 120 degree mirror assembly \_/ either side of the active cells gives you about twice the output (but not flat plate). Tends to get the PV cells a bit too warm and makes clear epoxy go yellow though.
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Its not a stupid question, it was a valid question relating to your stupid statement and you obviopusly didn't know the answer before you made it
you're a prize bellend ...
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