>> By developing a new antireflective coating that boosts
>> the amount of sunlight captured by solar panels and allows those
>> panels to absorb the entire solar spectrum from nearly any angle

> I don't get it.  I thought the wavelength sensitivity of solar panels
> was due to the physics of the junction; not surface reflectivity
> issues.  "Absorbing the entire solar spectrum" isn't a good thing if
> all it does it make your solar cell hot...  (unless you're doing solar
> heating.)

As in most things, you win and lose with an "advance".

Reflection inside solar cells is a cause of loss of efficiency and the rear 
layer of modern cells has had a fair amount of effort put into making it 
antireflective.

THEN, as you note, there is what you do with that spectrum. Typical single 
junction solar cells have poor to very poor performance in the IR region and 
filtering out IR will generally reduce performance due to lowered cell 
temperatures *. Si PV cells have a marked negative temperature coefficient 
for power (or voltage at given voltage or voltage at ...). I have found that 
in practice cooling a panel by simply running the thinnest possible 
continuous film of water across water across the outer glass typically 
produces in excess of 10% more output. If you have easy access to unlimited 
cooling water or can cool panels well by other means then this can be a 
simple means of increasing output usefully.

If anyone knows of a good cheap easy to use (bakes apple pie as well would 
help) IR filter material I'd be plased to hear. Same goes for UV although 
plain PC (polycarbonate) does a fair job there. The trouble with absorbing 
UV is that the energy involved has large energy quanta that tend to knock 
the stuffing out of many materials. Anything with carbon-carbon bonds tends 
to fall apart reasonably rapidly - especially in NZ which has amongst the 
highest UV levels of any country. Silicon-silicon bonds fare better due to 
highe rbond energies, which is why silicon rubbers have markedly superior UV 
performance compared to epoxies in solar encapsulant use.


   Russell McMahon
* Dual and triple junction cells use different semiconductor materials in 
each junction - Si + arcanery** , to make use of spectrum not well used by 
basic Si cells. The rather expensive triple junction cells really only come 
into their own in above astmosphere satellite installations where the 
increased energy at spectral extremes due to lack of atmospheric filtering 
can be well utilised.

** Various mixes of Gallium arsenide, Germanium, Indium Phosphide, Indium 
Gallium Arsenide, Indium Gallium phosphide, ... !!! (Even worse than LED 
combinations :-) ).



-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist