Altitude effects on PV performance [RE-wrenches]

[Antony Tersol]

<x-flowed>
according to earth.usc.edu/~slund/systems/topic2.html

179 kcal/cm2/yr insolation at "top" of atmosphere

118 kcal/cm2/yr insolation at surface

61 kcal/cm2/yr absorbed by atmosphere

half the mass of the atmosphere is below 18000 ft

assuming absorption is proportional to mass, then would expect 149 
kcal/cm2/yr at 18,000 ft,

=> 149/118 = 26% higher at 18,000 ft.

As a first approximation, assume absorption is constant thru 18,000 ft 
=> 26%/18 = 1.4% higher insolation per 1000 ft above sea level.

Since the density decreases with altitude, it is likely that the 
increase is faster at lower altitudes than at higher, so the increase 
per 1000 ft  is probably somewhat higher at lower elevations, so that 
the insolation does not increase as fast at higher altitudes.

Also, there is a paper at 
www.nature.kau.se/nhc/hmrsc4/papers/ChEA_hm4.PDF specifically about 
Tibet, but which seems to be concerned with overshadowing effects (all 
those tall mountains cast mighty big shadows)

ABSTRACT
A digital elevation model (DEM) is developed to establish a insolation 
model in central Tibet. From DEM, we can easily get follow factors: 
elevation, slope, and aspect. On the basis of these terrain
characteristics and solar data for various dates, we established a 
insolation model from which insolation maps were produced showing areas 
overshadowed at different times of the year.

-----Original Message-----
From: Jeff Oldham [mailto:starpower4u at juno.com]
Sent: Thursday, February 27, 2003 4:49 PM
To: RE-wrenches at topica.com
Subject: Altitude effects on PV performance [RE-wrenches]


Anyone know a basic formula or web site that addresses altitude effects
on output? I can't seem to find anything, I have a project at 12k' in
Tibet and need some ball park numbers for now (we'll take on site
readings later). I've had Everest climbing teams I've outfitted claim
very noticable increase at 15k, but these guys are deprived of oxygen
and can't think straight!

thanks


Jeff Oldham

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
This email was sent to: michael_welch at sbcglobal.net

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

TOPICA - Start your own email discussion group. FREE!
http://www.topica.com/partner/tag02/create/index2.html
==^================================================================

</x-flowed>