יום ראשון, 3 ביולי 2011

Practical Solar PV charts for installations

I've been asked a lot about how much degradation one should expect from having the wrong azimuth on a certain roof. also the inclination has an effect. I'll try to bring here the basic types I see common.

A roofs facing south are rare, but until we develop a tracking system that can use a standard roof tile installation, this is pretty much the degradation expected from a 22° inclination / Azimuth :


This Chart is only effecting 22° inclination roofs local at Israel. additional charts of different inclinations are located here.
The following interactive chart also shows expected degradation due to two variables: azimuth and 0°-25° inclination (geographical location Tel Aviv):

(to view a Google interactive chart you must log in your Google account)

When designing flat roof arrays, the row distance must allow the sunlight to be available for all of the array from 08:00-15:00 in winter at least and 07:30-17:00 in summer to enjoy the peak power of the array.
if the area doesn't allow it use these tips:

1. The build of the panel has some faults. when partially shadowed it may produce no energy at all. it seems that if it is shadowed on it's short side (for instance, a panel is standing) it will not generate energy. while if it is similarly shadowed on it's long side (a panel is lying) it will produce up to 66% energy even while shadowed.
Flat Panel with shadows drawing

2. it is smart to use technological improvements such as Tigo maximizer units but they are not cheap. sadly a lot of consumers think cheap and not think profitable, which can generate a lot of untapped energy. a large scale facility that isn't shadowed will think "why do I need this?" and forget about partial clouding or bird droppings that when one panel is down, the whole array goes down.

3. for flat roof installations, the following chart provides distances based on inclination of the panels (local iseael) and should provide maximum peak power at minimum distances, larger will be more effective:


(again, one must be logged in a Google account in order to view the interactive chart)
Be sure to check out GreenTops site for more info