PV Alignment

PV Alignment
   

Tilt angle

There are many experts giving quite different optimum tilt angles. It seems that the optimum tilt angle is your latitude minus 10 degrees.

Orientation

A roof does not always point conveniently north. So what is the effect of pointing other directions?

The website PVWatts Calculator give the answers for any latitude or direction for a PV cell mounted at an angle of 20 deg to horizontal. You enter your location and azimuth (compass bearing in deg) with other info, and it displays the power generated.

The tables below give the solar radiation and power generated for Sydney, Aust.

The solar radiation is measured on a horizontal flat plate

Effect of orientation on efficiency. This does not allow for the variation in power prices during the day.

The readings on this graaph are slightly different to teh tables below.

 

 




Solar radiation on 1 sq M 

kWh/day

Electricity from 1 Sq M

kWh/Day

  N E S W   N E S W
Jan 6.49 6.28 6.15 6.38 Jan 4.9 4.8 4.7 4.9
Feb 5.79 5.4 4.99 5.42 Feb 4.4 4.1 3.8 4.1
Mar 5.38 4.62 3.95 4.75 Mar 4.1 3.5 3.0 3.6
Apr 4.51 3.61 2.68 3.64 Apr 3.4 2.8 2.0 2.8
May 3.41 2.56 1.72 2.59 May 2.7 2.0 1.3 2.0
Jun 2.94 2.12 1.26 2.09 Jun 2.4 1.7 0.9 1.7
Jul 3.46 2.47 1.49 2.49 Jul 2.8 2.0 1.1 2.0
Aug 4.55 3.43 2.31 3.48 Aug 3.6 2.7 1.7 2.7
Sep 5.29 4.42 3.54 4.43 Sep 4.2 3.5 2.8 3.5
Oct 6.01 5.45 4.82 5.41 Oct 4.7 4.3 3.8 4.3
Nov 6.01 5.82 5.48 5.67 Nov 4.7 4.5 4.3 4.4
Dec 6.19 6.02 6.02 6.21 Dec 4.8 4.6 4.7 4.8

Points of interest are:

Electricity production from East and West PVs are very similar. With electricity prices double in the afternoon it is smarter to face cells to the west.

PV cells facing south: 

in Jan they produce 96% of PVs facing North.

In Jun  it is 37% of  PVs facing North.

So if PVs are cheap and electricity expensive, it may make sense to face South.

  c/kWh
Shoulder 7 AM-3 & 9-10 PM 25
Peak 3-9 PM 48
Off peak 10 PM-7 AM 12
Hot water  when there is xs 10

These times vary between suppliers