PV Output

Performance of your solar system

A solar power system is one of the only reliable ways to decrease your power bill and reliance on the national grid but the science involved in this money saving technology can be tricky to understand, so here is a breakdown of how your system performs.

How does my solar power system get its name?

Solar power systems are given a kilowatt name such as 1.5kW or 3kW, so where does this number come from and what does it mean? A system gets its number name from the generating potential of the solar panels. This generating potential is the maximum performance of the system and is reached when under ideal conditions. These conditions are replicated in our laboratory under our ‘Standard Test Conditions.’

What are the Standard Test Conditions?

The conditions in the test are;

1. Cell temperature of 25°C

2. Light measurement of 1000W/m²

3. Air mass of AM1.5 (this refers to the solar spectrum after the solar radiation has travelled through the atmosphere, this figure is universal for standard testing)

What if these conditions don’t occur all the time and at once?

These conditions will rarely all occur simultaneously but that doesn’t mean your system won’t be performing at a high rate. Our systems aren’t designed to only perform in “ideal” conditions, but in the tough Australian weather. Don’t be alarmed, these “Standard Conditions” are replicated to discover the systems generating potential, just because these conditions won’t occur on a daily basis doesn’t mean you won’t be saving money!

What elements can cause my solar power performance to be reduced?

There are a few certain elements that can prevent your systems operating at its peak level. These include shading, orientation, pitch and dust.

Shading

Shading is the single biggest cause of power loss in a solar system.  As all solar systems are built up of multiple solar panels connected ‘in series’.  If a single panel or part of a panel is shaded, it affects the whole array (all panels together) much more then the degree of shading.  Shade cast on a corner of one panel may drop the output of the entire array by 50% or more.  It is important to remove/minimize ANY shading on a solar system to optimize power output.

Orientation

Facing ‘true north’ is optimal as the sun spends more hours of the day/year in the north of a vertical axis in Australia.  Exceptions are in the first & last hours of the day between the equinoxes in the summer ½ of the year.  Panel placement away from north reduces yearly output by around 14% in the eastern/western directions & up to 25% in a southern direction, with a continuum in between.  Due east or west have the same degree of loss, so if this were the best orientation at your residence, other factors such as shading, aesthetics or cable run length would be taken into consideration.

Pitch

Optimal pitch for maximum solar collection is 900° perpendicular to the sun, so dual axis tracking which follows the sun all day can increase solar performance by approximately 30%, but is very expensive & takes a lot of space.  In a fixed array, the optimal pitch angle is equal to the latitude of your location, thus around Brisbane, (lat 270°), the common roof pitch of 220°-280° is almost perfect.  Sydney’s latitude is 340° & Melbourne’s latitude is 370°.  Within a few degrees of latitude makes minimal difference.  A totally flat array loses 9% compared to an optimally pitched array.  The biggest problems with a flat array are dust & debris accumulation & excess heat due to reduced ventilation under the array.

Dust & Debris

A pitched array will be somewhat cleaned after heavy rain & winds.  Small amounts of dust block light therefore reduce solar performance.  Leaves & bird/bat droppings do the same.

How do I measure the performance of my solar power system?

There is a calculation to see what your system will perform at but we have made it easier for you, simply view the table below to see a break down of the average daily production figure from an optimally placed system, which is one that is facing north, on the right pitch with no shading.

This information can also be downloaded below

download: Solar PV Performance Sheet (119.01KB) added: 29/04/2011 clicks: 307 description: This information sheet outlines the performace of Solar PV in general

download: CEC Solar PV Consumer Guide (694.24KB) added: 09/05/2011 clicks: 243 description: For more information about Solar PV and output download this handy guide today