Saturday, February 6, 2010

How do solar panels perform according to solar exposure..

The Australian bureau of Meteorology provides daily solar exposure data on their web site.

This map shows the amount of energy received from the Sun in a given location.

This was very interesting stuff (well, at least for me).

I wrote a little utility to retrieve the data in a form suitable for post-processing in a spreadsheet and for use in my power tracking system .

This utility is available there. It's written in python, run it with --help as an argument to see the various options available.

One direct application, was measuring on how well the CEEG panels I have installed performed according to the amount of energy they receive from the sun.

It gave me this graph:

The black line shows the average of Export/Import. Any points above the line means the system performed better than average, any points below the line, mean they performed worse.

A clear trend shows that my system performs really well when there's a lot of sun, but rather poorly in low light conditions.

It's rather a worry, as it means they will likely perform poorly during winter.

Stay in touch!


  1. 行動養成習慣,習慣培養人格,人格影響命運........................................

  2. You assume that the trend line should go through the origin. In fact what you are seeing is that below a certain level of irradience (ie. a very dull day) the system will produce very little or no power because the output voltage from the PV modules is too low for the inverter's MPPT algorithm, and the inverter itself consumes some power. All this means that there is no reason why your line should pass through the origin.

    In fact PV modules in general become slightly more efficient at lower temperatures but basically there's a lot less sun in winter than in summer. This means that for maximum annual energy capture the angle of the PV modules is set a little lower than would be the case if insolation in winter and summer were equally important -- if you want to optimise the system for winter then you increase the angle of the PV modules or put them on a tracking mount. Some people change the angle of their PV systems for summer and winter use, which typically gets them an extra 10% or so but really there are probably better and more effective things you could do in terms of upgrades to building airtightness and insulation.