Thursday, November 26, 2009

Said and done - the trees are gone!

After a full week of unshadowed operation is has becoome clear that solar energy is not always as "green" as everybody thinks. Shadow of any kind - even a tiny patch reduces the efficiency so dramatically that every effort to get the panel surface shadow-free is justified.

The reason for that effect is the serialization of cells within a module and the serialization of modules to form a "string" with sufficient input voltage for the inverter. A single solar P-N-element (the "cell") features typically only 0,5 Volts. It takes 60 or so cells to form a "module" creating a typical open-circuit voltage of 30 volts. 12-15 serially connected modules then create a string with 360 to 450 volts input at the inverter. Shadowing only one module or even only one cell within "pulls down" the whole string unless the current is lead through the bypass diodes, which means that the bypassed module is "cut out" effectively for the moment.

In that sense "trees" can be the natural enemy of  the solar entrepreneur.
In my case 4 massive 12-15m pine trees had to be victimized.

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