Solar shadowing – reducing the losses is like you partially unblocking a water pipe. Partial solar shadowing reduces your losses proportionally. Except in extreme clouding, however, solar modules produce some output. During daylight it’s rare for you to have none.
Solar Shadowing – reducing the losses – bypass diodes partially assist
Most 12-volt solar modules have 60 cells. Each cell is connected in a string. A totally shadowed cell produces no current. Blocking one affects all.
Basic modules supply the current of the least producing cell. To limit this, good quality modules have three strings. Each string has 20 cells. Furthermore, each string has a so-called ‘diode’. If activated, it carries current from unshaded strings. This assists, but is not a perfect solution. With only one cell shaded, output is slashed one-third. Furthermore, diodes are not reliable. One diode failing will prevent associated strings working.
A typical bypass diode. Pic: Original source unknown.
The ideal is a diode across each cell. Doing so, however, is costly. Worse, diodes fail more often than cells. Reliability is reduced.
Solar Shadowing – reducing the losses – the more effective ways
In basic systems, the lowest cell output limits your overall output. With multiple modules, shadowing one limits output of all. The loss is confined to the area shaded.
Power optimisers attach to existing solar modules. They maximise energy. Power optimisers also eliminate power mismatch. They decrease shadowing losses. Such optimisers can be built into solar modules. Or fitted separately. The concept works well.
Pic: Enphase micro-inverter (power optimiser)
Solar Shadowing – reducing the losses
Our books cover shadowing issues in depth. Solar That Really Works! is for cabins and RVs. Solar Success is for homes and properties. Caravan & Motorhome Electrics covers RV solar and general electrics. All are available in digital or print form. Moreover, our books also cover legal issues. Furthermore, you can download our digital versions right now. Click on the books’ title (above). Print versions are stocked by all Jaycar stores. You can also buy them (from anywhere) from booktopia.com.au/