Halving the size of solar cells increases their efficiency
Fraunhofer researchers from Halle came up with this simple and effective trick in 2014. A module with 144 half cells supplied five percent more current than a module with 72 full cells .
The development of solar cells and modules continues to progress and leads to ever higher efficiencies. Such a development does not always make it into mass production, often cost reasons are the reason for the end. But half cells have now made the leap and are now offered by several manufacturers.
When processed into modules, solar cells are wired, covered with a glass pane and the edges are finally sealed. A lot of power is lost due to optical and electrical losses. Because of the contact, small areas are no longer reached by the sun, and there are relatively large electrical resistances inside the relatively large cells. In addition, part of the electrical energy is converted into thermal energy (heat) when current flows through a conductor (= ohmic loss).
The idea of half cells: When the cells are halved, the current in the cells and in the wires that connect them together is reduced to the same extent, because the connectors for half cells have a smaller cross-section. At the same electrical resistance, the losses decrease in parallel.
The current in the half cell module is increased by the cell stringing in order to achieve parameters similar to those of a common 72-cell module. This means that the choice of inverter remains flexible, even for half-cell modules.
Cell stringing in a 144-cell module
With the TwinPeak solar modules from REC and the poly half-cell solar module from Suntech, Krannich Solar has two suppliers of half-cell modules in its portfolio. The advantages of half-cell modules in practice: Thanks to innovative cell technology, they generate a particularly high output on a small area and produce electricity even when they are partially shaded.