Page 88 - Applied Photovoltaics

Chapter

5

PV CELL

INTERCONNECTION

AND MODULE

FABRICATION

5.1 MODULE AND CIRCUIT DESIGN
Solar cells are rarely used individually. Rather, cells with similar characteristics are
connected and encapsulated to form modules which, in turn, are the basic building
blocks of solar arrays.
Since the maximum voltage from a single silicon cell is only about 600 mV, cells are
connected in series to obtain the desired voltage (Mack, 1979). Usually about 36
series cells are used for a nominal 12V charging system.
2
Under peak sunlight (100 mW/cm ), the maximum current delivered by a cell is
2
approximately 30 mA/cm . Cells are therefore paralleled to obtain the desired current.
Fig. 5.1 illustrates a typical connection system and the standard terminology used to
describe such connections.
A database including the characteristics of 125 commercial modules is available
online from Sandia National Laboratories (2002).

5.2 IDENTICAL CELLS
Ideally, the cells in a module would exhibit identical characteristics and the module
I-V curve would be the same shape as that of the individual cells, with a change in
scale of the axes. Therefore, for N cells in series and M cells in parallel