a) current-temperature coefficient
(Symbol: a) (Unit: A ´ K–1 (absolute), K–1 (relative))
change of the short-circuit electric current of a PV device per unit change of temperature
NOTE 1 Both absolute and relative values are used
NOTE 2 The user is cautioned to be aware of the difference between the absolute and the relative unit of measure, and to use the appropriate coefficient with the proper equation
NOTE 3 If the current-temperature coefficient has the unit of A ´ K–1, the value of the coefficient is a function of the series-parallel circuit arrangement. For example, a 36-cell PV module will have different coefficients if all 36 cells are connected in series versus a circuit with three parallel strings of 12 series-connected cells in each
NOTE 4 The short-circuit current varies with irradiance and to a lesser extent with temperature
b) voltage-irradiance coefficient
(Symbol: δ) (Unit: dimensionless)
ratio-change of the open-circuit voltage (Voc1 / Voc2) of a PV device as a function of the ratio-change of the natural logarithm of irradiance, ln(G1 / G2)
c) voltage-temperature coefficient
(Symbol: b) (Unit: V ´ K–1 (absolute), K–1 (relative))
change of the open circuit voltage of a PV cell per unit change of cell junction temperature
NOTE 5 The user is cautioned to be aware of the difference between the absolute and the relative unit of measure, and to use the appropriate coefficient with the proper equation
NOTE 6 If the voltage-temperature coefficient has the unit of V ´ K–1, the value of the coefficient is a function of the series-parallel circuit arrangement. For example, a 36-cell PV module will have different coefficients if all 36 cells are connected in series versus a circuit with three parallel strings of 12 series-connected cells in each |