(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 (V_oc1 / V_oc2) 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