(Symbol: h is commonly used.) (Unit: dimensionless, usually expressed as a percentage, %)
ratio of output quantity to input quantity
NOTE 1 The quantity specified by the term "efficiency" is normally the power, energy, or electric charge produced by or delivered to a component.
a) ampere-hour efficiency
(Symbol: hAh)
ratio of the amount of electrical charge removed during discharge conditions to the amount of electrical charge added during charge conditions in an electrical energy storage device
It is calculated by:
hAh = Id Td / (Ic Tc);
where
hAh is ampere-hour efficiency;
Id is discharge electric current (A);
Td is discharge time (h);
Ic is charge electric current (A);
Tc is charge time (h)
b) array efficiency
sunlight to electricity conversion efficiency of the PV array
c) charging efficiency
generic term to express ampere-hour efficiency (or less commonly, watt-hour efficiency in an energy storage device
d) collection efficiency
ratio of the number of electrons flowing out of a PV cell to the number of incident photons in a short-circuit condition
e) PV conversion efficiency
ratio of maximum PV output to the product of PV device area and incident irradiance measured under specified test conditions, usually standard test conditions, STC
NOTE 2 See also "conditions/standard test conditions", 3.4.16e)
f) effective energy efficiency
energy efficiency during an identified period
g) inverter efficiency
ratio of the useful inverter output power to its input power, or output energy to its input energy
h) mean array efficiency
(Symbol: hAmean)
average PV array efficiency
NOTE 3 Mean PV array efficiency is useful for comparison with the rated PV array efficiency
NOTE 4 The difference between mean and rated efficiency represents diode, wiring, mismatch and other losses during PV system operation
i) overall system efficiency
(Symbol: htot)
efficiency of the whole system including all the electricity sources
NOTE 5 Overall system efficiency is derived from the electricity supplied to the loads based on the solar irradiation and fuel supplies
j) partial efficiency
ratio of output power to input power, or output energy to input energy), when a component is operating below its rated output
k) partial load efficiency
ratio of the effective inverter output power to its input power, or output energy to input energy, at a specified load
l) power efficiency
ratio of active output power to active input power
m) rated efficiency
Pertaining to a PV device: efficiency of a device at specified operating conditions, usually standard test conditions, STC
NOTE 6 See also "conditions/standard test conditions", 3.4.16e)
Pertaining to an inverter: efficiency of an inverter when it is operating at its rated output
n) system efficiency
(Symbol: hSP) (Unit: dimensionless, usually expressed as a percentage (%) over a period of time such as a month or year)
ratio of PV system output energy (WSP) to the product of total irradiation (QASP) and PV array area (AP)
It is calculated by:
hSP = WSP / (QASP AP)
where
hSP is system efficiency;
WSP is system output energy (J);
QASP is total irradiation (J ´ m–2);
AP is array area (m2)
o) efficiency tolerance
(Unit: dimensionless, usually expressed as a percentage, %)
permissible tolerance between the manufacturer's specified efficiency and the measured efficiency
p) watt-hour efficiency
(Symbol: hWh)
ratio of the amount of electrical energy removed during discharge conditions to the amount of electrical energy added during charge conditions in an electrical energy storage device
It is calculated by:
hWh = Id Td Vdav / (Ic Tc Vcav) = hAh Vdav / Vcav
where
hWh is watt-hour efficiency;
Id is discharge electric current (A);
Td is discharge time (h);
Vdav is average discharge voltage (V);
Ic is charge electric current (A);
Tc is charge time (h);
Vcav is average charge voltage (V)
NOTE 7 In calculating watt-hour efficiency, the ratio of average voltage to the specified final discharge voltage is often used, rather than voltages at any specified time.
q) weighted average conversion efficiency
method of estimating the effective energy efficiency
NOTE 8 Weighted average conversion efficiency is calculated as the sum of products of each power level efficiency and related weighting coefficients depend on a regional irradiance duration curve. When a PV system is a stand-alone type with a storage sub-system, the weighting coefficients depend on the load duration curve. |