Power Binning Effect

The manufacturing process for PV cells is highly sensitive to a range of factors, with the result that cells from the same manufacturing run exhibit a range of performance levels. To reduce mismatch losses and other problems such as hot-spots, cells are tested and grouped into bins of cells with similar performance levels before being assembled into modules, and the resulting modules from each bin are then sold as different variants within the same series (for example, a series of nominally 300 W modules may be marketed with variants of power 295 W, 300 W, 305 W and 310 W).

Even amongst modules of the same variant, there will be a range of power outputs, the "Power Binning Range". Manufacturers will frequently provide an estimate of the lower and upper limits of this range, for example the "Power output tolerance" \(\Delta_{\text{max}}\) might be given as -0% to +3%.

In order to allow for this effect, SolarFarmer includes the module-type-specific Power Binning Effect (\(\Delta_{\text{binning,mtype}}\)) in its calculation. If the information is available, the user should input the low and high ends of the Power Binning Range for each module type used, and SolarFarmer will provide a recommended \(\Delta_{\text{binning,mtype}}\) value for the specific module type to compensate. This value defaults to lower end of the range plus one-quarter of the difference between lower and upper ends but can be adjusted by the user. As the Power Binning Effect for a module type frequently varies between plants, this input is considered plant- rather than module-specific.

As \(\Delta_{\text{binning,mtype}}\) is constant, the instantaneous and time-averaged values of this effect are all simply equal to \(\Delta_{\text{binning,mtype}}\).

Assuming the plant array is composed entirely of a single type of module, plant array power after the Power Binning Effect is simply:

$$P_{Parray,npmc,binning}\left( t \right) = \left( 1 + \frac{\Delta_{binning,mtype}}{100%} \right) \bullet P_{{Parray,npmc,T_{c},G}_{\text{eff}}}(t)$$

Where the plant array is composed of different types of module, each type may have its own specific Power Binning Effect \(\Delta_{\text{binning,mtype}}\). In this case:

$$P_{Parray,npmc,binning}\left( t \right) = \sum_{j = 1}^{N_{\text{submodules}}}{P_{submod,npmc,binning}\left( t \right)}$$

Where:

$$P_{submod,npmc,binning}\left( t \right) = \left( 1 + \frac{\Delta_{binning,mtype}}{100%} \right) \bullet P_{{Parray,npmc,T_{c},G}_{\text{eff}}}\left( t \right)$$

Note that SolarFarmer currently assumes that module type is constant across individual arrays.

The combined power binning effect at time t is:

$$\Delta_{\text{binning}}\left( t \right) = \left( \frac{P_{array,npmc,binning}(t)}{P_{{Parray,npmc,T_{c},G}_{\text{eff}}}\left( t \right)} - 1 \right) \bullet 100%\ $$

Powers can be summed over desired periods to get monthly or annual Power Binning Effects. As for other effects, it will be necessary to de-season if the input data is not a single complete year.

In order to consider the Power Binning Effect alongside other conversion effects in the mismatch calculation, an adjustment to the current from each submodule is calculated as:

$$\eta_{submod,binning} = \left( 1 + \frac{\Delta_{binning,mtype}}{100%} \right)$$