Skip to main content

​
Summary

DC System Losses account for non-ideal effects that reduce power from the calculated to actual DC power available at inverter DC terminals. PlantPredict applies loss factors for module , , module quality variation, and DC health. These losses are applied as a combined coefficient that reduces effective irradiance before power calculation. DC wiring losses are applied downstream in the model, accounted for as additional . Time-dependent degradation is applied downstream of the single-diode conversion and is documented separately in the Degradation Losses (DC Applied) and Degradation Losses (AC Applied) pages.

​
Inputs

NameSymbolUnitsDescription
Effective POA IrradianceGPOA,tot,effG_{POA,tot,eff}W/m²Combined front and rear POA irradiance from the irradiance calculation
Module Mismatch CoefficientfMMf_{MM}%Module-to-module mismatch loss percentage
Light-Induced DegradationfLIDf_{LID}%Light-induced degradation loss
Module Quality FactorfMQf_{MQ}%Power deviation from nameplate due to module binning and manufacturing tolerances
DC Health FactorfDCHf_{DCH}%User-defined DC system loss to account for factors such as connection degradation
Backside MismatchfMM,rearf_{MM,rear}%Rear-side irradiance mismatch loss
Average Rear IrradianceGPOA,rearG_{POA,rear}W/m²Average rear irradiance after structure shading, before bifaciality weighting (from rear irradiance)
Effective Front POA IrradianceGPOA,front,effG_{POA,front,eff}W/m²Front-side effective POA irradiance

​
Outputs

NameSymbolUnitsDescription
Scaled Effective IrradianceGPOA,tot,eff′G'_{POA,tot,eff}W/m²Effective POA irradiance after DC system losses

​
Detailed Description

PlantPredict applies module mismatch, LID, module quality, and DC health losses as a single combined coefficient that uniformly scales the effective POA irradiance before the single-diode conversion. Each input percentage is converted to a fraction (divided by 100) before use: GPOA,tot,eff′=GPOA,tot,eff×CcombG'_{POA,tot,eff} = G_{POA,tot,eff} \times C_{comb} where GPOA,tot,effG_{POA,tot,eff} is the total effective POA irradiance from the irradiance calculation, including all front-side components and bifaciality-weighted rear irradiance. The composition of CcombC_{comb} depends on the prediction version.

​
Version 10 and Later

The combined coefficient includes module mismatch, module quality, LID, and DC health: Ccomb=(1−fMM)×(1−fMQ)×(1−fLID)×(1−fDCH)C_{comb} = (1 - f_{MM}) \times (1 - f_{MQ}) \times (1 - f_{LID}) \times (1 - f_{DCH}) For bifacial modules, backside mismatch fMM,rearf_{MM,rear} is applied directly to the rear irradiance in the rear irradiance calculation and is not part of the combined coefficient.

​
Version 9 and Earlier

In Version 9 and earlier, the combined coefficient also includes rear-side mismatch for bifacial modules. Because the combined coefficient is applied uniformly to all irradiance components, the backside mismatch fraction is approximated as an effective value weighted by the rear-to-front irradiance ratio: fMM,rear,eff=fMM,rear⋅GPOA,rearGPOA,front,efff_{MM,rear,eff} = f_{MM,rear} \cdot \frac{G_{POA,rear}}{G_{POA,front,eff}} where GPOA,rearG_{POA,rear} is the average rear irradiance after structure shading (see Rear Irradiance) and GPOA,front,effG_{POA,front,eff} is the front-side effective POA irradiance. The full combined coefficient becomes: Ccomb=(1−fMM)×(1−fMQ)×(1−fLID)×(1−fDCH)×(1−fMM,rear,eff)C_{comb} = (1 - f_{MM}) \times (1 - f_{MQ}) \times (1 - f_{LID}) \times (1 - f_{DCH}) \times (1 - f_{MM,rear,eff}) Because the coefficient is applied uniformly to both front and rear irradiance, this approach slightly overestimates the backside mismatch loss compared to applying it directly to the rear irradiance. Version 10 eliminates this by moving backside mismatch upstream into the rear irradiance calculation. For monofacial modules, GPOA,rear=0G_{POA,rear} = 0 so fMM,rear,eff=0f_{MM,rear,eff} = 0 and the combined coefficient reduces to the Version 10+ form.

​
Loss Reporting

For reporting (loss tree), each individual loss component is approximated as Li=Pmpp×fiL_i = P_{mpp} \times f_i, where PmppP_{mpp} is the maximum power point power from the single-diode equation and fif_i is the corresponding loss fraction.