Deline 2020, from the rear cell rows

Method

At every timestep the total irradiance of each of the six rear cell rows of the rear model is the front irradiance plus the bifaciality times the row's rear irradiance. Their mean absolute difference, relative to their mean (1), gives Deline's fitted mismatch, scaled by the module's fill factor against 0.79 and held at 10 % (2). The loss on the rear irradiance is that mismatch divided by the bifacial gain (3, 4), held at the whole rear irradiance. Note: in the reference code (SSC) the rear irradiance can go negative here. The fraction replaces the flat fraction in the loss of the flat option. Values the model reads: the front irradiance is the plane irradiance after near shading and soiling, before the glass-reflection step; the fill factor is the module's V_mp I_mp over V_oc I_sc at standard conditions. It needs a rear model that computes the cell rows: bifacialvf (Marion 2017) or bifacialvf 1° sectors.

The math

1. Spread of the cell rows
2. Fitted mismatch
3. Bifacial gain
4. Loss on the rear irradiance

$$G_{cr,j} = G_{front} + b_f\,G_{rear,j},\qquad MAD = \frac{\sum_j \sum_k |G_{cr,j} - G_{cr,k}|}{N_{cr}^2\,\bar G_{cr}}\times 100 \tag{1}$$ $$M_{rm} = \min\!\left(10,\ (0.054\,MAD + 0.068\,MAD^2)\,\frac{FF_0}{0.79}\right) \tag{2}$$ $$g_{rear} = \frac{b_f\,\bar G_{rear}}{G_{front}}\times 100 \tag{3}$$ $$f_{rm} = \min\!\left(1,\ \frac{M_{rm}\,(1 + 100/g_{rear})}{100}\right) \tag{4}$$

where

Symbol	Meaning	Unit
$G_{cr,j}$	the total irradiance of rear cell row $j$	W/m²
$b_f$	the bifaciality factor of the module	—
$G_{rear,j}$	the rear irradiance of cell row $j$ after the structure shade	W/m²
$N_{cr}$	the number of cell rows, 6	—
$\bar G_{cr}$	the mean of the $G_{cr,j}$	W/m²
$MAD$	the mean absolute difference	%
$M_{rm}$	the mismatch of the module's power	%
$FF_0$	the module fill factor at standard conditions	—
$g_{rear}$	the rear side's gain over the front	%
$f_{rm}$	the rear mismatch fraction of the timestep	—

References

1. Deline, Ayala Pelaez, MacAlpine & Olalla 2020, Estimating and parameterizing mismatch power loss in bifacial photovoltaic systems, Progress in Photovoltaics 28(7) 691–703
2. NREL SAM Simulation Core (SSC) source code, release 2026.7.3, github.com/NatLabRockies/ssc: ssc/cmod_pvsamv1.cpp, cm_pvsamv1::intraElecMismatch() and its call in exec()

API

bifacial.rear_mismatch_model = deline_2020

Symbols follow the symbol registry.