Shadings: Electrical Loss , sheds

What this step does

A strip is a band along a row of modules whose modules form their own strings. When the shadow of the row in front reaches a strip, the strings in that strip stop producing. The electrical loss then exceeds the light the shadow removes, and this line of the diagram takes the extra loss from the array energy. It scales the timestep's module power by the extra fraction of the direct sunlight the affected strings lose. The row is zero unless the Model tab's Electrical shading effect step is set to According to strings.

The math

1. Running total
2. Loss at a timestep

$$E_{after} = E_{before} - E_{row},\qquad E_{row} = \frac{\Delta t}{1000\,P_{DC}}\sum_i L_i \tag{1}$$ $$L_i = N\,P_{mpp}(G_i, T_{arr,i})\,\frac{f_{elec,i}\,B_i\,F_{IAM,i}\,(1-f_{soil})}{G_{front,i}} \tag{2}$$

where

Symbol	Meaning	Unit
$E_{before}$	the running total of the loss diagram before this row	kWh/kWp
$E_{after}$	the running total after this row	kWh/kWp
$E_{row}$	the row taken as a loss	kWh/kWp
$\Delta t$	the length of one timestep	hours
$P_{DC}$	the DC nameplate of the system	kWp
$L_i$	the power lost at timestep $i$ over the whole system	W
$N$	the number of modules in the system	—
$P_{mpp}(G, T)$	the maximum power of one module at irradiance $G$ and cell temperature $T$, from the module model	W
$G_i$	the irradiance the module converts at timestep $i$: the effective irradiance on the front plus the bifaciality factor times the rear irradiance	W/m²
$T_{arr,i}$	the cell temperature at timestep $i$	°C
$f_{elec,i}$	the extra fraction of the direct sunlight lost by the switched-off strings at timestep $i$, times the fraction for electrical effect (1 by default)	—
$B_i$	the direct sunlight on the plane after the horizon, before the row shading	W/m²
$F_{IAM,i}$	the incidence-angle modifier at the incidence angle of timestep $i$	—
$f_{soil}$	the soiling fraction of the month	—
$G_{front,i}$	the effective irradiance on the front of the modules: the lost share is taken against the front alone, and the power at $G_i$, front and rear	W/m²

Reading the number

A loss, negative. Fewer strips across the row make it larger, because a shadow on one strip then switches off a larger share of the row. The fraction for electrical effect scales it (1 by default). The cell height along the slope sets how fast a strip's loss rises as the shadow climbs across its first row of cells. Rows with two strips lose about 1 to 2 % of the nominal energy. An array without rows in front of it shows zero.

API

loss.elec_shade

Symbols follow the symbol registry.