Load ratio

Method

The loss at every timestep is the design fraction times the array power times the ratio of the array power to its nameplate (1), so the loss fraction grows in proportion to the load and equals the design fraction at nameplate power. No fixed resistance is derived. For the operating-point search, each timestep uses the resistance that gives this loss at the maximum-power current (2).

The math

1. Wiring loss
2. Resistance of the operating-point search

$$L_i = f_w\,P_i\,\frac{P_i}{P_{nom,dc}} \tag{1}$$ $$R_{w,i} = \frac{L_i}{I_{mpp,i}^2} \tag{2}$$

where

Symbol	Meaning	Unit
$L_i$	the wiring loss at timestep $i$	W
$f_w$	the design loss fraction	—
$P_i$	the array DC power after the flat derates at timestep $i$	W
$P_{nom,dc}$	the array DC nameplate	W
$R_{w,i}$	the equivalent wiring resistance at timestep $i$	Ω
$I_{mpp,i}$	the array current at maximum power at timestep $i$	A

API

dc_losses.ohmic_model = load_ratio

Symbols follow the symbol registry.