Inverter Loss due to power threshold

What this step does

The row takes from the array energy the energy of the timesteps in which the inverter does not start. The inverter does not start when the effective irradiance is below a fixed 7 W/m², which the low-light threshold input does not change, or when the array's maximum power is at or below the inverter's power threshold, where the inverter delivers nothing. Timesteps that the low-light threshold has set to zero carry no array energy and add nothing here.

The math

1. Running total
2. Loss at a timestep

$$E_{after} = E_{before} - E_{row},\qquad E_{row} = \frac{\Delta t}{1000\,P_{DC}}\sum_i L_i \tag{1}$$ $$L_i = N_{inv}\,P_{mpp,i} \quad (\text{no start}) \tag{2}$$

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
$N_{inv}$	the number of inverters	—
$P_{mpp,i}$	the maximum power of one inverter's array at timestep $i$, after the DC losses	W

Reading the number

A loss, negative: a small fraction of a percent on utility and rooftop systems alike. A higher power threshold and a weather file with many dawn and dusk timesteps make it larger.

API

loss.inv_threshold

Symbols follow the symbol registry.