Part Two: DC Losses
Module Losses
Module Losses
Manufacturing Mismatch Loss
Suggested Values:
- 2% for most modules and systems with long strings
- 1% for modules that have tight wattage tolerances
Manufacturing variations can lead to differences in the electrical parameters of modules. This type of mismatch loss is applied as a fixed percentage reduction of the system’s DC power output.
Depending on the setup and length of strings, mismatch values can range from 0.01% up to 3%. Aurora uses a default value of 2% based on past industry consensus.
Module Losses
Light-Induced Degradation
Suggested Values:
- 1.5% default loss
- For newer modules that use LG components, the LID loss should be set to 0%. LG components are not subject to LID
Light-induced degradation (LID) occurs when the electrical characteristics of crystalline silicon solar cells change when they’re exposed to light. LID losses range from 0.5% to 1.5% and happen within the first few hours of the new panel’s exposure.
Note: Not all modules are affected by LID. Whether a module will experience this loss lies in the solar cell’s crystal structure and silicon wafer electrical properties.
Further reading:
Module Losses
Nameplate Rating Losses
Suggested Values:
- 0% for modern modules
- If a module has an error range on the wattage rating, such as “250W +/- 2.5W," you can enter a 1% loss (2.5/250) to ensure that your simulation provides a conservative estimate of power production.
Module nameplate rating loss represents the loss due to the difference in the stated power of the module compared with how it actually performs at Standard Test Conditions (1000 W/m2 and 25°C). This is also referred to as “power tolerance” and is typically expressed as a plus-or-minus percentage. For example, a 250-watt panel with a +/- 5% power tolerance could actually produce anywhere from 237.5 watts to 262.5 watts under ideal conditions (12.5 watts is 5% of 250 watts).
Most modern modules have datasheets that accurately reflect module operation at STC, so the default value for this loss is 0%.
