Any effects that simulation engines do not explicitly model are captured through system losses. These are linear loss factors (measured in percent) that get applied to the output of the simulation engine.
Admins can customize the default system losses for their organization in Settings.
The following system losses can be specified in the performance simulation settings in Aurora. Note that losses will be applied at different steps in the simulation.
Irradiance Losses
These losses reduce the amount of sunlight hitting each panel and therefore get applied to the incident irradiance of each module.
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Light-Induced Degradation (default 1.5%): Solar modules experience a loss in output power when they are initially exposed to sunlight.
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Shading (default 3%): Shade loss can greatly impact the energy production of a solar installation. To account for this, you can enter a linear shade loss applied to the irradiance on the modules in your design. Note that the shading loss factor will show as "n/a" if the
Shading Engineoption is checked off. In that case Aurora will automatically calculate the incident irradiance for each panel and each hour of the year and run a detailed simulation of the system, accounting for irradiance and partial shading conditions. Please see the section on Aurora's simulation engine for more detail. -
Snow (default 0%): In some areas snow cover can affect energy production of solar installations. The exact amount will depend on location, array orientation, and cleaning schedule. You will need to input an appropriate loss factor for the area in which your design is located.
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Soiling (default 2%): Soiling accounts for dirt and dust accumulation on the solar panels. Depending on the location of the project this can be more or less severe, so this factor will need to be adjusted in some cases.
Shading, snow, and soiling losses can all be specified on an annual OR monthly basis. The default is annual; to use monthly losses, click the button that says annual in parentheses next to one of the losses. This will switch the system losses view to a monthly breakdown for that loss.
DC Losses
DC losses represent energy lost on the DC side of the system (losses before the inverter) and are applied to the DC output of each module or string. These losses relate to modules, strings, and wiring.
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Module Nameplate Rating (default 0%): Account for variation of the module power from the value provided in the manufacturer's datasheet. In modern modules the power tolerance is typically positive (i.e., the module is guaranteed to produce at least the rated power at STC), and so conventional practice is to have a default loss of 0%.
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Mismatch (default 2%): While all modules of a given type have the same datasheet, in practice their IV characteristics can vary slightly due to variablity in manufacturing processes. This mismatch in IV characteristics results in slightly reduced energy production in string inverter designs. Industry consensus is that around 2% of system energy production is lost due to module mismatch. Module level MPPT tracking allows modules to operate independently of each other and mitigate mismatch losses. Thus Aurora does not apply the mismatch system loss in the case of microinverter, DC optimizer, or cell string optimizer designs.
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Connections (default 0.5%): Represents resistive losses in connectors in the system
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Wiring (default 2%): This accounts for resistive losses in the wiring of the system (both on the DC and AC side). This value may need to be adjusted depending on conductor choice and wire runs.
AC Losses
AC losses are applied to the simulated AC output of the system. These losses capture effects on system performance that have to do with the system as a whole.
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Age (default 0%): This system loss accounts for any degradation of the system that is due to age. The main purpose of this loss is to be able to simulate the production of systems, which have been operating for some time and have thus already seen performance degredation. For new systems this will be 0%, which is the default.
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System Availability (default 3%): System availability account for downtime of the system due to maintenance, equipment defects and grid outages.
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Other (default 0%): This is a catch-all category for any losses that cannot be classified by the above categories.
Note that system losses are multiplicative, i.e. two losses of 4%4% and 3%3% will result in a 1−(1−4%)×(1−3%)=6.88%1−(1−4%)×(1−3%)=6.88% estimated overall loss. However, the exact overall loss can vary, since losses are applied at different stages of the performance simulation.