Path-Q Solar
How should string voltage be checked when panels operate in cold conditions?
Answer
Calculate the string's maximum open-circuit voltage at the lowest expected cell or site design temperature, then confirm it remains below the inverter, disconnect, conductor, and other equipment limits. Cold temperatures generally increase module voltage, so checking only the panel's nominal voltage is insufficient.
Key points
- Use the panel's open-circuit voltage and voltage temperature coefficient from its current datasheet.
- Multiply the cold-adjusted module voltage by the number of modules in the string.
- Check the resulting maximum against every applicable component rating, not only the inverter's normal MPPT range.
- Also verify that hot-weather operating voltage remains within the inverter's MPPT operating range.
What it depends on
- Panel open-circuit voltage and temperature coefficient
- Number of modules in the string
- Lowest design temperature and installation conditions
- Inverter, disconnect, conductor, and equipment voltage limits
Risks and trade-offs
- Excess cold-weather voltage can damage equipment or create a safety hazard.
- Reducing string length to control maximum voltage may create insufficient operating voltage in hot conditions.
- Using outdated or incorrect datasheet values can invalidate the calculation.
Information you may need
- Exact panel and inverter specifications
- String length and wiring arrangement
- Design minimum and maximum temperatures
- All relevant equipment voltage ratings
Your next step
What to do next
Ask the designer to provide a cold-voltage and hot-operating-voltage calculation using current datasheets and the site's design temperatures.
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