Ambient Temp

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    Greg Smith

    The operating and maximum temperature ranges often cause confusion with installers, however, since Tigo does not state a "maximum" temperature range for the MLPE products, we must take the operating range at face value.

    Most PV inverters state both ranges so that the designer will get an idea of the derating temperature. The operating range offers full power while the maximum range will suffer derating. Since these devices, either PV inverters, charge controllers, micro inverters, optimizers, et. al. rarely utilize external temperature sensors for operational constraints, the stated temperature ranges are what the device measures inside its chassis.

    For example, the UL listed 500W TS4-A-O states an operating temperature range of -40C to 85C (-40 to 185F). This means the unit must be mounted in an area that will not exceed these ranges. If so, then the warranty will be compromised. And exceeding this temperature range has happened in extreme environments, but only a few circumstances. Remember, the range is what is measured in the device chassis, not the ambient air temperature.

    There are many studies on the topic of measuring the nominal operating cell temperature (NOCT) vs. the ambient temperature. I found 2 studies where the NOCT was 49C and 60C. These are probably fair estimates for those parts of the world, however, there are many design variables that will affect the NOCT. The good news is that PV module mounting best practices should mitigate the chances of reaching the 85C range. Airflow is the main variable- the more distance between the mounting surface the array the better.

    Studies: 

    University of West Indies: Limiting Effects of Temperature on the Performance of a Si-PV Array in Trinidad and Tobago

    National Renewable Energy Laboratory (New Mexico, US): Measuring and Modeling Nominal Operating Cell Temperature (NOCT)

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