Daily and seasonal temperature variances significantly influence the production capabilities of the PV modules in your array. Simply comparing the module specifications against the TS4 datasheet will not provide an accurate assessment of compatibility.
This article focuses on how to design a system for different temperature ranges so you can determine if a PV module is compatible with Tigo's TS4 MLPE products.
Contents:
Temperature Coefficient
When designing a system, it is important to use the PV module's Temperature Coefficient to calculate the gains (or losses) in voltage due to local ambient temperature changes. This will ensure the PV module is compatible with the system's voltage specs.
The common practice is to compare the PV module's Temperature Coefficient against the lowest recorded temperature for the area. However, solar designers have realized that using 100-year record-low temperatures result in overly conservative designs.
The 2017 NEC 690 added a section authorizing the use of ASHRAE Temperature Data for these calculations since they can better reflect average conditions.
Comparison Exercise
Using the available data sheets, along with the temperature resources (below), we can confirm whether the PV-Module is compatible with the TS4-A-O:
From these data sheets, you will need to gather four pieces of information:
- Voc (from PV-Module data sheet)
- Temperature Coefficient of Voc (%) (Temperature Characteristics of PV-Module data sheet)
- Max Voc (from TS4 product data sheet)
- ASHRAE temperature for the area (links provided below)
Then, plug this information into a resource to calculate the effects on the PV-Module's output.
Step 1: Go to: Maximum Solar Voc and Pmax Online Calculator
Step 2: Fill in the calculator data using the PV-Module data sheet information and the additional temperature information found in the links below.
In this exercise, we used the ASHRAE data provided for Sacramento, California:
Below is what the Maximum Solar Voc and Pmax Online Calculator entries look like for this area:
Note: The Extreme Minimum (-3 ºC) was used for the Worst Case Temperature Value. For string sizing applications, you would also include a 2% average temperature value (as per the NEC 690).
Step 3: Click submit and review the results
The two most important results are:
- Max Voltage: 52.94 (under the 80V maximum on the TS4)
- Pmax: 570.96 (under the 700W maximum on the TS4)
When comparing these numbers, we see that the PV module easily fits within the limits of the TS4 (even though it could make up to 571W in the right conditions!).
Conclusion: Even in the worst-case temperature scenario for this area, this module's output will not exceed the TS4 tolerances.
Q: What happens if I use a module with corrected temperature values for voltage and power that are close to or exceed the TS4 limits?
The most common scenario where this could happen is when using a Tigo TS4 product that accepts inputs for 2 PV modules (like the TS4-A-2F).
Let's take a quick look at a design using the TS4-A-2F. The data sheet specs are almost identical to the TS4-A-O used in the previous example:
This product has a maximum power value of 1000W, but since the 2F accepts 2 module inputs, each input is limited to 500W. Let's compare our worksheet results with the TS4-A-2F datasheet:
The maximum Voc is 52.9V (which is still comfortably below the 80V max input voltage), and the module's max current is also within specs. However, the module is rated for 520W, and the 20-watt overage of the PV module could exceed the power rating.
Generally speaking, depending on the system's design and geographic location, this module could still be compatible with the TS4-A-2F.
If you have questions or need design assistance, please don't hesitate to contact the Tigo Customer Success team.
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How to Calculate a PV Module's Voltage (Voc) for Different Ambient Temperatures