SunDAT is able to provide a recommended string size for your table, based on the module, inverter, and weather source file intended to be used in the project. Learn how to get a recommended string size and how it is calculated.
TABLE OF CONTENTS
- Assigning module, inverter, and weather source file
- View the recommended string size
- String size calculation
- See also
Assigning module, inverter, and weather source file
Prerequisite: a project has to be created in Project Setup
- Go to the Site Overview icon
- In the General tab, scroll down to Choose Weather Source and select a weather source file
- Scroll down System Components and in the Select Module(s) to be used in this site choose a module
- Next, continue down to Select Inverter(s) to be used in this site and select an inverter
View the recommended string size
Module(s), inverter(s), and weather source file has to be selected in Site Overview (see the steps above)
- Go to the Tables icon and then choose the type of table to be created
- Choose a New table or choose an existing table
- Scroll down to Choose a module from the library input and select the module to be used in the table. The module that was selected in Site Overview, will be the first one in the list and has an orange bookmark next to it.
- After selecting the module, the String Size input will now show a number in the header. This is the recommended string size based on the selected equipment and weather source file.
- If you want to use the recommended string size, just type in the value into the string size input
String size calculation
View the calculation for the recommended string size and adjust values to understand the impact to the string size
- To bring up the String Size Calculation, click the grey String Size header above the string size input
- The String Size Calculation window is broken up into 5 sections, the project location, ASHRAE Data, Module Characteristics, Inverter Characteristics, High Temperature check, and Low Temperature check.
- ASHRAE Data comes from the weather source file
- Module Characteristics values are from the module component found in the equipment library either from the Global Library or custom library. These values are used for the calculations of High temperature check and Low temperature check.
- Inverter Characteristics values are from the module component found in the equipment library either from the Global Library or custom library. These values are used for checking that the the High temperature check calculation is above the minimum DC voltage rating and Low temperature check calculation is below or equal to the maximum DC voltage rating.
- High temperature check is the formula to check the voltage is below or equal to the the minimum DC voltage rating.
- Low temperature check is the formula to check the voltage is below or equal to the the maximum DC voltage rating.
- [Optional] In ASHRAE Data, the Annual Dry bulb min temperature can be changed from the default one pulled from the weather source file. This will affect the formulas for the High temperature check and Low temperature check.
- At the High temperature check, there is a slider for the number of modules per string. This can be adjusted to see what the implications are when changing the string size.
What is the formula used to do the low temperature check?
number of modules x Module Voc x (1+(Annual dry bulb minimum temperature - 25C) x (Module Temp. coefficient Voc)/100)
What do the abbreviations mean?
DB: Dry bulb
Ebn: Clear-sky beam normal irradiances
Edh: Clear-sky diffuse horizontal irradiance
Voc: Open circuit voltage
TCvoc: Temperature coefficient of Open circuit voltage(Voc)
TCvmp: Temperature coefficient of voltage at maximum power(Pmax)
NOCT: Nominal operating temperature
VDC: Voltage DC
Recommended string size is not appearing
- Check if a weather source file is selected and available for the location of the project. For certain locations, weather source files might not be available.
- If using custom equipment