Design
How can I estimate my FRONIUS IG’s typical maximum AC power output?
There are numerous specifications that a PV designer must understand in order to size a PV array to a grid-tie inverter. Specifications like STC, PTC, rated efficiency, and balance of system’s (BOS) efficiency must all be taken into account in addition to a wide variety of site-specific conditions. There are a wide variety of “Rule of Thumb” estimates. One common estimation method uses the following equation:
[ (# of modules) x (module PTC rating) x (inverter’s CEC rated efficiency) x (BOS efficiency)] = The Estimated Maximum Continuous AC Power Output
This calculation can give you a general idea of what to expect in typical, peak field conditions.
What are the yellow, green, and orange squares on the Configuration Tool trying to tell me?
The Configuration Tool gives the PV system designer many options in order to create the most optimal design. The color-coding of the Configuration Tool details the PV STC power. The FRONIUS IG is optimized for peak performance with every color square. Values in yellow squares mean that you may want to consider purchasing the next smaller inverter. Check your AC power estimate using your “Rule of Thumb” calculation to see what makes the most sense for you based on your site-specific conditions. Similarly, the orange squares mean that it may be worthwhile to consider using the next larger inverter size or adding an addition inverter. Remember – this software tool is not able to take into account the specifics of your site like tilt, orientation, the accuracy of the module ratings, or other factors that will impact your array’s output.
How does the FRONIUS IG work when the PV array’s strings are at different orientations, shaded, or have dissimilar numbers of modules?
In a PV system designer’s ideal world, shading is non-existent and all arrays face due south. But, in the real world that this isn’t always the case. These non-optimal designs may include some degree of shading, different orientations, and/or dissimilar strings. The FRONIUS IG was designed to work well in most non-optimal configurations, and can be used with confidence in systems that have different orientations or shading. Conversely, we do not recommend using the FRONIUS IG when designing a system with dissimilar strings. Please see our white paper entitled, FRONIUS IG – Reaction to Non-Optimal Conditions for more information.
How much array can I put on a FRONIUS IG?
Because of the FRONIUS IG series design, the most important factor is to be within the voltage window (150 V to 500 V). Your system size will depend upon your environment (latitude, irradiance and temperature), your array's orientation and how often your system should be at full load. Also, your modules typically do not output their rated power since they are usually not at those conditions (25°C, 1000 W/m2). If the total DC input, after conversion losses, would exceed the output ability of the FRONIUS IG, it will change the operating point from the maximum power point to a point where it draws less current, and can output the maximum possible power.
In some situations, you may be able to oversize a Fronius inverter by as much as 30% of the rated power output and never get 'clipping' losses from operating off the maximum power point. However, we typically recommend the following maximums: 2500 Wp for the IG 2000, 3300 Wp for the IG 3000, 3000 Wp for the IG 2500-LV, 5000 Wp for the IG 4000, 6300 Wp for the IG 5100, and 5500 Wp for the IG 4500-LV. Larger PV systems will work, but may not maximize the use of the array during peak conditions. Conversely, these estimates may be high for a site with optimal conditions and high-performance arrays.