Shade Management with SMA ShadeFix

It is not always possible to prevent dormers, chimneys, or trees from casting their shade on PV modules. However, in order not to jeopardize the economic viability of a PV system, yield losses resulting from shade must be minimized already in the planning phase. Influential factors such as the arrangement of the PV modules, their circuitry and in particular the choice of an appropriate inverter play an important role. By observing some important planning rules, these factors can be adapted to the respective PV system in such a way that their energy supply can be used almost completely. The following basic rules should be observed:

• Therefore, when selecting the roof area for a PV system, you should make sure that no permanent shade falls on the PV array, and especially in times of high irradiation (noon, summer months) no shade should fall on it at all, if possible. The Sunny Design software for system design can be used to estimate the energetic consequences of shading, taking into account its size and change over the course of a year. Detailed information on the configuration can be found in the user manual at www.SMA-Solar.com.

• Shade analysis: The proportion of the shaded PV modules in relation to the total PV system and the course of shade over time are important characteristics of a shaded PV system. The following recommended actions are important when dealing with shaded PV systems:

  • When a single PV module or a very low portion of the PV modules (e.g. < 10% of the total number) is shaded, shade can be distributed evenly on the strings.

  • If there is strong shading, it makes sense to operate the shaded and unshaded PV modules separately. The following applies:

    • Group together PV modules with similar irradiation.

    • No parallel connection of strings with different irradiation; provide a separate MPP tracker for each string. No parallel connection of strings with different irradiation; provide a separate MPP tracker for each string.

    • SMA ShadeFix is necessary to maximize the energy yield.

• The choice of the inverter also influences yield losses due to shade. The following points are to be observed when selecting the inverter:

  • PV inverters with a broad input voltage range can still adjust the optimal operating point despite shade and the resulting decline in MPP voltage.

  • By using a PV inverter with a single-string control, a shaded PV system can operate optimally and avoid most losses.

  • To keep yield losses due to shade to a minimum, it is necessary to use a PV inverter with SMA ShadeFix for shaded strings whose MPP tracking recognizes the presence of several operating points.

SMA ShadeFix

SMA ShadeFix minimizes the negative impact of shading and increases the energy output at the same time. Thanks to the continuous improvement of the proven MPP tracking of the SMA PV inverters, SMA ShadeFix reliably finds the maximum power point despite shaded PV modules. SMA ShadeFix also means that the PV inverter can detect the presence of multiple maximum power points in the available operating range, such as can occur in shading situations in particular. It enables the PV inverter to almost fully use the energy supply of the PV modules under all conditions. The power losses caused by the patented search method are hardly measurable and can be completely neglected. SMA ShadeFix is directly integrated into the inverter as a software-based solution. This significantly reduces the number of system components and minimizes installation and service efforts. This differs significantly from PV systems in which power optimizers are installed on each PV module.

If the use of SMA ShadeFix is compared to permanently installed power optimizers over the entire operating time, the yield gains are usually higher with slightly to medium shaded PV systems with SMA ShadeFix.

Yield increase with SMA ShadeFix compared to power optimization on each PV module in different shading situations

In addition, it is avoided that the reliability and availability of the PV system is reduced through the use of additional components. SMA ShadeFix provides the opportunity to secure the profitability of shaded PV system by preventing higher investment costs and maximizing yield.

Additional information is available under the following link: Whitepaper "SMA ShadeFix" and at www.SMA-Solar.com.