Optimizer files - Canal Solar

With the emergence of bifacial photovoltaic modules on the market, many users question their compatibility with inverters, microinverters, and power optimizers. First of all, what is a power optimizer? If you have reached this article and are not yet familiar with the subject, I recommend reading two articles: PVSyst: photovoltaic systems with MLPE power optimizers and power optimizers for photovoltaic modules. Power optimizer The power optimizer is a small device connected to the output of the photovoltaic module. Due to its dimensions, and also practicality, the optimizer is physically housed behind the module, attached to the fixing structure or the frame of the module itself. The function of the optimizer, as its name suggests, is to optimize the energy generation of the photovoltaic module. This is done through the individualization of the MPPT (maximum power point tracking) of each of the modules that make up the photovoltaic system. Thus, the modules are decoupled and make the photovoltaic system practically immune to shadows. There are still other advantages. Even in situations without shading, the optimizers reduce the so-called power “mismatch”, which is the discrepancy between the powers of the modules connected in series. Typically the gain obtained from reducing mismatch is around 2%. It seems little, but over the lifetime of the photovoltaic system this can represent a large amount of energy. Figure 1: The power optimizer is connected to the output of the photovoltaic module and physically housed under the module, and can be attached to the structure or the frame of the module itself. Besides the issue of shadows and power mismatch, there is another advantage to using optimizers. With them, it is possible to form strings of modules installed in different positions, subject to different solar irradiance and quite distinct operating conditions. This would be impossible with traditional inverters. In complex rooftops or urban installations subject to significant shading from nearby objects, an optimizer is a good choice for photovoltaic solar energy projects. Figure 2: Optimizers allow the formation of strings with modules under very different operating conditions And bifacial photovoltaic modules, what can we say about them? As the name itself suggests, these are modules that have two sides. Bifacial photovoltaic modules capture light from both their front and back surfaces, and can offer higher power and generation rates than conventional modules, depending on the amount of light reflected at the location. Bifacial solar panels are most useful in solar power plants, where the module is spaced apart from the ground, allowing the back surface to capture a large amount of light reflected from the ground. On roofs, double-sided modules can offer some performance improvement in installations with metal roofing or, especially, in structures pitched over slabs. In the following tables we find the electrical characteristics of bifacial modules from the manufacturer Risen Energy, with nominal peak powers from 435 W to 455 W. Every photovoltaic module is specified under STC conditions (25 °C and 1000 W/m2). Traditional solar panels will always perform at or below the STC table shown in the datasheet. Bifacial photovoltaic modules, due to the additional capture of light reflected by the ground, can have a "bifacial gain," according to which the power, current, and operating voltage will be higher than those specified in the STC characteristics table. This means that a module with a nominal power of 450 W can, in practice, operate as a 585 W module if we consider a bifacial gain of 30%, as the following table demonstrates. Tables of electrical characteristics of Risen's RSM144-7-435BMDG-455BMDG modules The issue of compatibility With the gain in bifaciality, the electrical characteristics of photovoltaic modules are increased, as we mentioned above. This requires special care when specifying other components of photovoltaic systems, including power optimizers. SolarEdge, the leading manufacturer of power optimizers, issued the technical note “Application Note – Compatibility of bi-facial modules with SolarEdge power optimizers” in January 2020, which describes the correct method for selecting power optimizers for use with bifacial modules . The correct selection of the optimizer depends on the electrical characteristics of a given module. When designing a solar system with bi-facial modules, it is challenging to estimate the generation gain added by the back of the modules, especially due to the non-uniformity nature of the ground-reflected irradiance. The gain from reflected light is highly influenced by various conditions, such as geographic location, temperature, module inclination, surface area behind the modules, and so on. In order to provide design flexibility and support for a range of modules, SolarEdge power optimizers include a feature that is capable of handling the wide range of current and power expected from a bifacial module, even in extreme cases such as those mentioned above. When using bifacial modules, SolarEdge allows you to select optimizers that support the maximum power, current and voltage of the modules, considering the front electrical values (in STC) informed in the modules' data sheet. It is important to note that the optimizer warranty may be void if the power, voltage or current of the selected module in STC (without considering bifaciality gain) is above the specifications of the selected optimizers. When designing a system (manually or using a sizing tool) it is important to always make the optimizer characteristics compatible with the output characteristics of the photovoltaic module in STC declared in the module data sheet, without considering the power gain caused by nature. bifacial module. In other words, you should design the system as you always have, even if the module in practice may exceed the nominal power, current, or voltage values due to the capture of reflected light. Optimizers will be prepared to handle the gain from bifaciality, provided that the optimizer is chosen in accordance with this basic guideline. Sizing example Bifacial module specifications Power in STC (with 0% bifacial gain): 400 W; Power in STC (with 30% bifacial): 520 W; Open circuit voltage at STC: 49,7 V; Short-circuit current in STC: 10,22A; Current thermal coefficient: 0,03 ; VOC stress thermal coefficient: -0,27. Optimizer to be selected (considering two modules in series) Model (family): P850-4xxxxxx, serial number SJ5019A-xxxxxxxx; Maximum power 850 W (greater than 2 x 400 W 800 W); Maximum input voltage 125 VDC (greater than 2 x 49,7 V 99,4 V); Maximum input current 12,5 ACC (greater than 10,22 A). Inverter selected Output power (AC): 25 kW. Design considerations Maximum string power: 15,75 kW (for a 230 V to 400 V network); Maximum input power (DC) of the inverter in STC (135% oversizing): 33,75 kW; Maximum number of modules in the string: 15,75 kW / 400 W 39 (20 power optimizers); Maximum number of modules connected to the inverter: 33,750 kW / 400 W 84 (42 power optimizers). Note: The example above was taken from the document “Application Note – Compatibility of bi-facial modules with SolarEdge power optimizers”. Consult your local supplier to check the availability in Brazil of the models mentioned in the example and to verify the compatibility of other models. In conclusion, the power gain provided by bifacial modules can typically reach 30% over the module's nominal power rating. When designing a bifacial module project with power optimizers, it is initially important to ensure that the optimizer's characteristics match the photovoltaic module's STC characteristics as specified in the catalog (without considering the bifacial gain). This basic rule guarantees the integrity of the project and prevents loss of the optimizer's warranty. Following the basic rule, as shown in the example case study, the optimizer is sized with a slight power margin. The same applies to the total power of the inverter, which in this example was sized 35% above the nominal power of the modules in STC.

Compatibility between bifacial photovoltaic modules and optimizers

Compatibility between bifacial photovoltaic modules and optimizers

PVSyst: photovoltaic systems with power optimizers

PVSyst: photovoltaic systems with power optimizers

MLPE and power optimizers for photovoltaic modules

MLPE and power optimizers for photovoltaic modules

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