Description

Solar power plant (SPP) investments, which increased rapidly in the country in 2015, focused more on land applications than roof applications, contrary to expectations in the sector. However, up to now, many rooftop applications have been put into practice, which can be exemplified by specialized engineering companies, especially industrial facilities. One of these example applications is the 1 MWp SPP implemented by our customer Vels Energy on the roof of an industrial facility in 2017 in the Kahramankazan district of Ankara province.

EXPECTATION

Our client was aiming to develop innovative solutions at every point of the plant while designing this project, which is one of the larSPPt rooftop SPP investments in the region. The mounting system was built without holes in the rooftop with special apparatuses other than the traditional screwed methods. For inverter part, unusual center type inverter was wanted to use for rooftop SPP investment in Turkey and it is not established before for this type project. Because roof surface areas in industrial facilities do not mostly look in different directions, centralized inverter is not preferred in roof applications. At this point, our client was contacted to find an innovative solution.

APPLICATION

The phenomenon of not using a central inverter in roof applications had to have a single “MPPT” (1) input. For this reason, it was not possible to obtain maximum power from the photovoltaic (PV) modules which were mounted so as to look at different directions. Because conventional central inverters have only one MPPT input, all PV modules are connected to a single MPPT input, and the inverter produces according to PV modules that are exposed to lower radiation. Therefore, the SPP production curve was adversely affected by this situation.

When we consider our client’s project; PV modules could be installed on the roof area of the industrial plant with a total of 1 MWp power. When the roof area where the PV modules are to be mounted is examined according to its structure and position, it is determined that the modules will be mounted with two groups separated on the northeast-southwest axis with equal strength. Thanks to the “Friem Recon Line 2.30H1” series modular central inverters, which have 2 MPPT inputs at this point, the forces from the (north and south) panel assemblies of both groups are connected to two separate MPPT inputs via “DC String Boxes” (2). During the testing phase and before the commissioning phase, it was seen that both modular central inverter modules achieved maximum power from both sides of the PV modules and that the SPP production curve reached the ideal point.

(1): The MPPT term is the ‘Maximum Power Point Tracker’. As can be understood from the name, the power obtained from certain periods ensures that it is sent to the load by following the peak points. According to this definition, strength in our example application; the power obtained from the photovoltaic modules, and the load is the inverter itself.

(2): A DC electric panel that serves to sum up (parallels) the cables arising from the lines formed by the PV modules and to form two main cable lines with thick sections.

Result

In this example application, as Aktif Group, we have demolished the central inverter taboo for roof SPP projects and opened new way to these type projects. Thanks to the multi-MPPT feature of the Friem Recon Line family of modular central inverters, we have reached the best production curve to get from the PV modules mounted in different directions, according to the hours of maximum radiation. However, we have provided the most appropriate solution for the cost of investment and have provided a useful system to the end user, reducing the probability of failures to a minimum.