Medium-voltage power stations are often more flexible, cost-effective and easier to integrate into local grids than high-voltage power stations, making them ideal for distributed solar projects or regions without easy access to high-voltage transmission infrastructure. High-voltage power plants are more suitable for utility-scale generation for long-distance transmission, but are more sensitive to transmission losses and require significant upfront planning and investment. In addition, high-voltage installations require stricter safety measures, more complex protection systems and specialized personnel.
With these benefits in mind, a team of researchers from Germany’s Fraunhofer ISE are currently planning to build what they describe as the world’s first medium-voltage photovoltaic power stations, in an effort to reduce copper and aluminum consumption.
“The switch to medium voltage is an important lever for reducing the demand for copper and aluminum in large-scale photovoltaic power plants and thus for the economic viability of the projects,” says Fraunhofer ISE researcher Felix Kulenkampff. “On the one hand, doubling the voltage leads to a saving in the conductor cross-section of about 75%. Thinner cables are easier to lay and also reduce installation costs. In addition, the connection load of transformers and substations can be doubled without changing their size. In large power plants their number can be halved, leading to further savings in material, investment and installation costs.”
The team plans to build two 135 kW pilot plants in the German region of Baden-Württemberg and Rhineland-Palatinate.
“They will operate at 3 kV on the DC side and 1.2 kV on the AC side,” the Fraunhofer ISE said in a statement. “The medium-voltage PV inverter used, based on high-blocking silicon carbide semiconductors, was already developed by Fraunhofer ISE in the MS-Leikra project and is being adapted for field use.”
The project tests two string configurations: standard 1500 V solar panels with central grounding and 3 kV strings using prototype modules for higher voltages.
The researchers believe that building cost-competitive and voltage-resistant components is feasible and are working together with partners such as Pfalzwerke AG, the FEAG Group, Stäubli Electrical Connectors AG, Weidmüller Interface GmbH & Co. KG, Mersen Deutschland Eggolsheim GmbH, Prysmian Kabel und Systeme GmbH, Sumida Components & Modules GmbH, Hanwha Q Cells GmbH, Zimmermann PV-Steel Group GmbH & Co. KG, Infineon Technologies AG, Fluke Deutschland GmbH and BES new energy GmbH.
