In a state-of-the-art photovoltaic power plant with a capacity of 50 MWp, cable lengths in the three-digit kilometer range are laid. According to the International Energy Agency's Global Critical Minerals Outlook 2024, copper demand exceeds the announced supply from 2025 onwards, which is why raw material prices are expected to rise in the future. As a result, aluminum cables are already being used on a large scale. However, aluminum production causes high CO2 emissions and is already classified as a critical raw material by the EU. “The move to medium voltage is a key lever for reducing the demand for copper and aluminum in large-scale photovoltaic power plants and thus for the economic viability of the projects,” explains project manager Felix Kulenkampff from Fraunhofer ISE. On the one hand, doubling the voltage leads to savings in conductor cross-section of around 75 percent. Thinner cables are easier to lay and also reduce installation costs. In addition, the connected 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.

“All of the advantages mentioned are already apparent at low medium voltage. The costs of developing appropriately voltage-resistant components are manageable, which is why many component manufacturers are supporting us in the pilot project,” says Felix Kulenkampff.

Two pilot plants with 3 kV medium voltage

The objectives of the project are to construct and test two pilot plants in Baden-Württemberg and Rhineland-Palatinate with a connected load of approximately 135 kilowatts over a period of several months. They will be operated at 3 kV on the DC side and 1.2 kV on the AC side. 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 use in the field. Two different string connections are being tested in the project: On the one hand, the use of standard solar modules with 1500 V and center point grounding. Secondly, a 3 kV string with PV module prototypes developed for the higher voltage class. Based on their experience in planning, construction, and commissioning, the project partners ultimately want to develop a quality assurance and testing concept for medium-voltage PV systems, incorporate findings from the field into their product design, and contribute to international standardization committees.

The project partners of “PVgoesMV” are 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. They support the project by providing and further developing key components, as well as with expertise and engineering services for setup, commissioning, and monitoring.

The project, which started in December 2025, is funded by the German Federal Ministry for Economic Affairs and Energy as part of the 8th Energy Research Program “Innovations for the Energy Transition.”