Resource efficiency through medium voltage in photovoltaics
Fraunhofer ISE is revolutionising photovoltaics through the use of medium voltage in large-scale PV power plants. This innovative technology saves raw materials, reduces installation costs and increases system performance. Pilot projects and a market launch are already being planned.
The conversion of the energy system requires considerable quantities of raw materials such as copper and aluminium. One promising approach to saving these resources is the transition from low voltage to medium voltage in renewable energy production. The Fraunhofer Institute for Solar Energy Systems ISE has identified enormous savings potential through higher system voltages, particularly for large-scale photovoltaic power plants, and is planning initial pilot projects and a broad market launch.
Advantages of higher system voltages
Increasing the system voltage from 800 VAC to 1,500 VAC reduces the cable cross-section by around 75 per cent. This makes installation and connection easier, which reduces installation costs. Andreas Hensel, Group Manager “High Power Electronics and System Technology” at Fraunhofer ISE, emphasises the potential savings: “Now that PV module costs have fallen by 90 percent since 2010, installation and balance-of-system components now offer the greatest savings levers.”
In addition, the output of the subsystems can be increased by switching to medium voltage. At a voltage of 1,500 V, 10 to 12 MVA are already possible in one transformer instead of the 3 to 5 MVA that are common today. This reduces the number of transformers and switchgear required, which further reduces construction and installation costs.
Technological advances and initial successes
Progress in medium-voltage technology has been made possible by the development of highly blocking silicon carbide components with high switching speeds. SiC components up to 3.3 kV are now ready for the market. In the “MS-LeiKra” project, Fraunhofer ISE developed and successfully commissioned the world’s first MS-PV string inverter in 2023. The inverter achieves an output voltage of 1,500 VAC with an output of 250 kVA. “Technologically, the course has been set and it is now a question of who will be the first players in this promising market,” says Christian Schöner, Project Manager “Medium Voltage” at Fraunhofer ISE. A first photovoltaic pilot system based on this inverter is already being planned.
Cooperation for the breakthrough
In April, a European consortium was formed that brings together representatives from all trades involved in a large-scale PV power plant. The aim is to jointly investigate and overcome the technological and standardisation requirements for the leap to medium voltage. “As a powerful consortium, we can tackle the existing hurdles together and achieve optimisation for the entire power plant,” explains Christian Schöner.
Future prospects and areas of application
Large-scale PV power plants are just the beginning. Medium-voltage technology also offers potential for charging infrastructures, industrial grids, large heat pumps, battery storage systems, electrolysers and wind turbines. In addition to considerable material, cost and space savings, higher system voltages also enable new system architectures for renewable hybrid power plants. These can be linked together via the medium voltage and thus ensure an efficient and sustainable energy supply.