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Huge quantities of raw materials, such as copper and aluminum cables, are needed for energy system conversion when connecting renewable generators to the grid. The Fraunhofer Institute for Solar Energy Systems ISE sees enormous savings potential with higher system voltages and is planning its first pilot photovoltaic power plants with this technology.
In an effort to reduce demand for raw materials amid the continued expansion of photovoltaics, the Fraunhofer Institute for Solar Energy Systems ISE is studying a promising approach to switching from low-voltage to medium-voltage level in photovoltaic power plants. .
In collaboration with industrial partners, the institute is planning its first pilot plants with this technology and aims to launch it on the market. To kick off its new field of research, “ Medium Voltage – A Resource-Efficient Way to Interconnect ”, Fraunhofer ISE will present the first medium voltage string photovoltaic inverter in the world and a medium voltage battery inverter at the Intersolar Europe 2024 fair in Munich (June 19-21).
In its MS-LeiKra project, Fraunhofer ISE developed and demonstrated the worlds first medium-voltage string photovoltaic inverter.
Image: Fraunhofer ISE
According to the institute, an additional 73 TW of photovoltaic power will need to be installed worldwide by 2050. “This will lead to increasing demand for raw materials: According to the International Energy Agencys Global Critical Minerals Outlook 2024 report, demand for copper will exceed announced supply from 2025 onwards.”
“Increasing the system voltage can help reduce this demand, since the corresponding decrease in system current can lead to considerable savings in raw materials,” explains Andreas Hensel, director of the High Power Electronics and Systems Technology group at the Fraunhofer ISE.
For example, increasing the output voltage from 800 VAC to 1,500 VAC results in a 75% saving in cable cross section for the same power. It is also often easier to run and connect smaller sections of cable, reducing installation costs. “Now that PV module costs have fallen 90% since 2010 due to technological progress and economies of scale, installation and system balancing components have become the biggest savings levers,” adds Hensel.
“The transition from low to medium voltage can also increase the output power of the subsystems: At an output voltage of 1,500 V, 10 to 12 MVA are now possible in a transformer, instead of 3 to 5 MVA by transformer that are still common today,” says Fraunhofer ISE. “Thus, fewer transformers and switchgear are needed for power plants with medium voltage interconnections. This reduces both construction and installation costs.”
The move to medium voltage has been made possible by the development of high voltage silicon carbide (SiC) components with high switching speeds. SiC components of up to 3.3 kV are currently marketed.
Last year, Fraunhofer ISE developed the worlds first medium-voltage photovoltaic (MS-PV) string inverter as part of its MS-LeiKra project and successfully put it into operation on the grid. The two-stage inverter has an output voltage of 1,500 VAC at a power rating of 250 kVA.
“We have shown that the technological course for the transition to medium voltage has been set,” says Christian Schoener, Medium Voltage project manager at Fraunhofer ISE. “Due to the enormous increase in demand for raw materials, we are convinced that the question is no longer whether medium voltage technology will be introduced, but who will be the first players in this promising market.” The institute is currently planning its first photovoltaic pilot system based on the single-phase MS-PV inverter.
During a workshop on MS-PV held in April, a European consortium was formed consisting of representatives from all areas of the large-scale photovoltaic sector. The consortium is working on establishing the technological and regulatory requirements necessary to make the leap to medium voltage technology. “As a powerful consortium open to new participants, we can together overcome existing obstacles and achieve optimization of the entire plant,” adds Schöner.
“Commercial-scale photovoltaic power plants are just the beginning: Charging infrastructure, industrial networks, large heat pumps, battery storage systems, electrolyzers and wind turbines are also interesting application areas for the lower level.” medium voltage,” explains the institute. “Higher system voltages enable considerable material, cost and space savings and open up completely new system architectures for renewable hybrid power plants, whose individual components are interconnected via medium voltage.” |
