Fraunhofer Institute for Solar Energy Systems ISEBy 2050, a global increase of approximately 73 terawatts of installed photovoltaic capacity is expected. This planned expansion will require significant amounts of raw materials, including copper and aluminum for cables and transformers. Raising the PV system to medium voltage has the potential to significantly reduce resource use and investment costs. The project aims to demonstrate with two pilot plants that the transition to medium voltage for industrial PV power plants is technically feasible and economically viable. The team is supported by manufacturers for all key system components, from medium voltage cables to PV connectors.
Construction and Operation of the World’s First Medium Voltage PV Demonstration Plants with a 3 kV String Inverter
PVgoesMV
Medium voltage string inverter for future industrial PV power plants. Power: 135 kW, AC voltage: max. 1500 V, DC voltage: max. 3 kV.
Initial Situation
In a state-of-the-art PV power plant with an installed capacity of 50 MWp, cable lengths are in the hundreds of kilometers. According to the Global Critical Minerals Outlook 2024 by the International Energy Agency (IEA), copper demand is expected to exceed the announced supply starting in 2025, leading to rising raw material prices in the future. As a result, aluminum cables are already being used on a large scale, despite the higher processing efforts. On one hand, aluminum production is associated with significantly higher CO2 emissions, and on the other hand, aluminum is already classified as a critical raw material by the EU.
Development of primary copper supply requirements according to IEA.
Objective
The transition to medium voltage is a crucial lever to massively reduce the demand for copper and aluminum in PV power plants. Doubling the voltage leads to savings in conductor cross-section of approximately 75%. Thinner cables are easier to install and additionally lower installation costs. Furthermore, the rated power capacity of transformers and substations can be doubled while maintaining the same size. This allows to cut their number in half in large power plants, resulting in further savings in materials, investment, and installation costs.
All of the mentioned advantages already arise at low medium voltage. The expenses for designing components with suitable electric strength are manageable, which is why many industrial partners support us.
Minimal wire size for 250 kVA at different voltage levels.
Approach
However, suitable system components are not yet available on the market and adapted standards are still in the draft stage. The aim of the project is therefore to develop suitable components with the help of industry partners and to use them to set up and operate two pilot plants. Connected load: approx. 135 kW, DC voltage: max. 3 kV, AC voltage: 1.2 kV.
The medium voltage PV inverter was already developed by Fraunhofer ISE in the MS-Leikra project and will be adapted for field use. Two different string configurations will be tested: the use of standard PV modules with +/- 1500 V and midpoint grounding, as well as a 3 kV string with corresponding PV module prototypes. Based on the experiences gained in planning, construction, and commissioning, a quality assurance and testing concept for medium voltage PV systems will ultimately be developed.
Schematic of a 3 kV power plant with standard PV modules and neutral point grounding.
Project Partner
- Pfalzwerke AG
- FEAG Forchheim GmbH
- 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-Stell Group GmbH & Co. KG
- Infineon Technologies AG
- Fluke Deutschland GmbH
Funding
The project "PVgoesMV" is funded by the Federal Ministry for Economic Affairs and Energy (BMWE) as part of the 8th Energy Research Program of the Federal Government "Innovations for the Energy Transition".
