08/02/2023
Source: Energy & Management Powernews
To enable bidirectional charging to be used on a broad scale, a consortium led by Fraunhofer IAF is researching innovative charging technologies with industry.
Bidirectional charging enables electric vehicles to be both charged and discharged as required. Thus, e-cars can serve as mobile electricity storage and contribute to the flexibilization of the energy system. To ensure that bidirectional charging can be used on a broad scale, a consortium led by the Fraunhofer Institute for Applied Solid State Physics (IAF) is researching innovative charging technologies. In the recently launched "GaN4EmoBiL" project, the partners are developing new semiconductor, device and system technologies for the 800-V class, the IAF said.
In this project, partners from research and industry are working together to develop a cost-effective and efficient bidirectional charging technology for electric vehicles. Consumers could use this power for other electrical devices or deliver it to the power grid, contributing to energy security. Previous technological approaches have lacked intelligent and cost-effective bidirectional charging systems to connect batteries, the grid, local generators and consumers with high efficiency and power density, according to the IAF.
Involved in the project, in addition to the IAF, are the University of Stuttgart, Robert Bosch and Ambibox. The consortium's goal is to demonstrate an intelligent and cost-effective bidirectional charging system using new semiconductor devices, device concepts and system components. The three-year project is funded by the German Federal Ministry of Economics and Climate Protection (BMWK) as part of the "Elektro-Mobil" program.
"Our project aims to connect batteries, renewable energies and electrical consumers economically and flexibly," explained Stefan Mönch, project coordinator from IAF. Through bidirectional charging solutions, the previously unused batteries of parked electric vehicles could contribute more to making the energy system more flexible and avoiding CO2 emissions in the future. Etienne Tchonla, head of R&D Strategy at Ambibox, said, "Efficient, small-scale and smart charging infrastructures in electric mobility will help address societal challenges in the future."
To date, existing technology has been inadequate
First medium-power bidirectional DC wall boxes for batteries up to 800 V have so far used power semiconductor devices that are not yet optimal for this application. They were either efficient but expensive (made of silicon carbide) or inexpensive but less efficient (made of silicon). Today's available 650-V transistors made of gallium nitride on silicon (GaN-on-Si) are inexpensive and efficient, he said, but require complex circuitry because the dielectric strength is not sufficient.
In order to integrate as many batteries as possible bidirectionally, the cost, efficiency and compactness of the charging solutions would have to be significantly improved. To achieve this, the project partners are researching new semiconductor solutions as a first step. They want to realize a new low-cost GaN technology on alternative substrates (for example, sapphire) that enables inexpensive and efficient 1200-V transistors. Based on this, they will develop new system components (bidirectional charging cable and charger) and investigate their reliability for greatly increased operating durations.
At the end of the project, demonstrators are expected to fill the research and development gap that currently exists between cost, efficiency, compactness, functionality, power class and voltage class (800 V batteries). In addition, the consortium aims to promote knowledge transfer between universities, research institutions and industry, train young scientists and secure national know-how in the field of electromobility.
Information from the IAF on bidirectional charging is available on the Internet.
Author: Susanne Harmsen
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