Hybrid Storage SWIVT

The hybrid storage system SWIVT was built within the framework of the publicly funded projects SWIVT I and SWIVT II and serves to test the hybrid storage concept developed at the IMS consisting of lithium-ion battery and kinetic energy storage in outer rotor design. The synergistic combination of the two storage technologies creates a novel storage system that has improved characteristics in terms of aging, losses and available energy content. The testing takes place under realistic conditions in the living lab SWIVT district.

The hybrid storage system consists of a kinetic and an electrochemical energy storage system, which are connected via a common DC bus link. This interconnection makes it possible to use a common grid-sided inverter and thus reduce the number of components. The kinetic storage is an outer rotor design specifically developed at the IMS for the use in the factory. It consists of a CFRP rotor that rotates at speeds of up to 18,000 rpm to store energy. The energy is converted via a permanent magnet synchronous motor and fed into the DC bus of the hybrid system via a modern inverter (switching frequency: 12 kHz). The rotor is actively magnetically levitated to minimize maintenance and wear. In addition, the contact-less bearing enables operation in vacuum, which in turn minimizes air friction losses. The described storage system is characterized by its high cycle life and electrical power. The electrochemical storage is a lithium-ion battery from the manufacturer Akasol AG. The battery is characterized by a high energy density and is integrated into the DC bus via a DC/DC converter.

During operation, the requested electrical power must be split between the two storage systems. Appropriate algorithms to determine this spilt are currently the subject of research at IMS and can be tested on the real hybrid system. The hybrid storage system can pursue a wide variety of goals in the district to generate added value. Particularly noteworthy in the smart grid context are the peak shaving of EV charging peaks, the increase of own-consumption of locally produced energy and the reduction of forecast deviations in the load prediction. For this purpose, the storage system is fully connected to the district’s energy management via an industrial controller and exchanges high-frequency information.

SWIVT II

  • Investigation of the application of hybrid storages in modern residences
Maximum Power 100 kW
Capacity 2,4 kWh
Rotor mass 180 kg
Rotor outer diameter 430 mm
Rotor inner diameter 290 mm
Rotor length 850 mm
Speed range 9,000 – 18,000 U/min
Nominal power 30 kW
Capacity 49 kWh
Mass 620 kg
Voltage range 389 – 605 V
Storage material Lithium nickel manganese cobalt oxides (Li-NMC)
Cycle Life 6800 Cycles