Michael Sander

LIQHYSMES—A Novel Energy Storage Concept for Variable Renewable Energy Sources Using Hydrogen and SMES

A new energy storage concept is proposed that combines the use of liquid hydrogen (LH2) with Superconducting Magnetic Energy Storage (SMES). The anticipated increase of the contribution of intermittent renewable power plants like wind or solar farms will substantially increase the need for balancing demands and supplies from seconds to several hours or even days. LH2 with its high volumetric energy density is the prime candidate for large scale stationary energy storage but balancing load or supply fluctuations with hydrogen alone is unrealistic due to the losses related to the re-conversion into electricity and also due to the response times of the flow control. To operate the hydrogen part more steadily some short-term electrical energy storage will be needed. Here a SMES based on High Temperature Superconductors (HTS) is proposed for this purpose which could be operated in the LH2 bath. With this approach the cryogenics-related costs for the SMES are widely cut. The concept is introduced. Simple simulations on the buffering behavior and comparisons of different plant types are presented.

LIQHYSMES - size, loss and cost considerations for the SMES - a conceptual analysis

A new energy storage concept for variable renewable energy, LIQHYSMES, has been proposed which combines the use of liquid hydrogen (LH2) with superconducting magnetic energy storage (SMES). LH2 with its high volumetric energy density and, compared with compressed hydrogen, increased operational safety is the prime energy carrier for large scale stationary energy storage. But balancing load or supply fluctuations with hydrogen alone is unrealistic due to the response times of the flow control. To operate the hydrogen part more steadily, additional short-term electrical energy storage is needed. For this purpose a SMES based on coated conductors or magnesium diboride MgB2 operated in the LH2 bath, is proposed. Different solenoidal and toroidal SMES designs for the 10 GJ range are compared in terms of size and ramping losses. Cost targets for different power levels and supply periods are addressed, taking into account current developments in competing short-term storage devices like super-capacitors, batteries and flywheels.

Pulsed magnetization processes for HTS bulk components

Magnetization experiments using pulsed Cu coils were carried out on YBCO rings employing multi-pulse processes with different peak fields and pulse durations. Trapped magnetic flux profiles were recorded, and the shapes and absolute values of the remanent magnetization are discussed in terms of the dynamics of such pulsed magnetization processes. While Beans model with a constant current density J=J/sub c/ describes quasi-stationary processes well, in the pulsed magnetization the transient current density clearly exceeds J/sub c/ and leads to more complex flux flow effects.

Finite Element Design and Magnetization Issues of Ring-Shaped Cryo-Permanent Magnets

Trapped peak magnetic fields beyond 15 T obtained for melt-textured 123-High-Temperature Superconductor (HTS) bulk cylinders, make these materials highly attractive for cryo-permanent magnets (CPM). However, to in-situ magnetize such HTS bulk parts using pulsed copper coils, and, in particular to reduce the required peak magnetic field, is a key issue for turning the proven material performances into practical magnetic devices. Novel concepts like the injection-current assisted pulsed magnetization of ring-shaped CPMs are needed. Based on the modeling of the superconducting HTS bulk properties and finite element designs this approach is investigated semi-quantitatively. A still simple but very compact design taking into account all components of the resonant structure, has been chosen. Time evolutions of magnetic field profiles are presented. The results reflect the complexity of such highly dynamic and nonlinear magnetization processes. Comparisons are made for two different multi-pulse sequences without and with current injection. The latter obviously always leads to a higher trapped magnetic flux. Thus the presented model calculations gives confidence that based on further optimizations even trapped magnetic field profiles of les 5 T over ges 10 cm can be achieved with pulsed copper coils