Rainer Gehring

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.

The Cryogenic Pumping Section of the KATRIN Experiment

In order to determine the absolute scale of the neutrino mass with a sensitivity of 0.2 (90% Confidence Level), the Karlsruhe Tritium Neutrino experiment (KATRIN) operates a series of superconducting magnet systems, which guide the electrons adiabatically from the source of tritium beta-decay to the detector within a magnetic flux of 191 . The 7 m long Cryogenic Pumping Section (CPS) is designed as the final barrier of tritium circulation. It has to reduce the tritium partial pressure below Pa in order to limit the background count rate in the measurement. To achieve this, the tritium entering the CPS must be adsorbed onto a pre-condensed argon layer on the inner surface of the beam tube at a temperature of 3 K. The zigzag arrangement of the magnet modules increases the efficiency of tritium retention, but makes the transition of the magnetic flux rather complicated. The solenoids are operated in persistent mode with a central magnetic flux density of 5.6 T. The field drop of the magnet has to be less than 0.1% over one month. This report describes the design of the CPS and the current status of the project.

SMES compensator with a toroidal magnet system

Disturbances generated in the power system by the feedback of fluctuating loads can be reduced by application of a fast reacting SMES based power compensator. A demonstrator using a NbTi solenoid had been developed and tested in the field at an earlier time. This paper reports on the second step, which is the replacement of the solenoid by a ten coil toroid with low fringing magnetic field. The paper concentrates on Europes first toroidal SMES in operation. Its design, construction, and test are described. A maximum of 420 kJ energy was stored, when the magnet system reached the short sample current value after one training step.

The Windowless Gaseous Tritium Source for the KATRIN Experiment

For the direct, model-independent measurements of the absolute neutrino mass in an unprecedented sensitivity of 0.2 eV/c2 the Karlsruhe Tritium Neutrino (KATRIN) experiment needs among other components a chain of superconducting magnet systems serving different purposes. The most complicated part of these magnets is the windowless gaseous tritium source (WGTS). Different calibration modes require that an electron beam from an e-gun is scanned over the active area. This scanning requires sets of dipoles allowing a deflection of the beam in horizontal and vertical direction. In order to reach the high precision in the measurement of the neutrino mass the operation of the source system must have extremely stable conditions. The magnetic field will have persistent mode operation and the beam tube must have a very sophisticated cooling system to keep the temperature within an extremely narrow range around the operating temperature of 30 K. This paper describes some of the design aspects of the WGTS.

The KATRIN magnet system

For the proposed neutrino experiment KATRIN a new magnet system has to be designed. The superconducting magnet system has to guide the electrons originating from tritium beta decay from the source through the spectrometer to the detector. In order to determine the neutrino mass by measuring the electron energy spectrum the magnet system has to transport the electrons adiabatically along the 70 meter long experiment. The typical field of the system will be 5.6 T. Different sections of the magnetic transport system serve additional purposes so that a high precision measurement can be performed. The overall design as well as some details on different sections are presented in this paper.

Status of the Magnets of the Two Tritium Pumping Sections for KATRIN

The next generation neutrino mass experiment KATRIN (Karlsruhe Tritium Neutrino experiment) uses a series of superconducting magnet systems, which guide the electrons from tritium beta-decay adiabatically from the source to the detector within a magnetic flux of 0.0191 . The electron transport and tritiuAm pumping sections contain two complex magnet systems; the Differential Pumping Section (DPS2-F) and the Cryogenic Pumping Section (CPS) that are designed with a central magnetic flux density from 5 T to 5.7 T for persistent-mode operation. Each system has a series of superconducting solenoids in a zigzag arrangement that is designed to enhance the tritium pumping efficiency. The 7 m long DPS2-F was commissioned at the end of 2010 and the magnetic performance of the DPS2-F was accepted for the KATRIN experiment. The DPS2-F was operated for more than 325 hours in persistent-mode to investigate long term field stability, which is required to stay within 0.01% at the nominal field for a 60-day measurement run. All seven modules of the CPS were manufactured and successfully cold-tested.