João Murta Pina

SUPERCONDUCTING MAGNETIC ENERGY STORAGE - A Technological Contribute to Smart Grid Concept Implementation

The urgent need to solve existing problems in the electric grid led to the emergence of the new Smart Grid (SG) concept. A smart grid is usually described as an electricity network that can intelligently integrate the actions of all players connected to it in order to efficiently deliver sustainable, economic and secure electricity supplies. Smart grids should be flexible, accessible, reliable and economic, bringing great new challenges into grid management. In order to implement this concept it is necessary to consider the operation of several new devices in the electrical grid. A class of these potential devices is Superconducting Magnetic Energy Storage (SMES) that present, among other features, very fast response times. SMES devices can play a key role in helping to overcome several grids’ faults. In this paper it is described the possibility to integrate SMES into SG, and the advantages of this integration.

A Fast Algorithm for Initial Design of HTS Coils for SMES Applications

Superconducting magnetic energy storage (SMES) is characterized by low-energy density but high-power density, making this an unfeasible approach for bulk energy storage. Nevertheless, there are applications where high amounts of power must be available for a short period of time, like power quality applications. The core element of SMES is the superconducting coil. Different approaches are found in the literature considering the modeling of this component, either for design or simulation purposes. These usually consist of analytical or numerical approaches. The former allows fast results, but only considers geometric effects. The latter provides accurate results, considering, besides electromagnetic, also mechanical and thermal effects. In this paper, a review of these models is performed, and analytical models are used in an algorithm that allows optimizing equivalent inductance for a specified length of tape. Two small prototypes are fabricated, and experimental measurements carried out, in order to validate the models that are in the base of the proposed algorithm.

A test rig for thrust force measurements of an all HTS linear synchronous motor

This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductors ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

Analysis of Characteristic Hysteresis Loops of Magnetic Shielding Inductive Fault Current Limiters

Magnetic shielding inductive fault current limiters with high temperature superconducting cylinders have previously been described by a characteristic (or maximum) hysteresis loop, built from properties of their constitutive parts, which allowed predicting their behavior in electrical grids. These preliminary results were based on finite element simulations, but posterior experiments suggested limitations in the models. In order to investigate the application of these previous models to real devices, two laboratory-scale prototypes were built with different types of superconducting material in the secondary, either bulk cylinder or tape. Although the behavior of both devices is still approximately defined by a maximum hysteresis loop, differences in the shielding current response, when compared with previous model, must be incorporated in future models.

Design of a linear synchronous motor with high temperature superconductor materials in the armature and in the field excitation system

The high diamagnetism observed in high temperature superconducting (HTS) materials lead to applications involving levitation such as the linear synchronous motor (LSM). Certain features taken into account in conventional LSM design cannot be applied in the HTS case, due to these materials characteristics, such as BSCCO stiffness, when used as armature windings. Also other design features, e.g. slot skewing, which reduces the space harmonics of the air gap magnetic flux density, thus influencing motor performance, plays an important role in final cost. These and other aspects such as the thrust force or the effect of motor control through an inverter are examined in this paper, where the analytical and numerical methodologies involved in the design optimisation of a LSM demonstrator with premagnetised YBCO pellets in the field excitation system and BSCCO armature windings are described. Simulation results are also included.

Sand Pile Modeling of Multiseeded HTS Bulk Superconductors: Current Densities Identification by Genetic Algorithms

The sand pile model, in conjunction with Bean model, is often applied to describe single grain bulk superconductors. However, in several applications such as electric motors, multiseeded bulks are needed, due to the need to increase sample dimensions. In this paper, an extension of the sand pile model is presented in order to manage this type of materials. Multiseeded HTS bulk superconductors, produced, e.g., by the top-seeded melt growth process, are characterized by intra- and intergrain currents, and these are reflected in the model. However, identifying these currents from flux density measurements is not straightforward, when considering more than one grain. In fact, the number of currents increases with the number of grains, and these have to be identified from the measured field surface. A method to identify these currents based on genetic algorithms is validated with artificial data and then used in real measurements.

Numerical Design Methodology for an All Superconducting Linear Synchronous Motor

One potential advantage of the application of superconducting materials in electrical machines is the possibility to build lighter and compact devices by removing iron. These machines find applications, e.g., in systems where cryogenics is already available, or in naturally cryogenic environments. The design of motors with high temperature superconductors (HTS) presents issues unconsidered in classical machines, besides considerations on cryogenics, such as HTS brittleness or mechanical restrictions. Moreover, HTS’ electromagnetic properties also degrade due to flux density components, which arise if there is no iron to guide magnetic flux. Several aspects must thus be considered in the design stage, as applications may turn less attractive or even unfeasible. In this paper these issues are detailed, and a numerical methodology for the design of an all superconducting (without iron or conventional conductors) linear synchronous motor is presented.

Enabling rootless Linux Containers in multi-user environments: The udocker tool

This work has been performed in the framework of the H2020 project INDIGO-Datacloud (RIA 653549). The work of E.B. is supported by the Collaborative Research Center SFB676 of the DFG, “Particles, Strings and the early Universe”. The proofs of concept presented have been performed at the FinisTerrae II machine provided by CESGA (funded by Xunta de Galicia and MINECO), at the Altamira machine (funded by the University of Cantabria and MINECO) and at the INCD-Infraestrutura Nacional de Computacao Distribuida (funded by FCT, P2020, Lisboa2020, COMPETE and FEDER under the project number 22153-01/SAICT/2016).

Integration of SMES devices in power systems - opportunities and challenges

Superconducting Magnetic Energy Storage (SMES) systems are one of the superconducting technologies with envisaged applications in power systems. The flexibility of these systems allows a utilization as Energy Storage Systems (ESS) but also as power devices, for power quality applications. In the actual context of electric grids, with the emergence of the paradigm of Smart Grids, the possible applications of SMES systems are discussed, considering the actual state of the art in superconducting materials. Main envisaged applications are presented and a short comparison with other ESS is also performed, as a way to integrate SMES systems into the actual and upcoming context of power systems. Main already running or finished projects using not only standalone SMES systems but also a combination of multiple superconducting devices are also presented. Finally, a short description of concept projects using SMES systems is also given.

Towards an energy model for supporting real time building energy management

Building energy management may simultaneously integrate multiple energy areas and sources of information. The coordination of synergies allow better-informed decisions, such as performing forecasts and adjustments of energy production and storage, while adapting electrical loads to off-peak times, when energy rates are lower. This work targets the improvement and optimization of energy management operations in buildings and large complexes, by introducing a conceptual model for supporting real-time advanced reasoning and inference towards efficient energy management.