Superconducting Ferromagnetic Metamaterials Enabling the Development of Resilient High Voltage / High Current Transmission Systems

The need for a technological breakthrough in high voltage power transmission lines for resilient and environmentally friendly urban grids, as well as for the transport of power over long distances from renewable energy sources to load centers, is an undeniable reality that needs to be addressed today. Of course, this is the case if we want to cope with the demand of electric power and massive electric vehicle use expected in the next few decades. SUPERFEM responds to this need by proposing a new set of novel metamaterials which brings together the outstanding electric characteristics of High Temperature Superconducting materials (HTS) with, the shielding magnetic properties of Soft Ferromagnetic layers (SFM), introducing them in the design of power conductors for HVDC and three-phase HVAC networks with nearly zero magnetic leakages and power losses. It is already known that although the HTS conductors offer unbeatable performance features for each one of these networks, their benefits are certainly true when single cables or isolated current-phases are considered, as the large inductive losses produced by any neighbouring cable can be neglected. However, as the electric utility industry for generation and end usage are almost exclusively AC, for three phase power systems or DC systems which will have to share the right of way with them, the reality is that the major factor contributing to the operational costs of HTS networks is the losses produced by the magnetic field created by each one of the other cables, a situation that can only be understood by the numerical modelling of these kind of applications, as the occurrence of hysteretic power losses needs to be calculated to the fore.

For the modelling of real power applications of HTS single- and three-phase power transmission lines, a conductor is more than just the HTS material, and in this sense two major types of insulation schemes for retrofitting underground power transmission lines with HTS conductors, the Warm dielectric (W-) and Cold dielectric (C-) designs will be considered, with the novel feature of adding HTS/SFM metastructures to reduce the hysteretic losses of the entire system. In a first stage, we will embed a multifilamentary HTS cable into SFM sheaths, such that the magnetization losses produced by the concomitant action of co-axial cables is reduced or, virtually eliminated, without the need of having further HTS shields which also serve as an additional source of power losses. Similar metastructures have been demonstrated to enhance the mechanical properties of HTS cables, but its electromagnetic behaviour for different superconducting and ferromagnetic composites and their overall performance under three-phase or DC multiconductor configurations is unknown. We aim to study different magnetic sheaths for HTS/SFM warm conductors into the actual commercial market of SFMs for power applications. In this sense, 33 different SFM materials with relative magnetic permeability ranging from ~1 to 35000 will be considered as part of this project, leading to the world's first map of AC-losses for single phase HTS/SFM transmission lines. This will be then extended to triaxial and triad designs of warm and cold dielectric transmission lines, finding the best route of investment for this technology with a significant cost reduction and efficiency gain as the primary targets.

The research proposed in this project is the first of its kind on the search of energy-efficient and resilient transmission networks, which in the long term aims to mitigate costs of grid reinforcement, replacement and upgrade of fault limiters and other power management devices, with greater levels of public acceptance and lowering of installation costs, due their reduced need for use of the right of way in highly populated areas.

Opening up the deployment of solutions for improving the flexibility, resilience, and available capacity of the UK and pan-European electricity networks at high voltage levels, in coexistent DC and AC grids, is one of the greatest challenges that SUPERFEM aims to tackle. Its impact will be reflected by the developing of advance computational platforms for novel and cost-effective designs of multiconductor and three-phase power transmission lines taking advantage of the benefits invoked by the so-called HTS/SFM metastructures. In this sense, not only a large range of academic beneficiaries can be identified due to the interdisciplinary nature of this proposal, but in a long term major economic and societal impacts should be attained by the de-risking of public investments on the upgrading of the transmission and distribution networks, through the identification, optimization, and computational validation of highly efficient superconducting wires.

The list of our potential economic and societal beneficiaries is vast and well connected. Immediate economic impacts are being recognised within the grid stakeholders, and operators addressing the integration of renewables and other new electricity producers and users. At the same time we expect major societal impacts to be derived by the maintaining or balancing of power flows, the easier installation and voltage control strategies that can be implemented with the superconducting cables, and the maintaining or enhancing service quality, reliability and security of the power system.

In SUPERFEM, the semi-analytical methods and the computational tools to be developed for the understanding of conventional high temperature superconducting cables for HVDC and HVAC systems, together with the devising of new cable architectures supported by HTS/SFM metastructures, will be both used to demonstrate the viability of these technologies in urban or suburban networks, currently experiencing serious limitations on their right-of-way. The transmission cables to be developed by SUPERFEM weigh far less per unit length than their conventional counterparts. This fact allows an easier an cost-effective installation of overhead transmission lines, with their major beneficiaries being located in rural areas. However, we anticipate that the outcomes of our study, which all will be released through high impact journals and our equal participation in major energy conferences, will all have a greater impact on the upgrading of architectures for underground multiconductor and three-phase power networks. This is certainly our case, unless overhead rights-of-way costs will become sufficiently low, and the growing public resistance to overhead lines due to aesthetic issues and concerns for property values is ignored by policy-makers and government agencies, such that our designs for single phase isolated transmission lines might develop automatic paths of impact in the devising of overhead transmission lines.

We will simultaneously help to develop the competitiveness of UK in the ultimate upgrading of the power grid, which is currently challenged by the development of superconducting power transmission networks in cities such as Tokio-Japan, Essen-Germany, and the cities of Chicago and New York in the USA. A further reduction of the environmental and electromagnetic pollution impacts that is created by the extended use of conventional cables is also one of the primordial benefits of our HTS/SFM technology. For this reason, since the early stage of development, SUPERFEM focus on the reduction of magnetic leakages, and the further estimation of total hysteretic losses in a large set of novel transmission cables. Altogether, our results will work as a benchmark for the facilitation of cryogenic facilities capable to stand for the continuous operation of direct or alternating current in the superconducting power cables, and the mitigation of capital and operational costs for grid modernization.