Browsing by Author "Sanz, Santiago"
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Item Conceptual design and thermal analysis of a modular cryostat for one single coil of a 10 MW offshore superconducting wind turbine(2015-12-18) Sun, Jiuce; Sanz, Santiago; Neumann, Holger; Tecnalia Research & InnovationSuperconducting generators show the potential to reduce the head mass of large offshore wind turbines. A 10 MW offshore superconducting wind turbine has been investigated in the SUPRAPOWER project. The superconducting coils based on MgB2 tapes are supposed to work at cryogenic temperature of 20 K. In this paper, a novel modular rotating cryostat was presented for one single coil of the superconducting wind turbine. The modular concept and cryogen-free cooling method were proposed to fulfil the requirements of handling, maintenance, reliability of long term and offshore operations. Two stage Gifford-McMahon cryocoolers were used to provide cooling source. Supporting rods made of titanium alloy were selected as support structures of the cryostat in aim of reducing the heat load. The thermal performance in the modular cryostat was carefully investigated. The heat load applied to the cryocooler second stage was 2.17 W@20 K per coil. The corresponding temperature difference along the superconducting coil was only around 1 K.Item Design and Testing of Real-Scale MgB2 Coils for SUPRAPOWER 10-MW Wind Generators(2016-04) Sarmiento, G.; Sanz, Santiago; Pujana, A; Merino, Jose Maria; Marino, Iker; Tropeano, Matteo; Nardelli, Davide; Grasso, Gianni; Tecnalia Research & Innovation; DIGITAL ENERGYSuperconducting MgB2 coils have a promising application niche in large wind generators. The potential implementation as field coils results in machines with smaller size and reduced weight, which is a real benefit compared to conventional nonsuperconducting alternatives. This is a key factor where the wind market demands higher power rate and more compact turbines in order to optimize capital and operational costs. Under the SUPRAPOWER project, a 10-MW direct-drive wind generator concept will be probed through an experimental validator, with superconducting rotating dc coils. For the required temperature, current density, and magnetic field, the available commercial MgB2 wire has been selected, as it is cost effective and well suited compared to other solutions. The aim of the present work is to analyze the operational conditions of MgB2 dc field coils, which are cryogen-free cooled and developed in accordance with SUPRAPOWER generator requirements. This paper deals with the design, manufacturing, and experimental results of full-scale superconducting coils.Item Development of a rotary union for Gifford-McMahon cryocoolers utilized in a 10 MW offshore superconducting wind turbine(2017-12-30) Sun, Jiuce; Sanz, Santiago; León, Andrés; Fraser, Jim; Neumann, Holger; Tecnalia Research & InnovationSuperconducting generators (SCG) show the potential to reduce the head mass of large offshore wind turbines. By evaluating the availability and required cooling capacity in the temperatures range around 20 K, a Gifford-McMahon (GM) cryocooler among all the candidates was selected. The cold head of GM cryocooler is supposed to rotate together with the rotating superconducting coil. However, the scroll compressor of the GM cryocooler must stay stationary due to lubricating oil. As a consequence, a rotary helium union (RHU) utilizing Ferrofluidic® sealing technology was successfully developed to transfer helium gas between the rotating cold head and stationary helium compressor at ambient temperatures. It contains a high-pressure and low-pressure helium path with multiple ports, respectively. Besides the helium line, slip rings with optical fiber channels are also integrated into this RHU to transfer current and measurement signals. With promising preliminary test results, the RHU will be installed in a demonstrator of SCG and further performance investigation will be performed.Item Estimation of hysteretic losses for MgB2 tapes under the operating conditions of a generator(2016-02-02) Vargas-Llanos, Carlos Roberto; Zermeño, Victor M. R.; Sanz, Santiago; Trillaud, Frederic; Grilli, Francesco; Tecnalia Research & InnovationHysteretic losses in the MgB2 wound superconducting coils of a 550 kW synchronous hybrid scaled generator were estimated as part of the European project SUPRAPOWER led by the Spanish Fundación Tecnalia Research & Innovation. Particular interest was given to the losses caused by the magnetic flux ripples in the rotor coils originating from the conventional stator during nominal operation. To compute these losses, a 2D finite element analysis was conducted and Maxwell’s equations written in the H-formulation were solved considering the nonlinear material properties of the conductor materials. The modeled tapes are made of multiple MgB2 filaments embedded in a Ni matrix and soldered to a high purity copper strip and insulated with Dacron braid. Three geometrical models of single tape cross sections of decreasing complexity were studied: (1) the first model reproduced closely the actual cross section obtained from tape micrographs. (2) The second model was obtained from the computed elasto-plastic deformation of a round Ni wire. (3) The third model was based on a simplified cross section with the superconducting filaments bundled in a single elliptical bulky structure. The last geometry allowed the validation of the modeling technique by comparing numerical losses with results from well-established analytical expressions. Additionally, the following cases of filament transpositions of the multi-filamentary tape were studied: no transposition, partial and full transposition; thereby improving understanding of the relevance of the tape fabrication process on the magnitude of the determination of ac losses. Finally, choosing the right level of geometrical detail, the following operational regimes of the machine and its impact on individual superconducting tape losses in the rotor were studied: bias-dc current, ramping current under ramping background field and magnetic flux ripples under dc background current and field.Item Experimental Study and Simulation of Quench in MgB2 Coils for Wind Generators(2016-01-18) Sanz, Santiago; Sarmiento, G.; Pujana, Ainhoa; Merino, Jose Maria; Tropeano, Matteo; Nardelli, Davide; Grasso, Gianni; Sun, Jiuce; Toral, Fernando; Marino, Iker; Tecnalia Research & Innovation; DIGITAL ENERGYIn the frame of the European Union (EU) founded SUPRAPOWER Project, MgB2 conduction-cooled coils are foreseen to be used in the rotor of synchronous wind turbine generators. As a result, a conceptual design of a 10 MW superconducting (SC) generator will be made and a Rotating Magnetic Validator (RMV) will be constructed and tested, with two rotating SC coils. The main dimensions and working conditions will be kept in the RMV and in the 10 MW generator. The RMV has been conceived is such a way that it can be transformed in a generator. Numerical quench simulations have to be performed in order to design a suitable quench protection system. Due to the uncertainty of some material properties and its importance for the machine operation, an experimental validation must be performed in order to resolve discrepancies. Under this premises, a full size MgB2 double pancake coil have been manufactured and instrumented to trigger a controlled quench.Item Lightweight MgB2 superconducting 10 MW wind generator(2015-12-21) Marino, Iker; Pujana, Ainhoa; Sarmiento, G.; Sanz, Santiago; Merino, Jose Maria; Tropeano, Matteo; Sun, Jiuce; Canosa, T.; Tecnalia Research & Innovation; DIGITAL ENERGYThe offshore wind market demands a higher power rate and more reliable turbines in order to optimize capital and operational costs. The state-of-the-art shows that both geared and direct-drive conventional generators are difficult to scale up to 10 MW and beyond due to their huge size and weight. Superconducting direct-drive wind generators are considered a promising solution to achieve lighter weight machines. This work presents an innovative 10 MW 8.1 rpm direct-drive partial superconducting generator using MgB2 wire for the field coils. It has a warm iron rotor configuration with the superconducting coils working at 20 K while the rotor core and the armature are at ambient temperature. A cooling system based on cryocoolers installed in the rotor extracts the heat from the superconducting coils by conduction. The generator's main parameters are compared against a permanent magnet reference machine, showing a significant weight and size reduction. The 10 MW superconducting generator concept will be experimentally validated with a small-scale magnetic machine, which has innovative components such as superconducting coils, modular cryostats and cooling systems, and will have similar size and characteristics as the 10 MW generator.Item Tensile and Bending Strain Tolerance of Ex Situ MgB2/Ni/Cu Superconductor Tape(2015-04-01) Kovac, P.; Kopera, L.; Melisek, T.; Sarmiento, G.; Sanz, Santiago; Brisigotti, S.; Nardelli, Davide; Tropeano, Matteo; Kováč, Pavol; Melišek, Tibor; Sanz Castillo, Santiago; Tecnalia Research & InnovationThis paper describes the strain tolerance of MgB2/Ni/Cu tape produced by Columbus Superconductors subjected to tension and bending stress. A tension test instrument with freestanding sample was used for stress-strain, I-c-stress, and I-c-strain characteristics at liquid helium temperature. Bending of MgB2/Ni/Cu tape to variable diameters was done at room temperature and in two directions: 1) with a Cu strip on the outer surface (Cu out) of a bent sample; and 2) with a Cu strip on the inner side (Cu in). I-c-bending strain characteristics were measured at 4.2 K and external field B = 6 T oriented perpendicularly to the sample's width. Obtained results have shown the strain limits, which should not be exceeded during the winding process of superconductor containing brittle MgB2 filaments.