Retrospective and perspectives of the superconducting magnetic levitation (sml) technology applied to urban transportation

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INTRODUCTION

All big steps in the evolution of mankind can be related with the use in large scale of a new material to make objects. For instance: wood, bones, flint stones, iron, brass, steel. During the last century, the invention of the controlled semiconductor, in 1947, by Bardeen, Schockley and Brattain changed the world and inaugurated a new era that deserves to be referred in the future as the semiconductor era. Nowadays, a great variety of available new materials turns it difficult, even impossible, to select one to characterize the period, e.g.: graphene, carbon fiber, glass fiber, nanomaterials, superconductors and permanent magnets.

The Superconducting Magnetic Levitation (SML) technology is based on the use of high critical temperature superconductors (HTS) and rare earth permanent magnets, that dates back to 1987 [1, 2]. The availability of these materials for commercial applications, as expected, took some years. Therefore, the first prototypes of SML MagLev appeared at the turn of the century, practically 40 years later than the available prototypes of EML and EDL MagLev vehicles.

Disregarding small demonstrations, the first man loaded example of SML has been presented in Chengdu, by Wang and his research group [3] in 2002. This example was not only improved by Wang’ fellow students [4, 5], but was also followed by prototypes in Dresden, Germany [6] and Rio de Janeiro, Brazil [7, 8]. These initial systems operated inside the laboratory, in controlled environmental conditions and just for demonstration. The first and until today the single prototype that operates outdoors, presenting the conditions of a real transportation system, is the MagLev-Cobra project, that will be described in the following.

THE MAGLEV-COBRA VEHICLE

The prototype was inaugurated on the 1^st October 2014, the last day of the 22^nd International Conference on Magnetically Levitated Systems and Linear Drives. The conference participants were able to ride in the vehicle and test the system, which, at that time, still had some restrictions of operation as a recently inaugurated project.

Fig. 1. The last day of MagLev Conference in 2014

 

After one year of improvements, regular demonstrations, every Tuesday, started to visitors. The line is 200 meters long and the vehicle can carry 20 passengers at a speed of 12 km/h. Until today, more than twelve thousand persons experienced the ride [9, 10].

 

Fig. 2. The 200 meters long elevated line of MagLev-Cobra

 

The graphical abstracted depicted in Fig. 3 summarizes the technology and a figure says more than thousand words.

 

Fig. 3. Graphical abstract of the MagLev-Cobra project

 

NASA´s TECHNOLOGY READINESS LEVELS 

According to the Technologic Readiness Level [11, 12] proposed by NASA and summarized in Table 1, the MagLev-Cobra has reached TRL7.

 

Table 1. NASA´s Technology Readiness Levels

Level	Description	Main characteristic
TRL1	Basic principles observed and reported	Small scale Proof of concept
TRL2	Technology concept and/or application defined
TRL3	Proof of concept validation
TRL4	Validation in laboratory environment	Full scale Laboratory environment
TRL5	Validation in a relevant environment
TRL6	Validation in a relevant final environment	Full scale External environment
TRL7	Validation in an operational environment
TRL8	“Mission qualified” trough test and demonstration	First product
TRL9	“Mission proven” trough successful operations

 

In fact, for the large scale commercialization, which is not usually the main objective of NASA, a 10^th level should be added, as proposed in Table 2.

 

Table 2. A new Technology Readiness Level to encompass the commercialization

Level	Description	Main characteristic
TRL10	Production, sales and marketing chain established	Series production

 

The efforts to reach each level increases considerably at each step. The number of person engaged in the activity and the amount of invested money progress geometrically at a rate greater than two. Therefore, to turn the SML Technology a final product, i.e. to reach TRL10, Brazil and China established recently a cooperation named “China-Latin American United Laboratory for Rail Transportation”.

APPLICATION NICHE

The main cost of the SML technology rests on the Permanent Magnetic (PM) Rail. Since high speed implies necessarily large distance, which would represent a huge cost on PM, the application niches of SML are short distances, low speed (~70 km/h) urban transportation. For such applications, the EDL technology, which requires velocity to achieve levitation, does not offer a great appeal. In fact, presently, all commercially operated urban MagLev systems (HSST in Japan since 2005, ECO-Bee in South Korea since 2016, and Changsha and Beijing lines in China, since 2016 and 2017, respectively) uses EML technology.

The authors of this paper support that the SML method offers advantages in comparison with the EML solution for application in urban areas. The following items will support this statement based on two points: the simplicity and robustness of the levitation method; the simple and slimmer civil engineering construction.

COMPARISON EML x SML: LEVITATION SYSTEM

The SML technology is intrinsically stable, just the PM rail and the cryostats (the “wheels” of this technology) are necessary to achieve levitation, as already shown in Fig. 3. On the other hand, the stability of the EML can be obtained only with a closed loop control system, which requires sensors, signal processing, A/D and D/A converters, EMI (Electromagnetic Interference) reduction, back-up energy supply and heavy and bulk electromagnetic actuators made of iron core and copper windings. Fig. 4 turns this advantage of the SML technology evident.

COMPARISON EML x SML: CIVIL ENGINEERING CONSTRUCTION

As a direct consequence of the simplicity of the SML method and its lower weight, the civil engineering construction of the SML technology presents advantages in comparison with EML systems, as shown in Fig. 5. As proof of this, the Brazilian prototype for 20 people weighs only 2.3 tons empty. 

 

 

ROUTE FOR COMMERCIALIZATION

To confirm the arguments presented in the last paragraphs, and climb levels TRL8, TRL9 and TRL10, an experimental line of the SML technology, one to two kilometers long, with curves, declivities and switches have to be constructed. The investment necessary is in the order of magnitude of 10⁷ US$. Similar steps and levels of investment have been followed by other transportation systems. The participation of Public and Private capital, forming a Partnership, the so-called PPP, is under negotiation. Along this process, the production chain will be established and the flourishment of new companies are foreseen.

CONCLUSION

This paper presented the state of the art of the disruptive MagLev Technology based on flux-pinning property of superconductors in the proximity of permanent magnets, the SML method. The technology is promising. Efforts are in course to construct a test line with all characteristics of a commercial system.

The sentence coined by the colleagues of KIMM (Korean Institute of Machinery and Materials) on the occasion of the 2011 MagLev conference, held in Daejon, lends itself very well to conclude this article: “MagLev trains are not just ordinary trains but wings that will help mankind take another leap forward in the future”.

ACKNOWLEDGMENT

To the China-Latin American United Laboratory for Rail Transportation and to FAPERJ and CNPq for the financial support.

About the authors

Richard Stephan

Laboratory of Applied Superconductivity (LASUP/UFRJ) Federal University of Rio de Janeiro

Author for correspondence.
Email: rms@ufrj.br
ORCID iD: 0000-0003-3325-4499
Scopus Author ID: 7103249684
https://www.researchgate.net/profile/Richard_Stephan

Dr.-Ing.

Brazil, P.O.Box 68504, 21941-972, RJ

Felipe Costa

Laboratory of Applied Superconductivity (LASUP/UFRJ) Federal University of Rio de Janeiro

Email: felipe@pee.ufrj.br
ORCID iD: 0000-0002-9457-2805

PhD student

Brazil, P.O.Box 68504, 21941-972, RJ

Elkin Rodriguez

Laboratory of Applied Superconductivity (LASUP/UFRJ) Federal University of Rio de Janeiro

Email: elkin@dee.ufrj.br
ORCID iD: 0000-0001-8570-9139

D.Sc.

Brazil, P.O.Box 68504, 21941-972, RJ

Zigang Deng

State Key Laboratory of Traction Power (SWJTU)

Email: deng@swjtu.cn
ORCID iD: 0000-0001-7937-9081

Dr. Prof

China, Chengdu

References

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