ELECTRIC WIRE & CABLE, ENERGY
The Road to Liquid Hydrogen Electric Vehicle Powered by High-Temperature Superconducting Motor – Utilizing Tank Trucks to Deliver LH2 –
Ryosuke HATA * and Shigeki ISOJIMA
The 21 st century is “the era of energy, resource and environment.” In the near future, an increasing population and ad - vanced civilization will urge us to rely on solar-originated new energy sources. More specifically, hydrogen (H 2) energy generated by solar cell power will assume an important role to power vehicles, the most convenient products of modern civilization. The H 2 energy will be delivered in liquid form by tank trucks to H 2 stations, where the liquid hydrogen (LH 2) will be supplied to every automobile. Meanwhile, high-temperature superconducting (HTS) materials and technologies have markedly developed. By utilizing such application technologies as Sumitomo Electric’s cutting-edge BSCCO, an ideal hybrid electric vehicle (HEV) will be practical. LH 2, which produces 20 K cool energy, can act as a coolant itself for an HTS motor and therefore, a cooling device will not need to be mounted any more.
Thus, LH 2 holds high potential for realization of an energy-efficient environmental-friendly compact HEV, and therefore
LH 2, besides high-pressure H 2 gas, should be included within the development policies for the HEV.
Keywords: HTS HEV, Sun-originated LH 2, LH 2 Tank Truck, LH 2 station, LH 2 HTS HEV
(2), (16) 1. Introduction at the LN 2 temperature of 77 K (-196 °C) . If this HTS wire is cooled using LH 2 with a tempera ture of 20 K (- The automobile is one of the most convenient prod - 253 °C), its Ic can be increased by approximately six times ucts of modern civilization, and the number of vehicles is (200 A x 6 > 1 KA) (7) , which makes it then possible to in - rapidly increasing as the human population continues to crease output (torque = function of “Ampere x Turn”) grow and developing countries become more economically with minimum loss while retaining the ultra-compact na - active. From the standpoint of “energy, resources, and en - ture of the motor with ideally high energy efficiency. How - vironmental conservation,” however, the ongoing wave of ever, the problem still remains of creating a system for motorization has brought with it a number of problems, cooling the HTS motor to this level of LN 2/LH 2 temper - including the exhaustion of resources stemming from ris - ature and maintaining such a temperature. ing fossil fuel consumption and the rapid deterioration of Meanwhile, in order to facilitate the spread of FC EVs the environment caused by greenhouse gases, which are and hydrogen engine vehicles, both of which utilize hydro - contained within automobile exhaust (CO 2 from automo - gen resources, it is crucial that an infrastructure (i.e., hy - bile exhaust accounts for approximately 25% of gross CO 2 drogen stations) be developed that are equivalent to gas emissions) (6)-(8) . This being the case, almost all automobile stations for gasoline-powered vehicles. Given the present manufacturers have developed for commercial use electric situation of the EU and North America, which currently vehicles (EVs) or hybrid electric vehicles (HEVs) using an hold the lead in this field, it seems that it would be most electric motor, out of consideration for the earth’s natural practical and feasible to use LH 2 tank trucks to deliver hy - resources and the environment (14), (19) . Presumably, the ul - drogen produced off-site to such stations installed through - timate results of such efforts are fuel cell electric vehicles out the country, just as with gasoline. When it comes to (FC EVs) or hydrogen engine vehicles, both of which make generating hydrogen as a sustainable energy source, it has (9), (10) use of hydrogen (H 2) as fuel . Meanwhile, dramatic been pointed out that it will not be long before it becomes progress in high-temperature superconducting (HTS) necessary to depend on hydrogen that is either generated technology in recent years (1)-(3), (16), (17) has revealed that elec - off-site as a by-product or intensively produced using a new tric motors wound with HTS wire, whose electrical resist - type of energy (primarily solar cell power) (7), (8) . Whatever ance is almost zero, are optimal for motors to power the case may be, it is likely that “LH 2 will be supplied to hy - moving bodies, as they produce high torque while also con - drogen stations.” If we consider this “LH 2 station infrastruc - serving space and energy (4), (14) . Already, a prototype liquid ture” in relation to the “use of HTS motors using LH 2,” we nitrogen (LN 2) cooled HTS motor using the first-genera - arrive at the concept of “LH 2 high-temperature supercon - tion HTS wire (DI-BSCCO) is being tested in ships (5) and ducting hybrid electric vehicles (LH 2 HTS HEVs).” These automobiles (11) . completely clean, green, compact and energy-conserving By lowering the cooling temperature, it is possible to vehicles that run on sustainable energy, namely, sun-gen - significantly increase the permissible electrical current (Ic: erated hydrogen, and (liquid) hydrogen stations will surely Critical current) of HTS wire (7) . For example, DI-BSCCO guarantee to future generations the maintenance of a so - is capable of generating 200 A of Ic per HTS wire ( ≈ 1 mm 2) cial system wherein these convenient and essential automo -
SEI TECHNICAL REVIEW · NUMBER 69 · OCTOBER 2009 · 25 biles will play a core role. copper wire (used by forcibly water-cooling the heat gen - By placing the spotlight on the development of infra - erated as a result of current loss), was developed and (4), (5), (12) structure (LH 2 stations), as well as research efforts for tested on ships for the first time , the same year higher efficiency LH 2 HTS motors, this report intends to that the Kyoto Protocol came into effect on February 16, establish “LH 2 vehicles,” along with “high-pressure ambi - 2005, as shown in Fig.2 . The HTS motor’s compact size ent temperature hydrogen gas vehicles,” as additions to and high energy efficiency can be beneficial to all of the the development schedule for future hydrogen vehicles moving bodies listed in Table 1 . At the Hokkaido Toyako in Japan, out of a strong desire for early realization of a Summit of 2008, Sumitomo Electric Industries, Ltd. ex - more ideal motorized society through integration with in - hibited and test-drove a prototype of the world’s first HTS novative HTS technology. EV, details of which will be given below. Meanwhile, the peak-out and the depletion of fossil fuel resources and global warming with the increase in CO 2 emissions have become increasingly grave issues with the move into the 2. The past and future outlook of automobile 21 st century (6)-(8) . This has prompted governments and technology auto manufacturers around the world to develop and con - duct a series of demonstration tests on FC EVs and hydro - Figure 1 explicates the author’s idea of “the past and gen engine vehicles using H 2, which is considered to be future outlook of automobile technology (The road to the ultimate clean and green energy source (9), (10), (15), (19) . the ultimate future car),” the reasons why such technol - At this point in time, however, efforts to develop such au - ogy is necessary, and the innovative technologies that sup - tomobiles and the infrastructure necessary for them (hy - port it. The burgeoning population and economic lifestyle drogen stations) are not necessarily being coordinated of the 20 th century served to sharply increase the number with each other, but are instead being carried out sepa - of gasoline-powered vehicles, with the result that fossil rately. What should be noted here is that Japanese manu - fuel consumption and greenhouse gas (CO 2) emissions facturers are all aiming to develop FC EVs using have increased rapidly. In order to address this urgent “high-pressure (300 to 750 atm) ambient temperature hy - issue, an HEV using a combination of an electric motor drogen gas,” whereas BMW of Germany, for example, is and a gasoline engine was launched in 1997, which was seeking to develop hydrogen engine vehicles using LH 2. also the year that the Kyoto Protocol was adopted (on De - Likewise, many of the hydrogen stations in Europe and cember 10, 1997), as shown in Fig. 2 (6) . Subsequently, an North America are designed to “supply hydrogen in both (14) EV that does not emit CO 2 yet offers higher energy effi - liquid and gas form ,” whereas only “hydrogen gas” will ciency has been developed, and it is due to hit the market be supplied at such stations in Japan to accommodate the this year (2009) as an qualified commercial vehicle. One needs of FC EVs. A cooling device must in principle be of the most remarkable features of EVs is that they gener - mounted within an LN 2-cooled HTS EV, which is a major ate high torque at low speeds, while regenerating energy disadvantage. However, if both automobiles and hydro - by converting the motor into a generator when brakes are gen stations use LH 2, HTS DI-BSCCO wire’s Ic can be in - applied. At the same time, HTS technology, which is dis - creased by a factor of approximately six (7) due to the fact tinguished by its “zero” electrical resistance, has shown that LH 2’s temperature is 20 K (-253 °C), thereby achiev - (1)-(3) rapid progress . An HTS motor using LN 2 cooled (77 ing greater compactness and higher efficiency in compar - K) HTS DI-BISCCO, rather than an electric motor using ison with the use of LN 2 as a coolant and eliminating the
At present (~2009) In the near future (~2020) In future (2020~)
Liquid nitrogen (LN2) Electric generation e cooled HTS motor l 2
c by H engine i
driven vehicle h ＊ e HTS HEV
Improvement in motor v HTS (H) EV engine d efficiency r + ＊ HTS motor a Compactness H2 engine o HTS motor
+ b ＊Energy conservation +
Secondary batteries vehicle n
o Secondary batteries
n e g
Hybrid electric vehicle 2 o Electric generation
H fueled FC vehicle r
(HEV) Electric vehicle d by fuel cell (FC) FC y
Gasoline h Gasoline engine Electric motor + HTS HEV d engine + + Electric motor i
u FC
vehicle Electric motor Secondary q + i + + batteries Secondary batteries L HTS motor Secondary batteries + Secondary batteries ＊Realization of non fossil fuel ＊Reduction in fossil fuel ＊No emission of CO2 ＊No emission of CO2 ＊ ＊Sustainability of natural consumption Increase in energy Use of LH2 distribution Solar cell + electrolysis of H2O ＊ resources Environmental improvement efficiency tank trucks arrangement Generation of H2 2 (Reduction in CO emissions) of H2 station infrastructure (Sustainable resource)
Fig. 1. Transition and future outlook of automobile technologies (The road to ultimate vehicle)
26 · The Road to Liquid Hydrogen Electric Vehicle Powered by High-Temperature Superconducting Motor －Utilizing Tank Trucks to Deliver LH 2－ Table 1. Merits of HTS applications y s e s s m c e s s e d s o s l y n e u s e n t e e n a t i q n c i o l c r f o n l n i e - n
t a c s o e
Examples Details b Note e i h t t w h e l p
a
c i g g o t n l g i i e i S m i a S L r a t L o H B P o M C T MRI (Medical use) High field source ○ ○ ○ ○ ○ ◎ ○ Can be used in remote country NMR Extremely high field source ○ ◎ ○ Highest range (>1GHz) Large power transfer, low loss with American big PJ, collaboration with Cable (AC, DC) small diameter ◎ ◎ ○ ◎ railway company For bullet train ○ ◎ Utilizing its lightness Transformer For power transfer ◎ ○ ○ For underground substation FCL Fault current limitation ○ ○ ○ Higher reliability for existing grid SMES Energy storage ○ ◎ For grid’s stability Maglev Replacement of metal SC ○ ◎ ◎ ◎ ◎ Increase in stability, economy e l
c Ship propulsion Reduction of drag force ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ AMSC, Japanese group i h e Automobile Weight saving using fuel cell ○ ○ ◎ ○ ◎ Air force V Automobile Big torque, low loss ◎ ◎ ◎ ◎ ◎ Liquid hydrogen is suitable DC field for suppression, AC field Solidification control Silicon crystal, steel continuous cast for mixing ○ ◎ ○ Robot Weight saving and preciseness ○ ○ ◎ ○ Effective at the top of the arm Mother machines Extreme preciseness by D.D. ○ ○ ◎ ◎ Free of gear wear-out Magnetic separation Medicine, waste ○ ◎ ○ ○ Practical use in paper company Wind generator Weight saving of nacelle ○ ◎ ○ ○ ○ Lightness
biles and develop hydrogen stations as a form of social in - One-fourth of CO2 emissions Fuel efficiency of automobiles, ships, airplanes, come from transportation etc. Need to be improved frastructure. It is on these grounds that the author wishes to strongly urge Japan to not let European and North Monumental Date Protocol Future trend achievement American countries take the lead in technological devel - Agreement 1997 Toyota Shift to opment but rather, in accordance with the roadmap of Kyoto announced All (December 10) all-electric vehicle (EV) Protocol release of conveyance 2 including fuel cell car shown in Fig. 1 , aggressively seek to develop “LH FC EVs (COP3) HEV “Prius” Automobile vessel or H 2 engine HEVs,” in addition to “high-pressure H 2 gas Shift from current Sumitomo train Electric & diesel-engine ship FC EVs” as well. Ishikawajima- propulsion to Toward Enforcement 2005 Harima Heavy future electric motor “HTS motor” of Kyoto (February 16) Industries driven propulsion drive Protocol announced + success of test HTS motor drives of HTS （LiN2 cooled） propulsion 3. The past and present state of the development motor Super-eco-ship of high-temperature superconducting technology Clean Fuel efficiency improvement Green No waste/ afety Non-combustion (CO 2 reduction) by 30%-40% Non-toxic motor The 1986 discovery of the high-temperature super - 《Japanese-born advanced innovative technology of 21st century》 conducting phenomenon subsequently led to the discov - ery of various HTS materials, but the only commercial Fig. 2. Historical significance of HTS motor superconductor currently on the market is DI-BISCCO, which Sumitomo Electric developed from the first-gener - ation superconductor BSCCO, and it comprises ceramics materials discovered in 1988 in Japan (1), (2), (17) . That being need to mount a cooling device in the vehicle. In other said, Japan and the United States are currently engaged words, the low temperature of the fuel (LH 2) may also be in competition for practical application and commercial - used to cool the HTS wire, resulting in the birth of an ization of the second-generation superconductor YBCO, “ideal car” that overcomes the aforementioned disadvan - which was discovered in the U.S. in 1987. When their ef - tages. Additionally, if H 2 is obtained as energy originating forts come to fruition, the industrial supply of HTS wire, from the sun and delivered as LH 2 to hydrogen stations which is more cost-competitive and offers higher perform - via LH 2 tank trucks, the path could be opened to maintain ance than the first-generation superconductor BSCCO, the sustainability of energy resources for driving automo - will become possible. “High-temperature” superconduc -
SEI TECHNICAL REVIEW · NUMBER 69 · OCTOBER 2009 · 27 (A) applied technologies is an important goal for Japan. So far, DI-BSCCO has achieved an Ic of greater than 200 A ＜1,400A＞ 1,400 (7 times) and line lengths of 1-2 km. 1,300 In case of ingle 1,200 ＜1,140A＞ DI-BSCCO wire 0 . 2
1,100 3
(5.7 times) m m 1,000 4mm 900 4. Development of HTS motors 800 ≒ 1mm 2 of DI-BSCCO c I 700 Because of the need of high output at relatively low- 600 500 speed rotation and high availability (the long continuous ＜400A＞ 400 use of electric motors), a ship was chosen as the first sub - 4K 20K (2 times) 300 (65K) (4), (5), (12) LiHe LiH2 ＜200A＞ ject for HTS motor application , that can meet 200 (L part of the Super Eco-Ship (motor-driven contra-rotating 100 iN (1(the basic rate)) 2 ) (77K) 0 propeller propulsion system) project of the Japanese Min - 10 20 30 40 50 60 70 80 90 100（Ｋ） istry of Land, Infrastructure, Transport and Tourism Temperature (MLIT) and with economic considerations in mind, such as the large space available onboard due to the compact - Fig. 3. Relationship between temperature and critical current (Ic) ness of the HTS motor drive system. Figure 4 illustrates the structure of a prototype HTS ship propulsion electric motor and a podded propulsor, which is believed to be the ultimate form of its application (16) . While the United tivity is so called because the material becomes supercon - States Navy has announced its policy to install electric ducting at such a superconducting critical temperature motor propellers in all of its vessels and craft, a 36.5 MW- (Tc) as above 77 K, the temperature at which liquid ni - trogen is used as a coolant. With a nigh inexhaustible sup - ply existing within the atmosphere, nitrogen (N 2) is easy to extract and liquefy, and thus is inexpensive (LN 2: ap - prox. ¥50/L, mineral water: approx. ¥100/L), and pos - Structure of POD sesses superior insulating characteristics. The permissible critical current (Ic) of these HTS materials is known to increase when they are supercooled. Figure 3 shows how the coolant temperature relates to Ic. LN 2 is a superior Testing of contra-herical propulsion system Sumitomo Electric and Japanese industry-academic coolant in that it is easily obtained and cooled, but it can - group developed nitrogen cooled motor of world’s Cooling largest output 365 kW not serve as a fuel source. On the other hand, while LH 2 system Superconducting may not be easily cooled, it does offer some irreplaceable motors ■Contra-helical motor ■Specifications of the motor Liquid nitrogen advantages. Once it has been liquefied its temperature Cooling method circulation Cooling method Liquid nitrogen drops to 20 K, allowing the HTS wire’s Ic to increase to a circulation HTS wire DI-BSCCO (7) HTS wire DI-BSCCO Power 365 kW level 5.7 times greater than that of LN 2 , and LH 2 itself 12.5 kW Rotation speed 250 rpm is an excellent clean and green energy resource. Super - Power (Overload: 62.5 kW) Size (Diameter) 1.2 ‒ 0.8 -m Rotation speed 100 rpm conductivity is a phenomenon where electrical resistance Weight 4.4 ton is zero. For the purposes of industrial application, its high Size 0.6mø × 0.6m Size of the POD current, strong magnetic field, and ultra low loss (energy 0.8mø × 2m conservation) are taken advantage of. Table 1 shows the Fig. 4. HTS ship propulsion motor potential applications of superconductivity. As each of these applications is successively realized, peripheral tech - nologies will also progress and HTS wire will be mass-pro - duced, with the result that its scope of application should Table 2. Merits derived form application of HTS motor to vehicles expand (3), (16), (17) . Because of its large current and low loss, HTS technology was first applied to a power cable (HTS Characteristics of HTS motor Merits of vehicle with HTS motor AC Cable). In Albany, the state capital of New York, com - ＊Distribution in early morning mercial electric power was transmitted to some 70,000 Quiet or at midnight households in July 2006 through this cable for the first Merits over against noise ＊Home distribution vehicle; & vibration (13) Engine vehicles gathering to conven - time in the world . In Japan, too, the Tokyo Electric ient stores Power Company is progressing the project to construct a High efficiency Reduction of CO 2 emissions demonstration cable at its Asahi Substation. It is no exaggeration to say that HTS wire will be the ＊No need for transmission Large torque (Direct drive) key material that will lead innovative technologies in the Merits over for low speed ＊POD propulsion motor outside 21 st century, which has been dubbed as the “century of normal ships conduction energy, resources, and the environment,” the “era of hy - motor ＊Compact & light weight of vehi - drogen,” and the “era of direct current.” The author be - Compactness cle’s body → Low cost of fuel lieves that leading the world in the development of HTS ＊More space for cabin
28 · The Road to Liquid Hydrogen Electric Vehicle Powered by High-Temperature Superconducting Motor －Utilizing Tank Trucks to Deliver LH 2－ Superconducting electric car higher in order to gain high torque. Since the motor’s rpm is after all proportionate to the applied voltage, the motor’s voltage needs to be increased. Thus far, motor voltage has been raised to approximately 500 V for HEVs, but this still requires the connection of a large number of vehicle batteries of approximately 1- 3 V in series. In order to extend the life of recharge - able batteries, it is important to maintain an appropriate charge-discharge range. With multistage in-line, how - ever, it is difficult to uniformly manage charge and
Items Performance discharge, and so a power management system be - Cooling method Liquid nitrogen immersion comes necessary. Even with such a system, the current Superconducting wire DI-BSCCO HEV models require a voltage booster converter, or
MAX torque 120 Nm DC/DC converter, to be inserted between the motor MAX output 31 kW and the batteries connected in series as given in Fig. MAX speed 85 km/h 6, in order to obtain high applied voltage for the Cruising distance 60 km motor from the voltage generated by serially con - (at 30km/h on test site) nected batteries, which ranges between 144 V and 288 V. Because of this, such a system requires the use of the followings. (a) Serial many multistage rechargeable batteries (b) Voltage booster DC/DC converter (c) Many power semiconductors, which must be
Superconducting motor forced water-cooled (d) Forced water-cooling of the motor itself Fig. 5. World’s first “HTS motor driven vehicle (HTS EV)” If an HTS motor is used, as indicated in Fig. 6 , the number of turns (T) of the winding HTS coil can be re - duced, as HTS wire’s large current and low loss conduc - tion make it possible to increase the current (A) (as in class prototype HTS motor for their destroyers was test- A·T
SEI TECHNICAL REVIEW · NUMBER 69 · OCTOBER 2009 · 29 Large current converter with low loss
Easy Use of SiC removal of ＊Minimization of loss- converter cooled heat due to conversion generationof power by LiN 2 loss . c
Application transistor t e
2 , (inverter/converter) e of LH at Loss generation t c ＊ n n
Minimization of number 20 K e
r is minimized a y t t m e
and size of power i s
as coolant l i e b i s v b
transistors with low m e o o r u - m n
voltage and large current m
n
l r
n Range of use a O a l o c Phase A r u t o c r c e p e l i l Phase B o c e
e f M R o Phase C l .
a Currently used 3-phase AC
-270 -200p -400 150 300 m i m t e
p ˚C t
[HTS] O Multi-phase AC (for future use)
Fig. 7. Relation between on-resistance of power transistor and Fig. 8. Application of multiple phase alternating current (AC) cooled temperature - Use of SiC converter at very low temperature -
6… phase AC” is used instead of the current triphase AC, the required capacity for one power semiconductor may perature (over 100°C). With HTS EVs, a coolant of 77 be reduced, thus making it easier to achieve “uniform cur - K (LN 2) and 20 K (LH 2) may be used, and so the power rent” for HTS coils (or, this may also be thought of as a semiconductors may be cooled powerfully using a method to increase the power of the HTS motor). coolant at very low temperatures. As Fig. 7 clearly ex - (3) In order to make the normal conducting motor cur - plains, the “ON resistance,” which de termines the loss rently in use for EVs smaller and more com pact, the of the power semiconductors, may be reduced signif - motor’s rpm must be increased so that the necessary icantly when used at very low temperature compared torque may be obtained. Because of this, a transmission to the current use at high temperature environment. is required to generate the slow speed and high torque Since no electron can move at absolute zero (equiva - necessary to drive a vehicle. However, a transmission lent to infinite ON resistance), the optimal point of can be rather bulky and complicated, and it generates minus cooling temperature must exist (minimum ON an amount of loss when changing gears that is too great resistance) (7) . Preliminary research done by Sumit - to be ignored (8% to 10%). Thanks to its large [A·T], omo Electric has provided data suggesting that the an HTS motor can efficiently generate high torque at minimum point is somewhere between -40 °C and - low speeds. Using an HTS motor can therefore elimi - 50 °C. Contrary to this, the data in reference (18) sug - nate the necessity of a transmission as described in Fig. gests that the minimum point lies somewhere be - 6, which is certainly a great advantage. This advantage tween 40 K and 80 K (-233 °C and -193 °C), and that was demonstrated by the prototype HTS EV exhibited with LN 2 (77 K) ON resistance can be reduced to ap - at the Hokkaido Toyako Summit (See Fig. 5 ). proximately one-seventh of that at ambient tempera - (4) An FC EV using H 2 as fuel can only generate approx - ture. As just described, if the coolant cooling method imately 0.8 V per cell at most. In order to obtain the for the HTS motor is applied to power semiconduc - applied voltage necessary for a normal conducting tors, the following advantages may be achieved. motor, several hundred cells must be serially con - (a) Significantly reduced loss generation nected. For instance, the “GM Hydrogen 4” uses an (b) Significantly increased throughput per power FC stack consisting of 440 series-connected cells (ap - semiconductor, as the heat generated by large proximately 350 V, assuming 0.8 V/cell). For FC EVs, current can also be cooled largely (compact and such multi-series (DC) cells require an advanced level simple) of technology and strict management in terms of op - (15) (c) As LN 2 (as well as N 2 gas) works as good electric eration, reliability, service life, and maintenance . insulation, power semiconductors can be directly With an HTS motor that can run on LH 2 (20 K), the cooled with LN 2 or low temperature N 2 gas. applied voltage required to drive the motor may be In addition, since the voltage applied to power semi - lowered. Be it rechargeable batteries or FCs, the par - conductors is also lowered as stated in (1) above, fabrica - allel connection of a small number series is far simpler tion of the semiconductors themselves may becomes to operate than a multi-series connection. In addition easier. Presumably, a completely new semiconductor de - to this, the technical requirements for increasing ca - sign may be developed exclusively for such coolant cooled pacity (increasing the electrode area) to accommo - large-capacity power semiconductors for HTS motors. In date a parallel connection would instead be made order to prevent the amount of current required by a sin - easier, which then gives rise to the possibility of man - gle power semiconductor to generate the necessary power ufacturing economically efficient units for recharge - level from becoming excessively large, one of the methods able batteries and FCs exclusively for EVs. This serves that may be adopted is to apply a multiphase electric as a great source of the EVs’ appeal. power to an AC motor as illustrated in Fig. 8 . If the “4, 5, (5) The coils of normal conducting motors are formed by
30 · The Road to Liquid Hydrogen Electric Vehicle Powered by High-Temperature Superconducting Motor －Utilizing Tank Trucks to Deliver LH 2－ winding copper wire around magnetic materials. search has shown that the driving energy efficiency of These magnetic materials exhibit a phenomenon an HTS bus with a cooling device is approximately known as magnetic saturation, i.e., a limit beyond 25% higher and 13% higher than that of an HEV bus which more torque cannot be gained regardless of the and an EV bus using a normal conducting motor, re - amount of additional current applied. Likewise, spectively. However, the benefits of HTS EVs remain achieving low speed and high torque via a motor’s a subject for future investigation.) high rpm and a transmission has practically its own limits. In the case of an HTS motor, on the other hand, because even an air-core coil can achieve large magnetic flux through large A in “A·T”, there is no 6. LH 2-cooled HTS motors theoretical limit to “obtaining high torque.” Should (The ultimate vehicles of the future) there be any limit under practical use conditions, it is still possible to realize a high torque motor for a vehi - In Chapters 1 and 2, the author explained the com - cle, as its torque would be far greater than that gen - mon view that, out of consideration for energy, resources, erated by a normal conducting motor. and the environment, vehicles using hydrogen as an en - (6) In (1) - (5) above, the possibilities of HTS motors as ergy source will become the automobile of the future. being superior to normal conducting motors were dis - In the item (6) of Chapter 5, on the other hand, the cussed. The single most significant issue with EVs author pointed out that the necessity of an onboard cool - using an HTS motor is the question of how to gener - ing device would become a major issue for HTS EVs. The ate and maintain an atmospheric temperature low best solution to this issue is to develop “HTS EVs using enough to bring about the HTS state even in an EV. LH 2 which serves both as coolant and fuel.” If LH 2’s cold An HTS motor uses coolant in a thermally insulated energy stored in an LH 2 tank resistant to long-term stor - closed system, but its temperature rises gradually due age could be used to cool the HTS motor, an onboard to the heat generated by the motor itself (this is truer cooling device would be unnecessary and the advantages for AC motors) and heat that leaks in from outside. of the HTS motor (low temperature of 20 K; Ic approxi - Therefore it must be re-cooled no matter what, albeit mately six times higher) could be obtained. Figure 9 intermittently. Table 3 compares EVs both with and shows two possible systems for LH 2 EVs. Japanese manu - without a cooling device. As the table shows, the EV facturers have yet to create a prototype LH 2 FC model of without a cooling device (into which liquid coolants (A), but some overseas manufacturers, including GM, (19)
cell d at 20K motor i of the technology to passenger cars to follow. (Re - u Six times larger q i
L Ic than Ic at 77K Battery Regenerative (Refrigerant) Table 3. Low temperature generation and its maintenance With refrigerator Without refrigerator (B)《Liquid hydrogen + Engine + HTS motor 》 Installation of refrigerator in Change of coolant-tank (or car - Electric vehicle & its constant (but tridge) power HTS generator 2 H intermittent) operation (or refill of coolant like gasoline) HTS at 20K d motor H2 Gas Engine i u Six times larger q
＊Bus i
L Ic than Ic at 77K Applicable for all kinds of ＊Home distribution vehicle vehicles ＊Construction vehicles, forklift Regenerative Battery (Refrigerant) ＊Convoy truck Immediate application: For vehicles with high rate of operation, frequent gear-changes and necessity of high starting torque Fig. 9. HTS EV cooled by liquid hydrogen
SEI TECHNICAL REVIEW · NUMBER 69 · OCTOBER 2009 · 31 ) ] y a
2 d
Liquid H r
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n Several B.C. A.D. A.D. A.D. A.D. i W
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Fig. 10. Outline of BMW hydrogen 7 v i of fire on fire & animals energy u q One mil yrs 10,000 yrs 500 yrs 200 yrs 40 yrs E ( Source: World Population Prospects 1990. Energy Statics Yearbook
Fig. 11. History & forecast of energy consumption by mankind making it possible to store both LH 2 and high-pressure hydrogen gas in the tank. As shown in Fig. 10 , when both LH 2 and gasoline tanks are used, the current prototype vehicle can run for over 400 miles (640 km). If only the LH 2 tank is used, however, it can run for 125 miles (200 ) n o km). At the same time, BMW suggests that using a 10-kg i s Solar energy u f n 2 2 r Electrolysis of H O LH storage tank, which the company is currently test- u Electric a S e l power ( H2O → O 2 + H2 ) manufacturing, will allow over 350 miles (560 km) of dis - c u Solar cell N tance to be covered. (The “weight” of the fuel has a ( 2 ＜ ＞ bearing on this, but since H is the lightest molecule, the Permanency H2 (In the air) O2 H2 H2O 2 Storage “fuel energy weight density” for LH is 2.7 times that of Balance of Energy gasoline. Meanwhile, regarding the “energy bulk density,” ＜Sustainability＞ which is important because LH 2 is gasified before being
) Power generation Using k combusted in the engine, the value of H 2 gas is one-fourth r o Electric H2 and O2 d w n
i power e
that of gasoline. When using hydrogen for vehicles, both k m n Consumption of
a Fuel cell a r f
of these efficiency indicators are taken into considera - m electric energy l
u and / or a i H 2 c Electro tion.) It is believed that the existence of BMW’s “LH on o Hydrogen combustion turbine S
( power board and hydrogen engine vehicle” will be an important storage ( O2 + H2 → H 2O ) step toward realizing the concept of “LH 2 on board and hydrogen engine HTS series HEVs,” shown in Fig. 9 (B). Fig. 12. Acquisition of solar energy through “water cycle” - Permanent balance of energy -
7. Generation / transportation of LH 2 and “hydrogen stations” rents at low voltages.) If this proposal should become a re - ality, it will become possible to supply sun-originated, sus - Figure 11 illustrates how fossil energy resources, which tainable, clean, and green hydrogen and electric power to are currently used as fuels for automobiles, will reach a automobiles via “hydrogen stations” in areas of consump - peak and begin to decline, which was noted in Chapters 1 tion in which HTS EVs are in use. Figure 14 shows the pres - and 2 above. This figure clearly illustrates that, from a long- ent state of hydrogen stations (10), (19) . From the viewpoint term perspective, humankind will be forced to opt for the of sustainability of energy resources, the technique of ob - (7), (8) efficient use of new sun-originated energies . taining H 2 by modifying fossil fuels on-site (at a hydrogen Figure 12 shows how H 2 is generated (mainly by solar station) will not constitute a fundamental solution. Instead, cells) and stored, and then recycled to create electric a more practical and thus sustainable system would be one power. This is one of the most promising systems, because whereby H 2 generated off-site (specifically, the aforemen - of the need to “store and use” a practical amount of sun- tioned sun-originated H 2) is transported to various hydro - originated energy resources (8) . As a means for transporting gen stations where it is then supplied to vehicles. Europe these two energy resources (LH 2 and electric power) from and the United States each have some sixty hydrogen sta - desert areas, in which solar power generation and storage tions either available or under construction (or planned). facilities are expected to be mainly deployed, to areas of Many such stations supply both LH 2 and high-pressure H 2 consumption, the construction of “LH 2 transportation gas. There are approximately ten LH 2 generating plants pipes” has been proposed, inside of which HTS DC cables in the United States, and one or two in each EU member (20) will be installed (See Fig. 13 ). (Since the internal tem - country. Table 4 provides a comparison between LH 2 and perature of these “LH 2 transporting pipes” will be 20 K, high-pressure hydrogen gas. Judging from prior cases in HTS DC cables will be capable of transmitting large cur - Europe and the United States, when considering how hy -
32 · The Road to Liquid Hydrogen Electric Vehicle Powered by High-Temperature Superconducting Motor －Utilizing Tank Trucks to Deliver LH 2－ Table 4. Comparison between high-pressure H 2 gas and liquid H 2 e uter pip vacuum O under High-pressure sulation Items Liquid H 2 rmal in es) H2 gas The two pip etween rogen ipe (b uid hyd Inner p rized liq Refrigerator Necessary Unnecessary Pressu pipe) er t hin inn oltage it v n (w ith low bles w e High-pressure pump Unnecessary Necessary DC ca nt re m HTS rge cur nd la p a i High-pressure gas
u Unnecessary Necessary
q storage tank E Coolant storage tank Necessary Unnecessary Storage density ○ (Large) △ (Small)
Delivery of H 2 fuel to
) 2 ◎ × e H stations c
Fig. 13. Hybrid system of electricity transmission HTS DC cables in LH 2 n e Easiness and safety of i
delivering pipe n 2 2 ○ △
e H storage at H station v n o Easiness of taking on ? ? C
( board
s e i
t H2 carrying capacity & i l
i ○ △
c distance covered
Hydrogen station a F r Transformation of fossil fuel r △(?) e r o o t
t Risk rate in case of i e s a (Coal gas/Petroleum/LP gas) s s s l s High pressure gas a - ○ n e u r g e n accident FC HEV m p y 2 p t u O cylinder on board i s m H i c
c or i o c D r Electrolysis of H 2O
t High pressure gas C A H2 engine c
e (in KOH solution) l (At present) vehicle E ◎ (Include. EV) n o
＜H2 generation, storage and supply at H 2 station ＞ i Around sixfold t Merits of application c critical current × n of HTS technique
u (Ic) compared e F s Oil Refinery i 2 with “In LN 2” w Compression H stations - t 2 n c COG in Iron Mil (20MPa) in Japan H u
o f i
d (as of 2008) t o Trailer truck with o a r Electrolysis of Salt High FC (H)EV of t p
e Transfor-
s pipes on bard s t y
pressure i a
B mation 8 n g s ・・・・・
Japan’s automo - - gas e 2 f of fossil fuel n f 2 g
H BMW’s H o
i (At present) o O t Nuclear power Pyrolysis of Off-site Non HTS bile manufactur - r n a
r e 2 d d e 2 and 4 engine vehicle i H O g 2 H y
LH s n New energies
u o
e ers, Toyota or t r f H electrolysis q g i l o
Solar cell / d
tank truck L y e Electrolysis 2 u r Solar heat / h Liquid H Honda
u Total 12 2 s P Wind power of H 0 (in future) e
R (For reference) Sumitomo Elec - HTS Fig. 14. Supply of H 2 to H 2 HEV through H 2 stations tric’s trial vehicle － of LN 2 HTS EV drogen should be transported to the many hydrogen sta - tions that would be constructed in the future, transporta - 2
(Wind-power farm) e b
and practical, as with the case of gasoline transportation i (DC) n s （Remote hydraulic power ） e s g
o e p t 2 s via tank trucks. If we assume that “H ’s transportation (in - o HTS DC cable (Atomic power) i m
collection, e frastructure) will be conducted by LH 2 tank trucks,” the transmission, R distribution storage of hydrogen at each station in liquid form would Fuel cell (FC) (DC) (DC) or be simpler in terms of capacity. If this is the case, as shown Electricity H2 turbine generation
SEI TECHNICAL REVIEW · NUMBER 69 · OCTOBER 2009 · 33 In relation to energy, 2000 2050 Year resources & environment
LH 2 engine vehicle 2
H 2
(Hybrid of gasoline & LH ) y l l [Hydrogen vehicle of BMW, Germany] a i t r Internal ＊Exhaustion of fossil a Compressed national gas × P combustion (GNG such as propane) engine vehicle
fuel (Oil / Natural gas) l
e engine u f
l Gasoline engine vehicle i s ＊ s Emissions of global o warming gases (CO 2) F Diesel engine vehicle (Around 1/4~1/3) △ )
y HEV with gasoline engine generation c n e i Hybrid of c i f
f electric motor HEV with diesel engine generation e and engine h g i H g (
HEV wit CNG engine generation n i r k e a w e Normal o r p b
conduction Electric motor c e ＊ i motor vehicle l Use of electric ○ r i t & Plug-in electric motor vehicle (PHEV) c power with high h 2 e (LN Cooling) l battery w
efficiency E r HTS motor vehicle Use of atomic e w e r o
power at night d u r p s
a s n High- o e o b r i Normal t p
pressure n - a o r
HEV with FC & battery conduction
2 m e H gas on t s a n a motor vehicle
e board g 0 ○ g Fuel cell (FC) 2 5 e 7 H
Expansion r or 〜 f of use of new 2 o hybrid of H
energies e
engine, battery FC power generation s
◎ K U
Solar, wind 0 & 2 2 HEV with LH HTS motor ＜FC or “hydrogen engine”＞
& hydraulic f
l electric motor o & battery
2 powers e LH 2 on (LH cooling) y u t i f
HTS motor g board s n s n H2-engine& HTS power i e l Inexhaustible energy e vehicle g c o generator o e resources and o r 9～10 billions of people N C no emission of d HEV with H2 engine, y
greenhouse gasses H LH 2 HTS motor & battery 6.7 billions of people ［Increase in population］ s n ①
o 2008 2050 Year “Use of electric motor” + “Battery (storage of regeneration power) e i t g i
n ～ d y [Peak(2010 2050), then decline] a r ② From oil & jas to electric power: Further toward H2 FC or H2 engine power n h o a
c ＊ c Oil: 41 years
t l m ③
2 p New energies derived electric power & H a Depletion of petroleum resources i m u Gas: 63 years ＊ c r u o b
④ s
S 2 2
Construction of “LH infrastructure” & realization of LH -fueled A (＊Source: Resource & Energy, “Atomic Power 2008”) f o “HTS FC HEV” or “HTS H2 engine HEV” Aggravation of environmental issues ⇒Severer obligation of countermeasures against environmental issues
Fig. 16. The road to liquid hydrogen electric vehicle powered by high-temperature superconducting motor (LH 2 HTS FC HEV or LH 2 H2-engine HTS series HEV)
can be used. Furthermore, it would also be unnecessary 8. Conclusion to mount cooling devices in cars, which is the single largest issue for HTS EVs. Either FCs or hydrogen engine Figure 16 sums up the essence of this paper, and out - generators may be used to generate electric power in a lines a roadmap leading from our present automobiles to car using H 2. While FCs require innovative break - the ideal automobile of the future, i.e., “LH 2 HTS HEVs throughs, such as elimination of the necessity of platinum (power for which is generated by FCs or a hydrogen en - catalysts, we can safely say that hydrogen engines are part gine).” As they are among the most convenient products of an already commoditized technology. Using a hydro - of modern civilization, both the number and usage of au - gen engine to generate driving force, hydrogen vehicles tomobiles will only increase as the global population ex - do not use a generator (namely, a motor), and thus can - pands and civilization develops in the coming centuries. not use regenerative energy created while the brakes are It is quite natural that, from the standpoint of energy re - applied. Thus, they are not preferable as far as energy ef - sources and environmental conservation, sustainable, ficiency is concerned. The author would therefore like to clean, and green sun-originated hydrogen resources will point out that LH 2 is the best alternative from the point become the mainstream fuels for automobiles. When we of view of H 2 transportation infrastructures and that “LH 2 consider the development of an infrastructure involving HTS HEVs” would be the ideal technology for automo - the entire process from hydrogen generation to hydrogen biles running on LH 2 supplied at H 2 stations. Accordingly, stations, it is clear that LH 2 is obviously a more practical the author believes that Japan should consider, research, realistic choice than high-pressure H 2 gas. When we com - develop, and commercialize “LH 2 HTS HEVs (including pare conventional automobiles that use only internal those using power generated by H 2 engines as well as combustion engines and EVs (or HEVs) that may also use FCs),” in addition to “high-pressure H 2 gas FC HEVs.” regenerative energy, the EVs’ advantages in terms of en - (Here, H means the Hybrid in which FCs and recharge - ergy efficiency should remain the same in the future. If able batteries are coused.) we combine these two ongoing trends with HTS technol -
34 · The Road to Liquid Hydrogen Electric Vehicle Powered by High-Temperature Superconducting Motor －Utilizing Tank Trucks to Deliver LH 2－ ogy, which has made remarkable progress in recent years, (20) P. M. Grant, “The Super Cable: Dual Delivery of Chemical and Elec - an integrated system comprising an “HTS motor, battery, tric Power,” IEEE Trans. Appl. Super.15 (2005) 1810 and converter,” which does not require any onboard cool - ing device and thus is ideal for EVs, may be realized in the (In addition to the above, data from relevant organizations and auto man - ufacturers’ websites were also referred to.) concrete form of “LH 2 HTS HEVs.” The author wishes to point out that if we are to realize these “vehicles of the fu - ture” featuring innovative technologies (developed in Japan), it is of the utmost importance to alter Japan’s cur - rent basic development policies that now only consider “high pressure H 2 gas,” so as to also include “LH 2” within Contributors (The lead author is indicated by an asterisk ( )). the scope of development. * * * “DI-BSCCO” is a trademark or registered trademark of Sumitomo Electric R. HATA Industries, Ltd. • Dr. Eng., Former Managing Executive Officer Currently he is mainly engaged in R&D References on the matters relating to Energy, Re - (1) Kato, et al., “Development of Drastically Innovation BSCCO (DI- sources and Environment. BSCCO) Wire,” SEI TECHNICL REVIEW Vol. 62, June 2006 (2) Ayai, Hata, et al., “Achievement of High-Temperature Supercon - S. ISOJIMA ducting Wire with Critical Current Exceeding 200 A,” SEI TECH - • Chief Engineer, Materials and Process Technology NICAL REVIEW Vol. 63, December 2006 R&D Unit (3) High-temperature Superconducting Wire Made a Reality after 20 General Manager, Electric Power & Energy Years – Imminent Practical Application of Bismuth Wire, Nikkei Research Laboratories Electronics, February 28, 2005 (In Japanese) (4) Okazaki, “Study on Application of HTS Drive System for Movable Bodies,” SEI TECHNICSL REVIEW Vol. 62, June 2006 (5) Okazaki, et al., “Industrial Application of HTSC Coils Using NEX- Generation BSCCO Wire,” SEI TECHNICAL REVIEW Vol. 61, Jan - uary 2006 (6) Hata, “The Kyoto Protocol and the Northeast Asia Energy, Re - source, Environmental and Economic Cooperation Region: A Study on the DC Power Transmission System for International Intercon - nection,” SEI TECHNICAL REVIEW Vol. 61, January 2006 (7) Hata, ‘“GENESIS Project” and High-Temperature Superconducting (HTS) DC Cable –Keen Use of Ultimately Sustainable New Ener - gies-,’ SEI TECHNICAL REVEW Vol. 66, April 2008 (8) Hata, “GENESIS Project and Use of Sustainable Energy,” OHM Vol.96 No.1, January 2009 (In Japaness) and SEI TECHNICAL REVEW Vol. 69, 2009 (In English) (Planned) (9) Yamane, “BMW’s Hydrogen Vehicle Project,” Zero Emissions Sym - posium 2007, November 28, 2007 (10) Yamaji, “Hydrogen Energy Society,” Japan Society of Energy and Resources, May 26, 2008 (11) Oyama, et al., “Application of Superconductors for Automobiles,” SEI TECHNICAL REVIEW Vol. 67, October 2009 (12) Sugimoto, et al., “Prototype Study of High-temperature Supercon - ducting Electric Motors,” National Convention of the Institute of Electrical Engineers of Japan, March 17, 2005 (13) Yumura, Hata, et al., ‘World’s First In-grid Demonstration of Long- length “3-in-One” HTS Cable (Albany Project),’ SEI TECHNICAL REVIEW Vol. 64, April 2007 (14) All about Hybrid and Electric Vehicles 2007, Nikkei Business Pub - lications, Inc. (15) Potential of Fuel Cell and Electric Vehicles, Grand Prix Shuppan (16) Superconductivity! Welcome to the World of Zero Electrical Resistance!! SEI High-temperature Superconductivity Handbook, March 2009 (17) Kitazawa, “Future of Superconductivity -Network of Superconduc - tivity-,” Journal of the Cryogenic Association of Japan, 2007 (In Japanese) (18) Nemoto, Watanabe, Kikukawa, Parallel Connection MOSFET: Using High-temperature Superconducting Wire to Reduce ON Re - sistance, 79th Cryogenics & Superconductivity Committee, autumn 2008, Accelerators / Peripheral Technologies (2) 3B-a05 (2008) (19) “Frontline of Fuel Cell Vehicle Development,” OHM, January 2009
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