162
7 Concluding Remarks
water in the field of electric power generation. Water must be circulated for cooling
in thermal power plants. If impure substances contained in the water adhere to the
inner walls of heat exchangers, they degrade the heat exchange performance. Thus,
it is necessary to purify the water. In geothermal power generation, this technology is
also expected to prevent impurities contained in the hot spring water from adhering
to the inner walls of pipes or rotating fans, which will cause clogging or reduction
in the efficiency, respectively.
(3) Transportation
One of applications for transportation systems is the superconducting magnetic levitated (SCMAGLEV) train. It is planned that these trains will run between Tokyo
and Nagoya, and the line will be extended to Osaka in the future. Superconducting
magnets in the train are operated in the persistent current mode, and the train is
levitated by the repulsive interaction between the magnetic field produced by the
superconducting magnets and the magnetic field that is induced in closed coils or
conducting plates arranged on the ground when the train gets close. Acceleration
or deacceleration is done by controlling the current applied to the driving coils that
produce attractive or repulsive forces. Since the levitation is realized by using repulsive forces, the train does not touch the walls due to the strong repulsive force, even
when there is a big earthquake. The operating speed of the trains will be 500 km/h.
This is limited to prevent the power efficiency from being reduced by air resistance
and to keep the noise level low when the train goes into or out of a tunnel. In principle,
however, there is no limit to the speed. It would be possible to increase the speed
even up to 3500 km/h, if the train runs in an evacuated tube.
Ships usually move by means of engine that directly rotate their screws, which are
placed at the stern. Mostly, ships do not sail at the maximum speed but with about
half that value. In this case, the efficiency of the engine is not high. It is better to drive
the screw with an electric motor to improve the efficiency. Then, an electric generator
is necessary to drive the motor. It seems to be inefficient to generate electricity and
rotate the screw using generated electric power instead of the direct drive by the
engine. The efficiency mostly increases, however, since the efficiencies of electric
generators and motors are high. An additional merit of this system is the increase in
the efficiency brought about by a smart shape for the stern, which reduces the water
resistance, since the engine can be replaced by a small, powerful electric motor. In
addition, the generator can be placed in a free space in the ship, and this may give the
ship a structure of high utility. It is possible to install a superconducting generator
and motor to further increase the efficiency. This is expected for large ships and also
contributes to a reduction in CO 2 emission.
The aerospace industry intends to reduce the amount of its CO 2 emissions around
the world in 2050 to the half of the present amount as a measure against global
warming. On the other hand, the need for air flights is estimated to be doubled.
Hence, we have to develop a new technology to reduce the CO 2 emissions to one
quarter in the present stage. Electrification is inevitable for the propulsion system,
and the superconductor technology is expected to play a role in this achievement.
7 Concluding Remarks
water in the field of electric power generation. Water must be circulated for cooling
in thermal power plants. If impure substances contained in the water adhere to the
inner walls of heat exchangers, they degrade the heat exchange performance. Thus,
it is necessary to purify the water. In geothermal power generation, this technology is
also expected to prevent impurities contained in the hot spring water from adhering
to the inner walls of pipes or rotating fans, which will cause clogging or reduction
in the efficiency, respectively.
(3) Transportation
One of applications for transportation systems is the superconducting magnetic levitated (SCMAGLEV) train. It is planned that these trains will run between Tokyo
and Nagoya, and the line will be extended to Osaka in the future. Superconducting
magnets in the train are operated in the persistent current mode, and the train is
levitated by the repulsive interaction between the magnetic field produced by the
superconducting magnets and the magnetic field that is induced in closed coils or
conducting plates arranged on the ground when the train gets close. Acceleration
or deacceleration is done by controlling the current applied to the driving coils that
produce attractive or repulsive forces. Since the levitation is realized by using repulsive forces, the train does not touch the walls due to the strong repulsive force, even
when there is a big earthquake. The operating speed of the trains will be 500 km/h.
This is limited to prevent the power efficiency from being reduced by air resistance
and to keep the noise level low when the train goes into or out of a tunnel. In principle,
however, there is no limit to the speed. It would be possible to increase the speed
even up to 3500 km/h, if the train runs in an evacuated tube.
Ships usually move by means of engine that directly rotate their screws, which are
placed at the stern. Mostly, ships do not sail at the maximum speed but with about
half that value. In this case, the efficiency of the engine is not high. It is better to drive
the screw with an electric motor to improve the efficiency. Then, an electric generator
is necessary to drive the motor. It seems to be inefficient to generate electricity and
rotate the screw using generated electric power instead of the direct drive by the
engine. The efficiency mostly increases, however, since the efficiencies of electric
generators and motors are high. An additional merit of this system is the increase in
the efficiency brought about by a smart shape for the stern, which reduces the water
resistance, since the engine can be replaced by a small, powerful electric motor. In
addition, the generator can be placed in a free space in the ship, and this may give the
ship a structure of high utility. It is possible to install a superconducting generator
and motor to further increase the efficiency. This is expected for large ships and also
contributes to a reduction in CO 2 emission.
The aerospace industry intends to reduce the amount of its CO 2 emissions around
the world in 2050 to the half of the present amount as a measure against global
warming. On the other hand, the need for air flights is estimated to be doubled.
Hence, we have to develop a new technology to reduce the CO 2 emissions to one
quarter in the present stage. Electrification is inevitable for the propulsion system,
and the superconductor technology is expected to play a role in this achievement.