A superconducting material loses its electrical resistance when cooled to a certain temperature called the critical temperature. One hundred years has passed since such a superconducting phenomenon was first discovered. Sometime this year, the superconducting cables we have developed on consignment from NEDO* will be connected to the AC power grid of Tokyo Electric Power Company for demonstration test purposes. When substantially zero electrical resistance superconducting wires are used to transmit power, they will significantly reduce transmission loss and provide a power transmission capacity about 200 times that of traditional copper cables of the same cross sectional area. As an engineer who has been engaged in superconductivity research for 23 years, I am filled with deep emotion to see the demonstration test.
New Energy and Industrial Technology Development Organization, an incorporated administrative agency of Japan
In 1986, a high-temperature superconductor with a critical temperature far higher than that of previously known superconductors was discovered. At the time, I was engaged in electric wire development. When Sumitomo Electric launched a superconductivity research program, I was appointed as one of five research engineers and was inspired with the mission to create the "ultimate electric wire."
High-temperature superconductors are categorized into ceramics. At first, I could not imagine what they could be used for or the possibility of making wires from ceramics. Our research started with establishing the concept of a wire rod. Then we made palm-sized coils, cables, motors, and other devices on an experimental basis, using short superconducting wires. Through these activities, we could gradually achieve fruitful results. However, we spent about eight years until we succeeded in developing a 1000 m-long cable that could carry an electric current.
After that success, however, we drifted into a long period of research stagnation. Since a high-temperature superconductor was the same ceramics as porcelain, it was very fragile and difficult to make. We could not get the superconductors to exhibit the performance we expected. The reason for this was that when the raw material was solidified by baking, cavities were produced inside the material. These cavities lowered the density and deteriorated the superconducting performance. Even after repeated trial and error, we could not move our research forward. The Company was faced with the problem of whether to continue or discontinue the research program.
Though we were firmly convinced of our future success in principle, we could not yet draw out the intrinsic performance and properties of the raw materials. In other words, we could not establish a technique to materialize the theory. Even when many companies withdrew from the field of superconductors, we did not lose our will to continue researching. Though we were confronted with many difficult problems, we experienced the joy of verifying our ideas with actual experimental data. Without a positive attitude, we might not have been able to continue our research. As a materials engineer, I was particularly interested in superconducting materials. Due to their complex structure, the quality of these materials varied widely. We could obtain a high-quality superconductor only when we were able to severely control the manufacturing process conditions. The quality of the material depended largely on the skills of the engineers.
We were eventually able to break through a technical barrier in 2004. The new manufacturing technology we had devoted ourselves to developing since the 1990s was introduced into our new manufacturing facilities. Because of the facilities, we could now make ceramics of uniform density. Finally, we had a strong conviction that we would be sure to commercialize the "ultimate electric wire."
Superconducting cables will form a big market. At Sumitomo Electric, young researchers are focusing on further functional improvement and cost reduction of superconductors, as well as the development of superconductor application systems. The number of research and development personnel in charge of superconductivity has increased from the initial 5 to about 100.
To me, the last 23 years seems to have passed very quickly. Superconducting technology has grown intermittently during those years. In the social situation of global-scale energy problems, superconducting technology has reached the stage of practical application to magnets and cable demonstration tests. The magnets, cables, and other superconducting products are expected to help solve many energy problems. Needless to say, technology advances in response to social needs. By contrast, technology will not advance if it does not respond to social needs, even if it is superior. Technology may have the timing of advancement.
Last autumn, I received the IEC Thomas A. Edison Award for my long years of international standardization activities in the field of superconducting technology and valuable achievements in technology development. At the commendation ceremony held in Melbourne, Australia, I delivered a less-than-one-minute speech, saying "This award is an honor not only for me but also for Japan and all specialists in the field of superconductivity. One hundred years has passed since the superconducting phenomenon was discovered. I am enjoying double pleasure by receiving this award in this memorable year."
How will superconducting technology change our society? This technology will certainly change society not in a single step but slowly, over time. Upgrading superconducting wires and devices to systems will expand their use in the following five major technological fields: energy and environmental technologies, transport, ubiquitous, plant and manufacturing, and healthcare and analysis. In the field of healthcare technology, superconducting technology has already been applied for MRI and other commercial medical equipment. The superior characteristics of superconducting materials will be widely used in various fields, having large influences on our everyday lives.
In the fields of energy and environmental technologies, superconducting cables minimize power transmission loss and carry electric power at a rate 200 times that of traditional copper cables. This will contribute to the creation of a low-energy and -resource consumption society. For example, two tons of copper cables can be replaced with just 10 kg of superconducting cables to transmit the same quantity of electricity.
Since superconductors are more suitable for carrying DC power than AC power, they are suitable for carrying electric power generated from sunlight, wind, and other natural energy sources. Therefore, superconductors are expected to help solve many energy problems. The Japanese government has formulated a plan to increase the use of natural energy in order to cover a maximum of one-third of the peak domestic power demand in 2030. Locating large-scale photovoltaic power plants far distant from our living areas is essential for implementing this plan. The problem is how to transmit power from such distant locations to areas where most people live. The best solution is to use superconducting cables, which can carry power at high efficiency for long distances. To solve the energy problem, both power generation and power transmission systems must be completed at the same time. Since superconducting cables have an advantage in carrying DC power for long distances, they are useful for carrying low-voltage DC power generated by photovoltaic cells. At present, wind-generated DC power is converted to commercial-frequency AC power before being sent to a power grid. Because they can carry DC power directly, superconducting cables enhance power transmission efficiency.
The "Sahara Solar Breeder Project" is currently in progress under the leadership of Japanese scientists. This project aims to generate electric power from solar energy in the Sahara Desert, which is rich in silicon, a raw material of solar cells. The electric power generated there is used to refine the silicon and then the refined silicon is used to produce solar cells. In this way, the project has a grand design to foster industries and thereby provide numerous job opportunities in Africa, as well as to send the generated power to European countries through superconducting cables. I personally propose constructing appropriately-scaled superconductive power transmission systems in Japan, starting with areas where large amount of power is consumed.
In the field of transport technology, superconducting wires can be used for electric vehicles, linear motor cars, and railroad vehicles one-half of which operate on DC. Furthermore, superconducting cables are thinner and weigh only one-fourth as much compared to traditional copper cables. These advantages make it possible to lay them along highways and other pathways, thereby opening up the possibility for new road services. Though I cannot predict when the above ideas will be put into practice, it is undeniable that superconducting technology will support our everyday lives in the future.