There are high expectations for coated conductors in electric power applications such as SMES, power cables and transformers owing to their ability to contribute to stabilizing and increasing the capacity of the electric power supply grid, as well as reduce CO2 emissions based on their high critical-current characteristics. R&D has been performed on wires and power devices as part of many national projects all over the world. The Materials & Power Applications of Coated Conductors (M-PACC) project is a national project in Japan supported by the Ministry of Economy, Trade and Indstry (METI) and the New Energy and Industrial Technology Development Organization (NEDO) to develop both coated conductors that meet the market requirements and fundamental technologies for power applications using coated conductors. Three years have passed since this five-year national project started in fiscal 2008. In this article, R&D results are reviewed and compared with the interim/final targets of the project, and the future prospects are discussed.
A new Japanese national project has started in 2008 to develop high temperature superconducting electric power devices. In this project, we have developed a superconducting magnetic energy storage (SMES) system, which are highly expected as a stable power supply. Main issues are a large current capacity conductor made of YBCO-coated tapes and a compact coil wound the conductors. Aiming at the manufacturing of compact coil with higher energy density through the creation of higher magnetic field, we produced YBCO coil, and by carrying out hoop stress tests. Also, aiming at the development of 20 MJ class SMES component coils necessary for picturing the technological outlook of 2 GJ class SMES coil for power system control, we manufactured component coils (outer diameter 650 mm), adopting the bundled conductor that would enable the realization of high strength and low loss, proving that its current capacity was large enough to exceed 2.6 kA, through basic verification test for energization. In addition, we have challenged the development of high efficiency coil conduction cooling technology, stable manufacturing technology of coated conductors for SMES and the highly reliable/highly durable SMES coil component technology.
There are expectations for high-temperature superconducting (HTS) power cables as a compact cable with large capacity and low-loss power transmission. Recently, the stable manufacture of many long REBCO (RE = rare-earth element) tapes has been achieved. REBCO tapes have a high critical-current density, and the AC loss resulting from the parallel magnetic field is extremely small because of the thin-film structure of the superconducting layer. The basis of the M-PACC (Materials & Power Applications of Coated Conductors) project is to develop a process technology for fabricating REBCO tap