Development of a Compact Measurement System of Transport Characteristics in HTS Conductors by Using an HTS Current
In order to realize HTS power machines and devices with high performance, it is important to evaluate the characteristics of HTS conductors quantitatively. We developed a compact system to measure the transport characteristics of HTS conductors under various experimental conditions. This system enables us to measure the transport characteristics of straight HTS conductors up to a current capacity of 1 kA class at 77 K, 66 K, and 4.2 K. The measurement of transport current losses is done by the Poynting vector method. The distribution of Poynting vectors around the sample conductor can be obtained by using many sets of both potential leads and pickup coils. An HTS current transformer (HTS-CT) is used to feed current to the sample conductor for the measurement. A secondary current of about 1 kA at 77 K can be induced when the primary current is 40 A. The sample conductor is connected to the secondary coil of this transformer. As a sample conductor, we used a conductor consisting of 16 parallel Ag-sheathed Bi-2223 multifilamentary tapes. The joint method between the HTS-CT and sample conductors is also examined. Based on these results, the usefulness of this measurement system is discussed.
AC losses in long Bi-2223 tapes wound into a solenoidal-coil
Electrical loss-measurements were carried out in liquid nitrogen for long Bi-2223 tapes wound into a solenoidal-coil under various external conditions of ac transport currents and ac magnetic fields. In this experiment a new measuring-system, which is an extension of our original measuring-system applicable to short and straight HTS tapes, was developed. In this new system, the Poynting vectors at the outer and the inner surfaces of the sample coil were measured to get ac loss values by using two movable sets consisting of both a potential lead pair and a pick-up coil on each surface of the coil; The moving direction is the coil axis and its distance is one pitch of coil windings. Several samples were prepared in order to clarify fundamental electromagnetic-properties of Bi-2223 coils with various windings. The obvious difference of loss properties among these samples was observed for some external conditions of ac transport currents and ac magnetic fields.
Thermodynamic Evaluation of Solar Integration into a Natural Gas Combined Cycle Power Plant
The term integrated solar combined-cycle (ISCC) has been used to define the combination of solar thermal energy into a natural gas combined-cycle (NGCC) power plant. Based on a detailed thermodynamic cycle model for a reference ISCC plant, the impact of solar addition is thoroughly evaluated for a wide range of input parameters such as solar thermal input and ambient temperature. It is shown that solar hybridization into an NGCC plant may give rise to a substantial benefit from a thermodynamic point of view. The work here also indicates that a significant solar contribution may be achieved in an ISCC plant, thus implying substantial fuel savings and environmental benefits.