High Ohmic Losses Research Articles

Anode Supported Thin Zirconia Based Cells for Intermediate Temperature SOFC

Ni-YSZ anode supports show a fundamentally different microstructure from screenprinted Ni-YSZ anodes on YSZ electrolyte supports. Of high density and composed of fine zirconia and nickel oxide to allow for cofiring with a thin zirconia electrolyte film (5 µm), the anode support shows advantages of adequate strength and increased electrochemical activity probably not only limited to the TPB, unlike screen printed porous anodes. Areas up to 100 cm2 have been fabricated. Electrochemical cell testing produced results of >80% fuel utilisation, 35% electrical efficiency and >20 W at 800°C using hydrogen fuel. Unusually high ohmic loss (*3 x theoretical) on supported cells is consistently observed. The smallest loss is measured when employing thin dense cathodes of a mixed conducting material. Overall cell performance (at *800 °C) is more determined by the cathode than by the anode support.

The synthesis and thermal evaluation of a novel cerium precursor to grow thick ceria films by metal‐organic chemical vapor deposition (MOCVD)

Ce1‐xGdxO2‐x/2 as a thick electrolyte in solid oxide fuel cells should result in high current densities and acceptable ohmic losses at 500°C. It would be interesting to be able to grow such an electrolyte by MOCVD, and in this work the synthesis and thermal evaluation of a novel, air‐stable, liquid cerium precursor [{Ce(fod)3}2(tetraglyme)] for the MOCVD of the cerium component of the electrolyte is reported. Growth of good quality, thick, crystalline ceria films from the precursor has been demonstrated for the first time.

Adverse shielding of the heating field and high ohmic loss introduced by electrostatic shields employed in radio-frequency heating of plasma

The electrostatic shields now commonly employed to shield antennas in the heating of plasma in the ion cyclotron frequency range are shown to reduce the specific radiation resistance of a long narrow antenna in the presence of plasma by a significant factor (on the order of 2/3 for a typical double-array shield) due to the effect of magnetic shielding of the magnetosonic polarization. An allied change in antenna specific inductance is also found. These effects are shown to diminish with increase in antenna width and should pose no major problem for the wide antennas projected for use in fusion experiments. In addition to the foregoing effects which are not ohmically dissipative in essence, electrostatic shields are also shown to introduce surprisingly high ohmic loss, this being of potential importance in shield design. The dependences of the above magnetic and ohmic phenomena on shield parameters are given and a shield design minimizing them is presented. Their repercussion on coupling efficiency and on the excitation voltage necessary for a given power flux from the antenna is discussed.

Analysis of Radio Frequency Transmission in a Semicircular Mine Tunnel Containing Two Axial Conductors

We present an analysis of the propagation in a uniform tunnel of semicircular cross section that contains two axial conductors. In particular, we show that, even if one of these conductors has high ohmic loss, one of the two propagating modes has relatively low attenuation. This corresponds to the situation where an unloaded dedicated wire is used to improve radio frequency communication in a mine tunnel that contains a heavily loaded trolley wire.

Induction motors for multispeed service with particular reference to cascade operation

During the last ten or fifteen years a great deal of work has been done toward perfecting methods for varying the speed of induction motors. Each of these methods has certain disadvantages, which have precluded the general adoption of any one of them for practical use. The method most generally applied for varying the speed is that of inserting resistance in the secondary circuit. This method of speed regulation, however, has the one great disadvantage that, for a certain load and speed a certain amount of resistance is required; and as soon as the load changes, the resistance must be changed in order to maintain the same speed. When the load is taken off the motor will return to its synchronous speed. It is also evident that such speed regulation can be obtained only by a great sacrifice of efficiency, due to the high ohmic losses in the secondary circuit.

Induction Motors for Multispeed Service with Particular Reference to Cascade Operation

During the last ten or fifteen years a great deal of work has been done toward perfecting methods for varying the speed of induction motors. Each of these methods has certain disadvantages, which have precluded the general adoption of any one of them for practical use. The method most generally applied for varying the speed is that of inserting resistance in the secondary circuit. This method of speed regulation, however, has the one great disadvantage that, for a certain load and speed a certain amount of resistance is required; and as soon as the load changes, the resistance must be changed in order to maintain the same speed. When the load is taken off the motor will return to its synchronous speed. It is also evident that such speed regulation can be obtained only by a great sacrifice of efficiency, due to the high ohmic losses in the secondary circuit.