Volume 5 Issue 5

Authors: Henryk G. Sabiniak; Karolina Wi?nik

Abstract: The article presents the possibilities of developing the heat transfer area of supply pipes in underfloor heating. It examines the influence of ribs shape and the distance between them on the distribution of temperatures on the surface of heating plates depending on the variable temperature of the heating factor. Numerical analyses were conducted for the predetermined steady states and based on the finite element method.

Keywords: Heat Transfer; Rib; Underfloor Heating; Temperature Gradient


Authors: H. Noji

Abstract: The purpose of this research was to obtain new methods for decreasing alternating-current (AC) losses when transport currents pass through high critical-temperature superconducting power cables. The cables used in this study were composed of (RE)Ba2Cu3Ox (REBCO) superconducting tapes. The AC losses in monolayer and double-layer REBCO cables were calculated by a two-dimensional finite-element method (2D FEM). The cable parameters were those specified for the REBCO cables manufactured by Furukawa Electric Co. Ltd. In the monolayer cable, the loss in one tape of the cable was drastically decreased by increasing the tape number N from 25 to 100 (maintaining a constant critical current IC of 1,140 A in the cables). The loss in the monolayer cable also decreased as the tape width w decreased from 4 mm to 1 mm. When calculating the loss in the double-layer cable, N in the first and second layers (N1 and N2, respectively) were the same as N1 = N2 = 16, and the layer currents were assumed equal. It was observed that the loss drastically decreased as the relative tape-position angle between the layers increased, becoming minimized at a relative angle of 0.5. This reduction was caused by the cancelation of the vertical field between the first and second layers. At this relative angle, the opposite edges of the tapes in the two layers were minimally separated, and the vertical fields were cancelled out.

Keywords: High-TC Superconductor; Superconducting Power Cable; REBCO Tape; AC Loss; Finite-Element Method


Authors: M. I. Abouheaf; M.S. Mahmoud; S. Azher Hussain

Abstract: In this paper, reinforcement learning techniques are proposed for the control of autonomous microgrids. A type of approximate dynamic programming method is used to solve the Bellman equation, namely heuristic dynamic programming. The proposed control strategy is based on actor-critic networks. The control strategy is designed using a dynamic model of islanded microgrids and makes use of an internal oscillator for frequency control. The proposed control technique is based on a value iterations algorithm which is implemented online. Using only partial knowledge of the microgrid dynamics, the simulation results showed that the proposed control technique stabilizes the system and is robust to the load disturbances.

Keywords: Distributed Generation; Microgrid; Reinforcement Learning; Approximate Dynamic Programming, Heuristic Dynamic Programming; Actor-Critic Networks