Antonis P. Papadakis

Numerical Analysis of the Heating Effects of an Atmospheric Air-Dielectric Barrier Discharge

In this paper, the formation of the avalanche, primary streamer, secondary streamer, neutral gas heating effects, striations, as well as the radial expansion of the discharge from the symmetry axis toward the boundaries in a constant voltage atmospheric pressure air-dielectric barrier discharge configuration are analyzed. A voltage of 11.2 kV is applied between two metallic parallel plates which are placed at a distance of 4 mm apart. Two rectangular blocks of dielectric medium of 1 mm thickness, each with a relative permittivity of 8, are attached to the cathode and anode metallic electrodes, leaving the remaining 2-mm air gap for the atmospheric air discharge to develop. A single electron is released at the cathode as an initial condition and the development of the barrier discharge with its associated heating effects is analyzed. It has been shown that the discharge exhibits phenomena of radial expansion toward the outer boundaries, forming patterns of striations/filaments along the discharge and temperature rising of ambient air to 490 °K amounting to 63% increase above the ambient temperature. A secondary streamer has been observed traveling from the anode toward the cathode, after the primary streamer hits the cathode, and the primary and secondary streamer speeds were found to exhibit similar propagation speeds within the range 0.5 × 105 - 5 × 105 ms-1. The secondary streamer was found to be associated with electron charge densities of the order of 0.5 × 1018 - 1.5 × 1018 m-3, net charge densities of 1 × 1018 m-3 and radial and axial electric fields of 0.5 × 106 Vm-1.

Streamer propagation in non-uniform gaps at ambient atmospheric air pressures

The streamer propagation in point-plane, non-uniform gaps under high applied electric fields, prior to the impact of primary streamer on cathode, is analyzed. The configuration used is an anode hyperboloid with 50-μm radius of curvature, and a flat plate as the cathode. The applied voltage is 130-kV direct current, and an initial electron is assumed to exist close to the anode in ambient air. The geometry used is a two-dimensional axisymmetry with a gap of 5 cm between the anode and the cathode. It is shown that the streamer is formed on the anode tip as expected, and midway toward the cathode, it separates into two streamers, the primary streamer that continues its propagation toward the cathode, and the branched streamer expanding radially toward the outer boundaries. The qualitative behavior of the discharge is analyzed in terms of streamer speeds, radial and axial electric fields, charged particle densities, and conductive currents. A branched streamer plasma structure was observed along the path of the primary plasma structure expanding radially outwards.

Experimental Characterization of a Single Axis Photovoltaic Tracking System

 Abstract Nowadays, photovoltaic is one of the most prominent renewable energy source technologies. One of the most important aspects of maximizing the photovoltaic output is for the photovoltaic panel to face the sun at a right angle at all times such that maximum irradiation is incident on the solar cells. Due to the continuous movement of the sun, an automatic solar tracking system is necessary for tracking purposes. Ideally, a dual axis tracking system is necessary to track the sun in longitudinal and vertical directions; however the elevation angle to the sun in Cyprus is constant and known beforehand at an approximate elevation angle of 27 o to the South. Alternatively, one can use a much cheaper and effective single axis tracking system to track the sun effectively. The solar panel is allowed to move longitudinally from East to West from -165 to 165 o to sync with the sun. In order to conduct experimental measurements and verify them with analytical results, the I-V400 Photovoltaic Tester was utilized. The instrument was used to measure the incident power density of light and operating temperature of the photovoltaic panel using a light sensor and thermocouple respectively, as well as the current-voltage characteristics such as open-circuit voltage, short-circuit current, maximum power point operation and efficiency. The photovoltaic panel readings were taken under varying weather conditions in an attempt to compare with analytical results and determine the various parameters of