Obtaining electricity by direct transfer of charge generated in corona discharge

Abstract

The depletion of traditional energy sources such as deposits of hydrocarbons and uranium, as well as eco logical problems related to the traditional methods of energy production, make searching for alternative methods of electricity generation an important task. In past decades, much effort has been spent in developing such methods, with some forms thereof-e.g., solar and wind power engineering-already being employed on a commercial basis [1]. However, even these methods cannot be considered to be environ mentally clean, since the energy consumed in manu facturing one wind power generator or solar cell is comparable with (or exceed) the total yield of electric energy for the entire working life of these devices [2]. Therefore, the search for new methods of electricity production with minimum capital expenditures is still topical.In this work, we consider the possibility of generat ing electricity by means of direct transfer of charge carriers in a gas or vapor flow. It is proposed to use corona discharge as the source of charge carriers of one sign, in which the spatial separation of carriers takes place naturally [3]. Indeed, in the region of corona discharge that is adjacent to a counter elec trode, positive or negative ions (depending on the corona type) move freely in a self consistent electric field comprising a sum of the fields of electrodes and carriers (space charge) involved in the formation of corona [4]. These charge carriers can be used to pro vide the electromotive force (emf).Consider a system in which a flow of air, other gas, or vapor moves perpendicular to the axis of discharge. In this case, ions occur under the action of two forces-from this flow and from the electric field-so that, e.g., in air at atmospheric pressure, the motion of ions can be described by the following equation:where V i is the ion velocity, V g is the velocity of gas flow, E is the electric field strength, and K is the ion mobil ity. Note that the three terms are vectors and are added in accordance with vector summation rules. Under typical corona discharge conditions, an electric field near the counter electrode is E ~ 5 × 10 3 V/cm, the ion mobility is K ~ 2 × 10 -4 m 2 /(V s) [5], and the "electri cal" part of the ion velocity amounts to V el ~ 100 m/s. If the counter electrode is not very much extended, the airflow (wind) at a velocity of 20-30 m/s can blow off a significant part of ions generated in discharge. Let us consider an example of how these ions can be used for emf generation. Figure 1 shows a simple electrical scheme of emf generation with the aid of corona discharge. Then dis charge operates between point electrode 1 and counter electrode 2. The latter electrode must be arranged downstream of the airflow. In practice, the minimum gap width is several millimeters and is limited by the transition from corona to spark discharge with decreasing area of the counter electrode. Collector electrode 3 is a grid of mesh that must be fine enough to capture moving ions, while being sufficiently trans parent to produce ...