Why Will Future Automobiles be Electric? – The Advantages of Direct Connection to the Electricity Grid
By John Talbot
(Under the Direction of the Lord Jesus, Prov 3:6; Col 3:17)
In the previous article we came to the conclusion that battery-powered vehicles would only be suitable for short distance commuting. In this article we look at some of the advantages of using electric vehicles connected directly to the electricity grid. Familiar examples of vehicles connected directly to the electricity grid are electric railroad trains, some rapid transit systems, and trolley buses. Usually these make use of overhead wires for connecting to the grid, or, in the case of railroad trains, both overhead wires and the track. In a few cases, mainly in Great Britain, connection is made by using the conventional track and a third rail, or even a fourth rail. Such multiple rail systems use a low voltage (typically 750 volts) and require numerous sub-stations. The alternative is a system of overhead wires, usually referred to as “catenary.” Sometimes two wires are used (in the case of trolley buses) or the return is made through the track (in the case of railways). Much higher voltages can be used with a catenary system, the most common being 25 000 volts. In South Africa the heavy haul lines use 50 000 volts. Higher voltages enable the use of fewer, more widely spaced, substations. For example, the Sishen-Saldanha line in South Africa has only five substations in its length of 861 kilometers. Had a 25 000 volt system been used, 25 sub-stations would have been required. With 750 volts the system would not have been workable.
The system for road-going vehicles that has been under development by my company, Talbot Electric (Pty) Limited, uses conductors submerged in the road aggregate. It is a high voltage system comparable with catenary. All the untidy masts and overhead wires are eliminated. It is environmentally friendly and intrinsically safe and has adequate lightning protection. In its simplest form it is an SWER (Single Wire, Earth Return) system. The single wire is mounted on insulators inside a metal channel. The metal channel is firmly grounded and serves, together with the ground, as the earth return. It has a narrow opening in its top surface through which the current collector passes. Insulators ensure that electrical contact between the current collector and the metal channel cannot occur. The metal channel serves as a Faraday cage around the single wire. It is therefore impossible for lightning to strike the single wire. If lightning strikes, it will strike the metal channel, which is grounded along its entire length. Hence the system is immune to lightning damage.
More complex systems for three wire Hopkinson/Edison, and for three phase, systems have also been designed. Information on these will be found on my website.
In this article we have seen some of the advantages of the new Talbot Electric system of connecting vehicles, both road and rail, directly to the electricity grid, namely the elimination of unsightly and expensive overhead wiring, and immunity to lightning damage. In the next article we will look at means of controlling the speed of electric vehicles.
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