WHY MUNICIPALITIES FAVOUR ELECTRICS:
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How Electrically-propelled Vehicles Act as a Boon to Operating Stations.
IT GOES almost without. saying that it is to the advantage of municipalities, where • they own electricity generating stations, to employ electrkally-driven vehicles for every purpose in connectiam with the town service to which they can be applied. The electricity generating station has been very much handicapped from the start lay the fact that it has only limited means of storing current ; it has nothing similar to, or in any way approaching that for gas. The gas engineer can make his gas whenever it is convenient and economical : all that he has to he careful about is that his st.orage capacity is sufficient to carry him over week• ends, bank holidays, etc., and that the storage is used to the best advantage. He is subject to a certain amount of loss due to leakage when he stores his gas for any length of time, but, for nights, for instance, weekends, etc., the leakage does not amnnt to anything at all appreciable. in the storage that is available for electricity generating stations there is also leakage, quite as much as the gas engineer is subject to, if the charge in the storage batteries is held over for say a week-end, or a bank holiday.
The electrical engineer, running an electricity generating station, has, in practice, to generate his current as and when required, it may be taken that, when, say, someone switches on a lamp in a bedroom, in the middle of the night, the current taken by that lamp is generated in the generating station perhaps a few instants before the light is visible in the lamp. In the early days of electric lighting, the electricity generating station was very much more heavily handicapped than it is at present.; the current taken for light was principally by tradesmen for their shops and was only required for a few hours in the evening during the winter, a little longer on Saturday evenings, and hardly at all during the summer. Meanwhile, the generating station had to be running the whole 24 -hours with at least one generator, and its prime mover in case somebody wanted a light.
The advent of electric trams improved this a little, but it was soon found that something of. the same kind rules with them ; there is+ a rush time in the morning and evening in most towns, and sometimes a small rush at mid-day, whilst the current is required for the trains at the same time as for the lights—in winter at any rate. So. whilst the generating stations were obliged to be built larger, the relief brought by the trams was not great. The increase of the use of electricity for power in factories was also hoped to have helped matters ; it has certainly increased the load at certain times of the day when it was previously very light, but, again, the same trouble comes in.: most factories require power, in the winter months, during the same hours that shopkeepers require light and when there is usually a fairly heavy load on the tram service.
Hence, again, the devetopment of the electric power service has increased the size of the generating stations and, in particular, the size of the individual units, but it has not brought very much relief to the handicap as against gas. The electricity generating station still has to provide more and more generating plant as the demand increases, and is still without any appreciable relief in the matter of storage.
The Storage Battery.
The storage battery, or the accumulator, as itis so often called, is a very useful apparatus for certain purposes, and it is, and has been applied to help the central station engineer over some of his difficulties, but it is, in no sense, a method of storage in the same ;sense that the gasholder is. The
storage battery makes a charge of practically 50 per cent. of the current that is delivered, to it for the storage accommodation it gives, except in special cases, and this in addition to the leakage that corresponds to that of 'gas from the gasholder. It has been applied largely to the generating stations of small towns, to carry the station over the night load.
In these cases, its use has. been economical because the demand for current has been very small indeed during the night, and it was therefore cheaper to supply from a storage battery charged during the day than to incur the .expense of rUnning the whole plant, the steam engine, boiler, etc., during the night.
The storage battery has also been applied very successfully indeed, and with a very much higher efficiency than that given above, in some large generating stations, to help carry the station over the time of peak load, the time when tradesmen's shop lamps are alight, tramways are busy and fac tories are still running. Even there, the storage battery has been subject to a very heavy handicap. The current being delivered at the bus bars of the generating station has had to be transformed to that required by the battery, with the aid of a "_booster." The booster has taken the surplus, current from the machines running during slack hours and poured it into the storage batteries and, during peak times, the storage batteries have poured their current back again, through the booster, to the bus bars, and have helped the station to meet the very heavy load at that time. The batteries have worked at an efficiency of 80 per cent., but, even then, there have been the charges made by the booster for delivering the current to the battery from the bus bars, and for re-delivering the current to the bus bars from the battery.
The Time When Current Should be Cheap.
There is one period during the 24 hours when the chief engineer of any electricity generating station should heartily welcome any demand for current, and that is during the night, say from 11 p.m. to 5 or 6 a.m., and this is the time when it should be convenient to charge the batteries of any electrical vehicles and particularly those employed on -the town service—the refuse carts, the tramway repairing towers, the vans; for delivering parcels, or objects to diffeent parts of the town (such as gas or electric heating apparatus, stcrves, etc.), trolleys for conveying materials to different parts of the town where building or road repairing operations may be in progress, and many others. It is in this form that the storage battery will do good service economically. During this period, the station has to be more or less alive the night staff must be on duty, all of them, and all must be on the qui vive, in case of something happening to one of the mains, for instance. The boilers must be under steam and all their accessories running. At least one steam engine or turbine must be running; probably one is running, and another ready to be brought into service very quickly in case of accident. In the large modern station, the steam engines or turbines will be large and, though there is the street lighting to help keep them going, it must be remembered that street lighting is also required when everything else is, and the net result is that any additional current required during the night, over and above that required for street lighting, etc.. could be supplied very cheaply. It cannot, of course, be quite given away ; every additional unit generated requires its own additional quantum of coal, water, etc., but
the dead charges should be practically nil for any additional current supplied during the night hours.
The current supplied to the batteries by no means represents that which the generators in the generating stations have to furnish. What the generators have to furnish will be, at least, twice that taken in by the batteries, but, even at that, the cost of current during those hours should be small. In the large towns, for instance, the cost of fuel (which would be the principal cost of the charging current for the accumulator) is only about half the total cost of producing the current, including dead charges. It will be seen, therefore, what a great boon it should be to generating stations to employ electrically-driven commercial vehicles, particularly as the current and everything else employed is the property of the ratepayer, while petrol, paraffin, or any other propellent would have to be purchased.
(To' be concluded.)