Sturtevant Monogram exhauster and solid base heater.
District Steam Heating.
At Lockport, New York, a city of about 20,000 population, more than 350 dwellings and business premises are heated by the American District Steam Company, a concern which has installed more than 250 similar plants throughout the Union. The advantages of this system are plain:—cleanliness is promoted; customers handle no coal or ashes, tend no fires or boilers; the heat is more steadily and equably supplied than if it came from individual boilers; heat is ready day or night during the heating season; the hazard from fire is lowered and the risk of boiler explosion is abolished; water may be heated for laundries, bath-rooms and kitchens. Cheap fuel may be used, and stoked by machinery. An individual boiler in a building has to be large enough for its heaviest duty; in many cases it is called upon for but one tenth to one fifth of its full power, with much incidental waste. At a central station only as many boilers of a group are employed at a time as may be worked to their full capacity, responding to the demands of the weather.
At Lockport the steam-pipes are of wrought iron covered with sheet asbestos and enclosed in a round tin-lined wood casing, having a shell 4 inches thick, with a dead air space of about one inch between the tin and the asbestos. In its largest size this pipe has shown a total loss by radiation and conduction of but one part in four hundred in one mile; for the same distance the smallest pipe has suffered a loss of six per cent. Live steam is used at Lockport, but as a rule heating plants are supplied with exhaust steam. When intensely cold weather prevails this may be supplemented by boilers in reserve which supply live steam.
It is worth while to remark the tendency to unify, on lines of the best economy, a service of both heat and electricity. In Atlanta there were recently in operation twenty-two isolated electric plants. The central station installed a steam heating system, and as a result in less than a year all but two of the isolated plants went out of business.
Isolated Plants.
The success of the central station at Atlanta is due to the moderate scale of its charges. In the past there has been some complaint of the rates levied by central stations. In the future this complaint is likely to diminish, because an isolated plant for the production of heat and electricity was never before so low in cost, so efficient in working, as to-day. Well managed central stations broaden their market by putting a premium upon the utmost possible use of electricity. In Brooklyn, for example, the Edison Electric Company charges 10 cents per horse-power hour to customers using 100 to 250 horse-power hours per month; as consumption increases so do discounts until the customer who buys 5,000 horse-power hours pays 4 cents. The demand for current in all its diverse applications is stimulated with energy and address. A house or apartment of seven rooms is wired for twelve lights, with all fixtures complete, for $95. Signs for advertising purposes are provided gratis, on condition that they be lighted by the Company. The economy of a small ice machine or a refrigerator is pointed out all summer long, while in winter the comfort and convenience of electric heat is as plainly kept before the public. Such a policy as this takes account of the irrepressible facts of present day competition. When gas was the sole illuminant, producible only on a vast scale, served by an elaborate scheme of piping that from the nature of the case fell into a single hand, there was a liability to extortion. To-day in towns and cities electricity, the chief source of light, can be ground out anywhere simply, cheaply and without offence, incidentally affording when desired almost as much heat as if the fuel had been burnt to produce nothing else. Among the gifts bestowed by the electrician not the least is this conferring at the lowest price two prime necessities of life. But however liberal the management of a central station, many a fat plum will remain outside its pudding. A huge hotel, an office-building, factory, or department store, is best served by a plant of its own designed to furnish both heat and electricity, in which case the electric current will cost much less than if bought from a central station.
On occasion an isolated plant supplies a neighborhood, and at prices lower than those of a large central station which may be at a considerable distance. At Newark in the New Jersey Freie Zeitung building a 400 kilowatt plant is installed which supplies the neighbors in two blocks with electricity at 6 to 8 cents per kilowatt hour, according to the extent of their consumption. A necessary conduit crosses Campbell Street in this service. It seems likely that small power-centres of this kind, requiring no franchise, may be common in the near future, especially if united with heating systems. An inviting field for such installations is in the new residential quarters of our cities and towns, where in many cases a whole block might be cheaply and effectively served from a single plant.