The relative fuel economy of electricity, gas, oil, and solid fuel, as heating agents

The paperis an effort toexplain the reason why, and the conditions in which, electrical power can be used competitively for the heating of buildings, in spite of the fact that the cost of the crude heat is several times greater than that of any other heating medium. It deals exclusively with the cost of the fuel and the labour inevitablyincurred in handling it, and not with questions of capital cost and allied matters. It details the causes of loss of heat inevitably incurred in the use of any other form of fuel, estimates their respective amounts, and traces the stages by which the heat generated at a central boiler-house is frittered away on its way to the rooms where it is required. The principal features which enable electrical power whensuitably installed to compete withother fuels are its 100 per cent technical efficiency, its instantaneous control, and the very low time-lag and absorption. It is shown that, owing mainly to these features, an amount of heat fully equivalent to the energy of the electrical current used can be delivered at the exact time only when it is required, thereby avoiding the waste caused essentially by the lack of accurate timing inevitably associated with all systems in which heat is generated in and distributed from acentral boiler, whether or not this iselectrically heated. In this sense electricity, locally applied, is the only means by which an overall ?efficiency? of 100 per cent can be rationally claimed for an entireinstallation?in the sense thatthe amount of electrical energy used isequal to the bare minimum of theheat physically necessary to secure the desired result. The overall efficiency of the heating process by other media is determined as thecontinuous product of numerousdetailed efficiencies (corresponding tothe various stages of loss), each of which is so defined that their continuous product may be equal to a final ?overallefficiency? representingthe ultimate ratio between the heat physicallynecessary for securing the- desired result and that in the fuel purchased. Representative maximum, medium, and minimum values are in all cases given of each of these factors where they areliable to wide variation, and the tables are drawn up in such a form that they can readily be corrected for any variation in these assumed values. A close comparison ismade between the features of electricityand gas (herein called the ?mobile fuels?) as heating agents; also between the operating characteristics of the ?portable fuels??oil and coke. The labour involved in handling thefuel in each case is considered in detail. A sharp distinction is drawn between the relative costs in the respective cases of continuous and intermittent heating. It is inthe latter that the economy of electric heating showsto greatest advantage; the reasons for this are given. Explanationsare advanced of the reasons why instantaneous control, suchas is only obtainable by electricity, is of great importance in restricting the unnecessary use of heat and at the same time in supplying an adequate amount for main taining comfort conditions during all times of actualoccupation, and onlyduring those times. Numericaltables and diagrams are given showing theprogressive loss of heat in the various stages through which the heat passes, and explanations are given of the details of thecalculations of the heat quantities really necessary for maintaining the required temperatures, as well as of the proportions inevitably dissipated in the process of delivering heat from a central point to the rooms. The ratio between these iscalled the ?occupation efficiency?, the incidence of which on the calculated result is fully explained. Finally a table is given in which, assuming fixed prices for the crude heat, average medium values for the various factors involved and theoretical perfection of the heating result for an assumed period, the relative annual costs of heating 1 000 cubic feet of average space by the various media is calculated. It is em