The ease with which a gas-engine can be installed, compared with a steam-engine is self-evident. In places where illuminating gas can be obtained and where less than 10 to 15 horse-power is needed, street-gas is ordinarily employed. [A] The improvements which have very recently been made in the construction of suction gas-generators, however, would seem to augur well for their general introduction in the near future, even for very small powers.
The installation of small street-gas-engines involves simply the making of the necessary connections with gas main and the mounting of the engine on a small base.
An economical steam-engine of equal power would necessitate the installation of a boiler and its setting, the construction of a smoke-stack, and other accessories, while the engine itself would require a firm base. Without exaggeration it may be asserted that the installation of a steam-engine and of its boiler requires five times as much time and trouble as the installation of a gas-engine of equal power, without considering even the requirements imposed by storing the fuel (Fig. 1). Small steam-engines mounted on
their own boilers, or portable engines, the consumption of which is generally not economical, are not here taken into account.
Fig. 1.—30 H.P. Gas-engine and suction gas-producer.
Fig. 1a.—30 H.P. Steam-engine, boiler and smoke-stack.
So far as the question of cost is concerned, we find that a 15 to 20 horse-power steam-engine working at a pressure of 90 pounds and having a speed of 60 revolutions per minute would cost about 162⁄3 per cent. more than a 15 horse-power gas-engine, with its anti-pulsators and other accessories. The foundation of the steam-engine would likewise cost about 162⁄3 per cent. more than that of the gas-engine. Furthermore the installation of the steam-engine would mean the buying of piping, of a boiler of 100 pounds pressure, and of firebrick, and the erection of a smoke-stack having a height of at least 65 feet. Beyond a little excavating for the engine-base and the necessary piping, a gas-engine imposes no additional burdens. It may be safely accepted that the steam-engine of the power indicated would cost approximately 45 per cent. more than the gas-engine of corresponding power.
The cost of running a 15 to 20 horse-power steam-engine is likewise considerably greater than that of running a gas-engine of the same size. Considering the fuel-consumption, the cost of the lubricating oil employed, the interest on the capital invested, the cost of maintenance and repair, and the salary of an engineer, it will be found that the operation of the steam-engine is more expensive by about 23 per cent.