Twentieth Century Inventions: A Forecast

by George Sutherland

The anemometer of the "Robinson" type, having four little hemispherical cups revolving horizontally, furnishes the first hint of another principle of construction adapted to the generation of electricity. Some years ago a professor in one of the Scottish Universities set up a windmill which was simply an amplified anemometer, and connected it with several of Faure's storage batteries for the purpose of furnishing the electric light to his residence. His report regarding his experience with this arrangement showed that the results of the system were quite satisfactory.

In this particular type of natural motor the wind-wheel, of course, is permanently set to run no matter from what direction the wind may be blowing. Tests instituted with the object of determining the pressure which the wind exerts on the cup of a "Robinson" anemometer have shown that when the breeze blows into the concave side of the cup, its effect is rather more than three times as strong as when it blows against the convex side. At any given time the principal part of the work done by a windmill constructed on this principle is being carried out by one cup which has its concave side presented to the wind, while, opposite to it, there is another cup travelling in the opposite direction to that of the wind but having its convex side opposed.

The facts that practically only one sail of the mill is operative at any given time, and that even the work which is done by this must be diminished by nearly one-third owing to the opposing "pull" of the cup at the opposite side, no doubt must detract from the merits of such a wind-motor, judged simply on the basis of actual area of sail employed. But when the matter of cost alone is taken as the standard, the advantages are much more evenly balanced than they might at first sight seem to be.

The cup-shaped sail may be greatly improved upon for power-generating purposes by adopting a sail having a section not semicircular but triangular in shape, and by extending its length in the vertical direction to a very considerable extent. Practically this cheap and efficient wind-motor then becomes a square or hexagonal upright axis of fairly large section, to each side of which is secured a board or a rigid sheet-metal sail projecting beyond the corners. The side of the axis and the projecting portion of the sail then together form the triangular section required.

For the sake of safety in time of storm, an opening may be left at the apex of the angle which is closed by a door kept shut through the tension of a spring. When the wind rises to such a speed as to overbalance the force of the spring each door opens and lets the blast pass through. One collateral advantage of this type of windmill is that it may be made to act virtually as its own stand, the only necessity in its erection being that it should have a collar fitting round the topmost bearing, which collar is fastened by four strong steel ropes to stakes securely set in the ground. The dynamo is then placed at the lower bearing and protected from the weather by a metal shield through which the shaft of the axis passes.

For pumping, and for other simple purposes apart from the use of the dynamo, a ready application of this form of wind-engine with a minimum of intricacy or expense may be worked out by setting the lower bearing in a round tank of water kept in circular motion by a set of small paddles working horizontally. Into the water a vertically-working paddle-wheel dips, carrying on its shaft a crank which directly drives the pump. This simple wind-motor is particularly safe in a storm, because on attaining a high speed it merely "smashes" the water in the tank.

Solar heat is one of the principal sources of the energy to be derived from the wind. Several very determined and ingenious attempts at the utilisation of the heat of sunshine for the driving of a motor have been made during the past century. As a solution of a mechanical and physical puzzle, the arrangement of a large reflector, with a small steam-boiler at the focus of the heat rays thrown by it, is full of interest. Yet, when a man like the late John Ericsson, who did so much to improve the caloric engine, and the steam-ship as applied to war-like purposes, meets with failure in the attempt to carry such an idea to a commercially successful issue, there is at least prima facie evidence of some obstacle which places the proposed machine at a disadvantage in competition with its rivals.

The solar engine, if generally introduced, would be found more intermittent in its action than the windmill—excepting perhaps in a very few localities where there is a cloudless sky throughout the year. The windmill gathers up the power generated by the expansion of the air in passing over long stretches of heated ground, while a solar engine cannot command more of the sun's heat than that which falls upon the reflector or condenser of the engine itself. The latter machine may possibly have a place assigned to it in the industrial economy of the future, but the sum total of the power which it will furnish must always be an insignificant fraction.

The wave-power machine, when allied to electric transmission, will, without doubt, supply in a cheap and convenient form a material proportion of the energy required during the twentieth century for industrial purposes. Easy and effective transmission is a sine quâ non in this case, just as it is in the utilisation of waterfalls situated far from the busy mart and factory. Hardly any natural source of power presents so near an approach to constancy as the ocean billows. Shakespeare takes as his emblem of perpetual motion the dancing "waves o' th' sea".

But the ocean coasts—where alone natural wave-power is constant—are exactly the localities at which, as a rule, it is the least practicable to build up a manufacturing trade. Commerce needs smooth water for the havens offered to its ships, and inasmuch as this requirement is vastly more imperative during the early stages of civilisation than cheap power, the drift of manufacturing centres has been all towards the calm harbours and away from the ocean coasts. But electrical transmission in this connection abolishes space, and can bring to the service of man the power of the thundering wave just as it can that of the roaring torrent or waterfall.