Water Power
a general phrase the energy of moving water may be the water must have what is technically higher to a lower level; in other words utilized. called a "head." Such conditions more sufficient to have water falling from a energy effectual, it is necessary and
To make such a source of sufficient to have water falling from a though in many cases the fall is so slight or less favorable exist in all streams, construction of dams or otherwise, the energy may be stored up as potential construction of dams or otherwise, the can be obtained. In such cases, by the energy in a large mass of water to be so small that practically no useful work and therefore the volicity of the water though in many cases the fall is so slight can be obtained. In such cases, by the transformed at will. stream is one which is directly available for performing useful work, it is usually advisable to collect the water in reservoirs, since the quantity of flow of most Even where the streams varies co
Even with such precautions the considerably with the seasons. supply of water may be far from unisupply of water may be far from uniweather. season and hardly filling them in the dry Given the available fall and the total quantity of water which flows in a given time, the potential energy which is lost formed into the kinetic energy of runis expresed in foot pounds by the product of the mass in pounds multiplied ning water, while part is transformed by the height through which the water tion could be wholly transformed into has fallen. This energy is mainly transuseful work, the water would be brought into heat and sound. If the former porrealized, we see that the available energy to rest; but as this is never practically realized, we see that the available energy to rest; but as this is never practically effected, the most common are what are known as water wheels, in their several forms of turbines, undershot wheels, Of the various machines by which the last three are very similar in construction, and are made to rotate round a horizontal axis by the action of the of a fall of water is much smaller than the total transformable energy.
Of the various machines by which the equal intervals more or less radically round the circumference of the wheel. cable to falls of from 12 to 60 feet, the In the overshot wheel, which is appliwater on the floats which are fixed at partitions in the circumference, and by its weight, aided in some measure by the water on the floats which are fixed at horizontal axis by the action of the WATER SCORPION initial impact, drives the wheel round, the upper part moving in the direction of the flow water. The water escapes below as each partition during the rotation of the wheel is turned face downward. The breast wheel acts very similarly, and is applicable to falls smaller than those for which the overshot wheel can be conveniently used. The upper circumference of the wheel is higher than the feeding channel of the water, which enters at a point usually a little above the center of the wheel. The undershot wheel is used where the momentum only of the current can be utilized, the impact of the water upon the floats forcing the wheel round. There is necessarily a considerable waste of power in the undershot wheel, which was to a certain extent remedied by Poncelet when he introduced curved instead of plane floats.
The turbine or vortex wheel is usually horizontal, rotating round a vertical axis.
In the original form of turbine, invented by Fourneyron in 1823, water was introduced from above into a central chamber, from which it radiated through curved radial chambers. From these it was projected on the curved floats of the wheel, which was forced round by the reaction of the escaping water.
Though it is from rivers and streams that we derive all the water power which is profitably used, there is no doubt that in the tides we have a great and remarkably constant source of energy, if it could be utilized. Suggestions have not been wanting as to methods for utilizing this energy, but as yet nothing practical has resulted.