Waterwheels some of the instruments used to exploit water power

Water constitutes an extremely powerful source of energy, for the simple fact that it is a good 800 times denser than air, and consequently the impact and thrust it can supply to an appropriate rotating paddle can be very strong. In fact, the potential power supplied by water is much greater than that to be derived from wind Una sega idraulica disegnata da un anonimo ingegnere senese del Rinascimento . For administrative or social and cultural reasons, these types of water mill have been almost completely abandoned, in spite of the fact that they are undoubtedly both extremely simple and technically valid. We know that the first known waterwheel was on a vertical axis while those under consideration here, transformed to a horizontal axis, represent an evolution. If we have at our disposal a small watercourse, such as a brook, the choice of the type of system is made on the basis of the waterfall, so that for high waterfalls we can use the overshot waterwheel, for medium falls the breast wheel, and for low falls the undershot wheel. The major disadvantages are the dimensions of the structures in relation to the limited power supply, and the need to build intake constructions such as feed channels. Nevertheless, this type of technology has the advantage of being able to exploit even small streams with a limited rate of flow, while the simplicity of construction means that a moderate yield can even be provided by a self-built system. While they are not extremely powerful, the mechanical energy produced by this type of system can be sufficient to run small craft workshops situated in remote areas or in technically underdeveloped communities. As well as this, the system can also be appropriately modified so that the wheel powers an electrical generator for the provision of electrical energy. S.P.