Watermill

A watermill is a mostly historical technical system, which is driven by a hydraulic machine by water power.

In the system it may be a mill in the strict sense, in the ground or something is broken ( grinding mill ), or to a mill to be driven in the other machines (eg sawmill, grinding mill, blacksmith / hammer mill, pumping station ).

For the implementation of the Water energy into mechanical work are at historic mills almost exclusively water wheels used; these have recently been replaced often by water turbines.

The water needed for driving ( surcharge water) is usually taken from a stream. Depending on local conditions are to increase the height of fall and for storing water ponds, dams, canals or other water structures required see also Battle (water structure ).

History

Water mills are very old used by people machines that were not driven by muscle power of humans or animals. By water power driven waterwheels for irrigation ( " Noria " ) are already known from the 5th century BC from Mesopotamia. First grinding mills with water power drive are assigned to the 3rd century BC from Asia ( China). Even the ancient Egyptians, Persians, and later the Greeks and Romans used water mills, as it is known from a poem by Antipater of Thessalonica, a travelogue of the geographer Strabo and the detailed technical descriptions of Philo of Byzantium or Vitruvius.

In Barbegal in southern France, a Roman mill complex with 16 water mills was found which dates from the 3rd century and was powered by an aqueduct.

The Romans brought the water mill technology to Germany, as can be seen by a Fund at Düren in the Rhineland from the time of Christ's birth. In a trip report Mosella from the year 368, the Roman officials Ausonius mentions first mills on Kyll and Ruwer tributaries, the Moselle. In the Frankish Salic law people from around 450 water mills are mentioned with dam ( Farinarius ). The oldest documented by archaeological finds water mill in Germany according to the above in Düren was in the 6th century in the Alemannic settlement agent in Mayrhofen leek home.

From the Middle Ages water wheels were used as drive of grinding mills and various other machines throughout Western and Central Europe to the North and Baltic Sea region.

With the increasing spread the rulers and landlords used the water mills as a source of income for taxes. In addition to the mill law and the mill compulsion that was true for mills with drives of all kinds and especially for flour mills were water mills, some additional rules are important: mostly was for the use of storage right to a special levy due ( water knowledge, water rate, ...).

From the 17th century water- power driven machines ( " water art" ) also found strong use in the mining and pre-industrial trade. With industrialization competed the water mills, as well as wind and gin mills, increasingly versatile and powerful steam mills, with internal combustion engines and, finally, with electrically driven mills. The large industrial mills displaced more and more small classic craft mills; these were uneconomical, so that there was a " death mill " end of the 19th century.

With the increasing electrification put those water mills that remained in operation, its water power drive many of the Waterwheel on one of the newly developed, more efficient water turbine to the electricity to drive the electrical machinery inside the mill produced ( turbo -electric drive ). Means of a generator Surplus could be fed into the electrical grid. The latter function was often the main purpose after the milling was abandoned; Once a water mill became the pure water power plant.

Having already many water and wind mills were shut down and demolished, was remembered in the middle of the 20th century the importance of these structures as a technical monument. Some of the mills could thus be obtained in more or less original condition as art museum or for other purposes ( as a restaurant or the like often ).

Since the late 20th century historic watermills be revived reinforced by stepping importance of carbon-neutral renewable energy and converted to small hydropower plants. This is based on modern water wheels that maintain the historic nature of the mill and be the monument justice, but their effectiveness in the water turbines rarely met.

Construction and Technology

The determining factor for the achievable performance are the drop height, the flow rate, the amount of water and the efficiency.

A water mill building usually consists of three parts, which are explained below:

• Hydraulic structures for the management and storage of water surcharge
• Drive consisting of hydrogen combustion engine ( water wheel, water turbine) and the power transmission to the driven machine
• Production plant ( mill in the narrow sense ) with the mills or other machines

Water Retaining Structures

The simplest form of watermill is that in which the mill is located directly at the banks of the watercourse driving without whose course is changed. The mill can swim even as a ship mill on the water surface in the extreme. The water is not diverted or dammed, the water wheel appeared only with the blades at the bottom into the water ( deep - or undershot water wheel ). Such mills are not very efficient and they charge accordingly for a wide wheel and a larger river, which always results in enough water.

In order to build water mills also in watercourses with a little water or with low gradient, it is necessary to strengthen the power of water by the drop height and thus the pulse / pressure of water surcharge is increased. The waterwheel is applied laterally at the level of the shaft ( mittelschlächtig ) or from the top ( overshot ) with the force of water.

The increase in the height of fall is done either by the fact that a partial stream of the driving watercourse of it is diverted and ( often called " mill stream " ) in a channel is performed less frequently, a aufgeständertes canal or in an underground tunnel with a lesser gradient parallel. When the desired height difference is reached, the water is passed over the mill wheel and added to the water running again.

The other way to increase the height of fall, it to dam up the stream by a dam or weir is. The barrage, also called mill dam, has in addition to increasing the drop height and the positive effect that the dam (Mill Pond) water is stored that can be retrieved when needed. Thus, the mill is in times when the dining watercourse leads little water, less water level dependent.

Particularly in mining high effort were driven for the storage and management of water power for the fountains and partially branched systems far from reservoirs (artificial ponds ), channels ( Art ditches) and tunnels ( crispness, watercourse ) were created. Well-known examples of such systems are the Upper Harz Water Regale or the Freiberg district water supply.

Hydraulic power engines

To implement the flow energy of water into mechanical work requires a hydraulic machine. For this earlier water wheels were almost always used, and the design of the wheel was adapted to the conditions of the water power and the driven machine.

Only in rare special cases, very simple in their construction, but little effective Gnepfen were used.

From the 19th century onward, especially in mining, isolated by steam engines derived water motors.

In more recent times (see story) many water mills were modernized and the water wheels were replaced by water turbines.

Mill / production

As with other mills can be, even at water mills to mills in the narrower or broader sense. That is, either something is here ground or comminuted (eg, grain mill, oil mill) or water power is used as the drive for various working machines (eg sawmill, hammer mill, grinding cotta ). The latter use was common at water mills than for wind or gin mills.

Advantages and disadvantages compared to other types of mills

Compared to other types of mills have water mills a number of advantages and disadvantages:

The biggest advantage of hydropower is the fact that this as a natural and renewable source of energy is in principle (except for periods of frost ) unlimited and free. While this is true also for windmills as a rival to the water mills; however, depend watermills this more from the weather. Of course, the amount of available stationary surcharge water even when water mills of seasonal variations in rainfall dependent, but these are not quite as fast as changeable as the wind, and in contrast to the wind, the water may get jammed, stored in a mill pond and retrieved from a demand be.

Condition of your use of hydropower is the requirement that a water body with sufficient slope is available, the enough amount of water leads also in dry periods. Since this condition is not met in many places in the lowlands, where, however, often the wind blew stronger and more uniform, the windmill has in the coastal, shallow regions established as the predominant type of mill, in the more mountainous regions of the watermill.

The problem of the operation of water mills in areas where there are regular in winter periods of frost, as a water mill operation is not possible at times, where the watercourse on which the mill in question is, is iced. This disadvantage is especially in the cases a negative effect, in which the water is needed as a driving force ( eg for the Sawmill ).

An attempt to combine the advantages of wind and water mill, wind mill water. This hybrid form is suitable only for a few sites, there are very few mills of this type

Special designs

Through some special designs was trying to adapt to the local water mills offer of water power:

• Tide Mill - drive not by a river but by tidal current (ebb and flood )
• Schiffmühle - floating mill with water wheel tiefschlächtigem
• Wind Water Mill - a combination of a water mill with a windmill