People use natural sources of energy to complement human and animal work power. Water Mills were one of the first mechanical devices to utilise renewable energy sources. Water wheels were built on the fast-flowing rivers or streams, which were constructed to control water levels and flow speed.
What is a water wheel?
A device that converts the energy of flowing water into proper forms of power, often in a watermill. It consists of a wheel with a few blades and buckets arranged outside.
Almost all wheels work by water from a millpond, formed when obstructed by a flowing stream.
Mill race is a channel for the water flowing to or from a water wheel.
Headrace is the channel bringing water from the mill pond to the water wheel.
A tailrace carries water after it has left the wheel.
Water wheels were first used in ancient times, and they became widespread in the Middle Ages. The wheel power of standing water is transferred to the upright shaft that rotates the millstone inside the mill by gears and shaft extending from the axle. The millstones are placed in casings on the top floor of mills. Then, with the help of a hopper, grains are fed into them, including the use of shafts or slides, the ground material is transferred into the storage chests.
Water wheels were most commonly used in green mills, but they were also found in iron forges, sawmills and mines.
Advantages of waterwheel:
- It has a high moment of inertia, making it suitable for direct drive of slowly-rotating machines and machines with alternate resistance.
- Waterwheels have a simple hydraulic design and construction.
- They are suitable for small, highly alternating water quantities.
- Well constructed water wheels have up to 80% rate of efficiency.
- They have low maintenance expenditures, are very easy to repair, and have a long lifespan.
- Water wheels have a good storage of water and therefore producing energy is possible with the help of reservoirs.
Disadvantages of water wheel:
- They are heavy and have a large space requirement, as well as there are losses with overshot wheels due to the height and suspension.
- The rotational speed should be as low as possible to avoid fast emptying of the scoops due to greater centrifugal forces.
- A high and good initial torque is required. Water wheels are gravity machines and are more efficient than turbines when well constructed. The conversion into other forms of energy is quite difficult or impossible due to the low rotational operating speed.
- The long-distance transference of the energy by water wheels is not possible.
- They do require expensive hydrological construction measures. Due to this, utilisation of hydromechanical energy may not be possible.
At last, water wheels fit the best for application in small-scale mining due to the number of possibilities to use them in the direct mechanical drive of various mining and mineral extracting machines. Moreover, despite the relatively high investment costs, the water wheels are effortless to manufacture locally using domestic construction materials. Also, they are distinguished by low maintenance and repair costs.