Archimedes' screw

An Archimedes' screw is a hydraulic machine composed of an outer cylinder and an inner cylinder with helical blades. It can be operated both as a pump and a power generator, though it has been used for other purposes, such as drainage and sewage management.

The origins of the water screw are unknown. Archimedes of Syracuse is traditionally credited with inventing the water screw, but other academics argue Archimedes found the Egyptians already using the screw. The earliest mention of the screw is from between 250 and 220 BC, and archaeological remains of water screws in Europe and Asia suggested that it was diffused across the territories of the Roman Empire, though the screw largely fell out of use in Europe in the third century AD. However, it resurfaced during Renaissance, with the screw introduced to other regions such as China and Japan. In 1991, a patent for the Archimedes screw turbine was filed, and the testing was done between 1993 and 1995.

As a machine used for lifting water from a low-lying body of water into irrigation ditches, it lifts water by turning a screw-shaped surface inside a pipe. In the modern world, Archimedes' screw pumps are widely used in wastewater treatment plants and for dewatering low-lying regions. Run in reverse, Archimedes screw turbines act as a small hydroelectric powerplant that can be applied even in low head sites. Such generators operate in a wide range of flows (0.01 m3/s to 14.5 m3/s) and heads (0.1 m to 10 m), including low heads and moderate flow rates that are not ideal for traditional turbines and not occupied by high performance technologies.