Cross-flow turbine

Michell obtained patents for his turbine design in 1903, and the manufacturing company Weymouth made it for many years.

Today, the company founded by Ossberger which bears his name is the leading manufacturer of this type of turbine.

The cross-flow turbine is a low-speed machine that is well suited for locations with a low head but high flow.

Although the illustration shows one nozzle for simplicity, most practical cross-flow turbines have two, arranged so that the water flows do not interfere.

The subdivided regulating unit, the guide vane system in the turbine's upstream section, provides flexible operation, with 33, 66 or 100 % output, depending on the flow.

The turbine consists of a cylindrical water wheel or runner with a horizontal shaft, composed of numerous blades (up to 37), arranged radially and tangentially.

These divide and direct the flow so that the water enters the runner smoothly for any width of opening.

Since it has a low price, and good regulation, cross-flow turbines are mostly used in mini and micro hydropower units of less than one thousand kW and with heads less than 200 m (660 ft).

The efficiency of a turbine determines whether electricity is produced during the periods when rivers have low flows.

Due to its excellent behaviour with partial loads, the cross-flow turbine is well-suited to unattended electricity production.

Other turbine types are clogged more easily, and consequently face power losses despite higher nominal efficiencies.