Low Head (LH) Info

The PowerSpout LH is a propeller type turbine. This type gives the maximum shaft rpm from the lowest head of water. The propeller is completely submerged in water (unlike the pelton and turgo turbines that run in air, driven by a jet of water).

The Powerspout LH propeller is situated at the top end of a tube that connects two bodies of water. The head of pressure on the propeller is actually created by the suction effect of water in the draft tube below the turbine. It is important that this tube is full of water, so both the turbine at the top, and the mouth of the tube at the bottom must be completely submerged in water.

The drive shaft connects the propeller to an alternator above the water level, which produces electricity. The current is rectified within the unit to DC suitable for a Maximum Power Point Tracking battery charge controller or a grid-tied inverter. Contrary to popular myth, DC is more efficient than AC for transmission of power in cables.


One advantage of situating it at the top of the draft tube is that the PowerSpout LH turbine is very unlikely to suffer flooding at times of exceptionally high rainfall. The rising water level in the tailrace will however reduce the operating head, and therefore the power output (Watts).

A PowerSpout LH turbine is more likely to be closer to your home than a PowerSpout PLT or TRG. LH turbines will be installed on larger streams which tend to meander down valley bottoms where homes are typically closer. PowerSpout LH turbines are best employed by locating a part of the river that drops 2-5 m quickly (over a set of rapids).

The generation capacity of your site is determined by the water supply, primarily by the vertical distance the water falls (head) and how much water flows in a given time (flow rate). Please note that the "head" for the LH is the drop in height between the water surface at the turbine and the water surface at the tailrace.

Required head and flow per turbine:

Head: 1 - 5 meters

Flow: 14 - 55 litres/second