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Francis Turbine
The Francis turbine is a reaction turbine, which means that the water changes pressure as it moves through the turbine, giving up its energy. First, high pressure water enters the turbine through the spiral casing surrounding the guide vanes. Then water passes through guide vanes where it is directed to strike the blades on the runner at optimum angles. As the water flows through the runner its pressure and angular momentum reduces. This reduction imparts reaction on the runner and power is transferred to the turbine shaft.
Applicable Range Head: 20-200m Flow: 0.15-10m3/s
- Most widely used turbine in the world. (70-80%)
- Applicable head and flow range is very wide.
- As a type of reaction turbine, the draft tube can be used to effectively increase net head.
- Peak efficiency is highest among all turbine types. (85-94%)
- Due to its complex design and large number of moving parts, maintenance and repair can be significant.
Inline Linkless Francis Turbine
The Inline Linkess Francis turbine was jointly developed between Tokyo Electric Power Company, Tokyo Electric Generation Company and Tanaka Hydropower and commercially released in 2007. It was developed expressly for the purpose of installation within space restricted areas such as existing pumping stations, water treatment facilities, and drainage systems. The applicable head and flow range is narrower than a conventional Francis turbine; however, it maintains the pros of a Francis turbine while offering many additional advantages due to its simplified guide vane structure and inline design.
Applicable Range Head: 10-80m Flow: 0.15-1.0m3/s
- With its inline cylindrical design, the required space for installation is quite small and can be easily installed into existing water systems such as water supply stations, water treatment facilities, and drainage systems.
- Due to the simplification of the guide vane structure, the cost is significantly lower than a conventional Francis turbine.
- Since there are less moving parts than a conventional Francis turbine, maintenance and repair costs are lower.
- As a type of reaction turbine, the draft tube can be used to effectively increase net head.
Linkless Hydropower brochure (English)
Inline Linkless Francis vs. conventional Francis turbine comparison chart
Cross-flow Turbine
The cross-flow turbine consists of a cylindrical runner with a horizontal shaft, composed of numerous blades, arranged radially and tangentially. Unlike most water turbines, which have axial or radial flows, in a cross-flow turbine the water passes through the turbine transversely, or across the turbine blades. The water flows first from the outside of the turbine to its inside, and then after passing the runner, it leaves on the opposite side. Going through the runner twice provides additional efficiency.
Applicable Range Head: 2-60m Flow: 0.04-10m3/s
- A very cost effective solution
- Installation, operation, and maintenance is very easy due to its simple design.
- A very flat efficiency curve under varying load; efficiency remains high in low flow conditions.
- Peak efficiency is less than Francis, Pelton and turgo impulse turbines.
Cross-flow turbine brochure (Japanese)
Pelton Turbine
The Pelton turbine extracts energy from the impulse of moving water, as opposed to reactive turbines such as the Francis turbine. Water passes through a nozzle(s) and strikes the buckets arranged on the periphery of a runner which causes the runner to rotate, producing mechanical energy. The buckets were designed so that when the rim runs at half the speed of the water jet, the water leaves the runner with very little speed, extracting almost all of its energy, and allowing for a very efficient turbine. The Pelton turbine can be controlled by adjusting the flow of water to the bucket by use of a deflector.
Applicable Range Head: 30-500m Flow: 0.015-2m3/s
- A very flat efficiency curve under varying load; efficiency remains high in low flow conditions.
- The number of nozzles can be increased to raise efficiency. (up to 6 nozzles)
- Generator cost are higher since its rotational frequency is quite low. (speed increaser is usually necessary)
Turgo Impulse Turbine
The turgo turbine is type of impulse turbine that is similar to the Pelton turbine but can handle higher flow rates although it is slightly less efficient. The incoming water jet from the nozzle strikes the plane of the runner on one side (usually at an angle of about 25°) and exits on the other side. Since the water jet interferes less with the runner than the Pelton design, it can handle more flow than a same diameter Pelton runner, leading to reduced generator and installation costs. Since the runner of a turgo turbine is basically a Pelton runner cut in half, a turgo turbine can generate the same power as a Pelton runner with twice the diameter and thus has twice the specific speed .
Applicable Range Head: 35-300m Flow: 0.2-4m3/s
- A very flat efficiency curve under varying load; efficiency remains high in low flow conditions.
- To increase efficiency, up to 2 nozzles can be used.
- Installation, operation, and maintenance is very easy due to its simple design.
- Unlike the Pelton turbine, its rotational frequency is high thereby reducing generator costs. (usually a speed increaser is unnecessary)
Turgo Impulse Turbine brochure (Japanese)
