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Introduction
 Ch1 - Welcome to Microhydro
 Ch2 - Getting the service you want
 Ch3 - Determining your power potential
 Ch4 - About battery-charging systems
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Ch5- About AC systems
Ch6- Plumbing
Ch7- Case studies
Ch8 - Regulations and incentives


The following in an excerpt from Chapter 4.3 Turbines: high head, low head.
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There are several different kinds of turbines that are appropriate for battery charging systems.  The classic microhydro unit for a battery-based system is an impulse turbine, a design that relies on relatively high head and low flow.

An impulse turbine gets its energy from the impact of a spray of water.  A nozzle, also called a jet, at the end of the pipeline converts the water under pressure into a fast moving jet of water, which sprays little cups on the turbine wheel, also called a runner.  The kinetic energy from the water spins the runner.

This kind of turbine has the advantage of being able to operate at a wide variety of heads and flows, and thus a single model of wheel can be used in many sites.

Common impulse turbines are the Pelton, the Turgo and the Crossflow, the latter being a popular home-built design.  

Turbines are classified according to the head that they require.  Of the three impulse turbines mentioned, the Crossflow turbine is used for the largest flow, lowest head situations in the range of 4 to 20 feet.  The Pelton is used in situations where the head is as high as 600 feet, and is especially designed for low flow.  The Turgo has similar head requirements, but can handle more flow than the Pelton. 

Low head for battery charging systems means heads under 10 or 12 feet. Turbines that work in this range are reaction type turbines, for example the LH-1000 from Energy Systems and Design. 

The Aquair offers a completely different solution.  The Aquair has a propeller that sits directly in the creek and spins with the current of the water.

Some of these turbines are described below.  This section will also explore building your own.  After all, water turbines have been around for thousands of years.


4.3.1 High head turbines

Pelton

The original and classic microhydro turbine design is the Pelton. Invented in the 19th century by directing water jets used in hydraulic mining onto overshot water wheels, it provided a way to get the high rotating speeds necessary for electrical generating.   

It is used especially for low flow battery-charging systems, where the head is over 30 feet or so.  It requires at least ten feet of head. 

 An example of a Pelton wheel is the four-inch Pelton designed by Harris Hydroelectric.  It will generate with as little as 2 US gpm, and it will accommodate up to four half-inch jets to handle more flow. 


This Harris Hydroelectrc unit (left) has four jets and a permanent magnet alternator mounted on the top.  The runner (right) handles high pressure water.

The maximum power potential of the Harris Hydroelectric turbine is 1 kilowatt.  If your site has a lot more potential, you would probably benefit from choosing a larger wheel, or choosing a Turgo design which can handle more flow. 

The Harris Hydroelectric Pelton comes with a choice of alternators: a Harris Hydroelectric permanent magnet alternator, a Motocraft 80 amp alternator or a 30 amp Delco alternator, which will affect the power output.  These alternators will be covered in more detail in Charging batteries with alternators.

Turgo

The Turgo runner is a refinement of the Pelton, where the jets direct water at the runner at an angle.  The Turgo is used especially for situations with high water flows; the design allows for larger jets.  Because Turgos can use more water, significant power can be generated with less head.  This results in shorter penstocks, all things being equal. 

In addition the Turgo is rugged and can be used as a small and inexpensive AC turbine for the right kind of site, making it a commonly used turbine. 

An example of a Turgo turbine is the Stream Engine from Energy Systems & Design, a Canadian company who have been producing microhydro turbines since 1980. Their turbines have a 4-inch bronze runner.

 
This Stream runs two Stream Engines protected in a plexiglass covering(left).  A view from the underside of the unit (right) shows off the 4-inch bronze Turgo runner.

The Stream Engine can produce over 700 kW/hr per month. It can be equipped with up to four universal nozzles  that are adjustable with threaded inserts from 1/8 to a maximum of one inch.  In comparison, the Harris Hydroelectric Pelton can only accommodate 1/2-inch jets.

Like the Harris Hydroelectric Pelton, a variety of alternators can be fit the turbine, such as an automotive alternator or a brushless permanent magnet alternator.

The Waterbaby

Perhaps the smallest impulse turbine is the Waterbaby by Energy Systems and Designs.  There is no other way to describe it -- it’s simply cute.  The runner is only 2 inches across, with a design somewhere in between a Pelton and a Turgo.  It will efficiently produce outputs down to 18 kWhrs/month and costs about CAN$1750. 


The Waterbaby with alternator (left) and the two-inch runner (right).

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