The following in an excerpt from Chapter 4.3 Turbines: high 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
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
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.
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
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 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