Most micro hydro systems require a pipeline to feed water to the turbine. The
exception is a propeller machine with an open intake. The water should pass first
through a simple filter to block debris that may clog or damage the machine. The intake
should be placed off to the side of the main water flow to protect it from the direct
force of the water and debris during high flows.
It is important to use a pipeline of sufficiently large diameter to minimize friction losses
from the moving water. When possible, the pipeline should be buried. This stabilizes
the pipe and prevents critters from chewing it. Pipelines are usually made from PVC or
polyethylene although metal or concrete pipes can also be used. The article on hydro
system siting in Home Power #8 describes pipe sizing.
Turbines
Although traditional waterwheels of various types have been used for centuries, they
aren't usually suitable for generating electricity: They are heavy, large and turn at low
speeds. They require complex gearing to reach speeds to run an electric generator.
They also have icing problems in cold climates. Water turbines rotate at higher speeds,
are lighter and more compact. Turbines are more appropriate for electricity generation
and are usually more efficient.
There are two basic kinds of turbines: impulse and reaction.
Impulse machines use a nozzle at the end of the pipeline that converts the water
under pressure into a fast moving jet. This jet is then directed at the turbine wheel
(also called the runner), which is designed to convert as much of the jet's kinetic
energy as possible into shaft power. Common impulse turbines are pelton, turgo and
cross-flow.
In reaction turbines the energy of the water is converted from pressure to velocity
within the guide vanes and the turbine wheel itself. Some lawn sprinklers are reaction
turbines. They spin themselves around as a reaction to the action of the water
squirting from the nozzles in the arms of the rotor. Examples of reaction turbines are
propeller and Francis turbines.
Turbine Applications
In the family of impulse machines, the pelton is used for the lowest flows and highest
heads. The cross-flow is used where flows are highest and heads are lowest. The
turgo is used for intermediate conditions. Propeller (reaction) turbines can operate on
as little as two feet of head. A turgo requires at least four feet and a pelton needs at
least ten feet. These are only rough guidelines with overlap in applications.
The cross-flow (impulse) turbine is the only machine that readily lends itself to user
construction. They can be made in modular widths and variable nozzles can be used.
Most developed sites now use impulse turbines. These turbines are very simple and
relatively cheap. As the stream flow varies, water flow to the turbine can be easily
controlled by changing nozzle sizes or by using adjustable nozzles. In contrast, most
small reaction turbines cannot be adjusted to accommodate variable water flow. Those
that are adjustable are very expensive because of the movable guide vanes and
blades they require. If sufficient water is not available for lull operation of a reaction
machine, performance suffers greatly.
An advantage of reaction machines is that they can use the full head available at a
site. An impulse turbine must be mounted above the tailwater level and the effective
head is measured down to the nozzle level. For the reaction turbine, the full available
head is measured between the two water levels while the turbine can be mounted
well above the level of the exiting water.
This is possible because the "draft-tube" used with the machine recovers some of the
pressure head after the water exits the turbine. This cone-shaped tube converts the
velocity of the flowing water into pressure as it is decelerated by the draft tube's
increasing cross section. This creates suction on the underside of the runner.
There are more micro hydro components discussed on the next page.
< Micro Hydro Part 1 Micro Hydro Components Con't >
exception is a propeller machine with an open intake. The water should pass first
through a simple filter to block debris that may clog or damage the machine. The intake
should be placed off to the side of the main water flow to protect it from the direct
force of the water and debris during high flows.
It is important to use a pipeline of sufficiently large diameter to minimize friction losses
from the moving water. When possible, the pipeline should be buried. This stabilizes
the pipe and prevents critters from chewing it. Pipelines are usually made from PVC or
polyethylene although metal or concrete pipes can also be used. The article on hydro
system siting in Home Power #8 describes pipe sizing.
Turbines
Although traditional waterwheels of various types have been used for centuries, they
aren't usually suitable for generating electricity: They are heavy, large and turn at low
speeds. They require complex gearing to reach speeds to run an electric generator.
They also have icing problems in cold climates. Water turbines rotate at higher speeds,
are lighter and more compact. Turbines are more appropriate for electricity generation
and are usually more efficient.
There are two basic kinds of turbines: impulse and reaction.
Impulse machines use a nozzle at the end of the pipeline that converts the water
under pressure into a fast moving jet. This jet is then directed at the turbine wheel
(also called the runner), which is designed to convert as much of the jet's kinetic
energy as possible into shaft power. Common impulse turbines are pelton, turgo and
cross-flow.
In reaction turbines the energy of the water is converted from pressure to velocity
within the guide vanes and the turbine wheel itself. Some lawn sprinklers are reaction
turbines. They spin themselves around as a reaction to the action of the water
squirting from the nozzles in the arms of the rotor. Examples of reaction turbines are
propeller and Francis turbines.
Turbine Applications
In the family of impulse machines, the pelton is used for the lowest flows and highest
heads. The cross-flow is used where flows are highest and heads are lowest. The
turgo is used for intermediate conditions. Propeller (reaction) turbines can operate on
as little as two feet of head. A turgo requires at least four feet and a pelton needs at
least ten feet. These are only rough guidelines with overlap in applications.
The cross-flow (impulse) turbine is the only machine that readily lends itself to user
construction. They can be made in modular widths and variable nozzles can be used.
Most developed sites now use impulse turbines. These turbines are very simple and
relatively cheap. As the stream flow varies, water flow to the turbine can be easily
controlled by changing nozzle sizes or by using adjustable nozzles. In contrast, most
small reaction turbines cannot be adjusted to accommodate variable water flow. Those
that are adjustable are very expensive because of the movable guide vanes and
blades they require. If sufficient water is not available for lull operation of a reaction
machine, performance suffers greatly.
An advantage of reaction machines is that they can use the full head available at a
site. An impulse turbine must be mounted above the tailwater level and the effective
head is measured down to the nozzle level. For the reaction turbine, the full available
head is measured between the two water levels while the turbine can be mounted
well above the level of the exiting water.
This is possible because the "draft-tube" used with the machine recovers some of the
pressure head after the water exits the turbine. This cone-shaped tube converts the
velocity of the flowing water into pressure as it is decelerated by the draft tube's
increasing cross section. This creates suction on the underside of the runner.
There are more micro hydro components discussed on the next page.
< Micro Hydro Part 1 Micro Hydro Components Con't >
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Alternative-Heating-Info.com
Micro Hydro: Part III System Components
An intake collects the water
and a pipeline delivers it to the
turbine. The turbine converts
the water's energy into
mechanical shaft power. The
turbine drives the generator
which converts shaft power into
electricity.
In an AC system, this power
goes directly to the loads. In a
battery-based system, the
power is stored in batteries,
which feed the loads as needed.
Controllers may be required to
regulate the system.
and a pipeline delivers it to the
turbine. The turbine converts
the water's energy into
mechanical shaft power. The
turbine drives the generator
which converts shaft power into
electricity.
In an AC system, this power
goes directly to the loads. In a
battery-based system, the
power is stored in batteries,
which feed the loads as needed.
Controllers may be required to
regulate the system.