How to Recognize Quality and Durability
As we’ve shown, a hydro system is both
simple and complex. The concepts behind water power are
simple: it all comes down to Head and Flow. But good
design requires advanced engineering skills, and reliable
operation requires careful construction with quality components.
Think of a turbine system in terms of
efficiency and reliability. In a perfect world, efficiency
would be 100%. All the energy within the water would be
transformed to the rotating shaft. There would be no air
or water turbulence, and no resistance from bearings. The
runner would be perfectly balanced. The signs of energy
loss – heat, vibration and noise – would be absent. Of
course, the perfect turbine would also never break down or
Quality components and careful machining make a big difference
in turbine efficiency and reliability.
Obviously no turbine system will ever
achieve this degree of perfection. But it’s good to keep
these goals in mind, because better efficiency and reliability
translate to more power and a lower cost-per-watt. Here
are just a few of the things to consider when selecting a
The runner is the heart of the turbine.
This is where water power is transformed into the rotational
force that drives the generator. Regardless of the runner
type, its buckets or blades are responsible for capturing the
most possible energy from the water. The curvature of each
surface, front and rear, determines how the water will push its
way around until it falls away. Also keep in mind that any
given runner will perform most efficiently at a specific Head
and Flow. The runner should be closely matched to your site
Look for all-metal runners with smooth,
polished surfaces to eliminate water and air turbulence.
One-piece, carefully machined runners typically run more
efficiently and reliably than those that are bolted together.
Bronze manganese runners work well for small systems with clean
water and Heads up to about 500 feet. High-tensile stainless
steel runners are excellent for larger systems or abrasive water
conditions. All runners should be carefully balanced to
minimize vibration, a problem that not only affects efficiency
but can also cause damage over time.
The turbine housing must be well built and
sturdy, as it manages forces of the incoming water as well as
the outgoing shaft power. In addition, its shape and
dimensions have a significant affect on efficiency. For
example, consider a Pelton-type turbine. As an impulse
turbine, it is driven by one or more jets of water, but spins in
air. This means that both hydrodynamic and aerodynamic
forces must be considered in the design of the housing. It
must minimize the resistance from splash and spray and smoothly
exhaust tail waters, yet also be sized and shaped properly to
minimize losses due to air turbulence. Similarly, housings
for high-Flow designs like Crossflow and Francis turbines must
be precisely engineered to smoothly channel large volumes of
water through the turbine without causing pockets of turbulence.
Look for a smoothly welded housing that is
carefully matched to the proper runner for your site. Keep
in mind that both the water forces and the runner will be
producing considerable torque, so the housing material and all
fittings should be heavy-duty. Mating surfaces, such
as pipe flanges and access covers, should be machined flat and
leak-free. Since water promotes rust and corrosion, make
sure all vulnerable surfaces are protected with high quality
powder coat or epoxy paint. All bolts should be stainless
All surfaces that carry water can impact
efficiency, from the intake to your pipeline to the raceway that
carries the tail waters away from your powerhouse. Look
for smooth surfaces with no sharp bends, Jets and flow control
vanes should be finely machined with no discernable ripples or
Efficiency is important, but so are
durability and dependability. Your hydroelectric project
should deliver clean power without interruption. The
quality of components – and their installation – can make a big
difference on the quality of your life in the years to come.
Look for meticulous workmanship in the
design and construction of seal systems, shaft material and
machining, and all related components. Pay particular
attention to the selection and mounting of bearings; they should
spin smoothly, without grating or binding.
When it comes to suppliers, there is no
substitute for experience. While the principles of hydro
power can be mastered indoors, it is real world experience that
teaches both the highlights and pitfalls of diverting water from
a stream, pressurizing it, and forcing it through a turbine.
A turbine supplier with many years of field experience will be
invaluable to you as your design and build your hydro system.
Look for an experienced supplier that
specializes in the size and type of hydro system you intend to
build. A good supplier will work with you, beginning
with your measurements of Head and Flow, to help you determine
the right pipeline size, Net Head, Design Flow, turbine
specifications, drive system, generator, and load management
system. You should be able to count on your supplier to
make suggestions for optimizing efficiency and dependability,
including their effects on cost vs. performance.
A good turbine supplier is your partner,
and should take a personal interest in your success. After
all, a satisfied customer is very good for business.
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