At the highly traditional Neumühle in the community of Argenbühel in Germany’s western Allgäu region, the power of water has been harnessed on the Untere Argen river for centuries.

At the end of the 19th century, the site was electrified by the founders of the Argen works and in 1918 it was equipped with a Francis machine unit. During the course of the 1970s, the operators at the time sold the hydroelectric power plant to the Winter miller family, whose son Hubert Winter then decided to fundamentally modernise the Neumühle power plant, which was showing its age. The new plant concept envisages the installation of pipes for the lower part of the works water channel; the biggest GRP spiral pipes from the Flowtite system with the dimension DN3000 produced by the company AMITECH in Germany were used here.

The most striking aspect about the comprehensive renovation of the Neumühle
plant is the relocation of the
power production unit from the old mill site
to a new powerhouse 50 metres further down
the channel, right by the mouth feeding into
the Untere Argen river. The old drainage channel, which is approx. 350 metres long, is
still used as far as the old mill, but from there
the works water will in future be guided via a
siphon line with a subsequent suction pipe
into the newly laid GRP pipe string with a
diameter of 3.0 metres, which is then guided
directly into the new turbine house.
RAPID LAYING OF THE GRP PIPES THANKS TO
INNOVATIVE CONNECTOR SYSTEM
When in mid-March 2013 the AMITECH
FLOWTITE pipes DN3000 for the new
works water pipeline and DN2000 for the
necessary undersluice channel are delivered,
the construction company Ebert has already
perfectly prepared the channel excavation
below the old power plant site together with
the rough and fine levelling. Under the
watchful eyes of AMITECH project manager
Jochen Auer and construction site engineer
Uwe Pletz, the 6-metre-long sections of pipe
made from glass-fibre-reinforced polyester
resin are lifted by crane into the construction
pit and moved into position there. The construction
company has specially produced a
steel cross which matches the diameters of the
pipes and is attached to the coupling of the
GRP pipe which is to be laid. A digger then
uses its scoop to press against the attached
steel cross and pushes the new section of pipe
into the coupling of the existing pipe string
which has been well greased beforehand. The
AMITECH connector system of the patented FLOWTITE series with an interlocking seal
produces a specific noise when the sections of
pipe are locked together: “When it clicks, it
fits,” says Jochen Auer in describing the audible
sign of success when joining the pipes
together with a wink, “with this system we are
able to lay up to over 100 metres a day when
the conditions on the construction site are in
our favour.”
HYDRAULIC PIPE PROPERTIES PERSUADE
THE OPERATOR
In addition to its sealing function, another
advantage of the connector system is also a
certain flexibility when laying the FLOWTITE
GRP pipes. The pipe is moved straight
into the coupling and it can then be adjusted
slightly so that it is possible to work flexibly
in a certain range, but not beyond the sealing
element. In total, 48 metres of DN3000
pipes of the pressure class PN6 for the works
water and 61 metres of DN2000 pipes for the
undersluice channel of the new power plant
are being laid at the Neumühle site. The
developer Hubert Winter is also very satisfied
with the GRP pipe strings from the company
Amitech: “With the relocation of the powerhouse
further down the channel and the
hydraulically perfect properties of the AMITECH
FLOWTITE pipes, we have now gained
a total of approx. 70 cm of net drop for
generating power at the new site.” With a
current total gradient of around 7 metres, the
boost in power gained from the new plant
concept is therefore around 40 kW.
EFFICIENTLY DESIGNED KAPLAN TURBINE
DELIVERS NOTABLE BOOST IN
PERFORMANCE
And in order now to also make efficient use
of the optimised drop in gradient in the new
powerhouse in energy terms, Hubert Winter
decided to install a double-regulated Kaplan
turbine from the company HSI Hydro
Engineering there. This 5-vane turbine with a
vertical axis and an impeller diameter of 1.50 metres will by the end of 2013 replace the
almost 100-year-old Francis machine unit
from the old mill site and, together with an
equally new residual water turbine at the
restored discharge weir, now supply twice the
annual working capacity to the grid.
Incidentally, at the weir a water volume of up
to 10.5 m3/s can be drawn into the discharge
of the works water channel, but with the
design of the Kaplan turbine the main attention
was paid to the throughflows of between
4 and 8 m3/s as in this range, with an opening
of approx. 45 – 80%, the turbine can be
operated in the best efficiency range of
around 90%. Coupled directly to the turbine
shaft, a permanent magnet generator will
turn the mechanical work into electrical energy.
The PM generator, which is smaller and
lighter compared with conventional units,
also offers a persuasive choice with high efficiency
in the partial load range.
NEW TYPE OF FISHWAY UNDER
DISCUSSION
As part of the restoration work, a series of
measures to support the ecology of the waterways
will also be implemented, for example a
specially laid lock flow bypass which, competing
with the turbine outflow from the new
powerhouse, is intended to point the fish
fauna in the Untere Argen river in the right
direction towards the discharge channel in
the direction of the weir. And if the power
plant operator Hubert Winter gets his way, a
new and innovative type of migration aid
should soon enable the fish at the weir to
climb up into the headwater. This is because,
in addition to the conventional solutions,
consideration is also being given to a newly
developed fish lift which in a vertical
DN3000 GRP pipe is intended to transport
the aquatic water fauna into the headwater by
means of a floating acrylic glass basket.
Developer Hubert Winter is still coy about
revealing too many details of this pioneering
idea, but the advantages of rapid and straightforward
transportation of the fish to the
headwater with drops of up to 30 metres and
more, coupled with a design which saves
space and costs and has comparatively low
operational throughflows, seem to be hard to
deny.
The operator would like to be connected to
the grid with his fully renovated plant by the
end of this year. Together with his Thalerschachen
hydroelectric power plant, which is
also situated in Argenbühel, Hubert Winter
will thus be generating a considerable proportion
of the power required by this Allgäu
community.
The steel cross made
especially for the laying
process is used by a
digger to press against
the pipe sections.