Penstock Pipeline
Todtnau, Germany
Mini Hydroelectric Power Plant
The German economy is generally based
on electric power, generated by large
coal or nuclear power stations.
However, by one estimate, the amount
of electricity generated by water could
be doubled (for example, from 8% to
possibly 15% in Bavaria).
Indeed, in the small town of Todtnau in
mountains of the Black Forest, the share
of electricity produced by water power is
about 40%, due to the private enterprise
initiatives of the local Kaiser family.
They began with small projects in their
home town of Todtnau: First, with a
turbine engine with a 65kW generating
power and 110m-long penstock out of
concrete and GRP. Second, with an
80kW plant and a 360m penstock out of
steel. Third, with a 220kW plant and a
900m penstock of cast iron.
A cost-benefit analysis of these three
plants made it evident that the costs for
the inlet building and the turbine building
stay almost constant while the cost of
the penstock can vary widely.
Therefore, high attention was given to
the pipeline construction of the next
project, the “Hell Valley Power Plant.”
With a water flow of 840 l/s and 120m
difference of altitude, the facility will be
able to generate 750kW of electric power.
GRP (glass-reinforced plastic) pipes
from Owens-Corning Eternit Pipe GmbH
(OCER) were chosen after judging the
economics of the previouslyconstructed
plants and comparing the relative
advantages of the different pipe
materials and constructions.
12m pipe laying in front of the excavator
under heavy mountain conditions
In addition to its strength and corrosion
resistance, a primary reason for the
specification of GRP pipe for this project
was its relative lightness. In the nearly
impassible rough wilderness and on
narrow footpaths, transportation of the
pipes and placing them in the trench,
Profile
Diameter(s), DN
900
Pressure Class, PN
2.5, 6, 10 and 16
Stiffness Class, SN
5000 and 10,000
Length, m
3489
Application
Penstock
Location
Todtnau, Germany
Flange mounted penstock at the
turbine building on narrow trace
was greatly eased by the low weight of the GRP
material. For example, the weight of SN10,000, DN 900
GRP is 100kg/m, compared to cast iron or steel at
approximately three times as much.
The Hell Valley project was designed with a 3500m-long
penstock of 900mm diameter GRP pipe. It takes water
from a stream called “Rotbach” by the inlet building
and leads it to the 3.5km distant turbine building, with
an outlet back to the same Rotbach stream.
The trace for the penstock line was skillfully adapted to
the valley’s shape at the river line. By using varying
lengths of pipe and the flexible alignment of couplings
(two degrees of angular deflection were allowed) only
four elbow sections with thrust blocks were needed
for the entire length of the line. The pipeline also had to
cross the river three times on specially-built pipe
bridges.
The 120m drop in altitude from inlet to outlet created
pressure differences that called for different pressure
classes of pipe, ranging from PN2.5 up to PN16.
Because the outer diameters for all pressure classes of
pipe were equal, no adapters were required and all of
the pipe sections were joined with identical couplings.
Because of differing soil covers, two different stiffness
classes (SN) were needed. Also, the pipes were
protected against the sharp, rocky stones by bedding
and back filling with sand.
Water hammer in the penstock lines is prevented by
automatically controlled valves; if they should fail, the
impact would be diminished by the elasticity of the
GRP-material. (GRP pipe design allows for an additional
surge pressure of 0.4PN.)
The total project included the following pipe
components*
Pipe
(units)
PN
SN
Length
(m)
Total lengths
(m)
29
16
10,000
9
261
135
16
10,000
6
810
3
16
10,000
3
9
44
10
5,000
12
528
37
10
5,000
6
222
45
6
5,000
9
405
109
6
5,000
6
654
50
2.5
5,000
12
600
*Plus four elbow sections and four
flanged fittings.
3489
Technical conception and organization of the project
was carried out by Mr. Bernhard Kaiser; the technical
details (statics, hydraulics, bridges, thrust-blocks)
survey and supervision was designed by civil engineer
Peter Muller, Lorrach, with assistance from OCERService. The contractors were Bombardi and Unruh,
Titisee-Neustadt.
After only six months of construction time, the plant
began supplying electricity into the public network in
December, 1994. The project contributes to
environmental protection with a reduction of about
3100 tons of CO2 per year compared to a coal power
station of equal generating capacity.
Contacts:
Owens-Corning-Eternit-Rohre GmbH
Gewerbegebiet “Am Fuchsloch”
04720 Großsteinbach
Tel. 03431/481495
Fax 03431/481466
Technischer Dienst OCER
Ernst-Reuter-Platz 8
10587 Berlin
Tel. 030/3485-0
Fax 030/3485366
Kleinkraftwerke Kaiser
Freiburger Straße 35
79674 Todtnau
Tel. 07671/362
Fax 0671/8582
Ing. Büro Bauer & Partner
Tumringer Str. 287
79539 Lörrach
Tel. 07621/3781
Fax 07621/1247
THE HELL-VALLEY
Railway
Road
River
PENSTOCK on different trace
Distributed by:
FLOWTITE Technology AS
P.O. Box 2059
3202 Sandefjord
Norway
Tel.: + 47 971 003 00
Fax: + 47 334 626 17
[email protected]
www.flowtite.com
www.amiantit.com