Thursday, October 21, 2010

Shaft hydropower – small is beautiful, and good for environment

Shaft power plant design � small is beautiful, and good for the

Invention enables hydroelectric power generation at thousands of
unused locations

20.10.2010, Press releases

Hydroelectric power is the oldest and the �greenest" source of
renewable energy. In Germany, the potential would appear to be
completely exploited, while large-scale projects in developing
countries are eliciting strong criticism due to their major impact on
the environment. Researchers at Technische Universitaet Muenchen (TUM)
have developed a small-scale hydroelectric power plant that solves a
number of problems at the same time: The construction is so simple,
and thereby cost-efficient, that the power generation system is
capable of operating profitably in connection with even modest dam
heights. Moreover, the system is concealed in a shaft, minimizing the
impact on the landscape and waterways. There are thousands of
locations in Europe where such power plants would be viable, in
addition to regions throughout the world where hydroelectric power
remains an untapped resource.

In Germany, hydroelectric power accounts for some three percent of the
electricity consumed � a long-standing figure that was not expected to
change in any significant way. After all, the good locations for
hydroelectric power plants have long since been developed. In a number
of newly industrialized nations, huge dams are being discussed that
would flood settled landscapes and destroy ecosystems. In many
underdeveloped countries, the funds and engineering know-how that
would be necessary to bring hydroelectric power on line are not

Smaller power stations entail considerable financial input and are
also not without negative environmental impact. Until now, the use of
hydroelectric power in connection with a relatively low dam height
meant that part of the water had to be guided past the dam by way of a
so-called bay-type power plant � a design with inherent disadvantages:

* The large size of the plant, which includes concrete
construction for the diversion of water and a power house, involves
high construction costs and destruction of natural riverside landscapes.

* Each plant is a custom-designed, one-off project. In order to
achieve the optimal flow conditions at the power plant, the
construction must be planned individually according to the dam height
and the surrounding topography. How can an even flow of water to the
turbines be achieved? How will the water be guided away from the
turbines in its further course?

* Fish-passage facilities need to be provided to help fish bypass
the power station. In many instances, their downstream passage does
not succeed as the current forces them in the direction of the power
plant. Larger fish are pressed against the rakes protecting the intake
of the power plant, while smaller fish can be injured by the turbine.

A solution to all of these problems has now been demonstrated, in the
small-scale hydroelectric power plant developed as a model by a team
headed by Prof. Peter Rutschmann and Dipl.-Ing. Albert Sepp at the
Oskar von Miller-Institut, the TUM research institution for hydraulic
and water resources engineering. Their approach incurs very little
impact on the landscape. Only a small transformer station is visible
on the banks of the river. In place of a large power station building
on the riverside, a shaft dug into the riverbed in front of the dam
conceals most of the power generation system. The water flows into a
box-shaped construction, drives the turbine, and is guided back into
the river underneath the dam. This solution has become practical due
to the fact that several manufacturers have developed generators that
are capable of underwater operation � thereby dispensing with the need
for a riverbank power house.

The TUM researchers still had additional problems to solve: how to
prevent undesirable vortex formation where water suddenly flows
downward; and how to best protect the fish. Rutschmann and Sepp solved
two problems with a single solution � by providing a gate in the dam
above the power plant shaft. In this way, enough water flows through
to enable fish to pass. At the same time, the flow inhibits vortex
formation that would reduce the plant's efficiency and increase wear
and tear on the turbine.

The core of the concept is not optimizing efficiency, however, but
optimizing cost: Standardized pre-fabricated modules should make it
possible to order a �power plant kit" just like ordering from a
catalog. �We assume that the costs are between 30 and 50 percent lower
by comparison with a bay-type hydropower plant," Peter Rutschmann
says. The shaft power plant is capable of operating economically given
a low "head" of water of only one to two meters, while a bay-type
power plant requires at least twice this head of water. Series
production could offer an additional advantage: In the case of wider
bodies of water, several shafts could be dug next to each other � also
at different points in time, as determined by demand and available

Investors can now consider locations for the utilization of hydropower
that had hardly been interesting before. This potential has gained
special significance in light of the EU Water Framework Directive. The
directive stipulates that fish obstacles are to be removed even in
smaller rivers. In Bavaria alone, there are several thousand existing
transverse structures, such as weirs, that will have to be converted,
many of which also meet the prerequisites for shaft power plants.
Construction of thousands of fish ladders would not only cost billions
but would also load the atmosphere with tons of climate-altering
greenhouse gas emissions. If in the process shaft power plants with
fish gates and additional upstream fish ladders were installed,
investors could shoulder the costs and ensure the generation of
climate-friendly energy over the long term � providing enough power
for smaller communities from small, neighborhood hydroelectric plants.

Shaft power plants could also play a significant role in developing
countries. �Major portions of the world�s population have no access to
electricity at all," Rutschmann notes. �Distributed, local power
generation by lower-cost, easy-to-operate, low-maintenance power
plants is the only solution. For cases in which turbines are not
financially feasible, Rutschmann has already come up with an
alternative: �It would be possible to use a cheap submersible pump and
run it in reverse � something that also works in our power plant."


Prof. Peter Rutschmann

Technische Universitaet Muenchen

Department of Hydraulic and Water Resources Engineering

Tel.: +49 89 289 23161

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