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| Titel |
Hydropower production from bridges in urban or suburban areas |
| VerfasserIn |
Tullio Tucciarelli, Vincenzo Sammartano, Marco Sinagra, Gabriele Morreale, Teresa Ferreira |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107784
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| Publikation (Nr.) |
 EGU/EGU2015-7498.pdf |
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| Zusammenfassung |
| A new technology for hydropower production from rivers crossing urban or suburban areas is
proposed, based on the use of Cross-Flow turbines having its axis horizontal and normal to
the flow direction. A large part of the river cross-section could be covered by the turbine
cross-section and this would generate a small, but consistent jump between the water levels of
the inlet and the outlet sections.
The turbine should be anchored to a pre-existing bridge and the total length of its axis
should be of the same order of the bridge length. Due to the large axis extension, it should be
possible to easily attain a gross power similar to the power produced with a more traditional
installation, based on weirs or barrages, if single jumps of few tens of centimeters were added
over a large number of bridges. If the bridges were set in urbanized areas, the production of
electricity would be located close to its consumption, according to the smart grid
requirements, and the hydrological basin at the bridge section (along with the corresponding
discharge) would be greater than the basin of traditional plants located in more upstream
locations.
The maximum water level to be attained in the upstream section of the bridge should be
the minimum among the following ones: 1) the level corresponding to the maximum
flood allowed by the surrounding infra-structures, 2) the level corresponding to the
maximum force allowed by the bridge structures. The resulting upstream water
level hydrographs should be compatible with the river suspended and bed load
equilibrium and with the requirement of the aquatic living population. The system should
include a mechanism able to raise the turbine completely out of the water level, if
required, for maintenance or other purposes. The complete lifting of the turbine could
be used to: a) reconstruct the natural river bed profile during floods, b) allow the
navigation or fish movements during some periods of the year, or even some hours of the
day.
A possible technology which would allow the accomplishment of the proposed
targets is the use of a Cross-Flow turbine, arranged according to the scheme of Fig.1,
where:
- the position of the rotating wall (rw) is set according to the pressure measured at its top,
so that a small but constant falling discharge (Q2) is guaranteed. This falling discharge allows
the transition of floating objects and hid the all machinery, with an obvious skyline
improvement.
- the average distance d is set in order to guarantee in the confined channel
below the turbine an average velocity V similar to the original one existing in the
river.
PIC
Fig.1 - Scheme of the river Cross-Flow turbine.
Observe in Fig.2 the results of a CFX simulation, carried on with the following input data
for a large rectangular section per unit width:
ho (m) h1(m) h2 (m) d(m)
1.5314 1.99 0.082 0.1021
  Â
Q2(m2/s) Q3(m2/s)w (r.p.m.)V0(m/s)
0.04 0.267 27 2.61
Table 1. Input data for the CFD simulation.
Simulation have been carried out using ANSYS code, with a computational domain
divided using both tetrahedral and prismatic elements.
The mechanical power estimated at the rotational shaft was of 4.84 KW/m and the
hydraulic power of the water stream was of 7.25 KW/m. Thus the turbine efficiency was of
about 49.97 %.
PIC
Fig.2 - Vectors velocity water field close to the Cross-Flow turbine domain.
From the environmental point of view the turbine constitutes nonetheless a physical
barrier that moving organisms will have to negotiate on their movements through the
blades, particularly larger ones such as fish. Also, the hydraulic environment of the
river will be modified, e.g. turbulence, shear stress, pressure and flow patterns,
affecting as well the smaller organisms. While developing the turbine, a thorough
appraisal of its environmental consequences for aquatic ecosystems has to be done,
in order to develop an environmentally-friendly structure, embedding mitigation
aspects.
Furthermore, the structure itself will be subject to colonization on its surfaces by a
biological matrix including microbial organisms but also filamentous algae and aquatic
macrophytes, either anchored of clogging to the structure while drifting downstream. When
developing the turbine, the side-effects of such epibiosis have to be evaluated, given the
evidence already existing in rivers and canals, of harmful vegetation interfering with
irrigation and transport structures. |
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