development of criteria for the design and...

DEVELOPMENT OF CRITERIA FOR THE DESIGN AND DIMENSIONING OF FISH-FRIENDLY INTAKES FOR SMALL

HYDROPOWER PLANTS

RICHARD S.(1), COURRET D.(1), LARINIER M (3)., DAVID L.(2), CHATELLIER L.(2)

(1) Ecohydraulic team ONEMA-IMFT, Toulouse (FR)(2) P’ institute, Poitiers (FR)(3) Dr. Ing. Ecohydraulic expert

Workshop 1Screening & bypasses / fish guidance techniques / maintenance for HPP < 50 m3/s

Roermond (NL), 6-7 october 2016

CONTEXT IN FRANCE

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• Downstream migration is taking into account for :

Salmon & sea trout smolts(+ adults)è can have lot of hydropowerplants on their migration route

Silver eelè suffering high mortalities (large size, lot of hydropower plants on their migration route)

Brown trout (fry, juvenile, adult)è substantial or high mortalities at medium or high head hydropowerplants

Less problematic for other speciesè small individuals by speciesè or less hydropower plants on their migration route

(downstream migration over short distances)è research and knowledge deepen

CONTEXT IN FRANCE

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• A few big plants

• A lot of hydropower plants on migration route (old mills)o Turbine disharge mostly < 50 m3/s, some between 50-100 m3/s

o Run-of-river operation

o Dordogne and Garonne rivers : 300-500 m3/s

o Rhine and Rhone rivers : 1000-1500 m3/s

Saint Thibéry on Hérault river Tourouzelle on Aude river

Vallabrègues on Rhone river

Marckolsheim on Rhine river

© MRM

© Richard

© Richard

© Richard

BRIEF OVERVIEW OF SOLUTIONS AND ONEMA POSITION

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4 main types of solutions

• Fish friendly turbine (VLH, screw) è Good solutions, but limited to low heigh dam and discharge, mostly for new equipment, not really cost-effective on existing plant

• Behavorial device (sound, light, electricity) è No system approved until now, except light to attract smolts near bypasses

• Targeted shutdown of turbines è Foreseen for eels at biggest dams where othersolutions are not feasible, but difficult to define, ongoing research

• Materials barriers wich can induced both behavorial or physical effect :o Louver è Not implemented due to maintenance constraints

o Surface guiding wall with bypass è Reserved to biggest dams (1 case in France)

o Bypass in association with trashrack è main solution implemented at smallplants in France

STUDIES CONDUCTED

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• 1992 – 2005 : assessment of the efficiency of bypasses in association with existingtrashracks (EDF R&D, CSP, CEMAGREF)

è A satisfactory solution in some cases

è But difficulties to obtain regularly good efficiencies, especially for eels

Halsou, Nive

Baigts, Gave de Pau

Bypass efficiency for smolts :

Bypass efficiency for eels :- Baigts : ≈ 20% (surface), very low (bottom)

- Halsou : 56-64%

© Larinier

© Larinier

STUDIES CONDUCTED

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• 2007 – 2008 : synthetize the feed-back of all efficiency assessment and intake design in France and abroad (mainly USA) to define criteriafor systems of racks and bypasses with high efficiency (> 90%)è So-called « fish friendly intakes »

è Production of a technical guide in 2008

• 2010 – until now : hydraulic studies, mainly on down-scale physical model + numericalsimulationè Cararcterize head-losses through racks in fish-friendly configuration

è Verification of guiding conditions and adaptation of criteria

è Precise criteria for the design of bypasses(attractivity in function of position, flow…)

angled trashrack

© Courret

3 FUNDAMENTALS FUNCTIONS

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1) Stop fish and avoid their passage through turbine

• Smolts :– Possible to obtain good efficiency with

a behaviour effect

è Bar spacing ≤ 25 mm

• Silver eels :– Necessity to install a physical barrier : bar

spacing ≤ head diameter

è Bar spacing = 15 - 20 mm to stop eels longersthan 50 – 60 cm

• Velocities upstream the rack low enough to :– Allow fish swimming during time necessary to find bypasses

– Do not induce rapid passage through or impingement of fish against rack

è Normal velocity (flow divided by the wetted rack surface) ≤ 0.5 m/s for eels and smoltsè Give a minimal surface of the rack for a given turbine discharge : at least 2 m2

of rack for 1 m3/s of turbine discharge

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Figure 6 : Courbe classée des valeurs des rapports (largeur de tête / longueur du corps) à partir des 579 anguilles argentées utilisées dans le cadre des expérimentations menées sur le Gave de Pau.

L’espacement libre maximal à adopter sera fonction des caractéristiques de la population d’anguilles en amont de l’aménagement (taille des individus dévalant, sex ratio). Constituer une barrière physique pour les plus petits individus dévalant (petits males de 30-40 cm) nécessite d’avoirrecours à un espacement de l’ordre de 1.0 cm. Il apparaît toutefois qu’une grille avec un espacement libre de 1.5 cm constitue déjà une barrière physique pour la moitié des anguilles mesurant entre 40 et 50 cm et pour pratiquement tous les individus de plus de 50 cm. De même, une grille avec un espacement libre de 2.0 cm constitue une barrière physique pour plus d’un quart des anguilles mesurant entre 50 et 60 cm et pour tous les individus de plus de 60 cm (Figure 7).

Figure 7 : Boites de dispersion18 des largeurs de tête d’anguille par classe de taille (échantillon des 579 anguilles argentées utilisées dans le cadre des expérimentations menées sur le Gave de Pau).

Les plus petites anguilles (généralement des mâles) subissant des mortalités moindres au passage par les turbines que les gros individus, on peut envisager une protection incomplète de cette frange de la population et ainsi préconiser d’adopter pour les anguilles un espacement libre maximal entre les barreaux de l’ordre de 1.5 – 2.0 cm. Avec de tels espacements, on peut tout de même espérer une certaine efficacité sur les petites anguilles en comptant sur un certain effet comportemental répulsif du plan de grille.

Les préconisations sur l’espacement libre maximal entre les barreaux sont susceptibles de s’affiner au regard des résultats des expérimentations futures, en particulier pour l’anguille.

18 Les boites de dispersion présentent la moyenne des valeurs (point bleu), la médiane (trait au sein de la boite jaune), le premier et le troisième quartile (extrémités de la boite) et l’étendue des données (minimum et maximum aux extrémités de la droite bleu).

length of the eels (cm)

wid

thof

hea

d(m

m)

Courret et Larinier 2008

© Aigoui

Measured velocities (side view) (Raynal et al. 2012) X (mm)

Z (m

m)


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2) Guide fish towards bypassesè inclined trashrack perpendicular to the flow

• Moderate acceleration of velocities along the rack (≈ +10% at the top of the rack)

• To guide fish to the surfaceè minimal inclination at ß ≤ 26° to obtain Vtangential ≥ 2 Vnormal

ß = 25°

Normalized velocity

Normal and tangential velocity along the rack – ß = 25°(normalized to the approach velocity)

• Approach velocity acceptable up to ≈ 0.80-0.85 m/s for ß = 26°è higher inclination in case of higher velocities

VA

VN VT

© Richard


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2) Guide fish towards bypassesè angled vertical trashrack

• Minimal angle α ≤ 45° to obtain Vtangential ≥ Vnormal

• Approach velocity acceptable limite to 0.5 m/s at α = 45°è low gain on acceptable approachvelocity with increase of the angulation

Raynal et al. 2014

Conventionnal rack (bar perpendicular to the rack axis)

• Flow acceleration along the rack (≈ 1.7 VA at α = 45°) and head-losses increasing with angulation

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Figure 59 : Champs de vitesse longitudinale U, vus en plan, en amont de plans de grille orientés à

30°, 45° et 60° (de haut en bas). Vitesses moyennée s dans le temps, rapportées à la vitesse débitante V1. Profil hydrodynamique. e = 20/40 mm. Wang et al. (2010) et Chatellier et al. (2011).

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Figure 59 : Champs de vitesse longitudinale U, vus en plan, en amont de plans de grille orientés à

30°, 45° et 60° (de haut en bas). Vitesses moyennée s dans le temps, rapportées à la vitesse débitante V1. Profil hydrodynamique. e = 20/40 mm. Wang et al. (2010) et Chatellier et al. (2011).

X (mm)

Measured velocities (plane view) ; α = 45°

Raynal et al. 2012

conventional rack

© Courret


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2) Guide fish towards bypassesè angled vertical trashrack

• Minimal angle α ≤ 45° to obtain Vtangential ≥ Vnormal

• Approach velocity acceptable up to 0.6 m/s at α = 45°è higher angulation in case of highervelocities, but solution to find to clean the rack

Rack with streamwise bars (experimental configuration)

Raynal et al. 2014

• Homogeneous velocities upstream the rack and reductionof head-losses

Measured velocities (plane view) ; α = 45°

α = 45°

rack with streamwise bars

Raynal et al. 2014


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2) Guide fish towards bypasses è angled vertical trashrack

• Angled rack with horizontal bars are interesting

- No installation in France ; severalinstallations in Germany and Sweden

- Looking for studies and feedback on this configuration

• Rack in bank alignment are favorable configuration for fish guidance rack

bypass

Baigts on Gave de Pau river

Clugh 2011

© Geoportail


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3) Downstream transfer of fish è inclined rack

• Criteria to determine bypass number and flow- Minimal dimensions recommended : 1 m wide (Bb) and 0.5 m deep (Hb)

- Maximal distance between bypasses : 4-5 m è determination of the number of bypasses Nb

- Velocity at the bypass entrance Vbypass = 1.1 Vapproach

- Obstruction of the top of the rack, between bypasses, over the same depth è to generate transversal velocities

• Surface bypasses at the top of the rack

è Qb = Vb x Hb x (Nb x Bb)è From 5-6% of turbine discharge for small intakes, down to 2-3% for intakes > 50 m3/s

Near surface velocities (plan view) at the top of inclined rack ; β= 26° Raynal et al. 2013

3 bypasses1 bypass 2 bypasses

© Courret


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3) Downstream transfer of fish è angled rack

• Not a complete set of criteria nowadays- Surface bypass as deep as possible, ideally same depth as the intake è high flow ;

difficulties to create a such deep bypass on existing site

- Interrogation about bottom bypass, notably for eels

Ø sensible to clothing and difficult to clean

Ø Necessity ? è eels seem to prospect all the water column if they are stoppedby the rack

- Velocity at the bypass entrance Vb of about velocities at the downstream end of the rack

Ø Vb = 1.7 VA for a « conventional » angled rack at 45° è high flow

Ø Vb = 1.0 VA for an angled rack with streamwise bars

Ø Criteria for an angled rack horizontal bars and rack in bank alignment ?

• Bypasses positioned at the downstream end of the rack

© Voegtle

HEAD-LOSSES AND CLOGGING ISSUES

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• Experimental measurement of head-losses• Existing formulae not adapted to fish-friendly

configurationsè production of new formulae (Raynal et al. 2013)

Decreasing head-losses with inclination Increasing head-losses with angulation

© Voegtle

CONCLUSIONS

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• Preference for inclined rack- Lower head-losses

- Compatible with high approach velocities

- Existing solutions for rack cleaning è except for deep intakes and long racks

- Bypass design criteria well-defines

- But not adapted to forebay with water level fluctuations

• Angled rack reserved to deep intakes, or intakes with fluctuating water levels, or in bank alignment

- « Conventionnal » rack constraining (head-losses, admissible approach velocity)

- Rack with stream-wise bars è interesting solution, trashrake design to find

- Rack with horizontal bars ? è feed-back in Deutshland and Sweden

- Design criteria for bypass to complete

• Absolute necessity to adapt the trashrake

CONCLUSIONS

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• Feed back to acquire on operation and biological efficiency

è Studies planned for 2017-2019 for silver eels and smolts by Ecohydraulic team and EDF/Ecogea : assessment of 5 HPP on Ariege river

THANK YOU FOR YOUR ATTENTIONLes Religieuses (Limoux) on Aude river Las Rives (Varilhes) on Ariège river

Carabotte (Gignac) on Herault river Rochemaure on Rhône river (intake of reduce flow)

© Richard © Richard

© Richard © Richard

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