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The Replanting of Lochaber Hydro Power Station

by Andrew Thick

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Topics to be covered today

• Scheme modelling;

• Operating capability of Lochaber;

• Turbine selection;

• Penstock works.

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Spey Dam

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Laggan Dam

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

10

Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Loch Treig and Dam

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Schematic of the Lochaber Scheme

Loch Laggan & reservoir

Loch Treig

SpillSpill

Gravity Inflows

Gravity Inflows

Power-house

Tailrace

Spill

Surge Chamber

LochLinnhe

Spey reservoir

Penstocks

tunneltunnel

tunnel

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Penstocks, Powerhouse and Smelter

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Simplified Lochaber Scheme Model

QTspill

QP/H

QTin

Laggan

QTin

QTunnel

Treig

QLspill

QLin

QLin

QLin

Qintakes

Qintakes

Gravity Intake Flows are combined with Reservoir Inflows

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Energy Modelling Results

Trial 1 2 3 4 5 6 7

Installed Cap. (MW) 65 80 60 70 80 90 100

Overall Efficiency (%) 75 87 87 87 87 87 87

Headloss Coeff. (k) 0.021 0.0172 0.0172 0.0172 0.0172 0.0172 0.0172

Operating rule Ext Ext Max E Max E Max E Max E Max E

Laggan Spill (mcm) 2,034 1,794 4,160 1,709 1,227 1,074 801

Treig Spill (mcm) 154 121 857 201 54 10 7

Ave. Energy (GWh/yr) 467 569 523 574 581 583 580

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Scheme Operating Capability Diagram

9.3 % Q90.7 % Q

Average Operation

0 % Q100 % Q

No Gravity Inflows

100 % Q0 % Q

Max. Gravity Inflows

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Operating Capability in terms of Loch Treig Level

Note: 90.7% of water from Loch Treig9.3% of water from gravity intakes

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Scheme Operating Capability Diagram

9.3 % Q90.7 % Q

Average Operation

0 % Q100 % Q

No Gravity Inflows

100 % Q0 % Q

Max. Gravity Inflows

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Operating Capability in terms of Surge Shaft Water Level

Penstock Limitation

Note: 90.7% of water from Loch Treig9.3% of water from gravity intakes

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Scheme Operating Capability Diagram

9.3 % Q90.7 % Q

Average Operation

0 % Q100 % Q

No Gravity Inflows

100 % Q0 % Q

Max. Gravity Inflows

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Note: All water from Loch Treig

Operating Capability in terms of Surge Shaft Water Level

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Scheme Operating Capability Diagram

9.3 % Q90.7 % Q

Average Operation

0 % Q100 % Q

No Gravity Inflows

100 % Q0 % Q

Max. Gravity Inflows

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Operating Capability in terms of Surge Shaft Water Level

Note: All water from gravity intakes

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Scheme Operating Capability Diagram

9.3 % Q90.7 % Q

Average Operation

0 % Q100 % Q

No Gravity Inflows

100 % Q0 % Q

Max. Gravity Inflows

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Example Operation exceeding Penstock Pressure Rise Limit

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Turbine Selection

The steps towards to turbine selection were:

• Analysis of historical data of scheme operation

• The number of generating units was selected – 5

• Analysis of operating data from scheme model

• Performance data from tendering suppliers was fed into the scheme model

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Scheme Operation Frequency Plot

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Turbine Selection

The steps towards to turbine selection were:

• Analysis of historical data of scheme operation

• The number of generating units was selected – 5

• Analysis of operating data from scheme model

• Performance data from tendering suppliers was fed into the scheme model

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Turbine Selection

The steps towards to turbine selection were:

• Analysis of historical data of scheme operation

• The number of generating units was selected – 5

• Analysis of operating data from scheme model

• Performance data from tendering suppliers was fed into the scheme model

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Turbine Selection

The steps towards to turbine selection were:

• Analysis of historical data of scheme operation

• The number of generating units was selected – 5

• Analysis of operating data from scheme model

• Performance data from tendering suppliers was fed into the scheme model

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Penstock works

Key aspects of the penstock works were:

• Need to undertake the works minimising shutdown of generation.

• Existing penstock system was very complex.

• In order to maintain double isolation, the penstocks needed to be dewatered sequentially.

• The works were complex with poor access.

• Decision with RTA to laser scan the penstock system and create a 3-D model.

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Multiple buspipes

Numerous Valves

Bifurcations

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Penstock Area – difficult terrain!

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Penstock works

Key aspects of the penstock works were:

• Need to undertake the works minimising shutdown of generation.

• Existing penstock system was very complex.

• In order to maintain double isolation for the penstocks needed to be dewatered sequentially.

• The works were complex with poor access.

• Decision with RTA to laser scan the penstock system and create a 3-D model.

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Survey Point Cloud Data

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AutoCAD 3-D Model

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Project Summary

• The generating plant has been replaced to give 25+ years life extension.

• The water to wire efficiency has been improved from 75% to 90+%.

• Energy production increased from 460 GWh/yr to 600+ GWh/yr.

• The scheme’s capability is better understood and limitations identified.

• The scheme was completed ahead of schedule and is operating successfully with minimal disruption to Smelter operations during construction

Contact Details

Andrew Thick BEng CEng MIMechE

URS Infrastructure and Environment UK Limited

International House, Dover Place

Ashford

Kent TN23 1HU

United Kingdom

Tel: +44 (0) 1233 658200

hydropower@urs.com

Thank you for your kind attention