1

The Replanting of Lochaber Hydro Power Station

by Andrew Thick

E V E N T S P O N S O R S

3

Topics to be covered today

• Scheme modelling;• Operating capability of Lochaber;• Turbine Selection;• Penstock works.

4

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

5

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

6

7

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

8

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

9

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

11

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

12

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

13

14

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

15

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

16

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

17

18

Simplified Lochaber Scheme Model

QTspill

QP/H

QTin

Laggan

QTin

QTunnel

Treig

QLspillQLin

QLin

QLin

Qintakes

Qintakes

19

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

20

Scheme Operating Capability Diagram

9.3 % Q90.7 % QAverage Operation

0 % Q100 % QNo Gravity Inflows

100 % Q0 % QMax. Gravity Inflows

21

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

22

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.

23

24

25

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.

26

27

28

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 MIMechEURS Infrastructure and Environment UK LimitedInternational House, Dover PlaceAshfordKent TN23 1HUUnited KingdomTel: +44 (0) 1233 658200hydropower@urs.com

Thank you for your kind attention