Arno Ottermann (PULA)

Bo Barta, Willem Slabber, UJ

Retrofit of Small-scale Hydropower at

Hartbeespoort Dam

Pre-investment Investigation

Introduction

• RSA overview : Dam retrofit (green vs brown field)

• Pilot retrofit: Hartbeespoort dam - pilot

• Dev. Potential: past / current / future

• Key challenges: DWA policy (PPP)

motivate “small” opportunity

multi-faceted use

LED / hybrid

• Hydropower ~ Height x Flow

• Height ~ dam wall height / height to canal (certain!)

• Flow ~ subject to dam operating rules (uncertain!)

– daily environmental releases

– daily down-stream needs

– seasonal dam spillages

• Size and type of outlet works

– Access to outlet pipe to connect penstock (Dam safety)

– Hydraulic impact on existing outlet (incl. water hammer)

• Type of spillway (affects location of hydro-power plant)

Critical Considerations of Retrofit

• ± 4000 water dams

• 135 Large / 865 Medium / 3000 small

• 359 DWA owned (M/L)

• 70 of DWA dams have a hydro-power potential

• DWA can generate > 100MW base load (450GWh/a)

• RSA > 250MW Province

Height

<15

15-30m

30-60m

>60m

Count of

Dams

EC 379 73 28 2 482

FS 346 39 7 3 395

GT 115 13 4 1 133

KN 796 59 11 2 868

LP 238 40 16 3 297

MP 346 55 20 2 423

NC 92 9 1 102

NW 31 11 3 45

WC 941 264 42 4 1251

Total 3284 563 132 17 3996

Height: RSA dam safety register

Pilot Study: Dam Retrofit

Hartbeespoort Dam

Acknowledgements

• Study Funder:

– Dept of Economic Affairs – Gauteng

• Implementing Agent:

– The Innovation Hub Management Company

– Dr Charity Mbileni: Manager Green & Sustainable Dev.

• Public Entity / Owner:

– Dept of Water Affairs (owner & operator of dam & WR)

• Service Provider:

– PULA srm Consortium (UJ, B.Barta, W.Slabber)

PHASE-1:

NEEDS ASSESSMENT

Motivation-1: Growing Energy Shortage

Motivation-2: Removal of Sediment (1)

Motivation-2: Removal of Sediment

Motivation-3: Water Quality

Motivation-3: Water Quality (2)

Motivation-4: Social & Recreational Use

PHASE-2:

HYDROLOGICAL ANALYSIS

Hydrologic Analysis: 32yr daily flows

• Understand the hydrology!

• Base flow?

• What % of spillage?

0

5

10

15

20

25

30

35

40

45

50

19

81

/1/1

19

84

/1/9

19

87

/1/1

7

19

90

/1/2

5

19

94

/1/2

19

97

/1/1

0

20

00

/1/1

8

20

03

/1/2

6

20

07

/1/3

20

10

/1/1

1

19

81

/2/1

9

19

84

/2/2

7

19

88

/2/4

19

91

/2/1

2

19

94

/2/2

0

19

97

/2/2

8

20

01

/2/5

20

04

/2/1

3

20

07

/2/2

1

20

10

/2/2

9

19

82

/3/6

19

85

/3/1

4

19

88

/3/2

2

19

91

/3/3

0

19

95

/3/7

19

98

/3/1

5

20

01

/3/2

3

20

04

/3/3

1

20

08

/3/8

20

11

/3/1

6

19

82

/4/2

4

19

86

/4/1

19

89

/4/9

19

92

/4/1

7

19

95

/4/2

5

19

99

/4/2

20

02

/4/1

0

20

05

/4/1

8

20

08

/4/2

6

19

80

/5/3

19

83

/5/1

1

19

86

/5/1

9

19

89

/5/2

7

19

93

/5/4

19

96

/5/1

2

19

99

/5/2

0

20

02

/5/2

8

20

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/5/5

20

09

/5/1

3

19

80

/6/2

1

19

83

/6/2

9

19

87

/6/6

19

90

/6/1

4

19

93

/6/2

2

19

96

/6/3

0

20

00

/6/7

20

03

/6/1

5

20

06

/6/2

3

20

09

/6/3

1

19

81

/7/8

19

84

/7/1

6

19

87

/7/2

4

19

91

/7/1

19

94

/7/9

19

97

/7/1

7

20

00

/7/2

5

20

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/7/2

20

07

/7/1

0

20

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/7/1

8

19

81

/8/2

6

19

85

/8/3

19

88

/8/1

1

19

91

/8/1

9

19

94

/8/2

7

19

98

/8/4

20

01

/8/1

2

20

04

/8/2

0

20

07

/8/2

8

20

11

/8/5

19

82

/9/1

5

19

85

/9/2

6

19

89

/9/7

19

92

/9/1

8

19

95

/9/2

9

19

99

/9/1

0

20

02

/9/2

1

20

06

/9/2

20

09

/9/1

3

19

80

/10

/24

19

84

/10

/1

19

87

/10

/9

19

90

/10

/17

19

93

/10

/25

19

97

/10

/2

20

00

/10

/10

20

03

/10

/18

20

06

/10

/26

20

10

/10

/3

19

81

/11

/12

19

84

/11

/23

19

88

/11

/4

19

91

/11

/15

19

94

/11

/26

19

98

/11

/7

20

01

/11

/18

20

04

/11

/29

20

08

/11

/10

20

11

/11

/21

19

82

/12

/30

19

86

/12

/7

19

89

/12

/15

19

92

/12

/23

19

95

/12

/31

19

99

/12

/8

20

02

/12

/16

20

05

/12

/24

20

09

/12

/1

A2H083l: River Flow (down-stream of Hartbeespoort Dam m3/s)

Hydrologic Analysis: Flow-Duration Curves

0

5

10

15

20

25

30

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Flo

w (

M3

/s)

Duration (% of time)

Daily River Flows (A2H083)(12yrs split into dry/avg/wet)

wet years

avg years

dry years

Hydrologic Analysis: Selection of

Optimum Generating Capacity

Power

(MW)

Flow

(m3/s)

Assurance

(avg year)

Assurance

(wet year) Utilization

1.5 4.2 50% 70% 12 - 16hrs per day every day

4.2 12 25% 40% 50% to 80% of rainy season / 25% of dry season (peak 6hrs)

2x 4,2 24 10% 20% 20% to 40% of rainy season

9.9 29

Hydrologic Analysis: Future Scenario

Year MAR (m3/a) %

Increase

Surplus Yield

(m3/a)

Surplus as % of

4,2MW dry-season

flow need

hrs/day generating

capacity for 2nd

4,2MW turbine

1923 163 000 000

2010 217 000 000 33% 54 000 000

2035 292 396 754 79% 75 396 754 40% 9.5

2060 374 978 952 >100% 82 582 198 83% 20.0

PHASE-3:

TECHNICAL OPTIONS

Technical Options:

No river outlet

Right Bank of the dam:

• RB1: Refurbish & upgrade existing hydro installation (80 kW)

• RB3: New installation from un-pressurized tunnel / canal (1500 kW)

• RB4: New installation from pressurized tunnel (1800 kW)

Left Bank of the dam:

• LB1: Single unit new installation retrofitted between existing

isolating and sleeve valve control rooms (max 500 kW)

• LB2: Enlarged hydropower facility to utilize unallocated yield which

is currently spilled through crest gates (max 10MW)

Location: Technical Options

RB1

RB3

LB2

Combined

LB1

Refurbish & upgrade existing

yester-year installation

RB1

RB1: Upgrade yester-year Installation

1923 -1964

37kW capacity

Gilkes (UK)

Potential to double

Defunctional

Excellent Exhibits of Old Hydro Power

Existing Hydropower Installation

RB1: Upgrade existing Installation

• One turbine unit of Francis type

• Manufacturer: Gilbert Gilkes & Gordon in UK (1923)

• Effective head: 22 m

• Rated flow: 0,22 cub m per second

• Installed capacity: 37 kW with provision for 2nd unit

• Plant production between 1924 and mid 1960s

• Rehabilitated/upgraded capacity potential: 80kW

• Upgraded potential annual output: 0,672 GWh

• Estimated cost of rehab: about Rand 2,5 million

• Est. Unit Cost = R62m/MW

New installation

from un-pressurized tunnel

or siphoning from canal

1500kW

RB3

RB3: Possible Location

Optional combination with LB2

RB3: New Installation from tunnel

or siphoning from Canal

RB3: New installation + un-pressurized tunnel

• Existing yester-year hydro plant to be extended by new

building

• Large new penstock pipe connected to the existing outlet

tunnel to replace present 600 mm dia pipe

• Alternative: siphon from tunnel outlet

(higher environmental impact)

• The turbine design to take in consideration

– Head of 30m

– design flow = 5 m3/sec

• Estimated generating capacity of 1500kW or 8 GWh/a

• The costs of this development is estimated at R 20-30 mil +

• Est. Unit Cost = R17m/MW - R20m/MW

New installation

with pressurized tunnel

1,8MW

RB4

RB4: New Installation to pressurized tunnel

RB4: New installation with pressurized tunnel

• Existing yester-year hydro plant to be extended by new building to house two turbine units

• The outlet tunnel to be closed by a concrete structure housing two control valves for canal releases

• Large new penstock pipe connected to the existing outlet tunnel to replace present 600 mm dia pipe with 1300mm

• The turbine design to take in consideration water level fluctuation between 36 m and 39 m due to releases through the radial gates

• The design flow is suggested at 4,5 m3/sec

• Est. generating capacity = 1,8MW (10 GWh/a)

• The costs of this development is estimated at R38 mil + (R20/kW)

New retrofit installation

inline between existing isolating and

sleeve valve chambers

500kW

LB1

L/B Development of Hydro Power at

Hartbeespoort Dam – Actual Site

LB1: In-line turbine installation

LB1: In-line hydropower installation

• A single 1524 mm diameter outlet works pipe is bifurcated into three outlet pipes

• A hydro power unit is proposed to be retrofitted on the centre located 750 mm diameter outlet pipe

• Due to the spillway radial gates releases the minimum and maximum water heads are 14 and 16,7 m respectively

• The design flow is suggested at 3 m3/sec.

• Est. generating capacity = 500kW or 4,2 GWh/a

• The costs of this retrofit is estimated at R 8 mil + R16m/kW – R18m/kW

LB1: In-line hydropower installation

Enlarged hydropower facility

to utilize spillage & unallocated yield

8,4MW (4,2MW x2)

LB2

25 m3/s

LB2: Surplus Yield Generation

plan view

DA

M W

AL

L

River outlet

• Connect to 1524 mm diameter outlet works pipe with Y-junction in a separate valve control room

• Add penstock to new hydropower plant building: – 1500mm dia steel pipe

– 50m long (above ground and anchored)

– Split into 2 hydropower units and a river outlet

• 2 hydropower generator units with 4,2MW each

• Maximum water heads are 39 to 42 m

• The design flow is suggested at 25 m3/sec (2x12,5 m3/s)

• Est. generating capacity = 8,4MW

• The costs of this retrofit is estimated at R 120 mil + R14m/MW +

LB2 : Surplus hydropower installation

Phase-1: (26 GWh/a)

1,5 MW firm-yield generation from RB4

4,2 MW seasonal generation from LB2

Phase-2: (+4 GWh/a)

add 4,2 MW after 10 to 15 years from LB2

Combined

Retrofit vs New dam projects

• HBP retrofit unit cost = R12m/MW

• HBP greenfield unit cost (incl.dam wall) = R42m/MW

• Retrofit = low environmental impact (dam exists)

• Greenfield = high environmental impact

• Retrofit = short implementation (2 years+)

• Greenfield = long implementation (> 7 years)

Cost-Benefit

• Value of cleaning the dam? (own use)

• Value of environmental improvement?

• Social / property value?

• Value of affordable energy?

• Value of water loss in canals? (>50%)

• Pilot installation

– to demonstrate renewable energy options

– compare & integrate hybrid solution

– unlock value of “small” hydro solutions

END

Financials : Technical Options

• Operating cost = R80 /kW installed per year and R0.8 /MWh.

• Debt equity split of 30:70 assumed.

• Debt repayment period 13 years.

• ROE = 61c/kWh (IRR=14,7%)

• Interest rate of 14% assumed

• 2 year construction & commissioning

• Corporate tax rate of 30%

• Avg energy production of 69.4 GWh for ann.revenue calc (10MW)

– 25.1 GWh assumed to generate at peak hours associated tariff

– 44.3 Gwh assumed to generate at standard hours attracting off peak tariffs.

• Allowed for clean development trading mechanism (CDM) of 0.89

Kg/kWh CO2 displacement at US$ 4 /tonne.