pumped storage: technology for flexible operation - psh variable operation... · pumped storage:...

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Pumped Storage: Technology for flexible Operation Dr.-Ing. Christof Gentner

Golden, CO, USA, November 2012

Pumped Storage: Technology for flexible Operation

Contents

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The role of pumped storage

Machine concepts

Advantages of variable speed

Application example variable speed

Standardized pump turbines

Hydraulic short circuit

Pump turbine technology

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Changing storage requirements

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• Power mix as a major driver

• Share of intermittent production will increase significantly,

positive and negative reserve required

• Partly legal requirement to buy power from renewable production (Germany)

• Increasing demands relating to peaking and grid-frequency control

• World wide around 150 GW installed pumped storage capacity (2011)

Installed wind power world wide

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Influence of non dispatchable power on pricing

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Price for electricity on a sunny day in Germany

June 2005 and June 2012

Installed solar power and

peak price spread in Germany

Installed

solar power

Spread between

high price (8 am to 8 pm) and

low price (8 pm to 8 am) June 2005

June 2012

• Non dispatchable power influences price structure

• Storage capacity, both positive and negative is a technical requirement

• Required storage up to 80% of installed wind and solar,

depending on grid structure

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Required response time becomes shorter

� Renewable energy (wind, solar) is

extremely volatile, difficult to predict

and non dispatchable

� The stability of the grid is in danger

with large percentage of wind and

solar power

� The larger the wind and solar power

capacity, the larger the problems in

the grid

� The amount of renewables in the

electricity portfolio is increasing

rapidly

� New technologies for electricity

storage are needed to compensate for

those influences

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From static to dynamic

1920 1940 1960 1980 20202000

Cheap, domestic source of energy

Combination with irrigation and creation of navigable water ways

Quick grid controlHydro for grid stabilization

Hydro as compensation for wind und solarNew interest in pump storage

Hydro asSmart-Grid Player

Pump storage as long term storage

Renewable, clean energy

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Reversible Pump turbine

� Smaller cavern required

� Cost attractive solution (investment and maintenance cost)

� Lower complexity

� Longer change-over time (pump ↔ turbine)

� Pump start with drained runner

� Preferred method for pump startup

� electrical shaft „back to back“

� static frequency converter (SFC) in air

Pelton turbine

Generator/Motor

Pump

Reversible unit Ternary unit

Ternary units

� Both turbine and pump optimized

� Quick change-over time (pump ↔ turbine)

� Higher investment cost

� No start up device necessary

� Direct hydraulic short circuit possible

Machine concepts


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Variable speed

• Ability for variation of input power in pump operation

• Improved efficiency in pump and turbine operation

• Increased operation range pump and turbine operation

• Improved operation behavior

• Reduced pressure pulsation and vibration

• Increased life time of the hydraulic machines

• Reduced dynamic loads• Additional loss of converter

Fixed speed

• No power variation in pump• Non-optimal turbine operation

• No additional losses of converter

• Lower investment cost

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Fixed speed

FlowFlow

H min

H max H max

H minCavitation limit

Cavitation limit

Stability limit

Pump head, n sync

Efficiency

Efficiency

Pump Characteristics Turbine Characteristics

Sta

bilit

y m

arg

in

Head

Head

E

ffic

ien

cy



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Flow Flow

Cavitation limit

Cavitation limit

Stability limit

H max

H min

H max

H min

n sync + ∆n

n sync - ∆n

Pump head, n sync

Efficiency

Efficiency

Pump Characteristics

Head

Head

E

ffic

ien

cy

Variable speed

Turbine Characteristics

n sync - ∆n


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Head

E

ffic

ien

cy

Variable speed

Head

Flow Flow

H max

H min

H max

H minn sync + ∆n

n sync –∆n

Power input, n sync

Efficiency

Efficiency

Pump Characteristics Turbine Characteristics

n sync –∆n

Cavitation limit

Stability limit

Cavitation limit

Po

wer




Main data, size of pump-turbineSpecified Values Pump Mode Turbine Mode HWL max [m] 815

HWL min [m] 785 H gross max [m] 425

H gross min [m] 370 TWL max [masl] 415 TWL min [masl] 390

Pmax [MW] 250

H nominal [m] 400 Qmax [m

3/s] 63 69

n fix [MW] 428.6 n var [rpm] 400–440

Setting level (CLD) [masl] 350

1

2

3

45

6

7

8

9

10

1112

1314

15

16

17

0

100

200

300

400

500

600

700

800

900

60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360

nsq

H [

m ]

H, opt,max

1 Brasimone

2 Presenzano

3 Grimsel II

4 Cruachan

5 Waldeck II

6 Taloro

7 Solarino

8 Vianden 10

9 Leitzach

10 Panjiakou, n = 142.9 rpm

11 Panjiakou, n = 125 rpm

12 La Plate Taille

13 Guangzhou I

14 Bhira

15 Xikou

16 Tongbai

17 Lang Ya Shan

PT-USA

nsq = 3.651 ∗ n ∗ Q0.5

/ H0.75

Trend curve for maximum head, size of pump-turbine


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� Fix speed n =428.6 rpm layout: Main characteristic

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

40 45 50 55 60 65 70 75 80

Q [ m3/s ]

NP

SH

[ m

]

350

360

370

380

390

400

410

420

430

440

H [ m

]

NPSH,plant, all pumps NPSH,plant, 1 pump NPSH i

NPSH dETA=0% H Q,min

Q,max Stability limit Hstat=425m, all pumps

Hstat=370m, 1 pump

Setting level= 340 m.a.s.l.

Sufficientcavitation margin

Stability Limit




� Variable speed, pump mode:

Main characteristic

� n: 400 rpm – 440 rpm

� Pmax = 250 MW

� Power variation possible

between 30–70 MW

� Operation of pump at

best efficiency possible

over wide head range

175

185

195

205

215

225

235

245

255

265

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

350 360 370 380 390 400 410 420 430 440

P

[ M

W ]

Eta

[

% ]

H [ m ]

Stability limit TWLmax

TWLmin Pmax

Pmin Hmax

Hmin

n =400 - 440rpm

428.6 rpm

70 MW variation forconstant head of 380m

Operating range


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� Comparison: Turbine mode, operating area , fix - and variable speed

� Hill chart, fix speed =428.6rpm � Hill chart, var speed min =400 rpm for best efficiency

Turbine mode, at head 400m

fixed and variable speed

Improved efficiency over wide range

with variable speed




� To stabilize the grid a large amount of reserve capacity is needed

� The classical storage technology is

HYDRAULIC PUMPED STORAGE (HPS),

However:

� Large HPS plants are in mountain regions, often far away from wind farms

� Large distance between HPS plants and wind farms: additional loading for already stressed grid, additional transmission losses

� To compensate the very volatile wind and solar energy, the pump input power should be varied continuously. This was so far only possible with variable speed units (double-fed asynchronous motor-generators) which are rather expensive. Only few references in Europe and Japan are available.

Current solution

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Benefit of variable speed: ability to follow a variable demand for input power

Fixed speed: variation only by ON-OFF for complete units

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Comparison of fix and variable speed




Solution for grid stabilization based on

� Projects of smaller size for better chance of realization

� Flexibility in operation

� Progress in Full size converter technology

ANDRITZ HYDRO has developed a new innovative concept:

� Small decentralized pump storage plants with

� Standardized pump turbines with variable speed

� Synchronous motor-generator and

� Full size converter

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Concept

�Two different hydraulic designs

�17 machine sizes

�Full size converter, with speed variation from 0–100%

�Application range H=20–250 m and P=5–50 MW


Pump mode



Application range of concept

Turbine mode

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Pump head [m]

Pu

mp

in

pu

t p

ow

er

[M

W]

Advantages of the new concept

� The pump input power can be varied continuously due to full size converter

� Large power variations in pump mode

� Operation over very wide head ranges possible

� Flat efficiency characteristics

� Large speed variation (DFAM: only max. +/– 5–10%)

� Standardization due to variable speed (cost advantage compared to tailor-made small HPS units)

� Investment costs not significantly higher than fix speed solution




KOPS 2, Ternary units

� Customer: Vorarlberger Illwerke, Austria

� 3 x 180 MW Pelton turbines,

� 3 stage Pumps

� 3 x 200 MVA Generator/Motor

� Head range 696 – 826 m

� n = 500 rpm

� Highlights:

� Hydraulic short circuit enables variation of

input power by ± 100 %

� Pelton turbines pressurized

� Designed up to 60 load changes per day

� Ramp-up time to full load < 20 sec in pump

and turbine


Power, turbine operation

Power, pump operation

Pelton turbine

Generator/Motor

Coupling

Pump

Pump operation

Turbine operation


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Summary

Hydro power, pumped storage in particular, is becoming increasingly dynamic� Price spread is reduced� Flexibility and grid stability become important

Consequences for manufactures and operating utilitiesPeak efficiency alone not a sufficient measure to evaluate quality Focus on operating life and availability

Technical solutions for flexible operationVariable speed Ternary sets with short switch-over timesFull size convertersSmall scale, standardized pump storage plants

Benefit for operationOptimized hydraulic performance and cavitation safetySmooth and stable operation in wide operation rangeMaximum reliability though dynamic operationExtended service life

Pumped storage will very likely be the most beneficial storage solution to

integrate a high percentage of non dispatchable renewables in the grid

pumped storage: technology for flexible operation - psh variable operation... · pumped storage:...

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