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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
2 christof.gentner@andritz.ch
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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Pumped Storage: Technology for flexible Operation
Changing storage requirements
3
• 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
christof.gentner@andritz.ch
Pumped Storage: Technology for flexible Operation
Influence of non dispatchable power on pricing
4 christof.gentner@andritz.ch
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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Pumped Storage: Technology for flexible Operation
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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Pumped Storage: Technology for flexible Operation
6 christof.gentner@andritz.ch
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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Pumped Storage: Technology for flexible Operation
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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
Pumped Storage: Technology for flexible Operation
8 christof.gentner@andritz.ch
Advantages of variable speed
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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Pumped Storage: Technology for flexible Operation
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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
Advantages of variable speed
Pumped Storage: Technology for flexible Operation
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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
Advantages of variable speed
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Pumped Storage: Technology for flexible Operation
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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
Advantages of variable speed
Pumped Storage: Technology for flexible Operation
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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
Application example variable speed
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Pumped Storage: Technology for flexible Operation
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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
Application example variable speed
Pumped Storage: Technology for flexible Operation
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� 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
Application example variable speed
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Pumped Storage: Technology for flexible Operation
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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
Application example variable speed
Pumped Storage: Technology for flexible Operation
16 christof.gentner@andritz.ch
� 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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Pumped Storage: Technology for flexible Operation
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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
christof.gentner@andritz.ch
Comparison of fix and variable speed
Pumped Storage: Technology for flexible Operation
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Standardized pump turbines
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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Pumped Storage: Technology for flexible Operation
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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
Standardized pump turbines
Pump mode
Pumped Storage: Technology for flexible Operation
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Application range of concept
Turbine mode
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Pumped Storage: Technology for flexible Operation
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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
Standardized pump turbines
Pumped Storage: Technology for flexible Operation
22 christof.gentner@andritz.ch
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
Hydraulic short circuit
Power, turbine operation
Power, pump operation
Pelton turbine
Generator/Motor
Coupling
Pump
Pump operation
Turbine operation
Hydraulic short circuit
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Pumped Storage: Technology for flexible 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
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