Applications of a Vanadium Redox-flow Battery
to Maintain Power Quality
T. Shigematsu, T. Kumamoto, H. Deguchi, and T. Hara
Suntitorno Electric Industries, Ltd., Osaka, Japan
Abstrucf-The vanadium redox-flow battery (VRB) is a
rechargeable battery. The VRB has a quick response time and
E . OPERATING
PRINCIPLES AND FEATURES OF THE VRB
an outstanding high-rate charge and discharge performance for
A..
Structure
ond
Operating
Principles of the VRB
short time periods. The capacity of the VRB can be easily
As shown in Fig. 1, a VRB is comprised of a battery cell
specified by increasing or decreasing the quantity of electrolyte.
By utilizing all these features, the VRB can form an eKective section where the battery reaction takes place, positive and
system to maintain power quality, such as a voltage sag negative tanks containing electrolyte, and a pump and piping
compensation system, a stabilizing system for output for circulating the electrolyte from the tanks to the cell. The
fluctuations of wind turbines.
VRB is connected to an AC system via an AClDC converter.
SEI delivered a VRB to a semiconductor plant as a voltage
The
active material for both the positive and negative
sag compensation system in April 2001. This system normally
operates at the rated output of 1.5 MW as a load leveling electrodes of the VRB is vanadium ions that are dissolved in
system. Should a voltage sag occur, it can deliver 3 MW for 1.5 sulfuric acid and serve as metal ions whose valence number
seconds. This VRB has already completely compensated 20 changes. The changes in valence number of the ions
voltage sags.
(oxidation and reduction reactions) enable the battery to
SEI delivered a VRB for the project of The New Energy and store and discharge electric power. A simplified version of
Industrial Technology Development Organization (NEDO) in
March 2001, and it is nuder evaluation at a WT power plant of the reaction equation is as follows:
Positive electrode: V4' o V5' + eHokkaido Electric Power Company. The VRB's rated output
Negative electrode: V3' o V2' + epower is 170 kW, and it can be operated up to a maximum
power of 275 kW. The VRB has already been found to
(+: charging, +: discharging)
demonstrate good performance.
* The left-to-right reaction occurs during charging and the
right-to-left reaction occurs during discharging.
Index Terms-Vanadium redox-flow battery, Energy storage,
Voltage sag, Wind turbine, Power quality
I.
INTRODUCTION
T
HE vanadium redox-flow battery (VRB) is a
rechargeable battery in which a vanadium solution is
used as the electrolyte. Kansai Electric Power Company
(KEPCO) and Sumitomo Electric Industries (SEI) have been
developing the VRB since 1985. [I] [3] The VRB has a
quick response time and an outstanding high-rate output
performance over short time periods. As an example, a VRB
has demonstrated a response time of 350 U s , and at a state
of charge (SOC) of 90%, displayed the high-rate output
performance of 4.5 times the rated output for one second and
three times the rated output for one minute. [2] The capacity
of the VRB can be easily specified by increasing or
decreasing the quantity of electrolyte. By utilizing all these
features, the VRB can be an effective system not only for
conventional load leveling applications but also for
momentary voltage sag compensation and stabilizing the
output fluctuations of wind turbines. In this paper the
implementation is described of a VRB in the latter two
applications.
0-7803-7525-4/02/$17.00 0 2002 IEEE.
Fig. 1. Slruclure and principle of a Vanadium Redox Row Ballery(VRB).
VRB Feotures
The VRB offers a wide range of features and can be used
in a variety of applications.
B.
a) The reaction mechanism is simple (merely changes in
valence number) and the recharging-discharging cycle life is
extremely long.
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b) The output section (cells) and storage sections (tanks)
are independent of each other, making it easier to design the
output and storage sections according to the constraints of
the application. This feature also adds flexibility lo
installation layout by enabling, for example, only the tanks
to be installed underground.
c) The VRB has an instantaneous response in the order of
milliseconds and is capable of high-rate discharge over short
periods several times larger than the rated output.
Consequently, the VRB is well-suited to absorbing the
irregular output fluctuations inherent to renewable energy
generation.
d) The VRB operates at room temperature and is easy lo
maintain.
e) There is no emission of COz and the electrolyte is
recyclable, making the VRB environmentally friendly.
IlI. APPLICATION
TO POWER QUALITY MAINTENANCE
A. Applicatiori to a Momentary Voltage Sag Compensation
System
In facilities such as semiconductor manufacturing plants,
momentary voltage sags can cause substantial damage such
as defective half-finished products and business opportunity
losses associated with equipment recovery. Protection
against such damage requires instantaneous high output for
extremely short periods of time. A VRB can provide an
economical solution that meets these requirements using a
suitable instantaneous high-rate output performance and a
tank capacity volume matched to the short-period capacity.
A peak cut function can also be provided if required. In
2001, SEI delivered a VRB system for use as a momentary
voltage sag compensating system in a semiconductor plant.
I ) Overview of the Delivered System
The specifications of the delivered VRB system are
shown in Table 1. The external appearance of the equipment
is shown in Fig. 2.
TABLE 1
SYSTEM SPECIFICATIONS FOR A
SEMICONDUCTOR
MANUFACTURING
PUNTS
outnut
- r
Rated discharge
capacity
A C Terminal voltage
1,500 kW
Load leveling
kwh
6,600 V
The system constantly maintains the soundness of the
equipment by operating with a normal peak cut of 1.5 MW.
Fig. 2 Battery cubicle containing Cell-Stack of VRB in
manufaduring plans
a
semiconductor
The system also helps reduce electricity costs by utilizing
inexpensive nighttime electric power. Whenever a
momentary voltage sag occurs, the battery can deliver the
equivalent of twice its rated output, i.e., 3 MW, for 1.5
seconds with negligible delay.
2) Operating Results
The twenty momentary voltage sags that have occurred
thus far have all been successfully compensated for by the
system.
B. Application to Stabilization of Output Fluctuations of
Electricity Generated from Wind Power
Japan is aiming to generate 3,000 MW of electricity from
wind power by the year 2010. In the meantime, the effect of
wind turbine output fluctuations on power systems is under
discussion as a problem that must be dealt with before wind
power can be introduced. It is believed that combining wind
turbines with storage batteries could be an effective solution.
Currently the New Energy and Industrial Technology
Development Organization (NEDO) has different types of
storage batteries installed at wind power generation stations
and is conducting verification tests on stabilization of output
fluctuations. SEI delivered a VRB with a rated capacity of
170 kW (maximum 275 kW) for this project in March 2001.
It was installed lo work in combination with a wind turbine
(275 kW) at Hokkaido Electric Power Company's Horikappu
Wind Power Station, where the tests are being conducted on
stabilization of wind turbine output fluctuations.
1 ) Sumciary of Stabilization Test on Wmd Turbine Output
Fluctuatiotu
An overview of the system structure is shown in Fig. 3.
connected to the power system and functions to stabilize
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- -
TABLE 2
Purpose : Field test for stabilizing
Commissioned
[L NED0
Spec. : 170kW x
IAE
mriizzz
II
loutnu
Outuu
(The I i i s i i l ~ t e
Amlied
SEI
SYSTEM
SPECIFICATIONS
FOR APPLICATION
TO WIND POWER
11
STATION
Parameter
Specification
I
Rated Output
1
Maximum Output
-
170kW during 3 hours
(to reduce electrolyte volume by
halves)
275 kW
(to utilize the high- rate output
performance)
VRJ3
01/ F-9/E Field
-021 E
Data
Fig. 3 An overview of Ihe syslem structure for application
Io wind power
rlalion
output fluctuations by absorbing changes in the output of the
wind turbine. Wind turbine output fluctuations generally
include components ranging from those with relatively long
periods to those with very short periods. The battery system
has excellent momentary response and is expected to be
capable of handling both long- and short-period components.
The wind turbine output fluctuations are stabilized
using the following method. The actual output of the wind
turbine is passed through a low-pass filter having a certain
time constant and the output value after the short-period
components have been removed is set as the target value for
stabilizing. A portion of the output equivalent to the
difference between the target value and the actual wind
turbine output value is sent lo the battery.
2) Evaluation Conditions of VRB Installed at Hokkaido
Electric Power Company’s Horikappu Power Plant
A summary of the system specifications is shown in Table
2 and the appearance of the system is shown in Fig. 4.
Characteristic features of the system include the following:
the electrolyte tank is divided into two parts; the system is
capable of a 3-hour capacity test; and the system is designed
such that tests can be conducted to evaluate the
instantaneous high-rate output performance of the VRB in a
situation where the inverter output is 275 kW, which is equal
to the rated output of the wind turbine and largcr than the
rated output of the VRB.
3) Stabilizarioii Test Conrlitiotis
a) Stabilization data for time constants of eight minutes,
one hour, and eight hours are shown in Figs. 5 , 6, and 7. The
longer the time constant is, the greater the degree to which
the output fluctuations are stabilized. Simultaneously, the
output demand on the battery becomes larger and a larger
Fig.4 Appcardnce of VRB combimed wilh Horiksppu Wind Power Station
of Hokkaido Electric Power Co.,lnc.
capacity battery is required
b) Stabilization data for a time constant of one hour when
operating at 112 capacity (3-hour capacity) is shown in Fig. 8.
Although the amount of elecfrolyte has been reduced by one
half to achieve a capacity of three hours, the degree of
stabilizing exhibits similarly good results.
c) Stabilization data (time constant 1 hour) for when the
high -rate output characteristics are utilized are shown in Fig.
9. The system responds as a battery without any problems
and it has been successfully verified that it can output 275
kW. The data also illustrate that the degree of stabilization is
improved accordingly.
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....
O:M
2:M
403
6:M
-
,
.
.
. .
8:M l 0 : M
12W 1 4 0 0 16W 1800 M03 2'203 003
Tlme
Fig. 5 Stahililalion data for lime conslants of 8 minuter : 2001/05/18
(VRBl70kWl6h a1 Hokkaido Eledric Power Company's Hariksppu WT Power Planl)
5w
g
400
d
g
8
3m
200
discharge'
0
charge t
~
-la,
-m
-3@n
o m
200
400
s m
800
r o o 0 12:w
Tlmc
,400
16:m 18:w 2000
22w
om
Fig. 6 Stahilizalian data for lime conslants of 1 houm: 2001/05/22
(VRB170kW/6h SI Hokkaido EIeclric Power Compmy'r Horikappu \yT Power Planl)
+
m
B
8300
200
103
dlrrhsrge
0
charge
di,
00
-MO
50
-1
-300
003
t
U
0
203
403
6:O
803
1 0 0 3 1 2 0 3 1400 1603 1 8 0 3 2003 22:m 003
The
Fig. 7 Stabilization ddld lor lime UlnStdnls 01 8 hours : 2001/04/06 (VRB170kW/hh
at Hokkaido Electric Power Company's Horikappu WT Powcr Planl)
1068
E!
P
a-
-
005
V
50
boo i:bb 4:L
0
630
i:oO ioioo iiibo iCoo iS:oo iGoo i t o o ziloo U:oo
9
Time
Fig. 8 Stabiliration data for lime conslanls of 1 hours when operating at t i 2 capacity: 2001110120
(VRB:l70kWl3h al Hokkaido Electric Power Company's Horikappu W Power Plant)
sm
S
4m
Y
d s m
s.
g
203
im
discharge $
0
charge
c
I
m
100
a
-3m
om
50
zm
+m
em
em
tom
izm
iwn ism
inm mm 2zm
om
8
"
z
0
$
Time
Fig. 9 Slabiliialion dala for lime conslanl~of 1 hours r h e n the high -rale output caracteristics itre ulilized:
2001/11/26(VRB:275kW al Hakkaido Electric Power Company's Horikappu W Power Plant)
4) Observations
The response of the VRB, which also includes an inverter,
is on the order of a millisecond. The results of this study are
b e l i e v e d t o d e m o n s t r a t e that t h e s y s t e m a c h i e v e s
stabilization that is consistent with the original aim. The
degree of stabilization and the required battery capacity vary
greatly depending on the time constant. The required degree
of stabilization should be determined in response to the
economical factors of the battery system and the system
control requirements.
Regarding wind turbine output stabilization
applications, it is speculated that the required battery
capacity can ultimately be reduced to approximately 20% of
the rated output of the wind turbine by utilizing the
instantaneous high-output performance of the VRB. The
authors wish to study this possibility further.
N . CONCLUSIONS
As a result of environmental problems and deregulation of
the electric power industry, a variety of distributed power
sources, among them wind power, will be introduced into
future electric power systems. It is expected that electric
power storage technology will become a key technology in
electric power systems for ensuring supply reliability and
maintaining power quality. The VRB has unique
characteristics not seen in other batteries and it is believed
that these characteristics can be utilized in a wide variety of
applications in addition to those discussed in this paper. We
have reached the practical application stage, and will need to
focus development work on reducing cost and improving
practical applicability.
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H i r o s h i g e D E G U C H I was born on Nov.22.1966.He
received M.S. degrees in Electrical
Engineering from Tokyo University,
Tokyo, Japan in 1991. Since 1991
he has been an Engineer of
Sumitorno Electric Industries and is
currently Assistant Manager of
Energy Storage System
Development Group. He is in charge
of the development of Redox Flow
Battery. Mr.Deguchi is a member of
the Institute of Electrical Engineers
of Japan.
V . REFERENCES
[ l ]N. Tokuda, Y. Miki, H. Arai, K. Yamamoto, K. Eniura,
K. Motoi, T . Shinzato, and T. Kanno, ”Vanadium
R e d o x F l o w B a t t e r y S y s t e m for Use i n O f f i c e
Buildings,” in Electric Energy Storage Association
Technologies, Sep. 2000.
[ 2 ] T. Kaizuka and T. Sasaki. “Evaluation of Control
M a i n t a i n i n g E l e c t r i c P o w e r Q u a l i t y by u s e of
R e c h a r g e a b l e B a t t e r y S y s t e m ” , in I E E E P o w e r
Engineering Society Winter Meeting, 2000.
[3] M. Miyake, and N. Tokuda, “Vanadium Redox Flow
Battery for a Variety of Applications”, in IEEE Power
Engineering Society Summer Meeting, 2001.
Takushi HAM was bo1‘n on Sep.27.1949. He received M.S.
degrees in Electrical Engineering
from Okayama University,
Okayama, J a p a n i n 1 9 7 4 . Since
1974 he has been an Engineer of
Sumitomo Electric Industries and is
c u r r e n t l y G e n e r a l M a n a g e r of
Energy Storage System
Development Group. MI. Hara is a
member of the Institute of Electrical
Engineers of Japan.
VI. BIOGRAPHIES
T o s h i o S H I G E M A T S U was born on Dec.2.1956. H e
received M.S.degrees in Applied
Physics from Osaka University,
Osaka, Japan in 1982. Since 1982
he h a s b e e n a n E n gineer of
Sumitomo Electric Industries and
is currently assistant General
M a n a g e r of Energy Storage
System Development Group. He is
i n charge of the development of
Redox Flow Battery.
MrShigematsu is a member of the Institute of Electrical
Engineers of Japan.
T a k a h i r o K U M A M O T O was born on Nov.20.1968. He
received B.S. degrees in Electrical
Engineering from Osaka City
University, Osaka, Japan in 1992.
Since 1992 he has been an Engineer
of Sumitorno Electric Industries and
is c u r r e n t l y member of Energy
Storage System Development Group.
He is in charge of the development
of Redox Flow battery.
..
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