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A Comparative Study on Suitable High Voltage Sources
for Ozone Generation
A. Suksri, K. Karnchanalekha, K. Tonmitra and P. Apiratikul
Research Laboratory of High Voltage Engineering, Department of Electrical Engineering,
Faculty of Engineering, Khon Kaen University, Khon Kaen, 40002, Thailand.
Phone +66-4320-2353, Fax +66-4320-2836, Email: amnart@elec.kku.ac.th
Abstract
This research is a comparative study on ozone
generation via the use of various high voltage sources to
improve efficiency of ozone generation. The high voltage
used are AC power supply at the frequencies of 50 Hz,
20kHz, 25 kHz and superimposed AC with DC source. The
superimposed high voltage source has a HVDC
superimposed with AC frequency of 20 kHz and 25 kHz
respectively. The constructed ozone generator is based on
a cylindrical concentric reactor that has the value of field
utilization factor (
η
*) of 9.45%. Ozone is generated by
corona discharge phenomena principle.
The results revealed that ozone generation by using only
AC high frequencies alone yield great ozone concentration.
On the other hand, a method of superimposed high voltage
source produced low ozone concentration as well as low
efficiency on energy consumption concerned. Therefore, in
an application that needs ozone concentration below 600
ppm, the choice of suitable high voltage source is AC 50
Hz. For an industrial application that needs more
concentration of ozone gas, the choice of high voltage with
high frequency power supply is much more attractive due
to the efficiency of ozone concentration and reasonable
power consumptions.
Keywords: ozone, corona discharge, superimposed
I. INTRODUCTION
At Present, there are many applications of ozone in an
industrial such as waste water treatment, hospital
disinfectant and controlling the quality of drinking water
management at the water municipality. Since ozone is a
strong oxidizing agent, it can be used in various
disinfecting applications. Ozone can be generated by
lightning phenomena in nature. It can also be generated
from corona discharges from strong electric field or it can
be obtained from UV radiation. However, ozone that is
obtained from the UV radiation is of little amount and not
effectively done.
From past until present, researches have been mainly
focus on the concentration levels of ozone through the
corona discharge principle and looking for a suitable
strong electric field configurations[1]. An alternative
approach is to rely on the electrode configuration [2] and
choosing the various high voltages power supply method.
While choosing a uniform field electrode configuration,
there will be less amount of energy used in producing
ozone at the same level of supply voltage to that of highly
non-uniform electric field configuration but with the less
amount of ozone concentration. Therefore, the choice of
various high voltage sources must play an important role
in producing ozone concentration as well as energy
efficiency concerned.
It has been found that an ozone generator that is
available on the market is of low efficiency. One must
realized that with an energy input of 100 per cent only 10
per cent is contributed to the ozone production and the
rest is converted to the loss in the system in the form of
light, sound, and heat finally. So that, in order to design
an effective ozone generator, the system must have better
cooling to prevent ozone from being destructed by heat
and any other form of losses. Apart from the parameter of
heat, there are many other parameters that have
contribution on ozone yields such as the thickness of the
dielectric used, frequency on the supply voltage, the
space between the discharge gap, the pressure in the
discharge gap, and electrode materials. Also, the
configuration of electrode can be attributed to the ozone
yields as well.
In this research we mainly focused on the choices of
various high voltage sources using AC power supply at
the frequencies of 50 Hz, 20 kHz, and 25 kHz As well
as superimposed AC with DC sources. The principle of
superimposed high voltage source has a HVDC
superimposed with AC frequency of 20 kHz and 25 kHz
as shown in the figure 1.
Figure 1. The principle of superimposed high voltage source has a
HVDC superimposed with AC frequency.
II. MATERIALS AND METHODS
A. Current measuring device
Corona current produced during ozone generation is
measured using a Hall-effect current transducer (LEM
HX03-P/SP2) which has a capability of measuring both
DC and AC signals. The signals obtained from the
transducer is then amplified and buffered through the use
of an instrumentation operational amplifier (Burr-Brown
INA122) in the form of voltage signals fed to a digital
978-1-4244-3388-9/09/$25.00 ©2009 IEEE
storage oscilloscope (Tektronix TDS1001B) for capturing
the waveform purpose.
B. Cylindrical concentric reactor
The configuration of concentric cylindrical
arrangement is shown in the figure 2; it is consisted of
two electrodes with a glass as a dielectric barrier placed
in the middle [3].
Figure 2. The configuration of concentric cylindrical reactor.
Figure 3. The actual photograph of concentric cylindrical reactor.
C. The 50 Hz high voltage power supply
The first high voltage power supply uses the power
line frequency (50 Hz) as shown in the figure 4.
Figure 4. The 50 Hz High voltage power supply.
D. The high frequency high voltage power supply
The second high voltage power supply uses the high
frequency switching through active device as shown in
the figure 5.
Figure 5. The switching high frequency high voltage power supply.
E. The superimposed high voltage power supply
The third high voltage source has a HVDC
superimposed with AC frequency of 20 kHz and 25 kHz
as shown in the figure 6.
Figure 6. The superimposed high voltage power supply.
F. Flow process of ozone generation
Ozone is generated through the three aforementioned
types of high voltage power supply in this research. In
order to control the ozone production, a compressed air
tank is used as a raw material for air supply. The
compressed air is then filtered and passes through a mass
flow meter to monitor for a constant flow rate. When the
compressed air is passed through the reactor, the
molecules of oxygen are excited by an external energy
that is a strong electric field giving rise to the
recombination processes of oxygen atoms to form ozone
production.
The concentration of ozone gas is analyzed by
connecting a flow of ozone products to the ozone
analyzer (Teledyne Instruments Ozone Monitor Model
450M). During the ozone production, the corona current
is measured; levels of high voltages used are measured by
high voltage resistive divider with the ratio of 1: 1000 V
and Fluke high voltage probe (HV Probe Fluke® Model
80K-40). The process of controlling and measuring
scheme is shown in the figure 7 below.
Figure 7. The flow diagram of ozone generation.
r
1
r
2
r
3
Glass
tube
HV
Electrode
Ground
Electrode
III. ANALYTICAL METHODS
Experiments were conducted by applying high voltage
to the inner electrode and using glass tube for serving as a
dielectric barrier that has a thickness of 1 mm and has a
dielectric constant of 3.5. The outer electrode has an
inside diameter of 0.65 cm and outmost of 0.75 cm. This
outer electrode is fixed throughout the whole experiment
and function as a return conductor. Variation of high
voltages power supply will be another important factor in
the process of ozone generation. The best optimum key
parameter is to find the way how ozone concentration is
produced versus energy consumption in an hour
(mg/kWh). Thus, a comparison will then be made on the
application of applying various types of high voltage
power supply in order to find for better production of
ozone efficiency.
Ozone efficiency can be analyzed under the controlled
experiment and ozone production can be calculated as
equation (1) and (2) below. The concentration is
expressed as a part per million (ppm) and the flow rate
used can be controlled from 1-10 L/min.
3
33
O [mg/h]= Concentration of O [g/Nm ] Flow rate[L/min] 60××
(1)
Where
1 g/Nm3 = 467 ppm
The ozone efficiency can be computed from an equation
below [4].
3
Produced Ozone [g/Nm ]
Ozone efficiency [g/kWh] = Discharge Power [W] (2)
The discharge power is obtained by collecting the data of
current and voltage used during the discharge period.
2
0
1()
t
rms
Vvtdt
T∫
= (3)
2
0
1()
t
rms
Iitdt
T∫
= (4)
Where:
rms
V is an effective value of voltage (V)
rms
I
is an effective value of current (A)
()vt is an instantaneous value of voltage (V)
()it is an instantaneous value of current (A)
T is a period of time (Sec)
The electrical discharge power can be analyzed by the
averaged of instantaneous power in the time domain as
shown.
() ()*()Pt vt it= (5)
Hence,
0
1()
t
av
PPtdt
T∫
= (6)
Where
()Pt is an instantaneous power (W)
av
Pis an average value of real power (W)
IV. EXPERIMENTAL RESULTS
Figure 8 to 12, showed the results of ozone efficiency
versus ozone concentration on different types of high
voltage power supply.
OZONE CONCENTRATION [ppm]
0 100 200 300 400 500 600
OZONE EFFICIENCY [mg/kWh]
0
50
100
150
200
250
3.2 kV AC 50 Hz.
4.2 kV AC 50 Hz.
5.2 kV AC 50 Hz.
1 L/min
2 L/min
3 L/min
10 L/min
Figure 8. The comparison of ozone concentration and efficiency on AC
50 Hz high voltage power supply on descending flow rate.
OZONE CONCENTRATION [PPM]
0 500 1000 1500 2000 2500 3000
OZONE EFFICIENCY [mg/kWh]
0
10
20
30
40
50
60
3.8 kV AC 20 kHz.
4.0 kV AC 20 kHz.
1 L/min
2 L/min
3 L/min
10 L/min
Figure 9. The comparison of ozone concentration and efficiency on AC
20 kHz high voltage power supply on descending flow rate.
OZONE CONCENTRATION [PPM]
0 500 1000 1500 2000 2500 3000
OZONE EFFICIENCY [mg/kWh]
0
10
20
30
40
50
60
70
1.8 kV AC 25 kHz.
2.1 kV AC 25 kHz.
1 L/min
2 L/min
3 L/min
10 L/min
Figure 10. The comparison of ozone concentration and efficiency on
AC 25 kHz high voltage power supply on descending flow rate.
OZONE CONCENTRATION [PPM]
0 100 200 300 400 500
OZONE EFFICIENCY [mg/kWh]
0
5
10
15
20
25
30
3.4 kV (DC 3 kV Superimposed AC 20 kHz.)
4.4 kV (DC 4 kV Superimposed AC 20 kHz.)
1 L/min
2 L/min
3 L/min
10 L/min
Figure 11. The comparison of ozone concentration and efficiency on
superimposed DC and AC 20 kHz high voltage power supply on
descending flow rate.
OZONE CONCENTRATION [PPM]
0 100 200 300 400 500 600
OZONE EFFICIENCY [m g/kWh]
0
5
10
15
20
25
30
3.5 kV (DC 3 kV Superimposed AC 25 kHz.)
4.5 kV (DC 4 kV Superimposed AC 25 kHz.)
1 L/min
2 L/min
3 L/min
10 L/min
Figure 12. The comparison of ozone concentration and efficiency on
superimposed DC and AC 25 kHz high voltage power supply on
descending flow rate.
V. DISCUSSIO NS
It can be observed that, by applying the equation (1) to
(6) ozone concentration as well as ozone efficiency can
be calculated. In all cases of power supply used, a
threshold of ozone concentration of 600 ppm will be used
as a based value for ozone usefulness. The superimposed
high voltage power supply has the lowest values on ozone
efficiency and ozone concentration in all cases of flow
rate used. The figure obtained is 28.61 mg/kWh for the
efficiency and ozone concentration of 494 ppm by the
method of superimposed 4.5 kV DC with AC at 25 kHz.
The choice of low frequency AC 50 Hz power
supply alone at the level of 5.2 kV gave rise to the ozone
efficiency at 190.12 mg/kWh at the flow rate of 1 L/min.
When the high voltage with high frequency was used at
the voltage level of 2.1 kV 25 kHz, the ozone
concentration obtained is exceeded the threshold value at
2,856 ppm with the ozone efficiency of 61.83 mg/kWh.
Figure 13 reveals the comparison on ozone
efficiency and ozone concentration in all cases of high
voltage power supply used. In an application of ozone
concentration, the AC high frequency yields great results
but in contrast, high voltage AC 50 Hz alone has the
highest efficiency. Lastly, one important parameter that
affects ozone production is the air flow rate used.
OZONE CONCENTRATION [PPM]
0 500 1000 1500 2000 2500 3000
OZONE EFFICIENCY [mg/kW h]
0
50
100
150
200
5.2 kV AC 50 Hz.
4.0 kV AC 20 kHz.
2.1 kV AC 25 kHz.
4.4 kV (DC 4 kV Superimposed AC 20 kHz.)
4.5 kV (DC 4 kV Superimposed AC 25 kHz.)
1 L/min
2 L/min
3 L/min
10 L/min
1 L/min
2 L/min
3 L/min
10 L/min
Figure 13. The comparison of ozone concentration and efficiency on all
types of high voltage power supply on descending flow rate.
VI. CONCLUSIONS
Ozone generation using only AC high frequencies
alone yield great ozone concentration. A method of
superimposed high voltage source is, however, produced
low ozone concentration as well as low efficiency on
energy consumption concerned. Therefore, in an
application that needs ozone concentration below 600
ppm, the most suitable choice of high voltage source is
AC 50 Hz alone due to its efficiency. Also, for an
industrial application that needs more concentration of
ozone gas, the choice of high voltage with high
frequency power supply is much more attractive
configuration due to the ozone concentration obtained.
ACKNOWLEDGMENT
Authors wish to express thanks to the High-Voltage
Research Laboratory, department of Electrical
Engineering, Khon Kaen University, Thailand. Also,
grateful thanks to Mr. Promsak Apiratikul of
Rajamankala University, Tanyaburi, Nakorn Nayok,
Thailand for technically supporting on ozone analyzer
equipment.
REFERENCES
[1] C.Boonseng, V.Kinnares, P,Apiratikul, “Harmonic Analysis of
Corona Discharge Ozone Generator Using Brush Electrode
Configuration”,Power engineering Society, 2000.IEEE, Vol.1, 23-
27 Jan 2000 , pp.403-408.
[2] Suksri A., Tonmitra K., Karnjanalekha K. “The Correlation
between Electrode Sizes and Ozone Generated by Corona
Discharges Phenomena.” Proceeding of ECTI International
Conference; 2006 May 10-13 ; Ubon Ratchathani, Thailand;
2006. pp. 405-408
[3] Samruay Sankasa-ard, “High Voltage Engineering,” Chulalongkorn
University, Bangkok, Thailand, 2nd ed., 2004. ISBN 974-92125-5-x
[4] Ahn H.S., Hayashi N., Satoh S. “Ozone Generation Characteristics
of Superimposed Discharge with Surface and DC Discharge”.
Reports of the Faculty of Science and Engineering Saga University
2001; 30: pp. 25-32.
