The Effect of Electrical Variables on Hydrogen and Oxygen ...electrode on the efficiency of water electrolysis at a particular concentration. Abdallah et al. investigated the effect

International Journal of Applied Engineering Research ISSN 0973-4562 Volume 12, Number 13 (2017) pp. 3730-3739

© Research India Publications. http://www.ripublication.com

3730

The Effect of Electrical Variables on Hydrogen and Oxygen Production

Using a Water Electrolyzing System

Hanan Saleet*a , Salah Abdallah b, and Essam Yousef c

a,b,cApplied Science Private University, Mechanical and Industrial Engineering Department, P.O. Box 166, Amman, Jordan.

(*Corresponding author)

Abstract

Water electrolysis (splitting water) is an efficient method of

producing hydrogen and oxygen. The production efficiency

depends on important design variables such as the electrical

variables. This work presents an experimental study that was

conducted to investigate the effect of the following electrical

variables: AC voltage amplitude, waveform and frequency,

and DC voltage amplitude. The electrolyser splits water into

hydrogen and oxygen when an electric current passes between

two flat plate shaped electrodes immersed in water and

separated by non-electrical conducting material; this material

is resistive Teflon. From the experimental results, it can be

seen that the square waveform has the maximum hydrogen

and oxygen production followed by sawtooth waveform.

Therefore, using sinusoidal waveform as the base case, the

gain in total productivity can reach up to 489% for sawtooth

waveform, and up to 680% for the square waveform. In

addition, it is seen from the experimental results that the gain

in production of hydrogen and oxygen in case of DC input

voltage, for the same range of voltages, can reach up to

1100%. Therefore, it is clear that using DC input voltage such

a solar system can enhance the efficiency of hydrogen and

oxygen production.

Keywords: Electrical variables; Water electrolyzer; Hydrogen

and oxygen production.

INTRODUCTION

Due to the depletion of traditional energy resources, such as

crude oil, coal, and natural gas, many initiatives all over the

world have addressed the efficient use or replacement of these

resources [1 ] - [6 ]. Several renewable energy sources have

been introduced as alternatives to traditional sources to protect

environmental resources and to improve the quality of life [7

]. Using renewable energy sources represents a bright future

for humanity because they utilize a clean, and sustainable

fuel; the sun, wind, water, etc. [8 ]. Electrical energy produced

using photovoltaic systems is a sustainable energy resources.

The most important drawback of using photovoltaic systems

to generate energy is the change in sunlight illumination

through daytime and the absence of solar radiation at night

time [9 ], [10 ]. Thus, it is essential to store the energy in

batteries or store the energy into another material i.e. store

energy into high energy materials, such as hydrogen and

oxygen gases [11 ] - [14 ]. Water electrolysis is used to

produce hydrogen where electric current passes through water

resulting in splitting water into hydrogen and oxygen [15 ] -

[17 ]. Hydrogen stores electrical energy [18 ]. It can be used

to generate electricity in a fuel cell by a process that is the

reverse of electrolysis [19 ]. A life cycle assessment of the

processes indicates that it has minimal environmental burden

[20 ]- [22 ], compared to the quite considerable savings

offered [23 ], [24 ].

"The demands for energy are increasing as countries become

richer" mentioned Winterbone in [25 ]. Gutierrez-Martin et al.

suggested to build large number of electrolyzer plants in

Spain [26 ]. Abdel-Wahab et al. explored the application of

Fuel-Cell Energy Systems, which utilizes hydrogen from

renewable sources in the UK environment [27 ]; and [28 ],

and [29 ] investigated the potential of hydrogen production in

Algeria.

In addition, researchers developed mathematical models to

test the electrolyzer system under different conditions. For

example, Paul and Andrews presented a theoretical analysis of

a mathematical model that tests the conditions required for

connection of a photovoltaic array to an electrolyzer in solar

hydrogen systems [30 ]. Also, Bilgen presented a

mathematical model that aims to optimize the thermal

conditions and also optimize the economics of large scale

photovoltaic electrolyzing systems [31 ]. On the other hand,

researchers built simulation models to study the different

theories how to optimize hydrogen production. In [32 ],

Rabady used simulation to examine the utilization of sunlight

using a hybrid thermo-electrolysis system to produce

Hydrogen. Paola et al. created a simulation program that

compares different technological options in order to optimize

the PV-electrolysis system [33 ]. Khalilnejad and Riahy

designed and modeled a hybrid wind–photovoltaic system for

the purpose of hydrogen production through water electrolysis

[34 ].

mailto:[email protected]





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Many design parameters were investigate in the literature

such as the effect of TDS (Total Dissolved Solids) [35 ], and

the effect of PH levels [36 ]. In addition, Mahrous et al. in [37

] and Chennoufa et al. in [38 ] investigated the effect of input

voltage amplitude. Higher production rates can be obtained at

higher input voltage. Nagaia et al [39 ] and [40 ] used an

alkaline water electrolysis to study the effect of current,

temperature, distance between electrodes and bubbles between

electrode on the efficiency of water electrolysis at a particular

concentration. Abdallah et al. investigated the effect of

connection type (either parallel or series) of the solar panels

on the production rate [41 ]. This work aims to investigate the

effect of AC voltage amplitude, AC voltage waveform, AC

voltage frequency, and DC voltage on the hydrogen and

oxygen production.

EXPERIMENTAL DESIGN OF THE SYSTEM

In purpose of investigating the effect of AC voltage

amplitude, AC voltage waveform, AC voltage frequency, and

DC voltage on the hydrogen and oxygen production, testing

electrolyzing rig is built. A schematic diagram of water

electrolyzer, used in this work, is presented in Figure 1. The

system consists of pulse generator, power amplifier, DC

power generator, water electrolyzer, bubbler, and hydrogen

and oxygen measurement instrument.

Figure 1 : Schematic Diagram of water electrolyzing system.

The detailed information about each element of this system

can be described as following:

A) Pulse generator:

The electrical power generator used in this system is a pulse

generator. The main technical characteristics of pulse

generator 8120, which is used in this system, are: frequency

range from 0.1 Hz to 2MHz. Output voltage from 5mV to 2V,

and offset DC voltage is +10.

B) Power amplifier:

Power amplifier is used to amplify the voltage generated at

the output of pulse generator. The main technical data of

power amplifier 2712, which is used in this system, are:

power output capacity is 180 VA, frequency range from 0 to

100KHz.

C) DC Power supply:

DC power supply is used to generate regulated DC voltage. In

this work, regulated power supply model XP-650 is used and

its main technical data is as following: input voltage is 120

VAC or 220 VAC, output voltage 0-20 VDC or 0-40 VDC,

respectively. Output current is 3A at 0-20 VDC, and 1.5A at

0-40 VDC.

D) Water electrolyzer:

Water electrolyzer shown in Figure 2 uses a cylindrical plastic

container with 40cm height, 12 cm diameter, and 2 liters of

water capacity. The used electrodes are made of stainless steel

316 shown in Figure 3. The two electrodes are flat plate

shape, each of them is 6cm height and 5cm width. The

thicknesses of each plate is 1.5 millimetres and the gap



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between the two plates is 5 millimetres. The flat plates

electrodes are separated by a non-electrical conducting

material which is resistive teflon.

The electrolyzer contains two electrodes, where each

electrode is connected to power supply. The electrodes are

immersed in water where the process of splitting water into

hydrogen and oxygen occurs when electrical current generated

by the pulse generator or the power supply is passed between

two electrodes.

E) Bubbler.

The bubbler is a cylindrical shape device which prevents the

reverse flow of hydrogen and oxygen; this is important for

safe operations.

F) The hydrogen and oxygen measurement instrument.

The hydrogen and oxygen measurement instrument is a

homemade instrument. The gas produced is collected inside a

cylindrical plastic container; 25cm height and 14cm diameter.

During production this plastic container is placed under water

surface, and it begins to rises above water surface as it is

being filled with hydrogen and oxygen gases.

Figure 2: Water electrolyzing cell Figure 3: Electrodes made of stainless Steel 316

EXPERIMENTATION AND RESULTS

This section includes the instrumentation used in the

experiments, the experimental work and setup, and the

experimental results.

Instrumentation.

In this work, different electronic measuring instruments are

used; but before being used they were tested and calibrated.

Calibrated thermocouple (type-K) coupled to a digital

thermometer is used to measure the water temperature inside

electrolyzer. The measurement range of this thermometer is

from -199.9 to 137 ℃ and its accuracy is + 1℃ .

Electric current which goes through a conductor is measured

using a clamp meter. The range of measurements is from 0 to

20 A. The accuracy of ammeter is + 3%.

To measure the electrical voltage, a 35 MHz analog

oscilloscope HM303-6 was used. TDS or total dissolved

solids in water, i.e. the concentration of dissolved solids in it,

is measured using TDS tester. The range of measurement of

this instrument is from 0 to 5000 ppm and its accuracy is

+2%. PH tester is used to measure the level of acidity and

alkalinity of the water. The range of measurement is from 0 to

14 PH. The resolution is 0.01 PH and the accuracy is + 0.01

PH.

Experimental work and setup.

At the beginning of each experiment, the electrolyzer is filled

with water and the electrodes are fully immersed in water. The

terminals of power supply are connected to the electrodes. In

the following sections, the experimentation is divided into two

parts. In the first part, a pulse generator and a power amplifier

are used to generate alternating current, with variable

amplitude, waveform and frequency, to operate the

electrolyzer, and in the second part a DC power supply is used

to generate different DC voltage values to operate the

electrolyzer.



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The effect of alternating current waveforms on hydrogen

and oxygen production.

The aim of this experiment is to study the effect of AC

voltage amplitude, waveform, and frequency on the hydrogen

and oxygen production using water electrolyzer.

In this experiment, the range of studied frequencies is from

5Hz to 60Hz with different waveforms as follows: sinusoidal,

sawtooth, and square, as shown in Figure 4.

Figure 4: Waveforms shapes

The procedure of experiment starts by producing certain

voltage amplitude from 5V to 30V with certain frequency

from 5Hz to 60 Hz, and certain waveform shape for 15

minutes; where the total hydrogen and oxygen production is

measured at the end of these 15 minutes. The measurement of

solution temperature inside electrolyzer is taken as the

average for three readings, first reading at the start of the first

minute, the second reading is taken after 7.5 minutes, and the

third reading is taken at the end of the 15th minute.

At the start of each experiment, the electrolyzer is filled with

2 Liters of water with 458 TDS and 7 PH. The current starts to

flow into the electrolyzer, where the reaction inside can be

seen, and the produced hydrogen and oxygen flow through a

pipe into the bubbler, then to the instrument used to measure

the production.

In the following, the effect of AC voltage amplitude,

waveform, and frequency on the hydrogen and oxygen

production is investigated:

A) Waveform effect: to compare the hydrogen and oxygen

production for different waveforms, the production gain is

calculated. For a certain frequency, production gain is

calculated based on the total hydrogen and oxygen production

for a range of voltage amplitudes as follows:

Production gain = 𝑝𝑝 − 𝑝𝑠

𝑝𝑠∗ 100%; Where:

𝑝𝑠: total hydrogen and oxygen production for the base case i.e.

when the waveform is sinusoidal.

𝑝𝑝: total hydrogen and oxygen production in case of sawtooth

or square waveforms.

The experimental results are presented in Figure 5, Figure 6,

and Figure 7. They show the production for different values of

frequencies. For each frequency value and for each waveform,

the gain is calculated by taking the total hydrogen and oxygen

production for voltage amplitudes from 5V to 30V. It is worth

mentioning that, experimentally, there is no production at

frequencies from 0 to 3Hz. From these figures, it can be seen

that the square waveform has the maximum hydrogen and

oxygen production followed by sawtooth waveform.

Therefore, using sinusoidal waveform as the base case, the

gain in total productivity can reach up to 489% for sawtooth

waveform, and up to 680% for the square waveform.



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Results of experimentation for different input voltage amplitudes and waveforms for 5Hz frequency




Figure 5: Results of experimentation for frequencies between 5Hz and 20Hz



3735








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The effect of input DC voltage values on hydrogen and

oxygen production

The aim of this experimental part is to study the effect of DC

voltage on the hydrogen and oxygen production using

electorlyzing cell, and to compare the results achieved in this

part to the results obtained using AC waveforms.



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The schematic diagram in this case is the same as in Figure 1,

but the pulse generator and power amplifier are replaced by a

DC power supply which is described in point C of section 2.

The experiment starts by applying certain DC voltage from

5V to 20V for 15 minutes; this range of voltages is limited by

the capabilities of the power supply. Measurements of the

different experimental variables which are: hydrogen and

oxygen production, solution temperature and DC current are

conducted as described before.

Figure 8 shows the results of experimentation for different

input DC voltages. From the analysis of Figure 8 it is seen that

the higher rates of hydrogen and oxygen production can be

obtained at higher input voltages. The experimental results

indicates that higher gain in total hydrogen and oxygen

production can be obtained by using DC input voltages

compared to the AC input voltages for the same range of

voltages. Again using sinusoidal waveform as the base case,

the gain in total productivity can reach up to 1100% for the

DC input voltage. It can be concluded that using DC input

voltage, such as the voltage produced by solar panels, in

operating the water electrolysis system enhances hydrogen

and oxygen productivity.

Figure 8: Experimental results for DC input voltages

CONCLUSIONS

In this work, a water electrolyzer, used to produce hydrogen

and oxygen gases, is designed and constructed. From the

experimental results, it can be seen that the square waveform

has the maximum hydrogen and oxygen production followed

by sawtooth waveform. Therefore, using sinusoidal waveform

as the base case, the gain in total productivity can reach up to

489% for sawtooth waveform, and up to 680% for the square

waveform.

For the range of AC voltages from 5V to 30V, there is no

indication that the increase in voltage would lead to increase

in productivity, and for the range of frequency from 5 to

60Hz, there is no indication that the increase in frequency

would lead to increase in productivity. But, it is noticed that

there are specific values of frequency and voltage where the

productivity is maximum.

Regarding the DC input voltage, the higher rates of hydrogen

and oxygen production can be obtained at higher input

voltages. In addition, higher rates of hydrogen and oxygen

production can be obtained by using DC voltage compared to

AC voltage. It is seen from the experimental results that the

gain in production of hydrogen and oxygen in case of DC

input voltage can reach up to 1100%.

ACKNOWLEDGEMENT

The authors are grateful to the Applied Science Private

University, Amman, Jordan for the full financial support

granted to this research.

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Documents

The Effect of Electrical Variables on Hydrogen and Oxygen ...electrode on the efficiency of water electrolysis at a particular concentration. Abdallah et al. investigated the effect