CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 1 of 17
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 1 of 17
`
`
`Exhibit 22
`Exhibit 22
`
`Page 1
`
`OWTEx. 2149
`Tennant Company v. OWT
`IPR2021-00625
`
`

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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 2 of 17
`
`International Journal of Green Energy, 3: 381–395, 2006
`Copyright © Taylor & Francis Group, LLC
`ISSN: 1543-5075 print / 1543-5083 online
`DOI: 10.1080/01971520600873343
`
`AN EXPERIMENTAL STUDY ON THE EFFECT OF
`ELECTROLYTIC CONCENTRATION ON THE RATE
`OF HYDROGEN PRODUCTION
`
`D. Buddhi
`Professor, Thermal Energy Storage Laboratory, School of Energy & Environmental
`Studies, Devi Ahilya University, Indore, India
`
`R. Kothari
`Senior Research Fellow, Ministry of Non-conventional Energy Sources (MNES),
`School of Energy & Environmental Studies, Devi Ahilya University, Indore, India
`
`R.L. Sawhney
`Professor & Head, School of Energy & Environmental Studies, Devi Ahilya
`University, Indore, India
`
`The effects of concentration of electrolytes on hydrogen production rate (HPR) at different
`applied voltages were experimentally evaluated in this research paper. The rate of hydrogen
`production was found to be directly proportional to the concentration of total dissolved sol-
`ids and the efficiency did not change much with the change in the concentration of solids.
`Sensitivity analysis of the electrolysis system was also carried out to understand the relative
`importance of concentration of total dissolved solids (TDS) on the HPR, which can help for
`an optimum design.
`
`Keywords: Electrolysis; Efficiency; Hydrogen production rate (HPR); Total dissolved
`solids (TDS); Sensitivity analysis
`
`INTRODUCTION
`
`Hydrogen is considered as potential alternative energy carrier and has all the
`desirable qualities to replace the fossil fuels. Hydrogen energy can be stored until it is
`needed and transported to where it is required. It does not occur naturally in large
`quantities on earth. It has to be separated from other compounds such as water or fos-
`sil fuels. Current technologies used for producing the hydrogen are steam methane
`reforming (SMR), coal gasification, biomass gasification and electrolysis (Nath,
`2003; Kothari, 2004).
`The production of hydrogen by the electrolysis of water is, in principle, very simple.
`Electrolysis works by passing direct current (DC) through an electrolyte. Tap water, a
`simple electrolyte, is slightly conductive because it contains a certain amount of minerals,
`
`Address correspondence to D. Buddhi, Thermal Energy Storage Laboratory, School of Energy and
`Environmental Studies, Devi Ahilya University, Indore, India 452017. E-mail: dbuddhi@hotmail.com
`
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 3 of 17
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`382
`
`D. BUDDHI, R. KOTHARI, AND R.L. SAWHNEY
`
`whereas distilled water is almost a perfect insulator. Electrodes are inserted into the
`electrolyte and one is attached to the positive source (anode) and the other is attached to
`the negative source (cathode). The most important characteristics of electrolysis process is
`not that hydrogen and other gases are split out from the water, but that they are separated
`at the same time. This benefit is derived at the expense of having to use a high “energy
`form”, namely electric power, as the input to the cell (Lipovestsky, 2004; Streigel, 2000).
`Ionic concentration in an electrolyte plays an important role in the process of electrolysis,
`and hence, in this paper, the effect of concentration of electrolytes on hydrogen production
`rate (HPR) and efficiency of hydrogen production at different applied voltages were
`experimentally evaluated.
`
`Principle of Electrolysis
`
`When a direct current is passed through water between two electrodes, water
`decomposes according to the reaction:
`
`→ +
`H O H
`2
`2
`
`1
`
`O
`
`2
`
`2
`
`(1)
`
`Water is actually a poor conductor of electricity and in order for this reaction to pro-
`ceed a conducting electrolyte must be added to the water. Water is essentially dissociated
`into hydrogen and hydroxyl ions (H+ and OH−). The positive hydrogen ions migrate
`toward the cathode, the negative electrode, where they are discharged by picking up elec-
`trons and forming hydrogen molecules:
`
`+ + →−
`2
`e
`
`2
`
`H
`
`H
`
`2
`
`(2)
`
`Both of these electrode reactions require some intermediate catalytic reaction with a
`metal surface. When an aqueous solution of an inorganic acid, such as sulfuric acid, or an
`alkali metal hydroxide, such as caustic soda or caustic potash, is submitted to the passage
`of a direct current through a pair of non-reactive electrode, so as to prevent any adverse
`side reactions, hydrogen and oxygen developed at the cathode and the anode, respectively
`in gaseous form (Casper, 1978).
`In an acid solution, where H+ ions are strongly predominant over OH− ions, the half-
`reactions that can be considered as the most likely at each electrode are the following
`(Riis, 2005):
`Cathodic half-reactions:
`
`+
`
`
`H aq)(
`
`−
`+ →
`2
`e
`
`2
`
`H
`
`2
`
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`Anodic half-reactions:
`
`2
`
`H O 1( )
`
`
`2
`
`
`
`→
`
`+
`+
`
`
`2
`
`( 4O g) H aq)(
`
`
`
`+
`
`−
`
`4
`
`e
`
`→ + 1
`Overall reaction:
`H O H
`O
`2
`2
`2
`2
`In alkaline solutions, where OH− ions strongly predominate, the following half-
`reaction mechanisms can explain the two electrode processes (Riis, 2005):
`
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`ELECTROLYTIC CONCENTRATION AND HYDROGEN PRODUCTION
`
`383
`
`Cathodic half-reaction:
`
`Anodic half-reaction:
`
`+
`
`−
`+ →
`4
`e
`
`4
`
`H
`
`
`
`2 2H
`
`4
`
`OH
`
`−
`
`→ +
`O
`2
`
`2
`
`H O
`2
`
`+
`
`−
`
`4
`
`e
`
`+
`2→
`2 H O
` H O
`Overall reaction:
`2
`2
`2
`It can thus be seen that, irrespective of the acidic or basic nature of the electrolyte,
`the ions into which it is dissociated will perform, under the conditions formerly
`assumed, the main function of carrying the electrolytic current, in that their presence in
`the aqueous medium improves its conductivity, without affecting the overall electrolysis
`process.
`It is believed that the hydrogen ions discharge on the metal surface to form an
`adsorbed layer of hydrogen atoms, which then recombine on the surface to form
`hydrogen molecules. The ease with which the electrode reactions occur is pro-
`foundly affected by both the physical and chemical natures of the surfaces of the
`electrodes.
`A basic electrolyzer cell consists of the following components: (i) Electrolyte,
`(ii) Electrode and (iii) Container. An electrolyte is a water solution made conductive by
`mixing a salt or compound with water. Selection of the electrolyte and electrodes are
`important. The desirable selective criteria for the electrolyte are:
`• It must exhibit high ionic conductivity;
`• It must not become chemically decomposed by voltage as large as that applied to the
`cell (so that only water is decomposed);
`• It must not be volatile enough to be removed with the evolved gas;
`• Because hydrogen-ion concentration is being rapidly perturbed at the electrodes, the
`electrolyte should have a strong resistance of pH changes, i.e., it should be a buffer
`solution.
`
`For the most practical applications, these criteria can be met by the use of a strong
`acid, such as sulfuric acid (H2SO4), or a strong alkali, such as potassium hydroxide
`(KOH). Most salts are themselves decomposed under electrolysis at voltages likely to be
`encountered in an electrolyzer cell. Acid electrolytes present severe corrosion problems
`and are not usually selected for electrolyzer. Therefore, most commercial electrolyzer
`operates with an alkaline electrolyte.
`Therefore, in this study we have selected the alkaline electrolytes for the production
`of hydrogen. NaCl and a mixture of NaCl & MgCl2 were used as conducting material in
`the distilled water. The concentration variation of 3.0 gm/l to 100.0 gm/l was taken for the
`study.
`Sensitivity analysis of the electrolysis system was also carried out to understand the
`relative importance of concentration of total dissolved solids and voltage on the HPR,
`which can help for an optimum design.
`The electrical conductivity of salts is generally determined by measuring the resis-
`tance of a sample between fixed metallic electrodes by a-c methods. The geometry of a
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 5 of 17
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`384
`
`D. BUDDHI, R. KOTHARI, AND R.L. SAWHNEY
`
`cell is determined indirectly by measuring the resistance of a reference liquid. The specific
`conductance can be calculated from the relation,
`
`
`R L kA)= /(
`which relates the specific conductance, k, (Ohm−1 cm-1) to the measured resistance of the
`cell, R, (ohms) and the cell geometry factors: L, the distance between electrodes (cm) and
`A, the effective cross section area of the electrodes (cm2). The specific conductance is the
`conductance (the reciprocal of the resistance) of the material between two electrodes with
`one sq cm. cross section separated by one cm.
`For comparisons of chemical properties and theoretical treatments, the equivalent
`conductance is considered to be of more fundamental significance. The equivalent con-
`ductance, Λ, (Ohm−1 sq cm equiv−1), is defined by the relation,
`
`Λ =
`
`kVe
`
`=
`
`k E(
`
`/ ρ)
`
`in which Ve is the volume of one gram equivalent of salt, ρ the density of the salt, and E
`the gram equivalent wt. of the salt. The equivalent conductance represents the conduc-
`tance of one equivalent of salt between electrodes one cm apart and of sufficient cross-
`section to include all the salt (Cilfford, 1976).
`The total dissolved solids present in various cations and anions forms in the indus-
`trial wastewater are sodium, magnesium, potassium, calcium, chloride, sulphate, phos-
`phate, nitrate etc., and the concentration varies between 3.0 gm/l to 100.0 gm/l. In this
`paper, the synthetic solutions were prepared and kept restricted to the NaCl and MgCl2,
`which have the equivalent conductance of 150 Ohm−1cm sq equivalent−1 and 35 Ohm−1cm sq
`equivalent−1 respectively.
`
`EXPERIMENTAL SET-UP
`
`A Hoffmann apparatus (Figure 1) was used for the electrolysis and gases produced
`at the cathode and anodes were collected by the displacement method. Each collecting
`tube was graduated downward from 0–50 ml in increment of 0.2 ml. The amount of elec-
`trolyte used for the study was 150 ml. Carbon electrode of area 21.6 cm2 was used and
`held in the lower ends of the gas collecting tubes by means of rubber stoppers, which fitted
`closely into the tapered lower ends of the tubes. The distance between electrodes was kept
`at 8.0 cm. The electrodes were connected to a D.C. power supply having a range of volt-
`age supply from 0.0 to 30.0 V with a resolution of 0.1 V and 1mA for voltage and current
`respectively. All the experiments were conducted in the months of April, May, June, July,
`August and September. The average room temperature during the course of experiments
`was 25°C to 30°C. The electronic balance used for the weighing of salts has the resolution
`of 1 mg.
`
`Preparation of Electrolytic Solutions
`
`The electrolytes of different concentrations were prepared using laboratory grade
`Magnesium chloride (MgCl2) and Sodium chloride (NaCl). These salts were procured
`from the Indian market.
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`
`ELECTROLYTIC CONCENTRATION AND HYDROGEN PRODUCTION
`
`385
`
`Figure 1 Hoffmann Voltammeter.
`
`Table 1 Composition of NaCl solutions used as electrolyte.
`
`Composition
`
`Concentration (gm/l) of solutions
`
`Na+
`Cl−
`Total Concentration (gm/l)
`
`1
`
`1.9
`3.1
`5.0
`
`2
`
`3.9
`6.1
`10.0
`
`3
`
`7.9
`12.1
`20.0
`
`4
`
`11.8
`18.2
`30.0
`
`5
`
`15.7
`24.3
`40.0
`
`6
`
`19.7
`30.3
`50.0
`
`a) NaCl solution: The electrolytic solution was prepared using NaCl and distilled water.
`The concentrations of sodium chloride used were in the range of 5.0 gm/l to 50.0 gm/l.
`The composition of six solutions used is given in Table 1.
`
`The overall reaction for the electrolytic production of hydrogen in the presence of electri-
`cal energy is:
`
`2
`
`H O
`2
`
`+
`
`2
`
`NaCl
`
`→ +
`H Cl
`2
`
`2
`
`+
`
`2
`
` NaOH
`
`(3)
`
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 7 of 17
`
`386
`
`D. BUDDHI, R. KOTHARI, AND R.L. SAWHNEY
`
`Table 2 Composition of NaCl + MgCl2 solutions used as electrolyte.
`
`Composition
`
`Concentration (gm/l) of solutions
`
`Na+
`Mg+2
`Cl−
`Total Concentration (gm/l)
`
`1
`
`0.6
`0.4
`2.0
`3.0
`
`2
`
`0.9
`0.6
`3.5
`5.0
`
`3
`
`1.9
`1.3
`6.8
`10.0
`
`4
`
`3.9
`2.6
`13.5
`20.0
`
`5
`
`7.9
`5.1
`27.0
`40.0
`
`6
`
`11.8
`7.7
`40.5
`60.0
`
`7
`
`15.7
`10.2
`54.1
`80.0
`
`8
`
`19.7
`12.7
`67.6
`100.0
`
`b) NaCl + MgCl2 solution: The solutions used were prepared using NaCl & MgCl2 with
`deionized water. These simulated compositions of electrolytes were chosen to cover
`the wide range of industrial wastewater. Electrolytic concentrations were considered in
`the range of 3.0 gm/l to 100.0 gm/l. The composition of eight solutions used is given in
`Table 2. The overall reaction for this electrolyte is as follows:
`
`+
`+
`H O NaCl MgCl
`2
`
`2
`
`→ +
`+
`+
`
`2
`2
`
`H Cl NaOH Mg OH)(
`
`2
`
`(4)
`
`The above two types of electrolytes prepared with NaCl and with a mixture of NaCl &
`MgCl2 were referred to as single salt electrolyte (SSE) and double salt electrolyte (DSE)
`respectively later.
`Alkaline water electrolysis is the technology used in present practice for large- scale
`electrolytic hydrogen production. Low efficiency, low current density and a lack of proper
`scale-up practice are the primary drawbacks of the present technology. Alkaline water
`electrolysis uses fresh water with low salt content, and hence additional treatment and
`desalination systems add to the cost of hydrogen produced.
`It is towards this objective that the current research is directed to consider saline
`water in the range of 2.4 gm/l to 93.5 gm/l total dissolved solid (TDS) to be electrolyzed
`for hydrogen production.
`The volume of hydrogen produced at the cathode and the other gases at the anode
`were obtained. The effect of different concentration of the electrolyte on the rate of hydro-
`gen production and the average quantity of hydrogen produced per hour was calculated at
`room temperature for all the electrolytic solutions. The purity of hydrogen gas produced
`was analyzed by checking the thermal conductivity of gas, which was found to be 0.189
`W/mK (Actual thermal conductivity of H2 gas is 0.1897 W/mK) by using the thermal con-
`ductivity detector (Model THERM 2227–2, ALHBORN) at room temperature with a reso-
`lution of 0.002 W/mK.
`
`Electrolysis Efficiency
`
`The efficiency of electrolysis can be defined as the ratio of chemical energy of
`hydrogen produced to the electrical energy input the for electrolysis process. Electrolysis
`efficiency (η) of the experiments were calculated by using the following equation:
`
`
`
`η = m h.
`
`/
`
`V.I
`
`RP
`
`(5)
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`
`ELECTROLYTIC CONCENTRATION AND HYDROGEN PRODUCTION
`
`387
`
`where η is the efficiency (%), m is the mass flow rate of hydrogen (kg/sec), hRP is the
`enthalpy of combustion of hydrogen (J/kg), V is the applied voltage (Volt), and I is the
`current (A).
`
`SENSITIVITY ANALYSIS
`
`As the performance of the electrolysis in terms of HPR depends on ionic concentra-
`tion (C) as an input parameter, it is often useful to know the relative importance in the
`change in ionic concentration in determining the performance of the system. This allows
`one to concentrate on the parameter range having larger influence on the performance of
`the system. Mathematically,
`
`HPR
`
`= ( )
`f C
`
`or,
`
`
`Y
`
`= ( )
`f xi
`
`(6)
`
`±
`→ ±
`, then
`If the independent variable xi is changed by
`
` U x )i.e. x(
`
`x U x(
`),
`1
`i
`i
`i
`the dependent variable, Y is consequently changed by some amount U[Y]. The change in
`dependent variable Y is then related to the change in dependent variable xi by
`= ∂
`
`
`
`U Y[
`
`]
`
`Y
`
`∂
`
`i
`
`[
`x U x
`
`i
`
`]
`
`(7)
`
`It is often useful to express the change in any variable as a fraction or equivalently, a
`percentage, that is
`
`
`
`U Y U Y Y% = [ ] /
`
`
`
`The relation (6) can then be written as
`
`
`
`U Y[
`
`]
`
`=
`
`Y
`
`or
`
`x
`i
`
`Y
`
`[%
`U Y
`
`⋅ ∂
`
`Y
`
`=
`
`]
`
`]
`
`[
`U x
`i
`
`∂ ⋅
`x
`x
`[ ,
`] %[
`I y x U x
`i
`i
`
`(8)
`
`(9)
`
`]
`
`where the influence coefficient
`i.e.,
`
`[
`,
`l Y xi
`
`]
`
` is the logarithmic derivative of Y with respect to xi
`
`(10)
`
`∂∂
`
`[ln ]
`[ln ]
`i
`
`Y x
`
`=
`
`∂∂
`
`/ /
`
`Y Y
`x
`x
`i
`i
`
`l y x[ ,
`
`
`i
`
`]
`
`=
`
`The influence coefficient is the measure of the sensitivity of the dependent variable
`n=
`Y and for the relation of the form
` is equal to the value of the exponent n, i.e.,
`,
`Y xi
`
`l Y x,[
`
`
`i
`
`]=
`
`n
`
`equal to-1
`equal to +1 means a proportional relationship and
`Obviously
`[
`,
`]
`[
`,
`]
`l Y xi
`l Y xi
`means an inverse relationship.
`equal to 0 of course implies no relationship. The
`[
`,
`]
`l Y xi
`value of
` thus calculated is a “local” one, meaning that for a different set of parame-
`[
`,
`]
`l Y xi
`ters, the numerical value of
` might be different. Further, if a maximum or minimum
`[
`,
`]
`l Y xi
`
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`
`388
`
`D. BUDDHI, R. KOTHARI, AND R.L. SAWHNEY
`
`is necessarily zero. This also
`in Y has been found for a value of xi = xi0, then
`[
`,
`]
`l Y xi
`implies the greatest care in determining the uncertainties of the independent variable
`should be employed for those variables that have the largest influence coefficients at the
`condition of interest because these particular variables can contribute the largest uncer-
`tainty in the dependent variable Y.
`
`Numerical Determination of the Percentage Change in the Dependent
`Variable (U)
`
`For the very complex nature of the expression of HPR, it is easier to determine the influ-
`ence coefficient and percentage change in the HPR numerically then analytically. A logical
`procedure would arrange the independent variable in such a way to make it possible to vary
`each xi by a small fraction ∈, i.e., change in xi to xi (1 ± ∈) and determine the percentage
`change in the dependent variable Y. The influence coefficient and the percentage change in the
`dependent variable Y can be numerically estimated from the relations
`
`(11)
`
`(12)
`
`∈ −
`+
`)]
`
`Y x[
`
`(1
`i
`∈
`+
`/
`
`
`Y x[
`(1
`i
`
`]
`
`Y x[
`
`i
`2
`)]
`
`/
`
`2
`
`)
`
`⋅
`
`∈∈
`
`+
`(1
`
`
`
`l y x[ ,
`
`
`i
`
`] =
`
`]
`
`Y x[
`
`i
`2
`)]
`
`*
`
`100
`
`∈ +
`
`−
`)]
`∈
`/
`
`+
`
`Y x[
`
`(1
`i
`
`
`Y x[
`(1
`i
`
`and
`
`
`
`U Y%[
`
`]
`
`= +
`
`(1
`
`∈
`
`/
`
`2
`
`)
`
`⋅
`
`where square brackets denote a functional relationship and the parenthesis forms an alge-
`braic group.
`The percentage variation in parameter, C has been numerically estimated. HPR in
`equation 6 has been estimated by using the linear regression equation 13 to be developed
`experimentally from Tables 3 and 4.
`
`Table 3 Correlation of hydrogen production with
`total dissolved solids with single salt electrolyte.
`
`Voltage (V)
`
`6.0
`9.0
`12.0
`
`a
`
`0.169
`0.441
`0.619
`
`b
`
`0.346
`0.136
`3.28
`
`Table 4 Correlation of hydrogen production with
`total dissolved solids with double salt electrolyte.
`
`Voltage (V)
`
`6.0
`9.0
`12.0
`
`a
`
`0.225
`0.349
`0.457
`
`b
`−0.605
`1.45
`3.85
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 10 of 17
`
`ELECTROLYTIC CONCENTRATION AND HYDROGEN PRODUCTION
`
`389
`
`RESULTS & DISCUSSION
`
`Prepared synthetic electrolytic solutions of different concentrations varying between 3.0
`to 100.0 gm/l were electrolyzed under potentiostatic conditions in the range of 6.0 ± 0.1V, 9.0
`± 0.1V & 12.0 ± 0.1V at room temperature of about 30 °C. The hydrogen and chlorine gases
`were collected at cathode and anode separately and the efficiencies of electrolysis process were
`calculated using equation 5.
`
`Experimental Analysis of Single Salt Electrolyte (SSE)
`
`HPR and efficiencies of SSE at different voltages (6.0, 9.0 & 12.0 V) with various
`TDS concentrations (4.6 to 42.4 gm/l) are tabulated in Table 5 and plotted in Figures 2 and 3
`respectively.
`It can be seen from Figure 2 that the HPR increases with the increase in TDS and
`voltage. On the other hand, Figure 3 shows that the rate of increase in the electrolysis effi-
`ciency is not significant with the increase in TDS and had decreased as the input voltage
`increased from 6.0 V to 12.0 V. It can also be seen from Table 3 that when input voltage
`was doubled from 6.0 V to 12.0 V, the HPR was increased about 4.5 times that of 6.0 V.
`The highest values of HPR obtained were 8.1, 19.1 & 30.0 ml/hr at highest concentration
`of 42.4 gm/l of the used electrolyte. This is attributed to the increase in the conductivity of
`the electrolytic solution.
`
`Experimental Analysis of Double Salt Electrolyte (DSE)
`
`HPR and efficiency of DSE at different voltages (6.0, 9.0 & 12.0 V) with various
`TDS concentrations (2.4 to 93.5 gm/l) are tabulated in Table 6 and plotted in Figures 4 and 5
`respectively.
`It can be seen from Figure 4 that the HPR increases with the increase in TDS and
`voltage. The highest value of HPR is 21.1, 33.3 & 46.0 ml/hr at 6.0, 9.0 and 12.0 V respec-
`tively with 93.5 gm/l TDS concentration. This is attributed to the increase in conductivity
`of the salt.
`
`Table 5 Hydrogen production rate & Electrolysis efficiency with single salt electrolyte concentrations at various
`DC supply voltages.
`
`TDS (gm/l)
`
`Input voltage 6.0 V
`η (%)
`
`HPR (ml/hr)
`
`Input voltage 9.0 V
`η (%)
`
`HPR (ml/hr)
`
`Input voltage 12.0 V
`η (%)
`
`HPR (ml/hr)
`
`4.6
`9.8
`19.3
`28.8
`36.7
`42.4
`
`1.4
`2.1
`3.4
`4.7
`6.4
`8.1
`
`10.8
`11.5
`11.8
`12.0
`12.4
`12.7
`
`2.4
`4.5
`8.4
`12.5
`16.4
`19.1
`
`8.6
`9.1
`10.1
`10.7
`11.1
`11.1
`
`6.8
`9.4
`14.2
`20.8
`26.1
`30.0
`
`7.9
`8.2
`8.8
`9.2
`9.5
`9.8
`
`TDS is total dissolved solids.
`HPR is hydrogen production rate.
`η is the electrolysis efficiency.
`
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`
`390
`
`D. BUDDHI, R. KOTHARI, AND R.L. SAWHNEY
`
`6V
`
`9V
`
`12V
`
`y = 0.618x + 3.28
`
`y = 0.441x + 0.136
`
`y = 0.169x + 0.346
`
`35
`
`30
`
`25
`
`20
`
`15
`
`10
`
`05
`
`Hydrogen Production Rate (ml/h)
`
`0
`
`10
`
`20
`
`30
`
`40
`
`50
`
`Total Dissolved Solids (gm/l)
`
`Figure 2 Variation of hydrogen production rate at different input voltages with single salt electrolytic
`concentration.
`
`0
`
`10
`
`20
`
`6V
`
`30
`
`9V
`
`12V
`
`40
`
`50
`
`Total Dissolved Solids (gm/l)
`
`14
`13
`12
`11
`10
`
`6789
`
`Efficiency (%)
`
`Figure 3 Effect of single salt electrolytic concentrations on the efficiency of hydrogen production rate at
`different input voltages.
`
`The highest efficiency is 29.6% and 17.8% at 6.0 V and 9.0 V respectively,
`with TDS concentration of 38.7 gm/l, and 11.8% at 12.0 V with 19.7 gm/l TDS
`shown in Figure 5. The efficiency is seen to increase up to 38.7 gm/l and then
`decreases with an increase in concentration at both 6.0 V and 9.0 V. The similar
`trend is seen at 12.0 V, but the optimum value of concentration up to which effi-
`ciency increases is 19.7 gm/l.
`
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 12 of 17
`
`ELECTROLYTIC CONCENTRATION AND HYDROGEN PRODUCTION
`
`391
`
`Table 6 Hydrogen production rate & Electrolysis efficiency with double salt electrolyte concentrations at
`various DC supply voltages.
`
`TDS (gm/l)
`
`Input voltage 6.0 V
`η (%)
`
`HPR (ml/hr)
`
`Input voltage 9.0 V
`η (%)
`
`HPR (ml/hr)
`
`Input voltage 12.0 V
`η (%)
`
`HPR (ml/hr)
`
`2.4
`4.6
`9.7
`19.7
`38.7
`57.8
`77.3
`93.5
`
`0.2
`0.6
`1.7
`3.6
`7.7
`11.9
`16.5
`21.1
`
`9.4
`15.8
`27.5
`29.2
`29.6
`27.8
`28.7
`28.3
`
`1.9
`2.7
`4.4
`8.8
`15.8
`22.1
`28.5
`33.3
`
`6.0
`10.8
`12.9
`16.7
`17.8
`16.9
`15.9
`15.7
`
`4.2
`5.7
`8.6
`13.6
`22.2
`30.8
`39.0
`46.0
`
`4.5
`8.9
`10.3
`11.8
`11.5
`11.3
`10.4
`10.9
`
`TDS is total dissolved solids.
`HPR is hydrogen production rate.
`η is the electrolysis efficiency.
`
`6.0 V
`
`9.0 V
`
`12.0 V
`
`y = 0.457x + 3.85
`
`y = 0.349x + 1.45
`
`y = 0.225x - 0.605
`
`20
`
`40
`
`60
`
`80
`
`100
`
`Total Dissolved Solids (gm/l)
`
`50
`
`40
`
`30
`
`20
`
`10
`
`0
`
`0
`
`-10
`
`Hydrogen Production Rate (ml/h)
`
`Figure 4 Variation of hydrogen production rate with double salt electrolytic concentration at different
`input voltages.
`
`It may be concluded that, as the voltage increases efficiency decreases and also
`becomes optimized with a certain range of concentration. This may be due to higher ionic
`conductivity in solution. The increase in salinity level gives a proportional increase in the
`hydrogen productivity. Hydrogen production rate (HPR) and total dissolved solids (TDS)
`are correlated in the form:
`
`= + *
`HPR b a TDS
`
`(13)
`
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 13 of 17
`
`392
`
`D. BUDDHI, R. KOTHARI, AND R.L. SAWHNEY
`
`3
`
`5
`
`10
`
`20
`
`40
`
`6V
`
`60
`
`9V
`
`80
`
`12V
`
`100
`
`Total Dissolved Solids (gm/l)
`
`35
`
`30
`
`25
`
`20
`
`15
`
`10
`
`05
`
`Efficiency (%)
`
`Figure 5 Effect of double salt electrolytic concentrations on the efficiency of hydrogen production rate at differ-
`ent input voltages.
`
`where HPR is in ml/hr and TDS is in gm/l. The values of a and b for different voltages and
`for different electrolytes are given in Tables 3 and 4 respectively.
`
`Sensitivity Analysis
`
`The variations of percentage change in the ionic concentration on HPR at dif-
`ferent input voltages are plotted in Figures 6 (a, b & c) and 7 (a, b & c). It is seen
`from the set of figures that HPR increases with an increase in ionic concentration
`of the DSE and the increase is minutely higher for a higher value of the ionic con-
`centration. An increase of 10% of ionic concentration increases HPR by about 2%
`to 10%. In the case of SSE the change in HPR with 10% increase of ionic concen-
`tration is insignificant.
`
`CONCLUSIONS
`
`From the work presented here we can conclude that single salt electrolyte and dou-
`ble salt electrolyte both show the direct relation of voltage with HPR, but efficiency
`shows an inverse relation with voltage with both electrolytes. The inverse relation
`between voltage and efficiency is due to the resistance of electrolyte concentration and
`changes in the voltage of electrodes due to concentration polarization, i.e., changes in the
`concentration of hydrogen ions, chloride ions or water by changing the electrolyte con-
`centration. From the sensitivity analysis, it can be concluded that the 10% increase of
`ionic concentration with single salt electrolyte is insignificant in comparison to the dou-
`ble salt electrolyte.
`
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 14 of 17
`
`ELECTROLYTIC CONCENTRATION AND HYDROGEN PRODUCTION
`
`393
`
`U
`-10
`
`-5
`
`U
`-10
`
`-5
`
`1.00E-01
`
`5.00E-02
`
`0
`
`0.00E+00
`
`-5.00E-02
`
`-1.00E-01
`
`P(N)
`
`(a)
`
`3.00E-01
`2.00E-01
`1.00E-01
`0.00E+00
`-1.00E-01
`-2.00E-01
`-3.00E-01
`
`0
`
`P(N)
`
` (b)
`
`5
`
`10
`
`5
`
`10
`
`U
`-10
`
`-5
`
`6.00E-02
`4.00E-02
`2.00E-02
`0.00E+00
`-2.00E-02
`-4.00E-02
`-6.00E-02
`
`0
`
`5
`
`10
`
`P(N)
`
` (c)
`
`U(4.6)
`U(9.8)
`U(19.3)
`U(28.8)
`U(36.7)
`U(42.4)
`
`U(4.6)
`U(9.8)
`U(19.3)
`U(28.8)
`U(36.7)
`U(42.4)
`
`U(4.6)
`U(9.8)
`U(19.3)
`U(28.8)
`U(36.7)
`U(42.4)
`
`Figure 6 Percentage change in hydrogen production rate at different input voltages with SSE at (a) 6.0 V (b) 9.0 V
`and (c) 12.0 V input voltage.
`
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 15 of 17
`
`394
`
`D. BUDDHI, R. KOTHARI, AND R.L. SAWHNEY
`
`U(2.4)
`U(4.6)
`U(9.7)
`U(19.7)
`U(38.7)
`U(57.8)
`U(77.3)
`U(93.5)
`
`U(2.4)
`U(4.6)
`U(9.7)
`U(19.7)
`U(38.7)
`U(57.8)
`U(77.3)
`U(93.5)
`
`0
`
`5
`
`10
`
`15
`10
`
`05
`
`-5
`-10
`-15
`
`U
`-10
`
`-5
`
`P(N)
`
`(a)
`
`0
`
`5
`
`10
`
`15
`
`10
`
`05
`
`-5
`
`-10
`
`-15
`
`U
`
`-10
`
`-5
`
`P(N)
`
`(b)
`
`0
`
`5
`
`10
`
`U(2.4)
`U(4.6)
`U(9.7)
`U(19.7)
`U(38.7)
`U(57.8)
`U(77.3)
`U(93.5)
`
`15
`10
`
`05
`
`-5
`-10
`-15
`
`U
`
`-10
`
`-5
`
`P(N)
`(c)
`
`Figure 7 Percentage change in hydrogen production rate at different input voltages with DSE at (a) 6.0 V
`(b) 9.0V and (c) 12.0V input voltage.
`
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`CASE 0:20-cv-00358-ECT-HB Doc. 80-18 Filed 06/10/21 Page 16 of 17
`
`ELECTROLYTIC CONCENTRATION AND HYDROGEN PRODUCTION
`
`395
`
`ACKNOWLEDGEMENT
`
`The financial assistance as a Senior Research Fellowship (SRF) to Ms. Richa Kothari by the Minis-
`try of Non-Conventional Energy Sources (MNES), New Delhi, India under National Renewable
`Energy Fellowship is thankfully acknowledged.
`
`REFERENCES
`
`Casper, M.S. (1978). Hydrogen manufacture by electrolysis, thermal decomposition and unusual
`techniques. Noyes Data Corporation 112–118.
`Hampel, C.A., (1976). The encyclopedia of electrochemistry. New York: Reinheld Publishing
`Corporation.
`Kothari, R., Buddhi, D., Sawhney, R.L. (2004). Sources and technology for hydrogen production: a
`review. International Journal of Global Energy Issues (IJGEI) 21(1 & 2):154–178.
`Lipovestsky, V. (2004). Production of hydrogen, obtaining electric and thermal energy by water
`dissociation method. International Journal of Hydrogen Energy 29(14):1555–1558.
`Nath, K., Das, D. (2003). Hydrogen from biomass. Current Science 85(3):265–271.
`Riis, T., Hagen, E.F., Vie, P.J.S., Ulleberg, O. (2005). Hydrogen production-gaps and priorities.
`IEA-Hydrogen Implementing Agreement. March, 15.
`Streigel, G.J. (2000). Overview of program: focus on hydrogen production. National Energy Tech-
`nology Laboratory. Hydrogen Workshop. September 19.
`
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