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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Energy Res.</journal-id>
<journal-title>Frontiers in Energy Research</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Energy Res.</abbrev-journal-title>
<issn pub-type="epub">2296-598X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="publisher-id">875332</article-id>
<article-id pub-id-type="doi">10.3389/fenrg.2022.875332</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Energy Research</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Improving Parameter Estimation of Fuel Cell Using Honey Badger Optimization Algorithm</article-title>
<alt-title alt-title-type="left-running-head">Almodfer et al.</alt-title>
<alt-title alt-title-type="right-running-head">PEMFC Parameter Estimation using HBA</alt-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Almodfer</surname>
<given-names>Rolla</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Mudhsh</surname>
<given-names>Mohammed</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/1661787/overview"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Alshathri</surname>
<given-names>Samah</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="corresp" rid="c001">&#x2a;</xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Abualigah</surname>
<given-names>Laith</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/1661384/overview"/>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>Abd Elaziz</surname>
<given-names>Mohamed</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
<xref ref-type="aff" rid="aff7">
<sup>7</sup>
</xref>
<xref ref-type="corresp" rid="c001">&#x2a;</xref>
<uri xlink:href="https://loop.frontiersin.org/people/1660817/overview"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Shahzad</surname>
<given-names>Khurram</given-names>
</name>
<xref ref-type="aff" rid="aff8">
<sup>8</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/464564/overview"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Issa</surname>
<given-names>Mohamed</given-names>
</name>
<xref ref-type="aff" rid="aff9">
<sup>9</sup>
</xref>
<uri xlink:href="https://loop.frontiersin.org/people/1661966/overview"/>
</contrib>
</contrib-group>
<aff id="aff1">
<label>
<sup>1</sup>
</label>
<institution>School of Information Engineering</institution>, <institution>Henan Institute of Science and Technology</institution>, <addr-line>Xinxiang</addr-line>, <country>China</country>
</aff>
<aff id="aff2">
<label>
<sup>2</sup>
</label>
<institution>Department of Information Technology</institution>, <institution>College of Computer and Information Sciences</institution>, <institution>Princess Nourah bint Abdulrahman University</institution>, <addr-line>Riyadh</addr-line>, <country>Saudi Arabia</country>
</aff>
<aff id="aff3">
<label>
<sup>3</sup>
</label>
<institution>Faculty of Computer Sciences and Informatics</institution>, <institution>Amman Arab University</institution>, <addr-line>Amman</addr-line>, <country>Jordan</country>
</aff>
<aff id="aff4">
<label>
<sup>4</sup>
</label>
<institution>School of Computer Sciences</institution>, <institution>Universiti Sains Malaysia</institution>, <addr-line>George Town</addr-line>, <country>Malaysia</country>
</aff>
<aff id="aff5">
<label>
<sup>5</sup>
</label>
<institution>Faculty of Computer Science and Engineering</institution>, <institution>Galala University</institution>, <addr-line>Suez</addr-line>, <country>Egypt</country>
</aff>
<aff id="aff6">
<label>
<sup>6</sup>
</label>
<institution>Artificial Intelligence Research Center (AIRC)</institution>, <institution>Ajman University</institution>, <addr-line>Ajman</addr-line>, <country>United Arab Emirates</country>
</aff>
<aff id="aff7">
<label>
<sup>7</sup>
</label>
<institution>Department of Mathematics</institution>, <institution>Faculty of Science</institution>, <institution>Zagazig University</institution>, <addr-line>Zagazig</addr-line>, <country>Egypt</country>
</aff>
<aff id="aff8">
<label>
<sup>8</sup>
</label>
<institution>Key Laboratory of Land Surface Pattern and Simulation</institution>, <institution>Institute of Geographic Sciences and Natural ResourcesResearch</institution>, <institution>Chinese Academy of Sciences</institution>, <addr-line>Beijing</addr-line>, <country>China</country>
</aff>
<aff id="aff9">
<label>
<sup>9</sup>
</label>
<institution>Computer and Systems Department</institution>, <institution>Faculty of Engineering</institution>, <institution>Zagazig University</institution>, <addr-line>Zagazig</addr-line>, <country>Egypt</country>
</aff>
<author-notes>
<corresp id="c001">&#x2a;Correspondence: Mohamed Abd Elaziz, <email>abd_el_aziz_m@yahoo.com</email>; Samah Alshathri, <email>sealshathry@pnu.edu.sa</email>
</corresp>
<fn fn-type="other">
<p>This article was submitted to Sustainable Energy Systems and Policies, a section of the journal Frontiers in Energy Research</p>
</fn>
<fn fn-type="edited-by">
<p>
<bold>Edited by:</bold> <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/1534692/overview">Enzo Barberio Mariano</ext-link>, S&#xe3;o Paulo State University, Brazil</p>
</fn>
<fn fn-type="edited-by">
<p>
<bold>Reviewed by:</bold> <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/1683666/overview">Amin Valizadeh</ext-link>, Ferdowsi University of Mashhad, Iran</p>
<p>
<ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/1683713/overview">Reza Habibifar</ext-link>, University of Massachusetts Lowell, United States</p>
</fn>
</author-notes>
<pub-date pub-type="epub">
<day>27</day>
<month>05</month>
<year>2022</year>
</pub-date>
<pub-date pub-type="collection">
<year>2022</year>
</pub-date>
<volume>10</volume>
<elocation-id>875332</elocation-id>
<history>
<date date-type="received">
<day>14</day>
<month>02</month>
<year>2022</year>
</date>
<date date-type="accepted">
<day>12</day>
<month>04</month>
<year>2022</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#xa9; 2022 Almodfer, Mudhsh, Alshathri, Abualigah, Abd Elaziz, Shahzad and Issa.</copyright-statement>
<copyright-year>2022</copyright-year>
<copyright-holder>Almodfer, Mudhsh, Alshathri, Abualigah, Abd Elaziz, Shahzad and Issa</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/">
<p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p>
</license>
</permissions>
<abstract>
<p>In this study, we proposed an alternative method to determine the parameter of the proton exchange membrane fuel cell (PEMFC) since there are multiple variable quantities with diverse nonlinear characteristics included in the PEMFC design, which is specified correctly to ensure effective modeling. The distinctive model of FCs is critical in determining the effectiveness of the cells&#x2019; inquiry. The design of FC has a significant influence on the simulation research of such methods, which have been used in a variety of applications. The developed method depends on using the honey badger algorithm (HBA) as a new identification approach for identifying the parameters of the PEMFC. In the presented method, the minimal value of the sum square error (SSE) is applied to determine the optimal fitness function. A set of experimental series has been conducted utilizing three datasets entitled 250-W stack, BCS 500-W, and NedStack PS6 to justify the usage of the HBA to determine the PEMFC&#x2019;s parameters. The results of the competitive algorithms are assessed using SSE and standard deviation metrics after numerous independent runs. The findings revealed that the presented approach produced promising results and outperformed the other comparison approaches.</p>
</abstract>
<kwd-group>
<kwd>parameter extracting</kwd>
<kwd>fuel cells</kwd>
<kwd>optimization</kwd>
<kwd>proton exchange membrane fuel cell</kwd>
<kwd>honey badger optimization algorithm</kwd>
</kwd-group>
</article-meta>
</front>
<body>
<sec id="s1">
<title>1 Introduction</title>
<p>The technology of the fuel cell (FC) is an essential energy exporter due to its extraordinary production and reduced carbon effects. Also, in contrast to wind and photovoltaic power origins, the production of power from the FC is autonomous of the climatologic conditions. Thus, it can be used for perpetual power generation. Different models of the FC are revealed; their system is carried out based on the characteristics of the electrolyte applied. Among the numerous types of FCs are the chemical-based FC approach (CFC) (<xref ref-type="bibr" rid="B31">McLean et al., 2002</xref>), PEMFC (<xref ref-type="bibr" rid="B7">Eisman, 1989</xref>), solid-based oxide FC (SOFC) (<xref ref-type="bibr" rid="B29">Kawada et al., 1990</xref>), etc. One of the most well-known types of FCs is the PEMFC. Their active start is recognized because of their economic temperature and yield ranging between 30 and 60%. The PEMFCs are utilized in different disciplines (<xref ref-type="bibr" rid="B5">Messaoud et al., 2021</xref>). The escalating cost of human energy has a hazardous impression on the atmosphere. Electricity requirements contribute primarily to ecological degeneration while consuming nonrenewable supplies (<xref ref-type="bibr" rid="B35">Nain et al., 2021</xref>). The portion of renewable electricity from the universal energy production is 26% approximately. Various varieties of power references for providing hydrogen exist. Now, most of the hydrogen composition is generated by solar power (37%) and comes behind conventional fossil fuel (26%), as shown in <xref ref-type="fig" rid="F1">Figure 1</xref> (<xref ref-type="bibr" rid="B10">Fathy et al., 2020b</xref>). These H2 results guide to reasonable prices and more critical appropriate solutions via hydrogen in the real world (<xref ref-type="bibr" rid="B30">Kayfeci et al., 2019</xref>).</p>
<fig id="F1" position="float">
<label>FIGURE 1</label>
<caption>
<p>PEMFC arrangement (<xref ref-type="bibr" rid="B8">Famouri and Gemmen, 2003</xref>).</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g001.tif"/>
</fig>
<p>FC-based energy production methods can meet the anticipations of very low emanations and comparatively high conductivity (<xref ref-type="bibr" rid="B34">Mo et al., 2006</xref>). FC is characterized by more economical contamination and more extraordinary performance than traditional power origins; however, they have an excellent dynamic reaction, sound balance, and moderate noise (<xref ref-type="bibr" rid="B37">Ramos-Paja et al., 2010</xref>). Between several systems of FCs, because of their approximately low running temperature, quick reaction, small volume, high popular mass, no loss, and in case of explicit hydrogen zero emission is generated, PEMFC can be an excellent option for energy-producing origins in the future, particularly in the automation applications, shared power production, and transferable photoelectric applicability (<xref ref-type="bibr" rid="B4">Askarzadeh and Rezazadeh, 2011</xref>).</p>
<p>Despite substantial advancements in the previous few years, the financial performance of PEMFCs is still a point of contention among support and opposition (<xref ref-type="bibr" rid="B3">Alizadeh and Torabi, 2021</xref>). The improvement of PEMFC performance is critical for the marketing of the technology and achieving significant market adoption (<xref ref-type="bibr" rid="B27">Kahraman and Orhan, 2017</xref>). Generally, the performance of the FC is regarded as the essential aspect of end-user acceptability (J. <xref ref-type="bibr" rid="B40">Wang et al., 2018</xref>). Many published articles show that numerous structural and operational factors (parameters) highly influence the performance of the PEMFC. The most efficient methods that have successfully proved their ability to extract the parameters are the optimization methods (<xref ref-type="bibr" rid="B6">Eid et al., 2021</xref>; <xref ref-type="bibr" rid="B13">Hassan et al., 2021</xref>; <xref ref-type="bibr" rid="B41">Wang et al., 2021</xref>). This field still needs further investigation to find a more efficient approach to tackle this problem.</p>
<p>As presented in the relevant studies, <xref ref-type="bibr" rid="B36">Priya et al. (2015)</xref> presented a unique presentation for the efficient estimation of FC parameters. The parameters&#x2019; values of FC were determined based on the genetic algorithm, and the obtained results proved its ability to find better results than several other methods in this domain. <xref ref-type="bibr" rid="B15">&#x130;nci and Caliskan (2020)</xref> proposed a new enhanced energy extraction-based optimization method to tackle the FC parameters. The presented technique is based on using an improved cuckoo optimizer. The proposed technique achieved better convergence acceleration than traditional techniques. <xref ref-type="bibr" rid="B28">Kandidayeni et al. (2019)</xref> used several optimization techniques to solve PEMFC. The proposed method reduced squared errors among the included and measured voltage for two possible test cases. The proposed SFLA method got better results in terms of precision and repeatability than the other comparative methods.</p>
<p>
<xref ref-type="bibr" rid="B9">Fathy et al.</xref> (<xref ref-type="bibr" rid="B9">2020a</xref>) introduced a hybrid of differential evolution and vortex search algorithms for determining the optimum parameters of the FC, called VSADE. The achieved results established the superiority of the introduced VSADE method. This study aimed to provide a new, simpler, and accurate model of the proton electrolyte membrane FC (<xref ref-type="bibr" rid="B39">Seleem et al., 2021</xref>). The suggested approach drastically lowers the number of unknown factors in such models, resulting in a more straightforward model. It discloses just four design factors within the model in this regard. This model&#x2019;s great effectiveness is tested both in steady-state and dynamic operating situations. It is possible to build a highly exact PEMFC model using the suggested approach. <xref ref-type="bibr" rid="B38">Menesy et al. (2020)</xref> suggested an enhanced artificial ecosystem optimizer to determine the problem of the FC parameters. According to the results, it is proved that the presented optimizer has high performance in obtaining the optimal parameters compared with the other comparative methods.</p>
<p>As mentioned before, metaheuristic optimization algorithms proved their ability to deal with various problems such as bioinformatics (<xref ref-type="bibr" rid="B17">Issa, 2021a</xref>; <xref ref-type="bibr" rid="B23">Issa and Abd Elaziz, 2020</xref>; <xref ref-type="bibr" rid="B24">Issa and Hassanien, 2017</xref>; <xref ref-type="bibr" rid="B19">Issa et al., 2018a</xref>; <xref ref-type="bibr" rid="B20">Issa et al., 2018b</xref>; <xref ref-type="bibr" rid="B25">Issa and Helmi, 2021</xref>; <xref ref-type="bibr" rid="B22">Issa et al., 2022</xref>), control engineering (<xref ref-type="bibr" rid="B18">Issa, 2021b</xref>; <xref ref-type="bibr" rid="B21">Issa et al., 2019</xref>), passive suspension system (<xref ref-type="bibr" rid="B26">Issa and Samn, 2022</xref>), and digital watermarking (<xref ref-type="bibr" rid="B1">Abualigah and Diabat, 2021</xref>; <xref ref-type="bibr" rid="B16">Issa, 2018</xref>). To estimate the model parameters of the PEMFC, an efficient method compared to the existing method is needed. This research work proposed a new parameter extraction technique to deal with the FC modeling optimization problem. The proposed method is based on the honey badger algorithm (HBA), a technique recently proposed by <xref ref-type="bibr" rid="B11">Hashim et al.(2021)</xref> inspired by the creative foraging habits of the honey badger in real life. The mathematical modeling of the HBA is produced using efficient search operators to deal with highly complicated problems which motivate to use it for the parameter estimation of PEMFCs. The balancing between diversification and intensification of the search space of the HBA is the main merit and motivation to use it in this work. The primary fitness function that is used in the proposed method is to minimize the integral squared errors. The high effectiveness of the presented technique is verified using dynamic and steady-state operating conditions. The results illustrated that the presented method using the HBA achieved promising results in comparison with several relevant study parameter extraction methods used in the literature.</p>
<p>The main contributions and novelties of this study are concluded as following:<list list-type="simple">
<list-item>
<p>1. The optimal values of the PEMFC model parameters were adjusted based on the HBA.</p>
</list-item>
<list-item>
<p>2. Three PEMFC datasets (NedStack PS6, 250&#xa0;W, and BCS 500&#xa0;W) were used in the experimental tests.</p>
</list-item>
<list-item>
<p>3. The results of the developed method were compared with well-known methods.</p>
</list-item>
</list>
</p>
<p>The remaining sections of this article are organized as follows: <xref ref-type="sec" rid="s2">Section 2</xref> proposes the background of the used optimization methods. <xref ref-type="sec" rid="s3">Section 3</xref> shows the procedure of the proposed FC parameter extraction using the honey badger algorithm. In <xref ref-type="sec" rid="s4">Section 4</xref>, experiments and results are given. Finally, <xref ref-type="sec" rid="s5">Section 5</xref> presents the conclusions and future potential works.</p>
</sec>
<sec id="s2">
<title>2 Background</title>
<p>In this part, the primary mathematical representation of the PEMFC design is explained. It includes a cathode, negative charges, charged anode, and electrolyte, as described in <xref ref-type="fig" rid="F1">Figure 1</xref>. In the PEMFC system, the hydrogen data are divided into two main parts utilizing a catalyst: protons and electrons. Moreover, the cathode pulls the protons, and the electrons produce the output charge by moving along the exterior circuit. The mathematical notations of the chemical stability produced in the FC are presented as follows (<xref ref-type="bibr" rid="B3">Alizadeh and Torabi, 2021</xref>):<disp-formula id="e1">
<mml:math id="m1">
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<mml:msub>
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<mml:math id="m3">
<mml:mrow>
<mml:msub>
<mml:mi>H</mml:mi>
<mml:mn>2</mml:mn>
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<mml:mo>&#x2b;</mml:mo>
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<mml:mi>O</mml:mi>
<mml:mn>2</mml:mn>
</mml:msub>
<mml:mo>&#x2192;</mml:mo>
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<mml:mi>H</mml:mi>
<mml:mn>2</mml:mn>
</mml:msub>
<mml:mi>O</mml:mi>
<mml:mo>&#x2b;</mml:mo>
<mml:mi>e</mml:mi>
<mml:mi>l</mml:mi>
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<mml:mi>y</mml:mi>
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<mml:mi>t</mml:mi>
<mml:mo>.</mml:mo>
</mml:mrow>
</mml:math>
<label>(3)</label>
</disp-formula>
</p>
<p>In the PEMFC system, three drops normally happen during the voltage process, called activation (V<sub>act</sub>), ohmic (V<sub>ohm</sub>), and concentration (V<sub>con</sub>). Thus, <xref ref-type="disp-formula" rid="e4">Eq. 4</xref> is used to calculate the FC terminal voltage.<disp-formula id="e4">
<mml:math id="m4">
<mml:mrow>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>E</mml:mi>
<mml:mrow>
<mml:mi>N</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>r</mml:mi>
<mml:mi>n</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>s</mml:mi>
<mml:mi>t</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>a</mml:mi>
<mml:mi>c</mml:mi>
<mml:mi>t</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>o</mml:mi>
<mml:mi>h</mml:mi>
<mml:mi>m</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>c</mml:mi>
<mml:mi>o</mml:mi>
<mml:mi>n</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(4)</label>
</disp-formula>where E<sub>Nernest</sub> is the double-faced open circuit charge voltage, which is calculated as follows (<xref ref-type="bibr" rid="B43">Yuan et al., 2020</xref>):<disp-formula id="e5">
<mml:math id="m5">
<mml:mrow>
<mml:msub>
<mml:mi>E</mml:mi>
<mml:mrow>
<mml:mi>N</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>r</mml:mi>
<mml:mi>n</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>s</mml:mi>
<mml:mi>t</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mi mathvariant="italic">1.229</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi mathvariant="italic">8.5</mml:mi>
<mml:mo>&#xd7;</mml:mo>
<mml:msup>
<mml:mrow>
<mml:mi mathvariant="italic">10</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>4</mml:mi>
</mml:mrow>
</mml:msup>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mi>T</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mi mathvariant="italic">298.15</mml:mi>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>&#x2b;</mml:mo>
<mml:mi mathvariant="italic">4.385</mml:mi>
<mml:mo>&#xd7;</mml:mo>
<mml:msup>
<mml:mrow>
<mml:mi mathvariant="italic">10</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>5</mml:mi>
</mml:mrow>
</mml:msup>
<mml:mi>T</mml:mi>
<mml:mo>&#x2061;</mml:mo>
<mml:mi mathvariant="italic">ln</mml:mi>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi>H</mml:mi>
<mml:mi>2</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2b;</mml:mo>
<mml:mi mathvariant="italic">0.5</mml:mi>
<mml:mo>&#x2061;</mml:mo>
<mml:mi mathvariant="italic">ln</mml:mi>
<mml:mo>&#x2061;</mml:mo>
<mml:msub>
<mml:mi>P</mml:mi>
<mml:mrow>
<mml:mi mathvariant="italic">O</mml:mi>
<mml:mi mathvariant="italic">2</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(5)</label>
</disp-formula>where RP<sub>O2</sub> presents the pressure of the O2, RP<sub>H2</sub> presents the pressure of H<sub>2</sub>, and T represents the cell temperature value used in this research. The activation voltage loss value (V<sub>act</sub>) is calculated as follows:<disp-formula id="e6">
<mml:math id="m6">
<mml:mrow>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>a</mml:mi>
<mml:mi>c</mml:mi>
<mml:mi>t</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mo>&#x2212;</mml:mo>
<mml:mrow>
<mml:mo>[</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3be;</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
<mml:mo>&#x2b;</mml:mo>
<mml:msub>
<mml:mi>&#x3be;</mml:mi>
<mml:mn>2</mml:mn>
</mml:msub>
<mml:mi>T</mml:mi>
<mml:mo>&#x2b;</mml:mo>
<mml:msub>
<mml:mi>&#x3be;</mml:mi>
<mml:mn>3</mml:mn>
</mml:msub>
<mml:mi>T</mml:mi>
<mml:mo>&#x2061;</mml:mo>
<mml:mi>ln</mml:mi>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>C</mml:mi>
<mml:mrow>
<mml:mn>02</mml:mn>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>&#x2b;</mml:mo>
<mml:mo>&#xa0;</mml:mo>
<mml:msub>
<mml:mi>&#x3be;</mml:mi>
<mml:mn>4</mml:mn>
</mml:msub>
<mml:mi>T</mml:mi>
<mml:mo>&#x2061;</mml:mo>
<mml:mi>ln</mml:mi>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mo>]</mml:mo>
</mml:mrow>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(6)</label>
</disp-formula>where I<sub>FC</sub> is the present value of the FC and &#x3be;<sub>1</sub>, &#x3be;<sub>2</sub>, &#x3be;<sub>3</sub>, and &#x3be;<sub>4</sub> denote the coefficient values. C<sub>O2</sub> presents the condensation value of oxygen (mol/cm<sup>3</sup>) calculated as follows:<disp-formula id="e7">
<mml:math id="m7">
<mml:mrow>
<mml:msub>
<mml:mtext>C</mml:mtext>
<mml:mrow>
<mml:mtext>O</mml:mtext>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mtext>P</mml:mtext>
<mml:mrow>
<mml:mtext>O</mml:mtext>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mrow>
<mml:msup>
<mml:mrow>
<mml:mn>5.08</mml:mn>
</mml:mrow>
<mml:mo>&#x2217;</mml:mo>
</mml:msup>
<mml:msup>
<mml:mrow>
<mml:mn>10</mml:mn>
</mml:mrow>
<mml:mrow>
<mml:mn>6</mml:mn>
<mml:mo>&#x2217;</mml:mo>
</mml:mrow>
</mml:msup>
<mml:msup>
<mml:mi>e</mml:mi>
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>498</mml:mn>
</mml:mrow>
<mml:mtext>T</mml:mtext>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:msup>
</mml:mrow>
</mml:mfrac>
<mml:mo>.</mml:mo>
</mml:mrow>
</mml:math>
<label>(7)</label>
</disp-formula>
</p>
<p>The V<sub>ohm</sub> is calculated using <xref ref-type="disp-formula" rid="e8">Eq. 8</xref>, which is resulted from the equivalent resistance of the FC value.<disp-formula id="e8">
<mml:math id="m8">
<mml:mrow>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>o</mml:mi>
<mml:mi>h</mml:mi>
<mml:mi>m</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>R</mml:mi>
<mml:mi>M</mml:mi>
</mml:msub>
<mml:mo>&#x2b;</mml:mo>
<mml:msub>
<mml:mi>R</mml:mi>
<mml:mi>C</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(8)</label>
</disp-formula>where R<sub>C</sub> presents the connection resistance and R<sub>M</sub> presents the membrane resistances calculated as follows:<disp-formula id="e9">
<mml:math id="m9">
<mml:mrow>
<mml:msub>
<mml:mi>R</mml:mi>
<mml:mi>M</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3c1;</mml:mi>
<mml:mi>M</mml:mi>
</mml:msub>
<mml:mo>.</mml:mo>
<mml:mi>l</mml:mi>
</mml:mrow>
<mml:mi>A</mml:mi>
</mml:mfrac>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(9)</label>
</disp-formula>
<disp-formula id="e10">
<mml:math id="m10">
<mml:mrow>
<mml:msub>
<mml:mi>&#x3c1;</mml:mi>
<mml:mi>M</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:mn>181.6</mml:mn>
<mml:mrow>
<mml:mo>[</mml:mo>
<mml:mrow>
<mml:mn>1</mml:mn>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>0.03</mml:mn>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mi>A</mml:mi>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>0.0062</mml:mn>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mi>T</mml:mi>
<mml:mrow>
<mml:mn>303</mml:mn>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:msup>
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mi>A</mml:mi>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mn>2.5</mml:mn>
</mml:mrow>
</mml:msup>
</mml:mrow>
<mml:mo>]</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:mrow>
<mml:mo>[</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>&#x3bb;</mml:mi>
<mml:mi>m</mml:mi>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>0.634</mml:mn>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>3</mml:mn>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mi>A</mml:mi>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mo>]</mml:mo>
</mml:mrow>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
<mml:mi>p</mml:mi>
<mml:mrow>
<mml:mo>[</mml:mo>
<mml:mrow>
<mml:mn>4.18</mml:mn>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi>T</mml:mi>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>303</mml:mn>
</mml:mrow>
<mml:mi>T</mml:mi>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mo>]</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:mfrac>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(10)</label>
</disp-formula>where <inline-formula id="inf1">
<mml:math id="m11">
<mml:mrow>
<mml:msub>
<mml:mi>&#x3c1;</mml:mi>
<mml:mi>M</mml:mi>
</mml:msub>
</mml:mrow>
</mml:math>
</inline-formula> presents the measure of the resisting power of the membrane (&#x2126;.cm), <italic>l</italic> presents the density value of the membrane (cm), <italic>A</italic> presents the effective range of the cell (cm<sup>2</sup>), and <inline-formula id="inf2">
<mml:math id="m12">
<mml:mrow>
<mml:msub>
<mml:mi>&#x3bb;</mml:mi>
<mml:mi>m</mml:mi>
</mml:msub>
</mml:mrow>
</mml:math>
</inline-formula> presents the membrane water fulfilled. The V<sub>con</sub> value is calculated using <xref ref-type="disp-formula" rid="e11">Eq. 11</xref>.<disp-formula id="e11">
<mml:math id="m13">
<mml:mrow>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>c</mml:mi>
<mml:mi>o</mml:mi>
<mml:mi>n</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>b</mml:mi>
<mml:mo>&#x2061;</mml:mo>
<mml:mi>ln</mml:mi>
<mml:mrow>
<mml:mo>{</mml:mo>
<mml:mrow>
<mml:mn>1</mml:mn>
<mml:mo>&#x2212;</mml:mo>
<mml:mfrac>
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mi>A</mml:mi>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>m</mml:mi>
<mml:mi>a</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
<mml:mo>}</mml:mo>
</mml:mrow>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(11)</label>
</disp-formula>where <inline-formula id="inf3">
<mml:math id="m14">
<mml:mi>b</mml:mi>
</mml:math>
</inline-formula> presents a constant value and <inline-formula id="inf4">
<mml:math id="m15">
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mrow>
<mml:mi>m</mml:mi>
<mml:mi>a</mml:mi>
<mml:mi>x</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
</mml:math>
</inline-formula> is the present maximum destiny value. So, the stack includes a series value of <inline-formula id="inf5">
<mml:math id="m16">
<mml:mi>n</mml:mi>
</mml:math>
</inline-formula> FCs, and the stack voltage value is calculated as follows.<disp-formula id="e12">
<mml:math id="m17">
<mml:mrow>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mi>t</mml:mi>
<mml:mi>a</mml:mi>
<mml:mi>c</mml:mi>
<mml:mi>k</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo>.</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mi>C</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>n</mml:mi>
<mml:mo>.</mml:mo>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>E</mml:mi>
<mml:mrow>
<mml:mi>N</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>r</mml:mi>
<mml:mi>n</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>s</mml:mi>
<mml:mi>t</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>a</mml:mi>
<mml:mi>c</mml:mi>
<mml:mi>t</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>o</mml:mi>
<mml:mi>h</mml:mi>
<mml:mi>m</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>c</mml:mi>
<mml:mi>o</mml:mi>
<mml:mi>n</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>.</mml:mo>
</mml:mrow>
</mml:math>
<label>(12)</label>
</disp-formula>
</p>
<p>
<xref ref-type="fig" rid="F2">Figure 2</xref> presents the FC polarization detour.</p>
<fig id="F2" position="float">
<label>FIGURE 2</label>
<caption>
<p>Polarization curve of the PEMFC system (<xref ref-type="bibr" rid="B8">Famouri and Gemmen, 2003</xref>) showing the regions dominated by activation loss, ohmic loss, and concentration loss using HBA.</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g002.tif"/>
</fig>
<sec id="s2-1">
<title>2.1 Honey Badger Algorithm</title>
<p>The HBA mimicked the locating of prey operation of the honey badger that lives in rainforests and semideserts of Southwest Asia, the Indian subcontinent, and Africa. For locating a prey, it depends on its smelling skills and moving.<list list-type="simple">
<list-item>
<p>- Digging phase: In this phase, the honey badger depends on its smelling sense for locating the prey and the suitable place to catch it.</p>
</list-item>
<list-item>
<p>- Honey phase: In this phase, the honey badger tracks the honey bird for locating the beehive.</p>
</list-item>
</list>
</p>
<p>The HBA starts with the initialization of the solutions within the lower boundary (<italic>lb</italic>) and upper boundary (<italic>ub</italic>) according to <xref ref-type="disp-formula" rid="e13">Eq. (13)</xref>.<disp-formula id="e13">
<mml:math id="m18">
<mml:mrow>
<mml:msup>
<mml:mi>x</mml:mi>
<mml:mi>i</mml:mi>
</mml:msup>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>l</mml:mi>
<mml:msub>
<mml:mi>b</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>&#x2b;</mml:mo>
<mml:msub>
<mml:mi>r</mml:mi>
<mml:mn>1</mml:mn>
</mml:msub>
<mml:mo>&#x2217;</mml:mo>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mi>u</mml:mi>
<mml:msub>
<mml:mi>b</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>l</mml:mi>
<mml:msub>
<mml:mi>b</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(13)</label>
</disp-formula>where (<italic>x</italic>
<sup>
<italic>i</italic>
</sup>) represents the solution of the honey badger agent (<italic>i</italic>) where (i &#x3d; 1:N) and (<italic>r</italic>
<sub>
<italic>1</italic>
</sub>) is a random number within (0,1). For balancing between the exploration and exploitation of the HBA, a density factor (<italic>&#x3b1;</italic>) is defined in <xref ref-type="disp-formula" rid="e14">Eq. (14)</xref>.<disp-formula id="e14">
<mml:math id="m19">
<mml:mrow>
<mml:mi>a</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:mi>C </mml:mi>
<mml:mo>&#x2217;</mml:mo>
<mml:mi> e</mml:mi>
<mml:mi>x</mml:mi>
<mml:msup>
<mml:mi>p</mml:mi>
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mfrac>
<mml:mi>t</mml:mi>
<mml:mi>T</mml:mi>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:msup>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(14)</label>
</disp-formula>where <italic>C</italic> represents a constant with a value more than (1), <italic>T</italic> represents the total number of iterations, and <italic>t</italic> represents the current iteration.</p>
<p>In the HBA, there are two phases for updating the movements of solutions.<list list-type="simple">
<list-item>
<p>- Digging phase: In this phase, the movements are updated according to a cardioid shape [2], which is represented in <xref ref-type="disp-formula" rid="e15">Eq. (15)</xref>.</p>
</list-item>
</list>
<disp-formula id="e15">
<mml:math id="m20">
<mml:mrow>
<mml:msup>
<mml:mi mathvariant="normal">x</mml:mi>
<mml:mrow>
<mml:mtext>new</mml:mtext>
</mml:mrow>
</mml:msup>
<mml:mo>&#x3d;</mml:mo>
<mml:msup>
<mml:mi mathvariant="normal">x</mml:mi>
<mml:mrow>
<mml:mtext>prey</mml:mtext>
</mml:mrow>
</mml:msup>
<mml:mo>&#x2b;</mml:mo>
<mml:mtext>F</mml:mtext>
<mml:mo>&#x2217;</mml:mo>
<mml:mtext>&#x3b2;</mml:mtext>
<mml:mo>&#x2217;</mml:mo>
<mml:mtext>l</mml:mtext>
<mml:mo>&#x2217;</mml:mo>
<mml:msup>
<mml:mi mathvariant="normal">x</mml:mi>
<mml:mrow>
<mml:mtext>prey</mml:mtext>
</mml:mrow>
</mml:msup>
<mml:mo>&#x2b;</mml:mo>
<mml:mtext>F</mml:mtext>
<mml:mo>&#x2217;</mml:mo>
<mml:mtext>&#x3b1;</mml:mtext>
<mml:mo>&#x2217;</mml:mo>
<mml:msup>
<mml:mtext>d</mml:mtext>
<mml:mi>i</mml:mi>
</mml:msup>
<mml:mo>&#x2217;</mml:mo>
<mml:msub>
<mml:mtext>r</mml:mtext>
<mml:mn>3</mml:mn>
</mml:msub>
<mml:mo>&#x2217;</mml:mo>
<mml:mrow>
<mml:mo>&#x7c;</mml:mo>
<mml:mrow>
<mml:mi>cos</mml:mi>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mn>2</mml:mn>
<mml:mtext>&#x3c0;</mml:mtext>
<mml:msub>
<mml:mtext>r</mml:mtext>
<mml:mn>4</mml:mn>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
<mml:mo>&#x2217;</mml:mo>
<mml:mrow>
<mml:mo>[</mml:mo>
<mml:mrow>
<mml:mn>1</mml:mn>
<mml:mo>&#x2212;</mml:mo>
<mml:mi>cos</mml:mi>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mn>2</mml:mn>
<mml:mtext>&#x3c0;</mml:mtext>
<mml:msub>
<mml:mtext>r</mml:mtext>
<mml:mn>5</mml:mn>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mo>]</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mo>&#x7c;</mml:mo>
</mml:mrow>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(15)</label>
</disp-formula>where <inline-formula id="inf6">
<mml:math id="m21">
<mml:mrow>
<mml:msup>
<mml:mtext>x</mml:mtext>
<mml:mrow>
<mml:mtext>new</mml:mtext>
</mml:mrow>
</mml:msup>
</mml:mrow>
</mml:math>
</inline-formula> is the new updated value of <italic>x</italic>
<sup>
<italic>i</italic>
</sup>; <italic>x</italic>
<sup>
<italic>prey</italic>
</sup> is the best-founded solution; (F) controls the direction of the search according to <xref ref-type="disp-formula" rid="e16">Eq. (16)</xref>; <italic>r</italic>
<sub>
<italic>3</italic>
</sub>, <italic>r</italic>
<sub>
<italic>4</italic>
</sub>
<italic>, r</italic>
<sub>
<italic>5</italic>
</sub>, and <italic>r</italic>
<sub>
<italic>6</italic>
</sub> are uniformly generated random numbers within the range (0,1); (<italic>B</italic>) is a constant number having a value greater than (1); and (<italic>I</italic>) is the smell intensity of the prey, which expresses the remoteness between the prey and the honey badger.</p>
<p>It was estimated according to <xref ref-type="disp-formula" rid="e17">Eq. (17</xref>) and <xref ref-type="disp-formula" rid="e18">(18</xref>), where (d<sub>i</sub>) represents the remoteness between the prey and the honey badger and (S) expresses the source strength.<disp-formula id="e16">
<mml:math id="m22">
<mml:mrow>
<mml:mi>F</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:mrow>
<mml:mo>{</mml:mo>
<mml:mrow>
<mml:mtable>
<mml:mtr>
<mml:mtd>
<mml:mn>1</mml:mn>
</mml:mtd>
<mml:mtd>
<mml:mrow>
<mml:mi>I</mml:mi>
<mml:mi>f</mml:mi>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>r</mml:mi>
<mml:mn>6</mml:mn>
</mml:msub>
<mml:mo>&#x2264;</mml:mo>
<mml:mn>0.5</mml:mn>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:mtd>
</mml:mtr>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:mo>&#x2212;</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:mtd>
<mml:mtd>
<mml:mrow>
<mml:mi>E</mml:mi>
<mml:mi>l</mml:mi>
<mml:mi>s</mml:mi>
<mml:mi>e</mml:mi>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mrow>
<mml:mo>&#xa0;</mml:mo>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(16)</label>
</disp-formula>
<disp-formula id="e17">
<mml:math id="m23">
<mml:mrow>
<mml:msub>
<mml:mi>I</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msub>
<mml:mi>r</mml:mi>
<mml:mn>2</mml:mn>
</mml:msub>
<mml:mo>&#xa0;</mml:mo>
<mml:mfrac>
<mml:mi>S</mml:mi>
<mml:mrow>
<mml:mn>4</mml:mn>
<mml:mo>&#xa0;</mml:mo>
<mml:mi>&#x3c0;</mml:mi>
<mml:msubsup>
<mml:mi>d</mml:mi>
<mml:mi>i</mml:mi>
<mml:mn>2</mml:mn>
</mml:msubsup>
</mml:mrow>
</mml:mfrac>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(17)</label>
</disp-formula>
<disp-formula id="e18">
<mml:math id="m24">
<mml:mrow>
<mml:mtable>
<mml:mtr>
<mml:mtd>
<mml:mrow>
<mml:mi>S</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:msup>
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msup>
<mml:mi>x</mml:mi>
<mml:mi>i</mml:mi>
</mml:msup>
<mml:mo>&#x2212;</mml:mo>
<mml:msup>
<mml:mi>x</mml:mi>
<mml:mrow>
<mml:mi>i</mml:mi>
<mml:mo>&#x2b;</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:msup>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:mtd>
<mml:mtd>
<mml:mrow>
<mml:msub>
<mml:mi>d</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>&#x3d;</mml:mo>
<mml:msup>
<mml:mi>x</mml:mi>
<mml:mrow>
<mml:mi>p</mml:mi>
<mml:mi>r</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>y</mml:mi>
</mml:mrow>
</mml:msup>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>x</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
</mml:mrow>
</mml:mtd>
</mml:mtr>
</mml:mtable>
<mml:mo>.</mml:mo>
</mml:mrow>
</mml:math>
<label>(18)</label>
</disp-formula>
<list list-type="simple">
<list-item>
<p>- Honey Phase: This phase simulates the tracking of the honey badger for the honey guide bird to find the beehive, and this operation is simulated as in <xref ref-type="disp-formula" rid="e19">Eq. (19)</xref>.</p>
</list-item>
</list>
<disp-formula id="e19">
<mml:math id="m25">
<mml:mrow>
<mml:msup>
<mml:mi>x</mml:mi>
<mml:mrow>
<mml:mi>n</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>w</mml:mi>
</mml:mrow>
</mml:msup>
<mml:mo>&#x3d;</mml:mo>
<mml:msup>
<mml:mi>x</mml:mi>
<mml:mrow>
<mml:mi>p</mml:mi>
<mml:mi>r</mml:mi>
<mml:mi>e</mml:mi>
<mml:mi>y</mml:mi>
</mml:mrow>
</mml:msup>
<mml:mo>&#x2b;</mml:mo>
<mml:mi>F </mml:mi>
<mml:mo>&#x2217;</mml:mo>
<mml:msub>
<mml:mi> r</mml:mi>
<mml:mn>7</mml:mn>
</mml:msub>
<mml:mo>&#x2217;</mml:mo>
<mml:mi> &#x3b1; </mml:mi>
<mml:mo>&#x2217;</mml:mo>
<mml:msub>
<mml:mi> d</mml:mi>
<mml:mi>i</mml:mi>
</mml:msub>
<mml:mo>,</mml:mo>
</mml:mrow>
</mml:math>
<label>(19)</label>
</disp-formula>where r<sub>7</sub> is a uniform random number within the range (0,1). The procedure of the HBA is expressed as in algorithm (1). <xref ref-type="fig" rid="F3">Figure 3</xref> shows the flowchart of HBA. HBA&#x2019;s time complexity is <italic>O</italic> (<italic>T x N x C</italic>
<sub>
<italic>cost</italic>
</sub>), where <italic>T</italic> is the total number of iterations, <italic>N</italic> represents the population size, and <italic>C</italic>
<sub>
<italic>cost</italic>
</sub> is the needed execution time for updating solutions.</p>
<fig id="F3" position="float">
<label>FIGURE 3</label>
<caption>
<p>Flowchart of HBA (<xref ref-type="bibr" rid="B12">Hashim et al., 2022</xref>).</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g003.tif"/>
</fig>
<p>
<statement content-type="algorithm" id="alg1">
<label>Algorithm 1</label>
<p>HBA procedure</p>
</statement>
</p>
<p>
<statement>
<p>
<inline-graphic xlink:href="fenrg-10-875332-fx1.tif"/>
</p>
<p>The balancing between diversification and intensification of the search space of the HBA is the main merit and motivation to use it in this work. The balancing is performed through three main parameters:<list list-type="simple">
<list-item>
<p>1 - Intensity <inline-formula id="inf7">
<mml:math id="m26">
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mi mathvariant="normal">I</mml:mi>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:math>
</inline-formula>
<bold>:</bold> It controls the transfer between exploration to exploitation and the reverse through the distance between the prey and the other solutions, which may be increased or decreased. In addition, there is another issue that controls the exploration/exploitation process that is the distance between two neighbors of solutions. These interactions increase the possibility of escaping from local minima.</p>
</list-item>
<list-item>
<p>2 - Density factor (&#x3b1;): This parameter decreases with time, which achieves the trade-off between diversification and intensification of the search space.</p>
</list-item>
<list-item>
<p>3 - Flag <inline-formula id="inf8">
<mml:math id="m27">
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mi mathvariant="normal">F</mml:mi>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:math>
</inline-formula>: It controls the direction of the movements of the solutions, which increase the diversity of the generated solutions, which enhance the exploration.</p>
</list-item>
</list>
</p>
</statement>
</p>
</sec>
</sec>
<sec id="s3">
<title>3 PEMFC Model Parameter Estimations Based on HBA</title>
<p>The HBA was used for tuning the best parameters&#x2019; values of PEMFCs where each agent has a total of the seven parameters (&#x3bb;, Rc, &#x3be;<sub>1</sub>, &#x3be;<sub>2</sub>, &#x3be;<sub>3</sub>, &#x3be;<sub>4</sub>, and b), and the best agent is the agent that produces the best fitness. The fitness function used to evaluate the search is the sum square error (SSE) function, which represents the integral square of the subtraction between experimental and estimated voltages. The representation of the SSE function as proposed in <xref ref-type="disp-formula" rid="e20">Eq. (20)</xref>, where Vexp and Vest represent the experimental and estimated voltages, respectively.<disp-formula id="e20">
<mml:math id="m28">
<mml:mrow>
<mml:mi>S</mml:mi>
<mml:mi>S</mml:mi>
<mml:mi>E</mml:mi>
<mml:mo>&#x3d;</mml:mo>
<mml:msup>
<mml:mrow>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>e</mml:mi>
<mml:mi>x</mml:mi>
<mml:mi>p</mml:mi>
</mml:mrow>
</mml:msub>
<mml:mo>&#x2212;</mml:mo>
<mml:msub>
<mml:mi>V</mml:mi>
<mml:mrow>
<mml:mi>e</mml:mi>
<mml:mi>s</mml:mi>
<mml:mi>t</mml:mi>
</mml:mrow>
</mml:msub>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
<mml:mn>2</mml:mn>
</mml:msup>
<mml:mo>.</mml:mo>
</mml:mrow>
</mml:math>
<label>(20)</label>
</disp-formula>
</p>
<p>
<xref ref-type="fig" rid="F4">Figure 4</xref> shows the flowchart of parameter estimation of PEMFCs based on the HBA. The initial random solutions are initialized according to satisfying conditions and input into the HBA&#x2019;s block. The output of the HBA is the best solution found that achieves the smallest SSE.</p>
<fig id="F4" position="float">
<label>FIGURE 4</label>
<caption>
<p>PEMFC model parameter estimation based on HBA.</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g004.tif"/>
</fig>
</sec>
<sec id="s4">
<title>4 Numerical Analysis</title>
<p>The efficiency of the created HBA used for estimating PEMFC model parameters is assessed in this part using three datasets: PEMFC 250-W stack, NedStack PS6, and BCS 500-W, and their electrical specification are listed in <xref ref-type="table" rid="T1">Table 1</xref>. In addition, <xref ref-type="table" rid="T2">Table 2</xref> presents the parameters&#x2019; boundaries (lower bound and higher bound) (<xref ref-type="bibr" rid="B44">Zhang and Liu, 2010</xref>).</p>
<table-wrap id="T1" position="float">
<label>TABLE 1</label>
<caption>
<p>PEMFC dataset&#x2019;s electrical specifications.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="left">Specification</th>
<th align="center">BCS 500-W [2]</th>
<th align="center">250-W [33], [34]</th>
<th align="center">PS6 [33]</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left">
<inline-formula id="inf9">
<mml:math id="m29">
<mml:mrow>
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<td align="char" char=".">32</td>
<td align="char" char=".">24</td>
<td align="char" char=".">65</td>
</tr>
<tr>
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<td align="char" char=".">178</td>
<td align="char" char=".">127</td>
<td align="char" char=".">178</td>
</tr>
<tr>
<td align="left">
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<td align="char" char=".">64</td>
<td align="char" char=".">27</td>
<td align="char" char=".">240</td>
</tr>
<tr>
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<mml:mi>A</mml:mi>
</mml:mrow>
<mml:mrow>
<mml:mi>c</mml:mi>
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<mml:mn>2</mml:mn>
</mml:msup>
</mml:mrow>
</mml:mfrac>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:math>
</inline-formula>
</td>
<td align="char" char=".">469</td>
<td align="char" char=".">860</td>
<td align="char" char=".">1125</td>
</tr>
<tr>
<td align="left">
<inline-formula id="inf13">
<mml:math id="m33">
<mml:mrow>
<mml:mi>T</mml:mi>
<mml:msub>
<mml:mi>M</mml:mi>
<mml:mi>c</mml:mi>
</mml:msub>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mi>K</mml:mi>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:math>
</inline-formula>
</td>
<td align="char" char=".">333</td>
<td align="char" char=".">343</td>
<td align="char" char=".">343</td>
</tr>
<tr>
<td align="left">
<inline-formula id="inf14">
<mml:math id="m34">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:msub>
<mml:mi>R</mml:mi>
<mml:mrow>
<mml:mi>H</mml:mi>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msub>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
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</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:math>
</inline-formula>
</td>
<td align="char" char=".">1</td>
<td align="char" char=".">1</td>
<td align="char" char=".">1</td>
</tr>
<tr>
<td align="left">
<inline-formula id="inf15">
<mml:math id="m35">
<mml:mrow>
<mml:mi>P</mml:mi>
<mml:msub>
<mml:mi>R</mml:mi>
<mml:mrow>
<mml:mi>O</mml:mi>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msub>
<mml:mrow>
<mml:mo>(</mml:mo>
<mml:mrow>
<mml:mi>a</mml:mi>
<mml:mi>t</mml:mi>
<mml:mi>m</mml:mi>
</mml:mrow>
<mml:mo>)</mml:mo>
</mml:mrow>
</mml:mrow>
</mml:math>
</inline-formula>
</td>
<td align="char" char=".">0.2095</td>
<td align="char" char=".">1</td>
<td align="char" char=".">1</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="T2" position="float">
<label>TABLE 2</label>
<caption>
<p>Two parameter ranges of PEMFC parameters.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="left">Parameter</th>
<th align="left">Lower limit</th>
<th align="left">Upper limit</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left">&#x3be;<sub>1</sub>
</td>
<td align="left">&#x2212;1.1997</td>
<td align="left">&#x2212;0.8532</td>
</tr>
<tr>
<td align="left">&#x3be;<sub>2</sub>
</td>
<td align="left">0.80E-3</td>
<td align="left">6.00E-3</td>
</tr>
<tr>
<td align="left">&#x3be;<sub>3</sub>
</td>
<td align="left">3.60E-5</td>
<td align="left">9.80E-5</td>
</tr>
<tr>
<td align="left">&#x3be;<sub>4</sub>
</td>
<td align="left">&#x2212;26.00E-5</td>
<td align="left">&#x2212;9.54E-5</td>
</tr>
<tr>
<td align="left">&#x3bb;</td>
<td align="left">13</td>
<td align="left">23</td>
</tr>
<tr>
<td align="left">R<sub>c</sub> (&#x3a9;)</td>
<td align="left">0.1E-3</td>
<td align="left">0.8E-3</td>
</tr>
<tr>
<td align="left">b (V)</td>
<td align="left">0.0136</td>
<td align="left">0.5000</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>The HBA is compared to other MH techniques such as grey wolf optimization (GWO) (<xref ref-type="bibr" rid="B2">Ali et al., 2017</xref>; <xref ref-type="bibr" rid="B32">Mirjalili et al., 2014</xref>), Hunger Games Search (HGS) (<xref ref-type="bibr" rid="B42">Yang et al., 2021</xref>), sine cosine algorithm (SCA) (<xref ref-type="bibr" rid="B33">Mirjalili, 2016</xref>), and Harris hawk optimization (HHO) (<xref ref-type="bibr" rid="B14">Heidari et al., 2019</xref>) to demonstrate its capability. The values of each algorithm&#x2019;s parameters are assigned depending on the algorithm&#x2019;s original implementation. The conventional settings for the number of populations and iterations are 50 and 500, respectively.</p>
<p>
<xref ref-type="table" rid="T3">Tables 3</xref>&#x2013;<xref ref-type="table" rid="T7">7</xref> and <xref ref-type="fig" rid="F5">Figures 5</xref>&#x2013;<xref ref-type="fig" rid="F9">9</xref> using the three datasets show the comparison between the HBA and other approaches. <xref ref-type="table" rid="T3">Table 3</xref> shows the estimated parameters derived by each algorithm and their SSE values in general. The performance of the HBA in terms of SSE is superior to other MH approaches among the datasets studied, as can be seen from these results. HBA&#x2019;s SSE value with BCS 500-W, 250-W, and NedStack PS6 is, for example, 0.0118, 0.3378, and 1.38E&#x2b;00, respectively.</p>
<table-wrap id="T3" position="float">
<label>TABLE 3</label>
<caption>
<p>Estimated BSC 500&#xa0;W&#x2019;s parameters.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="left"/>
<th align="center">HBA</th>
<th align="center">HGS</th>
<th align="center">HHO</th>
<th align="center">SCA</th>
<th align="center">GWO</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>1</bold>
</sub>
</td>
<td align="center">
<bold>&#x2212;0.952</bold>
</td>
<td align="center">
<bold>&#x2212;</bold>0.9510</td>
<td align="center">
<bold>&#x2212;</bold>1.093</td>
<td align="center">
<bold>&#x2212;</bold>0.947</td>
<td align="center">
<bold>&#x2212;</bold>0.948</td>
</tr>
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>2</bold>
</sub>
</td>
<td align="center">
<bold>3.2E-03</bold>
</td>
<td align="center">3.3E-03</td>
<td align="center">3.3E-03</td>
<td align="center">3.3E-03</td>
<td align="center">3.3E-03</td>
</tr>
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>3</bold>
</sub>
</td>
<td align="center">
<bold>7.40E-05</bold>
</td>
<td align="center">
<bold>&#x2212;</bold>9.2E-05</td>
<td align="center">
<bold>&#x2212;</bold>1.89E-04</td>
<td align="center">
<bold>&#x2212;</bold>7.1E-5</td>
<td align="center">
<bold>&#x2212;</bold>8.0E-5</td>
</tr>
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>4</bold>
</sub>
</td>
<td align="center">
<bold>&#x2212;7.24E-05</bold>
</td>
<td align="center">
<bold>&#x2212;</bold>9.21E-5</td>
<td align="center">
<bold>&#x2212;</bold>1.89E-4</td>
<td align="center">
<bold>&#x2212;</bold>7.1E-5</td>
<td align="center">
<bold>&#x2212;</bold>8.0E-5</td>
</tr>
<tr>
<td align="left">
<bold>&#x3bb;</bold>
</td>
<td align="center">
<bold>2.01E&#x2b;01</bold>
</td>
<td align="center">14.00</td>
<td align="center">2.00E&#x2b;01</td>
<td align="center">19.569</td>
<td align="center">18.599</td>
</tr>
<tr>
<td align="left">
<bold>Rc</bold>
</td>
<td align="center">
<bold>5.43E-04</bold>
</td>
<td align="center">1.4E-04</td>
<td align="center">2.26E-04</td>
<td align="center">4.1E-04</td>
<td align="center">3.2E-04</td>
</tr>
<tr>
<td align="left">
<bold>b</bold>
</td>
<td align="center">
<bold>1.60E-02</bold>
</td>
<td align="center">1.7E-02</td>
<td align="center">1.51E-02</td>
<td align="center">2.9E-02</td>
<td align="center">3.01E-2</td>
</tr>
<tr>
<td align="left">
<bold>SSE</bold>
</td>
<td align="center">
<bold>0.0118</bold>
</td>
<td align="center">2.113</td>
<td align="center">0.0149</td>
<td align="center">8.726</td>
<td align="center">1.918</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="T4" position="float">
<label>TABLE 4</label>
<caption>
<p>Estimated 250&#xa0;W&#x2019;s parameters.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="left">Parameter</th>
<th align="left">HBA</th>
<th align="left">HGS</th>
<th align="left">HHO</th>
<th align="left">SCA</th>
<th align="left">GWO</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left">&#x3be;<sub>1</sub>
</td>
<td align="left">&#x2212;0.9486</td>
<td align="left">&#x2212;0.945</td>
<td align="left">&#x2212;1.1097</td>
<td align="left">&#x2212;0.9487</td>
<td align="left">&#x2212;0.9478</td>
</tr>
<tr>
<td align="left">&#x3be;<sub>2</sub>
</td>
<td align="left">3.25E-03</td>
<td align="left">3.00E-03</td>
<td align="left">3.46E-03</td>
<td align="left">3.23E-3</td>
<td align="left">3.22E-3</td>
</tr>
<tr>
<td align="left">&#x3be;<sub>3</sub>
</td>
<td align="left">7.80E-5</td>
<td align="left">7.8E-05</td>
<td align="left">8.32E-05</td>
<td align="left">7.69E-5</td>
<td align="left">7.69E-5</td>
</tr>
<tr>
<td align="left">&#x3be;<sub>4</sub>
</td>
<td align="left">&#x2212;1.73E-4</td>
<td align="left">&#x2212;1.0E-04</td>
<td align="left">&#x2212;1.52E-4</td>
<td align="left">&#x2212;1.8E-4</td>
<td align="left">&#x2212;1.8E-4</td>
</tr>
<tr>
<td align="left">&#x3bb;</td>
<td align="left">1.7E&#x2b;01</td>
<td align="left">17.993</td>
<td align="left">2.29E&#x2b;1</td>
<td align="left">18.395</td>
<td align="left">18.231</td>
</tr>
<tr>
<td align="left">R<sub>c</sub> (&#x3a9;)</td>
<td align="left">8.0E-04</td>
<td align="left">5.8E-04</td>
<td align="left">3.83E-04</td>
<td align="left">2.8E-04</td>
<td align="left">3.5E-04</td>
</tr>
<tr>
<td align="left">b</td>
<td align="left">1.60E-02</td>
<td align="left">1.6E-02</td>
<td align="left">5.42E-02</td>
<td align="left">1.8E-02</td>
<td align="left">1.8E-02</td>
</tr>
<tr>
<td align="left">SSE</td>
<td align="left">0.354</td>
<td align="left">0.3576</td>
<td align="left">6.46&#x2013;01</td>
<td align="left">0.546</td>
<td align="left">0.3680</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="T5" position="float">
<label>TABLE 5</label>
<caption>
<p>Estimated Nedstack PS6&#x2019;s parameters.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="left"/>
<th align="center">HBA</th>
<th align="center">HGS</th>
<th align="center">HHO</th>
<th align="center">SCA</th>
<th align="center">GWO</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>1</bold>
</sub>
</td>
<td align="center">
<bold>&#x2212;0.952</bold>
</td>
<td align="center">
<bold>&#x2212;</bold>0.945</td>
<td align="center">
<bold>&#x2212;</bold>0.9525</td>
<td align="center">
<bold>&#x2212;</bold>0.948</td>
<td align="center">
<bold>&#x2212;</bold>0/949</td>
</tr>
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>2</bold>
</sub>
</td>
<td align="center">
<bold>3.29E-03</bold>
</td>
<td align="center">3.23E-03</td>
<td align="center">2.91E-03</td>
<td align="center">3.2E-03</td>
<td align="center">3.2E-03</td>
</tr>
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>3</bold>
</sub>
</td>
<td align="center">
<bold>7.40E-05</bold>
</td>
<td align="center">7.80E-05</td>
<td align="center">5.18E-05</td>
<td align="center">7.5E-05</td>
<td align="center">7.5E-05</td>
</tr>
<tr>
<td align="left">
<bold>&#x3be;</bold>
<sub>
<bold>4</bold>
</sub>
</td>
<td align="center">
<bold>&#x2212;7.24E-05</bold>
</td>
<td align="center">
<bold>&#x2212;</bold>1.9E-04</td>
<td align="center">
<bold>&#x2212;</bold>0.95E-05</td>
<td align="center">
<bold>&#x2212;</bold>1.9E-4</td>
<td align="center">
<bold>&#x2212;</bold>1.9E-4</td>
</tr>
<tr>
<td align="left">
<bold>&#x3bb;</bold>
</td>
<td align="center">
<bold>2.01E&#x2b;1</bold>
</td>
<td align="center">19.273</td>
<td align="center">1.26E&#x2b;1</td>
<td align="center">20.81</td>
<td align="center">21.65</td>
</tr>
<tr>
<td align="left">
<bold>Rc</bold>
</td>
<td align="center">
<bold>5.43E-04</bold>
</td>
<td align="center">1.00E-04</td>
<td align="center">1.00E-04</td>
<td align="center">1.3E-02</td>
<td align="center">2.9E-04</td>
</tr>
<tr>
<td align="left">
<bold>b</bold>
</td>
<td align="center">
<bold>1.60E-02</bold>
</td>
<td align="center">1.6E-02</td>
<td align="center">1.36E-02</td>
<td align="center">1.8E-02</td>
<td align="center">1.6E-02</td>
</tr>
<tr>
<td align="left">
<bold>SSE</bold>
</td>
<td align="center">
<bold>1.59E-02</bold>
</td>
<td align="center">4.6E-02</td>
<td align="center">2.07</td>
<td align="center">0.662</td>
<td align="center">0.038</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="T6" position="float">
<label>TABLE 6</label>
<caption>
<p>Statistical values for each method.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="left"/>
<th align="center">&#x2014;</th>
<th align="center">Std</th>
<th align="center">Worst</th>
<th align="center">Best</th>
<th align="center">Mean</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td rowspan="5" align="left">
<bold>BCS 500&#xa0;W</bold>
</td>
<td align="center">HBA</td>
<td align="center">
<bold>0.037</bold>
</td>
<td align="char" char=".">
<bold>0.0119</bold>
</td>
<td align="char" char=".">
<bold>0.0117</bold>
</td>
<td align="center">
<bold>0.0118</bold>
</td>
</tr>
<tr>
<td align="center">HGS</td>
<td align="center">0.934</td>
<td align="char" char=".">4.5797</td>
<td align="char" char=".">1.3265</td>
<td align="center">2.11380</td>
</tr>
<tr>
<td align="center">HHO</td>
<td align="center">0.490</td>
<td align="char" char=".">1.824</td>
<td align="char" char=".">0.0901</td>
<td align="center">1.49E-02</td>
</tr>
<tr>
<td align="center">SCA</td>
<td align="center">3.338</td>
<td align="char" char=".">19.31522</td>
<td align="char" char=".">5.150285</td>
<td align="center">8.72860</td>
</tr>
<tr>
<td align="center">GWO</td>
<td align="center">0.595</td>
<td align="char" char=".">3.806807</td>
<td align="char" char=".">1.357709</td>
<td align="center">1.91880</td>
</tr>
<tr>
<td rowspan="5" align="left">
<bold>250&#xa0;W</bold>
</td>
<td align="center">HBA</td>
<td align="center">
<bold>0.030</bold>
</td>
<td align="char" char=".">
<bold>0.4275</bold>
</td>
<td align="char" char=".">
<bold>0.3377</bold>
</td>
<td align="center">
<bold>3.54E-01</bold>
</td>
</tr>
<tr>
<td align="center">HGS</td>
<td align="center">0.018</td>
<td align="char" char=".">0.3985</td>
<td align="char" char=".">0.3377</td>
<td align="center">0.34700</td>
</tr>
<tr>
<td align="center">HHO</td>
<td align="center">0.155</td>
<td align="char" char=".">0.955</td>
<td align="char" char=".">0.422</td>
<td align="center">6.46E-01</td>
</tr>
<tr>
<td align="center">SCA</td>
<td align="center">0.155</td>
<td align="char" char=".">0.955228</td>
<td align="char" char=".">0.422466</td>
<td align="center">0.54636</td>
</tr>
<tr>
<td align="center">GWO</td>
<td align="center">0.021</td>
<td align="char" char=".">0.408939</td>
<td align="char" char=".">0.341183</td>
<td align="center">0.36809</td>
</tr>
<tr>
<td rowspan="5" align="left">
<bold>NedStack PS6</bold>
</td>
<td align="center">HBA</td>
<td align="center">
<bold>0.2158</bold>
</td>
<td align="char" char=".">
<bold>1.86</bold>
</td>
<td align="char" char=".">
<bold>1.3196</bold>
</td>
<td align="center">
<bold>1.59</bold>
</td>
</tr>
<tr>
<td align="center">HGS</td>
<td align="center">4.75E-02</td>
<td align="char" char=".">0.145</td>
<td align="char" char=".">0.0118</td>
<td align="center">0.04620</td>
</tr>
<tr>
<td align="center">HHO</td>
<td align="center">0.5955</td>
<td align="char" char=".">3.806</td>
<td align="char" char=".">1.3577</td>
<td align="center">2.07E&#x2b;00</td>
</tr>
<tr>
<td align="center">SCA</td>
<td align="center">0.49033211</td>
<td align="char" char=".">1.824527</td>
<td align="char" char=".">0.090154</td>
<td align="center">0.66195</td>
</tr>
<tr>
<td align="center">GWO</td>
<td align="center">0.05954205</td>
<td align="char" char=".">0.266837</td>
<td align="char" char=".">0.01197</td>
<td align="center">0.03821</td>
</tr>
</tbody>
</table>
</table-wrap>
<table-wrap id="T7" position="float">
<label>TABLE 7</label>
<caption>
<p>
<italic>p</italic>-value for comparison between HBA and other methods.</p>
</caption>
<table>
<thead valign="top">
<tr>
<th align="left"/>
<th align="center">250&#xa0;W</th>
<th align="center">NedStack</th>
<th align="center">BCS 500&#xa0;W</th>
</tr>
</thead>
<tbody valign="top">
<tr>
<td align="left">
<bold>HGS</bold>
</td>
<td align="center">5.32E-04</td>
<td align="center">3.45E-04</td>
<td align="center">2.13E-05</td>
</tr>
<tr>
<td align="left">
<bold>HHO</bold>
</td>
<td align="center">6.73E-07</td>
<td align="center">1.15E-07</td>
<td align="center">3.96E-06</td>
</tr>
<tr>
<td align="left">
<bold>SCA</bold>
</td>
<td align="center">2.34E-05</td>
<td align="center">8.12E-05</td>
<td align="center">4.87E-05</td>
</tr>
<tr>
<td align="left">
<bold>GWO</bold>
</td>
<td align="center">1.27E-04</td>
<td align="center">9.12E-04</td>
<td align="center">4.21E-06</td>
</tr>
</tbody>
</table>
</table-wrap>
<fig id="F5" position="float">
<label>FIGURE 5</label>
<caption>
<p>Convergence curve of SSE of datasets. <bold>(A)</bold> BSC 500, <bold>(B)</bold> 250 W, and <bold>(C)</bold> Nedstack.</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g005.tif"/>
</fig>
<fig id="F6" position="float">
<label>FIGURE 6</label>
<caption>
<p>Error % of datasets: <bold>(A)</bold> BCS 500 W, <bold>(B)</bold> 250 W module, and <bold>(C)</bold> Nedstack module.</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g006.tif"/>
</fig>
<fig id="F7" position="float">
<label>FIGURE 7</label>
<caption>
<p>I-V curves of datasets: <bold>(A)</bold> BCS 500 W, <bold>(B)</bold> 250 W, and <bold>(C)</bold> Nedstack.</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g007.tif"/>
</fig>
<fig id="F8" position="float">
<label>FIGURE 8</label>
<caption>
<p>Curves under different temperatures for BCS 500&#xa0;W using HBA. <bold>(A)</bold> I/V curves and <bold>(B)</bold> I/P curves.</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g008.tif"/>
</fig>
<fig id="F9" position="float">
<label>FIGURE 9</label>
<caption>
<p>Different RP<sub>H2</sub> and RP<sub>O2</sub> for BCS 500&#xa0;W using HBA. <bold>(A)</bold> Different RP<sub>O2</sub>. <bold>(B)</bold> Different RP<sub>H2</sub>.</p>
</caption>
<graphic xlink:href="fenrg-10-875332-g009.tif"/>
</fig>
<p>Furthermore, the values of SSE over the iterations for SCA, GWO, HGS, HHO, and HBA are presented in <xref ref-type="fig" rid="F5">Figure 5</xref> among the three datasets for SCA, GWO, HGS, and HBA to justify the produced HBA&#x2019;s convergence rate. These charts show that the HBA has a higher convergence rate than other approaches, especially in the NedStack PS6 dataset. <xref ref-type="fig" rid="F6">Figure 6</xref> also displays the voltage and measured I/V polarization percentage errors, where the percentage error was estimated as the difference between estimated and measured voltage relative to the measured voltage. The percentage error of the HBA is nearly -0.9E-3 to 4.8E-3 for BCS 500&#xa0;W and from -0.012 to.015 for 250&#xa0;W module, according to these curves. Finally, the percentage errors for the NedStack PS6 range from -0.012 to &#x2b;0.012.</p>
<p>The obtained results in <xref ref-type="fig" rid="F8">Figure 8A,B</xref> depict the effect of the three temperature values on the I/V and I/P polarization curves, respectively. The pressures RP_O2 and RP_H2 were set to justify the effect of temperature on the performance of the PEMFC stack as shown in <xref ref-type="fig" rid="F9">Figure 9A,B</xref>.</p>
<p>Various statistical parameters such as mean, standard deviation, best, and worst of the SSE are calculated to further examine the effectiveness of HBA as a PEMFC model, as shown in <xref ref-type="table" rid="T6">Table 6</xref>. From these metrics, it is clear that the HBA is better at finding optimal settings than other approaches, as evidenced by the examined datasets. We also utilized the Wilcoxon nonparametric test to see if there was a significant difference between the HBA and other approaches. <xref ref-type="table" rid="T7">Table 7</xref> shows the Wilcoxon test <italic>p</italic>-value at a significance level of 0.05. These results show that there is a considerable difference in overall datasets between the HBA and other approaches.</p>
</sec>
<sec id="s5">
<title>5 Conclusion</title>
<p>In this study, an alternative approach for estimating the model parameters of a PEMFC under various operating conditions is described. This method is based on the HBA. This algorithm has proven its efficacy in a variety of applications, which prompted us to use it. The main motivation for using the HBA for estimating the PEMFC&#x2019;s parameters is the advantage of balance between exploration and exploitation of the search space, which avoids trapping in local minima. A set of experimental series has been conducted utilizing three datasets entitled 250-W stack, BCS 500-W, and NedStack PS6 to justify the usage of the HBA to determine the PEMFC&#x2019;s parameters (i.e., &#x3bb;, Rc, &#x3be;<sub>1</sub>, &#x3be;<sub>2</sub>, &#x3be;<sub>3</sub>, &#x3be;<sub>4</sub>, and b). HBA&#x2019;s results have also been compared to those of other metaheuristic techniques such as HGS and SCA. In terms of performance measures, the results showed that the HBA outperformed other MH approaches. The findings revealed that the presented approach produced promising results and outperformed the other pproaches. The main limitation of using the HBA for estimating the parameters of PEMFCs is it was tested on three modules only. More modules are needed to be used in the experimental tests for efficient verification of the performance of the HBA. Apart from the findings generated by the HBA, it may be employed in a variety of applications, such as PV parameter estimation, mechanical engineering, and other challenges such as cloud computing and picture segmentation.</p>
</sec>
</body>
<back>
<sec sec-type="data-availability" id="s6">
<title>Data Availability Statement</title>
<p>The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.</p>
</sec>
<sec sec-type="author-contributions" id="s7">
<title>Author Contributions</title>
<p>All the authors have made a substantial, direct, and intellectual contribution to the work and approved it for publication.</p>
</sec>
<sec sec-type="funding-information" id="s8">
<title>Funding</title>
<p>Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2022R197), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.</p>
</sec>
<sec sec-type="COI-statement" id="s9">
<title>Conflict of Interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec sec-type="disclaimer" id="s10">
<title>Publisher&#x2019;s Note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors, and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
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