# A solar-powered multi-functional portable charging device (SPMFPCD) with internet-of-things (IoT)-based real-time monitoring-An innovative scheme towards energy access and management

Anis Ur Rehman, Ishaq G Muhammad Alblushi, Muhammad Fahad Zia, Haris M Khalid, Usman Inayat, Mohamed Benbouzid, S.M. Muyeen, Ghulam Amjad Hussain

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Anis Ur Rehman, Ishaq G Muhammad Alblushi, Muhammad Fahad Zia, Haris M Khalid, Usman Inayat, et al.. A solar-powered multi-functional portable charging device (SPMFPCD) with internet-of-things (IoT)-based real-time monitoring-An innovative scheme towards energy access and management. Green Technologies and Sustainability, 2025, 3 (1), pp.100134. 10.1016/j.grets.2024.100134. hal-05345029

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# A solar-powered multi-functional portable charging device (SPMFPCD) with internet-of-things (IoT)-based real-time monitoring—An innovative scheme towards energy access and management

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Anis ur Rehman<sup>a</sup>, Ishaq G. Muhammad Alblushi<sup>b</sup>, Muhammad Fahad Zia<sup>c</sup>, Haris M. Khalid<sup>d,e,*</sup>, Usman Inayat<sup>f</sup>, Mohamed Benbouzid<sup>g,h</sup>, S.M. Muyeen<sup>i</sup>, Ghulam Amjad Hussain<sup>d</sup>

## ARTICLE INFO

Keywords:

Battery energy storage system (BESS)

Internet of thing (IoT)

Real-time monitoring

Disaster management technology

Economic viability

Emergency medical charging solutions

Mul-ti-functional charging device

Public spaces charging infrastructure

Renewable energy integration (REI)

Solar-powered portable charging

## ABSTRACT

In the absence of portable charging devices, sectors such as transportation, communication, and emergency services deal with various challenges towards electric power needs while compromising on (1) operational efficiency, (2) insufficient portable charging solutions, and (3) limited versatility. This highlights the critical need for reliable and multi-functional power solutions. To provide a portable charging solution across diverse sectors, this paper proposes an innovative development of a solar-powered multi-functional portable charging device (SPMFPCD) with internet-of-thing (IoT)-based monitoring capabilities. The proposed scheme introduces a comprehensive model integrating advanced technologies which include a highly efficient solar panel, charge controller, sensors, and IoT module. The proposed system facilitates versatile charging solutions for a wide range of power requirements with real-time monitoring and data analysis through the IoT platform. Moreover, the proposed work explores the applications of the SPMFPCD in (1) emergency medical scenarios, (2) outdoor adventures, (3) disaster management, and (4) public spaces. Performance evaluation was made by proposing case studies to validate the (1) economic viability, (2) power management, and (3) environmental impact of widespread deployment of SPMFPCD in public spaces. Furthermore, detailed analysis of battery energy storage system (BESS) and photovoltaic (PV) integration for load management, seasonal dynamics, and renewable energy integration (REI) contribute to a comprehensive understanding of the proposed solution.

## 1. Introduction

### 1.1. Renewable Energy Integration (REI), energy access, and motivation of this work

In recent years, the convergence of renewable energy (RE) and energy storage technologies and advancements in smart systems have emerged in a new era of innovative solutions to tackle the challenges of diverse sectors [1]. However, while addressing these challenges, adequate energy access and its management is a primary development

challenge which is increasingly seen to act as an anti-catalyst while restraining the (1) industrial growth, (2) energy advancements, (3) economy, (4) reliability, (5) security, and (6) affordability.

The motivation for this work is driven by the need to find practical solutions to current challenges in energy access and management. The proposed research embarks on a comprehensive exploration of the (1) design, (2) implementation, and (3) impact assessment of an advanced solar-powered multi-functional portable charging device (SPMFPCD) [2]. This SPMFPCD is not merely a conventional power

<footnote><sup>a</sup> Department of Electrical Engineering, University of Azad Jammu and Kashmir, Muzaffarabad 13100, AJK, Pakistan</footnote>

<footnote><sup>b</sup> Department of Electrical and Electronics Engineering, Higher Colleges of Technology, Sharjah 7947, United Arab Emirates</footnote>

<footnote><sup>c</sup> Department of Electrical and Computer Engineering, American University in Dubai, Dubai 28282, United Arab Emirates</footnote>

<footnote><sup>d</sup> College of Engineering and Information Technology, University of Dubai, Academic City 14143, Dubai, United Arab Emirates</footnote>

<footnote><sup>e</sup> Department of Electrical and Electronic Engineering Science, University of Johannesburg, Aukland Park 2006, South Africa</footnote>

<footnote><sup>f</sup> School of Systems and Technology, University of Management and Technology, Lahore 54000, Pakistan</footnote>

<footnote><sup>g</sup> University of Brest, Institut de Recherche Dupuy de Lôme (UMR CNRS 6027)), 29238 Brest, France</footnote>

<footnote><sup>h</sup> Logistics Engineering College, Shanghai Maritime University, Shanghai 201306, China</footnote>

<footnote><sup>i</sup> Department of Electrical Engineering, Qatar University, Doha 2713, Qatar</footnote>

<footnote>* Corresponding author at: College of Engineering and Information Technology, University of Dubai, Academic City 14143, Dubai, United Arab Emirates.
E-mail addresses: engr.anisurrehman861@gmail.com (A. ur Rehman), ishaqphd@ieee.org (I.G.M. Alblushi), mfz@ieee.org (M.F. Zia), mkhalid@ud.ac.ae, harism.khalid@ieee.org (H.M. Khalid), usman.inayat@umt.edu.pk (U. Inayat), Mohamed.Benbouzid@univ-brest.fr (M. Benbouzid), sm.muyeen@qu.edu.qa (S.M. Muyeen), ghussain@ud.ac.ae (G.A. Hussain).</footnote>
## Nomenclature

### Acronyms

<table><tr><td>APF</td><td>Active Power Filter</td></tr><tr><td>BESS</td><td>Battery Energy Storage System</td></tr><tr><td>DHT</td><td>Digital Humidity and Temperature Sensor</td></tr><tr><td>DC</td><td>Direct Current</td></tr><tr><td>STATCOM</td><td>Four-Quadrant Static Synchronous Compensator</td></tr><tr><td>GPIO</td><td>General Purpose Input-Output</td></tr><tr><td>IoT</td><td>Internet of Things</td></tr><tr><td>Blynk</td><td>IoT platform for iOS or Android smartphones that is used to control Arduino, Raspberry Pi and NodeMCU via the Internet</td></tr><tr><td>MPPT</td><td>Maximum Power Point Tracking</td></tr><tr><td>NPC</td><td>Net Present Cost</td></tr><tr><td>Ni-Cd</td><td>Nickel Cadmium</td></tr><tr><td>Ni-MH</td><td>Nickel Metal Hydride</td></tr><tr><td>NodeMCU</td><td>Node Microcontroller Unit</td></tr><tr><td>PV</td><td>Photovoltaic</td></tr><tr><td>PWM</td><td>Pulse Width Modulation</td></tr><tr><td>RE</td><td>Renewable Energy</td></tr><tr><td>REI</td><td>Renewable Energy Integration</td></tr><tr><td>SPMFPCD</td><td>Solar-Powered Multi-Functional Portable Charging Device</td></tr><tr><td>SOC</td><td>States of Charge</td></tr><tr><td>SMPS</td><td>Switch Mode Power Supply</td></tr><tr><td>V2G</td><td>Vehicle-to-Grid</td></tr><tr><td>VRFB</td><td>Vanadium Redox Flow Battery</td></tr><tr><td>Wi-Fi</td><td>Wireless Fidelity</td></tr></table>

### Symbols

<table><tr><td>C<sub>BESS</sub></td><td>Charge stored in the BESS</td></tr><tr><td>C<sub>benefit</sub></td><td>Socio-economic benefits derived from the deployment</td></tr><tr><td>C<sub>hardware,i</sub></td><td>Cost associated with the ith hardware component</td></tr><tr><td>C<sub>installation,j</sub></td><td>Cost of the jth installation process</td></tr><tr><td>C<sub>operational</sub></td><td>Ongoing operational expenses</td></tr><tr><td>C<sub>setup</sub></td><td>Initial setup cost</td></tr><tr><td>E<sub>impact</sub></td><td>Quantifies positive environmental implications of large-scale integration</td></tr><tr><td>G<sub>sun</sub></td><td>Solar irradiance</td></tr><tr><td>H<sub>BESS</sub></td><td>Quantitative measure of the health status of the BESS</td></tr><tr><td>η<sub>conversion</sub></td><td>Efficiency of energy conversion</td></tr><tr><td>η<sub>PV</sub></td><td>Efficiency of the PV panels</td></tr><tr><td>Initial Capacity</td><td>Original capacity of the battery</td></tr><tr><td>m</td><td>Number of hardware components</td></tr><tr><td>n</td><td>Number of installation processes</td></tr><tr><td>P<sub>BESS</sub></td><td>Power output from the BESS</td></tr><tr><td>P<sub>Load</sub></td><td>Power demand from charging devices</td></tr><tr><td>P<sub>device,i</sub></td><td>Power demand of the ith charging device</td></tr><tr><td>P<sub>PV</sub></td><td>Power output from integrated PV panels</td></tr><tr><td>Remaining Capacity</td><td>Current capacity of the battery</td></tr><tr><td>V<sub>BESS</sub></td><td>Voltage of the BESS</td></tr></table>

source. It integrates components such as (1) PV panels, (2) a battery energy storage system (BESS), and (3) a charge controller. This represents a significant advancement in the evolution of energy infrastructure [3]. The primary objective of this study is to showcase the multifaceted applications of this SPMFPCD and to distinguish its potential to revolutionize energy access and management across different environments [4]. By investigating the features of this technological advancement, the research offers practical implications for the widespread adoption and integration of such solutions in diverse settings [5]. The goal of this study is to explore utilization of the proposed technology in various situations, such as (1) emergency medical device charging, (2) visitor amenities, (3) disaster management, and (4) public spaces. The proposed research also looks at important features such as (1) remote monitoring, (2) battery health, and the (3) economic and environmental impacts of using these charging devices on a larger scale. By combining technological advancements with a detailed analysis of costs and benefits, the proposed research aims to provide practical insights for the effective use and improvement of SPMFPCD.

## 1.2. Remote monitoring and maintenance

The main components of the proposed research include the pivotal integration of (1) advanced remote monitoring, and (2) maintenance capabilities for the SPMFPCD [6]. This strategic incorporation is supported by the Internet of things (IoT) technology. The utilization of IoT serves as a technological feature which facilitates the real-time tracking of the power parameters and health metrics of the BESS deployed within the SPMFPCD [7]. This dynamic system enables the continuous and efficient monitoring and maintenance of these critical components from a centralized control room [8]. The significance of this feature extends beyond operational convenience. It fundamentally increases the reliability and resilience of the charging infrastructure [9]. The ability to remotely diagnose, trouble-shoot, and optimize the performance of these devices not only minimizes downtime, but also establishes a robust foundation for scalable and sustainable energy infrastructure. This transformative capability aligns with the broader objectives of enhancing operational efficiency and reducing the response times to potential issues [10]. It also highlights the future technological advancements in portable energy solutions. In essence, the infusion of remote monitoring and maintenance capabilities represents a paradigm shift in the operations of charging devices [11].

## 1.3. Battery lifecycle and health monitoring

The proposed research particularly emphasizes BESS health monitoring. It recognizes the paramount importance of comprehending the lifecycle and health dynamics of batteries [12]. The core component for this is the integration of IoT technology, a technological foundation that affords the capability to delve into the intricacies of BESS health in real-time. The significance of monitoring the lifecycle and health of batteries cannot be over-stated [13]. It serves as an essential component of proactive maintenance measures. This approach allows for the anticipation and mitigation of potential issues before they evolve into critical faults [14]. IoT-driven monitoring system's continuous data streams equip operators with invaluable insights into battery component performance trends and degradation patterns. This empowers timely intervention and facilitates data-driven decision-making processes for optimizing the overall charging infrastructure [15].

The use of IoT technology for monitoring battery health goes beyond the traditional reactive maintenance approach. It offers a systematic way to implement preventive and predictive maintenance strategies, which involves addressing issues before they can affect the functionality of charging devices [16]. This not only improves operational efficiency, but also extends the lifespan of batteries and ensures the long-term reliability of the charging infrastructure [17]. Furthermore, this approach helps to create a more sustainable and economically
<table><caption>**Table 1**

Preceding affined works: Contribution and limitations.</caption><thead><tr><td>Ref.</td><td>Contribution</td><td>Limitation</td></tr></thead><tbody><tr><td>[20]</td><td>Proposed a combination of solar PV-powered multifunctional EV charger with bidirectional converters while addressing sustainable EV charging through the grid and PV-driven energy.</td><td>Lacks practical applicability assessment and real-world scalability.</td></tr><tr><td>[21]</td><td>Proposed a half-bridge resonant converter for efficient solar power extraction and storage.</td><td>Lacks system scalability, long-term stability, and real-world potential challenges.</td></tr><tr><td>[22]</td><td>Addresses PV-based battery chargers and their challenges. Highlights the short falls of traditional techniques on terminal measurements. Also pinpoints variable input power and fluctuating temperature.</td><td>Lacks an in-depth specific solution, and algorithm development towards addressing the challenges being highlighted.</td></tr><tr><td>[23]</td><td>Proposed a cost efficient, fast solar charger with a rooftop PV array for vehicles with MPPT technology for improved efficiency. However, the paper lacks a thorough discussion on the scalability and adaptability of the proposed design to different vehicle types and battery chemistries.</td><td>Lacks real-world scalability and adaptability towards vehicle types and battery composition.</td></tr><tr><td>[24]</td><td>Proposed an MPPT-driven approach in PV systems with charge varying battery system.</td><td>Lacks comparison analysis with the existing MPPT techniques.</td></tr><tr><td>[25]</td><td>Proposed a unified control system for a multifunctional EV charger with four-quadrant static synchronous compensator and an active power filter.</td><td>Lacks scalability and adaptability towards EV models and grid conditions.</td></tr><tr><td>[26]</td><td>Proposed a synchronous buck converter with soft-switching for battery charging while reducing circuit losses and diode recovery effects.</td><td>Lacks experimental validation and real world application.</td></tr><tr><td>[27]</td><td>Proposed a blended solution to enhance lead-acid battery performance in PV diesel-generator hybrid power systems. This involves an online SoC estimation method using a pH meter probe and a new battery charger based on series pulse width modulation.</td><td>Lacks scalability and adaptability towards various PV systems and environmental effect.</td></tr><tr><td>[28]</td><td>Proposed wireless sensor network-based directional charging in wireless sensor networks while achieving efficient node energy. The proposed algorithm exhibits advantages in terms of simulation results. Further research is needed to address the potential real-world challenges and scalability considerations for practical deployments.</td><td>Lacks real world application and scalability.</td></tr><tr><td>[29]</td><td>Proposed a transient thermal management system for mobile battery chargers with effective power density.</td><td>Lacks comparison analysis and scalability towards power systems.</td></tr><tr><td>[30]</td><td>Proposed a data-driven optimization framework which utilizes mixed-integer linear program for cost reduction.</td><td>Lacks experimental validation and scalability towards grid-interactive systems.</td></tr></tbody></table>

Here EV, MPPT, PV, and SoCare the acronyms of electric vehicle, maximum power point tracking, photovoltaic, and state-of-charge respectively.

viable energy storage system [18]. Overall, the integration of the IoT in battery health monitoring is a strategic enabler for the optimization of SPMFPCD. It positions them as resilient and adaptable components within the broader landscape of modern energy infrastructure [19].

## 1.4. Economic and environmental analysis of large-scale integration

The cost-benefit analysis of large-scale integration highlights the economic viability and multifaceted advantages associated with the widespread deployment of the SPMFPCD [31]. The cost-benefit analysis includes a detailed examination of the initial setup costs incurred in establishing the infrastructure for large-scale integration of SPMFPCD [32]. This involves a detailed analysis of the expenses associated with installing the required hardware, including (1) PV panels, (2) BESS, and (3) advanced converters. Furthermore, the economic evaluation goes beyond the initial setup phase to encompass ongoing operational expenses. This entails a detailed examination of the day-to-day costs associated with maintaining and managing the portable charging devices [33]. Factors such as energy consumption, regular maintenance, and potential upgrades need to be explored to provide a comprehensive understanding of the operational expenditure over the lifespan of the system [34].

However, the proposed research is not confined to financial considerations, it also highlights the socio-economic benefits resulting from the enhanced energy accessibility facilitated by the large-scale integration of SPMFPCD. This provides an exploration of the positive outwardness that extends to various sectors such as (1) healthcare, (2) tourism, and (3) disaster management. Additionally, the environmental implications of this integration are scrutinized thereby acknowledging the importance of assessing the ecological footprint associated with such innovative energy solutions. Through a comprehensive analysis of carbon emission reduction, reliance on RE sources, and potential ecological benefits, the proposed research aims to provide insight into the environmental implications of large-scale integration.

## 1.5. Literature and preceding affined review for charging solutions

Numerous studies within the existing literature have proposed discussions on possible charging solutions. This has been presented in this section as well as canvassed in Table 1.

The research [20] explores a solar PV-powered multifunctional EV charger with bidirectional converters. It addresses sustainable EV charging through the grid and solar energy utilization. However, this paper lacks a detailed discussion of the practical implementation challenges and real-world scalability of the proposed system. The work in [21] focuses on regulating the charging voltage of PV-based EV batteries through power electronic converters. The model employs a half-bridge resonant converter for efficient solar power extraction and storage. However, it lacks a comprehensive analysis of the system's scalability, long-term stability, and potential challenges in real-world applications. The study in [22] addresses the challenges of PV-based battery chargers. It highlights the limitations of traditional techniques that rely solely on terminal measurements due to variable input power and fluctuating temperature. However, the paper lacks an in-depth exploration of specific solutions or algorithms to mitigate these challenges. [23] presents a detailed design procedure for a low-cost, fast solar charger with a rooftop PV array for vehicles. It incorporates a simplified maximum power point tracking (MPPT) technique for efficiency. However, the paper lacks a thorough discussion on the scalability and adaptability of the proposed design to different vehicle types and battery chemistries. The study [24] introduces a novel approach to MPPT in PV systems. It emphasizes load dynamics, particularly with a battery at varying states of charge (SOC). However, this paper lacks a comprehensive comparison of existing MPPT techniques. [25] introduces a unified control system for a multifunctional EV charger. It serves as a four-quadrant static synchronous compensator and an active power filter on a single-phase 4.5 kVA onboard charger. This study lacks a detailed exploration of potential limitations, such as scalability and adaptability to diverse EV models or grid conditions.
The paper [26] presents an innovative synchronous buck converter with soft-switching for battery charging. The aim is to reduce circuit losses and eliminate diode recovery effects. The novel converter exhibits theoretical effectiveness in terms of low voltage ripple, minimal loss, and high efficiency based on simulation results. The paper still lacks experimental validation and a detailed discussion of potential challenges or practical considerations in real-world applications. Future research could focus on the practical implementation and scalability to explore the performance of the proposed converter under diverse conditions.

Moreover, the work in [27] introduces two innovative techniques for enhancing lead-acid battery performance in PV diesel-generator hybrid power systems. The first technique involves a novel online SoC estimation method using a pH meter probe. The second technique presents a new battery charger based on series pulse width modulation control to regulate charging current and prevent over-charging. These methods promise improved battery operation, increased lifespan, and reduced maintenance costs. This paper lacks a detailed discussion on the scalability and adaptability of these techniques to different PV hybrid system configurations and environmental conditions. The paper [28] explores the use of directional charging in wireless sensor networks, leveraging mobile chargers to achieve efficient node energy replenishment. The proposed algorithm exhibits advantages in terms of simulation results. Further research is needed to address the potential real-world challenges and scalability considerations for practical deployments. The study [29] proposes a transient thermal management system for mobile battery chargers. It dynamically adjusts the converter output power to address thermal constraints in miniaturized systems. The hardware prototype demonstrates a 40% increase in effective power density when charging a conventional laptop battery. It shows the potential of this novel approach to overcome thermal barriers and provide valuable insights for optimizing fast-charging systems. The study [30] investigates the impact of mobile charging on ridesharing fleets using real-world data to propose a data-driven optimization framework. The developed model, which utilizes a mixed-integer linear program, determines the optimal integration scenarios for mobile chargers in urban transportation systems. The results demonstrate a potential 21% reduction in total costs compared with a non-scheduling policy. This demonstrates the effectiveness of the proposed approach in minimizing daily operating costs. It also stabilizes the power profile through a vehicle-to-grid (V2G) implementation in a grid-interactive transportation system.

## 1.6. Research contributions and graphical abstract

This study makes significant contributions to the field of SPMFPCD by offering insights into their diverse applications and impact on energy access and management. The key contributions of this research can be categorized into several crucial areas. Fig. 1 shows the graphical abstract of the proposed study.

* **Applications across Industries:** This research explores and delineates practical applications of the SPMFPCD which includes (1) emergency medical device charging, (2) visitor amenities, (3) disaster management, and (4) deployment in large public spaces. These diverse use cases demonstrate the versatility and potential societal impact of this technology.

* **Remote Monitoring and Maintenance Features:** The research introduces and emphasizes the implementation of remote monitoring and maintenance capabilities facilitated by IoT technology. This innovation contributes to the operational reliability of the charging devices while allowing for real-time monitoring and efficient maintenance from a centralized control room.

* **Battery Health Monitoring:** The study also provides a detailed exploration of BESS health monitoring. Through the integration of IoT, it offers a proactive approach to battery maintenance

while ensuring longevity and reliability. The primary focus is on how battery health is critical for the sustained efficiency of the charging infrastructure.

* **Economic and Environmental Analysis:** The research study provides a comprehensive cost-benefit analysis. It also considers factors such as (1) initial setup costs, and (2) ongoing operational expenses. Additionally, it assesses the broader socio-economic benefits arising from improved energy accessibility. The environmental impact, including carbon emissions reduction and ecological benefits, is also scrutinized, contributing to a view of the implications of large-scale integration.

## 1.7. Formation of the remaining paper

The formation of the remaining paper is as follows. The problem formulation is described in Section 2. The proposed methodology is expressed in Section 3. Performance evaluation, comparative analysis and results are drawn in Section 4. Finally, conclusion is made in Section 5.

# 2. Problem formulation — A multi-functional charging framework

The problem formulation section comprises of (1) objectives and constraints of proposed research, (2) energy balance, (3) cost benefits and economic analysis, (4) BESS health monitoring, and (5) environmental assessment.

## 2.1. Objectives and constraints of proposed research

The objective of the proposed research is to maximize the overall energy balance of the SPMFPCD by optimizing the power output from PV panels and the BESS. This is achieved by meeting the power demand from charging devices.

Maximize:

$$ \eta_{pv} \times A_{pv} \times G_{sun} \times \eta_{conversion} \times \eta_{BESS} \times C_{BESS} \times V_{BESS} - \sum_{i=1}^{n} P_{device,i} \quad (1) $$

where $\eta_{pv}$ is the efficiency of the PV panels, $A_{pv}$ is the surface area of the PV panels, $G_{sun}$ is the solar irradiance, $\eta_{conversion}$ is the efficiency of energy conversion, $\eta_{BESS}$ is the efficiency of the BESS. Also, $C_{BESS}$ and $V_{BESS}$ are the charge stored and voltage in the BESS. $P_{device,i}$ is the power demand of the ith charging device.

Minimize the initial setup costs associated with hardware components and installation processes of the SPMFPCD as follows:

Minimize:

$$ \sum_{i=1}^{m} C_{\text{hardware},i} + \sum_{j=1}^{n} C_{\text{installation},j} \quad (2) $$

where $C_{\text{hardware},i}$ represents the cost associated with the ith hardware component and $C_{\text{installation},j}$ is the cost of the jth installation process.

Maximize the operational reliability index of the charging devices, emphasizing reliable and consistent performance.

Maximize:

$$ R_{\text{operational}} \quad (3) $$

Constraints:

Ensure that the power generated by the PV panels and the BESS is greater than or equal to the power demand from charging devices. This can be represented as:

$$ P_{pv} + P_{BESS} \geq P_{Load} \quad (4) $$

Assign a predefined budget limit to control the overall costs associated with the deployment and operation of the portable charging devices. This can be represented as:

$$ C_{\text{total}} \leq \text{Budget Limit} \quad (5) $$
<figure><img src="image_3.png" /><figcaption>Fig. 1. Graphical abstract: A multi-functional charging solution.</figcaption></figure>

It is also important that the health status of the BESS remains above a minimum threshold, guaranteeing long-term reliability. This is expressed as:

$$H_{\text{BESS}} \geq \text{Minimum Health Threshold} \qquad (6)$$

To reflect the sustainability of the SPMFPCD deployment, the environmental impact index also needs to meet a minimum threshold. This is stated as:

$$E_{\text{impact}} \geq \text{Minimum Environmental Sustainability Threshold} \qquad (7)$$

## 2.2. Energy balance — Capturing the equilibrium in the dynamics

The fundamental energy balance equation serves as the key component of this research. It captures the equilibrium between energy generation and consumption within the intricate dynamics of the proposed SPMFPCD. The equation is expressed with comprehensive detail as:

$$P_{\text{PV}} + P_{\text{BESS}} = P_{\text{Load}} \qquad (8)$$

where $P_{PV}$ signifies the power output from integrated PV panels, PBESS represents the power output from the BESS and $P_{Load}$ denotes the power demand from charging devices. Note (8) delves into the interplay between the energy produced by the PV panels and the BESS against the energy requirements of the charging devices.

Here $P_{PV}$ can be further expressed as:

$$P_{\text{pv}} = \eta_{\text{pv}} \cdot A_{\text{pv}} \cdot G_{\text{sun}} \cdot \eta_{\text{conversion}} \qquad (9)$$

where $\eta_{PV}$ is the efficiency of the PV panels, $A_{PV}$ is the surface area of the PV panels, $G_{sun}$ is the solar irradiance and $\eta_{conversion}$ is the efficiency of energy conversion.

Here $P_{BESS}$ can be further expressed as in (10):

$$P_{\text{BESS}} = \eta_{\text{BESS}} \cdot C_{\text{BESS}} \cdot V_{\text{BESS}} \qquad (10)$$

## 2.3. Cost benefits and economic analysis

The intricacies of the cost-benefit analysis lay the basis for evaluating the financial viability of the proposed SPMFPCD. This can be expressed as:

$$C_{\text{total}} = C_{\text{setup}} + C_{\text{operational}} - C_{\text{benefits}} \qquad (11)$$

where $C_{total}$ signifies the overall cost, $C_{setup}$ represents the initial setup cost, $C_{operational}$ denotes the ongoing operational expenses and $C_{benefit}$ encapsulates the broader socio-economic benefits derived from the deployment.

$C_{setup}$ can be further expressed as:

$$C_{\text{setup}} = \sum_{i=1}^{m} C_{\text{hardware},i} + \sum_{j=1}^{n} C_{\text{installation},j} \qquad (12)$$

In the above equation, $m$ is the number of hardware components, $n$ is the number of installation processes, $C_{hardware,i}$ is the cost associated with the $i$th hardware component and $C_{installation,j}$ is the cost of the $j$th installation process.

$C_{operational}$ can be expressed as:

$$C_{\text{operational}} = \sum_{k=1}^{p} C_{\text{maintenance},k} + \sum_{i=1}^{q} C_{\text{energy},i} \qquad (13)$$

where $p$ is the total number of maintenance processes, $q$ is the total number of energy-related expenses, $C_{maintenance,k}$ is the cost of the $k$th maintenance process and $C_{energy,i}$ is the cost associated with the $i$th energy-related expense.

$C_{benefits}$ can be stated as:

$$C_{\text{benefits}} = \sum_{r=1}^{s} B_{\text{category},r} \qquad (14)$$

In (14), $s$ is the number of socio-economic benefit categories, $B_{category,r}$ is the quantifiable benefit associated with the $r$-th socio-economic category.
## 2.4. BESS health monitoring

The battery health monitoring aspect is a critical element for proactive maintenance strategies in ensuring the sustained performance of the BESS. The battery health monitoring can be represented as follows:

$$H_{\text{BESS}} = \frac{\text{Remaining Capacity}}{\text{Initial Capacity}} \times 100\% \qquad (15)$$

where $H_{BESS}$ serves as a quantitative measure gauging the health status of the BESS. Remaining Capacity denotes the current capacity of the battery, and Initial Capacity represents the original capacity of the battery.

## 2.5. Environmental assessment – An implication towards large-scale integration

The environmental impact assessment plays a crucial facet in gauging the broader ecological implications of large-scale integration of the proposed SPMFPCD. The environmental impact assessment is elaborated as follows:

$$E_{\text{impact}} = \frac{\text{Carbon Emission Reduction} + \text{Ecological Benefits}}{\text{Total Environmental Impact}} \times 100\% \qquad (16)$$

where $E_{impact}$ quantifies the positive environmental implications of large-scale integration. The components include (1) Carbon Emissions Reduction, (2) Ecological Benefits, and (3) Total Environmental Impact.

# 3. Proposed methodology

This proposed research employs a comprehensive methodology to investigate and evaluate the advanced prototype of a portable charging device integrating: (1) PV panels, (2) a BESS, (3) advanced converters, and (4) IoT technology. The methodology is structured around key components aimed at understanding the design, implementation, and impact assessment of this innovative energy infrastructure.

## 3.1. Control room-based remote monitoring of PV system – The prototype implementation

This subsection talks about the control room-based remote monitoring of PV system which involves two different phases of prototype development.

### 3.1.1. Prototype development first phase – IoT technology

In the first phase of the prototype development, the focus lies on incorporating IoT technology to establish a robust remote monitoring and maintenance system. The prototype comprises a PV system equipped with DC and voltage sensors. These sensors enable real-time tracking of power parameters, including current and voltage outputs from the PV system. The key component of this system is the centralized control room, strategically designed to oversee SPMFPCD installed at various locations. The power parameters of PV system are transmitted to the control room through the IoT application. The integration of IoT ensures a dynamic and interconnected network, enabling efficient communication between the PV system and the control room. The IoT technology acts as the backbone, facilitating the transmission of critical operational data for analysis and decision-making.

Continuous data streams originating from IoT-driven systems serve as a valuable source of information. These data streams encapsulate real-time updates on the operational status of the PV system, encompassing parameters such as DC and voltage. The continuous data collection process is instrumental in creating a comprehensive overview of the system performance. The data collected provides insights into the efficiency and health of the PV system while offering a detailed overview of its operational state. This continuous monitoring helps in proactive measures to address potential issues ensuring optimal performance and reliability.

### 3.1.2. Prototype development second phase – Data collection and analysis

In the second phase, the collected data undergoes a thorough analysis within the centralized control room. This analysis serves multiple purposes which includes (1) diagnosis, (2) troubleshooting, and (3) optimization of the PV system. The control room becomes a nerve centre where skilled personnel (1) interpret the data, (2) identify the trends, and (3) make informed decisions. Furthermore, to facilitate maintenance and cleaning operations for the SPMFPCD, an IoT-enabled cleaning system has been integrated. This system incorporates a servo motor coupled with a wiper mechanism. The servo motor, in conjunction with the wiper, efficiently cleans the PV system, ensuring optimal functionality and performance.

## 3.2. BESS health monitoring prototype

This section details the design and implementation of a prototype for monitoring the health of the BESS in real-time. The prototype integrates IoT technology for continuous monitoring and proactive maintenance. The monitoring system includes (1) power parameters, (2) charging and discharging status, (3) SoC, (4) power temperature, and (5) fire alarm system.

### 3.2.1. Monitoring and integration of IoT devices

The prototype incorporates a BESS to store and supply energy efficiently. The BESS is equipped with sensors to capture essential parameters, including (1) SoC, (2) temperature, and (3) power levels during charging and discharging. To enable real-time monitoring, IoT devices are integrated into the BESS. These devices facilitate communication between the BESS and the central control room, allowing seamless data transmission. Sensors are deployed to measure the DC and voltage of the BESS. These sensors provide crucial data for assessing the performance and health of the battery. The user interface is developed using the Blynk IoT application. It serves as a visual representation of the BESS parameters, allowing easy access to real-time data and control functionalities.

The IoT devices establish a communication link between the BESS and the central control room. This integration enables (1) real-time monitoring of power parameters, (2) charging/discharging status, (3) SoC, and (4) temperature. Continuous data streams, including (1) power levels, (2) temperature variations, and (3) SoC, are transmitted from the BESS to the central control room via the IoT devices. This ensures that any changes or anomalies are promptly detected.

### 3.2.2. Pseudo code and model design for real-time monitoring and maintenance of proposed SPMFPCD

This section explains the pseudo code for real-time monitoring and maintenance of PV and BESS health monitoring (See Table 2). This pseudo-code outlines a real-time monitoring and maintenance algorithm for a PV and BESS. The initialization phase (lines no. 1–5) involves importing libraries, configuring Blynk and WiFi, and setting up hardware parameters. System configuration (lines no. 6–10) includes establishing communication and initializing components like the servo motor and DHT sensor. The main loop (line no. 11–18) continuously monitors and collects data, computing metrics for voltage, current, temperature, and humidity. Results are displayed locally and transmitted to Blynk for remote viewing. Servo motor control (lines no. 19–22) responds to V9 updates, turning the motor on or off accordingly. The algorithm concludes at line no. 23.

Fig. 2 shows the model design of proposed SPMFPCD. It shows a charging solution with real-time monitoring and maintenance of PV and BESS health monitoring work.

## 3.3. Economic and environmental analysis

This section conducts a thorough evaluation of the economic viability and environmental impact associated with the deployment of the SPMFPCD. It emphasizes two key components: (1) cost–benefit analysis, and (2) environmental impact assessment.
<figure><img src="image_4.png" /><figcaption>**Fig. 2.** Proposed SPMFPCD model design.</figcaption></figure>

Here IoT, PV, DC, BESS, and SoC are the acronyms of internet of things, direct current, battery energy storage system, and state-of-charge respectively.

<table><caption>**Table 2**
Pseudo code for monitoring and maintenance of proposed SPMFPCD.</caption><thead><tr><th>Algorithm</th><th>Real-time monitoring and maintenance of PV and BESS health monitoring.</th></tr></thead><tbody><tr><td>1.</td><td><strong>Initiate System:</strong></td></tr><tr><td>2.</td><td>Import essential libraries.</td></tr><tr><td>3.</td><td>Configure Blynk and WiFi credentials.</td></tr><tr><td>4.</td><td>Define hardware and calibration parameters.</td></tr><tr><td>5.</td><td>Set up a DHT object for temperature and humidity sensing.</td></tr><tr><td>6.</td><td><strong>Configure System:</strong></td></tr><tr><td>7.</td><td>Establish serial communication.</td></tr><tr><td>8.</td><td>Connect to WiFi and Blynk server.</td></tr><tr><td>9.</td><td>Initialize GPIO pins for Servo Motor control.</td></tr><tr><td>10.</td><td>Activate DHT sensor.</td></tr><tr><td>11.</td><td><strong>Continuous Monitoring Loop:</strong></td></tr><tr><td>12.</td><td>Enter a perpetual loop for real-time monitoring.</td></tr><tr><td>13.</td><td>Execute Blynk tasks for server communication.</td></tr><tr><td>14.</td><td>Read voltage and current from sensors.</td></tr><tr><td>15.</td><td>Obtain temperature and humidity data.</td></tr><tr><td>16.</td><td>Compute power and charging/discharging metrics.</td></tr><tr><td>17.</td><td>Display metrics on the serial monitor.</td></tr><tr><td>18.</td><td>Transmit data to Blynk for remote visualization.</td></tr><tr><td>19.</td><td><strong>Servo Motor Control:</strong></td></tr><tr><td>20.</td><td>Receive V9 updates for Servo Motor control.</td></tr><tr><td>21.</td><td>If HIGH, switch on the Servo Motor.</td></tr><tr><td>22.</td><td>If LOW, switch off the Servo Motor.</td></tr><tr><td>23.</td><td>End</td></tr></tbody></table>

Here Blynk, DHT, GPIO, and Wi-Fi are the abbreviations of an IoT platform for iOS or Android smartphones that is used to control Arduino, Raspberry Pi and NodeMCU via the Internet, digital humidity and temperature sensor, general purpose input-output, and wireless fidelity respectively.

### 3.3.1. Cost-benefit analysis

The economic analysis initiates a detailed examination of the initial setup costs incurred in establishing the infrastructure for large-scale integration of SPMFPCD. This involves analysing expenses related to installing essential hardware components including (1) PV panels, (2) BESS, and (3) advanced converters. Each hardware component cost is considered, providing a comprehensive overview of the financial investment required for the initial deployment of the device. After the setup phase, the analysis extends to encompass ongoing operational

expenses. This involves an examination of day-to-day costs associated with maintaining and managing the SPMFPCD. Factors such as (1) energy consumption, (2) regular maintenance, and (3) potential upgrades, are scrutinized to provide an understanding of the operational expenditure throughout the system lifespan.

The analysis is not confined to financial considerations, but it also incorporates a broader perspective by assessing socio-economic benefits. These benefits arise from improved energy accessibility facilitated by the large-scale integration of SPMFPCD. The exploration encompasses positive externalities that extend to various sectors such as (1) healthcare, (2) tourism, and (3) disaster management. By quantifying these socio-economic benefits, the analysis provides insights into the broader positive impacts on society and various industries.

### 3.3.2. Environmental impact assessment

Environmental impact assessment considers the carbon emission reduction achieved through the large-scale integration of portable charging devices. This involves evaluating the extent to which deployment reduces carbon emissions and hence promotes a cleaner and more sustainable energy ecosystem. Factors such as the utilization of renewable energy sources and the displacement of traditional, more carbon-intensive power sources are considered. Furthermore, the evaluation examines the potential ecological benefits of deployment, including its impact on local ecosystems, biodiversity, and overall ecological footprint. By evaluating the positive ecological contributions, this analysis aims to provide a comprehensive understanding of the environmental sustainability implications of widespread SPMFPCD integration.

## 4. Performance evaluation, comparative analysis, and results

The result sections provide a comprehensive analysis of the prototype's performance, highlighting its innovative design, real-time monitoring capabilities, and diverse applications across sectors. Each subsection offers valuable insights into specific aspects of the SPMFPCD, showcasing its efficiency, adaptability, and potential impact on various scenarios.
<figure><img src="image_5.png" /><figcaption>Fig. 3. Prototype of SPMFPCD.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 4. 5 V output of multi-purpose portable charger.</figcaption></figure>

This section comprises of (1) prototype of SPMFPCD, IoT-based monitoring and maintenance prototype for (2) solar system, (3) BESS, (4) applications of SPMFPCD in various sectors, and (5) case study and performance evaluation, (6) comparative analysis with other techniques.

## 4.1. Prototype of SPMFPCD

The prototype in Fig. 3 successfully represents an integration of advanced technologies and innovative design for the development of an SPMFPCD with IoT monitoring capabilities. The intricate system is composed of several key components. Each component is playing a crucial role in ensuring (1) optimal functionality, and (2) user-centric efficiency. The main feature is: (1) a highly efficient solar panel, intelligently combined with (2) a charge controller, (3) set of voltage sensors, (4) a NodeMCU, and (5) power converter modules. The integration of these components contributes to the creation of a versatile charging solution, capable of addressing a wide range of power needs. The pivotal role played by the voltage sensor cannot be overstated. This component collects real-time data from the solar panel, ensuring the optimal utilization of sunlight. The acquired data undergoes processing before being transmitted to the NodeMCU. NodeMCU is a sophisticated microcontroller specifically designed to handle the intricacies of IoT technology.

The NodeMCU takes charge of the data transmission process, facilitating the transfer of information to the cloud through the Blynk IoT platform. This cloud connectivity introduces possibilities for remote monitoring and data analysis. It ensures that the system consistently operates at peak efficiency. The Blynk IoT channel in the cloud serves as a central component for real-time battery level monitoring, collecting, storing, and transmitting data to keep users consistently informed about the device's power status. To enhance user experience, the model

incorporates LCD screens dedicated to battery level monitoring, accommodating both 5-volt and 18-volt power outputs. These screens provide users with clear, real-time information about the battery's status, empowering them to manage power resources effectively. Whether charging a mobile phone, tablet, or blood pressure machine or powering up a laptop, this device offers versatile solutions to a broad spectrum of power needs.

In the development of the 5-volt charger (as shown in Fig. 4) for the proposed SPMFPCD, a crucial component was the implementation of a “buck converter,”. A DC-to-DC power converter is renowned for its efficiency in increasing current while simultaneously reducing voltage from input to output. It functions as a step-down converter within the broader realm of switched-mode power supply (SMPS). The proposed model strategically connected the buck converter to a 15-volt battery to establish a low voltage charger. Through the conversion process, the buck converter effectively reduced the input voltage from 7 V to a 5-volt output. This design choice ensures optimal power efficiency and voltage regulation, providing a reliable and effective solution for charging various devices within the 5-volt power range.

In the formation of the 18-volt charger for the charging device (Fig. 5), a pivotal element was the incorporation of a boost converter. It is also recognized as a step-up converter, within the DC-to-DC power conversion process. The boost converter utilizes the inductor's ability to manage current changes and store energy in its magnetic field. Notably, the boost converter's output voltage consistently surpasses its input voltage. The proposed model strategically employed the boost converter to establish a rapid charging capability. With an input voltage of 15 V, the boost converter elevated the output voltage to 18 V, facilitating swift charging of the load battery. This design choice ensures an efficient and expedited charging process for devices requiring an 18-volt power supply.
<figure><img src="image_7.png" /><figcaption>Fig. 5. 18 V output of multi-purpose portable charger.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Fig. 6. Environmental and power parameters monitoring of PV system in a control room.</figcaption></figure>

## 4.2. Grid interaction and load balancing in solar-powered systems: Monthly trends and observations

The successful implementation of the IoT-based monitoring and maintenance prototype for solar systems marks a significant achievement. Utilizing the Blynk IoT application, the prototype enables real-time monitoring of critical power parameters in PV systems. These parameters include (1) power, (2) current, and (3) voltage. This intuitive application provides users with a user-friendly interface to effortlessly access and observe real-time data, enhancing the overall understanding of the system performance. Besides power parameters, the prototype incorporates an environmental condition monitoring feature, offering insights into the external factors influencing the solar installation. The real-time tracking of environmental conditions is a valuable addition, empowering users to proactively address any issues that may impact system efficiency. A significant innovation in the prototype is the integration of a servo motor with a wiper mechanism designed for cleaning solar panels. This feature enables users situated in a control room to remotely operate the servo motor through the Blynk IoT application. The ability to initiate the cleaning process from a distance ensures that the solar panels remain free from debris and contaminants, contributing to optimized energy harvest and prolonged system lifespan. Figs. 6 and 7 show the (1) power and environmental parameter monitoring of the PV system, (2) servo motor-based cleaning features, and (3) power parameters variation analysis.

The remote operation of the servo motor is facilitated through the Blynk IoT user interface which provides users with a convenient means to activate the cleaning mechanism. This remote functionality is pivotal for maintenance purposes which offers an efficient solution to keep solar panels clear of obstructions and ensure sustained optimal performance. Visual representation of the results is provided through these visuals as above showcasing the Blynk IoT user interface and the physical prototype. These visuals offer a comprehensive view of the system's design, clearly demonstrating the integration of monitoring features and the servo motor for efficient maintenance. As a whole the developed IoT-based prototype successfully combines the (1) monitoring capabilities of the Blynk IoT application, (2) environmental condition tracking, and (3) remote servo motor operation, while enhancing the efficiency, resilience, and longevity of solar energy systems.

## 4.3. IoT-based monitoring and maintenance prototype for BESS

The development of a prototype for BESS health monitoring represents a significant stride in enhancing the safety and efficiency of energy storage infrastructure as depicted in Fig. 8. The prototype incorporates a flat sensor for the detection of fire within the BESS, providing a crucial safety measure. This fire detection system is seamlessly integrated with the Blynk IoT platform while allowing for real-time monitoring from a remote-control room. The integration with Blynk
<figure><img src="image_9.png" /><figcaption>Fig. 7. Voltage, current, and power variation analysis.</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>Fig. 8. BESS health and protection monitoring.</figcaption></figure>

enables operators to (1) promptly respond to any fire incidents, (2) mitigating potential risks, and (3) ensuring the safety of the energy storage facility. Note the BESS voltage in Fig. 8 is showing the amplitude of 15 volt and the BESS discharge from 10 to 12 volt. However, as shown in the proposed Fig. 8, the BESS discharges up to 5 V. This variation is a noise and not the complete discharge of the BESS. At the start when system is turned on, the little spikes occur until system reach a stable stage. These variations of little spikes are for 5 to 10 s. This is because initially the BESS is not fully charged and therefore it is reflecting a low SoC.

Furthermore, the prototype includes comprehensive monitoring of charging and discharging processes along with the tracking of (1) current, (2) power variation, and (3) voltage variation. These parameters are monitored in real-time through the Blynk IoT application, offering operators a view of the BESS performance. The real-time monitoring of these critical parameters facilitates proactive management and timely intervention to optimize the charging and discharging cycles, thereby extending the overall lifespan of the energy storage system. In addition to electrical parameters, the prototype addresses environmental factors by incorporating the monitoring of temperature and humidity within the BESS. The Blynk IoT platform serves as a reliable interface for monitoring these environmental conditions, providing operators with insights into the operational environment of the BESS. This environmental monitoring is essential for maintaining optimal operating conditions and preventing adverse effects on the BESS components.

Thus, the proposed BESS health monitoring prototype with its features of (1) fire detection, (2) real-time monitoring of charging and discharging parameters, and (3) environmental condition tracking, offers a comprehensive solution for ensuring the safety, efficiency, and longevity of BESS. The integration with the Blynk IoT platform further enhances the accessibility and responsiveness of the monitoring system, empowering operators to make informed decisions and proactively manage the BESS for optimal performance.

## 4.4. Applications of SPMFPCD in different sectors

This section discusses applications of SPMFCD in various sectors. This includes: (1) emergency medical device charging, (2) outdoor adventures and camping, (3) disaster management, and (4) public spaces.

### 4.4.1. Emergency medical device charging

In emergency medical scenarios, the SPMFPCD equipped with IoT monitoring capabilities serves as a critical component for ensuring uninterrupted power to essential medical devices. The real-time monitoring facilitated by the Blynk IoT platform allows healthcare professionals to closely track battery levels, ensuring that devices like blood pressure machines remain operational during crucial moments. The integration
of LCD screens dedicated to battery level monitoring provides imme-
diate and detailed insights, enabling healthcare practitioners to make
informed decisions swiftly. This application becomes particularly cru-
cial in emergency rooms, clinics, and field medical setups, contributing
to enhanced patient care and medical response efficiency.

4.4.2. Outdoor adventures and camping

In the context of outdoor adventures such as camping in hilly areas,
the SPMFPCD becomes an essential gadget for modern campers. The
solar panel harnesses sunlight efficiently, providing a sustainable power
source for charging electronic devices like smartphones, cameras, and
GPS devices. The IoT monitoring feature allows campers to track bat-
tery levels in real time, ensuring that essential devices remain charged
through-out the camping experience. This application significantly en-
hances the convenience and safety of outdoor enthusiasts, enabling
them to stay connected and navigate efficiently in remote hilly terrains.

4.4.3. Disaster management

In disaster management scenarios, the SPMFPCD with IoT monitor-
ing proves to be a resilient and indispensable tool. The real-time moni-
toring features empower disaster management teams to remotely track
available power, making informed decisions on resource allocation.
The dual-output capability becomes a strategic advantage, supporting
both standard electronic devices and specialized equipment used in
disaster response, such as (1) communication devices, and (2) medical
equipment. This application significantly contributes to the overall
efficiency and connectivity of disaster response operations, especially
in areas where conventional power sources may be disrupted.

4.4.4. Public spaces

Deploying SPMFPCD in public spaces has far-reaching implications for enhancing the overall technological infrastructure and convenience. The real-time monitoring capabilities through the Blynk IoT platform allow administrators to (1) delve into detailed usage patterns, (2) optimize charging cycles, and (3) promptly address any maintenance issues. This application ensures a seamless charging experience for the general public, promoting a technologically advanced and user-friendly environment. The LCD screens displaying battery levels become not just informative but also a part of the user interface, contributing to an enhanced sense of transparency and trust in the charging service. This application extends to urban parks, public transportation hubs, recreational areas, and any location where people rely on electronic devices while on the go.

4.5. Case study and performance evaluation

This section discusses case study to have performance evaluation
towards public spaces with SPMFPCD. It comprises of (1) case study
system details, (2) analysis of BESS and PV integration for load man-
agement, (3) seasonal dynamics of BESS, (4) seasonal REI and charg-
ing/discharging dynamics of BESS, (5) economic and environmental
implications, and (6) comparison analysis with other techniques.

4.5.1. Case study system details – Public spaces with SPMFPCD

A case study was conducted on a public space equipped with 25 SPMFPCD, each featuring both 5-volt and 18-volt charging ports (Fig. 9). A comprehensive analysis of power management, seasonal dynamics, economic viability, and environmental impact was undertaken. The investigation aimed to assess the effectiveness of the integrated PV and BESS-based SPMFPCD in meeting the power demands of users while ensuring sustainability and economic feasibility.

The power management analysis focused on evaluating the perfor-
mance of the PV and BESS systems in meeting the charging needs of
electronic devices. A detailed investigation has been performed on how
systems managed power distribution across the 25 SPMFPCD, ensuring
optimal charging rates and availability for users. The economic viability

<figure><img src="image_11.png" /><figcaption>Fig. 9. Schematic diagram of case study: 25 SPMFPCD in a public space.
Here CP is the acronym of charging point.</figcaption></figure>

assessment delved into the cost-effectiveness of deploying multiple
SPMFPCD in the public space. This involved analysing the initial setup
costs and maintenance expenses over time. The environmental impact
analysis aimed to quantify the sustainability of the SPMFPCD. Factors
such as carbon footprint reduction through the use of solar power, and
the overall environmental benefits of reducing reliance on conventional
power sources were assessed. The study explored how the integration
of PV and BESS contributed to minimizing the environmental impact
of providing charging services in public spaces.

4.5.2. Analysis of BESS and PV integration for load management

The power-sharing dynamics between BESS and PV systems to meet
electrical load requirements during winter and summer seasons are
presented in Figs. 10 and 11. The data represents a 24-h day for both
winter and summer. It also highlights the variations in solar power,
storage power, and load.

In the winter season, during the initial hours, solar power genera-
tion is negligible, and the load variation is met primarily through the
discharge of stored energy from the BESS. As the day progresses, solar
power begins to contribute, peaking around midday. The storage power
also experiences fluctuations, with the BESS charging during periods of
excess solar generation and discharging when solar input is insufficient
to meet the load. Notably, during peak demand hours, the combined
power from solar and storage is effectively utilized to meet the load
requirements, showcasing the cooperation between PV and BESS (See
Fig. 10).

On the other hand, in the summer season, solar power generation is more prominent, with a noticeable increase in daytime hours. During this period, the PV system actively contributes to meeting the load, and any excess energy is stored in the BESS for later use. As the evening approaches, solar power diminishes, and the BESS takes over to bridge the gap until the next day's solar generation begins. The storage power remains dynamic, adjusting to the availability of solar energy and load demand (See Fig. 11).

Comparing the two seasons, it is evident that the power-sharing
dynamics adapt to the seasonal variations in solar energy. In winter,
the reliance on stored energy is higher, while in summer, the PV system
plays a more significant role. The combined efforts of BESS and PV
result in a balanced and reliable power supply throughout the 24-
h cycle. It showcases the effectiveness of this integrated approach in
addressing the challenges of load variations in different seasons.
<figure><img src="image_12.png" /><figcaption>Fig. 10. Analysis of BESS and PV power integration for load management (Winter).</figcaption></figure>

<figure><img src="image_13.png" /><figcaption>Fig. 11. Analysis of BESS and PV power integration for load management (Summer).</figcaption></figure>

On the other hand, in the summer season, solar power generation is more prominent, with a noticeable increase in daytime hours. During this period, the PV system actively contributes to meeting the load, and any excess energy is stored in the BESS for later use. As the evening approaches, solar power diminishes, and the BESS takes over to bridge the gap until the next day's solar generation begins. The storage power remains dynamic, adjusting to the availability of solar energy and load demand.

Comparing the two seasons, it is evident that the power-sharing dynamics adapt to the seasonal variations in solar energy. In winter, the reliance on stored energy is higher, while in summer, the PV system plays a more significant role. The combined efforts of BESS and PV result in a balanced and reliable power supply throughout the 24-h cycle. It showcases the effectiveness of this integrated approach in addressing the challenges of load variations in different seasons.

### 4.5.3. *Seasonal dynamics of BESS*

The results detailing the BESS energy content and SoC variations over 24 h during winter and summer are presented in Figs. 12 and 13. These metrics provide valuable insights into the performance and

<figure><img src="image_14.png" /><figcaption>Fig. 12. Seasonal dynamics of BESS (Winter).</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>Fig. 13. Seasonal dynamics of BESS (Summer).</figcaption></figure>

utilization of the BESS during different seasons. In winter, the BESS energy content gradually decreases from the initial hours to its lowest point. This reflects the discharge of stored energy to meet the electrical load during periods of low solar power generation. Notably, the BESS SoC follows a similar trend, gradually decreasing as the load is fulfilled. During peak solar generation hours, there is a visible recovery in BESS energy content and SoC, indicating effective charging. The highest BESS energy content and SoC are observed in the late afternoon and early evening, show-casing the successful storage of excess energy during daylight hours.

Conversely, in summer, the BESS energy content starts at a lower level compared to winter. This reflects a reduced reliance on stored energy during this season with higher solar power availability. The BESS SoC follows a pattern of increase during daylight hours, reaching its peak in the late afternoon. The overall variation in BESS energy content and SoC is less pronounced in summer. This highlights the greater contribution of solar power in meeting the load. The lowest levels of BESS energy content and SoC occur during the night when solar generation is minimal.

Comparing the two seasons, it is evident that the BESS plays a more critical role in winter, with greater discharge and subsequent recharge cycles. In contrast, during summer, the BESS operates with a more consistent and higher SoC, indicative of its ability to store excess solar energy efficiently.
<figure><img src="image_16.png" /><figcaption>Fig. 14. REI and charging/discharging dynamics of BESS (Winter).</figcaption></figure>

<figure><img src="image_17.png" /><figcaption>Fig. 15. REI and charging/discharging dynamics of BESS (Summer).</figcaption></figure>

### 4.5.4. Seasonal REI and charging/discharging dynamics of BESS

Figs. 14 and 15 provide insights into the RE penetration percentage and the charging/discharging dynamics of the BESS during winter and summer. This information helps us understand how effectively the system integrates RE into the overall power supply and how the BESS responds to seasonal variations.

In winter, RE penetration is relatively low during the initial hours, indicating minimal reliance on renewable sources. However, as the day progresses, there is a notable increase in renewable energy penetration, reaching its peak at midday. This aligns with the increased solar power generation during daylight hours. The BESS responds by discharging during periods of low RE penetration, ensuring a consistent power supply. During high penetration periods, the BESS absorbs excess power, contributing to charging. Notably, there is a significant positive correlation between renewable energy penetration and BESS charging (See Fig. 14).

Conversely, in summer, the RE penetration percentage is higher overall, reflecting increased solar power availability. During daylight hours, RE penetration is prominent, with the BESS absorbing excess power for storage. The peak renewable energy penetration aligns with peak solar generation and the BESS discharges during periods of lower penetration or higher load demand. This adaptive behaviour of the

<table><caption>Table 3
Economic implications of large scale integration.</caption><thead><tr><td>NPC ($)</td><td>COE ($)</td><td>Operating Cost ($)</td><td>Initial capital cost ($)</td></tr></thead><tbody><tr><td>1.215</td><td>0.101</td><td>23.98</td><td>905.50</td></tr></tbody></table>

BESS contributes to grid stability and efficient use of renewable energy (See Fig. 15).

Comparing the two seasons, winter exhibits a more pronounced variation in renewable energy penetration, with the BESS playing a crucial role in balancing the fluctuations. In summer, the BESS primarily focuses on absorbing excess energy during periods of high RE penetration, contributing to sustained power supply during periods of lower solar generation.

### 4.5.5. Economic and environmental implications

The economic and environmental analysis of the integrated BESS and PV system reveals a promising and sustainable energy solution (Table 3). The net present cost (NPC) of $1215.47 reflects the total lifetime cost, considering initial capital, operating expenses, and future discounted costs. At a competitive cost of energy (COE) of $0.10 per unit and an annual operating cost of $23.97. The system demonstrates economic efficiency and financial viability. The initial capital investment of $905.5 highlights the upfront commitment required for implementing the BESS and PV infrastructure. Notably, the environmental impact is notably positive, with zero carbon dioxide emissions associated with the integrated system. This aligns with broader sustainability goals, emphasizing the environmentally friendly nature of the BESS and PV integration. Collectively, the economic and environmental analysis positions the integrated BESS and PV system as an economically viable and environmentally sustainable solution for meeting energy needs.

### 4.6. Comparative analysis with other techniques

The proposed paper stands out as an innovative breakthrough in portable charging solutions, particularly when compared to the existing literature (Table 4). It introduces a SPMFPCD with IoT monitoring capabilities which showcase an innovative model integrating advanced technologies. Unlike the other papers that focus on traditional charging techniques, the proposed study offers a versatile solution for diverse power needs, facilitated by real-time monitoring and IoT-based control. Additionally, it explores applications in (1) emergency scenarios, (2) outdoor adventures, (3) disaster management, and (4) public spaces, expanding its utility. The inclusion of detailed case studies assessing economic viability and environmental impact adds depth to the proposal, making it a comprehensive and innovative contribution in the field.

## 5. Conclusion

In conclusion, this proposed research has successfully introduced and demonstrated the effectiveness of a SPMFPCD with IoT monitoring capabilities. The developed model integrates advanced technologies to provide versatile charging solutions for various power needs. The inclusion of IoT-based monitoring systems for solar installations, BESS health monitoring, and comprehensive load management showcases the adaptability and resilience of the proposed solutions. Case studies conducted in public spaces underscore the economic viability and environmental sustainability of the integrated BESS and PV systems. Economic analysis reveals a NPC of $1215.47, a competitive COE at $0.10 per unit, and an annual operating cost of $23.97. The seasonal dynamics analysis reveals the system's ability to balance variations in solar energy, ensuring reliable power supply throughout the year. The economic and environmental analysis further supports the conclusion that the integrated BESS and PV system represents a promising and
<table><caption>**Table 4**

Comparative analysis of charging system papers: Emphasizing the innovation of the proposed paper.</caption><thead><tr><th>Feature aspect</th><th>Proposed paper</th><th>[35]</th><th>[36]</th><th>[37]</th><th>[38]</th><th>[39]</th></tr></thead><tbody><tr><td>Integration of Renewable Sources</td><td>✓ Solar-powered with IoT monitoring capabilities</td><td>✓ PV-based battery chargers</td><td>✓ Rooftop PV array with simplified MPPT technique</td><td>✓ Solar MPPT charger for Vanadium Redox Flow battery</td><td>✓ PV panel charging battery with load-dependent MPPT</td><td>✓ Wind and solar for EV charging with hybrid energy management</td></tr><tr><td>Charging System Efficiency</td><td>✓ Versatile charging solutions for diverse power needs</td><td>✗ Evaluation of traditional charging techniques</td><td>✓ Fast solar charger with simplified MPPT technique</td><td>✓ Real-time flow control integrated solar PV MPPT for VRFB</td><td>✓ Load-dependent MPPT considering battery states of charge</td><td>✓ Optimization algorithms for RE share and cost</td></tr><tr><td>Battery Compatibility and Control</td><td>✓ IoT-based monitoring and real-time data analysis</td><td>✗ Evaluation of major battery chemistries (NiCd, NiMH, Li-ion, lead-acid)</td><td>✓ Linearized models for accurate charge control</td><td>✓ Real-time flow control for VRFB charging</td><td>✓ Focus on load type for MPPT and protection of components</td><td>✓ Energy storage and power grid integration for EV charging</td></tr><tr><td>Application Scenarios</td><td>✓ Emergency medical scenarios, outdoor adventures, disaster management, public spaces</td><td>✗ Limited to evaluating major battery chemistries</td><td>✗ Limited to rooftop PV array and lead-acid battery</td><td>✓ Practical 1 kW VRFB system operation in sunny and cloudy weather conditions</td><td>✓ Focus on load type and protection of components, laboratory prototype</td><td>✓ On-grid system with wind and solar for EV charging, global agenda support</td></tr><tr><td>Economic and Environmental Impact</td><td>✓ Case studies on economic viability, power management, and environmental impact</td><td>✗ Limited to design considerations and performance evaluation</td><td>✗ Limited to design procedure and experimental prototype testing</td><td>✓ Modified MPPT for VRFB charging system, efficiency comparisons</td><td>✓ Focus on load type, proposed designs, and experimental results</td><td>✓ Optimization results for energy cost, RE share, and grid dependence</td></tr></tbody></table>

Here EV, IoT, Li-ion, MPPT, Ni-Cd, Ni-MH, PV, RE, and VRFB are the acronyms of electric vehicle, internet-of-things, lithium-ion, maximum power point tracking, nickel cadmium, nickel metal hydride, photovoltaic, renewable energy, and vanadium redox flow battery respectively.

sustainable energy solution. Overall, this proposed research contributes valuable insights and practical solutions for addressing diverse power needs in a technologically advanced and environmentally conscious manner.

## Funding statement

The publication of this article has no funding.

## CRediT authorship contribution statement

**Anis ur Rehman:** Writing – original draft, Visualization, Validation, Software, Methodology, Formal analysis, Data curation, Conceptualization. **Ishaq G. Muhammad Alblushi:** Writing – review & editing, Supervision, Investigation, Formal analysis, Data curation, Conceptualization. **Muhammad Fahad Zia:** Writing – original draft, Validation, Supervision, Methodology, Funding acquisition, Formal analysis, Data curation, Conceptualization. **Haris M. Khalid:** Writing – original draft, Supervision, Methodology, Investigation, Funding acquisition, Formal analysis, Conceptualization. **Usman Inayat:** Writing – review & editing, Validation, Investigation, Funding acquisition, Formal analysis, Conceptualization. **Mohamed Benbouzid:** Writing – review & editing, Resources, Project administration, Funding acquisition, Formal analysis, Conceptualization. **S.M. Muyeen:** Writing – review & editing, Validation, Methodology, Investigation, Funding acquisition, Formal analysis, Conceptualization. **Ghulam Amjad Hussain:** Writing – review & editing, Validation, Project administration, Methodology, Investigation, Formal analysis, Conceptualization.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Data availability statement

The data will be made available on request.

## References

[1] M. Tomašov, M. Straka, D. Martinko, P. Bracinfk, L. Buzna, A feasibility study of profiting from system imbalance using residential electric vehicle charging infrastructure, Energies 16 (23) (2023) http://dx.doi.org/10.3390/en16237820, Art. no. 23.

[2] R.D.N. Aditama, N. Ramadhani, T. Ardriani, J. Furqani, A. Rizqiawan, P.A. Dahono, New modular multilevel DC-DC converter derived from modified buck-boost DC-DC converter, Energies 16 (19) (2023) http://dx.doi.org/10.3390/en16196950, Art. no. 19.

[3] A. Chmielewski, P. Piórkowski, J. Mozaryn, S. Ozana, Sustainable development of operational infrastructure for electric vehicles: A case study for Poland, Energies 16 (11) (2023) http://dx.doi.org/10.3390/en16114528, Art. no. 11.

[4] D. Petreus, T. Patarau, E. Szilagyi, M. Cirstea, Electrical vehicle battery charger based on smart microgrid, Energies 16 (9) (2023) http://dx.doi.org/10.3390/en16093853, Art. no. 9.

[5] J. Vujasinović, G. Savić, M. Prokin, Model-driven developed terminal for remote control of charging station for electric vehicles powered by renewable energy, Electronics 12 (8) (2023) http://dx.doi.org/10.3390/electronics12081769, Art. no. 8.

[6] M. Gerardi, F. Fallucchi, F. Oreccini, Blockchain technology for monitoring energy production for reliable and secure big data, Electronics 12 (22) (2023) http://dx.doi.org/10.3390/electronics12224660, Art. no. 22.

[7] A.U. Rehman, M. Ali, S. Iqbal, S. Habib, A. Shafiq, Z.M.S. Elbarbary, A.B. Bar-nawi, Transition towards a sustainable power system: MA-DA & DC framework based voltage control in high PV penetration networks, Energy Rep. 9 (2023) 5922–5936, http://dx.doi.org/10.1016/j.egyr.2023.05.035.

[8] N. Andrenacci, M. Di Monaco, G. Tomasso, Influence of battery aging on the operation of a charging infrastructure, Energies 15 (24) (2022) http://dx.doi.org/10.3390/en15249588, Art. no. 24.

[9] A.A. Shalaby, M.F. Shaaban, M. Mokhtar, H.H. Zeineldin, E.F. ElSaadany, A dynamic optimal battery swapping mechanism for electric vehicles using an LSTM-based rolling horizon approach, IEEE Trans. Intell. Transp. Syst. 23 (9) (2022) 15218–15232, http://dx.doi.org/10.1109/TITS.2021.3138892.

[10] A.M. Braik, M. Koliou, A novel digital twin framework of electric power infrastructure systems subjected to hurricanes, Int. J. Disaster Risk Reduct. 97 (2023) 104020, http://dx.doi.org/10.1016/j.ijdrr.2023.104020.

[11] A.U. Rehman, M. Ali, S. Iqbal, A. Shafiq, N. Ullah, S.A. Otaibi, Artificial intelligence-based control and coordination of multiple PV inverters for reactive power/voltage control of power distribution networks, Energies 15 (17) (2022) http://dx.doi.org/10.3390/en15176297, Art. no. 17.

[12] Y. Abdullah, Z. Movahedi, Qos-aware and energy data management in industrial IoT, Computers 12 (10) (2023) http://dx.doi.org/10.3390/computers12100203, Art. no. 10.

[13] H. Winata, N. Surantha, Online voltage and degradation value prediction of lead acid battery using gaussian process regression, Appl. Sci. 13 (21) (2023) http://dx.doi.org/10.3390/app132112059, Art. no. 21.
[14] K. Hasan, N. Tom, M.R. Yuce, Navigating battery choices in IoT: an extensive survey of technologies and their applications, Batteries 9 (12) (2023) http://dx.doi.org/10.3390/batteries9120580, Art. no. 12.

[15] Z. Ullah, A.U. Rehman, S. Wang, H.M. Hasanien, P. Luo, M.R. Elkadeem, M.A. Abido, IoT-based monitoring and control of substations and smart grids with renewables and electric vehicles integration, Energy (2023) 128924, http://dx.doi.org/10.1016/j.energy.2023.128924.

[16] M. Farjana, A.B. Fahad, S.E. Alam, M.M. Islam, An IoT- and cloud-based E-waste management system for resource reclamation with a data-driven decision-making process, IoT 4 (3) (2023) http://dx.doi.org/10.3390/iot4030011, Art. no. 3.

[17] G.S. Kuaban, E. Gelenbe, T. Czachórski, P. Czekalski, J.K. Tangka, Modelling of the energy depletion process and battery depletion attacks for battery-powered internet of things (IoT) devices, Sensors 23 (13) (2023) http://dx.doi.org/10.3390/s23136183, Art. no. 13.

[18] S. Tanabe, T. Tanzawa, Battery-assisted battery charger with maximum power point tracking for thermoelectric generator: concept and experimental proof, Electronics 12 (19) (2023) http://dx.doi.org/10.3390/electronics12194102, Art. no. 19.

[19] S. Rabah, A. Zaier, J. Lloret, H. Dahman, Efficiency enhancement of a hybrid sustainable energy harvesting system using HHHOPSO-MPPT for IoT devices, Sustainability 15 (13) (2023) http://dx.doi.org/10.3390/su151310252, Art. no. 13.

[20] P.R. Pillewar, S.N. Patil, M.G. Unde, An implementation of solar PV array based multifunctional electrical vehicle charger, Mater. Today: Proc. 69 (2022) A12-A18, http://dx.doi.org/10.1016/j.matpr.2023.01.003.

[21] K.A. Mohamed Junaid, Y. Sukhi, Y. Jeyashree, A. Jenifer, A. Fayaz Ahamed, PV based electric vehicle battery charger using resonant converter, Renew. Energy Focus 42 (2022) 24–32, http://dx.doi.org/10.1016/j.ref.2022.05.005.

[22] A.A. Hussein, A.A. Fardoun, Design considerations and performance evaluation of outdoor PV battery chargers, Renew. Energy 82 (2015) 85–91, http://dx.doi.org/10.1016/j.renene.2014.08.063.

[23] T.-T. Nguyen, H.W. Kim, G.H. Lee, W. Choi, Design and implementation of the low cost and fast solar charger with the rooftop PV array of the vehicle, Sol. Energy 96 (2013) 83–95, http://dx.doi.org/10.1016/j.solener.2013.07.006.

[24] N. Karami, N. Moubayed, R. Outbib, Analysis and implementation of an adaptive PV based battery floating charger, Sol. Energy 86 (9) (2012) 2383–2396, http://dx.doi.org/10.1016/j.solener.2012.05.009.

[25] S. Taghizadeh, M.J. Hossain, J. Lu, W. Water, A unified multi-functional on-board EV charger for power-quality control in household networks, Appl. Energy 215 (2018) 186–201, http://dx.doi.org/10.1016/j.apenergy.2018.02.006.

[26] J. Li, L.-H. Zhao, A novel synchronous buck topology for battery charger, Procedia Eng. 23 (2011) 684–689, http://dx.doi.org/10.1016/j.proeng.2011.11.2566.

[27] M. Bayoumy, S. El-Hefnaw, O. Mahgoub, A. El-Tobshy, New techniques for battery charger and SOC estimation in photovoltaic hybrid power systems, Sol. Energy Mater. Sol. Cells 35 (1994) 509–514, http://dx.doi.org/10.1016/0927-0248(94)90180-5.

[28] C. Zhao, P. Zhu, N. Zhang, S. Chen, X. Shao, Y. Wang, Directional charging-based scheduling strategy for multiple mobile chargers in wireless rechargeable sensor networks, Ad Hoc Netw. 149 (2023) 103251, http://dx.doi.org/10.1016/j.adhoc.2023.103251.

[29] J. Weimer, N. Weimer, J. Nuzzo, I. Kallfass, High power density battery chargers with fast-charging utilizing heat storage, Appl. Therm. Eng. 232 (2023) 121043, http://dx.doi.org/10.1016/j.applthermaleng.2023.121043.

[30] L. Hou, O.E. Herrera, W. Mérida, Charging scheduling and energy management for mobile chargers in a grid-interactive transportation system, J. Energy Storage 65 (2023) 107305, http://dx.doi.org/10.1016/j.est.2023.107305.

[31] A.U. Rehman, Z. Ullah, A. Shafiq, H.M. Hasanien, P. Luo, F. Badshah, Load management, energy economics, and environmental protection nexus considering PV-based EV charging stations, Energy (2023) 128332, http://dx.doi.org/10.1016/j.energy.2023.128332.

[32] R.G. Allwyn, A. Al-Hinai, V. Margaret, A comprehensive review on energy management strategy of microgrids, Energy Rep. 9 (2023) 5565–5591, http://dx.doi.org/10.1016/j.egyr.2023.04.360.

[33] P.K. Kushwaha, C. Bhattacharjee, Integrated techno-economic-enviro-socio design of the hybrid renewable energy system with suitable dispatch strategy for domestic and telecommunication load across India, J. Energy Storage 55 (2022) 105340, http://dx.doi.org/10.1016/j.est.2022.105340.

[34] A.U. Rehman, A. Shafiq, Z. Ullah, S. Iqbal, H.M. Hasanien, Implications of smart grid and customer involvement in energy management and economics, Energy (2023) 127626, http://dx.doi.org/10.1016/j.energy.2023.127626.

[35] A.A. Hussein, A.A. Fardoun, Design considerations and performance evaluation of outdoor PV battery chargers, Renew. Energy 82 (2015) 85–91, http://dx.doi.org/10.1016/j.renene.2014.08.063.

[36] T.-T. Nguyen, H.W. Kim, G.H. Lee, W. Choi, Design and implementation of the low cost and fast solar charger with the rooftop PV array of the vehicle, Sol. Energy 96 (2013) 83–95, http://dx.doi.org/10.1016/j.solener.2013.07.006.

[37] A. Bhattacharjee, H. Samanta, N. Banerjee, H. Saha, Development and validation of a real time flow control integrated MPPT charger for solar PV applications of vanadium redox flow battery, Energy Convers. Manage. 171 (2018) 1449–1462, http://dx.doi.org/10.1016/j.enconman.2018.06.088.

[38] N. Karami, N. Moubayed, R. Outbib, Analysis and implementation of an adaptive PV based battery floating charger, Sol. Energy 86 (9) (2012) 2383–2396, http://dx.doi.org/10.1016/j.solener.2012.05.009.

[39] P. Zheng, Z. Fang, H. Li, Y. Pan, D. Luo, Z. Zhang, Multi-objective optimization of hybrid energy management system for expressway chargers, J. Energy Storage 54 (2022) 105233, http://dx.doi.org/10.1016/j.est.2022.105233.