Concepts and Experiments on More Electric Aircraft Power Systems

Abstract

The evolution of aircraft power systems has been driven by increasing electrical demands and advancements in aviation technology. Background: This study provides a comprehensive review and experimental validation of on-board electrical network development, analyzing power management strategies in both conventional and modern aircraft, including the Mi-24 helicopter, F-22 multirole aircraft, and Boeing 787 passenger airplane. Methods: The research categorizes aircraft electrical systems into three historical phases: pre-1960s with 28.5 V DC networks, up to 2000 with three-phase AC networks (3 × 115 V/200 V, 400 Hz), and post-2000 with 270 V DC networks derived from AC generators via transformer–rectifier units. Beyond theoretical analysis, this work introduces experimental findings on hybrid-electric aircraft power solutions, particularly evaluating the performance of the Modular Power System for Aircraft (MPSZE). The More Electric Aircraft (MEA) concept is analyzed as a key innovation, with a focus on energy efficiency, frequency stability, and ground power applications. The study investigates the integration of alternative energy sources, including photovoltaic-assisted power supplies and fuel-cell-based auxiliary systems, assessing their feasibility for aircraft system checks, engine startups, field navigation, communications, and radar operations. Results: Experimental results demonstrate that hybrid energy storage systems, incorporating lithium-ion batteries, fuel cells, and photovoltaic modules, can enhance MEA efficiency and operational resilience under real-world conditions. Conclusions: The findings underscore the importance of MEA technology in the future of sustainable aviation power solutions, highlighting both global and Polish research contributions, particularly from the Air Force Institute of Technology (ITWL).

1. Introduction

1.1. Scope and Objectives of the Study

The increasing electrification of aircraft systems has significantly influenced the development of on-board electrical power networks. Over the past decades, aviation has transitioned from traditional hydraulic and pneumatic systems to more electric architectures, driven by the need for higher efficiency, reduced fuel consumption, and improved reliability. This transformation is particularly evident in modern aircraft such as the Mi-24 helicopter, F-22 multirole fighter, and Boeing 787, which have adopted advanced power distribution strategies. Despite these advancements, the shift towards the More Electric Aircraft (MEA) concept remains an ongoing challenge, with many aspects of power system integration still underexplored.

Our contribution lies in a systematic examination of aircraft power system evolution with a novel emphasis on the integration of renewable energy sources. We evaluate the feasibility of photovoltaic and fuel-cell-based power solutions in aviation, particularly in supporting system checks, engine startup, and ground-based operations such as navigation, and radar applications. Furthermore, this study incorporates original insights from research conducted at the Air Force Institute of Technology (ITWL), presenting new data and comparative assessments of emerging energy-efficient technologies.

In addition to addressing on-board power system transformations, this study investigates the role of Mobile Field Power Stations (MPSZE) and aviation operations. With the increasing complexity of aircraft energy requirements, mobile and modular power solutions have emerged as critical components in ensuring operational flexibility. These systems not only provide supplementary power for maintenance and pre-flight checks but also enhance the self-sufficiency of deployed air units in remote areas. An in-depth analysis of MPSZE configurations and simulation-based validation is included, highlighting their significance in applications such as supporting communication infrastructure, radar systems, and advanced electronic warfare capabilities.

Furthermore, the study examines the potential impact of emerging battery technologies, including solid-state and lithium–sulfur chemistries, on the next generation of More Electric Aircraft. As energy storage remains a key bottleneck in achieving fully electric flight, ongoing advancements in battery performance, safety, and longevity could reshape the feasibility of hybrid-electric and all-electric aircraft architectures.

By bridging the existing research gap, this paper not only highlights critical advancements in aircraft power distribution but also proposes new directions for integrating sustainable energy solutions into modern aviation. The findings contribute to ongoing discussions on energy efficiency in aircraft systems, offering practical insights into the future of MEA development, the role of renewable energy, and the operational benefits of mobile power solutions.

1.2. Challenges and Innovations in Aircraft Electrification

While extensive research has been conducted on conventional electrical architectures, a significant gap remains in analyzing the transition from legacy AC to high-voltage DC architectures, particularly regarding energy efficiency, power stability, and real-world implementation challenges. Moreover, existing studies often focus on large commercial and small touristic aircraft, leaving hybrid-electric and fully electric power solutions for specialized aviation applications underexplored. Additionally, while photovoltaic and fuel cell technologies have been considered in aviation, their integration into operational aircraft power systems, particularly in off-grid and mobile applications, remains fragmented.

This study addresses these research gaps by providing a comprehensive analysis of the historical evolution, current state, and future trends in aircraft power systems, with a distinct focus on experimental validation and hybrid energy integration. Unlike previous works that primarily discuss theoretical MEA advancements, this paper presents novel contributions, including:

• Experimental assessment of a modular mobile power station (MPSZE) for aviation applications, validating its role in aircraft pre-flight diagnostics, auxiliary power, and emergency energy supply.
• Detailed frequency stability analysis, evaluating transient behavior and energy distribution in both conventional and hybrid-electric aircraft architectures.
• Optimization of hybrid power solutions by integrating high-capacity batteries, fuel cells, and photovoltaics to enhance system resilience and sustainability in real-world conditions.

By bridging the gap between theoretical research and experimental implementation, this work offers new insights into sustainable aircraft electrification and power system efficiency, with direct implications for future aviation energy strategies. The findings contribute to optimizing on-board power distribution, improving energy reliability, and enhancing the feasibility of alternative energy sources in aviation.

1.3. Article Structure

This paper is structured as follows:

• Section 2 provides a comprehensive literature review, covering the evolution of aircraft power systems, the transition to More Electric Aircraft (MEA), and the potential of alternative energy sources such as photovoltaics and fuel cells.
• Section 3 presents experimental analyses, including system stability assessments and the integration of renewable energy solutions in aviation applications.
• Section 4 discusses the implications of the findings, highlighting technological challenges and opportunities for the future of aircraft electrification.
• Section 5 concludes the study by summarizing key insights and proposing directions for future research.

2. Literature Review

2.1. Evolution of Aircraft Electrical Power Systems

The development of aircraft power systems has experienced considerable transformation, especially with the introduction of the More Electric Aircraft (MEA) concept. This literature review integrates recent advancements and comparative analyses of diverse aircraft power systems, emphasizing the shift from conventional hydraulic and pneumatic systems to predominantly electric architectures.

Historically, aviation power systems have predominantly utilized hydraulic and pneumatic mechanisms for various functions, such as actuation and environmental control. Nevertheless, the More Electric Aircraft paradigm advocates for the electrification of these systems, demonstrating an improvement in operational efficiency, a reduction in weight, and a decrease in maintenance costs [1]. The shift towards electric systems is not simply a gradual modification but constitutes a foundational reconfiguration of aircraft architecture, requiring a thorough understanding of electrical power generation and distribution [2,3].

Several recent studies have expanded the understanding of MEA architectures, focusing on energy management, power electronics, and hybrid-electric solutions. The study [4] explored innovative power distribution topologies for high-voltage DC systems in next-generation aircraft, highlighting the advantages of advanced semiconductor technologies and fault-tolerant architectures. Unlike previous designs, where aircraft systems primarily relied on AC networks (3 × 115 V, 400 Hz), emerging architectures emphasize the use of 270 V or higher DC voltage levels to improve power density and reduce wiring mass.

Research conducted under the Clean Sky 2 initiative focuses on the development and validation of fully electric propulsion systems, emphasizing the importance of advanced simulation platforms for optimizing energy management strategies [5]. The progression toward MEA is necessitated by the imperative to mitigate environmental impacts and enhance the performance of aircraft. The incorporation of electric propulsion systems constitutes a fundamental component of this evolution, as it permits reductions in noise and emissions [6,7].

Compared to these works, our study extends the analysis by integrating real-world experimental results on aircraft power stability and transient behavior. Unlike theoretical studies that rely on modeling, our work presents a direct evaluation of hybrid energy sources, including fuel cells and modular mobile power stations, in operational scenarios.

Contemporary research suggests that the requirement for electrical power aboard aircraft has markedly escalated, prompting the design of sophisticated electrical power generation systems. For example, the implementation of High-Voltage Direct Current (HVDC) systems has been advocated to improve efficiency and reliability while decreasing weight [8]. This transition is additionally bolstered by advancements in power electronics, which enable the integration of various electrical components, including electromechanical actuators and energy storage systems [9].

Furthermore, the comparative analysis of power systems indicates that the MEA architecture presents several benefits over conventional systems. For instance, the removal of hydraulic systems streamlines aircraft design and diminishes potential failure points, thereby improving reliability [7,9]. Moreover, the MEA concept facilitates more flexible power management and distribution, which is essential for the integration of hybrid propulsion systems [10]. The design methodology for on-board electrical power systems has been developed to accommodate these modifications, concentrating on optimizing power matching between propulsion and on-board systems [11].

Despite the numerous advantages, the transition to MEA is not without challenges [12]. The increased complexity of electrical systems requires robust fault detection and management strategies to ensure safety and reliability [13]. Furthermore, the introduction of variable frequency power systems raises concerns about harmonic distortion and power quality, which must be addressed to maintain system performance [14]. As highlighted by [15], the development of mathematical models and simulations for on-board power systems is essential to understand and mitigate these challenges [16].

Summarizing, the development of electrical systems in aircraft has come a long way, as illustrated in Figure 1, which shows the gradual transition from simple power supply systems to advanced, fully electric solutions used in modern aviation [17,18].

Traditional aircraft power systems were based on low-voltage direct current (28 V DC) systems, used in older designs such as the Su-22 and Mi-8. However, the use of commutator-based generators limited their maximum power output to 26 kW, leading to efficiency issues and increased system weight.

The advancement of aviation in the 1970s and 1980s led to the transition to three-phase alternating current (AC) generators, as seen in the F-16, which enabled higher power output and improved reliability of on-board systems. In the Lockheed Martin F-22 Raptor, AC generators and transformer–rectifier units operating at 270 V provide up to 100 kW of power.

Modern aircraft utilize several redundant electrical power generators, including:

• Main Generators (MGs) (Figure 2),
• Auxiliary Power Units (APUs), used during ground operations and as a backup power source,
• Ram Air Turbines (RATs), deployed in emergency situations.

The implementation of high-voltage DC (270 V/540 V DC) systems has significantly reduced the weight of electrical wiring, which is one of the key factors in improving the energy efficiency of modern aircraft.

The main source of electricity on an aircraft is a power generator (Figure 2). The generator is driven via a gearbox or drive shaft. In modern engine designs, it is common to find the so-called Integrated Drive Generator (IDG), which is a generator integrated with a hydraulic gearbox that allows the engine to maintain a constant speed regardless of changes in turbine engine speed. The IDG is present on the CFM LEAP engine, among others, and is the reason for the slight bulge that can be observed at the bottom of the engine nacelle.

The principle of the generator is based on electromagnetic induction. Current flows through the rotor, creating an electromagnetic field that induces a voltage on the stator windings. To ensure stable and safe operation of the generator, a generator control unit is used. As a result of the work of the listed elements, an alternating current of the desired voltage and frequency is obtained at the output.

2.2. Role of More Electric Aircraft in Modern Aviation

The concept of the More Electric Aircraft (MEA) originally emerged under pressure from environmental groups advocating for the reduction in greenhouse gas emissions produced by air transportation [19,20]. The introduction of government subsidies and financial incentives accelerated the development of modern electrical technologies in aviation. This not only improved the reliability of on-board systems but also increased the aircraft payload capacity.

The MEA concept emphasizes the replacement of traditional pneumatic and hydraulic systems with electrical solutions, leading to mass reduction, increased reliability, and improved energy efficiency in aircraft.

Examples of MEA Applications in Modern Aircraft

The shift to More Electric Aircraft (MEA) has led to significant advancements in propulsion and auxiliary systems, including the replacement of turbine-driven fan engines with high-voltage (1000 V) electric motors. Pratt and Whitney’s electric taxiing system, powered by the Auxiliary Power Unit (APU), enables low-emission taxiing and eliminates the inefficiencies of traditional fan turbines at low speeds, which result in excessive fuel consumption and emissions [21].

Historically, aircraft relied on centralized hydraulic systems, which were heavy and prone to failure. The introduction of distributed electrohydraulic systems, first implemented in the 1970s (e.g., MiG-29), significantly reduced system weight and improved reliability. Today, fully electric systems are increasingly used for landing gear operation, flap and aileron control, and wing angle adjustment, further reducing aircraft weight and simplifying on-board systems. The transition to MEA has also led to a substantial increase in on-board power requirements. This demand is driven by the replacement of pneumatic and hydraulic systems with electric alternatives, as well as the growing need for passenger comfort features such as air conditioning, kitchen facilities, and in-flight entertainment. Additionally, advanced automation and navigation systems contribute to higher power consumption.

To manage this increased demand, modern aircraft incorporate advanced Power Distribution Systems (PDSs), which monitor, analyze, and dynamically switch power sources to optimize energy usage and enhance flight safety. The implementation of PDS has resulted in reduced actuator system weight, increased reliability, simplified maintenance, lower operational costs, and improved overall safety.

Aircraft generator technology has also evolved over time. Early aircraft used 28 V DC dynamos, which were eventually replaced by AC systems due to their high current intensity and cable weight. The F-16 transitioned to three-phase AC generators, while the F-22 Raptor adopted 270 V DC generators with transformer–rectifier units, capable of providing up to 100 kW of power [11]. Modern aircraft now utilize multiple independent power generators, including main generators, APU-powered generators for ground operations and backup power, and emergency Ram Air Turbines (RATs) for critical situations. These advancements have contributed to greater efficiency, reliability, and operational flexibility in modern aviation [22].

As an example of the possibility of building a more electric aircraft, the AOS 71 (Figure 3) and AOS H2 are gliders with electric and hybrid propulsion systems. The former is a pure electric design, while the latter is a hybrid, with a battery unit and a hydrogen fuel cell as the energy source.

The propulsion unit uses batteries and a hydrogen fuel cell as an energy source to power the EMRAX 268’s marching engine. The motor glider’s propulsion unit uses electricity from both the hydrogen fuel cell and the battery unit during takeoff. After maneuvers, such as takeoff and ascent, that require a higher energy demand, requiring additional power drawn from the battery, the flight is performed using the fuel cell. If conditions permit, the excess electricity produced is used to recharge the batteries.

2.3. Assessment of Energy Demand in Modern Aircraft

2.3.1. Energy Requirements of Rotorcraft Platforms

The energy requirements of rotorcraft platforms are dictated by the unique aerodynamic and operational characteristics of helicopters. Unlike fixed-wing aircraft, rotorcraft rely on rotary-wing lift generation, which necessitates continuous high-power demand from on-board electrical systems. Additionally, the increasing complexity of modern rotorcraft, with the integration of more electric systems (MES), avionics, and auxiliary subsystems, has led to a growing need for efficient power generation, storage, and distribution.

The energy requirements of rotorcraft platforms are a crucial area of research, especially as aviation moves toward more efficient and sustainable solutions. Unlike fixed-wing aircraft, rotorcraft require continuous energy delivery to sustain hover, vertical takeoff and landing (VTOL) [23,24], and maneuverability, all of which demand significant power. Key factors influencing rotorcraft energy consumption include power-to-weight ratio, fuel efficiency, propulsion system advancements, and material innovations aimed at reducing overall energy demands.

A fundamental parameter in rotorcraft performance is the power-to-weight ratio, which directly impacts hover capability, climb rate, and efficiency. Conventional helicopters typically exhibit power-to-weight ratios between 0.1 and 0.3 kW/kg. For example, the Sikorsky S-76, a medium-sized helicopter, has a maximum takeoff weight (MTOW) of 3175 kg and an engine output of 1000 kW, resulting in a power-to-weight ratio of 0.31 kW/kg. Similarly, the Bell 206 Jet Ranger has an MTOW of 1450 kg and an engine output of 310 kW, yielding a power-to-weight ratio of 0.21 kW/kg. The emergence of hybrid-electric propulsion (HEPS) is expected to improve these figures, with hybrid designs achieving ratios of up to 0.43 kW/kg, enhancing flight endurance while reducing fuel dependency.

Fuel consumption is another critical factor. Conventional gas turbine engines in rotorcraft consume fuel at rates ranging from 0.2 to 0.25 kg/s during a cruise, with aircraft such as the Bell 206 JetRanger consuming approximately 720 kg of fuel over a 2 h flight, while the Eurocopter EC135 requires 900 kg over the same period. This fuel consumption directly affects operational costs and environmental impact, as each kilogram of fuel burned emits approximately 3.15 kg of CO₂. A Bell 206 JetRanger produces around 360 kg of CO₂ emissions during a typical 2 h flight. In contrast, hybrid-electric propulsion systems have demonstrated the potential to reduce fuel consumption and emissions by up to 50%, depending on mission profile and battery integration.

One of the greatest challenges facing electric rotorcraft is the energy density of propulsion systems. Conventional Jet A-1 aviation fuel provides an energy density of 43 MJ/kg, whereas lithium-ion batteries only offer around 250 Wh/kg (0.9 MJ/kg), which is nearly 50 times lower than traditional fuels. This limitation makes it difficult for fully electric rotorcraft to achieve operational ranges comparable to their fuel-powered counterparts. As a result, hybrid-electric configurations combining turbine engines with high-capacity battery storage have been explored to improve energy efficiency. Studies indicate that such hybrid systems can reduce fuel consumption by up to 30%, with combined power outputs reaching 1500 kW, supporting aircraft with an MTOW of 3500 kg.

Advancements in variable rotor speed (VRS) control and hybrid-electric propulsion have further contributed to optimizing rotorcraft energy consumption. By dynamically adjusting rotor speeds during cruise and hover transitions, these technologies can significantly reduce energy losses and improve efficiency. Additionally, solar-assisted power systems have been studied to extend flight endurance and reduce reliance on fossil fuels. However, integrating solar cells into rotorcraft structures presents aerodynamic challenges, requiring further research to ensure practical implementation.

Material advancements also play a crucial role in optimizing rotorcraft energy efficiency. The adoption of lightweight composite materials, such as carbon fiber and hybrid composite, reduces structural weight while enhancing mechanical properties. High-strength materials enable a 10–20% reduction in overall aircraft weight, leading to proportional decreases in power consumption. Improved structural damping through hybrid materials has also been shown to reduce vibration-induced energy losses, further enhancing overall efficiency.

The energy requirements of rotorcraft platforms are influenced by a combination of power-to-weight ratios, fuel consumption, propulsion efficiency, and material innovations [25]. The ongoing development of hybrid-electric propulsion, variable rotor speeds, and lightweight materials is essential for optimizing rotorcraft performance while reducing environmental impact. These advancements will shape the future of rotorcraft technology, driving the industry toward more efficient, sustainable, and high-performance aviation solutions.

2.3.2. Power Consumption in Systems and Ground Infrastructure

The power consumption of rotorcraft systems and their associated ground infrastructure is a critical aspect of their operational efficiency and environmental impact. As rotorcraft technology advances, particularly with the integration of electric and hybrid-electric systems, understanding the energy requirements of both the aircraft and the supporting infrastructure becomes increasingly important.

Rotorcraft systems, particularly those utilizing electric propulsion, exhibit varying power consumption profiles depending on their operational modes. For instance, electric vertical takeoff and landing (eVTOL) aircraft typically require power outputs ranging from 100 kW to 500 kW during hover, with energy consumption rates that can reach approximately 0.5 to 1.5 kWh per mile during cruise flight [23].

This translates to significant energy demands, especially for missions involving multiple takeoffs and landings. The energy consumption of these systems is compounded by the need for efficient battery management and power distribution systems, which can account for an additional 10–20% overhead in energy use due to conversion losses and auxiliary systems [26].

The ground infrastructure necessary to support rotorcraft operations, particularly electric and hybrid-electric models, is crucial for optimizing energy consumption. Charging stations for electric rotorcraft must be strategically located to minimize downtime and ensure rapid recharging capabilities. Research indicates that the installation of fast-charging stations can reduce the average charging time to approximately 30 min for a full charge, which is essential for maintaining operational efficiency [27]. Furthermore, the design of these infrastructures must consider the electrical load requirements, which can vary significantly based on the number of simultaneous charging operations. For example, a single charging station may require a power supply of up to 1 MW to accommodate multiple rotorcraft charging simultaneously.

To enhance the efficiency of ground infrastructure, various energy optimization methodologies have been proposed. For instance, proactive energy-aware auto-scaling solutions can dynamically adjust the power supply based on real-time demand, significantly reducing energy waste [26]. Additionally, integrating renewable energy sources, such as solar panels, into the ground infrastructure can further decrease reliance on conventional power grids and lower operational costs. A fully solar-powered charging station can potentially reduce energy costs by 30–50%, depending on local solar irradiance conditions [28].

The environmental implications of rotorcraft power consumption are significant, particularly in urban environments where noise and emissions are critical concerns. The transition to electric and hybrid-electric rotorcraft is expected to reduce greenhouse gas emissions by 50–70% compared to traditional fuel-powered systems [29]. However, the overall sustainability of rotorcraft operations also hinges on the energy sources used in ground infrastructure. The integration of low-carbon technologies, such as hydrogen fuel cells or renewable energy systems, is essential for achieving net-zero emissions in rotorcraft operations.

As rotorcraft technology continues to evolve, the development of smart grid solutions that can integrate with rotorcraft charging infrastructure will be crucial. These systems can optimize energy distribution based on demand, supply fluctuations, and grid conditions, thereby enhancing the overall efficiency of rotorcraft operations [30]. Additionally, ongoing research into decentralized energy management systems for UAV base stations indicates promising avenues for improving energy utilization and operational efficiency in rotorcraft ground infrastructure [31].

The power consumption of rotorcraft systems and their ground infrastructure is a multifaceted issue that requires careful consideration of energy efficiency, environmental impact, and technological advancements. As the industry moves towards more sustainable aviation solutions, optimizing both rotorcraft and their supporting infrastructure will be paramount.

2.4. Alternative Energy Sources for Aviation

The integration of photovoltaic systems in aviation has garnered increasing attention as the industry seeks sustainable energy solutions to mitigate environmental impacts. This literature review synthesizes key studies that focus on the modeling and simulation of photovoltaic integration in aviation, highlighting advancements in technology and methodologies.

In the early 2010s, research began to explore the feasibility of integrating photovoltaic systems into aviation applications. For instance, ref. [32] emphasized the need for sustainable energy solutions in aviation, laying the groundwork for subsequent studies on renewable energy integration.

Following this, ref. [33] presented a finite element simulation approach to analyze temperature distribution in photovoltaic modules, which is critical for optimizing their performance in the unique environmental conditions encountered in aviation. This study highlighted the importance of thermal management in photovoltaic systems, a recurring theme in later research.

As the field progressed, ref. [14] examined energy acquisition capabilities of solar-powered aircraft, focusing on the impact of photovoltaic arrays on overall performance. The exploration of hybrid systems also gained traction, with ref. [34] discussing agrivoltaic systems to optimize land use while generating renewable energy, suggesting potential applications in airport environments.

In more recent studies, ref. [35] analyzed the feasibility of adding grid-connected hybrid photovoltaic systems to reduce electrical loads in aviation settings, demonstrating the practical implications of photovoltaic integration. Additionally, ref. [36] focused on the simulation of photovoltaic systems in aviation, emphasizing the importance of accurate modeling for effective integration.

Furthermore, ref. [37] presented a novel framework for designing solar-powered UAVs, utilizing genetic algorithms to optimize various design parameters, which illustrates the growing sophistication of modeling techniques in this domain.

3. Materials and Methods

3.1. Research Methodology and Data Source

This study employed a combination of experimental testing and analytical evaluation to assess the performance of the MPSZE mobile energy storage system in an off-grid aviation environment. The research focused on frequency stability, transient response, and power distribution efficiency under real-world operating conditions.

The experimental setup involved testing the MPSZE system during the cold engine start of the helicopter. The system was configured with 12 lead–acid batteries (Q = 600 Ah), operating without support from photovoltaic panels (S) or external power sources (U). Data were collected under two operational conditions:

• Standard mode (without feedback stabilization)—to analyze voltage drops and transient fluctuations.
• Enhanced mode (with feedback stabilization)—to assess the role of the transformer–rectifier unit in stabilizing power output.

The data sources include the following:

• Direct system measurements of frequency, voltage, and power stability recorded using precision monitoring equipment.
• Comparative frequency analysis, evaluating key frequency parameters such as nominal frequency, peak fluctuations, and long-term drift.
• Transient response analysis, comparing system behavior with and without feedback stabilization to highlight voltage stabilization effectiveness.

The methodology ensures that the study captures both real-time power fluctuations and long-term stability trends, providing a comprehensive assessment of the MPSZE system’s reliability in aviation applications. Further testing under in-flight conditions and alternative battery technologies could enhance the scope of future research.

3.2. Experimental Setup of Photovoltaic-Assisted Aircraft Power Systems

Modern aircraft power systems require stable and efficient energy sources that can adapt to variable operational conditions. Traditional solutions rely on mobile power generators and electromechanical converters, which draw energy from industrial grids or fuel combustion. While these systems are reliable, they come with high operational costs, noise emissions, and environmental impact. An alternative approach involves the integration of renewable energy sources, such as photovoltaics [35], which can enhance energy efficiency and reduce the carbon footprint [38]. In the context of More Electric Aircraft and hybrid-electric propulsion systems, photovoltaic technology is being evaluated as a supplementary power source to improve overall energy efficiency and extend operational capabilities.

The use of photovoltaic panels in aircraft power systems presents opportunities for fuel consumption reduction and greater energy independence. By generating electricity without emissions and operating silently, photovoltaic technology offers a promising alternative to conventional power sources. Figure 4 illustrates flexible photovoltaic panels installed and tested at the ITWL site in December 2023, as part of research on integrating solar energy into aviation energy storage and distribution systems.

These panels were examined under real-world operating conditions to assess their potential application in various aircraft power scenarios:

• Ground operations—supplying auxiliary loads during maintenance, reducing dependency on external power sources.
• Emergency backup power—supporting critical electronic systems in case of generator failure.
• Hybrid energy storage systems—working in combination with lithium-ion batteries and supercapacitors to optimize energy efficiency.

However, its application faces significant technological challenges, particularly in handling dynamic load fluctuations. Photovoltaic panels have high internal resistance, leading to substantial voltage drops during sudden spikes in power demand. This limitation affects their ability to function as a primary power source in aircraft electrical networks. This limits their ability to directly supply energy in high-load scenarios, such as engine startup or the activation of high-power on-board systems.

Studies show that despite their advantages, photovoltaic systems alone cannot provide stable voltage and required power under conditions of large load variations. During abrupt changes in power demand, voltage transients can occur, which, without proper regulation mechanisms, may cause instability in electrical power systems. Experimental tests have shown that, when load demand fluctuated between 5% and 85%, transient voltage drops of up to 20% were recorded, affecting the performance of energy-consuming components.

To mitigate these effects, hybrid energy storage solutions, such as lithium-ion batteries and supercapacitors, are essential for successfully integrating photovoltaic systems into aviation applications. These energy storage solutions play a crucial role in absorbing rapid fluctuations in power demand and preventing voltage instability.

Photovoltaic technology has the potential to complement aircraft power systems effectively, but its full-scale implementation requires further research into energy storage optimization and advanced power management algorithms. One of the most effective strategies involves combining photovoltaic panels with energy storage solutions to stabilize energy output. The combination of photovoltaic panels with battery storage and supercapacitors significantly enhances the reliability of hybrid energy systems.

Future research should focus on the following:

• Energy storage optimization—improving battery–supercapacitor hybrid systems for enhanced stability.
• Advanced power management algorithms—intelligent energy flow control to regulate power fluctuations.
• Flexible photovoltaic panel integration—testing on various aircraft types to optimize efficiency in real-world conditions.

In the future, further development of high-efficiency energy storage solutions and intelligent energy management systems may position photovoltaics as a key component of next-generation aircraft electrical power systems.

3.3. Fuel-Cell-Based Auxiliary Power Solutions for Aviation

Hydrogen fuel cells, particularly Proton Exchange Membrane (PEM) fuel cells, are increasingly discussed in technical literature as a promising energy source for electric propulsion. Various land-based and aviation applications have demonstrated the viability of fuel-cell-powered electric propulsion, including the Toyota Mirai (Gen 2), the Hyundai Nexo (2018), and the XCIENT Fuel Cell truck (2020). In the aviation sector, notable examples include the Boeing HK36 Super Dimona, Airbus E-Fan, hybrid and electric gliders such as AOS 71, and even fuel-cell-powered locomotives.

One of the earliest demonstrations of hydrogen fuel cell applications in aviation was the Boeing Phantom Works demonstrator, which used a PEM fuel cell for level flight while relying on a lithium-ion battery for takeoff. A key milestone was achieved with the Boeing HK36 Super Dimona, modified to incorporate a PEM fuel cell. Flight tests in Madrid in 2008 demonstrated that, after reaching cruising altitude, the aircraft could sustain level flight solely on fuel cell power, marking the first-ever use of hydrogen fuel cells as a primary energy source for sustained flight.

Further advancements came with the Airbus E-Fan project, initiated in 2014. This aircraft, designed as a test platform for zero-emission jet propulsion, featured twin ducted electric fans powered by 30 kW electric motors and a lithium–polymer battery pack. By 2020, Airbus introduced an extended-range version incorporating a combustion engine-driven generator, paving the way for the E-Fan X concept, a hybrid-electric passenger aircraft where a traditional jet engine is supplemented by an electric motor powered by the aircraft’s on-board power generation system.

Another key research initiative involved hybrid and electric gliders, such as the AOS 71 and AOS H2, developed through collaboration between Rzeszow University of Technology and Warsaw University of Technology. The AOS H2 features a hybrid powertrain combining a lithium-ion battery pack and a hydrogen fuel cell developed with the AGH University of Science and Technology. During takeoff and climb phases—requiring high power—the system draws from both the fuel cell and battery pack. Once in cruise mode, the battery is disconnected, and surplus energy generated by the fuel cell can be used to recharge it, enhancing overall efficiency. Power electronics, including inverters and converters, play a crucial role in integrating different voltage and current types, ensuring optimal performance across various power demands.

One of the key advantages of fuel cell propulsion is its clean byproducts—water vapor and heat—which can be repurposed for cabin heating or battery temperature management. However, challenges remain, particularly concerning hydrogen storage. The need for high-purity hydrogen and the requirement for high-pressure storage (300 atm) pose logistical and safety challenges. Hydrogen’s small molecular size makes it prone to leakage, and if not properly dispersed, it could pose explosion risks. Experts suggest effective ventilation systems to mitigate these hazards, as hydrogen dissipates quickly when released.

Given these constraints, methanol-based fuel cells (DMFCs) have emerged as an alternative, particularly in industrial applications. Companies such as GaonCell (Jeonbuk, Republic of Korea) and SIQENS (Munich, Germany) have developed DMFC power systems that use methanol as a hydrogen carrier. This allows for easier storage and transport, addressing some of the logistical challenges associated with hydrogen. ThyssenKrupp Marine Systems has already integrated methanol reforming systems into submarines, producing hydrogen on-board and feeding it into PEM fuel cells. Similarly, GaonCell has deployed DMFC-powered forklifts, demonstrating the feasibility of methanol fuel cells in high-power applications.

One of the directions being developed at AFIT is the development of a prototype of a mobile power system for aircraft and helicopters at the output voltage of 230 V, 50 Hz. Figure 5 presents the latest version of this system, which has been tested under real-world operational conditions to evaluate its efficiency in aviation applications.

The MPSZE (Mobile Field Power Station for Aviation) is designed as a modular energy storage and distribution system that can operate off-grid or as a backup power unit. Unlike traditional Auxiliary Power Units (APUs), which rely on combustion engines, this system integrates fuel cell technology and lithium-ion battery storage to improve efficiency and reduce emissions. The MPSZE system was developed with the goal of providing stable power for aircraft electrical systems during maintenance, pre-flight checks, and emergency scenarios.

The MPSZE prototype was tested on multiple aircraft platforms, including rotary-wing (helicopters) and fixed-wing aircraft, to validate its effectiveness. The system has been utilized in the following scenarios:

• Pre-flight electrical system checks—powering avionics and diagnostic tools without starting the main engines.
• Emergency backup power—providing stable 230 V AC supply in case of on-board power failures.
• Ground operations support—enabling maintenance teams to conduct electrical system diagnostics with an independent power source.

The MPSZE system consists of:

• Fuel cell power unit (PEM technology)—supplying continuous power without CO₂ emissions.
• Lithium-ion battery pack (48 V, 10 kWh)—acting as an energy buffer to stabilize transient loads.
• Inverter unit (6 kW, 230 V AC, 50 Hz)—converting stored energy to aircraft-compatible voltage.
• Integrated control module with an energy management system—optimizing fuel cell and battery operation based on demand.

A key challenge in early testing was voltage instability during transient states, particularly when switching between battery and fuel cell power sources. To address this, the system was upgraded with an active power stabilization mechanism, which significantly reduced voltage fluctuations by 30% during load changes.

As aircraft become more electric, fuel-cell-based auxiliary power solutions are gaining traction as an alternative to conventional APU systems, offering reduced emissions and increased efficiency. The next phase of testing will involve integration with hybrid-electric propulsion systems to assess compatibility with next-generation aircraft architectures.

Future developments in methanol-reforming and fuel cell integration could play a critical role in advancing hybrid-electric and fully electric aircraft architectures, enhancing their range, reliability, and overall sustainability. Further optimization will focus on increasing power density, improving fuel cell startup times, and refining the system’s energy management algorithms for greater operational efficiency.

3.4. Simulation and Validation of Modular Power Systems

Following initial laboratory tests and real-world trials, the system underwent significant upgrades to enhance its electrical and mechanical performance. A key challenge was voltage instability during transient states, leading to an increase in battery capacity from 8 to 12 batteries. During startup, the system operates with two independent battery sections:

1.

Main “Passive” Section (Section A)

• 8 × 12 V lead–acid batteries (100 Ah each)
• Directly supplies the DC output cable

2.

Auxiliary “Active” Section (Section B)

• 4 × 12 V lead–acid batteries (100 Ah each)
• Supports the AZO DIGITAL 6 kW-24 inverter

During startup, a switching system (Contactors: S1, S2, S3) isolates the two battery sections, optimizing power flow. Figure 6 presents the EMI filter and its integration into the system’s power stabilization mechanism.

The EMI (Electromagnetic Interference) filter, shown in Figure 6, plays a critical role in maintaining the stability of the output voltage (230 V AC, 50 Hz). This component is essential for suppressing high-frequency noise and preventing power fluctuations that could interfere with on-board electronic systems.

The EMI filter is integrated with the transformer–rectifier unit, which has two primary functions:

• Voltage stabilization—ensuring that transient fluctuations are reduced during high-load operations.
• Suppression of electromagnetic interference—preventing disturbances that could affect avionics and communication systems.

Additionally, in the schematic diagram of the MPSZE system (Figure 7), the battery banks are split into two sections (“A” and “B”), ensuring an active coupling mechanism that enhances power stability during transient states.

The key components labeled in Figure 7 include the following:

• B—Shunt ammeter
• A—Analog ammeter
• S1—Contactor activating voltage on the 28 VDC output cable, terminated with a SzRAP-500 plug

The combination of active coupling, EMI filtering, and transformer–rectifier stabilization significantly improves system reliability by:

• Reducing voltage instability during transient loads by up to 30% compared to earlier versions.
• Minimizing EMI-related disturbances in avionics and communication systems.
• Enhancing battery longevity by optimizing energy distribution.

These improvements ensure higher operational efficiency and compatibility with hybrid-electric aircraft systems. Future testing will focus on optimizing the power regulation algorithms to further improve system performance in variable load conditions.

4. Results

4.1. Power Stability and Frequency Analysis

The test scenario focused on evaluating the performance of the MPSZE Mobile Field Power Station during the cold start of the helicopter. The system, configured with 12 lead–acid batteries (Q = 600 Ah), operated without support from photovoltaic panels (S) or external grid power (U) to assess its standalone capabilities.

Two test conditions were analyzed:

• Standard mode (MPSZE without feedback stabilization): The system powered the on-board electrical loads, and the engine start sequence, exposing transient voltage drops and fluctuations.
• Enhanced mode (MPSZE with feedback stabilization): The transformer–rectifier unit was engaged to provide additional voltage support and stabilize the DC power output during startup.

The results compare the system’s stability, transient response, and power continuity between the two modes, highlighting the effectiveness of the feedback stabilization in mitigating voltage drops and ensuring reliable power delivery during critical startup phases.

The stability of the aircraft’s electrical system cannot be assessed solely based on the numerical data in

Table 1. Comparative study of frequency stability in 230 V, 50 Hz AC circuit (photovoltaic inverter output circuit) during helicopter startups.

Lp.	Parameter	Unit	Value
1	2	3	4
1	fsr	Hz	49.997 ± 0.012
2	Fmax	Hz	50.154 ±0.001
3		%	100.31 ± 0.02
4	Fmin	Hz	49.41 ± 0.47
5		%	98.83 ± 0.01
6	fpp	Hz	0.41 ± 0.16
7	fp	Hz	0.0083 ± 0.0012
8		%	0.021 ± 0.001
9	ΔF	Hz	0.25 ± 0.12
10		%	0.511 ± 0.002
11	drift	Hz/min	0.0075 ± 0.0131

. Frequency fluctuations must be evaluated in terms of their impact on power delivery, transient response, and potential resonance effects on on-board avionics and control systems.

To provide a more detailed analysis, the following additional calculations were conducted:

• Frequency drift rate (${\displaystyle \frac{dF}{dt}}$): Determines the rate at which the frequency deviates over time, affecting stability.
• RMS (Root Mean Square) frequency deviation: Quantifies the overall variation in frequency, which can impact sensitive avionics.
• Transient recovery time ($T_{rec}$): Measures how quickly the system stabilizes after a disturbance.

One of the key parameters analyzed was the range of frequency variation, which was calculated as the difference between the maximum and minimum recorded values:

$$\mathsf{\Delta }F=F_{max}-F_{min}$$

where $F_{max}, F_{min}$ represent the upper and lower bounds of frequency deviations during transient conditions.

Another crucial aspect of system stability was the rate of frequency drift rate, which was determined based on the time required for the system to return to nominal conditions:

$${\displaystyle \frac{dF}{dt}}={\displaystyle \frac{\mathsf{\Delta }F}{T_{rec}}}$$

where $T_{rec}$ is the time required for the system to return to nominal frequency after a disturbance.

To validate the data presented in Table 1, the following experimental setup was used:

• High-resolution frequency analyzers were connected to the inverter output circuit.
• Data were collected at 100 ms intervals to detect short-term variations.
• Frequency drift measurements were conducted over a 10 min interval, capturing both transient and steady-state conditions.
• The system was tested under different electrical loads (baseline avionics vs. full engine startup).

The analysis confirmed that the transformer–rectifier stabilization mechanism significantly reduced short-term frequency variations, improving system resilience under high-load transitions.

The results compare the system’s stability (Table 1), transient response, and power continuity between the two modes, highlighting the effectiveness of feedback stabilization in the following:

• Mitigating voltage drops—transient fluctuations reduced by up to 30% in enhanced mode.
• Ensuring reliable power delivery—frequency deviations were stabilized to within ±0.02 Hz, minimizing potential interference with on-board systems.
• Reducing frequency drift effects—long-term drift was kept below 0.008 Hz/min, ensuring continuous operational stability.

These findings provide a strong basis for further refinement of feedback-controlled power systems in aviation applications. Future work will focus on enhancing predictive control algorithms to further optimize stability and response time in dynamic load environments.

4.2. Experimental Evaluation of the MPSZE System

Table 1 presents key frequency-related parameters that describe the system’s stability and transient behavior. To accurately assess the stability of the system, both short-term and long-term variations in frequency were analyzed, with a particular focus on their impact on power regulation and transient response.

The nominal system frequency (f_sr) is measured at 49.997 Hz with a small deviation of ±0.012 Hz, indicating that the system operates very close to the standard 50 Hz, ensuring stable frequency regulation. The maximum recorded frequency (F_max) reaches 50.154 Hz, while the minimum frequency (F_min) drops to 49.41 Hz with a deviation of ±0.47 Hz. These values indicate slight variations within the operational range. The corresponding percentage values show that the frequency exceeded the nominal value by 0.31% at its peak and decreased to 98.83% at its lowest. Despite these variations, the system remains within acceptable operational limits, ensuring that no significant power instability occurs.

The peak-to-peak frequency fluctuation ($f_p$) is recorded at 0.41 Hz with a ±0.16 Hz uncertainty, representing the total range of frequency variations. Instantaneous frequency variation per cycle is measured at 0.0083 Hz with a ±0.0012 Hz deviation, confirming that short-term fluctuations are minimal.

$$f_p={\displaystyle \frac{\mathsf{\Delta }F}{Number of cycles}}$$

The frequency drift rate (drift) was recorded at 0.0075 Hz per minute, with a deviation of ±0.0131 Hz per minute, which represents the long-term frequency variation and is crucial for assessing system aging and operational reliability.

To validate the data presented in Table 1, a detailed experimental procedure was implemented to measure frequency stability and drift over time.

• High-resolution frequency analyzers were used to record real-time frequency variations at 100 ms intervals.
• Continuous frequency data were collected over multiple operational cycles, including startup and transient conditions.
• The frequency drift rate was observed over a 10 min period to assess long-term behavior.
• Load variations between 5% and 85% were applied to observe the impact on frequency stability.

Figure 8 illustrates the frequency stability and drift over time in the analyzed system. The current frequency (blue, dashed line) fluctuates around the nominal 49.997 Hz (black, dashed line), indicating minor variations in system performance.

The maximum frequency (red line) and minimum frequency (green line) represent the recorded upper and lower bounds of frequency deviations. A key observation is the frequency drift (purple, dotted line), which shows a slight increasing trend over time, demonstrating a gradual long-term shift in system frequency.

The observed drift does not exceed ±0.02 Hz per minute, confirming that the feedback stabilization and power management mechanisms effectively mitigate fluctuations and ensure stable power delivery.

Although frequency variations exist, their magnitude is insufficient to cause significant power instability. However, in aviation applications, even small fluctuations can affect sensitive avionics and power-sensitive components.

To assess this risk, the system’s dynamic response was tested under variable load conditions, confirming that:

• The short-term frequency variation does not exceed 0.021%, minimizing its impact on avionics.
• Long-term drift remains below 0.008 Hz/min, ensuring power stability over extended operational periods.
• Feedback-controlled rectification effectively regulates frequency variations, reducing transient voltage drops by up to 30%.

The combination of feedback stabilization and power management strategies effectively controls voltage and frequency instability, ensuring continuous and reliable power delivery, particularly during critical startup phases.

However, it is important to note that while deviations remain within acceptable ranges under tested conditions, further studies are required to evaluate stability under extreme environmental conditions and high-load variations.

4.3. Impact of Feedback Stabilization on Power Distribution

The results of frequency stability analysis demonstrate that the system maintains a high level of regulation with minimal deviations. The combination of feedback stabilization and power management strategies effectively mitigates frequency fluctuations, ensuring continuous and reliable power delivery, particularly during transient conditions. The graphical visualization illustrates these variations, where the nominal frequency remains stable, while maximum and minimum frequency values indicate minor but controlled deviations. The drift rate is low, confirming the long-term stability of the system.

Transient Response of MPSZE During Helicopter Startup

A critical aspect of evaluating the system’s performance under transient conditions involves analyzing the behavior of the MPSZE during operational scenarios. To further investigate its power stability, a series of measurements were conducted on a battery configuration consisting of two modules, each containing 12 lead–acid batteries (Q = 600 Ah). These tests were performed without support from photovoltaic panels (S) or an external power grid (U) to simulate real-world off-grid conditions. The system was set to disconnect at 25.0 VDC, a threshold defined to prevent deep battery discharge.

Measurements of the MPSZE system, battery configuration with two modules (12 lead-acid batteries, Q = 600 Ah), operating without support from photovoltaic panels (S) or an external power grid (U) during transient states. The system was set to disconnect at 25.0 VDC during the activation and deactivation of on-board receivers on the helicopter. Cold engines start tests for Engine 1:

(a)

response without feedback stabilization—MPSZE

(b)

response with feedback stabilization—MPSZE

In these tests, two configurations were compared to assess the impact of feedback stabilization on power stability. The first scenario (Figure 9a) presents the response without feedback stabilization, where significant voltage drops were observed during the startup of on-board electrical loads. The second scenario (Figure 9b) includes active feedback stabilization, which effectively compensates for transient voltage dips and ensures a more stable power supply to critical systems.

These findings are crucial in validating the role of feedback control in maintaining power stability, particularly in aviation applications where electrical reliability is essential. The combination of frequency stability analysis and transient response evaluation confirms that the MPSZE system can deliver reliable energy, even under fluctuating load conditions.

By integrating real-time frequency monitoring, power stabilization strategies, and advanced battery management, the system can be further optimized for applications requiring high-efficiency, off-grid energy solutions, such as emergency power distribution. The graphical representation of frequency variations and transient response comparisons further support the importance of dynamic power stabilization mechanisms in such environments.

The conducted tests of the MPSZE Mobile Field Power Station during the cold start of the helicopter provided key insights into the impact of the implemented active feedback stabilization on power system performance:

• Voltage Stability and Risk of Overcharging: The active feedback loop effectively reduced the duration of voltage drops below 24 V, ensuring more stable power delivery during startup. However, once the current demand subsided, the system intensively recharged Section B (8 lead–acid batteries), increasing the risk of overcharging and excessive depletion of Section A (4 lead–acid batteries supporting the photovoltaic inverter). To prevent this, it is recommended to disable the feedback loop when current demand falls below 3290 A.
• Suppression of Oscillations: The multiple oscillations observed during sudden load reductions were significantly dampened. The number of oscillations decreased to one, and their amplitude was reduced, improving system response stability.
• Improved Frequency Stability: The active feedback mechanism reduced frequency drift in conditions of dynamic DC load variations, contributing to a more stable power supply for on-board systems.

These findings suggest that while the active feedback mechanism enhances voltage stability and mitigates oscillations, further optimization is required to prevent potential battery overcharging and ensure long-term system reliability.

5. Discussion

5.1. Key Findings and Interpretation in the Context of Prior Research

The results of this study confirm that the MPSZE system provides effective energy management and stability, particularly in off-grid and high-demand transient conditions, such as helicopter engine startups. The feedback stabilization mechanism significantly improved voltage stability, reduced frequency drift, and minimized oscillations, demonstrating enhanced power reliability compared to traditional passive energy storage systems.

These findings align with prior research on advanced power stabilization in aviation energy systems, where active feedback loops and integrated rectifier–transformer units have been shown to mitigate transient power fluctuations. Studies on more-electric aircraft (MEA) power systems have highlighted similar challenges in maintaining stable DC voltage and frequency during high-load transitions. The frequency stability analysis in this study further supports the literature on power electronics and adaptive energy management strategies, reinforcing the role of smart power distribution networks in modern aviation.

5.2. Implications of Advanced Power Systems for Future Aircraft Design

The transition toward more-electric and hybrid-electric aircraft demands high-efficiency, lightweight, and intelligent energy management solutions. The MPSZE system, with its modular design, active feedback control, and integration with renewable energy sources, presents a scalable solution for reducing reliance on traditional auxiliary power units (APUs) and improving overall aircraft energy efficiency.

Advanced power systems will play a key role in the following:

• Reducing fuel consumption by minimizing dependence on combustion-driven APUs.
• Enhancing system redundancy and reliability, ensuring uninterrupted power supply to critical aircraft systems.
• Integrating energy storage with high-voltage electrical architectures in future hybrid-electric propulsion systems.
• Supporting distributed power generation, where on-board energy storage complements fuel-cell or solar-based energy systems for extended operational endurance.

These improvements align with emerging aviation electrification strategies, particularly in urban air mobility (UAM), unmanned aerial vehicles (UAVs), and hybrid-electric commercial aircraft.

5.3. Challenges in Integrating Renewable Energy into Aviation

While renewable energy integration holds promise for enhanced aircraft energy autonomy, significant challenges remain in adapting these technologies for practical aviation use. The MPSZE system, which incorporates photovoltaic energy storage, provides a test platform for evaluating off-grid energy solutions in aviation. However, this study highlights several technical and operational barriers:

• Energy density limitations: Current battery and solar technologies have low power-to-weight ratios, making them impractical for high-energy-demand aircraft systems.
• Intermittency of renewable sources: Solar energy generation fluctuates based on weather conditions and operational altitude, requiring hybridized storage solutions for consistent power output.
• Power management complexity: The need for adaptive switching, real-time load balancing, and voltage stabilization increases system complexity and integration challenges.
• Thermal management issues: High-power energy storage solutions, including lithium-ion batteries and fuel cells, require advanced cooling solutions to prevent overheating and efficiency losses.

Addressing these challenges requires further research into next-generation battery technologies, solid-state energy storage, and power electronics optimization to enable efficient renewable energy integration in aviation applications.

5.4. Potential Applications of Mobile Energy Storage Systems

The MPSZE system demonstrates the viability of mobile energy storage and distribution for a range of aerospace, defense, and emergency power applications. Based on the findings of this study, potential use cases include the following:

(a)

Aircraft Ground Operations and Maintenance

• Providing auxiliary power during aircraft servicing to reduce fuel dependency and support sustainable airport operations.
• Acting as an emergency backup system in cases of unexpected APU failure or ground power unit (GPU) unavailability.

(b)

Unmanned Aerial Vehicles (UAVs) and Remote Sensing Platforms

• Powering UAVs and electric propulsion systems in extended operations.
• Supporting modular battery swapping systems to improve UAV endurance and operational efficiency.

(c)

Emergency Power Supply

• Supplying field-deployed radar, surveillance, and communication systems with reliable off-grid power.
• Enhancing mobile command centers and field hospitals with renewable-powered energy storage solutions.

These applications highlight the adaptability of modular energy storage in both aerospace and non-aviation domains, paving the way for future advancements in mobile power technologies.

5.5. Limitations of the Study and Future Research Directions

Although this study provides valuable insights into mobile energy storage for aviation applications, several limitations must be acknowledged:

• Experimental conditions were limited to ground-based testing under controlled scenarios. Further in-flight evaluations are required to assess system performance in real-world operating conditions.
• The study focused on lead–acid battery configurations, which, while reliable, are less efficient compared to lithium-ion or solid-state battery technologies. Future research should explore alternative energy storage solutions for improved energy density and weight reduction.
• The feedback stabilization mechanism effectively mitigated transient instability; however, it introduced potential risks of overcharging under low-current conditions. Further refinement of adaptive energy regulation algorithms is necessary to prevent long-term battery degradation.
• The role of hybrid energy integration (solar, battery, and fuel cell combinations) was not fully explored in this study. Future work should investigate multi-source energy architectures, optimizing power allocation between different energy storage and generation methods.

Expanding the scope of research to include advanced simulations, real-world flight testing, and integration with next-generation aircraft power systems will provide a more comprehensive understanding of the role of mobile energy storage in modern aviation.

6. Conclusions

This study evaluated the MPSZE mobile energy storage system for aviation applications, focusing on frequency stability, transient response, and power continuity during critical startup phases. The results demonstrate that active feedback stabilization significantly improves voltage regulation, reduces frequency drift, and minimizes power fluctuations, ensuring reliable energy delivery in off-grid aviation environments.

The findings highlight the potential of advanced power systems in supporting more-electric and hybrid-electric aircraft, improving energy efficiency and reducing reliance on traditional auxiliary power units (APUs). However, challenges remain in integrating renewable energy sources, optimizing power-to-weight ratios, and refining feedback control mechanisms to prevent overcharging.

Future research should explore lightweight battery technologies, hybrid energy storage solutions, and real-world flight tests to enhance the feasibility of mobile power systems in aviation. The MPSZE system provides a strong foundation for developing modular, scalable energy solutions for aerospace, and emergency applications, supporting the transition toward more sustainable and autonomous power architectures.