Navigating the Intersection of Microgrids and Hydrogen: Evolutionary Trends, Challenges, and Future Strategies

Abstract

Growing interest in sustainable energy has gathered significant attention for alternative technologies, with hydrogen-based solutions emerging as a crucial component in the transition to cleaner and more resilient energy systems. Following that, hydrogen-based microgrids, integrated with renewable energy sources including wind and solar, have gained substantial attention as an upcoming pathway toward long-term energy sustainability. Hydrogen, produced through processes such as electrolysis and steam methane reforming, can be stored in various forms including compressed gas, liquid, or solid-state hydrides, and later utilized for electricity generation through fuel cells and gas turbines. This dynamic energy system offers highly flexible, scalable, and resilient solutions for various applications. Specifically, hydrogen-based microgrids are particularly suitable for offshore and islanded applications, with geographical factors, adverse environmental conditions, and limited access to conventional energy solutions. This is critical for energy independence, long-term storage capacity, and grid stability. This review explores topological and functional-based classifications of microgrids, advancements in hydrogen generation, storage, and utilization technologies, and their integration with microgrid systems. It also critically evaluates the key challenges of each technology, including cost, efficiency, and scalability, which impact the feasibility of hydrogen microgrids.

1. Introduction

Traditionally, power systems were designed to supply energy to areas with high consumption, which led to the construction of large power plants near industrial and residential areas [1]. However, due to challenges with fuel supply, construction constraints, and environmental concerns, most power generation shifted away from these densely populated zones. With this shift, it became necessary to transmit power over long distances to reach high-demand areas. To minimize transmission losses, the generated voltage is stepped up to high levels, then later stepped down to medium and low voltages at grid substations, where it is distributed to industries and residential areas [2]. However, this power system topology has introduced several technical, social, and environmental issues, including inefficient energy transfer, reduced energy security, and increased pollutant gas emissions [3]. This led to the development of novel power system topologies in the next phase of power system evolution.

Small-scale power generators, often powered by Renewable Energy Sources (RESs), have been introduced to the main grid. These generators, known as Distributed Generators (DGs), connect directly to the distribution network, providing industries and residents with direct access to their output [4]. DGs offer both advantages and disadvantages compared to traditional power sources. Some of the benefits include reliable electricity supply, increased system efficiency, easier integration of RESs, and reduced stress on the power system [5]. However, there are also drawbacks, such as power quality issues, frequent variations in bus voltages, changes in fault levels, reduced system inertia, and decreased network stability. Managing multiple distributed generators, especially with a high share of RESs, is complex due to the intermittent nature of renewable sources and the relatively unexplored characteristics of modern Energy Storage Systems (ESSs) [6]. Nevertheless, a localized system that includes all the essential components of a power system can address these challenges effectively due to its small scale. This type of system is known as a microgrid [7]. In recent years, hydrogen systems have emerged as an energy storage solution for high-RES-integrated systems, where excess energy is used to produce hydrogen, which can then be stored for use during periods of high demand [8]. Furthermore, this integration aligns with the 16 Sustainable Development Goals (SDGs) outlined by the United Nations. Specifically, SDG 7 showcases the importance of ensuring access to affordable, reliable, sustainable, and modern energy for all [9]. Modern hydrogen-integrated microgrids, as sustainable and reliable alternatives to traditional power systems, can make significant contributions toward achieving this goal. The concept of a hydrogen economy has been a topic of discussion for several years and continues to be relevant in modern contexts [10,11]. From generation to utilization, any hydrogen-based system involves several primary processes: packaging, transportation, storage, and transfer. These processes are essential within the framework of the hydrogen economy. Hydrogen must be stored either through compression or liquefaction and transported via surface vehicles or pipelines to facilitate effective storage and transfer.

To ensure a comprehensive review, this study utilized scientific databases including IEEE, MDPI, and Scopus. The search focused on publications related to microgrids that incorporated at least one type of hydrogen technology, such as generation, storage, or utilization. To maintain relevance to up-to-date developments, most of the selected papers were published in the last decade. Most of the current literature on microgrids [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32] primarily focuses on planning, control, energy management, and demand-side management strategies. Even when hydrogen technologies are integrated into microgrids, there is limited explanation regarding the selection of specific hydrogen techniques. Additionally, most of the existing research on hydrogen applications in microgrids [33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66] examines the operations, advancements, and drawbacks of these techniques. However, the literature related to hydrogen generation, storage, and consumption mainly analyzes the essential principles without discussing their potential integration into the microgrids. As a result, the potential applications of these techniques are rarely addressed. Despite the available studies on microgrids and hydrogen storage, there remain gaps in identifying suitable hydrogen techniques for specific microgrid applications. To address this gap, this paper offers the following contributions.

• An updated review of microgrid definitions, microgrid classifications, hydrogen production techniques, hydrogen storage techniques, and hydrogen utilization techniques.
• Different microgrid applications are matched with potential hydrogen production, storage, and utilization techniques.

The remaining sections of this paper are organized as follows. Section 2 discusses the microgrid definitions, characteristics, and issues. Section 3 illustrates the requirement of ESSs due to RESs, modern loads, and modern power system development. In Section 4, the role of hydrogen in microgrids as an energy carrier is discussed. In Section 5, potential hydrogen applications on future microgrids are discussed, followed by the conclusion in Section 6.

2. Microgrids: Definitions, Characteristics and Issues

Microgrids typically consist of energy sources, loads, energy storage systems, distribution networks, protection equipment, and control schemes that ensure power, voltage, and frequency regulation within the system. Some microgrids can connect to the main grid at the point of common coupling through a static transfer switch. From the perspective of the main grid, a microgrid can be considered a single unit, allowing it to supply power to the main grid during periods of excess generation and draw power from the main grid during power shortages. Additionally, a microgrid can consciously separate from the main power grid during circumstances of power quality on the main grid [12]. In recent years, the capability for standalone operation of microgrids has gained significant attention. If a microgrid includes sufficient energy sources and storage devices, it can be designed to operate independently of the main grid. This type of microgrid arrangement is usually referred to as an islanded, standalone, or self-sufficient microgrid [13].

2.1. Microgrid Definitions

Over the years, microgrids have been utilized in various industrial and academic applications for electrification and research purposes. The term “microgrid” is composed of two parts: “micro”, referring to the small-scale nature relative to the main power system, and “grid”, referring to the main power system. A microgrid is defined considering two supply aspects, power and heat, to complete a system of an accumulation of small energy sources and load by the Consortium for Electric Reliability Technology Solutions (CERTS) [14]. In [15], a microgrid is defined as a low voltage, small-scale system, where small generation units, ESSs, and general and critical loads combine to develop a small-scale energy system. In the European approach, a microgrid concept is as a low voltage distribution electricity network containing various DGs, ESSs, and general and critical loads, that can operate as islanded or grid-connected in regard to the main power system [16]. Also, in [16], a microgrid is defined as a subdivision of the main power grid, involving generation and loads, where islanded and grid-connected operation is carried out without compromising the stability of the main power grid even during unstable grid conditions. All these definitions imply that a microgrid should include the essential components of a main grid, except for some non-essential sections. A microgrid system must maintain power balance, voltage regulation, protection, and other critical parameters within the defined region. Figure 1 illustrates a typical hydrogen-integrated, grid-connected microgrid structure.

2.2. Microgrid Characteristics and Issues

A microgrid is responsible for overseeing electrical components, energy management, voltage regulation, frequency regulation, and safety. Generally, a microgrid connects to the distribution network at medium or low voltage levels through the point of common coupling. The point of common coupling manages the connection and disconnection from the utility grid. Before the boundary of the point of common coupling, the microgrid includes generators, ESSs, loads, Energy Management Strategies (EMSs), safety protocols, and power electronic converters. This microgrid setup ensures that ESSs can support critical loads within the microgrid, especially during disruptions in the main power grid. It also generates the necessary reference voltage and frequency during islanded operation. Typically, microgrids are designed as pre-planned systems in specific locations, such as remote areas or offshore platforms, and utilize local data to control power flow. However, there are key challenges within microgrids that need to be addressed in future studies. Some of the commonly cited issues in the literature include energy storage sizing problems, system stability concerns, protection challenges, optimal location selection, forecasting data inaccuracies, energy management complications, demand response issues, microgrid security vulnerabilities, industrial standards gaps, and regulatory policy obstacles.

2.3. Microgrid Classification Based on Topology

Microgrids are generally categorized based on the operating power of the distribution network as in Figure 2. Microgrids operating using AC distribution networks are identified as AC microgrids, while those operating in DC distribution networks are identified as DC microgrids. Hybrid microgrids consist of both AC and DC electricity distribution networks.

2.3.1. AC Microgrids

In AC microgrids, the power distribution network operates in the form of AC power. AC-powered devices can connect directly to the distribution network, while DC-powered devices need to be connected through power converters [19]. AC microgrids can easily connect to existing grids since they already operate in AC power. AC microgrids have evolved significantly regarding structures, control strategies, EMSs, and protection schemes [20].

• Interoperability: Can easily interconnect with existing power systems without requiring separate converter controllers.
• Standardization and Compatibility: Well-established worldwide, with standardized norms for power, voltage, and frequency variations. These standards are applicable to AC microgrids, facilitating easy integration into industry.
• Resiliency: Capability to transition from grid-connected to standalone mode. Capability to power the local loads even at main grid outages, providing stable operations.

2.3.2. DC Microgrids

A DC microgrid is a small-scale power system that operates in DC power. DC-powered devices can connect directly to the distribution network, while AC-powered devices need to be connected through power converters [21]. With advancements in power electronics devices and improvements in DC-operable sources, loads, and ESSs, DC microgrids have a high potential for future industrial applications [22].

• Easy integration of RESs, ESSs, and loads: Technologies such as PV operate on DC power, and several studies aim to improve their efficiency and power levels. ESS-like batteries also operate on DC power. Most consumer electronic devices, such as PC systems, mobile devices, laptops, printers, and lighting, are powered using DC.
• Elimination of AC-related issues, synchronization, frequency control, reactive power, and harmonics: Issues such as frequency control and harmonic distortion arise with the introduction of frequency in an AC system.
• Reduced conversion stage/improved efficiency: Since most residential and industrial loads operate on DC power, selecting an appropriate DC voltage level minimizes the need for power conversions. Minimal conversion increases system efficiency.
• Reduced cost of the system: DC systems can operate with thinner conductors with reduced cost. Reduced conversion stages increase efficiency with a reduced cost.

2.3.3. Hybrid Microgrids

Both AC- and DC-based electricity distribution networks are used in hybrid microgrid distribution networks. This involvement reduced the required power conversion stages, increasing the overall efficiency of the microgrid system. Furthermore, the required amount of power for electronic converters is also reduced which reduces the cost as well [23]. This allows both consumers and suppliers to choose an appropriate type of power for connection or supply [24].

• Seamless integration: Can incorporate both AC and DC components, leveraging each type’s unique benefits.
• Increased efficiency: Reduce the need for heavy conversion infrastructure by only converting when necessary
• Optimal renewable and ESS usage: Enable optimized integration of renewable energy and storage by leveraging each energy form’s strengths.

2.4. Classification of Microgrids Based on Functional Layers

Microgrids are typically divided into three main operational layers: the physical layer, the communication layer, and the intelligence layer, as outlined in this section.

2.4.1. Physical Layer

The physical layer encompasses all the physical components of the system, including power sources, energy storage devices, loads, power electronic devices, and the distribution network. Power sources can operate in either the DC or AC domain and must be carefully chosen based on the specific requirements of the system. Power electronic components are crucial for enabling the plug-and-play capability of the microgrid, allowing each component to be seamlessly connected or disconnected from any layer of the microgrid. This feature is especially important during transitions from grid-connected mode to islanded mode, ensuring smooth operations without disruptions and helping to maintain the stability of the microgrid. Power electronic converters, such as back-to-back voltage source converters and electronic control units, are commonly used for these purposes.

2.4.2. Communication Layer

The communication layer is responsible for providing the status of the components in the physical layer to the decision-making layers. This allows the proper functioning of physical layer components. For short-distance communications, wired networks such as RS 232 and RS 485 are efficient and reliable [25]. However, wired communication is complex and not reliable at present. Distributed Network Protocol (DNP3) is used for supervisory and data acquisition purposes in microgrid EMSs due to its security features and robustness, even under noisy conditions [26]. Modbus is another commonly used protocol in application layers because of its simplicity and ease of implementation. Modbus facilitates communication between supervisory systems and microgrid field devices [26]. Specifically, IEC 61850 is the international standard for communication in substations and smart grids, which has also been extended to some microgrid applications [27]. This standard enables real-time communication between electronic operating devices. The Open Platform Communications Unified Architecture (OPC-UA) protocol allows the integration of various systems, such as SCADA systems, intelligent electronic devices, and data analytics systems [28]. Furthermore, communication protocols based on ISO or open system interconnection, transmission control protocols, and UDP/IP protocols ensure the secure and fast transmission of the data [18]. Furthermore, microgrid communication structure is commonly categorized considering the range of the communication such as Wide Area Network (WAN), Field Area Network (FAN), Neighborhood Area Network (NAN), Building Area Network (BAN), and Home Area Network (HAN) [17] as illustrated in

Table 1. Analysis of microgrid communication layer [17,18,25,29,30].

Type	Connection Scope	Microgrid Operations
WAN	Multiple microgrids or microgrid with a central power grid	Data exchange for regional monitoring, control, and coordination. Real-time data transfer across microgrids for operations including balancing supply and demand, managing power fluctuations
FAN	Covers specific field equipment like substations	Integrates field devices for centralized monitoring and control within a microgrid. Rapidly collects and transfers data on grid conditions such as faults. Ensures resilience by quickly detecting and addressing issues at critical points
NAN	Links buildings or distributed resources in defined area	Supports local load balancing and demand response within community microgrids; gather energy data from multiple residences, optimize energy use, and implement demand responses
BAN	Operates within individual area in a microgrid	Transfers data among energy management systems, adjusting usage based on occupancy, time, and temperature. Reduces peak load contributions to the microgrid using building-level energy management
HAN	Serves individual homes in a microgrid setup	Connects individual components, enabling energy adjustments according to pricing signals and energy availability. Facilitates integration of PV and EV, allowing residents to control energy use and peak load reduction

.

2.4.3. Intelligence Layer

The intelligence layer is the core of all operations and control within a microgrid. It typically collects data from the physical layer through the communication layer, processes these data, and then sends the necessary commands back to the physical layer devices via the communication layer [17]. The main objectives of this layer are planning, energy management, demand-side management, and protection coordination of the system.

Planning is a key function performed by the intelligence layer. With the increased integration of renewable energy sources, frequent fluctuations are introduced into the microgrid. Additionally, modern load profiles have become more variable due to the introduction of new technologies, regardless of the time of day. Even some literature has developed programming models for optimizing the optimal component sizing and scheduling of the DER under different pricing scenarios [31]. Some studies even consider the capacities, location, time frame of the operation, and investment time in the planning process [32]. Even dedicated software models also have been developed which input weather data, required RES techniques, and tariff data and output the optimal capacity planning to reduce the cost of operations [33].

Energy management from a power system perspective involves the systematic monitoring, control, and optimization of electrical generation and transmission facilities to ensure their effective operation while meeting the objectives defined by regulatory bodies. In microgrids, this approach is similarly applied, involving tasks such as load forecasting, supervisory control, and data acquisition, all of which support efficient decision-making for generation, storage, and load distribution. The core aim of an EMS within a microgrid context is to maintain power balance. Additionally, EMSs are often implemented to address various optimization goals, such as extending equipment lifespan, reducing operational expenses, enhancing system reliability, improving overall efficiency, and minimizing environmental impacts, among other key applications [34].

Load or demand management is a specific method to control electricity by balancing demand, reducing peak loads, and improving efficiency. Techniques include peak shaving, load shifting, demand response, and energy storage as in Figure 3 [36]. Benefits include cost savings, system reliability, and reduced environmental impacts. In microgrids, it optimizes limited resources, integrates renewables, and maintains stability in isolated systems.

Microgrids typically consist of various power sources, loads, and energy storage systems. A control system is needed to manage tasks such as connecting, disconnecting, regulating, and monitoring to ensure smooth operation. The control system is responsible for all these functions to maintain the stability of the microgrid. To achieve these objectives, traditional control architectures can be classified into four types: centralized control, decentralized control, distributed control, and hierarchical control. Protection and fault management in microgrids play a pivotal role in ensuring safe, reliable, and efficient operation. Microgrids are vulnerable to various types of faults, such as overcurrent, short circuits, and ground faults. Control strategies detect and localize faults in minimal time by continuously monitoring the electrical parameters of the system. Faults are typically isolated by quickly disconnecting the affected section or component from the rest of the system, which prevents cascading failures. Faults in microgrids can cause damage to components and equipment, leading to downtime and costly repairs. Commonly used protection methods include voltage protection, adaptive protection, overcurrent protection, differential protection, and distance protection.

In the discussion of microgrids, power-based classification, layer-based classification, and control-based classification are illustrated in the sections above. The classification of microgrids based on control techniques is not discussed in this study, as it is commonly available in most of the literature and beyond the objectives of this study. Classification based on connection type has already been discussed in the introductory section regarding grid-connected and islanded scenarios. Classification based on scenarios is illustrated in the final section of the study.

3. Role of Hydrogen in Microgrids as an Energy Storage Solution

ESSs are critical in modern power systems due to the rise of RESs, evolving load profiles, and the complexity of contemporary grids [37]. The integration of RESs, which are inherently intermittent, makes ESSs essential for smoothing out fluctuations in energy generation. ESSs are needed to shift energy over time, storing excess power during periods of high generation and releasing it during times of low or no generation [38]. As modern loads evolve with increasing electrification and demand for high power quality, ESSs must respond quickly to balance supply and demand. Modern loads, such as electric vehicles, require more flexible and fast-acting power systems, leading to a need for ESSs to provide rapid response services like frequency regulation, voltage control, and black start capabilities [39]. Additionally, as power systems become more decentralized with DER, ESSs help manage the complexity by enhancing grid flexibility. Beyond these factors, ESSs play a pivotal role in grid decarbonization goals, supporting the transition to cleaner energy by storing renewable energy. ESSs also optimize energy markets, enabling price arbitrage by storing low-cost electricity during off-peak hours and selling it during high-demand periods, which improves market efficiency and stabilizes energy costs. Proper utilization of ESSs can mitigate these issues, offering several benefits as given below.

Supply-demand matching: In the traditional power system, a portion of the generation is reserved to meet peak demands during the day, often leading to energy waste. With the integration of ESSs, energy is stored during the excess energy generation periods and applied during times of energy deficit. This allows energy generators to operate at a constant level without frequent power fluctuations, enabling economic and highly efficient operations [40].

Enabling high renewable energy penetration: Solar PV and wind are the largest renewable energy sources, estimated to contribute 20–30% of electric energy in the next decade. A large portion of electricity generation of these occurs during off-peak periods, which have limited economic value. ESSs can store energy produced during off-peak times and dispatch it during more economically valuable periods.

Reliability enhancement: ESSs can respond to intermittent fluctuations, making the power system reliable for both producers and consumers. ESSs can provide power to the main power system eliminating transient variations caused by brief disturbances and sudden load shifts. Appropriate ESS designs can even supply power back to the main power system for long-term energy requirements including prolonged blackouts [41].

Power quality improvement: Distribution networks, susceptible load units, and decisive operations suffer from interruptions, leading to economical disadvantages for both supplies and consumers. Properly implemented energy storage systems can provide electricity to customers without secondary fluctuations or disruptions, overcoming power quality problems such as sags, spikes, and harmonics.

To meet the requirements of an ESS, hydrogen-based ESSs must incorporate at least three critical stages, hydrogen generation, hydrogen storage, and hydrogen utilization. Initially, any excess energy should be converted into hydrogen, allowing it to be stored as a stable, energy resource. When there is a demand for electricity, this stored hydrogen can then be reconverted into electrical energy, ensuring that energy is available when needed. This process highlights the conversion mechanism essential to hydrogen ESSs, enabling both efficient storage and reliable energy recovery.

3.1. Hydrogen Storage Techniques

One of the key challenges in integrating the full potential of hydrogen as an energy storage solution is identifying suitable storage types. There are two principal methods of hydrogen storage systems described in

Table 2. Analysis of hydrogen storage techniques [42,43].

Storage Method	Description	Benefits	Drawbacks
Compressed Hydrogen Gas Storage	Hydrogen stored in high-pressure tanks (up to 700 bar). Compression consumes about 13–18% of hydrogen’s Lower Heating Value (LHV)	High filling/release rates. No additional energy needed.	Technology for such high-pressure compression is not well-developed
Liquid Hydrogen Storage	Requires very low temperatures (−252.8 °C). High-density results in volumetric energy density of around 8 MJ/L	High energy density. Reduced tank requirements. Reduced costs.	High liquefaction cost (consumes 30–40% of LHV), Daily evaporative losses (boil-off rate of 1.5–3%)
Metal Hydride Storage	Hydrogen reacts chemically with metals or metal alloys, expanding volume by 20–30%. External energy is required to release stored hydrogen	Higher storage capacity compared to compressed and liquid.	High release temperatures needed. Undesired gas formation. Onboard energy requirements for release.
Complex Hydride Storage	Hydrogen bonds with metal atoms to form stable complex anions, allowing dense atomic-level storage. Holds up to 10–15% hydrogen by weight.	Denser storage. Possible hydrogenation/dehydrogenation.	Requires temperature control to release hydrogen
Physical Adsorption	Hydrogen adsorbs onto solid surfaces via van der Waals forces, using microporous carbon structures, metal–organic frameworks, or zeolites	High loading/unloading rates. Near-zero byproduct losses.	Low capacity at room temperature. Reasonable only at cryogenic temperatures or high pressures.
Chemical Hydrogen Storage	Hydrogen stored in liquid organic carriers, which release hydrogen through dehydrogenation. Hydrogenated part can be reused to load hydrogen.	Can use current infrastructure for bulk storage and transportation.	Chemical processing needed for release Potentially costly

: physical-based storage and material-based storage [42]. Physical storages include compressed gas, liquid–gas, and cryo-compressed gas. Material-based storage options include metal hydrides, complex hydrides, absorbents, and liquid organic compounds.

3.2. Hydrogen Generation Techniques

Generally, hydrogen is extracted from fossil fuels of biomass and water. Natural gas is the main source in practice now. Also, hydrogen produced utilizing RESs is recognized as renewable hydrogen which is commonly known as green hydrogen.

3.2.1. Electrolysis Techniques

Electrolysis is a process that uses electricity to split water into hydrogen and oxygen gases. This occurs in an electrolyzer, which applies an electric current to water, breaking the bonds in water. There are several types of electrolysis methods used to produce hydrogen. Alkaline electrolysis is the most common and uses an alkaline solution as an electrolyte. PEM electrolysis uses a solid polymer membrane as an electrolyte, offering higher efficiency and faster response times. Solid oxide electrolysis operates at high temperatures and uses a ceramic electrolyte to produce hydrogen with higher efficiency while the molten carbonate technique utilizes liquid carbonate solutions as an electrolyte. Detailed illustrations of each of these techniques including operating parameters, advantages, disadvantages, and applications are given in

Table 3. Analysis of electrolyzer techniques [44,45,46].

Type	Alkaline	PEM	Solid Oxide
Technical State	Commercial	Commercial	Experimental
Electrolyte	KOH solution	Nafion membrane	ZrO2 doped with Y2O3
Temperature (°C)	40–90	20–10	650–1000
Pressure (bar)	<30	<200	<20
Efficiency (%)	55–75	45–60	75–85
Gas purity (%)	>99.50	>99.99	>99.90
Application	Hydrogen production applications	Portable applications Power to gas applications	R&D studies
Advantages	Stable operation Long term operations Low-cost production	Fast response times High purity Dynamic operations	High efficiency Low energy consumption No noble metal catalyst
Challenges	Low-purity Low current densities Corrosive system	High cost Low durability High pressure	Not well established High temperature Low durability

.

3.2.2. Other Techniques

Apart from electrolysis, there are several other hydrogen generation techniques applied in the industry and research studies. Details of some of these techniques include Steam Methane Reforming (SMR), partial oxidation, Autothermal Reforming (ATR), Plasma Reforming (PR), biomass gasification, biohydrogen production, and photocatalytic water splitting. Detailed descriptions of the operations, reactions, and key factors are given below in

Table 4. Analysis of other hydrogen generation techniques [47,48,49].

Method	Description	Key Factors
Steam Methane Reforming	Produces hydrogen via natural gas, ethanol, and methanol as feedstocks. Synthesis gas mixture (hydrogen, CO2, CO) is generated using methanol and steam. The process operates at 200–300 °C and pressures around 20–30 atm. Endothermic: CH3OH → CO + 2H2 Exothermic: CO + H2O → CO2 + H2	High carbon footprint. High energy requirements. Complex process.
Partial Oxidation	Utilizes thermal or catalytic oxidation of natural gas or coal under high temperature (1200–5000 °C) and high pressure (3–10 MPa). Syngas produced via Fischer-Tropsch synthesis. TPOX produces more CO; CPOX, with lower temperature, achieves higher H2 ratio. TPOX: CnHm + nH2O → nCO + (n+½m)H2 CPOX: CnHm + ½ nO2 → nCO + ½ mH2	CPOX achieves higher H2 ratio with low CO2 emissions. Higher temperature and pressure used in TPOX.
Autothermal Reforming (ATR)	Combines POX and SMR to yield high H2 ratios. Operates in an adiabatic reactor with steam and oxygen, initiating oxidation and reforming simultaneously. CnHm + ½ nH2O + ¼ nO2 → nCO + ½ (n+m)H2	25% lower capital cost than SMR, Compact design. Fast start/stop. Catalyst and reactor improvements required.
Plasma Reforming (PR)	High-efficiency process utilizing thermal or non-thermal plasma (glow discharge, dielectric barrier discharge) to produce syngas at high temperatures with controlled energy input. Similar reaction to SR and POX, with plasma providing energy	Higher energy density. Controlled heat. Higher conversion efficiency. Enable fast reaction dynamics.
Biomass gassification	Converts coal or biomass into hydrogen, with byproducts like CO, CO2, and H2O. Coal partially oxidized with steam and oxygen, then syngas undergoes a water-gas shift reaction to maximize H2. Biomass gasification also produces CO and CO2, with steam injected to convert CO to H2. Similar to coal gasification, CO + H2O → H2 + CO2	Utilizes coal/biomass (N2, hydrogen sulfide, ammonia, oils, and tars. Conducts at high temperature (649–1480 °C) and pressure.
Biohydrogen Production	Biological methods utilizing algae/bacteria for hydrogen production from organic wastes. Processes include photolysis, photo and dark fermentation, and metabolic processing. Direct photolysis splits water using sunlight, while indirect photolysis involves CO2 fixation and H2 production via fermentation. Direct: 2H2O + light energy → 2H2 + O2 Indirect: C6H12O6 + 12H2O + light energy → 12H2 + 6CO2	Low environmental impact. Utilizes enzymes and algae (blue-green algae) for hydrogenation
Photocatalytic Water Splitting	Directly splits water using light energy and semiconductor materials, generating electron and hole pairs that oxidize water to form H+ ions, which then combine to form hydrogen. 2H2O + hv → 2H2 + O2	Semiconductor material essential for photon absorption. Conduct at room temperature. Requires sufficient light energy for operation.

.

3.3. Hydrogen Utilization Techniques

Hydrogen utilization techniques encompass various methods for consuming hydrogen as an energy source. Key technologies include fuel cells, which convert hydrogen into electricity efficiently, and hydrogen combustion, used in industrial and transportation applications. These techniques enable clean energy generation, making hydrogen a valuable resource for sustainable energy solutions.

3.3.1. Fuel Cells

Fuel cell systems convert chemical energy in fuels like hydrogen into electrical energy through an electrochemical reaction. The main types include PEM fuel cells, which are compact and efficient, ideal for transportation and portable applications, alkaline fuel cells, known for their high efficiency; and solid oxide fuel cells, which operate at high temperatures and are suitable for stationary power generation. Each type has unique strengths, depending on the application and operating conditions. Details of each technique including operating parameters, advantages, drawbacks, and applications are given in

Table 5. Analysis of fuel cell techniques [50,51].

Type	Alkaline	PEM	Solid Oxide	Molten Carbonate
Electrolyte	alkaline polymer membrane	Perfluorosulfonic acid	Yttria stabilized zirconia	Molten lithium, sodium, potassium carbonates
Temperature	40–90 °C	40–100 °C	600–1000 °C	600–700 °C
Efficiency (%)	45–60	55–65	55–60	50–60
Fuel Type	H2	H2	Natural, biogas	Natural, biogas
Oxidant	O2/Air	O2/Air	O2/Air	CO2/O2/Air
Application	Space systems Backup power transportation	RES integrations Portable power applications Transportation Backup power systems	Auxiliary power RES integrations Power system applications	Auxiliary power systems Electric utility RES integrations
Advantages	Lower costs Fast response Flexibility Low temperature	Reduced corrosion and maintenance Fast response time Low temperature	High efficiency Flexible fuel supply Gas turbine cycle applications	Fuel flexibility High efficiency Solid electrolyte CHP integrations
Challenges	High costs Impurity sensitivity	High sensitivity to impurities High cost	High temperature Slow response	High temperature, High corrosion maintenance

below.

3.3.2. Hydrogen-Based Combined Heat and Power (CHP)

CHP systems generate both electricity and heat from a single fuel source in one process. The main components of a CHP system include a power generation unit, a heat recovery unit, and a heating system. Heat produced during electricity generation is captured and repurposed for heating applications, thereby maximizing energy efficiency [47]. Unlike separate systems for electricity and heat production, CHP systems offer benefits such as high efficiency, lower fuel consumption, and reduced greenhouse gas emissions. Systems known as CHP 2.0 use renewable natural gas, biogas, and hydrogen, in contrast to traditional CHP 1.0 systems, which rely on fossil fuels [47]. Prime movers such as gas turbines and internal combustion engines generate significant amounts of recoverable heat, making them ideal for thermal energy applications in CHP systems. However, these prime movers typically operate on natural gas and emit harmful pollutants. While the use of pure hydrogen in combustion engines is still under development, hydrogen-enriched fuel mixtures offer a promising solution for reducing fossil fuel consumption.

3.3.3. Hydrogen Microturbines

Gas turbines generate electricity by mixing compressed air with fuel and igniting the mixture at high temperatures, producing a powerful combustion process. Therefore, hydrogen can be utilized as a fuel in a gas turbine for power generation. The heated air flows through the turbine, causing it to spin a shaft connected to a generator. This process converts the chemical energy of hydrogen into mechanical energy, which is then transformed into electrical energy [47]. Using pure hydrogen in gas turbines enables a zero-carbon emission process, playing a vital role in transitioning the power system towards a more sustainable and greener energy solution. However, a complete restructuring of the traditional gas turbine is necessary to make it feasible for hydrogen as a fuel. Differences in properties such as molecular weight, molecular size, flame speed, flame temperature, and lower heating value between traditional fuels like methane and hydrogen make this adoption challenging [47]. Another strategy in the industry is to utilize hydrogen as a mixture with natural gas and other hydrocarbons to minimize fuel consumption and carbon emissions.

3.3.4. Hydrogen for Industries

Hydrogen is emerging as a vital component in the decarbonization of various industries, particularly those that are hard to electrify or have high CO₂ emissions. Hydrogen can be used as a reducing agent in place of coal or coke in the steel-making process [52]. Green hydrogen, produced via electrolysis using renewable energy, can drastically reduce the carbon footprint of steel production. In productions such as Ammonia and Fertilizer, hydrogen acts as a key feedstock [53]. Furthermore, using green hydrogen can make ammonia production a more sustainable production scheme. Additionally, hydrogen is widely used in oil refining to remove sulfur and other impurities from fuels [54]. Transitioning to low-carbon or green hydrogen could help refineries reduce their overall emissions. Also, the cement industry generates significant CO₂ emissions through the calcination process and the combustion of fossil fuels. Hydrogen, as a clean fuel source, could help decarbonize the energy-intensive processes involved in cement production. Hydrogen can be utilized to provide the high temperatures required in processes like glassmaking, petrochemicals, and ceramics, potentially replacing natural gas or coal as an energy source.

3.4. Comparision of Cost, Associated Emissions, and Technology Readiness Level (TRL)

A comparative analysis of hydrogen generation, storage, and consumption methods, considering cost, associated emissions, TRL, and a brief analysis, are categorized in

Table 6. Comparison of cost, associated emissions, and TRL of hydrogen generation, storage, and utilization techniques [53,55,56,57,58,59,60,61,62].

Category	Technology		Cost (USD)	Associated Emissions (kg CO2/kg H2 or kg CO2/kWh)	TRL
Hydrogen Generation	Electrolysis	Alkaline	USD3.00–USD6.00/kg H2	0–1.5 (based on energy source)	8–9
		PEM	USD4.00–USD7.00/kg H2	0–1.8 (based on energy source)	8–9
		Solid Oxide	USD5.00–USD8.00/kg H2	Near zero (based energy on source)	6–7
	Steam Methane Reforming (SMR)		USD1.50–USD2.50/kg H2	9–12 (without CCS) 2–4 (with CCS)	9
	Partial Oxidation (POX)		USD1.80–USD3.00/kg H2	8–10 (depends on feedstock and CCS)	8
	Autothermal Reforming (ATR)		USD2.00–USD3.00/kg H2	2–4 (with CCS) 8–11 (without CCS)	7–8
	Plasma Reforming (PR)		USD5.00–USD10.00/kg H2	Near zero (based energy on source)	4–6
	Biomass Gasification		USD1.50–USD3.00/kg H2	Near zero (with CCS)	6–7
	Biohydrogen Production		USD2.00–USD4.50/kg H2	Near zero	4–5
	Photocatalytic Water Splitting		>USD10.00/kg H2	Near zero	3–5
Hydrogen Storage	Compressed Hydrogen Gas Storage		USD0.50–USD1.50/kWh	Near zero	8–9
	Liquid Hydrogen Storage		USD1.00–USD2.50/kWh	Near zero	7–8
	Metal Hydride Storage		USD5.00–USD10.00/kWh	Near zero	4–6
	Complex Hydride Storage		USD6.00–USD12.00/kWh	Near zero	3–5
	Physical Adsorption		USD2.00–USD6.00/kWh	Near zero	4–6
	Chemical Hydrogen Storage		USD3.00–USD7.00/kWh	Near zero	4–6
Hydrogen Consumption	Fuel Cells	Alkaline	USD1000–USD2000/kW	Near zero (using green hydrogen)	8
		PEM	USD2000–USD3000/kW	Near zero (using green hydrogen)	8–9
		Solid Oxide	USD3000–USD5000/kW	Near zero (using green hydrogen)	6–7
		Molten Carbonate	USD2500–USD4000/kW	Near zero (using green hydrogen)	6–7
	Combined Heat and Power (CHP)		USD1000–USD5000/kW	Near zero (using green hydrogen)	8
	Microturbines		USD700–USD1500/kW	Near zero (if using green hydrogen)	8

.

This provides both economic and environmental aspects of each technique in a comparative manner. Additionally, the TRL can be used to design a microgrid system by integrating the most suitable type of hydrogen technology for a specific microgrid application. This structured comparison aims to support the evaluation of hydrogen technologies in the context of advancing sustainable energy solutions.

4. Potential Hydrogen Applications on Future Microgrids

The role of hydrogen in future microgrids is highly adaptable, with different hydrogen technologies being applied based on the type of microgrid, its size, location, energy demand, and specific operational needs. Microgrids can be generally categorized by their application into residential, commercial, industrial, remote, islanded, urban, rural, military, and other types.

4.1. Commercial Microgrids

Commercial microgrids are established with the primal objective of serving medium-scale commercial and business corporations [63]. Examples of applications in this category include office buildings, business parks, universities, and shopping centers. The main purpose of these commercial microgrids is to enhance power system reliability, ensuring uninterrupted operation even during outages. Additionally, microgrids reduce energy costs and efficiently manage power distribution within various departments of the facility. Common current and future energy systems for these microgrids include solar PV, wind, small hydro, and CHP systems.

There is significant potential to integrate hydrogen technologies into commercial microgrids. These microgrids typically have high energy demands, requiring a reliable mix of energy sources. However, since most of the energy in microgrids comes from renewables, this can lead to fluctuations in power generation. Given that a large portion of the load in commercial microgrids is critical, incorporating hydrogen production methods like electrolysis can enable better demand management by balancing energy supply and demand. Electrolysis allows excess energy generated during periods of low demand to be stored as hydrogen, which can then be used during peak demand, enhancing system reliability without disrupting critical loads. In addition, almost all commercial power systems use backup power solutions. Hydrogen-based technologies, such as fuel cell systems, could serve as reliable backup options, ensuring continuous operation during grid outages. For instance, a commercial microgrid with rooftop solar panels and wind turbines could include a hydrogen storage system paired with fuel cells to maintain power supply when the grid is not operating. Moreover, commercial facilities like universities and shopping centers often require vehicles for daily operations. Implementing hydrogen-fueled vehicles could help reduce overall energy costs, making the system more efficient and sustainable.

Despite their potential benefits, hydrogen technologies often involve high upfront costs, which can be a challenge for commercial applications with limited budgets. However, creating a long-term strategy that accounts for energy savings and reduced losses can help offset these initial expenses. Additionally, hydrogen systems require dedicated space for operation, which may be difficult to accommodate in urban locations where many commercial microgrids are situated.

4.2. Industrial Microgrids

Industrial microgrids are designed primarily to serve large-scale industrial businesses. Applications in this sector include large factories, refineries, manufacturing plants, data centers, and business hubs [64]. Unlike commercial microgrids, industrial microgrids typically incorporate both traditional and modern energy systems, such as natural gas systems, solar PV, wind power, CHP systems, and diesel generators.

Hydrogen production industries can transition to SMR with carbon capture technologies as a step towards reducing fossil fuel dependency. Although this method is not a zero-carbon solution, it serves as a transitional technology for industries aiming to decarbonize. Additionally, some industrial microgrids are in regions with high renewable energy penetration such as PV, allowing the integration of large-scale electrolysis systems to produce hydrogen using excess renewable energy. The generated hydrogen can then be utilized in energy-intensive industrial processes, such as chemical production, and for power generation during peak load periods. Moreover, industrial microgrids can incorporate hydrogen turbines for rapid electricity generation, making them a viable option for backup power systems. One of the main challenges of hydrogen systems is the lack of viable storage solutions. However, given the large scale of industrial microgrids, they can integrate extensive hydrogen storage systems. This not only helps reduce the operational costs of the microgrid compared to using smaller storage systems but also offers the potential for long-term energy storage.

However, as in commercial microgrids, industrial microgrids also operate prioritizing the operating cost of the system. Introducing hydrogen technologies has very high associated capital costs. Furthermore, industrial microgrids consider safety as a primary objective in operations, where safety-related hydrogen techniques are still developing.

4.3. Residential Microgrids

Residential microgrids are identified as small power systems applied in an individual household or few residential units, which govern the supply–demand balance and stability of the system [65]. Residential microgrids typically consist of solar PV as the energy source with battery as the energy storage system to handle the power demands. This allows the residential microgrid system to operate as an islanded system during power failures at the main power grid, increasing the reliability of the system.

One promising approach is the use of electrolysis, where excess energy from renewable sources can be stored as hydrogen. Electrolyzer systems enable homeowners to store surplus solar energy generated during the day. This stored hydrogen can then be converted back into electricity during periods of high demand. However, careful consideration must be given to hydrogen storage in this setup. Currently, small, compressed hydrogen tanks are the most viable option due to their advanced technology. These tanks can be installed on-site, requiring less space compared to large battery systems. For hydrogen utilization, residential microgrids can employ hydrogen fuel cells to convert stored hydrogen back into electricity. Fuel cells are typically compact and operate quietly, making them well-suited for small-scale residential applications. Additionally, there is a growing interest in using stored hydrogen for hydrogen-powered vehicles, which is expected to become more common in the future. Hydrogen storage systems can be designed to meet the needs of hydrogen-fueled vehicles, allowing homeowners to directly use the stored hydrogen as a vehicle fuel.

To be able to easily apply in residential applications, there are several challenges to be addressed for hydrogen technologies. Hydrogen storage techniques need to be improved significantly in the future. All available storage techniques are highly costly and require advanced technical skills for the implementation process. Also, the safety concerns regarding hydrogen systems are very high and it is required to have a safety certification by external parties to verify concerns such as leakages.

4.4. Remote and Island Microgrids

Remote and islanded microgrids are small-scale power systems islanded from the main grid [66]. The size of an islanded microgrid can vary, typically ranging from small- to medium-scale systems. The primary reason for operating as an islanded microgrid is the complexity of connecting to the main grid. Examples of remote and islanded microgrids include islands, offshore industries, and rural households located far from the main power system. Commonly available energy sources in these locations include solar PV, wind systems, wave energy systems, diesel generators, and gas turbines.

There is significant potential for introducing some of these techniques into islanded microgrids, particularly in rural microgrids with agricultural applications or forestry. These communities can utilize their waste to produce hydrogen through processes like gasification. This approach not only provides a renewable energy source but also offers advantages in waste management and economic benefits to the community. Like other types of microgrids, the abundant renewable resources in rural areas can be harnessed by using electrolyzers to store excess energy as hydrogen, reducing reliance on other energy storage systems like batteries. In offshore microgrid applications, renewable energy sources such as wind and wave energy are highly available. Compared to battery systems, hydrogen storage can offer greater capacity since space is less restricted than in community or industrial microgrids. Additionally, cooling requirements for fuel cell systems can easily be met using the water available in offshore locations. Hydrogen storage also holds potential for remote microgrids, as it can provide reliable, long-term energy. In remote locations with sufficient space, compressed hydrogen is a viable option. For smaller island microgrids with limited space, liquid hydrogen may be a better choice due to its higher energy density. Furthermore, in rural microgrids where diesel generators are traditionally used, hydrogen fuel cells present an environmentally friendly alternative. CHP systems can also be integrated with fuel cell and electrolysis systems, addressing both the power and heat requirements of the community.

However, the capital cost related to hydrogen systems is challenging in rural and islanded microgrids. Even the cost of transporting can be huge for applications such as offshore microgrids and rural microgrids. Assistance from hydrogen-related expertise is required for the installation and transportation of hydrogen-related components.

4.5. Urban Microgrids

One potential future application of hydrogen in microgrids is within urban microgrids. These microgrids can range from medium to large, such as those serving city building complexes or parts of city infrastructure. Typical energy systems for such microgrids include solar PV and CHP systems, along with energy storage solutions like battery systems.

Urban microgrids are often integrated with city-level renewable energy initiatives. Electrolysis offers a way for cities to store excess energy from renewable sources and prevent grid overloading during peak production times. This stored hydrogen can later be used to generate electricity when demand is high. Hydrogen fuel cells can support urban microgrids by providing power during peak load periods, reducing the strain on the main grid. They can also serve as backup power sources for critical infrastructure, such as hospitals and data centers. As cities increasingly adopt hydrogen-based transportation solutions like buses, trains, and ships, urban microgrids can include hydrogen refueling stations to support local transit fleets, reducing the carbon footprint of transportation and aligning with city sustainability goals. Urban microgrids often still rely on natural gas for heating and CHP systems. Blending hydrogen with natural gas can help lower the carbon emissions of these systems while utilizing existing infrastructure.

However, implementing hydrogen infrastructure in urban areas faces challenges such as space constraints, high costs, and strict safety regulations. Additionally, community acceptance and regulatory policies present significant challenges for hydrogen installations in densely populated areas.

A summary of the discussed microgrid applications with potential hydrogen technologies is provided in

Table 7. Analysis of potential hydrogen applications on future microgrids [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66].

Type	Potential Hydrogen Techniques			Analysis
	Generation	Storage	Utilization
Commercial	Electrolyzer using excess RESs	Compressed hydrogen tanks Liquid hydrogen storage	Backup power Heating and cooling for buildings	Serve as a clean backup energy source and assist with heating/cooling, reducing emissions and reliance on grid power in commercial buildings
Industrial	Large-scale electrolyzer systems Biomass gasification	High-capacity pressurized storage Underground storage	Industrial process heating Power for heavy machinery	Hydrogen can support high-energy-demand processes, reducing carbon emissions in industrial settings and providing energy security
Residential	Small electrolyzer integrated with PV, Biogas reforming	Metal hydride storage, Compact hydrogen tanks	Home heating Fuel cells for backup energy	Can enhance energy independence and provide clean energy for heating, especially in remote residential areas
Remote	Electrolyzer powered by RES Gasification	Portable hydrogen storage solutions On-site pressurized storage	Primary power source Backup and emergency power	Enables off-grid, stable power supply in remote locations, improving energy security and reducing the need for fossil fuels
Urban	Centralized electrolyzes Integration with natural gas networks	Centralized storage hubs Distribution pipelines	Transportation applications (fuel cell vehicles)	Supports urban energy systems by providing fuel for transport, reducing urban emissions, and stabilizing grid demand through decentralized power sources

.

5. Discussion and Future Directions

Particularly in hydrogen generation, electrolyzer processes are becoming highly applicable in every type of microgrid due to their capability for renewable integration. Methods such as gasification and reforming are suitable for industrial and commercial microgrids due to their large production capacities and mature technology. In terms of storage, compressed gas is widely used in many microgrid applications, while liquid hydrogen is also being considered for industrial applications. However, processes such as absorption and chemical hydrogen storage are still in the development stages. For consumption, fuel cell types such as alkaline and PEM are already in use in many industrial as well as residential applications. CHP systems and gas turbines are commonly used in industrial applications.

Hydrogen technologies can be modified to various applications across multiple sectors, addressing the specific energy needs and challenges of each. This study finds that commercial microgrids are well-suited to integrate hydrogen technologies such as electrolysis using excess RESs, compressed hydrogen tanks, and liquid hydrogen storage. These technologies provide clean backup power and support heating and cooling systems in commercial buildings, thereby reducing emissions and reliance on grid power. For industrial microgrids, the findings of this study indicate that large-scale electrolyzer systems and biomass gasification, combined with high-capacity pressurized and underground storage, play a critical role. These technologies are instrumental in powering heavy machinery and industrial process heating, supporting energy-intensive operations while minimizing carbon emissions. In residential microgrids, this study identifies that small electrolyzers integrated with PV systems or biogas reforming, paired with metal hydride storage or compact hydrogen tanks, enable clean energy solutions. These systems enhance energy independence in remote areas, providing sustainable options for home heating and backup power. For remote microgrids, the findings of this study highlight that hydrogen-powered electrolyzers driven by RESs, gasification systems, portable storage solutions, and on-site pressurized storage offer significant benefits. They provide a stable off-grid energy supply for both primary and backup power needs while reducing reliance on fossil fuels. Lastly, in urban microgrids, this study shows that hydrogen technologies such as centralized electrolyzers, integration with natural gas networks, centralized storage hubs, and hydrogen distribution pipelines are highly beneficial. These systems support transportation applications, such as fuel cell vehicles, while stabilizing grid demand and reducing urban emissions through decentralized power sources. In summary, the findings of this study underscore hydrogen’s transformative potential in revolutionizing energy systems across diverse microgrid types.

There are several future directions for this research study where significant contributions can be achieved. Some of the key factors identified in this research are outlined below.

• Future studies should focus on improving the overall efficiency of hydrogen generation, storage, and utilization techniques. Although some of these techniques are environmentally friendly, their operational efficiency remains low.
• Reducing the costs associated with hydrogen technologies will also be crucial in future studies. This reduction will be helpful for the commercial integration of hydrogen.
• Scaling up production levels will also be essential for future research. Increased production capacity can, in turn, help reduce costs.
• The design and investigation of advanced material types for electrolyzers and fuel cell components are critical for improving efficiency, and cost-effectiveness. Suggestions such as high-performance catalysts, corrosion-resistant components, and low-cost membranes could significantly increase the application of hydrogen technologies.
• Furthermore, efficient and accurate modeling and control developments are essential for optimizing hydrogen production, storage, and utilization within microgrids. Advanced algorithms and modules for real-time monitoring and control can ensure system stability and the seamless integration of hydrogen technologies with RESs.
• The Internet of Things (IoT) and digital twin technologies also have huge potential for enabling hydrogen microgrids. IoT systems can enable real-time data collection and remote monitoring, while digital twins support predictive modeling and dynamic optimization of microgrid operations.
• Machine learning algorithms and AI-driven optimization techniques can forecast energy demand, optimize hydrogen production schedules, and reduce operational costs. AI can also assist in anomaly detection, fault diagnosis, and adaptive system management, ensuring high efficiency and minimal downtime.
• Advancements in electrolysis technologies, such as high-temperature and hybrid systems, can improve efficiency and integration with RESs.
• In terms of storage, innovations in advanced materials for metal hydrides, complex hydrides, and chemical hydrogen storage could provide safer, more compact, and cost-effective solutions for various applications.
• Optimizing fuel cells, CHP systems, and hydrogen-compatible turbines will be critical in expanding hydrogen’s role in transportation, industrial processes, and residential energy systems.
• Expanding hydrogen infrastructure, such as centralized storage hubs and distribution networks, particularly in urban areas, is essential for supporting large-scale adoption.
• Policymakers and industry stakeholders are encouraged to prioritize investment in research, pilot projects, and standardization to address challenges such as energy losses, safety concerns, and lifecycle emissions.

This literature review is conducted as part of a PhD study focused on developing an energy management system for an islanded hydrogen microgrid. Specifically, the study aims to achieve optimal fuel operation of fuel cell systems and optimal efficiency in the operation of electrolyzer systems. The authors have several publications related to hydrogen technologies, both prior to and during this study [67,68,69,70,71]. Furthermore, this PhD study is funded by a grant from the Blue Economy Cooperative Research Centre, located in Launceston, Tasmania, Australia.

6. Conclusions

This paper highlights the critical role of hydrogen technologies in advancing the performance of microgrids. By offering an updated review of hydrogen technologies and matching them with various microgrid applications, this study aims to provide a comprehensive understanding of the potential integration of hydrogen systems into microgrids. It is indicated that hydrogen can significantly improve the energy resilience and sustainability of microgrids, especially when integrated with RESs. This investigation suggests that selecting a suitable approach for each of hydrogen production, storage, and utilization are crucial to meet the unique needs of different microgrid applications. Overall, this research highlights the importance of integrating hydrogen technologies as a key operator in the transition towards a more reliable, flexible, and sustainable microgrid-based energy system.