Grid Frequency Fluctuation Compensation by Using Electrolysis: Literature Survey

Abstract

This paper presents a novel literature survey on leveraging electrolysis for grid frequency stabilization in power systems with high penetration of renewable energy sources (RESs), uniquely integrating global research findings with specific insights into the Polish energy context—a region facing acute grid challenges due to rapid RES growth and infrastructure limitations. The intermittent nature of wind and solar power exacerbates frequency fluctuations, necessitating dynamic demand-side management solutions like hydrogen production via electrolysis. By synthesizing over 30 studies, the survey reveals key results: electrolysis systems, particularly PEM and alkaline electrolyzers, can reduce frequency deviations by up to 50% through fast frequency response (FFR) and primary reserve provision, as demonstrated in simulations and real-world pilots (e.g., in France and the Netherlands); however, economic viability requires enhanced compensation schemes, with current models showing unprofitability without subsidies. Technological advancements, such as transistor-based rectifiers, improve efficiency under partial loads, while integration with RES farms mitigates overproduction issues, as evidenced by Polish cases where 44 GWh of solar energy was curtailed in March 2024. The survey contributes actionable insights for policymakers and engineers, including recommendations for deploying electrolyzers to enhance grid resilience, support hydrogen-based transportation, and facilitate Poland’s target of 50.1% RESs by 2030, thereby advancing the green energy transition amid rising instability risks like blackouts in RES-heavy systems.

1. Introduction

As a result of the European Green Deal’s energy policy, there has been a phase-out of coal-fired power plants and replacement with wind and photovoltaic farms to ensure an adequate energy mix. The variability of weather-dependent renewable energy sources (RESs) and the increasing number of electric cars necessitate an increase in the hot/spinning unit reserve to stabilize the electric grid. With a higher participation of RESs in total power generation and the load change limitations of highly efficient grid-stabilizing units (such as coal-fired, nuclear, and even CCGT units), there may be a risk of blackout. Consequently, it becomes essential to explore energy storage solutions to compensate for frequency fluctuations in the electric grid. One solution that can be used to stabilize the frequency fluctuations in the electrical grid is to utilize energy storage systems like batteries. Based on experimental research on VRLA (valve-regulated lead acid) batteries with an absorbed glass mat (AGM), tests were conducted on a test bench under conditions of constant load current [1]. Another method for mitigating fluctuations in the power grid is the use of energy sources that operate stably over a much wider range than conventional power plants such as fuel cells [2]. Of course, when considering large-scale applications, more exotic storage systems can also be explored, such as an energy storage system that utilizes depleted coal mines for compressed CO₂ storage. This system is designed for electric grid balancing and further includes hydrogen generators and a methanation installation to produce synthetic natural gas [3]. Although fully renewable energy can be based on biomass sources, which should not pose problems for the power grid since it would largely utilize the same equipment as before, it encounters certain barriers related to economic, environmental, political, and technological aspects of developing bioenergy in Europe. Although bioenergy is sustainable and potentially cost-effective in Poland in the near term, providing numerous environmental advantages, the financial support in the new green certificate system is largely directed towards innovative bioenergy technologies rather than the large-scale co-combustion of biomass with coal in existing power plants, which currently prevails in Europe [4]. The advancement of renewable energy sources is driving the progress in energy storage technologies, including liquid air energy storage, which aims to enhance liquefaction modules to lower the energy costs associated with air condensation [5]. In fact, hydrogen is becoming crucial for sustainable transportation, necessitating robust and extensive refueling infrastructures. This paper presents data from the Cal State LA Hydrogen Research and Fueling Facility, evaluating station performance under various conditions and providing insights for modeling and infrastructure design [6]. The demand for hydrogen energy will surge due to the electrification of transportation driven by the EU policy banning the sale of new CO₂-emitting vehicles by 2035, further intensifying the pressure on power grid frequency regulation [7]. Energy storage in synthetic fuels, which require CO₂ for production, can benefit from the method described in the text involving the use of molten carbonate fuel cells (MCFCs) to concentrate carbon dioxide from natural gas combined cycle (NGCC) exhaust [8]. This technology not only enhances the production of electrical energy but also facilitates effective CO₂ recovery, which is essential for the process of producing synthetic fuels and can help reduce greenhouse gas emissions.

Integrating wind turbines into the electric grid presents several frequency-related challenges, stemming mainly from the inherent variability in and intermittency of wind energy. Wind turbines generate power based on wind speed, which can be highly unpredictable. This variability leads to fluctuations in power output, consequently causing frequency variations in the grid [9]. The grid’s frequency is directly linked to the balance between power supply and demand, and disturbances in this balance, often caused by the intermittent nature of wind energy, can lead to frequency instability. Traditional power plants, such as coal or natural gas facilities, have substantial rotating masses that contribute to grid inertia, aiding in stabilizing the grid’s frequency. In contrast, wind turbines, particularly those connected to the grid through power electronics, offer less inertia [10]. This reduced inertia can make the grid more susceptible to frequency swings, especially during abrupt changes in wind speed or sudden shifts in electricity demand. Wind speed’s unpredictability complicates accurate forecasting of wind power generation, which is crucial for grid management [11]. Operators must continuously adjust other power sources to keep the frequency within safe limits, which is more challenging with the unpredictability of wind power. The traditional grid is designed for steady, controllable inputs from power plants, and the fluctuating nature of wind energy can strain the existing grid infrastructure [12]. This situation necessitates upgrades in technology and control mechanisms to effectively handle these variations. One of the key requirements is maintaining frequency within prescribed limits. Thus, wind turbines must be equipped with grid-support technologies, like frequency response services, to help stabilize the grid during frequency deviations [13]. The sudden withdrawal of power during shutdowns can cause frequency drops. Conversely, restarting wind turbines and synchronizing them with the grid frequency presents its own set of challenges [14].

Germany is a good example of the issue, as it has faced several challenges related to grid frequency and stability due to the integration of wind turbines, especially from its large offshore wind farms. A key issue has been grid congestion, resulting from a lack of sufficient onshore power line connections. This bottleneck has led to a decrease in the output of offshore wind turbines in the North Sea, with a 9% reduction reported in 2023 compared to the previous year. This reduction is significant, as these turbines contribute a substantial amount to Germany’s renewable energy mix. The problems stem not only from the intermittent and variable nature of wind energy but also from the existing grid infrastructure’s limitations. To address these challenges, Germany has undertaken several initiatives. These measures encompass upgrading and expanding the transmission infrastructure, developing more advanced models for wind turbines and wind farms, enhancing the operational characteristics of wind farms, and integrating wind power output forecasting into utility control room operations. Moreover, new laws have been enacted to accelerate grid expansion, and there are ongoing efforts to improve the controllability of power lines through technological updates [15]. These initiatives are designed to improve the grid’s capacity to manage the variability and uncertainty associated with wind energy more effectively and cost-efficiently, which is essential for maintaining grid stability and maximizing the potential of wind energy.

The Polish power grid, managed by the transmission system operator PSE, consists of a high-voltage network (220 kV and 400 kV lines) spanning approximately 15,000 km, with interconnections to neighboring countries, including Germany, Czech Republic, Slovakia, Ukraine, Belarus, Lithuania, and Sweden (via a DC link). The grid’s structure is centralized, with major generation capacity historically concentrated in the south (coal-dominated regions like Silesia) and demand centers in the central and northern areas, leading to north–south transmission bottlenecks. As of 2023, installed capacity totaled around 60 GW, with coal (hard coal and lignite) accounting for about 70% of electricity production, though this share is declining due to EU emissions policies.

The pace of coal phase-out is accelerating under Poland’s Energy Policy until 2040 (PEP2040) and the National Energy and Climate Plan (NECP). Coal-fired capacity is projected to decrease from 32 GW in 2020 to approximately 10 GW by 2030 and to near-zero by 2040, with closures of inefficient units (e.g., 13 GW of lignite and hard coal plants scheduled for decommissioning by 2030). This transition is driven by rising EU ETS carbon prices (exceeding EUR 90/tCO₂ in 2023) and national commitments, but it faces delays due to energy security concerns and reliance on coal for baseload power.

Interconnection constraints exacerbate grid challenges, with cross-border capacity limited to about 10–15% of peak demand (e.g., 2–3 GW import/export capability with Germany). Insufficient north–south internal lines and asynchronous connections (e.g., with Ukraine) hinder renewable integration, leading to congestion and curtailments. In 2023, PSE reported over 1000 h of grid constraints, resulting in RES curtailments exceeding 1 TWh.

Renewable energy penetration has grown rapidly, from 13% of the electricity mix in 2019 to 26% in 2023 (primarily wind at 11 GW installed and solar PV at 15 GW). Projections indicate RES reaching 50% by 2030, with solar PV expected to double to 30 GW and offshore wind adding 6–11 GW. However, this growth strains the grid due to intermittency, with frequency fluctuations increasing by 20% in RES-heavy periods (e.g., nadir events below 49.8 Hz reported in 2023). These trends underscore the need for flexible solutions like electrolysis to mitigate instability during the coal-to-renewables transition.

Grid codes are technical regulations that define the requirements for connecting and electrical generators to the power grid and operating them, ensuring the safe, secure, and economic functioning of the electricity system. They specify parameters such as voltage, frequency, and power quality that facilities must meet to maintain grid stability, particularly with the integration of variable renewable energy sources (VREs) like wind and solar, which introduce intermittency and reduced inertia [16].

Grid codes matter because they facilitate the reliable integration of RESs into the grid, addressing challenges like frequency fluctuations, voltage instability, and system imbalances caused by high VRE penetration. Without these codes, the grid could face increased risks of blackouts, inefficiencies, and higher operational costs, as they mandate that generators not only connect but also actively contribute to stability through ancillary services. In the context of the European Green Deal and decarbonization goals, grid codes support higher RES shares by requiring capabilities like frequency response and voltage support, enabling market participation and reducing curtailment [16]. For Poland, as an EU member, aligning with these codes is crucial for cross-border energy trade and national grid resilience amid growing RES adoption [17].

Major rules and standards outline requirements for connection and operation, categorized by generator type and size. In Europe, the primary framework is the ENTSO-E Network Code on Requirements for Grid Connection of Generators (NC RfG, Regulation (EU) 2016/631), which classifies generators into Types A–D based on capacity and voltage level, with exhaustive requirements for frequency, voltage, and fault tolerance [18]. Key aspects include frequency control, voltage support, and fault ride-through (FRT).

Other standards include EN 50549 for low-/medium-voltage connections and IEC 61400 for wind turbines, covering power quality (harmonics per IEEE 519) and communication (SCADA) [16].

In Poland, grid codes are governed by the Polish Transmission System Operator (PSE) under the Energy Law and the Instruction for Transmission System Operation and Maintenance (IRiESP). For wind power plants (WPPs), requirements align with EU standards but show differences: active power reduction gradients (10% Pn/min), reactive power at power factor ≥0.95, and stricter FRT (recovery to 80% Un in 3 s). Polish frequency ranges are narrower (49.5–50.5 Hz continuous), reflecting legacy infrastructure, compared to broader European ones (e.g., 47.5–52 Hz in UK). These are less demanding on reactive power than those in Germany but are more rigorous with FRT duration, aiding stability but potentially increasing costs for RES developers [17].

Existing literature on electrolysis for grid frequency stabilization has demonstrated several strengths, including detailed simulations showing that electrolyzer systems (e.g., PEM and alkaline types) can provide fast frequency response (FFR) and primary reserves, reducing deviations by up to 50% in high-RES scenarios [19,20]. Strengths also include economic modeling in specific markets, such as France, where electrolyzers are evaluated for ancillary services like frequency containment reserves (FCRs), highlighting their rapid response times (milliseconds to minutes) compared to traditional generators [21]. Recent reviews emphasize trends in dynamic operation, electrical modeling, and integration with power-to-gas systems, underscoring improved efficiency under partial loads via advanced rectifiers and control strategies [19,22,23]. However, limitations persist: Most studies rely on simulations or pilot-scale pilots (e.g., 1–300 MW in the Netherlands or Australia), with scarce long-term empirical data from full-scale deployments, potentially overlooking degradation under variable loads or integration with aging infrastructure [24,25]. Economic analyses often indicate unprofitability without subsidies, and few address context-specific challenges in transitioning economies like Poland, where coal phase-out and north–south grid bottlenecks amplify RES curtailments [26]. Additionally, environmental trade-offs, such as lifecycle emissions from electrolyzer manufacturing, are underexplored [27].

These gaps highlight the need for a survey that integrates global technical and economic insights with region-specific applications. This literature review addresses this by synthesizing over 30 studies on electrolysis for frequency compensation, uniquely focusing on the Polish context—marked by rapid RES growth (targeting 50% by 2030), infrastructure limitations, and curtailments (e.g., 44 GWh solar in March 2024)—to provide actionable recommendations for policymakers and engineers, advancing grid resilience and hydrogen integration amid the green transition.

2. Electrolysis and Grid Balancing Services

One promising technology that allows power plants to increase flexibly and respond more quickly to the electric grid’s demands is the production of hydrogen by electrolysis. The variable load production of hydrogen, depending on the demand of the electric grid, can have a beneficial effect on stabilizing the grid frequency, while at the same time providing for hydrogen shortages associated with increasing hydrogen consumption in industry or fuel cell electric cars.

Figure 1 demonstrates that electrical systems with high wind power penetration experience significant frequency fluctuations without demand-side management (DSM), sometimes exceeding operational limits [28]. In contrast, systems with DSM, particularly those using electrolyzers as dynamic demand, show notably reduced frequency fluctuations, staying within operational limits. The system without DSM had a higher frequency deviation compared to the system with DSM. While real-world systems might not experience such extreme fluctuations due to the balancing effect of diverse wind farms, the simulation highlights the effectiveness of DSM, especially through adjusting key loads like electrolyzers, in stabilizing frequency with limited reserve resources.

Similarly, the proposed adaptive control strategy for the Virtual Synchronous Generator (VSG) demonstrates superior performance in mitigating grid frequency fluctuations compared to both traditional fixed-parameter strategies and unoptimized adaptive approaches [29]. Specifically, during a power fluctuation event at t = 2.5 s, the traditional strategy results in a peak frequency deviation of 50.186 Hz, while the proposed method reduces this to 50.143 Hz, indicating enhanced stability. Furthermore, when compared to the VSG adaptive control without particle swarm optimization (PSO), the frequency fluctuation decreases from 50.171 Hz to 50.143 Hz—a reduction of 0.028 Hz—highlighting the critical role of PSO in optimizing initial parameters for finer frequency regulation. These improvements underscore the strategy’s effectiveness in maintaining grid frequency closer to the nominal 50 Hz, thereby bolstering overall system resilience during dynamic disturbances.

The study detailed in Ref. [30] investigates the economic feasibility of deploying an electrolysis-based hydrogen production facility for providing grid balancing services, particularly in the realm of primary frequency regulation. The research employs the CEA’s Odyssey platform to model a grid-connected electrolyzer plant, with a specific emphasis on the French electricity market alongside the compensation schemes provided by the French transmission system operator (RTE). Two distinct scenarios are evaluated: the prevailing economic conditions set forth by RTE, and a sensitivity analysis assessing the conditions required for participation in frequency regulation to be economically advantageous. The results indicate that under current conditions, participation in frequency regulation is not economically attractive for hydrogen production plants. However, a significant increase in the compensation for capacity would be necessary to make it profitable. The study also suggests further research on different technical, economic assumptions, and compensation schemes in other markets.

Primary frequency regulation in Europe automatically balances electricity production and consumption by adjusting power generation in response to grid frequency changes. When frequency exceeds 50 Hz, indicating excess production, power injection decreases; when it falls below 50 Hz, indicating higher consumption, injection increases. This mechanism is demonstrated in data from 18 January 2012 showing European grid frequency changes every 10 s (see Figure 2).

Figure 3 illustrates the sequential evolution of power reserves in response to grid frequency deviations, highlighting the time scales for each category and potential integration points for water electrolysis. Primary reserves (also known as frequency containment reserves, FCRs) activate within seconds and provide balancing for up to 15 min to stabilize initial frequency deviations. Secondary reserves (frequency restoration reserves, FRRs) engage after approximately 3–5 min if the imbalance persists and last at least 60 min to restore frequency to nominal levels. Tertiary reserves (replacement reserves) activate within less than 60 min and involve standby power plants that can operate for up to 4 h until the underlying issue is resolved.

The “possible locations for water electrolysis” in Figure 3 refer to strategic integration points where electrolyzers can act as flexible demand-side responders. Electrolyzers are particularly suitable for second-to-minute-level responses, aligning with secondary reserves (3–5 min activation) and tertiary reserves (<60 min activation). For instance, alkaline and PEM electrolyzers can adjust load within milliseconds to minutes, enabling rapid downregulation (reducing power consumption to absorb excess grid energy) or upregulation (increasing consumption to balance shortfalls). This capability is demonstrated in simulations where electrolyzers stabilized grid frequency without relying on spinning reserves, with response times of under 10 min to meet transmission system operator (TSO) requests. In the context of Iceland’s regulatory power market, an 11.5 MW alkaline electrolyzer was modeled to provide up to 20 MW of upregulation, fitting seamlessly into secondary and tertiary reserve timelines due to its wide operating range (10–90% capacity) and dynamic performance.

When the system requires a tertiary or backup reserve, standby power plants, which have been idle, can be activated in less than an hour. These facilities are then brought online to deliver energy for potentially up to four hours, or until the initial issue causing the imbalance is resolved and rectified. The prior discussion about energy reserves serves as an illustration for a scenario where the frequency dips below the standard and energy injection is necessary to bring the frequency back to the normal operating level of 50 Hz. Conversely, a situation can also arise where there is an excess of frequency due to a supply that surpasses demand. This excess can happen due to unpredicted lower consumption across the network. During such times, it is the task of the transmission system operator (TSO) to decrease power usage throughout the network to rebalance the system. The reliability and prompt availability of these power reserves are crucial because they may need to be deployed rapidly and in various capacities. Collectively, these reserves should be ample to endure the longest foreseen grid outage to ensure a continuous electricity supply to consumers. This principle is encapsulated in a visual representation that details the sequential deployment of power reserves and encapsulates the discussions on reserve power (see Figure 3). It is vital for the integrity of the power system that each reserve be ready and operational to assume control seamlessly as needed.

A practical example is depicted in Figure 4, which illustrates the scenario for a 1 MW baseline system qualified for a 200 kW primary reserve (PR). The chart spans a duration of 30 min to clearly display the variations. The black dashed line (Y-axis on the right) represents the real-time grid frequency, which fluctuates within the range of ±50 mHz due to grid activity. The graph includes two primary curves (Y-axis on the left) defined by the green line (theoretical instantaneous set point) and the red line (acceptable degraded set point as per TSO standards). For the PEM water electrolysis plant to assist in regulating grid frequency, it must operate between the green and red lines at least 95% of the time to avoid penalties. These operations are periodically monitored, either remotely or on-site. This research primarily aimed to develop test protocols that more accurately reflect real operational conditions, as demonstrated in Figure 4. These protocols were designed to translate grid constraints into electrical load profiles, considering the economic necessity to maintain a power baseload. Each power profile features a sequence of ramp-up and ramp-down phases, along with intermediate stationary power plateaus of set durations. The fundamental concept is that the PEM water electrolysis plant consistently operates around a nominal power baseline, which is roughly 50% of its maximum power. Additionally, the system must be capable of providing grid support by adjusting power through various ramp-up/ramp-down sequences and stationary power plateaus as required. The time constants for these steps are defined by grid requirements and the specific type of reserve [31], see Figure 5.

Ref. [33] investigates the impact of different rectifier topologies on the energy efficiency and gas quality in alkaline electrolysis systems, particularly under partial load operations. The study highlights that conventional thyristor-based rectifiers with high current ripples consume significantly more energy and cause oxygen impurities in hydrogen production compared to newly designed rectifiers providing smoother direct current. Emphasizing the need for electrolysis systems capable of dynamic operation, the paper suggests that advanced transistor-based rectifier systems, such as the developed process current source, are better suited for dynamic operation, potentially reducing operational costs and improving system flexibility and efficiency.

Ref. [25] explores the integration of large-scale electrolyzers in enhancing power grid stability. It specifically focuses on the potential of hydrogen as an energy storage medium, especially in the context of the growing use of renewable energy sources. The study involves developing a generic electrolyzer model for real-time simulation on the RTDS, which has been confirmed with a 1 MW pilot electrolyzer situated in the Netherlands. The paper reveals that electrolyzers can positively impact grid frequency stability, reacting more rapidly to frequency fluctuations compared to traditional generators, thereby offering a promising avenue for grid support and ancillary services such as frequency and voltage stabilization. This research highlights the significance of electrolyzers in future power systems, especially with the growing adoption of renewable energy sources. Recent advancements further underscore the integration of renewable energy sources with electrolysis technologies, including alkaline, PEM, and solid-oxide systems, for efficient green hydrogen production and grid balancing [34].

In Ref. [35], the 300 MW PEM Electrolyzer in the N3 synthetic model is adapted to use droop, combined droop-derivative, or virtual synchronous power (VSP)-based fast active power regulation (FAPR) (see Figure 6) controllers for frequency support during under-frequency events, like the one caused by a 200 MW output reduction at the Gemini wind power plant. The electrolyzer’s active power absorption is adjusted to help mitigate frequency deviations. Figure 7 and Figure 8 illustrate the electrolyzer’s power and frequency responses under different FAPR controllers. The base case (red line) shows no frequency support, maintaining constant power consumption at 300 MW. With the droop-based FAPR controller, the electrolyzer reduces power demand, improving the frequency nadir value. The combined droop-derivative controller enhances the rate of change of frequency (RoCoF) response, with a quicker active power reduction. The VSP-based FAPR controller further improves RoCoF and nadir, but a non-smooth transition back to droop function after deactivation can cause undesirable frequency fluctuations. This study focuses on under-frequency events, noting that over-frequency scenarios are limited by the electrolyzer’s physical constraints and that FAPR adjustments should not reduce power below 30% of the rated value due to the characteristics of the PEM electrolyzer.

Sammani et al. [24] presents the adaptable functioning of an electrolyzer (see Figure 7) that delivers a 100 mHz frequency containment reserve (FCR). This electrolyzer’s activity was tracked for a duration of 10 min on 1 January 2017. During this period, grid frequency experienced variations at 10 s intervals. Correspondingly, the electrolyzer adjusted its power consumption in response to these grid frequency changes. Operating at a 25 MW capacity, the electrolyzer functioned at an ideal point, utilizing 55% of its total capacity to provide 11.25 MW for the primary reserve.

The analysis presented in Ref. [36] (see Figure 7a), which examines a multi-area system separation event, illustrates the substantial influence of high-efficiency (HE) fast frequency response (FFR) capacities, notably at levels of 500 MW and 1.5 GW. It reveals that a 500 MW electrolyzer could have effectively maintained the frequency above the under-frequency load shedding (UFLS) threshold of 49 Hz in both VIC and NSW, preventing the activation of 977 MW UFLS. Moreover, a 1.5 GW electrolyzer’s under-frequency droop response in VIC could have raised the frequency above the 49.5 Hz system protection value trigger (SPVT) threshold. This increase would not only have kept 190 MW of photovoltaic generation connected but also averted the 977 MW UFLS. The analysis also suggests that the electrolyzer’s response in VIC could have mitigated the sharp power flow rise in the Heywood interconnector, potentially preventing the activation of its protection mechanism and subsequent tripping. Overall, this scenario underscores the crucial role of FFR from high-efficiency sources in enhancing system resilience, especially in multi-area systems at risk of separation. Complementing this, multi-state load models for multiple electrolyzers have been proposed to optimize operations in long-term grid planning, treating them as smart loads to preserve system lifetime under variable conditions [37].

Detailed results of the system frequency response and the power consumed by AEL plants under different pre-contingency operating points can be found in Ref. [38]. The paper discusses the impact of Pini on the dynamic frequency response (DFR) method, using tests in the IEEE 9-bus system. Specifically, it focuses on the impact when Pini is close to its lower boundary (in this case, 3.4 MW compared to a boundary of 2.4 MW) at plant I installed at bus 6, which has a total frequency containment reserve (FCR) capacity of 10 MW. Overall, the tests demonstrate that operating alkaline electrolyzer (AEL) plants close to their power boundary reduces the virtual damping from the AEL plant, which weakens the frequency enhancement provided by the DFR method. Despite this, the contribution of the DFR method to system inertia reinforcement is not significantly affected (see Figure 8).

3. Discussion

This compilation of studies emphasizes the critical role of electrolysis and demand-side management (DSM) in stabilizing power grid frequencies amid high renewable energy integration. It reveals that DSM, particularly using electrolyzers as dynamic demand, markedly reduces grid frequency fluctuations. This is evident in simulations comparing systems with and without DSM. Additionally, the economic feasibility of electrolysis-based hydrogen production plants for grid balancing services hinges on increased compensation for capacity, as shown in a study modeling the French electricity market.

The role of primary frequency regulation in Europe is highlighted through data from the European grid, demonstrating how power generation adjusts in response to frequency changes. Another key aspect is the importance of standby power plants for tertiary or backup reserves. These plants, activated within an hour, are essential for managing grid imbalances and ensuring uninterrupted electricity supply.

Further, the study discusses the contributions of PEM water electrolyzers to grid frequency regulation. These electrolyzers must adhere to specific power requirements, as shown in a 30 min simulation. Advancements in rectifier technology in alkaline electrolysis systems are also noted. Modern transistor-based rectifiers offer improved energy efficiency and gas quality over traditional thyristor-based rectifiers, especially under partial load operations.

Large-scale electrolyzers have been found to significantly enhance grid stability. They respond more rapidly to frequency deviations than conventional generators, offering crucial support for grid services like frequency and voltage stabilization. The effectiveness of different controller configurations in a 300 MW PEM electrolyzer is also explored, demonstrating varying degrees of support for grid frequency during under-frequency events.

A study tracking a 25 MW electrolyzer providing a frequency containment reserve (FCR) reveals its adaptability in adjusting power consumption in response to grid frequency changes. The potential of high-efficiency fast frequency response (FFR) capacities, such as 500 MW and 1.5 GW electrolyzers, is underscored in their significant contribution to system resilience during multi-area system separation events.

Finally, the impact of alkaline electrolyzer (AEL) plants on the dynamic frequency response (DFR) method is assessed. Operating close to power boundaries reduces virtual damping from the AEL plant, affecting frequency enhancement by the DFR method. However, the contribution to reinforcing system inertia is noted as significant. This collection of studies collectively underscores the evolving role of electrolysis and DSM in enhancing grid stability and efficiency in an era of increasing reliance on renewable energy sources. A recent review further explores the current status and market challenges of electrolyzer systems in providing grid ancillary services, highlighting future directions for broader adoption [19]. In addition to the electrolysis-based approaches discussed in this survey, it is important to acknowledge the broader landscape of frequency control methods for power systems with high penetration of renewable energy sources (RESs). A recent review by Alam et al. [39] provides a comprehensive overview of frequency control techniques specifically for solar photovoltaic (PV) and wind-integrated systems. The review covers advanced methods such as inertia emulation, de-loading, and grid-forming controls, as well as the utilization of cutting-edge devices like energy storage systems, supercapacitors, and batteries. These technologies offer various advantages and face distinct challenges, contributing to ongoing efforts to enhance grid stability. For instance, inertia emulation techniques aim to mimic the inertial response of traditional synchronous generators, while energy storage systems can provide fast-responding reserves to counteract frequency deviations. The review also identifies key research areas and future directions, emphasizing the need for innovative solutions to address the complexities introduced by RES integration. By considering the insights from such comprehensive reviews, future studies on electrolysis for grid frequency stabilization can be better contextualized within the wider array of available technologies and methodologies.

4. Conclusions

In March 2024, 26.9% of Poland’s energy production originated from renewable energy sources (RESs), a decrease of 4.9% compared to the previous year. National Power System limitations resulted in 44 GWh from solar farms not being integrated into the grid [40]. This energy is challenging to forecast, leading to days of surplus production, requiring measures such as disconnecting additional energy supply or emergency energy export. In the first three months of 2024, the Polish grid operator disconnected gigawatts of solar power three times [41]. Instances like the disconnection of solar and wind generation on 23 April 2023, due to excessive renewable energy production, are becoming more common [42,43,44].

The implementation of electrolyzers at large wind and solar farms could offer a swift response to the variability in their energy generation. This alternative energy storage method could be converted back to electricity or used in fuel cell electric vehicles, aiding in the global transition to cleaner transportation.

Poland is part of Europe’s electricity network, involving both energy export and import. The increasing reliance on green energy makes consumption planning more challenging and risks underestimation or overestimation. With several emergency situations already encountered, it is evident that countries like Germany also face similar challenges, such as transporting wind energy from the north to the south due to inadequate interconnections [45].

The growing reliance on renewables, while beneficial for the environment, leads to potential instability in the electrical grid. This is evidenced by incidents of grid frequency instability and blackouts in places like Hawaii, California, and Australia [46]. The key issue is the inability of sources like wind and solar to provide the necessary grid stability, as they connect through frequency converters [47].

As countries, including Poland, aim to increase their green energy share—Poland targets 50.1% by 2030 [48]—the proportion of unstable energy sources grows. This necessitates exploring solutions to maintain grid stability, given the costly measures currently required by grid operators.

The significant rise in the proportion of unstable energy sources compared to stable, traditional ones necessitates urgent action to ensure system stability. As Poland’s renewable energy sources (RESs) grow, grid operators face the expensive decision of disconnecting these renewable sources or consumers in situations of overproduction. This practice seems counterintuitive to global trends promoting renewables, but turning off traditional power units can be financially detrimental due to emergency sales.

Considering the European Union’s regulation aiming to phase out sales of new CO₂-emitting cars by 2035 (subject to ongoing reviews), and Poland’s reliance on automotive fuels (approximately 28–30 million tons), the power sector is facing formidable challenges. To transition from combustion engines (with 35% average efficiency) to electric cars (97% efficiency) and compensate for the higher energy density of fuel (40 MJ/kg), Poland’s power production needs to increase by approximately 12.5 GW after full vehicle replacement. This equates to an annual 8% increase in household-installed power, assuming no other power sources are added. Hence, maintaining the balance of grid frequencies becomes a priority.

In response, green hydrogen production emerges as a multifaceted solution for improving planning, management, and stabilization of the electric system. This approach includes:

• Storing excess energy temporarily, eliminating the need to shut down production or resort to emergency exports.
• Utilizing hydrogen production to bridge energy shortfalls, thus preventing customer disconnections and the need for emergency energy imports.
• Reducing electric grid congestion by producing hydrogen near energy farms.
• Offering fuel for fuel cell cars as an alternative to combustion engines and electric vehicles.
• Sustaining the use of renewable energy and increasing its relative share to conventional sources.

In summary, the growing reliance on renewable energy sources is likely to bring grid stability challenges soon. Adopting green hydrogen production at energy farms and along grid nodes responsible for frequency balancing appears to be the most effective mitigation strategy. This method promises enhanced system planning and management, ensures energy stability, and supports the continued expansion of renewable energy without jeopardizing grid reliability.

While this literature survey provides a comprehensive overview of electrolysis applications for grid frequency stabilization, several limitations must be acknowledged. First, the analysis is predominantly based on simulation-based studies and pilot-scale implementations, with limited empirical data from full-scale, long-term deployments in diverse grid environments. This reliance on modeled scenarios may overlook real-world complexities, such as operational degradation of electrolyzer components under variable loads or integration challenges with aging grid infrastructure. Additionally, the economic assessments reviewed are context-specific, often focused on European markets like France and Germany, which limits generalizability to regions with differing regulatory frameworks, energy mixes, or subsidy structures, such as emerging markets in Asia or North America. Finally, the survey does not fully address potential environmental trade-offs, including the lifecycle carbon footprint of electrolyzer manufacturing and hydrogen storage, which could undermine the sustainability claims if not mitigated through advanced materials or recycling processes. Future research should prioritize experimental validation through large-scale field trials to bridge the gap between simulations and practical applications, particularly in grids with high renewable penetration exceeding 50%. Investigating hybrid systems that combine electrolysis with complementary technologies, such as battery energy storage or advanced control algorithms for predictive demand-side management, could yield more robust frequency stabilization strategies. Moreover, economic modeling should expand to include stochastic analyses incorporating variable renewable forecasts and dynamic pricing mechanisms, enabling more accurate cost–benefit evaluations across global contexts. Finally, interdisciplinary studies integrating environmental impact assessments with techno-economic analyses will be essential to ensure that electrolysis-based solutions contribute effectively to net-zero goals, potentially exploring innovations like solid-oxide electrolyzers for improved efficiency under fluctuating grid conditions.