Abstract

To fully explore the potential of hybrid pumped storage in enhancing the power supply flexibility of the hydropower-wind-solar system in a river basin, the time-varying characteristics of water head under the joint operation of hybrid pumped storage and cascade hydropower, considering time delay, are analyzed. A model for cascade hydropower and hybrid pumped storage operations, considering hydrological coupling characteristics, is established. The active power scenarios of wind and photovoltaic are extracted through the improved SA-CGAN model. Then, a multi-scenario-based stochastic optimization dispatch method for the hybrid pumped storage-cascade hydropower-wind-solar joint generation system is proposed. The whale migration algorithm is used to improve the solution efficiency. Through simulation verification, the flexible complementarity of hybrid pumped storage and cascade hydropower can effectively improve the economic and reliable power supply of the hydropower-wind-solar renewable energy base in the river basin.

Abstract

To address the challenge of rotor speed drift, large overshoot, and even DC microgrid instability caused by constant generator rotor speed inaccurate prediction in marine IRGT/SOFC all-electric propulsion systems, this study proposes a physics-informed Long Short-Term Memory framework to enhance transient prediction accuracy and robustness. This method integrates rotor nonlinear differential equations into the loss function, enforcing physical characteristic consistency while leveraging the LSTM memory capability to capture long-term nonlinear dependencies. The dataset from the mechanism and data-driven hybrid model which is validated in 2.5% error by experiment is used for training.
Results demonstrate that it reduces 55% Root Mean Square Error for key power parameters of system output power, with RMSE dropping from 107 to 52 and 183 to 83, respectively. For generator rotor speed, the RMSE improved by 50%, from 2.08 to 1.05, with an R² increase from 0.926 to 0.998, which mitigate rotor speed drift and overshoot, ensuring accurate and reliable predictions. Under dynamic conditions such as sudden load decreases, the PI-LSTM framework maintains stability and limits the prediction error for generator rotor speed to a maximum of 5 rpm, while the traditional LSTM suffers deviations as large as 30 rpm (1%). This work introduces a novel technical approach for next-generation marine hybrid propulsion systems, enabling highly accurate dynamic predictions and enhancing the reliability of marine microgrid operations.

Abstract

This study presents the development and experimental evaluation of a hybrid heating system with integrated electrical and thermal energy storage for domestic hot water production. In this study, the experimental system combined a solar heat collector to generate thermal energy and a photovoltaic (PV) panel to produce electricity. During periods of solar availability, the thermal energy was stored in a water tank, while the electricity was stored in a battery. A heat pump, powered primarily by the PV-charged battery, was used to heat the water to the desired set point after the initial solar heating phase. Experimental results demonstrated that the integrated system significantly reduced grid electricity use and achieved a high system efficiency of around 2.86. Furthermore, the incorporation of the PV-battery subsystem reduced grid power by approximately 23.9%, and the hybrid solar heating system achieved 66.4% electricity savings compared to a conventional electrical heater. This work confirmed the technical feasibility of hybrid solar heating systems in enhancing energy efficiency and promoting renewable energy utilization for residential hot water requirements.

Abstract

This study compares four different scenarios for sustainable aviation fuel (SAF) production using techno-economic analysis (TEA) to assess the Levelized Cost of SAF (LCoSAF). The SAF pathways assessed are: (i) Methanol-to-Jet sourcing carbon from post-combustion carbon capture (MTJ-PCC), (ii) Methanol-to-Jet sourcing carbon from biomethane (biomethane-MTJ), (iii) Hydrothermal Liquefaction of sewage biosolids (HTL), and (iv) Lignocellulosic biomass Fast Pyrolysis bio-oil (FP).
The TEA methodology draws on real-world feedstock and process descriptors and imposes elemental mass balances across critically reviewed unit processes, producing aviation turbine fuel with properties modeled to be within ASTM D4054 specification limits. The results show that SAF produced from lignocellulosic biomass fast pyrolysis has the highest potential, with an LCoSAF of 746 €/t. In comparison, the LCoSAF for Methanol-to-Jet (PCC), Methanol-to-Jet (biomethane), and Hydrothermal Liquefaction of sewage biosolids are 1,109, 2,263, and 5,153 €/t, respectively.

Abstract

Integrating gigawatt-scale offshore wind-hydrogen energy systems (OWHESs) is pivotal for the energy transition, yet their dynamic interactions and grid-support capabilities remain insufficiently explored. This paper addresses this gap by developing a real-time electromagnetic transient model of a 2 GW OWHES, which is implemented on a commercial real-time digital simulator (RTDS). Furthermore, a novel communication-free coordinated frequency control strategy is proposed, which synergistically harnesses the flexibility of the HVDC system, wind power plants, and electrolyzer plants. Real-time simulation results demonstrate the model’s ability to capture the OWHES dynamics. Moreover, results from a significant generation loss scenario demonstrate the proposed control’s superiority over existing methods, as it markedly improves the onshore frequency nadir and reduces the rate of change of frequency. This confirms its effectiveness in enhancing onshore frequency stability and showcases the potential of OWHESs as a valuable source of grid ancillary services.

Abstract

Coal power is still central to China’s electricity system but also a major source of emissions. With more renewables, the system needs stronger flexibility to stay reliable. This study uses a TIMES-based power system model of China’s 30 provinces. It characterizes coal technologies in detail, including part-load efficiency losses, retrofits, and early retirements. Two scenarios are compared: CN60 as the baseline, and CN60-DPS where coal acts as a flexibility resource. Results show that coal flexibility lowers the need for solar PV and storage, improves ramping, and brings earlier BECCS deployment. In the eastern regions, flexible coal power, together with storage and transmission, can meet net load ramping needs. Investing in coal flexibility offers a viable pathway for China’s power sector transition.

Abstract

Methanation is one of the most common microbial reactions in underground hydrogen storage (UHS). This biogeochemical reaction induces biofilm growth and mineral dissolution/precipitation, which in turn alter the reservoir pore structure and permeability, affecting the long-term multi-cycle operation of UHS systems. However, quantitative studies on biomass variation, the formation mechanism, spatiotemporal evolution, and key controlling factors of mineral precipitation during the injection and storage stages of UHS systems remain scarce. Based on PHREEQC software, this study developed a Darcy-scale reactive transport model integrating microbial reaction kinetics and mineral precipitation kinetics, followed by model validation. The model was used to analyze the spatiotemporal evolution characteristics of porosity during the hydrogen injection stage and the characteristics of UHS system parameters during the storage stage. The results show that mineral precipitation exhibits a heterogeneous distribution during the injection stage, and porosity is mainly influenced by mineral precipitation. During the storage stage, hydrogen consumption reaches its maximum after approximately 4.5 months, and the subsequent UHS system attains a stable state. This study provides a quantitative prediction tool for mineral precipitation in UHS systems and geo-methanation processes, and offers critical technical support for the site selection and evaluation of related projects.

Abstract

Global efforts to transition from fossil fuels towards a hydrogen-based future present Qatar with a strategic opportunity to leverage its fossil fuel endowment for the production of clean hydrogen for export. This paper applies the MUSE simulation platform to evaluate Qatar’s potential to consolidate its position as a leading low-carbon energy exporter, building on its established LNG capacity, under three distinct emissions mitigation scenarios. The analysis compares the relative competitiveness of LNG, hydrogen, and ammonia, highlighting the influence of carbon price trajectories and demand levels. Results show that under moderate emissions targets, hydrogen begins to substitute LNG at carbon prices of USD 420-460 per ton CO2, whereas under more stringent carbon budgets, hydrogen enters the market at lower carbon prices of 90-130 USD per ton CO2. Ammonia, by contrast, remains structurally uncompetitive against capitalizing in LNG and hydrogen under transition. These findings underscore the pivotal role of policy in shaping export competitiveness and demonstrate the value of model-based analysis in informing strategic policy discourse.

Abstract

LHTES systems provide high energy density and management in various applications. This study presents a numerical modelling and thermal analysis of a tube-in-tube LHTES using PCM as the storage medium. A 3D transient heat transfer model based on the enthalpy-porosity method was developed to simulate the coupled processes of conduction, convection, and phase change. A computational model, created with ANSYS FLUENT 2023 R1, was validated against experimental data. The study examined how the initial PCM temperature affects the charging time, heat transfer rate, and energy stored, while maintaining a constant HTF mass flow rate of 234 kg/h and an inlet HTF temperature of 333 K. Increasing the initial PCM temperature was shown to reduce charging time by boosting the initial heat transfer rate and extending the peak thermal response, thereby speeding up early-stage melting. After melting is complete, the heat transfer rate sharply drops to nearly zero. Importantly, while the charging rate varies, the total energy storage capacity remains consistent, with all systems reaching a similar maximum capacity. These results highlight that initial PCM temperature is a vital parameter for enhancing charging kinetics without impacting storage capacity, providing valuable insights for designing efficient TES systems.

Abstract

Indian distribution companies are undergoing significant structural and operational changes, driven by rising electricity demand and increasing penetration of distributed renewable energy (DRE) sources. Yet, large-scale DRE integration exposes distribution networks to challenges such as intermittency and peak load management. This study addressed these issues by virtually modelling a practical sub-11 kV distribution network in power simulation software using load-flow analysis. It evaluated the infrastructure readiness to accommodate future load growth with DRE integration, ensuring a smooth and sustainable transition.
Based on the model, active power and reactive power losses were determined, and transformers at risk of exceeding their rated loading during peak demand were identified. The findings indicated the threshold levels of rooftop photovoltaic penetration beyond which network reinforcement (such as transformer upgrades, voltage regulation, and reactive support) is essential. This study provides actionable guidance for distribution companies, demonstrating not only the benefits of DRE but also the tipping points at which proactive grid investment becomes mandatory to maintain reliability.