Search Results (506)

Currently, hydrogen is considered a primary option for replacing fossil fuels across various processes, which can reduce greenhouse gas emissions and mitigate global warming. To achieve these goals, hydrogen should be produced using non-polluting processes, such as water electrolysis powered by renewable energy sources. This method requires feeding the converter with an unregulated voltage source. A quadratic step-down converter can be connected between a DC source and a Proton Exchange Membrane (PEM) electrolyzer to produce hydrogen. To mitigate variations in the generated output voltage and intermittent power supply to a PEM electrolyzer, a DC-DC converter is used as an interface. A converter model can be combined with a static or dynamic model of the PEM electrolyzer to yield switched models and, after averaging, linear state-space models. These models can be used to design robust controllers for green hydrogen production, thus significantly reducing greenhouse gas emissions. This work presents experimental and simulation results. Full article

The transition toward market-oriented renewable energy policies has increased the demand for flexible operation of biogas plants (BGPs), particularly under Japan’s Feed-in Premium (FIP) scheme. This study evaluates the technical performance and revenue potential of integrating hydrogen production into a dairy-manure-based BGP, focusing on steam reforming (SR) and electrolysis (EL) pathways. An energy system optimization model was developed using the Open Energy Modelling Framework (OEMOF) to simulate coordinated operation of biogas combined heat and power (CHP), hydrogen production, heat supply, and storage under electricity spot market conditions in Hokkaido, Japan. Sensitivity and scenario analyses were conducted to examine hydrogen production behavior, system-level resource allocation, and revenue performance under varying hydrogen prices and FIP levels. The results show that EL enables price-responsive switching between electricity supply and hydrogen production, resulting in dynamic hydrogen output and high sensitivity to conditions. In contrast, SR provides stable hydrogen production through continuous biogas utilization, achieving biogas throughput but limited responsiveness to price fluctuations. A System-level trade-off between conversion flexibility and direct fuel utilization efficiency was identified. These findings indicate that hydrogen pathway selection in farm-scale BGPs should be treated as a system design decision shaped by market exposure, operational objectives, and risk tolerance under the FIP framework. Full article

Small combustion installations (SCIs) burning solid fuels remain a major source of particulate matter (PM) emissions responsible for winter smog episodes in many European regions. This study aimed to develop and validate low-cost, micro-scale electrostatic precipitators (ESPs) suitable for retrofitting residential SCIs, and to quantify their PM removal performance under both controlled laboratory conditions and real-life field operation. Two ESP variants were designed and prototyped: (i) a tubular in-line ESP for installation at the boiler flue outlet and (ii) a disk (chimney-bypass) ESP mounted at the chimney outlet, with low energy demand. PM concentrations upstream and downstream of the ESPs were measured using standardized gravimetric, isokinetic sampling with recalculation to reference conditions, and the overall dedusting efficiency was determined from inlet/outlet concentrations. Laboratory testing showed that the micro-scale ESPs can achieve high dedusting efficiencies of approximately 90% under stabilized nominal-load operation. Field trials of the disk ESP in households and small residential buildings confirmed robust performance, with dedusting efficiencies of 70–82% under unsupervised user operation. In most cases, outlet PM concentrations were reduced below applicable Ecodesign thresholds. The results confirm that micro-scale ESPs are a technically feasible and effective “end-of-pipe” option for reducing short-stack PM emissions from solid-fuel heating, offering immediate air quality benefits where appliance replacement or fuel switching is limited by cost or practical constraints. This paper discusses the latest advancements in reducing PM emissions from SCIs. It introduces a prototype design for two types of micro-scale electrostatic precipitators (ESPs) that can be integrated into SCIs that burn solid fuels. The proposed technical solution utilizes an electrostatic method to effectively remove PM from flue gases. An established industrial technology has been adapted to meet the specific technical, economic, and safety needs of residential applications. The paper compares two design variants with a novel self-cleaning mechanism through laboratory testing and presents results from field trials. Findings confirm ESPs can substantially reduce PM emissions from SCIs. Full article

In the context of power electronic interfaces in photovoltaic (PV), fuel cell, battery, and microgrid applications, the low output voltage of the DC source necessitates a voltage-boosting inverter. This paper proposes a single-source seven-level switched-capacitor boost inverter, particularly for low-voltage applications. The proposed inverter has the capability to produce seven different output voltage levels, i.e., intermediate boosted levels, with a total gain of three times the input voltage. The inverter has the advantage of a reduced number of power switches, diodes, and a switched-capacitor unit, which allows for single-stage operation without the need for a second DC-DC converter. The operating principle of the proposed inverter is explained in detail with a complete switching state analysis, conduction path analysis, and output voltage generation. The capacitor size is calculated using a charge balance-based equation. The self-balancing capability is validated for mismatched initial voltages with a bounded steady-state ripple. To evaluate the performance of the proposed inverter in a more realistic scenario, the effects of non-ideal device characteristics are considered, and the efficiency of the inverter is estimated using a loss model. A predictive current control technique is applied to control the output current under inductive load conditions. The simulation results obtained in MATLAB/Simulink software validate the proper seven-level operation of the inverter, the self-balancing capability of the capacitors, improved output waveform quality, and current control. The proposed inverter can be extended to grid-connected applications, where conventional output filters can be applied to meet the harmonic standards. Full article

The integration of renewable energy sources, including photovoltaic (PV) and fuel cell (FC) systems, into AC grids has attracted immense research interest in recent times. Furthermore, incorporating these renewable sources of energy into medium-voltage grids is garnering increased attention because of the obvious benefits of medium-voltage integration at elevated power levels. Photovoltaic applications entail the arrangement of solar panels capable of outputting voltages up to 1.5 kV; nonetheless, fuel cells display restricted output voltage, with a maximum market range of 400 to 700 V. Hence, the efficient integration of renewable energy sources into low-voltage or medium-voltage grids demands the utilization of a step-up direct current (DC–DC) inverter and a converter for connection to the alternating current (AC) grid, in which an efficient step-up converter is critical for the medium-voltage grid. Therefore, this study presents a three-phase buck-boost split-source inverter (BSSI) that resolves the constrained output voltage of the fuel cells. This study focuses on modifying the configuration of a conventional three-phase split-source inverter (SSI) circuit by adding a few components while maintaining the inverter’s modulation. This novel circuit design enables the reduction in voltage strains on the inverter switch components and improves DC-link use in relation to a traditional SSI configuration. For an 800 bus, maximal voltage stress on the primary inverter switches is lowered when compared with the standard SSI that delivers entire DC-bus voltage to switches. A rectifier-based model is employed to simulate the behavior of a renewable energy source. Combining these advantages with the conventional modulation of the inverter offers a more effective design. The buck-boost split-source inverter (BSSI) was analyzed using three distinct modulation techniques: the sinusoidal pulse-width modulation scheme (SPWM), the third-harmonic injected pulse-width modulation (THPWM) scheme, and space vector modulation (SVM). The proposed analysis was validated through MATLAB-SIMULINK and practical outcomes on a 5.0 kW model. The practical and SIMULINK data were found to be closely aligned with the analysis. The circuit developed in this study also ensures efficient DC-to-AC conversion, specifically with regard to low-voltage sources, like fuel cells or photovoltaic (PV) systems. Full article

Hydrogen-fueled gas turbines face challenges related to flashback risk, nitrogen oxide (NO_x) emissions, and operational flexibility. In this study, a Center-Graded Spiral Micromixing (CGSM) combustor was designed and experimentally investigated to enhance the robustness of fuel–air mixing under hydrogen-rich conditions. The proposed CGSM concept employs spiral microtubes to induce curvature-driven secondary flows, promoting mixing through airflow-controlled mechanisms rather than relying solely on fuel jet momentum. Numerical simulations were conducted to qualitatively analyze the internal flow and mixing characteristics of the spiral microtubes, followed by pressurized combustor experiments at an inlet pressure of 0.3 MPa and elevated air temperatures. The experimental results demonstrate stable combustion of pure hydrogen under lean conditions, with NO_x emissions being maintained below 25 ppm, corrected to 15% O₂, without observable flashback or combustion oscillations within the designated operating range (from ignition to full load). The combustor further exhibits stable operation with blended hydrogen–methane and hydrogen–ammonia fuels, enabling online fuel switching without hardware modification. Application tests on an 80 kW micro-gas turbine indicate that the CGSM combustor can support stable operation across the full range of load conditions, from ignition to full-load operation, under both simple- and reheat-cycle modes, with performance characteristics that are consistent with established operational standards for micro-gas turbines. These results suggest that the CGSM concept provides a feasible micromixing strategy for hydrogen and hydrogen-rich fuels at a moderate pressure and micro-gas turbine scale. Full article

In this paper, frequency control of shipboard microgrids is achieved in the presence of measurement noise, dynamic uncertainty, and actuator faults. Measurement noise arises from incorrect signal processing, electromagnetic interference, converter switching dynamics, mechanical vibrations from propulsion and generators, and transients caused by sudden changes in load or generation. Actuator faults are caused by intense mechanical vibrations, temperature-induced stress, degradation of power electronic devices, communication latency, and wear or saturation in fuel injection and governor components. To regulate the frequency deviation under these challenges, a cross-entropy-based fault-tolerant model predictive control method, utilizing a discrete-time linear Kalman filter, is developed. Firstly, the discrete-time linear Kalman filter ensures that uncertain states of the shipboard microgrids are measurable in a noisy environment. Afterward, the model predictive control scheme is employed to obtain an optimal control input based on the measurable states. This controller ensures the frequency regulation of shipboard microgrids in the presence of measurement noise. Furthermore, a fault-tolerant control technique that utilizes the concept of cross-entropy is extended to provide a robust controller that verifies the frequency regulation of shipboard microgrids with actuator faults. To demonstrate the stability of the closed-loop system of the shipboard microgrids based on the proposed controller, considering the effects of measurement noise, state uncertainty, and actuator faults, the Lyapunov stability concept is employed. Finally, simulation results in MATLAB/Simulink R2025b are provided to show that the proposed control method for frequency regulation in renewable shipboard microgrids is both effective and practicable. Full article

The rise of carbon emissions from fossil fuel-based power generation has intensified the need for efficient and low-carbon energy systems. The global CO₂ concentration has risen from 285 ppm in the pre-industrial era to nearly 420 ppm today, and this contributes to a 1°C increase in average temperature. Therefore, in this article, a hybrid photovoltaic–thermoelectric generator (PV–TEG) system integrated with a reduced-switch multilevel inverter (MLI) is proposed. This enhances renewable energy utilization and power quality. The proposed PV–TEG model recovers waste heat from PV modules, which yields an overall efficiency improvement of approximately 2–8% compared to standalone PV systems. Further, the proposed MLI operates in symmetric (seven-level) and asymmetric (11-level) modes using eight switches. The system develops high-quality stepped output voltages with a minimum component count. Simulation work is performed, and the results show a peak output voltage of ±220 V with Total Harmonic Distortion (THD) of 7.2% under R-load and reduced THD below 5% under RL and variable load conditions. The integrated system demonstrates improved efficiency, reliability, and suitability for sustainable power generation and rural electrification. Full article

Solar-driven hydrogen production is a cornerstone of sustainable energy systems, yet its implementation remains intrinsically constrained by reliance on continuous illumination, limiting temporal control and compatibility with intermittent renewable sources. This perspective articulates the emerging concept of on-demand solar hydrogen generation, in which photon absorption is intentionally decoupled from hydrogen evolution through reversible charge storage and stimuli-responsive catalytic activation. We introduce a systematic classification of on-demand approaches across molecular, semiconductor, and device-level platforms, highlighting how these architectures enable programmable hydrogen release triggered by electrical, chemical, or thermal stimuli and sustained operation beyond illumination periods. Moving beyond a descriptive survey, we propose key performance metrics, including Switching Efficiency, Response Time, and Cycle Fidelity, to enable consistent evaluation and comparison of on-demand systems. Recent advances demonstrate substantial progress in charge storage, catalytic reversibility, and dynamic control, directly addressing the intermittency limitations of conventional photocatalytic and photoelectrochemical technologies. While challenges remain in kinetic synchronization, durability, and scalability, on-demand hydrogen concepts establish a coherent design framework for flexible and dispatchable solar fuels. By enabling integration with variable renewable inputs, this paradigm points toward adaptive and intelligent solar-fuel systems applicable from grid stabilization to off-grid and extraterrestrial environments. Full article

This study experimentally investigates the performance and exhaust emission characteristics of a low-speed two-stroke marine diesel engine operated with different controllable pitch propeller (CPP) modes during actual sea operation. Full-scale measurements were conducted on the training vessel T/S Baek-Kyung, equipped with a MAN B&W 5S35ME-B9.5 engine, operating under IMO Tier II fallback (FB) conditions. Two CPP control strategies were compared: a constant-speed mode, in which engine speed was maintained at approximately 162 rpm and load was controlled by propeller pitch, and a combinator mode, in which engine speed and pitch were jointly controlled. In the combinator mode, the propeller pitch reached saturation (100%) at approximately 25% load, and further load variation was governed primarily by engine speed. The analysis focused on an engine-load range of approximately 25–75% SMCR and evaluated propulsion performance, including specific fuel oil consumption (SFOC) and shaft torque, together with estimated brake-specific exhaust emissions expressed in g/kWh. The combinator mode achieved superior fuel efficiency under partial-load conditions, reducing SFOC by up to 10.5 g/kWh (5.4%) at 25% load, while increasing shaft torque by up to 47%, indicating improved engine–propeller matching. However, this benefit was accompanied by higher estimated emissions at low load, with BSNO_x increasing from 13.61 to 16.95 g/kWh. As engine load increased, differences in both performance and emissions between the two modes diminished. These results reveal a clear load-dependent trade-off between fuel efficiency and exhaust emissions in CPP operation and emphasize the importance of load-based switching or optimal joint control strategies under off-design conditions. Full article

This paper develops a theoretical model analyzing the optimal timing of switching from fossil-fuel-based energy to cleaner technologies in a stochastic environment. The economy consists of two interacting sectors: a backstop-production sector (e.g., solar panels), which uses both fossil fuels and backstop energy, and a consumption sector that initially relies exclusively on fossil fuels but can adopt a hybrid (cleaner) technology by incurring a fixed, irreversible investment cost. Both pollution accumulation and backstop accumulation are assumed to be stochastic. Our results indicate that the optimal timing for switching is significantly influenced by technological parameters, particularly the dependence on fossil fuels in post-switch production and the extent of technological gains in backstop manufacturing. Specifically, reducing fossil-fuel reliance and improving backstop technology both accelerate the adoption of cleaner technologies. We also find that uncertainty can either accelerate or delay adoption, depending on technological progress and intertemporal substitution preferences. These findings underscore the importance of policies that decrease fossil fuel dependence while fostering innovation in renewable energy technologies. Full article

This study examines how national electricity market structures condition the impact of carbon pricing on green innovation within the European Union. Using two-way fixed-effects panel models, we uncover a central paradox: although liberalized, price-signal markets exhibit the highest baseline levels of green innovation, the marginal effect of carbon pricing in these markets is weakest and often negative. This pattern points to an innovation-substitution effect, whereby market flexibility facilitates short-term compliance strategies, such as fuel switching, that crowd out investment in fundamental research and development (R&D) when carbon prices remain moderate. By identifying this mechanism, the study establishes electricity market structure as a pivotal moderating factor in the carbon pricing–innovation nexus and highlights a critical boundary condition for the Porter Hypothesis. The findings provide important insights for the design of sustainability policy mixes, demonstrating that institutional context plays a decisive role in translating economic instruments into sustained technological change. Effective climate policy therefore cannot be context-blind; instead, it must combine carbon pricing with tailored market design and direct support for long-term R&D to coherently advance the sustainability transition. Full article

Coastal shipping plays a critical role in meeting maritime decarbonization targets under the International Maritime Organization’s (IMO) Carbon Intensity Indicator (CII) and the European Union Emissions Trading System (EU ETS); however, operators currently lack robust tools to forecast route-specific carbon intensity and evaluate the causal benefits of fuel switching. This study developed a distribution-free causal forecasting framework for voyage-level Carbon Dioxide (CO₂) intensity using an enriched panel of 1440 real-world voyages across four Nigerian coastal routes (2022–2024). We employed a physics-informed monotonic Light Gradient Boosting Machine (LightGBM) model trained under a strict leave-one-route-out (LORO) protocol, integrated with split-conformal prediction for uncertainty quantification and Causal Forests for estimating heterogeneous treatment effects. The model predicted emission intensity on completely unseen corridors with a Mean Absolute Error (MAE) of 40.7 kg CO₂/nm, while 90% conformal prediction intervals achieved 100% empirical coverage. While the global average effect of switching from heavy fuel oil to diesel was negligible (≈−0.07 kg CO₂/nm), Causal Forests revealed significant heterogeneity, with effects ranging from −74 g to +29 g CO₂/nm depending on route conditions. Economically, targeted diesel use becomes viable only when carbon prices exceed ~100 USD/tCO₂. These findings demonstrate that effective coastal decarbonization requires moving beyond static baselines to uncertainty-aware planning and targeted, route-specific fuel strategies rather than uniform fleet-wide policies. Full article

The cement industry is at the core of global economic and infrastructure development accounts, but it also accounts for 7% to 9% of total emitting CO₂ For Pakistan, it is a major consumer of coal, emitting 8.9 Mt of CO₂ annually, resulting in nearly 49% of the country’s coal While several strategic initiatives are being adopted to lower conventional fuel consumption in the cement sector such as an increased shift towards solar energy deployment, initiating the shift from coal to alternate materials, but a well-regulated alternative fuel policy framework across cement production processes remains a clear gap in the industry’s decarbonization efforts. Given this challenge, this study conducts a scenario-informed quantitative evaluation using the Low-Emission Analysis Platform (LEAP) to explore the decarbonization potential of fuel switching in Pakistan’s cement industry, aligning it with NDC, Net-zero, and energy transition targets. The results reveal that swapping out coal and petroleum coke for cleaner alternatives would be necessary for reducing emissions by 13.5 Mt under the NDC scenario and 17.1 Mt for net-zero by 2050. However, achieving these targets requires a well-defined policy framework, regulatory support for Refuse-Derived Fuel (RDF) and Tire-Derived Fuel (TFD), building a sustainable biomass chain and quality control units, and capital investment in cleaner fuels. Full article

This study investigates the total carbon dioxide (CO₂) emissions from various types of passenger vehicles in five Latin American countries: Argentina, Brazil, Ecuador, Mexico, and Paraguay. The aim was to analyze to which degree CO₂ output can be reduced in Latin America by switching from petrol cars to electric cars. The vehicles analyzed include petrol-driven cars, short-, mid-, and long-range battery electric vehicles, fuel cell electric vehicles, plug-in hybrid electric vehicles, and hybrid electric vehicles. The study examines the total CO₂ emissions including battery production, vehicle manufacturing, and their operation, considering the energy grid mix of the selected countries for the year 2023. Using experimental data and considering production conditions yields more reliable results than previous studies. The results indicate that battery cars with the shortest cruising range using batteries produced in Europe and/or America generate the lowest levels of CO₂ emissions, regardless of the energy mix. However, the emission values vary across different countries. In countries with a predominant share of renewable energy for the electricity generation, such as Paraguay, Brazil, and Ecuador, battery cars are the most effective in reducing overall CO₂ emissions. Conversely, in countries like Argentina and Mexico, where renewable energy sources constitute a smaller share of the energy mix, the use of electric vehicles yields only a minor reduction in CO₂ output, while emissions of long-range vehicles with batteries produced in Asia even exceed those of internal combustion engine vehicles. Therefore, eco-friendly electricity generation is a prerequisite for eco-friendly use of electric cars and should therefore be the goal of every country. Full article