Generation System Research Articles

(Invited) A Hybrid Electrochemical and Catalytic Compression System for Direct Generation of High-Pressure Hydrogen at 350 Atmospheric Pressure

Hydrogen is becoming the center piece in the global de-carbonatization efforts in multiple industrial sectors. Gaseous hydrogen at high pressures in gas tanks is the most common approach for H2 storage, transportation and hydrogen refueling for fuel cell vehicles. Gaseous hydrogen at high pressures is also heavily used in the Haber process for ammonia production and hydro-cracking of heavy petroleum. In the long term, low-cost high pressure H2 will also play a critical role in the future long-duration grid storage for deep decarbonization and improved resilience.In this talk, I will share some recent development on a hybrid electrochemical/catalytic approach for direct generation of high-pressure H2 in collaboration with Pacific Northwest National Laboratory (PNNL). The hybrid system oxidizes water to oxygen at the anode, reduces V3+ to V2+ at the cathode, and stores proton in the catholyte during the “electrochemical charging” step. We demonstrated that the charged catholyte is then capable of generating H2 at >350 bar in the subsequent “catalytic discharging” step without any additional energy input. This concept leverages the electrochemical Nernst potential difference between the redox couple (V2+/3+) and the hydrogen evolution reaction and delivers a unique system that is capable of generating H2 at demand and at high pressure without any mechanical or electrochemical compression. We estimate a cost of <$0.19/kg-H2 for compression, representing >80% of the cost reduction compared to the traditional multi-stage compressor approach.

Monolithic Integration of Organic Solar Cell and Secondary Battery with Shared Electrode As a Photo-Rechargeable Energy Device

The solar cell-secondary battery energy system has been widely used as decentralized power generation and energy-storage system to reduce reliance on fossil fuel-based generation and mitigate fluctuations in solar cell energy supply. This typically involves power conversion by connecting two energy devices through charge controllers such as maximum power point tracker (MPPT) and pulse width modulator (PMW), which are technically mature and ensure reliable energy conversion and storage within the system. In the era of the fourth industrial revolution, characterized by the hyper-connectivity and hyper-mobility of the internet of things and wearable devices, solar-based integrated energy systems are emerging as a promising independent power source. To make devices more cost-effective, miniaturized, and energy efficient, many researchers are developing integrated energy devices that directly connect two energy devices without relying on a charge controller, a so-called "monolithic" form. However, most integrated devices reported to date still utilize a simple four-electrode structure. While this may visually resemble a monolithic device, it is functionally and structurally limited in its integration capabilities. To maximize the benefits expected from monolithic integrated devices, such as reduced process costs, miniaturization, and increased efficiency, it is essential to implement energy devices with three-electrode structures that share core components such as the electrode of the devices. In this regard, studies have been reported to realize a three-electrode energy device by utilizing the anode (or cathode) of a solar cell, which is a power generation device, as the electrode of an energy storage device, but there is a limitation that the energy density per unit area is low due to the use of a supercapacitor as the storage device, and the overall efficiency of the integrated device is low.In this study, we report on the design and implementation of a three-electrode integrated energy device sharing an electrode to improve the performance (e.g., areal capacity, energy efficiency). This integrated device uses an organic solar cell as the power generation device and a silver-zinc secondary battery as the energy storage device, and they share a silver electrode with each other. The shared silver electrode acts as a multifunctional layer that simultaneously serves as the positive electrode of the solar cell, the electrical connection between the solar cell and the secondary battery, and the cathode active material of the secondary battery. On the device perspective, by using a secondary cell instead of a capacitor, we have significantly increased the areal capacity. In order to further improve the efficiency of the integrated energy device, we applied the following three design strategies to the battery design. First, through the composition design of active ions in the electrolyte, the operating voltage of the secondary battery was matched to the same level as the maximum output voltage of the solar cell. This allows the solar cell to operate at its maximum power conversion efficiency when it charges the battery. Second, we improved the fast-charging characteristics of silver-zinc battery by ensuring that the area near the silver electrode surface is supersaturated with silver anion species during battery operation. This allows the secondary battery to accept the high-power density supplied by the solar cell at a low overvoltage, improving the efficiency of the integrated device. Finally, by applying a gel electrolyte with an optimized ratio of electrolyte components (gelling agent, hardener, salt, and plasticizer), we prevented the failure of the solar cell due to the penetration of electrolyte components and ensured the stable operation of the secondary battery. In conclusion, the aforementioned design improvements enabled the high-performance silver-zinc battery to be recharged near the maximum power point of the solar cell, achieving the highest photo conversion-storage efficiency (PSE) of any organic solar cell-based integrated energy system to date. In this presentation, the design and implementation of a solar cell-battery integrated energy device in a three-electrode configuration sharing a silver electrode will be presented in detail. In addition, secondary battery design strategies will be discussed to maximize the efficiency of the integrated device during high-power charging from solar cells.

Distributed multienergy and low-carbon heating technology for rural areas in northern China

In the context of China's “double carbon” policy and “rural revitalization” strategy, clean and low-carbon heating in rural areas of the northern China has become a key problem that needs to be urgently addressed. Practice has proved that “coal-to-gas” and “coal-to-electricity” projects have various limitations, such as high operating cost, high carbon emission, and high cost of distribution network upgrade, making them unsuitable for nationwide promotion. To address this issue, this research proposes a distributed multienergy and low-carbon heating (DMLH) system, which integrates the photovoltaic power generation, combined heat and power (CHP) system, heat storage, and newly developed multisource efficient heat pump (MEHP). The MEHP operates by simultaneously absorbing heat from air and waste heat sources of the CHP generation, providing a stable and efficient heat output. The multienergy complementary operating strategy of the DMLH system has been presented, considering variations of heating demand and environmental temperature. Comprehensive case studies were performed under typical and extremely cold winter scenarios to examine the effectiveness of the DMLH system. Simulation results revealed that 66.7 % of the operating cost can be reduced by the proposed system in typical scenario and the heat supply stability of MEHP has been considerably enhanced compared to a single-stage heat pump system. Furthermore, the DMLH system has low-level requirement of distribution network capability, which is conducive to promotion in the rural areas of northern China.

A Multi-Format, Multi-Wavelength Erbium-Doped Fiber Ring Laser Using a Tunable Delay Line Interferometer

This work demonstrates the use of an erbium-doped fiber amplifier (EDFA), a tunable bandpass filter (TBF), and a tunable delay line interferometer (TDLI) to form a ring laser that produces multi-format, multi-wavelength laser beams. The TDLI serves as the core of the proposed laser generation system. TDLI harnesses the weak Fabry–Pérot (FP) interferences generated by its built-in 50/50 beamsplitter (BS) with unalterable filtering characteristics and the interferences with free spectral range (FSR) adjustable from each of its two outputs with nearly complementary phases to superpose and generate a variable interference standing wave. The interferometric standing wave and weak FP interferences are used to form a spatial-hole burning to promote the excitation of multi-format and multi-wavelength lasers. The proposed system enables dual-wavelength spacing ranging from 0.3 nm to 3.35 nm, with a switchable wavelength position at approximately 1527 nm to 1535 nm, providing flexible tunability.

Modeling of hydropower plant in islanded mode for different operating conditions

Most countries have access to abundant water resources through rivers and canals. Utilizing this renewable resource, electricity can be generated in an environmentally friendly manner without causing pollution. In rapidly developing countries like India with the abundance of natural resources and diversities, the development of Hydropower is gaining in importance to meet the country’s demand. This work discusses the different operating conditions that may occur in real time of the standalone hydro power generation system. In this work, various operating conditions are considered in terms of faults and disturbances that occur on the load side. These effects of faults and disturbances may be caused in the generating side. It takes into consideration some major events from the load side i.e. small disturbance, load addition, load rejection, large disturbance. In this work, the above-mentioned objectives are achieved by creating a model of a hydro power plant in MATLAB Simulink and keeping its operating environment same, simulate different scenarios related to load side, and study its effect on the generator and generating system. This is achieved by changing the load side for different conditions like introducing a small fault into the system, changing the load on a larger scale, etc The conditions that are introduced are simulated in a period of 10 s time frame. The reaction of the generating side from these conditions is recorded and plotted on parameters that can show the effect directly on the generator.

Distributed generation powered by smart grids

Smart grids are conceived as a system to optimally manage the set of means that are part of the electricity grid to achieve adequate performance in the distributed generation system in the supply of quality electricity. The objective of this study was to analyze the importance of smart grids in distributed generation and how the elements that make it up allow the implementation of this technological innovation. The methodology was based on the mixed approach, of experimental design with descriptive scope and documentary support, the experimental method was applied for programming with the use of Homer Pro software. The results were obtained by simulation, carried out for a distributed generation system with a consumption of 197.78 kWh/day, obtaining important data such as the amount of kW of electricity generation supplied in a year, with a value of 98,114 kWh/year.

The Combination of Electronic Structure and Lattice Strain Engineering for Multi‐Powered Hydrazine‐Assisted Seawater Electrolysis System at High Current Densities

AbstractThe utilization of hydrazine in aiding water electrolysis presents a promising avenue for achieving highly efficient hydrogen production through energy conversion. Herein, bifunctional electrocatalyst of urchin‐like iron, nickle‐codoped cobalt phosphide supported on Ni foam (FeNi‐CoP/NF) is reported. Benefitting from the combined electronic structure and lattice strain engineering by Fe and Ni‐ codoping, the hydrazine‐assisted seawater electrolysis assembled with FeNi‐CoP/NF as both electrodes can achieve an industrial‐level current density of 1.5 A cm−2 at a record‐setting voltage of 163 mV at 70 °C and sustain stable operation for hundreds of hours in seawater environment. The existence of a potential coincidence region lends credibility to the feasibility of implementing self‐activated hydrazine‐assisted seawater electrolysis. Based on theoretical calculations, the separate and synergistic effects of electronic structure and lattice strain engineering are investigated and an integrated illustration of these two strategies on enhancing hydrogen evolution and hydrazine oxidation activity is provided. Moreover, an innovative multi‐powered hydrogen generation system featuring a direct hydrazine fuel cell, rechargeable Zn‐hydrazine battery, and hydrazine‐assisted seawater electrolysis is proposed, underscoring the unique advantages of hydrazine oxidation reaction and its prospective contribution to electrochemical energy conversion technologies powered by sustainable sources.

Experimental study on a solar thermoelectric power generation system under non-uniform irradiation

Non-uniform irradiation caused by high light concentration significantly affects the performance of the solar thermoelectric power generation system, but the research remains at the theoretical stage. This paper establishes an experimental setup for the solar thermoelectric system and conducts a comprehensive experimental study of the system operating under non-uniform irradiation. The temperature, power and efficiency of the systems are tested for different input powers, cooling methods and structures, and irradiation uniformity. The results indicate that the output power of the solar thermoelectric system slightly increases and then decreases as the irradiation uniformity increases. The system’s output power is minimized when the irradiation uniformity approaches 100%. The optimum irradiation uniformity of the solar thermoelectric system is 47.4% and the maximum efficiency is 1.495%, which is an improvement of 7.6% compared to the efficiency of 98.4% irradiation uniformity. The performance of the solar thermoelectric system can be further improved by using a double-layer TE structure. At a concentration ratio of only 12.4, the double-layer system connected in series achieved a maximum efficiency of 2.06%, which is 0.55% higher than the single-layer system. The importance of optimizing irradiation uniformity to improve system performance is experimentally revealed. These results are important for clarifying the operating principle of the solar thermoelectric system under non-uniform irradiation and can guide the subsequent design of high-efficiency solar thermoelectric systems.

Virtual coupling control of photovoltaic-energy storage power generation system for efficient power support

The key to achieving efficient and rapid frequency support and suppression of power oscillations in power grids, especially with increased penetration of new energy sources, lies in accurately assessing the inertia and damping requirements of the photovoltaic energy storage system and establishing a controllable coupling relationship between the virtual synchronous generator and the main network. In this paper, the inertia and damping requirements of the photovoltaic energy storage system are estimated using frequency safety warnings and power oscillation suppression constraints. Furthermore, the oscillation characteristics of the power system, which include photovoltaic and energy storage in the presence of periodic load disturbances, are analyzed. Based on this analysis, a coupled virtual synchronous controller for energy storage is proposed. This controller employs a forced oscillation suppression technique through natural frequency shifting, and establishes a controllable power coupling relationship between the photovoltaic energy storage system and the main network to achieve the desired frequency shift. Finally, a simulation system incorporating conventional generators and a photovoltaic energy storage system controlled with the proposed strategy is built to test the frequency support and power oscillation suppression behaviors of the grid-connected power generation system.

Parametric optimization for enhancing the electrical performance of hybrid photovoltaic/thermal and thermally regenerative electrochemical cycle system

Globally, the efficient utilization of solar energy has garnered significant attention. A hybrid system of photovoltaic/thermal (PV/T) modules integrated with thermally regenerative electrochemical cycle (TREC), i.e., PV/T-TREC has emerged recently and shows higher efficiency for solar-to-electrical conversion than a standalone PV system. However, there is a trade-off between the electricity generation from PV/T and TREC because the thermal energy from PV/T degrades the efficiency of the PV/T but improves that of TREC. Previous studies have failed to investigate this problem. This study therefore focuses on the key parameters that significantly affect the thermal output of PV/T, i.e., different PV materials, air gaps, heat storage tank volumes, and working fluids to investigate the maximum electrical efficiency of the hybrid system. The mathematical and transient-state numerical models are developed with the validation/refinement from the experiments. The results show that the hybrid system with PV material of cadmium telluride presents the best overall electrical efficiency of 25.37 %. The case of the air gap fosters the solar-to-electrical conversion. The electrical efficiency versus heat storage tank volume shows a convex curve, peaking at 200 L. The nanofluid performs the best. This study may help guide the practical application of such a high-efficiency electricity generation system.

Optimization study of a high-proportion of solar tower aided coal-fired power generation system integrated with thermal energy storage

Solar aided coal-fired power generation technologies have proven to be effective in reducing fossil fuel consumption and greenhouse gas emission. In this research, a high-proportion solar tower aided coal-fired power generation system integrated with thermal energy storage system is proposed. According to the constraint conditions, the integration scheme with the highest solar coupling capacity is obtained, and its thermodynamic, economic and environmental performances are researched. The results indicate that the solar coupling capacity that can be accommodated by the 660 MW coal-fired unit after parameter optimization is 339.532 MWth. As the load rate decreases, the power generated from solar and solar to electricity efficiency gradually decreases while the proportion of power from solar increases. The proportion of power from solar reaches a maximum of 24.28 % at 50 % load rate. The effects of different thermal energy storage hours on the levelized cost of electricity are investigated, and the results show that the lowest levelized cost of electricity is only 41.62 $/MWh in the high-level direct normal irradiance area. The new system can reduce about 272,921 tons of CO2 emissions in a year at 100 % load rate. This study contributes to further promoting the development of a high-proportion solar aided coal-fired power generation system and realizing the low-carbon transition of coal-fired power generation industry.

A Champernowne Adaptive Filter-Based Control of Grid Interactive Solar PV with Power Quality Enrichment

This work presents a variable step Champernowne Adaptive Filter (VS-CAF) based control architecture for a grid-integrated solar photovoltaic system. The control structure is implemented to successfully synchronize the two-stage solar photovoltaic at the point of common coupling where the source and domestic loads are connected. The control architecture ensures solar power injection and improvised power quality at the unity power factor. Moreover, the control structure provides only the balanced positive sequence fundamental sinusoidal source currents at solar irradiation alteration and load disturbances. The VS-CAF is exploited to estimate the peak of the fundamental component out of the harmonics-rich domestic load currents. To examine the efficacy of the suggested control technique, a 40 kW solar photovoltaic is simulated using MATLAB/Simulink. The performance assessment of the grid-tied solar generation system is carried out at solar irradiation alteration, zero solar irradiation, and detachment of one phase of the three-phase load. Various simulation results are carried out to verify the successful integration of solar photovoltaics into the three-phase grid following the IEEE-519 standard and satisfactory performance during various working conditions. Moreover, the simulation results are also verified with real-time results taken from the Opal-RT simulator.

Design and optimization of space nuclear power system with sCO2 Brayton cycle on Mars

As human exploration of outer space deepens, the demand for space power increases. This requires not only higher thermoelectric conversion efficiency but also a more compact system. Space nuclear power based on the sCO2 Brayton cycle is better suited for the surface of Mars due to its high efficiency and low ratio of mass to electric power. This paper designs a 6 MWt sCO2 Brayton cycle power generation system, and the following system configurations are mainly studied including Simple Heat Recovery Cycle (SRC), Re-Compress Heat Recovery Cycle (RC), Reheating Heat Recovery Cycle (RRC), and Reheating Re-Compress Cycle (RHRC). A thermodynamic calculation model of the system was developed based on the aforementioned cycle configurations. Additionally, a quality assessment model was developed separately for each component within the system, according to its respective category. The effects of parameters such as temperature, compressor pressure ratio, and bypass ratio on the system efficiency and total system mass are also examined for each of the four-cycle configurations. The study conducted a global multiparameter optimization using a genetic algorithm to optimize system efficiency and the ratio of mass to electric power. The RHRC configuration achieved the highest cycle efficiency at 39.47%, while the SRC cycle had the lowest system efficiency at 35.46%. The RRC configuration had the minimum ratio of mass to electric power at 7.419 kg/kWe with an efficiency of 33.13%.

Super-twisting ADRC for maximum power point tracking control of photovoltaic power generation system based on non-linear extended state observer

This paper proposed a new method for maximum power point tracking in photovoltaic power generation systems by combining super-twisting sliding mode control and active disturbance rejection method. An incremental guidance method is used to find the point of maximum power. The non-linear extended state observer is applied to estimate the unmodeled dynamics and external disturbance. The ADRC based on a super-twisting sliding mode is designed to bring the state variables to the desired state. In the next step, the stability of NESO and ADRC are theoretically proved. Finally, the simulation results have been compared with the results of the PI controller, classical sliding mode control, and terminal sliding mode control (TSMC) presented in other articles. The results show the effectiveness and superiority of the proposed method.Also, to check the performance of the proposal method in real-time, real-time results have been compared with non-real-time results. The results obtained from the real-time and non-real-time simulations exhibited a minimal difference. This fact indicates the high accuracy of the modeling and simulations performed. Indeed, the mathematical models and non-real-time simulations have been able to accurately mimic the actual behavior of the photovoltaic system under various operating conditions.

Study on reactive power compensation for a grid connected photovoltaic power generation system

Study on reactive power compensation for a grid connected photovoltaic power generation system

Optimization and Feasibility Analysis of Rooftop Solar Photovoltaic (PV) Power Generation System Design

Optimization and Feasibility Analysis of Rooftop Solar Photovoltaic (PV) Power Generation System Design

MtArtGPT: A Multi-Task Art Generation System With Pre-Trained Transformer

MtArtGPT: A Multi-Task Art Generation System With Pre-Trained Transformer

Small signal stability analysis of a wind power system integrated with a multi-band supplementary damping controller

Abstract With the integration of wind turbines represented by doubly-fed induction generators (DFIG) into the power system, the inertia level of the system decreases sharply, and small disturbances can easily cause low-frequency oscillation (LFO) in the system. In this paper, we propose a multi-band supplementary damping controller (MBSDC) directly applied to the active power control link of the rotor-side converter in the wind power generation system. We establish a linearized model for DFIG integrated with the power system, calculate eigenvalues, and screen out multiple electromechanical oscillation modes to be suppressed. Based on the calculation results, an MBSDC is designed to suppress LFO, and we propose a parameter-setting algorithm to enhance the suppression effect. Taking the New England 10-generator 39-bus system containing DFIG as an example for simulation verification, the results show that the MBSDC and parameter setting algorithm designed in this paper can effectively suppress LFO.

Capacity optimization of a large-scale photovoltaic power generation system coupled with hydrogen production and storage based on economic analysis

Abstract The renewable energy system coupled with hydrogen storage has proven to be a suitable method to reduce the variability of output power and meet stable hydrogen supply demand. However, the excessive cost of hydrogen through water electrolysis using renewable energy restricts its application, and the capacity configuration of electrolyzers and gaseous hydrogen storage tanks is affected by the immoderate reliance on engineering experience, leading to the unbalance of generation side and hydrogen demand side. In this study, a 300 MW photovoltaic power generation system has been proposed to fit the raw material demand of a synthetic ammonia plant, i.e., around 1000 kg/h hydrogen. A simplified mathematical model including an electrolyzer and a hydrogen tank is proposed to get the best capacity configuration. The levelized cost of hydrogen (LCOH) is chosen as an optimization function, and a particle swarm optimization algorithm is adopted to get the optimal results. The simulation results indicate that the optimal capacity configuration is 176.36 MW for the electrolyzer and 14644.2 Nm3 for the hydrogen tank, and the LCOH is 30.31 Yuan/kg. Compared with the empirical model, the LCOH based on the optimization model is 8.87% lower than that of the empirical model, indicating better economic benefits of the optimization model.

Coupling study of onboard power generation system of Magnetohydrodynamics enhanced Brayton Cycle

Closed cycle power generation systems offer a possible solution to meet the high electricity needs of hypersonic vehicles, but the power generation is limited by the finite cold source and cycle temperature. Introducing two-phase flow liquid metal (LM) MHD power generation based on Closed-Brayton-Cycle (CBC) is a potential solution that can enhance the thermal-electricity conversion process at the system level. However, it is difficult to reflect the complex coupling relationship between the power generation system and the vehicles propulsion system and the limitations of finite cold sources by relying only on ideal system analysis, especially the contradiction between the void fraction and the mass flow of working fluid after the introduction of LMMHD power generation. The study utilizes a multi-dimensional model to evaluate the performance of the CBC enhanced by multi-stage LMMHD generators coupled with hydrocarbon fuel scramjet. The multi-stage mixing-separation LMMHD generator is proposed to decouple the void fraction of the MHD channel and the wall cooling process, and control the void fraction by change number of stages. The calculation result indicate that the void fraction significantly affects the overall power generation performance, including output power, performance boundary, etc. Increasing the void fraction is beneficial, and the optimal void fraction is 0.65. At the same Mach number, the fuel cooling capacity available to the system increases with the fuel equivalence ratio, resulting in higher total power output. The maximum Mach number for thermal protection of the combustor walls alone may surpass 9.5. For gas void fractions of 0.35/0.5/0.65, the maximum power generation reaches 182.8/167.1/156.9 kW, respectively. The novel system is compared with other advanced thermal-electricity conversion cycles under nearly the same conditions and demonstrated clear performance advantages.