Advanced Power Generation Research Articles

Instantaneous Power Control Within an Advanced Power Generation Center for More-Electric Aircraft Applications

This article presents an instantaneous power control (IPC) to regulate the power flow of a back-to-back converter (BTB converter) within an advanced power generation center (APGC) for more-electric aircraft applications. The APGC essentially is composed of two power generation channels (each channel is with a permanent magnet generator driven by two different engine shafts and an ac/dc converter) with a BTB converter connected in between. The BTB converter allows power transfer between these two channels and thus two different shafts of an aircraft engine. Control of the power transfer was achieved using the phase current synchronization (PCS) method where current flowing through the BTB converter is controlled to be in phase with that of one generator within the APGC. In this article, we propose an improved IPC technique. Compared with the previously proposed PCS method, the IPC method enables independent control of active power and reactive transferred from one channel to the other. The IPC also allows improved dynamic response in power control and elimination of tedious tuning of control parameters. The effectiveness and performance of the proposed IPC method are compared with those of the PCS method in terms of power control within the APGC in both simulation and experiments.

Hybrid modelling and simulation of thermal systems of in-service power plants for digital twin development

Digital twin is a core technology for smart power plants aiming to increase the safety and efficiency of power generation in low-carbon transitions. High-precision modelling of in-service power plant thermal systems plays a key role to develop digital twins, but remains a challenge. There is a lack of high-precision modelling for in-service power plant thermal systems over the full working ranges. This work proposes a hybrid modelling framework combining physical mechanism and operation data to develop grey-box models of thermal systems. Key equipment characteristics are figured out through historical operation data. Moreover, system models consisting of mass and energy balances, process mechanism equations and characteristic equations are implemented. An in-service 660 MW ultra-supercritical double reheat power plant, one of the most advanced thermal power generation technologies, is selected as a case study. The grey-box model of high- and intermediate-pressure thermal system is established. An average simulation error of the model of 0.79% over the full working ranges is achieved. Furthermore, key system characteristics are quantified through the model. It demonstrates the high precision of the proposed modelling method over the full working ranges and provides necessary model support for the digital twin development of thermal power plants.

Numerical study of convective heat transfer to supercritical CO2 in vertical heated tubes

Supercritical heat transfer is important to design and operate advanced power generation system. Non-uniform heating is frequently encountered such as for sCO2 boiler and solar receiver applications. Here, 3D numerical simulations are performed in turbulent regime, coupling solid wall and sCO2 in tubes. Non-uniform heating is simulated by applying heat via a thin metal layer at the outer tube wall, covering half circumference of tube wall. Calculation results matched experimental data well. Heat transfer is compared between uniform heating and non-uniform heating. Numerical results are re-processed by the pseudo-phase transition theory, including a liquid-like region in tube core and a gas-like layer near the tube wall. The two layers of structure are interfaced by a terminating temperature T+ which is determined by thermodynamics. Hence, supercritical heat transfer is evaluated based on the relative importance of thermal resistances induced by the liquid-like region and the gas-like film region. It is found that wall temperatures for uniform heating are higher than those for non-uniform heating, which is explained by larger thermal resistance of the gas-like film for uniform heating than that for non-uniform heating. This difference ensures better heat transfer for non-uniform heating than uniform heating. We conclude that in turbulent regime, the gas-like film dominates the magnitudes of wall temperature and the occurrence of heat transfer deterioration for both uniform and non-uniform heating. Our work is important for heat transfer facilities in supercritical domain, especially under non-uniform heating condition.

Transportation Electrification Gets a Boost in the Infrastructure Investment and Jobs Act

On November 15, 2021, President Biden signed the $1.2 trillion Infrastructure Investment and Jobs Act (IIJA or “Act”) into law. The IIJA is one of the largest infrastructure packages in recent history, including funding across three key areas: connectivity, decarbonization, and the creation of new economic opportunities. Connectivity investments fund the ways in which Americans connect with one another both physically and virtually. The IIJA intends to fund highways, roads, and bridges, and invest in public transit and water system upgrades, passenger rail, airports, and supply chain ports. It also provides opportunities for increased access to high‐quality broadband connectivity in otherwise underserved areas. While not the intended purpose of the Act, it does nonetheless provide funding that advances decarbonization efforts, including providing financial support for the expansion of renewable energy development, the acceleration of electric vehicle adoption, and the advancement of emerging technologies such as energy storage, blue hydrogen, geothermal, and advanced nuclear power generation. Finally, the IIJA is expected to create significant job growth, with a projected creation of 1.5 million jobs per year for the next 10 years.

Stability Improvement of Onboard HVdc Grid and Engine Using an Advanced Power Generation Center for the More-Electric Aircraft

In the high-power settings of engine, such as maximum take-off, more power should be extracted from the high-pressure spool (HPS) than the low-pressure spool (LPS) to avoid the overspeed and potential instability of the HPS. However, as revealed in this paper, extracting more power from the HPS will degrade the onboard HVDC grid stability for the conventional single dc bus power generation center. To address this conflict, in this paper, an advanced power generation center (APGC) incorporating an extra back-to-back (BTB) converter is introduced to improve the stability for both engine and HVDC grid. The BTB converter connects the HP power generation channel and the LP channel, providing an additional power flow path between the HP channel and LP channel. A transfer function-based impedance model and a state-space model of the HVDC grid are proposed to study the HVDC grid stability. The analytical findings of the HVDC grid stability and stability improvement using the APGC architecture have been verified through simulation and experimental results.

A Multisectoral Dynamic Model for Energy, Economic, and Climate Scenario Analysis

The MIT Economic Projection and Policy Analysis (EPPA) model has been widely used in energy, land use, technology, and climate policy studies. Here, we provide details of revisions that form the basis of EPPA7, the current version. Key updates include: 1) using the latest Global Trade Analysis Project (GTAP-power) database as the core economic data for the world economy; 2) updating regional economic growth projections; 3) separating extant and vintage capital of the previously aggregated fossil generation; 4) using an innovative approach to calculate the costs of backstop (i.e., advanced) power generation options based on engineering data from the Energy Information Administration; 5) identifying base year biofuel output from existing sectors; and 6) re-parameterizing electric vehicles based on recent studies. Our simulations demonstrate that with widespread mitigation policies worldwide, regions relying heavily on fossil fuel imports benefit from lower global fossil fuel prices when their domestic emissions targets are lenient, but the benefits dissipate when deeper emissions cuts are imposed domestically. We also provide an illustration how the model output can be used to calculate the net present values of unrealized fossil fuel production and stranded assets from idling coal power generation under various policy scenarios.

Centralized power generation with carbon capture on decommissioned offshore petroleum platforms

The existing cogeneration systems on offshore petroleum platforms face clashing targets intrinsic to offshore applications, namely, weight, area, cost and efficiency. Moreover, the prolonged offdesign operating conditions during their lifetime further increase the inefficiencies, leading to increased environmental impact. Thus, in this work, centralized power stations are designed for supplying the electricity required by various identical floating production, storage and offloading units (FPSOs) in the offshore oil and gas sector. This approach aims to increase the performance and alleviate the environmental burden that the conventional utility systems are responsible for by integrating carbon abatement technologies. Since these modifications bring about an increase in the initial investment cost and the financial feasibility of the system, a techno-economic assessment and optimization process is necessary in order to determine the optimal configuration of the power hubs. To this end, a combined thermodynamic, environmental and economic analysis, together with space and weight allowance quantification is performed. The use of adapted and decommissioned FPSOs for installing the power hub is a novel proposal that reduces the initial investment cost. As a result, the advanced utility systems provide higher overall power generation efficiencies (above 10 percentage points) compared to existing simple cycle gas turbine systems, even at fourfold lower emissions. The incremental economic analysis has found that, for moderate carbon taxations (> 40 USD/tCO2), the advanced power generation systems may economically outperform the conventional offshore power plants. Lastly, a delay in entry of operation between FPSOs of up to 4 years may reduce the investment cost by 50%, while maintains the same thermodynamic performance.

ADVANCED FOOTSTEP POWER GENERATION USING RFID FOR CHARGING

The advanced Footstep Power Generation using RFID for Charging System is innovated through various past researches. In this paper, historical perspectives used to establish the required system were provided. Due to which, the idea of invention of technologies done related to project.

Bimodal particle distributions with increased thermal conductivity for solid particles as heat transfer media and storage materials

Solid particles are being considered in several high temperature thermal energy storage systems and as heat transfer media in a variety of advanced power generation systems, particularly in concentrated solar power plants. The downside of such an approach is the low overall heat transfer coefficients caused by the inherently low thermal conductivity values of the low-cost solid media when coupled to heat exchanger for the power cycle working fluid. Choosing the right particle size distribution, emittance, and material of the solid media can all make a substantial difference in packed bed thermal conductivity. Current research though exclusively focuses on continuous unimodal distributions of particles. Here, we propose the use of a binary particle system with a bimodal size distribution to significantly increase packed bed thermal conductivity by reducing packed bed porosity. This is the first study related to ceramic solid particle heat transfer that has considered the thermal conductivity of non-unimodal size distributions at room and elevated temperatures. The following study found that for the binary particle system using Carbo particles CP 16/30 – CP 70/140 where the large particle volume fraction was 50% there was an 17–47% increase in packed bed thermal conductivity when compared with a nearly unimodal particle size distribution of CP 16/30 between 50 and 300 °C. Two different porosity and effective thermal conductivity models were studied, with one providing better prediction of porosity but both effective thermal conductivity models providing less predictive capacity. Importantly this approach can have a substantial impact of thermal performance, with little to no impact on the particle cost.

Synthesis of ZnO-CuO and ZnO-Co3O4 Materials with Three-Dimensionally Ordered Macroporous Structure and Its H2S Removal Performance at Low-Temperature

H2S is a common but hazardous impurity in syngas, biogas, or natural gas. For some advanced power generation technologies, such as integrated gasification combined cycle (IGCC), solid oxide fuel cells, H2S content needs to be reduced to an acceptable level. In this work, a series of highly porous Zn-Cu and Zn-Co composites with three-dimensionally ordered macropores (3DOM) structure were synthesized via the colloidal crystal template method and used to remove H2S at 150 °C and one atm. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption studies, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were carried out to analyze the fresh and spent adsorbents. The results show that all the adsorbents possess well-ordered macropores, a large surface area, and a highly dispersed active phase. The relative content of Zn and (Cu or Co) has a significant influence on the desulfurization performance of adsorbents. The addition of CuO significantly increases the sulfur capacity and 3DOM-Zn0.5Cu0.5 shows the largest sulfur capacity of all the adsorbents, reaching up to 102.5 mg/g. The multiple adsorption/regeneration cycles of 3DOM-Zn0.5Cu0.5 and 3DOM-Zn0.5Co0.5 indicate that the as-prepared adsorbents are stable, and the sulfur capacity can still exceed 65% of the fresh adsorbents after six cycles.

Performance improvement of supercritical carbon dioxide power cycle at elevated heat sink temperatures

The supercritical carbon dioxide power cycle has emerged as an advanced power generation system owing to its better efficiency, compactness, and capability to synergize with a broad range of boundary conditions. Its superior performance is due to the liquid-like compression near the critical point. However, this phenomenon deteriorates significantly for elevated heat sink temperatures and is therefore highly detrimental to the cycle performance. Thus, this study proposed and investigated an integrated power and refrigeration cycle scheme to curtail the effects of elevated heat sink temperatures. A theoretical model of the proposed scheme based on industrial flue gases was developed, and the influence of heat sink at a range of heat-source temperatures (200–500 °C) was examined. Subsequently, benchmark cases are established and optimized, and the performance improvement with respect to the benchmark case is reported, with net power as the performance indicator. The optimization of the benchmark case reveals that the simultaneous optimization of low- and high-pressure levels of the cycle is necessary to maximize the net power. The parametric investigation of the proposed configuration shows that the performance is sensitive to the saturation temperature in the evaporator of the refrigeration cycle and to the ratio of low- and high-pressure levels in the power cycle. Therefore, the proposed case was optimized for both influencing parameters for each boundary condition. The results show that for a given heat-source temperature, higher heat sink temperatures favor the proposed design. For the heat-source temperatures of 200 °C, the benchmark case is superior for all heat sink conditions, whereas for 300 °C, 400 °C, and 500 °C, the proposed system results in an increase in power generation of 10.67%, 7.2%, and 5.2%, respectively, at a sink temperature of 50 °C. Finally, a case study with molten salt as the heat source was conducted, and the results indicated that the proposed scheme outperformed the benchmark case by 32.87% in terms of net power. The results are significant in simplifying the design of pressurization components and performance improvement of the supercritical carbon dioxide power cycle at elevated heat sink temperatures.

Optimal design of power hubs for offshore petroleum platforms

Even though advanced power generation systems offer higher efficiencies than simpler gas turbines, severe area and weight restrictions keep on impeding their widespread implementation in offshore petroleum industry. If those restrictions could be resolved, the performance of the utilities systems on offshore platforms may be drastically enhanced. In order to overcome these practical limitations, the installation of a power hub is proposed to centralize the energy supply required by a number of floating production, storage and offloading units (FPSOs). However, many challenges are still brought to companies contemplating this approach, such as incremental costs and prolonged offdesign operating conditions. This circumstance renders necessary to determine the optimal number, layout and operating load of the modular power units on the hub. Thus, in this work, a computational framework is developed to assist in the selection of the most suitable hub setups, so that the trade-off between higher overall efficiency and lower investment cost can be elucidated. This framework consists of a group of subroutines that evaluates, compares and ranks alternative offshore utility systems in terms of well-defined objective functions, whereas is subject to restricted weight and space allowances. As a result, the power hub configurations based on the largest bottoming cycles benefit from the economies of scale, as well as from an increased efficiency, if compared to other designs based on smaller bottoming cycles. Levelized costs of electricity reaches 40 USD/MWh when only gas turbines are installed, which can be reduced by 13% if combined cycles are preferred. The weight-to-power ratio of the hubs based on combined cycles remains 12–28% higher than that of the conventional setup, whereas the efficiency increase achieves up to 7 percentage points.

System modification and thermal efficiency study on the semi-closed cycle of supercritical carbon dioxide

Supercritical carbon dioxide (sCO2) semi-closed cycle is an advanced, efficient, and economical power generation system that can meet the needs of low cost and efficient utilization of coal and low carbon emissions. The Advanced System for Process Engineering software (Aspen Plus) was used to simulate different sCO2 systems. In the simplified sCO2 closed cycle, multi-stage compression and inter-cooling of CO2 compressors together can increase the system efficiency by about 5%. The system thermal efficiency increases by 0.5% with every 10 bar increase of the combustion chamber pressure between 200 bar and 500 bar, and increases by 0.35% with every 10 °C increase of the combustion temperature between 800 °C and 1500 °C. In the typical sCO2 semi-closed cycle--Allam cycle, the gas temperature in the combustion chamber decreases with the increase of CO2 backflow, and it would decrease with increase of the excess O2 ratio. The system thermal efficiency could be improved by 3% by adding reheat and graded expansion, and by 2% with ASU coupling and CO2/O2 mixing. Adding heat exchangers and proper stream distribution can improve the system efficiency by up to 10%. When the combustion chamber temperature is 1300 °C, turbine inlet pressure is 300 bar, turbine outlet pressure is 30 bar, and the split ratio of CO2 is 5:95, the sCO2 semi-closed cycle with precompression, recompression or partial cooling reaches the highest thermal efficiency (~64%). Depending on the results of the system modification and sensitivity analysis, ideas can be provided for the improvement and demonstration of the system.

Performance of hot-gas cleanup technology for clean coal processing

The integration of advanced coal-based power generation systems with hot-gas cleanup technology endows the former with higher efficiency and reduces their environmental impacts. Syngas from coal gasification or flue gas from combustion contains dust particulates that must be eliminated before the raw gas is burned in gas turbines to protect the turbine blade and control particulate emissions. The present work attempts to provide a general understanding of moving granular bed filters (MGBFs), which are regarded as a promising technology for hot-gas cleanup, and proposes a filtration technology for application to near-industrial environments. An experimental method was established to investigate the filtration processing of dust particulates under various operating conditions. The experimental facility included an air fan, two-stage gas heaters, a screw feeder for dust particulates, a measurement system to detect the size distribution of dust particulates, a filter granule supply device, a rotary valve, and an MGBF filled with filter granules. The collection efficiency of the MGBF was assessed at different temperatures ranging from room temperature to 500 °C and granular mass flow rates of 300–1500 g/min under a fixed filtration superficial velocity of 2100 cm/min and dust concentration 7500 ppmw. Variations in the outlet concentration and size distribution of dust particulates were measured to evaluate the dynamic characteristics of the cleanup process. Results revealed that an optimal mass flow rate must exist for high collection efficiency under specific operating temperatures. In addition, important design constraints were identified for the successful operation of the proposed MGBF system. The findings indicated that the proposed design could be useful in different cross-flow filter systems for gas cleanup. This work lays a solid foundation for future research on clean coal processing.

Quantification of the water-energy-carbon nexus of the coal fired powerplant in water stressed area of Pakistan

ABSTRACT The water-energy-carbon realms are interlinked together in all of the sectors and should be subjected to integrated management. In this study, Water-Energy-Carbon Nexus (WECN) of a 660 MW coal-fired powerplant, a part of China-Pakistan Economic Corridor (CPEC) is analyzed to calculate its water and carbon footprints. The power generation unit works on subcritical technology which is considered as the least efficient type. Therefore, more efficient power generation technologies are also studied to assess their effect on the WECN. Moreover, the use of coal for power generation will be responsible for substantial amounts of CO2 emissions and will add to the country’s overall greenhouse gas emissions. To counter this, carbon capture and storage technology could be employed for the powerplant; therefore, this study also analyzes the carbon capture technology and its impact on the WECN of the powerplant. For nexus modeling two of the most widely used tools namely, Water Evaluation and Planning (WEAP), and Long-Range Energy Alternatives and Planning (LEAP) have been selected to model the water and energy systems, respectively. Findings show that, the unit has yearly water demand of 11.06 Mm3 with electricity requirements of 36.36 million kWh and the resulting CO2 emissions can reach as high as 5.76 million metric tons by 2050. Advanced power-generation technologies can save water, the resulting electricity demand while also reducing CO2 emissions of the plant. The water saved by the use of advanced technologies could be used by the hundreds of people residing in an already water-stressed area.

Performance assessment of a biomass fuelled advanced hybrid power generation system

This paper deals with the development and detailed assessment of a biomass-fuelled electrochemical power generation system employing biomass gasification, solid oxide fuel cell, gas turbine, and organic Rankine cycle. The performance of the plant has been monitored with the changes in important operating parameters with respect to energetic, exergetic, economic and environmental points of view. The proposed system yields the maximum 49.29% 1st law efficiency and 44.57% 2nd law efficiency. Exergetic analysis reveals that among all the elements of the system, biomass gasifier is the highest (41.22%) contributor in total exergy destruction, followed by the heat exchanger (14.01%), and the organic Rankine boiler (13.27%). Economic analysis reveals that the plant can generate electricity at a minimum rate of 0.0654 $/kWh. The environmental analysis predicts that the proposed system has a maximum CO 2 emission reduction potential of about 2867 tCO 2 /year compared to a coal-fired sub-critical steam power plant of similar capacity, resulting in an environmental benefit value of about 430014 $/year. This study also reveals that the present system is better compared to previously investigated other biomass-fuelled power generation plants considering the efficiency and economy together. • Biomass-based SOFC-GT-ORC system has been conceptualized. • Energetic, exergetic, economic and environmental analyses have been performed. • The system has highest energetic and exergetic efficiencies of 49.29% and 44.57%. • Minimum cost of electricity can reach up to 0.0654 $/kWh. • The system has better thermo-economic results than other biomass-based power plants.

Off-Design Performance Prediction of a S-CO2 Turbine Based on Field Reconstruction Using Deep-Learning Approach

The reliable design of the supercritical carbon dioxide (S-CO2) turbine is the core of the advanced S-CO2 power generation technology. However, the traditional computational fluid dynamics (CFD) method is usually applied in the S-CO2 turbine design-optimization, which is a high computational cost, high memory requirement, and long time-consuming solver. In this research, a flexible end-to-end deep learning approach is presented for the off-design performance prediction of the S-CO2 turbine based on physical fields reconstruction. Our approach consists of three steps: firstly, an optimal design of a 60,000 rpm S-CO2 turbine is established. Secondly, five design variables for off-design analysis are selected to reconstruct the temperature and pressure fields on the blade surface through a deconvolutional neural network. Finally, the power and efficiency of the turbine is predicted by a convolutional neural network according to reconstruction fields. The results show that the prediction approach not only outperforms five classical machine learning models but also focused on the physical mechanism of turbine design. In addition, once the deep model is well-trained, the calculation with graphics processing unit (GPU)-accelerated can quickly predict the physical fields and performance. This prediction approach requires less human intervention and has the advantages of being universal, flexible, and easy to implement.

Design and Performance Analysis of a Supercritical Carbon Dioxide Heat Exchanger

This paper presents a preliminary design and performance analysis of a supercritical CO2 (SCO2) heat exchanger for an SCO2 power generation system. The purpose of designing a SCO2 heat exchanger is to provide a high-temperature and high-pressure heat exchange core technology for advanced SCO2 power generation systems. The target outlet temperature and pressure for the SCO2 heat exchanger were 600 °C and 200 bar, respectively. A tubular type with a staggered tube bundle was selected as the SCO2 heat exchanger, and liquefied petroleum gas (LPG) and air were selected as heat sources. The design of the heat exchanger was based on the material selection and available tube specification. Preliminary performance evaluation of the SCO2 heat exchanger was conducted using an in-house code, and three-dimensional flow and thermal stress analysis were performed to verify the tube’s integrity. The simulation results showed that the tubular type heat exchanger can endure high-temperature and high-pressure conditions under an SCO2 environment.

Electromagnetic Characteristics Analysis of a Tubular Moving Magnet Linear Generator System

As a new type of advanced electrical power generation system, free-piston engines can be applied to many fields, such as electric vehicles and communication base stations. In this paper, a novel tubular moving magnet linear generator system is designed for free-piston engines. A three-dimensional finite element model of the designed linear generator is presented using a transient computing method with a motion solver. The electromagnetic force, electromotive force, and generating efficiency of the designed linear generator are analyzed in detail. A prototype is manufactured and tested under laboratory conditions, and then the main performance of the prototype is evaluated using the validated finite element model. The electromagnetic analysis in this paper indicates that a generating efficiency of 91.4% can be obtained by the moving magnet linear generator under the rated working frequency of 50 Hz. Compared with the existing moving coil linear generator prototype, the power volume density and the power mass density of the new designed moving magnet linear generator prototype are increased by 150% and 35%.

Comparative assessment of advanced power generation and carbon sequestration plants on offshore petroleum platforms

On conventional offshore petroleum platforms, the combined heat and power production (CHP) currently depends on simple cycle gas turbine systems (SCGT) that operate at lower efficiency and increased environmental impact compared to modern onshore thermoelectric plants. Additionally, the reduced space and the limited weight budget on offshore platforms have discouraged operators from integrating more efficient, but also bulkier cogeneration cycles (e.g. combined cycles). In spite of these circumstances, more stringent environmental regulations of offshore oil and gas activities have progressively led to a renewed interest in the integration of advanced cogeneration systems, together with either customary or unconventional carbon capture approaches, to maintain both higher power generation efficiencies and reduced CO2 emissions. Thus, in this paper, it is evidenced how advanced gas turbine concepts are promising technologies for maintaining or even increasing efficiency, while facilitating the capture rate of CO2 produced, either for geological storage or enhanced oil recovery. Despite the profuse research works on onshore applications, advanced cogeneration and carbon capture systems have been barely studied in the context of supplying power to offshore petroleum platforms. Accordingly, the performance of a conventional offshore petroleum production platform (without carbon capture system) is compared to other configurations, based on either an amine-based chemical absorption system or oxyfuel combustion concepts ( S-Graz and Allam cycles) for CO2 capture purposes. Since the original power and heat requirements of the processing platform must remain satisfied, an energy integration analysis is performed to determine the waste heat recovery opportunities. Additionally, the exergy method helps quantifying the most critical components that lead to the largest irreversibility and identifying the thermodynamic potential for enhanced cogeneration plants. As a result, oxyfuel equipped platforms provide a diversified set of advantages, while keeping competitive efficiencies. For instance, advanced systems allow for cutting down ostensibly the atmospheric CO2 emissions compared to the conventional and amine-based power plant configurations of the FPSO.