High Efficiency Power Plant Research Articles

Production of biobased polyethylene terephthalate and its precursors for diversification in the global sugarcane industry

The technical and economic viability of producing fully bio-based polyethylene terephthalate (PET) or its monomers was investigated. First generation (1 G) biorefineries, utilizing A-molasses, and combined first and second generation (1G2G) biorefineries, utilizing molasses and sugarcane bagasse and brown leaves, were considered. Simulations were developed for self-sufficient biorefineries, where the energy demands were met by utilizing the existing sugar mill boiler, accompanied by a new medium-pressure boiler and biogas generator. 1G2G scenarios required the replacement of the sugar mill boiler with a new, high-efficiency combined heat and power (CHP) plant, where electricity and useful heat were generated from a portion of 2 G biomass and other residues. 1 G PET was unprofitable at a minimum selling price (MSP) of $2946.t−1. 1 G production of Ethylene ($1847.t−1), monoethylene glycol (MEG) ($1648.t−1), 5-Hydroxymethylfurfural (HMF) ($1576.t−1) and iso-butanol (iButOH) ($1292.t−1) were more economically viable than PET, terephthalic acid (TPA) ($2689.t−1) and p-xylene (PX) ($2983.t−1), due to less complex processing and lower energy demands. 1G2G biorefineries were less profitable than 1 G equivalents, due to the cost of pretreatment and new CHP plants. The most profitable scenario was 1 G iButOH, with an MSP 19.0 % lower than its market price. New technologies to produce p-xylene and TPA from biomass in fewer steps, such as Virent Inc.’s Bioforming® technology, could potentially improve the economic viability of PET in the future.

Techno-economic analysis of ammonia cracking for large scale power generation

The increasing interest in leveraging green ammonia to mitigate carbon emissions in fertilizer production is paralleled by an expanding acknowledgment of its potential as a fuel for decarbonizing the electricity sector, particularly in high-efficiency gas turbine power plants. Co-firing ammonia with hydrogen presents a promising method for integrating ammonia into existing infrastructures. Within this context, the development of efficient technology for ammonia cracking presents a potential avenue for deploying ammonia in gas turbines. The objective of this study is to conduct a preliminary techno-economic evaluation and uncertainty analysis of two cracking technologies namely a membrane reactor and a conventional FTR (Fired Tubular Reactor) for the co-firing of ammonia with hydrogen in a CCGT (Combined Cycle Gas Turbine) plant. The integration of a membrane reactor during the cracking stage demonstrates a remarkable improvement in the system's thermal efficiency, surpassing traditional approaches by over 25%. Additionally, it brings about an approximate 10% reduction in the levelized cost of hydrogen (LCOH), despite a higher initial capital expenditure (CAPEX). At the CCGT level, the discrepancy in levelized cost of electricity (LCOE) narrows, as it is strongly influenced by the cost of ammonia constituting 80% of the LCOE. Beyond LCOE, the widespread adoption of these systems also faces challenges due to material scarcity. Analysis reveals that revamping just 1 GWe of CCGT assets using membrane reactors would for example necessitate approximately 0.11% of the global palladium supply, and 10% of the global ruthenium production. Considering the limited availability of these resources, coupled with their high demand across multiple sectors and the possibility of external factors such as geopolitical tensions, this strategy seems unfeasible. To tap into this market, future research should prioritize the exploration of alternative membrane materials, such as carbon molecular sieves, and catalysts, like nickel.

Optimal placement and sizing of photovoltaic power plants in power grid considering multi-objective optimization using evolutionary algorithms

During the past decade, the effect of renewable and non-renewable Distributed Generation (DG) sources of production has grown all over the world. Also, it has enhanced by national and international policies aimed at increasing the share of renewable energy sources and combining small high efficient heat and power plants to reduce greenhouse gas emissions, and global warming have been encouraged. Although the installation and operation of DGs have discussed for solving network problems in distribution networks, the fact is that in most cases, Distribution System Operator has no control or influence over DG placement and size. In this article, a meta-heuristic algorithm for management and decision-making for optimal selection is presented, and in choosing the optimal solution, the impact factor is suggested in the best case. Inappropriate DG placement may increase system losses, network investment, and operating costs. This paper determined the optimal capacity and placement of photovoltaic sources to reduce losses, improve the voltage profile, and increase the active power to reactive power lines in MATLAB software by the second version of the genetically engineered algorithm with unstable Non-dominated Sorting Genetic Algorithm (NSGA-II).

Influence of precipitate and grain sizes on the brittle-to-ductile transition in Fe–Al–V bcc-L21 ferritic superalloys

The limiting factors to achieving a wide application of bcc-superalloys are the high brittle-to-ductile transition temperatures (BDTT). The understanding of the mechanisms controlling the BDTT and how to optimise the microstructure in polycrystalline bcc-superalloys remains a concern today.In the present work, the influence of grain and coherent precipitates sizes on strength and brittle-to-ductile transition temperature (BDTT) are studied in a Fe78Al10V12 (A2+L21) ferritic superalloy, toward application in high-efficiency power plants. Additionally, the A2 matrix behaviour was evaluated in a derived single-phase-bcc Fe84Al8V8 alloy. Thermal ageing and coarsening treatments were applied to produce samples with different precipitate and grain sizes. Tensile tests were carried out at different temperatures and strain rates to assess the variation of the yield stress. Charpy impact tests were used to measure the BDTT in both alloys, which was substantially reduced with grain size refinement, and precipitate coarsening. It was found that the increase in cleavage stress by precipitation strengthening follows the same behaviour that the increase in yield stress for coherent strengthened bcc-superalloys. Integration into a physical-based model, which identified a novel interplay with cleavage stress, provides enhanced BDTT predictive capability for ferritic superalloys.

Compact High Efficiency and Zero-Emission Gas-Fired Power Plant with Oxy-Combustion and Carbon Capture

Reduction of greenhouse gases emissions is a key challenge for the power generation industry, requiring the implementation of new designs and methods of electricity generation. This article presents a design solution for a novel thermodynamic cycle with two new devices—namely, a wet combustion chamber and a spray-ejector condenser. In the proposed cycle, high temperature occurs in the combustion chamber because of fuel combustion by pure oxygen. As a consequence of the chemical reaction and open water cooling, a mixture of H2O and CO2 is produced. The resulting working medium expands in one turbine that combines the advantages of gas turbines (high turbine inlet temperatures) and steam turbines (full expansion to vacuum). Moreover, the main purpose of the spray-ejector condenser is the simultaneous condensation of water vapour and compression of CO2 from condensing pressure to about 1 bar. The efficiency of the proposed cycle has been estimated at 37.78%. COM-GAS software has been used for computational flow mechanics simulations. The calculation considers the drop in efficiency due to air separation unit, carbon capture, and spray-ejector condenser processes. The advantage of the proposed cycle is its compactness that can be achieved by replacing the largest equipment in the steam unit. The authors make reference to a steam generator, a conventional steam condenser, and the steam-gas turbine. Instead of classical heat exchanger equipment, the authors propose non-standard devices, such as a wet combustion chamber and spray-ejector condenser.

Effects of coal compositions on the environment and economic feasibility of coal generation technologies

Coal has strategic importance for the global generation of electricity. However, the environmental impacts of its intense use are a concern, especially about greenhouse gases emissions. High Efficiency and Low Emissions coal-fired power plants are part of the approach known as Clean Coal Technologies, including supercritical (SC) and ultra-supercritical (USC) plants, since they allow cleaner and more efficient coal usage. This study analyzes how the usage of different coal compositions impacts the economic and environmental feasibility of operating units with higher efficiency when compared to conventional subcritical power plants. The analysis identified that the application of supercritical and ultra-supercritical technologies provided significant savings in fuel consumption, and consequently in CO2 emissions. The economic feasibility analysis identified that the annual savings change significantly among the analyzed coal compositions, in such manner that it determines whether the supercritical and ultra-supercritical technological alternatives can be economically viable in the long term or not. In general, these technologies are viable both as an alternative to mitigate CO2 emissions and to obtain better profitability through energy generation.

Chromium can cluster in molten salts

Highly dilute metal ions can aggregate in a high-temperature ionic-liquid medium and form long-lived clusters. The unexpected finding, which is the result of a study that combines experiment and modeling, sheds light on the early stages of corrosion in molten salt reactors (MSRs). MSRs are a next-generation, high-efficiency nuclear power plant technology in which nuclear fuel contained in a high-temperature salt circulates through the reactor in the liquid state. By running roughly 500 °C higher than today’s solid-fuel commercial reactors, MSRs promise to boost thermodynamic efficiency. More than 50 years after researchers began studying MSRs, however, the technology remains under development. One reason is that molten salts can corrode reactor vessels, slowly leaching chromium from alloys that otherwise perform well. To probe the corrosion process at the atomic level, Alexander S. Ivanov of Oak Ridge National Laboratory and coworkers used X-ray scattering and theoretical simulations to study the behavior of

Modular Multilevel Converter for Photovoltaic Application with High Energy Yield under Uneven Irradiance

The direct integration of Photovoltaic (PV) to the three-phase Modular Multilevel Converter (MMC) without dc–dc converters results in high-efficiency PV power plant with increased energy yield. The arm power control method for the MMC further improves the extraction of available power under uneven irradiance across different phases of the MMC. However, the uneven irradiance between the sub-modules results in residual voltage that results in harmonics and unbalance components. In this paper, the effect of uneven irradiance across the sub-module of the MMC is investigated with arm power control method. A modified balancing algorithm for the arm power control of the MMC is proposed which enables balanced power to be injected into ac grid despite uneven irradiance across the sub-modules in the MMC. The modified balancing algorithm enables to keep the unbalance in the phase currents below 10% and the Total Harmonic Distortion (THD) is confined as per IEEE 519 standard.

The problems of intelligence improving of power plants process control system

Trends in the development of modern control systems of technological processes (ACS TP) on the basis of program and technical complexes (PTC) are aimed at creating a unified control system of the power unit in all modes of its operation, capable in addition to directly controlling the power unit, blocking operator errors, using intelligent control strategies. At the same time, improving the quality of technological processes based on new hardware and software and the achievements of the modern theory of automatic control occurs mainly at the level of power unit equipment and to a much lesser extent – at the level of the power plant. It is obvious that the level of intelligence of ACS TP should correspond to the technical level of promising high-efficiency power plants. Under these conditions, the problem of increasing the degree of intelligence of energy production management systems in power plants through the development and implementation of new innovative technologies, algorithms and systems for optimal control of the operation of equipment of power plants and power plants in general is extremely urgent. At the same time, a set of technical solutions and technologies should provide, in addition to high efficiency, such “sparing” modes of operation, which allow to reduce the rate of exhaustion of the resource characteristics of the equipment and thereby prolong its service life. This shows the necessity and expediency of developing intelligent high-performance control systems for the entire cycle of energy production in power plants, by expanding the functionality of the PTC in terms of optimal control of technological and production processes of the block and station levels.

Thermodynamic Cycle Concepts for High-Efficiency Power Plants. Part B: Prosumer and Distributed Power Industry

An analysis was carried out for different thermodynamic cycles of power plants with air turbines. A new modification of a gas turbine cycle with the combustion chamber at the turbine outlet has been described in the paper. A special air by-pass system of the combustor was applied, and in this way, the efficiency of the turbine cycle was increased by a few points. The proposed cycle equipped with an effective heat exchanger could have an efficiency higher than a classical gas turbine cycle with a regenerator. Appropriate cycle and turbine calculations were performed for micro power plants with turbine output in the range of 10–50 kW. The best arrangements achieved very high values of overall cycle efficiency, 35%–39%. Such turbines could also work in cogeneration and trigeneration arrangements, using various fuels such as liquids, gaseous fuels, wastes, coal, or biogas. Innovative technology in connection with ecology and the failure-free operation of the power plant strongly suggests the application of such devices at relatively small generating units (e.g., “prosumers” such as home farms and individual enterprises), assuring their independence from the main energy providers. Such solutions are in agreement with the politics of sustainable development.

Techno-Economic Assessment of Novel vs. Standard 5m Piperazine CCS Absorption Processes for Conventional and High-efficiency NGCC Power Plants

CO2 capture and storage (CCS) can play a key role in the mitigation of greenhouse gas emissions, as it is generally applicable to many industrial sectors to limit the environmental impacts from fossil fuels usage. In this regard, natural gas-fired power plants are a suitable application for CCS technologies, although they produce flue gases with a much lower CO2 concentration (i.e. ~4 %mol) than coal-fired power plant flue gases. Amine-based solvent absorption has been widely studied as a practical solution to decarbonize post-combustion flue gases from natural gas combined cycle power plants (NGCC). This paper presents the methodology and the results of a techno-economic assessment of 5 molal (5m) piperazine (PZ) as a new potential baseline solvent for carbon capture from NGCC in three different case studies that have been considered relevant from a preliminary literature analysis. The three evaluated configurations are (i) conventional F-class NGCC coupled with the conventional absorber configuration with a direct contact cooler (DCC), (ii) conventional F-class NGCC coupled with an advanced absorber configuration (no DCC – flue gas cooling integrated within the absorber) and (iii) high efficiency, state-of-the-art H-class NGCC, coupled with the advanced absorber configuration. The present work is based on the most recent findings from University of Texas at Austin (UT) research activities, and it has been carried out by Laboratorio Energia e Ambiente Piacenza (LEAP) and Politecnico di Milano (POLIMI) researchers supported and sponsored by the CO2 Capture Project (CCP).

On effect of rhenium on mechanical properties of a high-Cr creep-resistant steel

9–12%Cr martensitic steels are perspective materials for critical components of new high-efficiency power plants working at ultra-supercritical parameters of steam. Addition of 0.2% rhenium in the experimental steel improved the short-term creep strength at 650 °C. Comparison of kinetics of tungsten depletion from the matrix in different high-Cr martensitic steels showed that rhenium in the experimental 10Cr-3Co-3W-0.2Re steel did not lead to retaining an increased amount of solute W in the ferritic matrix during both aging and creep at 650 °C. At the same time, the precipitation of the high fraction of the fine Laves phase particles provided the effective particle strengthening.

A novel multigeneration system driven by a hybrid biogas-geothermal heat source, Part I: Thermodynamic modeling

Hybrid renewable energy heat sources provide more sustainable energy resources with high maintenance for high-efficient power plants. Multigeneration systems driven by a hybrid renewable source are proved as cutting-edge technologies in recent studies. In this study, a novel multigeneration system driven by a hybrid biogas-geothermal heat source is proposed and simulated. To demonstrate the feasibility of the proposed multigeneration system, first and second laws analysis are employed as the most effective tools for performance assessment of the systems. It is found that the proposed multigeneration system can produce overall heating capacity, overall cooling capacity, net output power, hydrogen production rate, and freshwater production rate of 538.1 kW, 1799 kW, 443.4 kW, 0.2583 kg/s, and 367.92 lit/h, respectively. Under this circumstance, the thermal efficiency, exergy efficiency, and total exergy destruction of the system are calculated 62.28%, 74.9%, and 2036.19 kW, respectively, showing a considerable improvement compared to the single-generation system. In addition, the results indicated that the condenser is the most destructive component, whereas the absorption refrigeration cycle is accounted as the most destructive sub-system. Moreover, a comprehensive parametric study is carried out to give more information about the behavior of the proposed system.

High-efficiency concentrated solar power plants need appropriate materials for high-temperature heat capture, conveying and storage

Particle suspensions can be used in Solar Power Towers to capture the solar heat at a high temperature, and convey it to the storage and the subsequent use in the power block. Thermal Energy Storage (TES) needs to be integrated. Temperatures of 600–900 °C foster the use of high-efficiency power generation cycles. Appropriate Phase Change Materials (PCMs) in that temperature range were examined, i.e. Sb2O3 for the lower melting point range, and BaCO3 and its Na2CO3 compounds as high melting PCMs. Cooling rates of the melt and solid phases follow a linear-time relationship. The time for solidification of the melt is also measured. Rates and times are compared with the theoretical approaches of unsteady state conduction and phase transition. The cooling rate of the melt is significantly higher than the cooling rate of the solid phase. The time of phase transition is a function of the latent heat. Natural convection within the melt enhances the heat transfer, and is predicted by assigning an effective thermal conductivity to the melt. The thermal cycling of the encapsulated PCMs demonstrates that the selected encapsulation material retains its mechanical properties for 1250 charge/discharge cycles. Practical considerations on TES design conclude the research.

Large-Scale 3D Electromagnetic Field Analysis for Estimation of Stator End Region Loss in Turbine Generators

In indirectly hydrogen cooled turbine generators used in high-efficiency combined cycle power plants, improving the energy efficiency and increasing the power density are required for one of the solutions of the global environmental problems. When the output current is increased for achieving the high power density, the stray load loss at the stator end region is increased by the leakage flux from the armature and field coils. Therefore, in the case that the stray load loss at the stator end region is increased when the output capacity is increased, it is necessary to evaluate the temperature under the condition of the leading power factor load. In this paper, we analyzed the loss density distribution at the end region structures using the large-scale 3D electromagnetic field analysis to establish the temperature reliability in the 870MVA indirectly hydrogen cooled machine, which is the largest class capacity in the world. Using the loss density distribution obtained by the analysis, the thermal analysis is then performed. The analysis results show good agreements with the measured values.

고효율 저공해 청정화력 발전동향

고효율 저공해 청정화력 발전동향

固体酸化物形燃料電池（ＳＯＦＣ）に適したバイオマスガス化炉の開発と解析

In order to utilize the unused biomass spread in broad area, a high efficient and compact biomass power plant is demanded. In this study, the design and control methods of the biomass downdraft gasifier for solid oxide fuel cells (SOFCs) were investigated. Using the calculation model of biomass gasifier, the experimental data and calculated data were compared. The validity of the model was confirmed, it was possible to predict the composition of the gasified gases with the parameters (Temperature, Supply of biomass, Air, Steam and Compositions of biomass). Furthermore, from the I-V characteristics of the SOFC fed by the gasified gases, it was confirmed that the power output by the gasified gas was about 0.85 times as large as that by pure hydrogen.

Thermodynamic analysis of a novel power plant with LNG (liquefied natural gas) cold exergy exploitation and CO2 capture

The LNG (liquefied natural gas) regasification process is a source of cold exergy that is suitable to be recovered to improve the efficiency of thermal power plants. In this paper, an innovative power plant with LNG (liquefied natural gas) exergy utilisation and the capture of CO2 proceeding from the flue gases is presented. It is characterised by the recovery of LNG cold exergy in a closed Brayton cycle and through direct expansion in an expander coupled to an electrical generator. Moreover, this novel power plant configuration allows CO2 capture, through an oxy-fuel combustion system and a Rankine cycle that operates with the flue gases themselves and in quasi-critical conditions. The greatest advantage of this plant is that all the recoverable LNG exergy is used to increase the efficiency of the CBC (closed Brayton cycle) and in direct expansion whereas, in other power cycles found in literature that associate LNG regasification and CO2 capture, part of the LNG exergy is used for condensing flue gas CO2 for its subsequent capture. As a result, a high efficiency power plant is achieved, exceeding 65%, with almost zero greenhouse gas emissions.

Thermodynamic Performance of a High Efficient Power Plant Based on Faecal Biomass Gasification, Solid Oxide Fuel Cells and Micro Steam Turbine

Affordable sanitation around the world with the recovery of valuable energy and clean water from faecal biomass in an off-grid system is a challenge. An energy neutral sanitation system concept based on plasma gasification and solid oxide fuel cell (SOFC) was presented by TU Delft {Mings et al.}. The system is further optimised and novel small scale CHP toilet system concept has been developed which can generate power very efficiently and produce clean water. Pre-dryed faecal biomass, is fed to the integrated system. The system combines a dryer, a plasma gasifier, and a gas cleaning unit with an ambient pressure stack and a micro steam turbine (MST). The gasifier uses the heat supplied from the combustion of SOFC depleted fuel. With this concept syngas with high heating value can be produced, which can be efficiently converted in a SOFC system. This is reflected by the net electrical efficiency of the integrated system configuration of the order of 50%. Additional power is produced combining it with an MST and an efficiency increase of the order of 5% is achieved. Variation of the different operating conditions in the system reveals an optimum for the temperature, steam to biomass ratio and oxidant to fuel ratio in the gasifier. Furthermore, the SOFC operating temperature influences the system performance and self-sustainability. As a result, from a thermodynamic point of view it is demonstrated that a high efficiency power generation through faecal biomass can be realized. Ming Liu, T. Woudstra, E.J.O. Promes, S.Y.G. Restrepo, P.V. Aravind. System development and self-sustainability analysis for upgrading human waste to power.

Thermodynamic Performance of a High Efficient Power Plant Based on Faecal Biomass Gasification, Solid Oxide Fuel Cells and Micro Steam Turbine

Affordable sanitation around the world with the recovery of valuable energy and clean water from faecal biomass in an off-grid system is a challenge. A novel small scale combined heat and power (CHP) toilet system concept has been optimized which generate power very efficiently and produce clean water. The system combines a dryer, a plasma gasifier, and a gas cleaning unit with an ambient pressure solid oxide fuel cell (SOFC) stack and a micro steam turbine (MST). The gasifier uses additional heat supplied from the combustion of stack depleted fuel. With this concept, syngas with high heating value can be produced which can be efficiently converted in a SOFC system. This is reflected by the net electrical efficiency of the integrated system configuration of the order of 40%. Additional power is produced combining it with an MST and an efficiency increase of the order of 20% is achieved.