Cycle Gas Research Articles

Air Excess Coefficient and Irreversibility Value Analysis of Gas Turbines

Gas turbines used in natural gas cycle power plants have been researched in terms of energy efficiency. Gas turbines used in power generation plants have a very complex structure because they contain many components. In order to determine the thermodynamic performance of this system, the efficiency of each component and the increase in entropy of each component were calculated using exergy analysis. Irreversibility was chosen as the main parameter and used for thermodynamic optimization of production. The system consists of many components. An increase in the irreversibility of a single component causes an increase in the irreversibility of other components. The effect of gas turbine pressure ratio and excess air percentage on fuel consumption, fuel exergy, combustion chamber exergy change and irreversibility change was investigated. It was observed that the increase in compressor pressure ratio increased irreversibility. Maximum irreversibility was observed in the combustion chamber. Irreversibility was compared with the excess air used in the combustion chamber. The air excess coefficient was examined as percentages of 100%, 200%, and 300%, respectively. The compression pressure ratio was examined for air excess coefficient percentage values from 3 to 40.

Optimizing trigeneration energy systems: Biogas-centric methanol production via direct CO2 hydrogenation with advanced integration of PEM electrolyzer and LNG cold technology

Biogas, a sustainable alternative to fossil fuels, addresses issues of non-renewability and accessibility. Its structural similarity to fossil fuels makes it a potent option for energy systems. With this in mind, this paper discusses a novel trigeneration system that utilizes biogas and Liquefied natural gas cooling to produce methanol, electricity, cold water, hot water, oxygen, and natural gas. The system integrates various components such as a biogas burner, Kalina cycle, organic Rankine cycle, liquefied natural gas liquid gasification cycle, proton exchange membrane electrolyzer, and methanol synthesis unit. Simulation via Aspen HYSYS software includes an analysis of energy, exergy, economic, and environmental aspects. Efficiency assessment in single generation, cogeneration, trigeneration, and chemical trigeneration modes concludes chemical trigeneration as most efficient, with the proton exchange membrane electrolyzer being the most efficient subsystem. Key variables like Kalina cycle evaporator temperature, gas flow rate to the methanol reactor, and organic Rankine cycle working fluid pressure are assessed. Predictions on thermodynamic, environmental, and economic behaviors, along with their fluctuations, are made. Using a thermoeconomic approach, the economic analysis determines an exergy unit cost of 59.79 $/GJ and a total cost rate of 2764 $/h. Overall, this work presents a novel and efficient chemical trigeneration system that utilizes biogas and LNG cooling to produce multiple products.

Thermodynamic evaluation of decarbonized power production based on solar energy integration

This study aims to create an environmentally friendly system by utilizing solar and biomass energies as renewable sources, employing high temperature and pressure ranges for analysis. A new energy system is introduced, using biomass to produce hydrogen and other valuable commodities. The study evaluates power and hydrogen production technologies from a thermodynamic perspective, including conventional biomass gasification, calcium and iron thermochemical looping cycles, and gasification with supercritical water, incorporating carbon capture techniques. It assesses and compares the performance of locally available biomass material, such as cotton stalk, during gasification. Results show that employing the supercritical water gasification cycle yields the highest hydrogen production (8330 kg/h) and carbon capture rate (92.91 %), with potential for significant reduction in CO2 emissions. Supercritical water gasification also demonstrates electricity, heating, and CO2 production rates of 51.48 MW, 23.3 MW, and 16.6 MW, respectively. Integrating supercritical water gasification with solar energy enhances syngas productivity and system efficiency. Additionally, the highest performance is demonstrated in the SCWG case, which exhibits the lowest irreversibility at 320.32 MW. In conclusion, the system with supercritical water gasification emerges as the most efficient biomass conversion method, with higher energy and exergy efficiencies of 67.59 % and 49.74 %, respectively, under specific operating conditions. The developed model facilitates integration of solar energy into biomass gasification, enabling prediction and comparison of performance in terms of energy and exergy efficiencies.

A case study of thermal performance of gas-steam combined cycle with gas turbine inlet air cooling and condenser deep cooling

To enhance power generation during high summer temperatures and address the power supply and demand imbalance in gas-steam combined cycle, this study explored the exhaust gas waste heat refrigeration scheme, along with the optimal scheduling of cooling capacity between the precooling of inlet air for the gas turbines and deep cooling for condenser in steam cycle. Using the Ebsilon software, we investigate the thermal performance of the gas cycle, steam cycle, and the overall gas-steam combined cycle under various off-design operating conditions, including varying cooling capacity distributions, ambient temperatures, and generation loads. Based on our calculations, it is advisable to prioritize cooling capacity for precooling the ambient air for the gas cycle, balancing power generation and thermal efficiency. After the transformation, the power generation of the gas-steam combined cycle remains relatively stable across varying ambient temperatures, achieving a significant 10.9 % increase compared to pre-transformation levels under a 39 °C ambient temperature and 100 % generation load. Furthermore, the thermal efficiency of the gas-steam combined cycle improves by 1.11 % under a 40 % generation load condition. As ambient temperatures rise, the benefits of the inlet air cooling scheme become more apparent, validating its effectiveness in addressing the inherent summer power supply and demand challenges.

Study of the Effects of Different Ambient Gases and Buoyancy on Hydrogen Jet Characteristics.

Substituting nitrogen with inert gases in an inert gas cycle engine can not only effectively improve engine efficiency but also eliminate NOX emissions in the combustion products. Owing to the low density of hydrogen, jet development is affected by buoyancy. This study explored the effects of different ambient gases, such as Ar, N2, and He, as well as buoyancy, on the hydrogen jet and mixing characteristics based on Schlieren. The results indicated that as the pressure ratio increases, the penetration length and volume of the hydrogen jet increase, whereas the dispersion angle and entrainment ratio decrease. The penetration capacity of the hydrogen jet is strongest in He, followed by N2, and weakest in Ar. Additionally, in He, the hydrogen jet exhibits the smallest dispersion angle, fastest jet volume growth, and largest entrainment ratio. The entrainment ratio of the H2 jet in He is 2.75-3.84 times that of N2 and 4.72-8.3 times that of Ar. In N2 and Ar, the penetration length of the inverted jet after 2.5 ms is approximately 2-4 mm longer than that of the upright jet, indicating that buoyancy has a certain influence on jet development.

Performance analysis of a new compressed air energy storage system coupled with the municipal solid waste power generation systems

In order to improve the performance of the compressed air energy storage (CAES) system, a novel design is proposed: the CAES system is combined with the municipal solid waste power generation systems, including a waste incineration power generation system and a biogas power generation system. During the charging process, the feedwater and the condensate from the waste incineration power generation system are used to cool the compressed air. During the discharge process, the released compressed air is heated by the flue gas from the waste incineration power generation system, and the high-temperature compressed air works in the expander. Finally, the expanded air from the expander is fed into the combustor of the biogas power generation system, thus replacing the compressor of the gas cycle. Through the system integration, the efficiency of the CAES system is improved, and some equipment of the original CAES system is reduced. Based on the systems simulation, energy analysis, exergy analysis, economic analysis, and sensitivity analysis are performed. As a result, for the CAES subsystem, the round-trip efficiency, the energy storage density, and the exergy efficiency can reach 75.32 %, 14.10 MJ/m3, and 74.31 %. Besides, the dynamic payback period can reach 6.82 years.

The Hybrid Concept of Turboshaft Engine Enhanced by Steam Cycle Using Waste Heat Recovery—Combined Analytical and Numerical Calculation of Its Efficiency

<div>The article presents a hybrid concept of a turboshaft engine that fits into the area of PGE (pressure-gained combustion). It combines the advantages and elements of a piston engine and a turbine engine. The combustion takes place in isochoric chambers. The proposed timing system of the engine efficiently realizes the Humphrey cycle. Additionally, the main gas cycle engine was enhanced by the Clausius–Rankine steam cycle to achieve effective power of engine equal to 1231.3 kW. It was supplied by waste heat recovery from the exhaust gas. The enhancement of the engine by the secondary steam cycle significantly improved engine effective efficiency with a final value reaching 0.446. The effective efficiency and specific fuel consumption of the engine were calculated using merged analytical–numerical CFD (computational fluid dynamics) analysis. The centrifugal compressor, gas turbine, and steam turbine can work on the common shaft whose rotational velocity is 35,000 rpm. Because of additional weight, it could have potential applications for stationary use or heavy military units.</div>

Development a policy for the production of Bitcoins with renewable energy sources

Bitcoin, the first decentralized digital currency introduced by an anonymous person or group since 2008, has attracted worldwide attention. A significant number of economists have introduced Bitcoin as a new phenomenon in the 21st century that could reduce global inflation. Given the tens of thousands of digital currencies that have emerged since the advent of Bitcoin and its price growth trend over more than a decade, which are signs of the growth of this business. In addition to being money, Bitcoin has always been considered a tool for investing and storing value, which is why it is called digital gold. One of the most important problems in the production or extraction of Bitcoins is the high-power consumption by miners. If the energy sources of electricity generation are supplied by non-renewable energy sources, in addition to emitting air pollutant gases, it will increase greenhouse gases and consequently contribute to climate change. In this research, based on the idea of the authors, which is that the economic support of Bitcoin is energy, a strategy for producing Bitcoin from renewable energy sources is considered. First, the amount of electrical energy consumption by Bitcoin production is calculated based on statistical data, and then based on the price of electricity in different countries of the world and its global average, the base price of Bitcoin is calculated. In the following, four scenarios are proposed for the production of Bitcoin by electricity supplied from non-renewable energy sources. These scenarios include coal-fired steam power plants, natural gas-fired power plants, natural gas/oil gas-fired power plants, and dual-cycle (steam and gas cycles) natural gas-fired power plants. Based on the amount of electricity required to produce one Bitcoin, the amount of pollutants emitted to produce Bitcoin and its social costs are calculated. These costs should be added to the base cost of Bitcoin production if non-renewable energy sources are used to produce Bitcoin. Then, renewable energy sources for Bitcoin production based on the price of electricity generated by renewable energy sources are examined. Based on the analyses, how to choose the best renewable energy source to produce Bitcoin is presented as a scenario. This article briefly answers two key questions: 1. At what price of Bitcoin is it cost-effective for governments to produce it? 2. What is the best renewable energy source to produce it? These two questions can be useful in creating a roadmap and strategy for economists and governments.

Modelling and Output Power Estimation of a Combined Gas Plant and a Combined Cycle Plant Using an Artificial Neural Network Approach

Artificial neural networks (ANNs) have gained prominence among contemporary computing techniques due to their capacity to handle complicated stochastic datasets and nonlinear modelling in combined gas and combined cycle power (COGAS) plants. Researchers, academicians, and stakeholders have been unable to predict, ensure effective operation, and prevent power outages in COGAS due to the nonlinearity. The first implementation of the simultaneous adoption of three types of ANNs using Levenberg–Marquardt (LM), Bayesian regularisation (BR), and scaled conjugate gradient (SCG) configurations for training and assessing a combined cycle power plant output is presented. The dataset used in this research is a 9568-unit full combined cycle power plant basis load dataset, accessible through the public UCI Machine Learning Repository. It incorporates ambient temperature, exhaust vacuum, ambient pressure, and relative humidity as input parameters to predict the electric output power. The most accurate and dependable electric power predictions could be identified for 70% of the total data, of which 6698 were trained, 15% were tested, and 15% were validated (2870). By using the three training techniques, namely, LM, BR, and SCG, the parameterized networks are studied, increasing the number of hidden layers from 20 to 500. The lowest root-mean-square error value for a multilayer perceptron (MLP) architecture is 3.631%, which is lower than the values of 4.17%, 4.35%, and 4.63% for comparable MLP structures (20 to 500), documented in the literature. The LM and BR algorithms outperform SCG. These adopted algorithms could be a cutting-edge application in the power plant industry and other real-world applications for reliable solutions, to satisfy emerging societal needs with environmental benefits.

Perceptions of social disruption in communities that experienced induced seismicity from hydraulic fracturing in Colorado and Oklahoma, USA

This study tests a conceptual model of perceptions of community social disruption (measured as crime and violence, boom and bust oil and gas cycles, social disruption to the community, built environment/infrastructure related concerns, family disruption, and personal life disruption) from hydraulic fracturing. Data come from a sample of 1200 households located in hydraulic fracturing communities that also experienced induced seismicity in Colorado and Oklahoma. Results of structural equation models suggests residents who (1) reside near fracking drill sites, (2) identify as racial/ethnic minorities, (3) have lower socio-economic status (4) view fracking as a risk, (5) are liberal, and (6) do not trust institutions associated with hydraulic fracturing, are all likely to report perceptions of community social disruption. These results emphasize that the perceived effects of hydraulic fracturing matter but are not experienced equally by all members of the community. As a result, environmental injustices emerge and have consequences for perceptions of community social disruption.

Effect of Ni/SiO2 catalyst preparation method on methane decomposition and CO2 gasification cycles

Catalytic methane decomposition is a promising reaction to produce CO2-free hydrogen from methane-rich feedstock with solid carbon as a by-product. Significant research conducted on this reaction to find ways to manage and utilize this solid carbon. In this work, the methane decomposition reaction is followed by Reverse Boudouard Reaction using CO2 feedstock to convert the solid carbon to carbon monoxide, which is a valuable starting component for many chemical applications. Realizing this promising concept would require a catalyst that is efficient for both reactions. Herein, we explored the potential of using solution combustion synthesis (SCS) to make a 5 wt% of Ni supported SiO2 catalyst and benchmarked it versus the conventional impregnation method. The catalyst prepared by SCS showed an improved performance at different temperatures, space velocities, and catalyst pellet sizes. The SCS catalyst successfully completed five repeated cycles reaching up to 38.1 h of stable time on stream operation, whereas the impregnated catalyst was not able to complete the second testing cycle with only 14 h of time on stream operation. A thorough characterization using XRD, H2 and O2 TPR, TEM, SEM, XPS, and Raman spectroscopy were conducted to provide an adequate explanation for the observed performances for both catalysts. The Ni nanoparticles size and distribution, the strength of the metal support interaction, and the nature of graphitic carbon were the key factors affecting the catalytic performance. Insights on how to make an optimal catalyst for this promising process is identified which is a step forward toward making separated H2 and CO streams from methane feedstock and CO2, respectively.

Sustainable approach to integrate a conventional power plant and renewable energies, coupled with the Goswami cycle and Maisotsenko heat exchanger

AbstractThis paper presents a pioneering investigation into an integrated power generation cycle that combines gas turbines, steam turbines, Goswami cycles, biomass fuel, solar energy sources, and advanced Maisotsenko heat exchangers. Biomass gasification has been applied to partially fuel the gas turbine, while the M‐Cycle serves as the gas turbine inlet air cooling system. Solar parabolic collectors are utilized to elevate the compressed air temperature for combustion, and the Goswami cycle generates both power and cooling through waste heat recovery. This research addresses a critical gap by undertaking a holistic examination of the integrated power generation cycle, modelling the overall system performance by considering interactions and synergies between various components. The base model has been implemented, and the impacts of influential parameters on system efficiency, such as ambient temperature, seasonal variation, and steam‐to‐biomass ratio, have been taken into consideration. Remarkably, the incorporation of the M‐Cycle, solar parabolic systems, steam cycles, and the Goswami cycle into the base gas cycle results in substantial energy efficiency enhancements of 1.59%, 1.96%, 16.87%, and 6.06%, respectively, highlighting the transformative potential of this integrated approach for sustainable and efficient power generation.

Development of Mass–Energy Balance Model Based on a New Process of RSF with Hy-O-CR

At present, blast furnace (BF) ironmaking is still the main process for producing hot metal in China and around the world. Under the constraint of the global goal of “double carbon”, it is urgent to carry out hydrogen metallurgical innovation for the existing BF ironmaking process with higher carbon emissions. In recent years, BF technology with hydrogen enrichment and pure oxygen has made some progress, effectively reducing carbon emissions of hot metal per tons, but it is still unable to break through the technical bottleneck of emission reduction of more than 30%. In view of this, the authors put forward an ironmaking technology of a reduction smelting furnace (RSF) that is hydrogen-rich and utilizes pure oxygen and carbon recycle (Hy-O-CR), which breaks through the technical defect of traditional BF emission reduction of less than 30% by reshaping the furnace. Firstly, the construction process of the mass and energy balance model for two main unit modules in the new process (RSF with Hy-O-CR and top gas cycle) is introduced, and then the parameter optimization under specific scenario conditions is analyzed, and the influence mechanism of several key variables on the parameters in the furnace is obtained. Finally, the emission of CO2 in the whole process is explored in the case of two typical operating parameters. The results show that after using CCUS technology, the minimum value of direct CO2 emission is 215.93 kg/tHM, which is as high as 84.58% compared with the traditional BF process. Even if the removed CO2 is counted in carbon emissions, the minimum value of direct or indirect carbon emissions is 729.85 kg/tHM, and the proportion of emission reduction can reach 47.87%. The research results show that the reconstruction of Hy-O-CR technology can change the ratio of direct reduction and indirect reduction, which greatly breaks through the emission limit of the traditional BF and provides a new reference for hydrogen metallurgy technology and a basis for further study of the optimization of RSF size.

Environmental and exergoeconomic analysis of a low-carbon polygeneration process based on biomass energy, a geothermal source and a high-temperature fuel cell

Abstract By combining renewable energy resources, we can expect higher efficiency from energy systems, which in turn can facilitate their commercialization. In addition, fuel cells are among the clean devices that provide superior performance with zero environmental pollution. Fuel cells can improve the stability of the energy conversion system by storing energy. This paper introduces and analyzes a polygeneration system driven by a biomass fuel and a geothermal source. The system consists of a high-temperature fuel cell coupled with a gasification cycle. In addition, a triple-flash geothermal cycle, a refrigeration unit, and a proton-exchange membrane (PEM) electrolyzer are used in the bottoming cycle. Accordingly, power, hydrogen, and cooling and heating capacities are considered as products of the system. Energy, exergy, environmental and economic analyses have been applied to evaluate the system. Besides that, the optimal working conditions of the system based on two decision-making methods have been identified. According to the findings, the outputs of power and hydrogen from the polygeneration system were equal to 3880.8 kW and 0.356 kg/h. Also, cooling and heating capacities of 2168.1 and 1534.5 kW can be obtained. Accordingly, the system will be 33.16% and 60.39% efficient in terms of energy and exergy. Further, the total emitted CO2 and product unit cost are 57.75 kg/GJ and 5.802$/GJ. According to the TOPSIS decision-making method, more optimal environmental and cost findings can be achieved than using the LINMAP method.

Exergoeconomic and exergoenvironmental analyzes of a new biomass/solar-driven multigeneration energy system: An effort to maximum utilization of the waste heat of gasification process

In addition to improving the sustainability and thermodynamic efficiencies of an energy conversion system, a solar/biomass-driven integrated energy system can also reduce environmental impacts. The current work presents a detailed evaluation (thermodynamic simulation and exergoenvironmental and exergoeconomic analyzes) of a solar/biomass-powered multigeneration energy system (MGES). Accordingly, four units were considered for electric power generation. A linear Fresnel concentrator (LFC)-driven solar farm, a municipal solid waste (MSW) gasification cycle, an alkaline water electrolyzer (AWE) unit (to produce hydrogen gas), and a multi effect desalination (MED)-based Seawater desalination cycle are also considered in the MGES. A multi-objective optimization (regarding the technical, cost, and environmental objective functions) was also developed for the offered MGES. The proposed configuration for the MGES has a new components process that had not been reported in the publications. The power generation level was improved by utilizing the energy available in waste heat in the different downstream units. The offered MGES can generate 154.1 MW of electrical power, ∼ 280 kg per day of hydrogen gas, and 265.4 m3/h of fresh water. Meantime, the offered MGES can 38.8 % and 32.2 % efficient in terms of energy and exergy, respectively. Besides, the LCOE value and the environmental impacts index for the offered MGES were approximately 3.82 USD/GJ and 0.545 Pts/GJ, respectively. Also, raising the syngas temperature at the inlet of the combustion chamber can be a reasonable decision from the exergetic, economic and (especially) environmental standpoints.

Thermo-Economic Analysis of Gas Turbine Combined Multistage Flash (MSF) Desalination Cycle

Over the past few decades, the growth of the earth’s population has increasingly contributed to global warming, and increased demand for fresh water on top of a need for a greater power supply. This paper will analyze the integration of a combined- gas turbine with intercooler and a multi-stage flash (MSF) desalination plant for the simultaneous generation of electricity and supply of water and improved performance. The paper will also examine the calculation of the production cost and the capital cost of the MSF desalination plant. The thermo-economic analysis of the study was conducted using the IPSEpro software system. Also, exergy losses of the gas turbine and MSF desalination unit were also calculated. The desalination plant uses the exhaust gases from the gas turbine, as a form of thermal energy, and discharges to feed the seawater heater. A portion of the desalinated water is used to cool the compressed air in the intercooler heat exchanger. Results indicate the improvement in the gas turbine’s performance when desalinated water is used for the intercooler between compressor stages, as the power output increased by 59% over the the simple gas cycle and found decrease with an increase in the ambient temperature. The desalinated water cost was calculated to be $1.7 per cubic meter after determining the optimal configuration and operating conditions. A decrease in steam cost by 36% was observed when the waste heat from the gas turbine was used as the source of thermal energy. Part of this reduction can be explained by the observation that the desalination plant’s pumps consume part of the power generated by the gas turbine.

Developing and optimizing a new cogeneration cycle to produce hydrogen from seawater

Global warming and the depletion of fossil fuels have driven countries to develop alternative fuel strategies. As an alternative fuel, hydrogen is very attractive since it has a high thermal energy and near-zero emissions. This paper proposes a new arrangement of the cogeneration cycle for hydrogen production from seawater is proposed and optimized via the multi-objective swarm optimization (MOPSO) algorithm. In this survey, hydrogen is produced through the electrochemical cycle Copper-Chloride (Cu-Cl), using the heat and electricity provided via waste heat recovery of a gas cycle. A reverse osmosis system provides drinking water for the Cu-Cl cycle. This cycle can produce 256 GWh of electricity and 23616 tons/year of hydrogen during a year. This cycle's first and second law efficiencies are 35.3 % and 7.2 %. Based on the financial aspects, this cycle's investment return time equals 4.1 years. By using MOPSO algorithm, the exergy efficiency of the cogeneration system is improved by 22.7 %, while the payback is decreased by around 33.3 %.

Temperature transition optimization in cryogenic systems: Application to liquid nitrogen expenditure reduction in a thermal vacuum chamber case study

This paper presents outcomes regarding liquid nitrogen consumption reduction in a thermal vacuum chamber, with the motivation of lessening operational costs during space equipment testing. The article briefly outlines the optimal control application to thermal and cryogenic-related control systems based on a gas cycle, and assesses liquid nitrogen savings opportunities for a chamber including six shrouds with independent temperature requirements. In this case study, optimization of temperature transition profiles and a proposed modification in the control setup yielded potential savings from 14.1% to 20.4% in the examined experimental transitions.

Technology for trimming of greenhouse gas in thermal plant system

Industrial expansion depends largely on electric power generation for its operations. These industrial activities have contributed significantly to environmental degradation from frequent emission of large volume of greenhouse gases. Concentration of suspended greenhouse gases in the air of many cities exceed World Health Organization standards and its effect on human health can be devastating. Thus, utmost importance is to generate clean and efficient energy from power plant. The aim of this work is to foster a way of reducing emissions in Power Plants by integrating gasification technologies to the system. Emission data from thermal power plant was analysed with varying gasifier pressure, air-fuel ratio, steam-fuel ratio, and flue gas-fuel ratio. Numerical simulation of the gasification cycle with varying parameters was carried out using MATLAB. The analysis indicated supplementary power generation and cleaner exhaust. The progress of this work can greatly reduce greenhouse emission.

Coupling a Gas Turbine Bottoming Cycle Using CO2 as the Working Fluid with a Gas Cycle: Exergy Analysis Considering Combustion Chamber Steam Injection

Gas turbine power plants have important roles in the global power generation market. This paper, for the first time, thermodynamically examines the impact of steam injection for a combined cycle, including a gas turbine cycle with a two-stage turbine and carbon dioxide recompression. The combined cycle is compared with the simple case without steam injection. Steam injection’s impact was observed on important parameters such as energy efficiency, exergy efficiency, and output power. It is revealed that the steam injection reduced exergy destruction in components compared to the simple case. The efficiencies for both cases were obtained. The energy and exergy efficiencies, respectively, were found to be 30.4% and 29.4% for the simple case, and 35.3% and 34.1% for the case with steam injection. Also, incorporating steam injection reduced the emissions of carbon dioxide.