The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Yousef Haseli - One of the best experts on this subject based on the ideXlab platform.
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Efficiency of irreversible Brayton Cycles at minimum entropy generation
Applied Mathematical Modelling, 2016Co-Authors: Yousef HaseliAbstract:Abstract System level optimization of power plants is mainly based on the thermodynamic laws. Various objective functions are proposed that are based on the 1st and 2nd law of thermodynamics. Given the fast technological advancement of power plants, it is important to understand which optimization objective should be used in practical applications. The objective is to find out whether an entropy-based optimization may be useful when designing gas turbine engines operating on Brayton Cycle. The study considers three configurations of Open Brayton Cycle: a regenerative Cycle, a reheat regenerative Cycle, and an intercooled regenerative Cycle. The operational regimes at maximum thermal efficiency, maximum work output and minimum entropy production of these power Cycles are compared. The results reveal that a reduction in Cycle entropy production is neither equivalent to an increase in its thermal efficiency; nor to an increase in its work output. Under special circumstances, minimum entropy production design may be identical to maximum thermal efficiency design and/or maximum work output design. The minimum entropy production, the maximum thermal efficiency, and the maximum work output criteria may be equivalent at the condition of fixed heat input . The two first criteria may also lead to an identical design at the condition of fixed work output . It is demonstrated that for practical applications, thermodynamic optimization of gas turbine power plants should continue to be based upon maximum thermal efficiency or maximum work output criteria. An entropy-based design should be avoided.
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optimization of a regenerative Brayton Cycle by maximization of a newly defined second law efficiency
Energy Conversion and Management, 2013Co-Authors: Yousef HaseliAbstract:Abstract The idea is to find out whether 2nd law efficiency optimization may be a suitable trade-off between maximum work output and maximum 1st law efficiency designs for a regenerative gas turbine engine operating on the basis of an Open Brayton Cycle. The primary emphasis is placed on analyzing the ideal Cycle to determine the upper limit of the engine. Explicit relationships are established for work and entropy production of the ideal Cycle. To examine whether a Brayton Cycle may operate at the regime of fully reversible characterized by zero entropy generation condition, the Cycle net work is computed. It is shown that an ideal Brayton-type engine with or without a regenerator cannot operate at fully reversible limit. Subsequently, the analysis is expanded to an irreversible Cycle and the relevant relationships are obtained for net work, thermal efficiency, total entropy production, and second law efficiency defined as the thermal efficiency of the irreversible Cycle divided by the thermal efficiency of the ideal Cycle. The effects of the compressor and turbine efficiencies, regenerator effectiveness, pressure drop in the Cycle and the ratio of maximum-to-minimum Cycle temperature on optimum pressure ratios obtained by maximization of 1st and 2nd law efficiencies and work output are examined. The results indicate that for the regenerator effectiveness greater than 0.82, the 2nd law efficiency optimization may be considered as a trade-off between the maximum work output and the maximum 1st law efficiency.
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Second law efficiency optimization of a regenerative gas turbine power plant
2010Co-Authors: Yousef Haseli, J.a. Van OijenAbstract:The idea is to find out whether 2nd law efficiency optimization may be a suitable trade-off between maximum work output and maximum 1st law efficiency designs for a regenerator gas turbine engine operating on the basis of an Open Brayton Cycle. It is shown that an ideal Brayton-type engine with or without a regenerator cannot operate at fully reversible limit; regime of zero entropy generation. Hence, the 2nd law efficiency of the power Cycle is defined as the ratio of the 1st law efficiency to the efficiency of the ideal power Cycle. For an ideal Cycle, minimization of entropy production is equivalent to maximization of the system thermal efficiency. Except at regenerator effectiveness of 50 percent, at which maximum work output, maximum 1st law efficiency, and minimum entropy generation become identical, no relation is observed between these three optimization criteria for an irreversible engine. A design region is established within which pressure ratio of a real engine must lie between optimum pressure ratios corresponding to maximum work output and maximum 1st law efficiency, respectively, as the upper and the lower limits of this region. The results indicate that the 2nd law efficiency optimization is approximately equivalent to maximum work output design when regenerator effectiveness is between 0.78 and 0.82. For the regenerator effectiveness beyond 0.82, the 2nd law efficiency optimization may be considered as a trade-off between optimized work output and 1st law efficiency. However, if the effectiveness value happens to be less than 0.78, the 2nd law efficiency optimization may give no useful design information.
Mariano Martín - One of the best experts on this subject based on the ideXlab platform.
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optimal coupling of a biomass based polygeneration system with a concentrated solar power facility for the constant production of electricity over a year
Computers & Chemical Engineering, 2015Co-Authors: Marta Vidal, Mariano MartínAbstract:Abstract In this paper we address the integration of a polygeneration system based on biomass with a concentrated solar power facility for the constant production of electricity over a year long. The process is modelled as a superstructure embedding two different gasification technologies, direct and indirect, and two reforming modes, partial oxidation or steam reforming followed by gas cleaning and three alternatives for the syngas use, water gas shift reactor (WGSR) to produce hydrogen, a furnace for thermal energy production and an Open Brayton Cycle. We couple this system with a concentrated solar plant that uses tower technology, molten salts and a regenerative Rankine Cycle. The problem is formulated as a multi-period mixed-integer non linear programming problem (MINLP). The optimal integration involves the use of indirect gasification, steam reforming and a Brayton Cycle to produce 340 MW of electricity at 0.073 €/kWh and 97 kt/yr of hydrogen as a credit.
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optimal integration of a concentrated solar plant facility with a biomass based polygeneration system
Computer-aided chemical engineering, 2014Co-Authors: Marta Vidal, Lidia Martin, Mariano MartínAbstract:Abstract In this paper we address the integration of a polygeneration system based on biomass with a concentrated solar power facility for the constant production of electricity over a year long. The process is modeled as a superstructure embedding two different gasification technologies, direct and indirect, and two reforming modes, partial oxidation or steam reforming, followed by gas cleaning and three alternatives for the syngas use, water gas shift reactor (WGSR) to produce hydrogen, a furnace for thermal energy production and an Open Brayton Cycle. We couple this system with a concentrated solar plant that uses tower technology, molten salts energy storage, and a regenerative Rankine Cycle. The problem is formulated as a multi-period mixed-integer non linear programming problem (MINLP). The optimal integration involves the use of indirect gasification and steam reforming using the Brayton Cycle to produce 340 MW of electricity and 97 kt/yr of hydrogen. The electricity cost is 0.073 $$/kWh.
C.f. Sanders - One of the best experts on this subject based on the ideXlab platform.
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Status report of the EPA`s air pollution prevention and control division`s biomass-to-energy development and demonstration projects. Report for July 1994-June 1996
1996Co-Authors: C.r. Purvis, J. Cleland, J.d. Craig, C.f. SandersAbstract:The paper reports the status of three EPA biomass-to-energy development and demonstration projects. EPA`s Air Pollution Prevention and Control Division is participating in research, development, and demonstration projects with goals of coverting biomass energy to electrical power, waste utilization, pollution alleviation and energy conservation. Each project is aimed at demonstration of the technical, economic, and environmental feasibility of an innovative energy conversion technologic. The first project is a demonstration of a design by Thermal Technology, Inc. and Mech-Chem and Associates, Inc. that consists of a fixed-bed gasifier, a gas cleanup system, and a syngas and diesel engine. The second project is a continuation of the development of the Cratech, Inc. biomass-fueled integrated-gasifier gas turbine power plant. The third project is a demonstration of the ENERGEO, Inc. AGRI-POWER 200 biomass-fueled power plant that operates with an Open Brayton Cycle using fluidized-bed combustor and several heat exchangers to heat compressed air and drive a turbine/generator set. The system also discharges clean hot air that can be used for cogeneration.
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Status Report of the EPA's Air Pollution Prevention & Control Division's Biomass-to Energy Development & Demonstration Projects.
1996Co-Authors: C.r. Purvis, J. Cleland, J.d. Craig, C.f. SandersAbstract:The US Environmental Protection Agency`s (EPA`s) Air Pollution Prevention and Control Division (APPCD) is participating in research, development, and demonstration projects that will convert biomass energy to electrical power, resulting in waste utilization, pollution alleviation, and energy conservation. The goal is to demonstrate the technical, economic, and environmental feasibility of an innovative energy conversion technology. This paper describes the status of each project. The first project is a demonstration of a design that consists of a fixed-bed gasifier, a gas cleaning system, a spark ignited syngas engine, and a diesel dual fuel engine. The technology will use wood waste as fuel and produce approximately 1 MWe. The design of the technology is complete, equipment fabrication is underway, and installation, start-up, testing, and demonstration will follow by September 1996. The second project is a biomass-fueled intergrated-gasifier gas turbine (BIGGT) power plant. Phase 1 is complete and consisted of the design, fabrication, and operation of a 0.5 metric ton per hour (tph) (0.55 tph) pressurized fluidized-bed gasifier with a slipstream hot gas cleanup system. Phase 2 is to increase the feed rate to 1 metric tph (1.1 tph) and uprate the gasifier to operate at 10 atmospheres (981 kPa) with a fullmore » scale, dry, hot gas cleanup system capable of being integrated with a 1 MWe rated gas turbine engine. Construction of Phase 2 will begin in the summer of 1996. The third project is a demonstration of a biomass-fueled power plant. The system operates with an Open Brayton Cycle using a fluidized-bed combustor and heat exchangers to heat compressed air and drive a turbine/generator set. The system discharges clean hot air which can be used for cogeneration applications. The system will use lumber wastes as fuel and will produce approximately 200 kWe. Fabrication is underway, and the demonstration is scheduled to accumulate 8000 hours of operation over 1 to 2 years.« less
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Installation of an ENERGEO Biomass Power Plant at a Lumber Company
1995Co-Authors: C.f. Sanders, C.r. PurvisAbstract:Abstract : ENERGEO, Inc. is engaged in a demonstration test program of its AGRIPOWER 200 unit fueled with biomass at Sutton Lumber Company in Tennga, Georgia. The objective of the program is to evaluate the operating and performance characteristics of the system using lumber wastes for fuel. The program is scheduled to accumulate 800 hours of operation over a period of 1 to 2 years. The program became a reality due to initial funding from the U.S. Department of Defense's (DoD's) Strategic Environmental Research and Development Program (SERDP) and the U.S. Environmental Protection Agency's (EPA's) Air and Energy Engineering Research Laboratory (now referred to as National Risk Management Research Laboratory (NRMRL), Research Triangle Park). The AGRIPOWER unit operates with an "Open" Brayton Cycle using a fluid bed combustor and several heat exchangers to heat compressed air which in turn drives a turbine/generator (T/G) set. The T/G set, which includes the compressor and a recuperator, is a Solar "Spartan" unit packaged for this application by Alturdyne, Inc. The combustor utilizes both in-bed and freeboard combustion zones, and the above-bed zone is well mixed to provide uniform temperatures.
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Demonstration of a 200-kilowatt biomass fueled power plant. Report for February 1992-August 1994
1994Co-Authors: C.f. Sanders, C.r. Purvis, A.p. BrayAbstract:The paper discusses the demonstration of a 200-kW biomass-fueled electric power plant. The objective of the demonstration is to evaluate the operating and performance characteristics of the system using lumber wastes for fuel. It is scheduled to accumulate 8000 hours of operation over a period of one to two years. Energeo`s Agripower unit operates with an Open Brayton Cycle using a fluid-bed combustor and several heat exchangers to heat compressed air which, in turn, drives a turbine-generator (T-G) set.
Huaixin Wang - One of the best experts on this subject based on the ideXlab platform.
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Parametric Optimization of Brayton /Organic Trans-critical Combined Cycle for Flue Gas Waste Heat Recovery
Energy Procedia, 2015Co-Authors: Qiang Zhu, Huaixin WangAbstract:Abstract A combined Cycle composed of an air based Open Brayton Cycle (BC) and an organic trans-critical Cycle (OTC) is presented for power recovery from flue gas of initial temperature around 600 °C. BC is employed as the top Cycle to span the temperature gap between the heat source and the OTC bottom Cycle, and offers a desirable temperature matching between the heat source's heat rejection process and the heat addition process of the Cycle. Air is selected as working fluid for BC owing to its outstanding thermal stability. Parametric optimization on the combined Cycle is carried out to maximize the net power output of the system at a given mass flow rate of the flue gas. The results show that the choice of OTC working fluid and pressure ratio value of the BC dominate the system performances, while the values of other parameters like the initial temperature of air in BC expansion process, the initial pressure and temperature of the organic fluid in OTC expansion process, and the condensing temperature of OTC also affect the system performances. Benzene, toluene, heptanes, acetone and R113 are screened as candidates for OTC working fluid, and maximum net power output of 175.87 kJ/(kg-flue gas) is achieved with benzene.
Vlatko Materić - One of the best experts on this subject based on the ideXlab platform.
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Calcium looping in solar power generation plants
Solar Energy, 2012Co-Authors: Susan E.b. Edwards, Vlatko MaterićAbstract:The use of a calcium looping based process as a thermal storage and transportation system for concentrated solar power plants is proposed in this work. This system exploits the reversible calcination–carbonation reaction of limestone and lime. Concentrated solar heat is used to calcine CaCO3, which is then released as required by carbonating the resulting CaO. The CaO/CaCO3 system has a high energy density and its high temperature operation allows the use of a gas turbine for power production. This paper presents a first order evaluation of the potential of this application of calcium looping, with particular consideration given to carbonation activity of the sorbent. A model including a solar calciner and a pressurised fluidised bed carbonator feeding a gas turbine in an Open Brayton Cycle has been developed. Results from the model indicate that electric efficiencies of 40–50% could be achieved with sorbent carbonation activities between 15% and 40%. Higher sorbent activity levels do not affect efficiency but would lead to lower capital costs. According to the model, CaO activity levels above 17% lead to significant reductions in the required storage volume over existing systems, such as molten salts. In principle, high efficiency and smaller footprint solar thermal power plants are possible with calcium looping. Such plants would have no process use of water and could be used as baseload, variable demand load or microgrid systems.
