1,721,092 research outputs found
Techno-economic assessment of hydrogen selective membranes for CO2 capture in integrated gasification combined cycle
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Using Hydrogen as Gas Turbine Fuel: Premixed Versus Diffusive Combustors
No full textThis work aims at estimating the efficiency gain resulting from using lean premixed combustors in hydrogen-fired combined cycles with respect to diffusive flame combustors with significant inert dilution to limit NOx emissions. The analysis is carried out by considering a hydrogen-fired, specifically tailored gas turbine whose features are representative of a state-of-the-art natural gas-fired F-class gas turbine. The comparison between diffusion flame and lean premixed combustion is carried out considering nitrogen and steam as diluents, as well as different stoichiometric flame temperatures and pressure drops. Results show that the adoption of lean premixed combustors allows us to significantly reduce the efficiency decay resulting from inert dilution. Combined cycle efficiency slightly reduces from 58.5%-57.9% when combustor pressure drops vary in the range 3%-10%. Such efficiency values are comparatively higher than those achieved by diffusive flame combustor with inert dilution. Finally, the study investigated the effects of decreasing the maximum operating blade temperature so as to cope with possible degradation mechanisms induced by hydrogen combustio
Analysis of direct carbon fuel cell (DCFC) based coal fired power cycles with CO2 capture
No full textASME GT2012-6977
Predicting the ultimate potential of natural gas SOFC power cycles with CO2 capture - Part B: Applications
No full textAn important advantage of solid oxide fuel cells (SOFC) as future systems for large scale power generation is the possibility of being efficiently integrated with processes for CO2 capture. Focusing on natural gas power generation, Part A of this work assessed the performances of advanced pressurised and atmospheric plant configurations (SOFC + GT and SOFC + ST, with fuel cell integration within a gas turbine or a steam turbine cycle) without CO2 separation. This Part B paper investigates such kind of power cycles when applied to CO2 capture, proposing two ultra-high efficiency plant configurations based on advanced intermediate-temperature SOFCs with internal reforming and low temperature CO2 separation process. The power plants are simulated at the 100 MW scale with a set of realistic assumptions about FC performances, main components and auxiliaries, and show the capability of exceeding 70% LHV efficiency with high CO2 capture (above 80%) and a low specific primary energy consumption for the CO2 avoided (1.1-2.4 MJ kg-1). Detailed results are presented in terms of energy and material balances, and a sensitivity analysis of plant performance is developed vs. FC voltage and fuel utilisation to investigate possible long-term improvements. Options for further improvement of the CO2 capture efficiency are also addressed
Optimal design of multi-energy systems with seasonal storage
Full text linkOptimal design and operation of multi-energy systems involving seasonal energy storage are often hindered by the complexity of the optimization problem. Indeed, the description of seasonal cycles requires a year-long time horizon, while the system operation calls for hourly resolution; this turns into a large number of decision variables, including binary variables, when large systems are analyzed. This work presents novel mixed integer linear program methodologies that allow considering a year time horizon with hour resolution while significantly reducing the complexity of the optimization problem. First, the validity of the proposed techniques is tested by considering a simple system that can be solved in a reasonable computational time without resorting to design days. Findings show that the results of the proposed approaches are in good agreement with the full-scale optimization, thus allowing to correctly size the energy storage and to operate the system with a long-term policy, while significantly simplifying the optimization problem. Furthermore, the developed methodology is adopted to design a multi-energy system based on a neighborhood in Zurich, Switzerland, which is optimized in terms of total annual costs and carbon dioxide emissions. Finally the system behavior is revealed by performing a sensitivity analysis on different features of the energy system and by looking at the topology of the energy hub along the Pareto sets
A MILP model for the design of multi-energy systems with long-term energy storage
No full textOptimal design and operation of multi-energy systems involving seasonal energy storage are often hindered by the complexity of the optimization problem. Indeed, the description of seasonal cycles requires a year-long time horizon, while the system operation calls for an hour resolution; this turns into a large number of decision variables, especially binaries. This work presents a novel mixed integer linear program methodology that allows considering a year time horizon with hour resolution whilst significantly reducing the complexity of the optimization problem. The validity of the proposed technique is tested by considering a simple system that can be solved in a reasonable computational time without resorting to design days. Findings show that the proposed approach provides results in good agreement with the full-size optimization, allowing to correctly size the energy storage and operate the system with a long-term policy, while significantly simplifying the optimization problem
Pre-combustion CO2 capture
No full textThis paper, which is part of a special issue of the International Journal of Greenhouse Gas Control, gives an overview of the latest achievements in the pre-combustion decarbonisation route for the production of electricity with CO2 capture. Pre-combustion technologies applied to two different fuels are considered, natural gas and coal, since they cover most of electricity production from fossil fuels worldwide. The work first discusses in detail the different sections in which a power plant with pre-combustion CO2 capture can be divided. For each section, the available technologies with corresponding advantages and disadvantages are presented. Next, the plant lay-outs for natural gas and coal proposed in literature, including heat & mass balances and the economic assessment, are discussed. In general, research activity in pre-combustion decarbonisation for power production focused more on coal than on natural gas-based plant since in the latter case the plant complexity and costs are not competitive with post-combustion CO2 capture, which is a technology on the verge of commercialization. Finally the paper briefly discusses pre-combustion CO2 capture in industry especially those projects where CO2 is captured and stored or used for EOR
Predicting the ultimate potential of natural gas SOFC power cycles with CO2 capture – Part A: Methodology and reference cases
Full text linkDriven by the search for the highest theoretical efficiency, in the latest years several studies investigated the integration of high temperature fuel cells in natural gas fired power plants, where fuel cells are integrated with simple or modified Brayton cycles and/or with additional bottoming cycles, and CO2 can be separated via chemical or physical separation, oxy-combustion and cryogenic methods. Focusing on Solid Oxide Fuel Cells (SOFC) and following a comprehensive review and analysis of possible plant configurations, this work investigates their theoretical potential efficiency and proposes two ultra-high efficiency plant configurations based on advanced intermediate-temperature SOFCs integrated with a steam turbine or gas turbine cycle. The SOFC works at atmospheric or pressurized conditions and the resulting power plant exceeds 78% LHV efficiency without CO2 capture (as discussed in part A of the work) and 70% LHV efficiency with substantial CO2 capture (part B). The power plants are simulated at the 100 MW scale with a complete set of realistic assumptions about fuel cell (FC) performance, plant components and auxiliaries, presenting detailed energy and material balances together with a second law analysis
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