| 1. |
- Cuneo, A., et al.
(author)
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ECONOMICAL OPTIMIZATION OF A HYBRID SYSTEM GAS TURBINE SIZE WITH SOFC STACK DEGRADATION
- 2017
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In: EFC - Proc. Eur. Fuel Cell Piero Lunghi Conf.. - : ENEA. - 9788882863241 ; , s. 117-118
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Conference paper (peer-reviewed)abstract
- The coupling of a pressurized solid oxide fuel cell (SOFC) and a gas turbine has been proven to result in extremely high efficiency and reduced emissions. The presence of the gas turbine can improve system durability compared to a standalone SOFC, because the turbomachinery can supply additional power as the fuel cell degrades to meet the power request. Since performance degradation is an obstacles to SOFC systems commercialization, the optimization of the hybrid system to mitigate SOFC degradation effects is of great interest. In this work, an optimization approach was used to innovatively study the effect of gas turbine size on system durability for a 400 kW fuel cell stack. A larger turbine allowed a bigger reduction in SOFC power before replacing the stack, but increased the initial capital investment and decreased the initial turbine efficiency. Thus, the power ratio between SOFC and gas turbine significantly influenced system economic results.
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| 2. |
- Zaccaria, Valentina, 1989-, et al.
(author)
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Advanced gas turbine hybrid power systems to improve SOFC economic viability
- 2017
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In: Journal of the Global Power and Propulsion Society. - 2515-3080. ; 1, s. 28-40
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Journal article (peer-reviewed)abstract
- Coupling a solid oxide fuel cell (SOFC) with a gas turbineprovides a substantial increment in system efficiency comparedto the separate technologies, which can potentiallyintroduce economic benefits and favor an early market penetrationof fuel cells. Currently, the economic viability of suchsystems is limited by fuel cell short lifetime due to a progressiveperformance degradation that leads to cell failure.Mitigating these phenomena would have a significant impacton system economic feasibility. In this study, the lifetime of astandalone, atmospheric SOFC system was compared to apressurized SOFC gas turbine hybrid and an economic analysiswas performed. In both cases, the power production wasrequired to be constant over time, with significantly differentresults for the two systems in terms of fuel cell operating life,system efficiency, and economic return. In the hybrid system,an extended fuel cell lifetime is achieved while maintaininghigh system efficiency and improving economic performance.In this work, the optimal power density was determined forthe standalone fuel cell in order to have the best economicperformance. Nevertheless, the hybrid system showed bettereconomic performance, and it was less affected by the stackcost.
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| 3. |
- Zaccaria, Valentina, 1989-, et al.
(author)
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Conceptual Design of a 3-Shaft Turbofan Engine with Reduced Fuel Consumption for 2025
- 2017
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In: Energy Procedia. - : Elsevier BV. - 1876-6102.
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Conference paper (peer-reviewed)abstract
- In the past decade, aircraft fuel burn has been continually decreased, mainly by improving thermal and propulsion efficiencies with consequent decrement in specific fuel consumption. In view of future emission specifications, the requirements for SFC in the forthcoming years are expected to become more stringent. In this paper, a preliminary design of a turbofan engine for entry in service in 2025 was performed. The design of a baseline 2010 EIS engine was improved according to 2025 specifications. A thermodynamic analysis was carried out to select optimal jet velocity ratio, pressure ratio, and temperatures with the goal of minimizing specific fuel consumption. A gas path layout was generated and an aerodynamic analysis was performed to optimize the engine stage by stage design. The optimization resulted in a 3-shaft turbofan jet engine with a 21% increase in fan diameter, a 2.2% increment in engine length, and a fuel burn improvement of 11% compared to the baseline engine, mainly due to an increment in propulsive efficiency. A sensitivity analysis was also conducted to highlight what the focus of technology development should be.
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| 4. |
- Zaccaria, Valentina, 1989-, et al.
(author)
-
Fuel Cell Temperature Control with a Pre-Combustor in SOFC Gas Turbine Hybrids during Load Changes
- 2017
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In: Journal of electrochemical energy conversion and storage. - : ASME International. - 2381-6872 .- 2381-6910. ; 14, s. 031006-031014
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Journal article (peer-reviewed)abstract
- The use of high temperature fuel cells, such as Solid Oxide Fuel Cells (SOFCs), for power generation is considered a very efficient and clean solution to conservation of energy resources. When the SOFC is coupled with a gas turbine, the global system efficiency can go beyond 70% on natural gas LHV. However, durability of the ceramic material and system operability can be significantly penalized by thermal stresses due to temperature fluctuations and non-even temperature distributions. Thermal management of the cell during load following is therefore essential.The purpose of this work was to develop and test a pre-combustor model for real-time applications in hardware-based simulations, and to implement a control strategy to keep constant cathode inlet temperature during different operative conditions. The real-time model of the pre-combustor was incorporated into the existing SOFC model and tested in a hybrid system facility, where a physical gas turbine and hardware components were coupled with a cyber-physical fuel cell for flexible, accurate, and cost-reduced simulations.The control of the fuel flow to the pre-combustor was proven to be effective in maintaining a constant cathode inlet temperature during a step change in fuel cell load. With a 20 A load variation, the maximum temperature deviation from the nominal value was below 0.3% (3K). Temperature gradients along the cell were maintained below 10 K/cm. An efficiency analysis was performed in order to evaluate the impact of the pre-combustor on the overall system efficiency.
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