Hybrid Fuel Cell Gas Turbine System Design and Optimization

Author(s):  
Dustin McLarty ◽  
Jack Brouwer ◽  
Scott Samuelsen

Ultrahigh efficiency, ultralow emission fuel cell gas turbine (FC/GT) hybrid technology represents a significant breakthrough in electric power generation. FC/GT hybrid designs are potentially fuel flexible, dynamically responsive, scalable, low-emission generators. The current work develops a library of dynamic component models and system design tools that are used to conceptualize and evaluate hybrid cycle configurations. The physical models developed for the design analysis are capable of off-design simulation, perturbation analysis, dispatch evaluation, and control development. A parametric variation of seven fundamental design parameters provides insights into design and development requirements of FC/GT hybrids. As the primary generator in most configurations, the FC design choices dominate the system performance, but the optimal design space may be substantially different from a stand-alone FC system. FC operating voltage, fuel utilization, and balance of plant component sizing has large impacts on cost, performance, and functionality. Analysis shows that hybridization of existing fuel cell and gas turbine technology can approach 75% fuel-to-electricity conversion efficiency.

Author(s):  
Dustin McLarty ◽  
Scott Samuelsen ◽  
Jack Brouwer

Fuel Cell–Gas Turbine (FC-GT) hybrid technology portends a significant breakthrough in electrical generation. Hybrid systems reach unprecedented high efficiencies, above 70% LHV in some instances, with little to no pollution, and great scalability. This work investigates two high temperature fuel cell types with potential for hybrid application ranging from distributed generation to central plant scales; sub MW to 100MW. A new library of dynamic model components was developed and used to conceptualize and test several hybrid cycle configurations. This paper outlines a methodology for optimal scaling of balance of plant components used in any particular hybrid system configuration to meet specified design conditions. The optimization strategy is constrained to meet component performance limitations and incorporates dynamic testing and controllability analysis. This study investigates seven different design parameters and confirms that systems requiring less cathode recirculation and producing a greater portion of the total power in the fuel cell achieve higher efficiencies. Design choices that develop operation of the fuel cell at higher voltages increase efficiency, often at the cost of lower power density and greater stack size and cost. This work finds existing SOFC technology can be integrated with existing gas turbine and steam turbine technology in a hybrid system approaching 75% fuel to electricity conversion efficiency in optimized FC-GT hybrid configurations.


Author(s):  
Ji Ho Ahn ◽  
Tong Seop Kim

Owing to the increasing consumption of fossil fuels and emission of greenhouse gases, interests in highly efficient and low carbon emitting power systems are growing fast. Several research groups have been suggesting advanced systems based on fuel cells and have also been applying carbon capture and storage technology to satisfy the demand for clean energy. In this study, the performance of a hybrid system, which is a combination of a molten carbonate fuel cell (MCFC) with oxy-combustion carbon capture and an indirectly fired micro gas turbine (MGT) was predicted. A 2.5MW MCFC system that is used in commercial applications was used as the reference system so that the results of the study could be applicable to practical situations. The ambient pressure type hybrid system was modeled by referring to the design parameters of an MGT that is currently being developed. A semi-closed type design characterized by flow recirculation was adopted for this hybrid system. A part of the recirculating gas is converted into liquefied carbon dioxide and captured for storage at the carbon separation unit. Almost 100% carbon dioxide capture is possible with this system. In these systems, the output power of the fuel cell is larger than in the normal hybrid system without carbon capture because the partial pressure of carbon dioxide increases. The increased cell power partially compensates for the power loss due to the carbon capture and MGT power reduction. The dependence of net system efficiency of the oxy-hybrid on compressor pressure ratio is marginal, especially beyond an optimal value.


2014 ◽  
Vol 257 ◽  
pp. 412-420 ◽  
Author(s):  
Dustin McLarty ◽  
Jack Brouwer ◽  
Scott Samuelsen

Author(s):  
Ji Ho Ahn ◽  
Tong Seop Kim

Owing to the increasing consumption of fossil fuels and emission of greenhouse gases, interests in highly efficient and low carbon emitting power systems are growing fast. Several research groups have been suggesting advanced systems based on fuel cells and have also been applying carbon capture and storage technology to satisfy the demand for clean energy. In this study, the performance of a hybrid system, which is a combination of a molten carbonate fuel cell (MCFC) with oxy-combustion carbon capture and an indirectly fired micro gas turbine (MGT), was predicted. A 2.5 MW MCFC system that is used in commercial applications was used as the reference system so that the results of the study could be applied to practical situations. The ambient pressure type hybrid system was modeled by referring to the design parameters of an MGT that is currently being developed. A semi-closed type design characterized by flow recirculation was adopted for this hybrid system. A part of the recirculating gas is converted into liquefied carbon dioxide and captured for storage at the carbon separation unit (CSU). Almost 100% carbon dioxide capture is possible with this system. In these systems, the output power of the fuel cell is larger than in the normal hybrid system without carbon capture because the partial pressure of carbon dioxide increases. The increased cell power partially compensates for the power loss due to the carbon capture and MGT power reduction. The dependence of net system efficiency of the oxy-hybrid on compressor pressure ratio is marginal, especially beyond an optimal value.


2014 ◽  
Vol 254 ◽  
pp. 126-136 ◽  
Author(s):  
Dustin McLarty ◽  
Jack Brouwer ◽  
Scott Samuelsen

2005 ◽  
Vol 2 (4) ◽  
pp. 268-273 ◽  
Author(s):  
Rainer Kurz

A thermodynamic model for a gas turbine-fuel cell hybrid is created and described in the paper. The effects of gas turbine design parameters such as compressor pressure ratio, compressor efficiency, turbine efficiency, and mass flow are considered. The model allows to simulate the effects of fuel cell design parameters such as operating temperature, pressure, fuel utilization, and current density on the cycle efficiency. This paper discusses, based on a parametric study, optimum design parameters for a hybrid gas turbine. Because it is desirable to use existing gas turbine designs for the hybrids, the requirements for this hybridization are considered. Based on performance data for a typical 1600hp industrial single shaft gas turbine, a model to predict the off-design performance is developed. In the paper, two complementary studies are performed: The first study attempts to determine the range of cycle parameters that will lead to a reasonable cycle efficiency. Next, an existing gas turbine, that fits into the previously established range of parameters, will be studied in more detail. Conclusions from this paper include the feasibility of using existing gas turbine designs for the proposed cycle.


2003 ◽  
Author(s):  
Dawson A. Plummer ◽  
Comas Haynes ◽  
William Wepfer

Solid oxide fuel cell (SOFC) technology incorporates electrochemical reactions that generate electricity and high quality heat. The coupling of this technology with gas turbine bottoming cycles, to form hybrid power systems, leads to high efficiency levels. The purpose of this study is to conceptually integrate the hybrid power system with existing and imminent coal gasification technologies through computer simulation. The gasification technologies considered for integration include the Kellogg Brown Root (KBR) Transport Reactor and Entrained Coal Gasification. Parametric studies were performed to assess the effect of changes in pertinent fuel cell stack process settings such as operating voltage, inverse equivalence ratio and fuel utilization will be varied. Power output, system efficiency and costs are the chosen dependent variables of interest. Coal gasification data and a proven SOFC model program are used to test the theoretical integration. Feasibility and economic comparisons between the new integrated system and existing conventional systems are also made.


Author(s):  
David N. Rocheleau ◽  
John F. Sagona

To integrate a fuel cell into a vehicle platform many subsystems must be engineered to support the electrical power production of the fuel cell plant. These subsystems include the control of fuel and air supply as well as managing thermal and water throughput in the fuel cell stack. For the fuel cell plant to operate at optimum performance, one must examine the individual components that make up the “balance of plant” of the fuel cell system. Specifically, the power used to run the system must be scrutinized with the power produced by the system. Knowing how individual balance of plant components perform is the first step in design and optimization studies, as well as automated control system development. To address these issues, this paper examines how balance of plant components and subsystems affect parasitic power consumption, fuel cell power production, membrane hydration, hydrogen usage, and water production.


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