Fuel utilization effects on system efficiency in solid oxide fuel cell gas turbine hybrid systems

Abstract

A computational analysis was conducted to optimize the design of a solid oxide fuel cell-gas turbine hybrid power generator, focusing on the impact that fuel utilization within the fuel cell has on system efficiency and installed costs. This is the first ever design-study considering the effect of fuel utilization on performance, as well as on the optimum power split. This hybrid system attained high electric generation efficiencies (>70%) over a wide range of operating conditions (60% < fuel utilization < 90%) while the fuel cell stack size decreased in proportion to decreasing the fuel utilization. A one-dimensional fuel cell model was used to simulate the fuel cell while GateCycle® was used to simulate the performance of the associated recuperated turbine and various subsystems necessary for thermal management. For each test case, the size of the solid oxide fuel cell, gas turbine, and recuperator, as well as the fuel and air flow rates, hot-air bypass set point, and heat exchange effectiveness in the solid oxide fuel cell manifold were varied to obtain 550 MWe output. In addition, anode recycle, turbomachinery efficiency, and various thermal management options were tested. The maximum system efficiency (75.6%) was attained for the single-pass solid oxide fuel cell with highly efficient turbomachinery when the solid oxide fuel cell used 80% of the incoming fuel. Efficiency was essentially flat from 75% fuel utilization through 85% fuel utilization. Employing anode recycle starting at 65% resulted in roughly 1 percentage point efficiency decrease for each percent increase in fuel utilization. For minimized solid oxide fuel cell degradation, a near 50:50 power split case was studied resulting in 68.6% efficiency and the solid oxide fuel cell using 55% of the incoming fuel. Because of shifting half of the power generation to the gas turbine, the size of the fuel cell stack was reduced by 25% as compared to that at maximum efficiency (80% fuel utilization).

Coupling effects of fuel reforming process and fuel utilization on the system performance of a natural gas solid oxide fuel cell/gas turbine hybrid system

“…The developed model showed good agreement with the Aspen Plus model, the maximum error was 1.33% for CH 4 composition. For the second approach, the reformer performance from the developed model was compared with Reference 29 as shown in Table 3 (18)(19)(20). As shown, both models showed good agreement with the maximum error of 3.34% for H 2 O conversion rate at 873 K and 100 kPa.…”

“…Lumped average values were used to represent cell temperature, current density, and U f in lumped models, which could be substantially different from a more realistic distributed model result. 20,23 U f is normally an assigned number in a lumped SOFC model. However, in a distributed model, U f is a localized phenomena across the fuel cell, which should be calculated based on different operating conditions of SOFC.…”

Computational Techniques Based on Artificial Intelligence for Extracting Optimal Parameters of PEMFCs: Survey and Insights

“…Depending on the electrolyte type, FCs are categorized and utilized in the market for different applications [1,2]. Examples of FC types are; (i) Proton exchange membrane FCs (PEMFCs) [7,8], (ii) Solid oxide FCs (SOFCs) [9,10], (iii) Molten carbonate FCs (MCFCs) [11], (iv) Phosphoric acid FCs (PAFCs) [8], (v) Alkaline FCs (AFCs) [12,13] and furthermore. Specifically, the basic characteristics of the latter-mentioned types are illustrated in Table 1.…”

Exergoeconomic and environmental optimisations of multigeneration biomass‐based solid oxide fuel cell systems with reduced CO 2 emissions

“…According to the results, the highest exergy destruction is associated with the engine. Oryshchyn et al 21 analysed the hydrogen utilisation factor for a combined SOFC and GT cycle. The results revealed that the highest possible efficiency for the cycle would reach 75.6%, while for achieving a minimum degradation for the SOFC stack, the efficiency would inevitably reduce by 7%.…”