Waste heat management of direct carbon fuel cell with advanced supercritical carbon dioxide power cycle – A thermodynamic-electrochemical modeling approach

Two combined cycle engine cascade concepts are presented in this paper. The first uses a traditional open loop gas turbine engine (Brayton cycle) with a combustor as the topping cycle and a series of supercritical carbon dioxide (S–CO2) engines as intermediate cycles and a bottoming cycle. A global optimization of the engine design parameters was conducted to maximize the combined efficiency of all of the engines. A combined cycle efficiency of 65.0% is predicted. The second combined cycle configuration utilizes a fuel cell inside of the topping cycle in addition to a combustor. The fuel cell utilizes methane fuel. The waste heat from the fuel cell is used to heat the high pressure air. A combustor is also used to burn the excess fuel not usable by the fuel cell. After being heated, the high pressure, high temperature air expands through a turbine to atmospheric pressure. The low pressure, intermediate temperature exhaust air is then used to power a cascade of supercritical carbon dioxide engines. A combined efficiency of 73.1% using the fuel lower heating value is predicted with this combined fuel cell and heat engine device. Details of thermodynamics as well as the (S–CO2) engines are given.

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Advanced Exergy Analysis of the Supercritical Carbon Dioxide Power Cycle for Waste Heat Recovery of Gas Turbine

10.1115/gt2021-59195 ◽

2021 ◽

Author(s):

Bo Li ◽

Shun-sen Wang ◽

Liming Song

Keyword(s):

Carbon Dioxide ◽

Supercritical Carbon Dioxide ◽

Gas Turbine ◽

Exergy Analysis ◽

Waste Heat ◽

Design Stage ◽

Exergy Destruction ◽

Technical Improvement ◽

Power Cycle ◽

Supercritical Carbon

Abstract In this paper, the supercritical carbon dioxide power cycle used to recover the waste heat of gas turbine is investigated by means of conventional exergy analysis and advanced exergy analysis. Firstly, the thermodynamic parameters of carbon dioxide cycle in design stage are determined by single-objective optimization with net power output as objective function. Then, conventional exergy analysis is carried out on the partial heating cycle under real, unavoidable and ideal conditions. After that, advanced exergy analysis, in which the exergy destruction is divided into endogenous / exogenous part and avoidable / unavoidable part is adopted to reveal the improvement potential of the system and illustrate the interaction among the components. According to the calculation results, a total amount of 3.55MW (47.33%) exergy destruction could be reduced by the improvement of component efficiency. Endogenous exergy destruction is higher than exogenous exergy destruction in all components. Based on the results of conventional exergy analysis, the high-temperature heater should be paid attention in order to reduce exergy destruction. However, according to the results of advanced exergy analysis, the technical improvement of turbine should be emphasized due to its high endogenous-avoidable exergy destruction. Meanwhile, for the components with high unavoidable exergy destruction, external systems should be employed to exploit the underutilized energy and enhance the system performance.

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Development of the Supercritical Carbon Dioxide Power Cycle Experimental Loop in KIER

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2016-57460 ◽

2016 ◽

Cited By ~ 8

Author(s):

Junhyun Cho ◽

Hyungki Shin ◽

Ho-Sang Ra ◽

Gilbong Lee ◽

Chulwoo Roh ◽

...

Keyword(s):

Carbon Dioxide ◽

Supercritical Carbon Dioxide ◽

High Speed ◽

Waste Heat ◽

Power Cycle ◽

Foil Bearings ◽

Radial Turbine ◽

Turbo Generator ◽

Test Loop ◽

Supercritical Carbon

Three supercritical carbon dioxide (CO2) power cycle experimental loops have been developed in Korea Institute of Energy Research (KIER) from 2013. As the first step, a 10 kWe-class simple un-recuperated Brayton power cycle experimental loop was designed and manufactured to test its feasibility. A 12.6 kWe hermetic turbine-alternator-compressor (TAC) unit which is composed of a centrifugal compressor, a radial turbine and the gas foil bearings was manufactured. The turbine inlet design temperature and pressure were 180 °C and 130 bar, respectively. Preliminary operation was successful at 30,000 RPM which all states of the cycle existed in the supercritical region. Second, a multi-purpose 1 kW-class test loop which operates as a transcritical cycle at a temperature of 200 °C was developed to concentrate on the characteristics of the cycle, control and stability issues of the cycle. A high-speed turbo-generator was developed which is composed of a radial turbine with a partial admission nozzle and the commercial oil-lubricated angular contact ball bearings. Finally, a 60 kWe-class Brayton cycle is being developed which is composed of two turbines and one compressor to utilize flue-gas waste heat. As the first phase of development, a turbo-generator which is composed of an axial turbine, a mechanical seal and the oil-lubricated tilting-pad bearings was designed and manufactured.

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