Reversible fuel cell systems

Milliken, C.E. and Ruhl, R.C., Low-Cost High-Efficiency, Reversible Fuel Cell System, paper presented at Proceedings of the 2002 U.S. DOE Hydrogen Program Review, NREL/CP-610-32405. 

A different approach is to reconsider the airship as a means of air travel. A first approach to this is considering an airship for high-altitude cruising (or as a stratospheric platform) powered by photovoltaic panels and using a reversible fuel cell system to store surplus solar power and use it when the sim is not visible. In this way, carrying possibly heavy batteries may be avoided. The envisaged relative shares of direct use of solar power, of elec-trolyser operation and of fuel cell power production are shown in Fig. 4.12. So far, testing of the equipment sketched in Fig. 4.12 has been performed on a 1-kW scale in the laboratory and in simulated airship conditions. 

Reversible fuel cells—systems that can be switched between producing electricity from the cold combustion of hydrogen and oxygen and splitting water again into hydrogen and oxygen by electrolysis—were first devel-... 

II.D.5 Low Cost, High Efficiency Reversible Fuel Cell Systems... 

Patent for reversible fuel cell system to compensate peak load in an electric grid. 

A regenerative fuel cell system can also be a single electrochemical cell in which both the oxidation of fuels (i.e., production of electric power) and reduction of CO2 (to obtain fuels) can be carried out by simply reversing the mode of operation. 

Comprehensive discussions of fuel cells and Camot engines Nemst law analytical fuel cell modeling reversible losses and Nemst loss and irreversible losses, multistage oxidation, and equipartition of driving forces. Includes new developments and applications of fuel cells in trigeneration systems coal/biomass fuel cell systems indirect carbon fuel cells and direct carbon fuel cells. 

Fig. 2.1 The reversible fuel cell, its energy balance and its system boundary.

Fig. 2.12 The reversible fuel cell -U heat engine hybrid system.

The one area where oxyhydrogen combustion is desirable is where high flame temperatures are required, such as in welding. In all other applications the most efficient system is to use fuel cells and the least expensive configuration is to use my new reversible fuel cell design (Section 1.3.5.4), which can operate both in the electrolyzer and the fuel cell modes and uses free solar energy to drive the electrolyzer. 

Intrinsic tests were performed on the electrolyser and fuel cell of the test bench system for their characterisation (electrical and thermal behaviour, Faraday efficiency, gas purity). Additionally simulations were performed using the Matlab/Simulink software in order to develop a numerical model for such a kind of reversible fuel cell . The system storage efficiency was estimated at 40-42%. 

Electricity is very expensive to store, so it is generated as needed. Hydrogen is somewhat easier to store and, as discussed elsewhere in this report, hydrogen could be used in conjunction with the electric system as backup storage, so that hydrogen would be generated at times of ample power in a reversible fuel cell and reconverted as needed (see Chapter 8 and Appendix G in this report). 

Figure 3.3. Reaction mechanisms for water splitting (upward arrows) or the reverse power-producing reaction (downward arrows), proposed for organic photosystem II (a) and for morganic electrolysers and fuel cell systems (b). Charges are omitted in the figure, but discussed in the text (Sorensen, 2004e).

Figure 4.12. Power modes and their time-shares for reversible fuel cell (RFC) plus solar cell system proposed as a power source for a stratospheric airship. (From K. Eguchi, T. Fujihara, N. Shinozaki, S. Oka-ya (2004). Current work on solar RFC technology for SPF airship. In Proc. 15 World Hydrogen Energy Conf., Yokohama. 30A-07, CD Rom. Copyright attributed to the Hydrogen Energy Soc. Japan.)...

Figure 5.3. Layout of a decentralised, building-integrated hydrogen and fuel cell system based on intermittent primary power sources (such as wind or solar energy), reversible fuel cells and local stores, including stationary and maybe vehicle-based stores, and possibly capable of interchanging hydrogen with users in other buildings through pipelines (Sorensen, 2002a).

The MCFC because of its high operating temperature has higher efficiency (>50%o) and faster electrode kinetics than any other fuel cell system.At 650° C, almost a theoretical reversible potential is established at the interface with low electrode overpotentials, which does not require any noble metal catalysts. The CO does not poison the anode, because in the MCFC it is oxidized at the anode interface. 

In 1839 in Paris, nineteen year old experimenter Edmund Becquerel discovered the photovoltaic effect when he found that certain materials would produce electricity when exposed to light. In that same year William Grove experimented with reversing the process of electrolysis and invented the first gas battery or fuel cell. In the 21st century, these three discoveries converge in photovoltaic fuel cell system technology. 

The Technology Management, Inc. (TMI) reversible (fuel cell - electrolyzer) system employs a high temperature solid-oxide based electrochemical process to produce either electricity from common hydrocarbon fuels (e.g., natural gas, propane, and... 

A prototype of a CamCorder equipped with a PEM fuel cell system made of a stack of 15 bipolar plates, as shown in Figure 8-15, was developed to deliver 9 W output power at 8 V. The stack described above was integrated into a housing which also includes the metal hydride reversible hydrogen storage, pressure control, fans, and electronics. This system replaces the Li-ion battery pack normally used as an energy source in the camera. 

In any fuel cell system, the chemical energy of the reactants is converted directly into electrical energy. Thereby, the Gibbs free energy A G is related to the reversible cell potential ... 

As the anion-exchange membrane fuel cell is the alkaline-based system, we can use non-platinum-based catalyst. This is a big advantage to lower the cost of fuel cells. Especially perovskite-type and pyrochlore-type oxides have high performance to oxygen-electrocatalysts which could be applicable to the cathode materials. Some oxides have also bifunctional activities as oxygen electrode catalyst to produce a reversible fuel cell thus, future deployment is expected. While, the big problems are stability of the base... 

The AFC was one of the first modem fuel cells to be developed, beginning in 1960. The application at that time was to provide on-board electric power for the Apollo space vehicle. The AFC has enjoyed considerable success in space applications, but its terrestrial application has been challenged by its sensitivity to CO2. Still, some developers in the U S. and Europe pursue AFC for mobile and closed-system (reversible fuel cell) applications. 

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