Regenerative fuel cell

Besides chemical catalytic reduction of carbon dioxide with hydrogen, which is already possible in the laboratory, we are exploring a new approach to recycling carbon dioxide into methyl alcohol or related oxygenates via aqueous eleetrocatalytic reduction using what can be called a regenerative fuel cell system. The direct methanol fuel cell... 

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. 

Fig. 28. Cycle of 34-ceU regenerative hydrogen—oxygen fuel cell where A represents the charging region at 10 A, B represents discharging at 18.2 A. Both (—) voltage and (—) pressure changes are shown. To convert MPa to psig, multiply by 145.

Chen GY, Delafuente DA, Sarangapani S, Mallouk TE. 2001. Combinatorial discovery of bifunctional oxygen reduction-water oxidation electrocatalysts for regenerative fuel cells. Catal Today 67 341-355. 

GM also announced the expansion of fuel cell development activity with Giner, Inc., to include applications beyond the transportation field, including hydrogen generation for refueling systems and regenerative fuel cells for stationary power. GM s fuel cell stack set a new world standard for power density that packed 60% more power. The new stack generated 1.75 kilowatts (kW) per liter. 

The Peugeot Quark ATV uses an air-cooled fuel cell with a 40 cell nickel metal hydride battery. The 9 liter hydrogen tank can be pressurized to 10,150 psi for a range of up to 80 miles. The tank is designed to be exchanged for a full one when empty. Each 17 inch wheel has its own electric motor that can produce 74 pound-feet of torque. The motors also supply regenerative braking. 

Figure. 11. Schematic of a Regenerative Fuel Cell System...

Mitlitsky, E, Myers, B. and Weisberg, A. H. (1998) Regenerative fuel cell systems. Energy Fuels, 12, 56-71. 

Figure 9-13. Regenerative Brayton Cycle Fuel Cell Power System... 

Table 9-23. Performance Calculations for a Pressurized, High Temperature Fuel Cell (SOFC) with a Regenerative Brayton Bottoming Cycle Approach Delta T=30F... 

The results of the performance calculations are summarized in Table 9-24. The efficiency of the overall power system, work output divided by the lower heating value (LHV) of the CH4 fuel, is increased from 57% for the fuel cell alone to 82% for the overall system with a 30 F difference in the recuperative exchanger and to 76% for an 80 F difference. This regenerative Brayton cycle heat rejection and heat-fuel recovery arrangement is perhaps the simplest approach to heat recovery. It makes minimal demands on fuel cell heat removal and gas turbine arrangements, has minimal number of system components, and makes the most of the inherent high efficiency of the fuel cell. 

The results of the performance calculations for the fuel cell, Rankine cycle heat recovery system, summarized in Table 9-24, indicate that the efficiency of the overall system is increased from 57% for the fuel cell alone to 72% for the overall system. This Rankine cycle heat-fuel recovery arrangement is less complex but less efficient than the combined Brayton-Rankine cycle approach, and more complex and less efficient than the regenerative Brayton approach. It does, however, eliminate the requirement for a large, high temperature gas to gas heat exchanger. And in applications where cogeneration and the supply of heat is desired, it provides a source of steam. 

The effectiveness of the regenerative Brayton cycle performance will depend on the efficiency of the fuel cell, compressor, and turbine units the pressure loss of gases flowing through the system the approach temperatures reached in the recuperative exchanger and, most importantly, the cost of the overall system. 

J. Pettersson, B. Ramsey, and D. Harrison. A review of the latest developments in electrodes for unitized regenerative polymer electrolyte fuel cells. Journal of Power Sources 157 (2006) 28-34. 

Chaurasia, P.B.L., Ando, Y., Tanaka, T. 2003. Regenerative fuel cell with chemical reactions. Energy Convers Manage 44 611-628. 

Chicago/Vancouver Demo 1 st fleet demonstration program 205 kW Ballard fuel cell engine with regenerative braking. 

Several types of fuel cell are currently under development, using different electrolyte systems phosphoric acid (PAFC), alkaline, molten carbonate (MCFC), regenerative, zinc-air, protonic ceramic, (PCFC), proton exchange membrane (PEM), direct methanol (DMFC), and solid oxide (SOFC). The last four contain solid electrolytes. 

The oxygen anode (in the regenerative mode) as a metal oxide is also able to work in the oxidic form as hydrogen anode (in the fuel cell mode). 

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