Coproduction with Molten Carbonate Fuel Cells

Abstract

The concept of coproduction has been explored in combined heat and power applications. It is a method of improving the efficiency of the energy generating system by utilising waste heat. In the coming years hydrogen is expected to play an important role in decarbonization as it does not emit greenhouse gas at the point of application. Hydrogen today is primarily generated from fossil fuels and the processes of producing hydrogen are energy intensive, while also emitting large quantities of greenhouse gases into the atmosphere. As the amount of hydrogen generated today is limited, it has restricted the growth of industries such as the automobile industries producing fuel cell vehicles that are to use hydrogen as fuel. In this thesis report a coproduction concept using high temperature molten carbonate fuel cell has been examined. The molten carbonate fuel cells operate at very high temperature, and it is possible to utilise the waste heat for internal reforming reaction of a fuel such as natural gas to liberate hydrogen required by the fuel cell. Excess hydrogen can also be produced from such fuel cell systems when the fuel utilisation in the fuel cell is reduced. This concept has been studied with solid oxide fuel cells and a paper published in 2008 by Hemmes et al. titled "Flexible Coproduction of Hydrogen and Power Using Internal Reforming Solid Oxide Fuel Cells System" has served as the inspiration for this thesis report. Three modes of operations have been simulated in this thesis on the Cycle-Tempo software with varying fuel utilisations, similar to what has been shown with the solid oxide fuel cells in that paper. With molten carbonate fuel cells, overall efficiency of up to 80% was obtained in terms of electricity and hydrogen coproduction. By doing so it is also possible to produce overall power output of nearly three times than what can be achieved by conventional electricity production. The results obtained have also been compared with the solid oxide fuel cells in this report. While high coproduction efficiencies for flexibly coproducing hydrogen and power have been shown to be possible, other factors would also play important roles in the success of this technology. In this report some of those factors such as the status and expected growth of the hydrogen market, molten carbonate fuel cell market, role of actors, role of policy makers have also been examined. As this technology does rely on a fossil fuel that is natural gas, the benefits of using natural gas in hydrogen production has also been highlighted along with the positive effects these systems could have on the society.