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THE USE OF BIOMASS IN MOLTEN CARBONATE AND SOLID OXIDE DIRECT CARBON FUEL CELLS

Adeniyi, Olalekan David (2011) THE USE OF BIOMASS IN MOLTEN CARBONATE AND SOLID OXIDE DIRECT CARBON FUEL CELLS. PhD thesis, University of Sheffield.

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Abstract

A direct carbon fuel cell (DCFC) is a special type of high temperature fuel cell that uses solid carbon as fuel and air as oxidant. Researches in the area of the DCFC have focused on using fuel derived from petroleum products, coal and activated carbon but this current research investigates the use of biomass carbon fuel in a single cell DCFC. Six different biomasses were investigated (miscanthus, switchgrass, wheat, spruce, poplar and willow). The biomasses were subjected to pyrolysis reaction at 800oC, 7oC/min with particle sizes of 0.50 mm to 1.00 mm, yielding 25 wt.% biomass carbon. The two electrolyte systems investigated were; molten carbonate electrolyte direct carbon fuel cell (MCDCFC) and solid oxide electrolyte direct carbon fuel cell (SODCFC) and these were tested using hand and ball milled biomass carbon fuels (HM and BM). The overall electrochemical reactions of the biomass carbon fuels in the SODCFC were better than those of the MCDCFC. The BM biomass fuels performed better in the SODCFC while the HM biomass fuels performed better in the MCDCFC. In terms of the open circuit voltage, miscanthus fuel (1.24 V) had the best value for SODCFC while willow fuel (0.83 V) for MCDCFC. The best peak power density was recorded for miscanthus fuel (77.41 mW/cm2) in the SODCFC and willow fuel (18.48 mW/cm2) in the MCDCFC. Miscanthus fuel (180.52 mA/cm2) gave the maximum current density for the SODCFC while spruce fuel (73.02 mA/cm2) for the MCDCFC. For the current density at 80% voltage efficiency miscanthus fuel (100 mA/cm2) was superior for the SODCFC and willow fuel (6.67 mA/cm2) for MCDCFC. Miscanthus fuel (0.66 V) showed the highest voltage at peak power for the SODCFC and willow fuel (0.48 V) for the MCDCFC. The overall energy strategy considering two major routes of electricity generation from biomass were investigated. The first route is the burning of biomass in a power plant to generate 6.5 MJ of electricity and the second is the DCFC integrated route using biomass to generate 12.8 MJ of electricity. The DCFC integrated route gave superior outputs of energy generation with an overall conversion efficiency of 70% when compared with the 35% of the first route.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Chemical and Biological Engineering (Sheffield)
Depositing User: Olalekan David Adeniyi
Date Deposited: 16 Dec 2011 16:38
Last Modified: 08 Aug 2013 08:47
URI: http://etheses.whiterose.ac.uk/id/eprint/1964

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