Catalytic combustion of 1-butanol coupled with heat harvesting for compact power

A combustor paired with a heat-harvesting device, such as a thermoelectric or thermal photovoltaic device, can utilize high energy-dense liquid fuels while avoiding direct chemical-to-electrical conversion issues such as electrode and electrolyte poisoning. Therefore, the system is an attractive alternative to batteries and fuel cells for portable power applications. In the current study, a 1-butanol fed catalytic combustor using a Rh/Al₂O₃ catalyst was tested with a heat extractor, in this case being a stainless steel rod with a copper heat sink that was designed to thermally mimic a small thermoelectric module. The effects of residence time, fuel flow rate, and rod size on reactor/extractor temperatures and the energy balance were observed. Fuel-lean equivalence ratios were also studied and shown to have little effect on performance. Residence time does not have a direct effect; however, it does provide a catalytic stability limit for the fuel flow rate. The difference in the hot and cold side temperatures of the rod is dependent on the fuel flow rate and length of the rod. The greatest difference observed in these temperatures was 513 °C using the long-sized (15 cm) rod. The percentage of fuel energy conducted through the rod is only dependent on the rod size, with a maximum around 40% using the short rod. These results provide important design guidelines for the catalytic combustion of energy-dense liquid fuels as an excellent alternative heat source for either direct use or electrical power conversion.