An experimental investigation of a micro-tubular SOFC membrane-separated liquid desiccant dehumidification and cooling tri-generation system

This paper reports the results of experimental work carried out on a micro-tubular solid oxide fuel cell tri-generation systemthat uses the waste heat from the fuel cell for dehumidification and cooling though the integration of an open cycle liquid desiccant dehumidification and cooling system. The experimental results demonstrate regeneration of the potassium formate solution using the thermal output from the SOFC in the first of its kind tri-generation system. Optimisation has shown that a 2.2L.min-1 regenerator desiccant volumetric flow facilitates best performance.When integrated with the micro-SOFC, the open cycle desiccant system demonstrates a COP of approaching 0.7, an encouraging value for a waste heat driven cooling system of this capacity. A tri-generation performance analysis is presented which serves to demonstrate the novel system operating in a building. The system achieved an electrical efficiency of 11% and regeneration efficiency of approximately 37%. The electrical efficiency is lower than that predicted by the company supplying the micro-tubular SOFC, because the unit suffered sulphur poisoning during preliminary tests. The electrical power output decreased from 250W to 150W, which reduced the electrical efficiency from around 18% to 11% and the overall efficiency from approximately 45% to just over 37%. Low temperature (33-36°C) regeneration was demonstrated

Annealing behaviour of Pt and PtNi nanowires for proton exchange membrane fuel cells

PtNi alloy and hybrid structures have shown impressive catalytic activities toward the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, such promise does not often translate into improved electrode performances in PEMFC devices. In this contribution, a Ni impregnation and subsequent annealing method, translatable to vertically aligned nanowire gas diffusion electrodes (GDEs), is shown in thin-film rotating disk electrode measurements (TFRDE) to enhance the ORR mass activity of Pt nanowires (NWs) supported on carbon (Pt NWs/C) by around 1.78 times. Physical characterisation results indicate that this improvement can be attributed to a combination of Ni alloying of the nanowires with retention of the morphology, while demonstrating that Ni can also help improve the thermal stability of Pt NWs. These catalysts are then tested in single PEMFCs. Lower power performances are achieved for PtNi NWs/C than Pt NWs/C. A further investigation confirms the different surface behaviour between Pt NWs and PtNi NWs when in contact with electrolyte ionomer in the electrodes in PEMFC operation. Indications are that this interaction exacerbates reactant mass transport limitations not seen with TFRDE measurements

Temperature-controlled growth of single-crystal Pt nanowire arrays for high performance catalyst electrodes in polymer electrolyte fuel cells

AbstractThe anisotropic structure and unique surface properties of one-dimensional (1D) Pt-nanowire (PtNW) make it a promising new type of electrocatalyst for various catalyst applications, especially for fuel cells. However, due to the critical synthesis process, a finely tuning of the synthesis temperature for precisely controlling the morphology and distribution of PtNWs in catalyst electrodes still remains a grand challenge. In this work, we present the temperature-controlled growth of PtNWs with large-area 16cm2 carbon paper piece as a direct support. The relationship between the growth temperature and PtNW behavior is studied by physical characterization, and their catalytic activity is measured towards oxygen reduction reaction (ORR) by testing as the cathode in a hydrogen-air fuel cell. The results show that the growth temperature plays a vital role on the behavior of PtNWs thus influencing their properties. The catalyst electrode with PtNWs grown at 40°C shows the best power performance. A possible mechanism for the influence of temperature on PtNW growth is suggested. The comparison with the state-of-the-art commercial TKK catalyst also shows a better performance and durability. The understanding gained in our work from PtNW catalyst electrode could aid in the design of other novel nanostructures in practical applications