Browsing by Author "Chouhan, Ashish"
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Item Electrochemical compression: performance evaluation and the role of back-diffusion(University of Delaware, 2021) Chouhan, AshishHydrogen offers the potential to decarbonize the automotive and stationary power sectors and is therefore expected to play an increasingly significant role in meeting global energy demand. Despite its high gravimetric energy density, hydrogen possesses very low volumetric energy density, and hence, it is important to find methods to efficiently store hydrogen in order to grow the hydrogen economy. Storing hydrogen as a compressed gas could be achieved by electrochemical compression (ECC), which is a membrane-based alternative to conventional mechanical compressors. ECC can be superior to mechanical compressors because of its higher efficiency, lack of moving parts, and noiseless operation. ☐ First, we investigate the performance of a single hydrogen electrochemical compressor cell in this study. In particular, detailed experiments have been conducted to study the detrimental effect of back-diffusion. These results have allowed us to propose a theoretical formulation for the ECC process incorporating back-diffusion and validate it by experiments. A robust definition for ECC efficiency that properly accounts for back diffusion is also proposed. Next, we turn our attention to practical systems that employ multiple cells in a stack configuration to achieve higher flowrates and gas pressures. Here, we analyze two different stack configurations - electrically in series/flow in parallel (ESFP) and electrically in series/flow in series (ESFS) - in order to understand their influence on gas throughput and exit pressure in the presence of back-diffusion. A theoretical performance analysis has been conducted for both configurations to gain insights into the compressed gas flux, pressure rise, back diffusion, and efficiency. Furthermore, a novel hybrid configuration that combines the features of both configurations is proposed that can optimize both flow and pressure for a given application. ☐ Finally, we study the application of ECC to environmentally friendly refrigerants like ammonia. We explore the ECC of ammonia using hydrogen as a carrier gas. Experimental results on the performance of an ECC operated on ammonia-hydrogen blends indicate that the back-diffusion of ammonia through the perfluorosulfonic acid membrane poses an even greater challenge, and we provide recommendations to facilitate the ECC of ammonia-hydrogen blends.Item Electrochemical gas separation and inerting system(Journal of Power Sources, 2021-05-15) Aryal, Utsav Raj; Chouhan, Ashish; Darling, Robert; Yang, Zhiwei; Perry, Mike L.; Prasad, Ajay K.Following the TWA 800 flight disaster in 1996 which was attributed to an explosion in the fuel tank, inerting of the ullage (air volume above the fuel in the tank) has gained prominence. Fuel tank inerting is the process of reducing the flammability of the ullage by supplying it with an inert gas like nitrogen. Current inerting techniques are expensive, consume large amounts of energy, and fail prematurely. Here, we propose a novel in-flight electrochemical gas separation and inerting system (EGSIS) to produce and supply nitrogen-enriched air (NEA). EGSIS combines a polymer electrolyte membrane (PEM) fuel cell cathode with a PEM electrolyzer anode to generate humidified NEA as the cathode output which can be dehumidified and supplied directly to the fuel tank. The required rate of NEA varies during a typical flight and a major advantage of EGSIS is that the rate of NEA generation can be conveniently controlled by varying the voltage applied to the system. Here, we report on the performance of a single-cell EGSIS apparatus and evaluate its suitability for aircraft fuel tank inerting.