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Abstract:
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In this thesis I used measured data from Humboldt State University’s hydrogen fueling
station, and ideal gas thermodynamic models, to calculate the specific energy (kWh/kg)
and 2nd Law efficiency for a hydrogen compressor. I used adiabatic, isothermal, and polytropic
thermodynamic models and found that the measured specific energy was substantially greater than that predicted using the models. The measured specific energy was approximately 8 kWh/kg compared to 1-1.5 kWh/kg for the thermodynamic models. The 2nd Law efficiencies for the models varied from approximately 17% relative to the adiabatic model to approximately 11% relative to the polytropic model. I speculate that the
large discrepancy between the measured and calculated specific energies, and the low efficiencies, is due to the details of the process the compressor uses to compress gas; it is not well modeled by an ideal gas process. I propose a preliminary model that more accurately
represents the compressor’s operation, based on the Bernoulli equation for fluid flow. While collecting data for this analysis, my colleagues and I noticed that the power used by the compressor varies depending on the time of day. We speculated that this was caused by variation in the incoming line voltages for the compressor. I monitored the line voltages for ten days and found that they do vary depending on the time of day. The compressor power variation is correlated with that of the line voltage. |
