Development of a Hydrogen Producing Thermal Control for Chemical Hydrogen Storage
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Authors
St. John, Adam
Date
2007-12-13T20:28:39Z
Type
thesis
Language
eng
Keyword
Hydrogen storage , thermal control , efficient , reactor
Alternative Title
Abstract
This thesis investigated a potential improvement to hydrogen storage for fuel cells using a thermally efficient hydrogen storage method. The efficiency of the storage
system was improved using a metal hydride system to act as a thermal control unit for an exothermic chemical hydrogen storage system.
A cylindrical shaped “hybrid” reactor was created to allow hydrogen production
from a sodium borohydride packed bed reactor and the metal hydride. Additionally, a custom built pressure-composition-temperature apparatus was built to record the amount
of hydrogen desorption from the metal hydride while isolating the metal from potential
poisons such as oxygen.
Before using the chemical hydride packed bed, heat transfer through the reactor was studied using circulating water. The water experiments showed that an increase in
heat flux to the reactor led to a faster desorption rate of hydrogen from the metal hydride resulting in a larger temperature drop throughout the reactor.
After the operating characteristics of the hybrid reactor were studied, a 10 wt%
solution of sodium borohydride was created and pumped through the packed bed to
produce enough hydrogen for a 300 W fuel cell. The amount of heat produced from the
packed bed portion of the reactor was significant, but temperatures levelled to around 80 °C. As expected, temperature control was directly proportional to the rate of hydrogen release from the metal hydride. On average, approximately 10% of the available heat energy was transferred to the metal hydride, and the hybrid reactor operated with gravimetric and volumetric energy densities of 0.27 kWh·kg-1 and 1.29 kWh·L-1 respectively. If the hybrid reactor is used solely to control peak temperatures, the amount of metal hydride necessary for thermal control could be decreased. Additionally, improvements in heat transfer as well as the hydrogen storage materials themselves would increase the energy density values further.
When compared to other energy storage devices, the hybrid reactor without
improvements is competitive as a backup power generator due to its silent operation and
large volumetric energy density. Since the hybrid reactor can provide quiet and cool
energy storage in a relatively small volume, it may become an effective and efficient
means for hydrogen storage with limited improvements.
Description
Thesis (Master, Mining Engineering) -- Queen's University, 2007-12-06 14:45:56.551
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