Porous Metal Hydride (PMH) Compacts for Thermal Energy Applications

2009 ◽  
Author(s):  
Michael Lee ◽  
Il-Seok Park ◽  
Sunwoo Kim ◽  
Kwang J. Kim
Keyword(s):  
Thermal Conductivity ◽  
Heat Generation ◽  
Metal Hydride ◽  
Storage Systems ◽  
Metal Hydrides ◽  
Porous Metal ◽  
Rigid Wall ◽  
Ideal Gas ◽  
Energy Applications ◽  
Powder Type

Pelletized Porous Metal Hydride (PMH) was investigated in order to assess its thermal capability for energy storage/transfer applications. Metal hydrides have been known as promising materials for hydrogen storage systems, heat storage systems, and thermal devices, thanks to their nearly reversible reaction characteristics during the hydrogen absorbing and desorbing processes. The conventional powder-type metal hydrides however have a relatively low thermal conductivity, which is responsible for low heat generation. In the present study three representative metal hydrides, LaNi5, Ca0.6Mm0.4Ni5, and LaNi4.75Al0.25, metal hydride powders were coated with thin copper and pressed at 3,000 psig with metal additives in order to improve the thermal conductivity. This pelletizing process does not require the use of an organic binder and additional processes such as sintering under high pressure. The pelletized PMH compacts employing the copper coating exhibit higher thermal conductivity compared to raw metal hydride powders. However, pelletizing may deteriorate the permeability of the PMH compacts, lowering mass transfer of hydrogen. Therefore, the permeability must be observed to verify whether it meets the required level for suitable applications. Measurements were performed by varying copper fractions and plotted against the upstream/downstream pressure differential. Darcy’s equation in conjunction with an ideal gas assumption was used to calculate the permeability of a rigid wall design. This investigation reveals that rising copper content is accompanied with decreases in permeability. Permeability values for most samples tested in this study were found to be larger than the desirable level, 5 × 10−15 m2. Additionally, the thermal performance of the LaNi5 PMH compacts was tested by calculating and comparing the heat generation of the PMH pellets and powders filled reactors during the hydrogen absorption process in water bath medium.

The Thermodynamic Way of Assessing Reversible Metal Hydride Volume Expansion: Getting a Grip on Metal Hydride Formation Overpotential

2021 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Volume Change ◽  
Metal Hydride ◽  
Volume Expansion ◽  
Storage Systems ◽  
Metal Hydrides ◽  
Ideal Gas ◽  
Relative Volume ◽  
Hydride Formation ◽  
Chemical Hydrogen Storage ◽  
Insight Into

<p>The relative volume change of reversible metal hydrides upon hydrogenation is determined by means of the van’t Hoff reaction entropy and STP ideal gas parameters. This method allows insight into the requirements to metal hydride formation, outlined by example of Ti-NaAlH<sub>4</sub>. This work presents a timeless perspective on the sorbent phase thermodynamics of reversible chemical hydrogen storage systems.</p>

scholarly journals The Thermodynamic Way of Assessing Reversible Metal Hydride Volume Expansion: Getting a Grip on Metal Hydride Formation Overpotential

2021 ◽  
Author(s):  
Roland Hermann Pawelke
Keyword(s):  
Volume Change ◽  
Metal Hydride ◽  
Volume Expansion ◽  
Storage Systems ◽  
Metal Hydrides ◽  
Ideal Gas ◽  
Relative Volume ◽  
Hydride Formation ◽  
Chemical Hydrogen Storage ◽  
Insight Into

<p>The relative volume change of reversible metal hydrides upon hydrogenation is determined by means of the van’t Hoff reaction entropy and STP ideal gas parameters. This method allows insight into the requirements to metal hydride formation, outlined by example of Ti-NaAlH<sub>4</sub>. This work presents a timeless perspective on the sorbent phase thermodynamics of reversible chemical hydrogen storage systems.</p>

Performance of Thermal Enhancement Materials in High Pressure Metal Hydride Storage Systems

2008 ◽  
Author(s):  
Timothe´e L. Pourpoint ◽  
Aaron Sisto ◽  
Kyle C. Smith ◽  
Tyler G. Voskuilen ◽  
Milan K. Visaria ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Pressure ◽  
Metal Hydride ◽  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
Hydrogen Gas ◽  
Thermal Enhancement ◽  
Hydrogen Systems ◽  
Hydride Powder

Over the past two years, key issues associated with the development of realistic metal hydride storage systems have been identified and studied at Purdue University’s Hydrogen Systems Laboratory, part of the Energy Center at Discovery Park. Ongoing research projects are aimed at the demonstration of a prototype large-scale metal hydride tank that achieves fill and release rates compatible with current automotive use. The large-scale storage system is a prototype with multiple pressure vessels compatible with 350 bar operation. Tests are conducted at the Hydrogen Systems Lab in a 1000 ft2 laboratory space comprised of two test cells and a control room that has been upgraded for hydrogen service compatibility. The infrastructure and associated data acquisition and control systems allow for remote testing with several kilograms of high-pressure reversible metal hydride powder. Managing the large amount of heat generated during hydrogen loading directly affects the refueling time. However, the thermal management of hydride systems is problematic because of the low thermal conductivity of the metal hydrides (∼ 1 W/m-K). Current efforts are aimed at optimizing the filling-dependent thermal performance of the metal hydride storage system to minimize the refueling time of a practical system. Combined heat conduction within the metal hydride and the enhancing material particles, across the contacts of particles and within the hydrogen gas between non-contacted particles plays a critical role in dissipating heat to sustain high reaction rates during refueling. Methods to increase the effective thermal conductivity of metal hydride powders include using additives with substantially higher thermal conductivity such as aluminum, graphite, metal foams and carbon nanotubes. This paper presents the results of experimental studies in which various thermal enhancement materials are added to the metal hydride powder in an effort to maximize the effective thermal conductivity of the test bed. The size, aspect ratio, and intrinsic thermal conductivity of the enhancement materials are taken into account to adapt heat conduction models through composite nanoporous media. Thermal conductivity and density of the composite materials are measured and enhancement metrics are calculated to rate performance of composites. Experimental results of the hydriding process of thermally enhanced metal hydride powder are compared to un-enhanced metal hydride powder and to model predictions. The development of the Hydrogen Systems Laboratory is also discussed in light of the lessons learned in managing large quantities of metal hydride and high pressure hydrogen gas.

Investigation of a Solar-Thermal Bio-Mimetic Metal Hydride Actuator

Solar Energy ◽  
2002 ◽  
Author(s):  
George Lloyd ◽  
Kwang J. Kim ◽  
A. Razani ◽  
Mohsen Shahinpoor
Keyword(s):  
Metal Hydride ◽  
Response Times ◽  
Complete Solution ◽  
Porous Metal ◽  
Solar Thermal ◽  
Performance Bounds ◽  
Solar Thermal Energy ◽  
Energy Applications ◽  
Advantages And Disadvantages ◽  
Thermal Actuators

Metal hydrides have been investigated for use in a number of solar thermal energy applications, such as heat regenerators or hydrogen storage technology, but rarely for thermal actuators. Preliminary experimental results from a prototype solar thermal metal hydride actuator, using copper-encapsulated porous metal hydride compacts of LaNi5, indicate that this thermal-mechanical system can produce high specific forces (over 100 (N/g)), with response times on the order of seconds. These operational characteristics, along with features such as being bio-mimetic, compact, operationally safe, lubricationless, noiseless, soft actuating, and environmentally benign, result in an actuator that is ideal for many industrial, space, defense, and biomedical applications. In this paper, we report recent work directed toward predicting and characterizing the performance bounds of the actuator, specically concentrating on elements which might comprise an actuator driven by concentrated solar radiation. A complete solution of the 1D governing heat and mass transfer equations with an ideally selective reactor surface are used to predict bounds on performance in terms of volume flow rates and realistic actuation times. The advantages and disadvantages of the design are discussed from this perspective. The preliminary data show a great potential for these metal hydride actuators to be used for solar thermo-mechanical applications.

Transient Plane Source Method for Thermal Property Measurements of Metal Hydrides

2008 ◽  
Author(s):  
Scott Flueckiger ◽  
Yuan Zheng ◽  
Timothe´e Pourpoint
Keyword(s):  
Thermal Conductivity ◽  
Stainless Steel ◽  
Thermal Diffusivity ◽  
Hydrogen Storage ◽  
Thermal Property ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Flash Method ◽  
Plane Source ◽  
Transient Plane Source

Metal hydrides are promising hydrogen storage materials with potential for practical use in a passenger car. To be a viable hydrogen storage option, metal hydride heat transfer behavior must be well understood and accounted for. As such, the thermal properties of the metal hydride are measured and compiled to assess this behavior. These properties include thermal conductivity, specific heat, and thermal diffusivity. The transient plane source (TPS) method was selected primarily due to a high level of versatility, including customization for high pressure hydrogen environments. To perform this measurement, a TPS 2500 S thermal property analyzer by the Hot Disk Company was employed. To understand the measurement and analysis process of the TPS method, two different sample materials were evaluated at ambient conditions. These samples included a stainless steel pellet and an inactivated (non-pyrophoric) metal hydride pellet. Thermal conductivity and thermal diffusivity of these samples were measured using the TPS method. The thermal property measurements are compared to the data available in the literature (stainless steel) and the data obtained using laser flash method (metal hydride). The improvements needed to successfully implement the TPS method are discussed in detail.

Physics based models for metal hydride particle morphology, distribution, and effective thermal conductivity

2009 ◽  
Vol 1172 ◽  
Author(s):  
Kyle Christopher Smith ◽  
Timothy Fisher
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Effective Thermal Conductivity ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Particle Morphology ◽  
Particle Packing ◽  
Interparticle Contact ◽  
Storage Media ◽  
Particle Size And Shape

AbstractThis paper describes a modeling approach to target aspects of heat conduction in metal hydride powders that are essential to metal hydrides as viable H2storage media, including particle morphology distribution, size distribution, particle packing properties at specified solid fraction, and effective thermal conductivity. An isotropic fracture model is presented that replicates features of particle size and shape distributions observed experimentally. The discrete element method is used to simulate evolution of metal hydride particle contact networks during quasi-static consolidation of decrepitated metal hydride powders. Finally, the effective thermal conductivity of such a powder is modeled assuming that contact conductance is the same for each interparticle contact.

Investigation of a Solar-Thermal Bio-mimetic Metal Hydride Actuator

2003 ◽  
Vol 125 (1) ◽  
pp. 95-100 ◽  
Author(s):  
George M. Lloyd ◽  
Kwang J. Kim ◽  
A. Razani ◽  
Mohsen Shahinpoor
Keyword(s):  
Metal Hydride ◽  
Response Times ◽  
Complete Solution ◽  
Porous Metal ◽  
Solar Thermal ◽  
Performance Bounds ◽  
Solar Thermal Energy ◽  
Energy Applications ◽  
Advantages And Disadvantages ◽  
Thermal Actuators

Metal hydrides have been investigated for use in a number of solar thermal energy applications, such as heat regenerators or hydrogen storage technology, but rarely for thermal actuators. Preliminary experimental results from a prototype solar thermal metal hydride actuator, using copper-encapsulated porous metal hydride compacts of LaNi5, indicate that this thermal-mechanical system can produce high specific forces (over 100 (N/g)), with response times on the order of seconds. These operational characteristics, along with features such as being bio-mimetic, compact, operationally safe, lubricationless, noiseless, soft actuating, and environmentally benign, result in an actuator that is ideal for many industrial, space, defense, and biomedical applications. In this paper, we report recent work directed toward predicting and characterizing the performance bounds of the actuator, specifically concentrating on elements which might comprise an actuator driven by concentrated solar radiation. A complete solution of the 1-D governing heat and mass transfer equations with an ideally selective reactor surface are used to predict bounds on performance in terms of volume flow rates and realistic actuation times. The advantages and disadvantages of the design are discussed from this perspective. The preliminary data show a great potential for these metal hydride actuators to be used for solar thermo-mechanical applications.

Advanced Transient Plane Source Method for the Measurement of Thermal Properties of High Pressure Metal Hydrides

2009 ◽  
Author(s):  
Scott Flueckiger ◽  
Tyler Voskuilen ◽  
Yuan Zheng ◽  
Timothe´e Pourpoint
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Effective Thermal Conductivity ◽  
Metal Hydride ◽  
Metal Hydrides ◽  
Test Method ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Metal hydrides are a promising material type for hydrogen storage in automotive applications, but thermal property data is needed to optimize the necessary heat exchangers. In the present work, the transient plane source method is integrated with a pressure vessel to measure these properties for metal hydride powder as a function of pressure during the hydrogenation process. The properties under investigation include effective thermal conductivity, thermal diffusivity, specific heat, and thermal contact resistance. The results of this work with oxidized Ti1.1CrMn powder provide effective thermal conductivity values similar to data reported in literature for other metal hydride materials. The experimental measurements are also well modeled by the Zehner-Bauer-Schlu˝nder interpretive model for packed beds as a function of gas pressure. Extending the test method and ZBS model to estimate the contact resistance provides values that were two orders of magnitude less than measurements previously reported for other hydride materials.

Sign in / Sign up

Export Citation Format

Share Document