Reversible metal hydride thermal energy storage systems, devices, and process for high temperature applications

Abstract

High-temperature thermal energy storage and retrieval systems, devices, and processes are described that reversibly store high-temperature heat in metal hydride beds composed of titanium-containing metals or transition metal alloy that reversibly form metal hydrides at high temperatures above about 600° C. and at low temperatures at or below 100° C. The present invention provides exergetic efficiency up to 96% or better.

What is claimed is: 
     
         1 . A reversible thermal energy storage and retrieval system, comprising:
 at least one HT reservoir and at least one LT reservoir, each reservoir including a metal hydride bed,   wherein the metal hydride bed of the HT reservoir comprises a titanium-containing metal in the presence of hydrogen gas that reversibly forms a metal hydride at a temperature at or above about 600° C.;   wherein the metal hydride bed of the LT reservoir comprises a transition metal alloy that reversibly forms a metal hydride in a hydrogen gas environment at a temperature at or below about 100° C.; and   a hydrogen transfer device configured to transfer hydrogen gas between the metal hydride bed of the HT reservoir and the metal hydride bed of the LT reservoir or vice versa that maintains an ambient or near-ambient hydrogen pressure in the respective reservoirs during a thermal cycle operation.   
     
     
         2 . The system of  claim 1 , wherein the metal hydride bed of the respective HT and LT reservoirs include one or more storage containers with an internal compartment comprising a selected density of adjacent conducting metal disks disposed a selected distance apart therein that span at least a portion of the length or internal volume of the internal compartment, the separation distance between the metal disks defines a space configured to receive a titanium-containing metal or a transition metal alloy therein configured to reversibly form a metal hydride during operation, the metal disks enhance thermal conductivity through the metal hydride in the metal hydride bed in at least a radial direction during a thermal cycle. 
     
     
         3 . The system of  claim 1 , wherein the gas transfer device is a sintered porous conduit disposed within the metal hydride bed with an inner bore of a selected dimension configured to deliver hydrogen into the metal hydride bed for formation of the metal hydride and to recover hydrogen released from the metal hydride bed during operation. 
     
     
         4 . The system of  claim 1 , wherein the heat transfer fluid for the HT metal hydride bed is selected from sodium metal, lead-bismuth, tin-antimony, and the heat transfer fluid for the LT metal hydride bed is selected from water, propylene glycol, ethylene glycol, or mixtures thereof. 
     
     
         5 . The system of  claim 1 , wherein the titanium-containing metal and transition metal alloy are in the form of compressed powder disks disposed in the one or more HT and LT reservoirs, respectively. 
     
     
         6 . The system of  claim 1 , wherein the metal disposed within the HT metal hydride bed comprises titanium metal and the metal alloy within the LT metal hydride bed comprises one or more metals selected from: Ti, Fe, Ni, Mn, or combinations thereof. 
     
     
         7 . The system of  claim 1 , wherein the energy density is at least about 750 kJ/kg and the volumetric energy density is at least about 3,000 kWh/m 3 . 
     
     
         8 . The system of  claim 1 , wherein the exergetic efficiency is up to about 95% or better. 
     
     
         9 . A reversible thermal energy storage and retrieval device, comprising:
 a container constructed of a corrosion-resistant metal or metal alloy with an internal compartment comprising a selected density of adjacent conducting metal disks disposed a selected distance apart therein that span at least a portion of the length or internal volume of the internal compartment, the separation distance between the metal disks defines a space configured to receive a titanium-containing metal or a transition metal alloy that when introduced defines a metal hydride bed configured to reversibly form a metal hydride during operation at a temperature at or above 600° C. or at or below 100° C., the metal disks enhance thermal conductivity through the metal hydride in the metal hydride bed in at least a radial direction during a thermal cycle.   
     
     
         10 . The device of  claim 9 , wherein the metal or metal alloy is in the form of compressed powder disks that are insertable in the space disposed between the conducting metal disks. 
     
     
         11 . The device of  claim 9 , wherein the metal alloy comprises one or more metals selected from the group consisting of: Ti, Fe, Ni, Mn, and combinations thereof. 
     
     
         12 . The device of  claim 9 , wherein the titanium-containing metal reversibly forms titanium metal hydride at a high temperature between about 600° C. and about 800° C. 
     
     
         13 . The device of  claim 9 , wherein the transition metal alloy is a titanium-containing metal alloy that reversibly forms a metal hydride at a low temperature between about 20° C. and about 100° C. 
     
     
         14 . The device of  claim 9 , further includes a sintered porous metal conduit that couples to the conducting metal disks disposed therein constructed of a selected metal or metal alloy with an inner bore of a selected dimension configured to deliver hydrogen into the metal hydride bed for formation of the metal hydride and to recover hydrogen released from the metal hydride bed during a thermal cycle operation. 
     
     
         15 . The device of  claim 14 , wherein the sintered porous conduit maintains a hydrogen gas pressure in the metal hydride beds of the HT and LT reservoirs between about 0.1 MPa and about 1 MPa. 
     
     
         16 . The device of  claim 9 , wherein the heat transfer fluid for the HT bed includes selected from sodium metal, lead-bismuth, tin-antimony, and the heat transfer fluid for the LT bed is selected from water, propylene glycol, ethylene glycol or mixtures thereof. 
     
     
         17 . The device of  claim 9 , wherein the density of conducting metal disks is between 2% and 10% of the volume of the HT or LT reservoir, respectively. 
     
     
         18 . A process for reversible thermal energy storage and retrieval, comprising the steps of:
 providing at least one HT reservoir and at least one LT reservoir each containing a metal hydride bed comprising a titanium-containing metal or a transition metal alloy, the HT metal hydride bed is configured to reversibly form a metal hydride at a temperature at or above about 600° C., the LT metal hydride bed is configured to reversibly form a transition metal alloy at a temperature at or below about 100° C.;   contacting the metal hydride in the HT reservoir with heat introduced from a high-temperature heat source to release hydrogen from the metal hydride therein;   absorbing hydrogen released from the HT reservoir in the metal hydride bed of the LT reservoir to store high-temperature heat therein;   releasing high-temperature heat at a temperature above 600° C. from the metal hydride bed of the HT reservoir to generate power.   
     
     
         19 . The process of  claim 18 , wherein providing the HT reservoir and the LT reservoir includes inserting the titanium-containing metal or the transition metal-containing metal alloy between adjacent conducting metal disks disposed within one or more storage containers within the metal hydride beds of the HT and LT reservoirs, respectively. 
     
     
         20 . The process of  claim 18 , wherein releasing heat from the HT metal hydride bed includes delivering the heat to a Rankine steam cycle to generate power. 
     
     
         21 . The process of  claim 18 , further including recovering high-temperature heat from hydrogen gas released from the HT metal hydride bed in a recuperation system to recuperate heat used to preheat feed water into a Rankine steam cycle. 
     
     
         22 . The process of  claim 18 , wherein the process includes matching the hydrogen flow rate between the HT reservoir and the LT reservoir during operation.