Reversible hydride thermal energy storage cell optimized for solar applications

Abstract

A solar energy collection and storage system and a method of collecting and storing solar energy. The system includes a device for focusing solar energy onto a reaction chamber for the conversion of metal hydride to liquid metal and hydrogen, a metal/metal hydride chamber containing a metal/metal hydride mixture, a hydrogen storage system using hydrides and a thermo-cline for recovering the thermal energy from the hydrogen when it is cooled from 2000 F to ambient conditions for storage.

1 . A solar energy collection and storage system including:
 A device for focusing solar energy, or any type of thermal energy, into a reaction chamber for the conversion of metal hydride to liquid metal and hydrogen,
 a metal/metal hydride vessel containing a metal/metal hydride mixture, 
 a hydrogen storage system. 
   
     
     
         2 . The system of  claim 1  wherein the metal is selected from the group of calcium, magnesium, strontium, barium, lithium, sodium, potassium, titanium, or zirconium. 
     
     
         3 . The system of  claim 1  wherein the hydride is selected form the group of metal boro-hydrides of lithium, sodium, or potassium. 
     
     
         4 . The system of  claim 1  wherein the reaction vessel is at the focus of a helio-stat or field of solar mirrors. 
     
     
         5 . The system of  claim 1  wherein the reaction vessel has a quartz window and a molybdenum conduit projecting within the metal/metal hydride so that sunlight can project onto the bottom of the conduit for heating the metal/metal hydride. 
     
     
         6 . The system of  claim 1  wherein the reaction vessel has a heat pipe projecting out of the top of the reaction vessel with the heat pipe also extending into the metal/metal hydride for heating the metal/metal hydride. 
     
     
         7 . The system of  claim 1  wherein a heat transfer conduit projects through reactor lid and into the metal/metal hydride. 
     
     
         8 . The system of  claim 1  wherein a hydrogen flow line projects into the reactor vessel. 
     
     
         9 . The system of  claim 1  wherein the metal/metal hydride pressure vessel is located within an outer pressure vessel and an annular space exists between the metal hydride pressure vessel and the inner wall of the outer pressure vessel. 
     
     
         10 . The system of  claim 1  wherein the metal/metal hydride is contained within an inner metal or ceramic vessel, a mid metal container supports the inner vessel, and an outer pressure vessel supports both the inner and mid vessels. 
     
     
         11 . The system of  claim 1  wherein the inner vessel is fabricated from molybdenum with a lanthanum oxide dispersion. 
     
     
         12 . The system of  claim 1  wherein the inner vessel is fabricated from a calcium aluminate or calcium oxide ceramic. 
     
     
         13 . The system of  claim 1  wherein the inner vessel is fabricated with an internal metal wire mesh which is covered with ceramic creating an enhanced structural inner vessel. 
     
     
         14 . The system of  claim 1  wherein the inner vessel is supported by a rigid or powdered ceramic such as silicon dioxide or aluminum oxide or calcium oxide. 
     
     
         15 . The system of  claim 1  wherein a primary gas stream extends from the reaction chamber to a hydrogen storage vessel. 
     
     
         16 . The system of  claim 1  wherein a primary gas stream extends from the reaction chamber through a heat transfer thermocline to a hydrogen storage vessel. 
     
     
         17 . The system of  claim 1  wherein hydrogen storage system comprises one or multiple hydrogen storage vessels, the hydrogen storage material comprising a metal or metal alloy capable of reacting with or absorbing hydrogen. 
     
     
         18 . The system of  claim 1  wherein the hydride storage material is at least one metal hydride selected from the group of magnesium nickel hydride, lithium aluminum hydride, magnesium iron hydride, lanthanum nickel aluminum hydride, calcium nickel hydride, titanium iron hydride, and magnesium hydride. 
     
     
         19 . The system of  claim 1  wherein multiple hydride storage vessels are contained within a water cooled tank. 
     
     
         20 . The system of  claim 1  wherein the hydrogen storage system is hydrogen stored as a compressed gas or liquid. 
     
     
         21 . The system of  claim 1  wherein a heat exchanger and heat storage system is provided to recover heat from the primary hydrogen gas stream between the reaction chamber and the hydrogen storage vessel. 
     
     
         22 . The system of  claim 1  wherein the heat changer material is boron oxide. 
     
     
         23 . The system of  claim 1  wherein the heat exchanger has graphite fiber, dispersed within the boron oxide, oriented predominantly sideways relative to the direction of hydrogen flowing within multiple heat transport tubes with the heat exchanger operating as a thermo-cline. 
     
     
         24 . The system of  claim 1  wherein the boron oxide, in the heat exchanger, flows within a counter flow heat exchanger transferring heat with the hydrogen gas. 
     
     
         25 . The system of  claim 1  wherein the heat exchanger consists of a high and low temperature tanks system with separate heat transfer materials handling a high and low temperature hydrogen temperature range. 
     
     
         26 . The system of  claim 1  wherein the 2 nd  heat exchanger utilizes a nitrate salt mixture from the group of alkaline metal nitrates. 
     
     
         27 . The system of  claim 1  wherein the heat exchange occurs with the hydrogen gas without mixing between the hydrogen gas and the heat exchange materials. 
     
     
         28 . The system of  claim 1  wherein the hydrogen gas flows from the hydrogen storage system into the reactor providing a chemical reaction with the metal to create the hydride and thermal energy. 
     
     
         29 . A thermal storage method wherein energy is stored when a compound of two or more materials are separated into components.
 Said components operate reversibly so that when they combine they release thermal energy and when they are separated they absorb thermal energy.   Said components store their energy in the heat of formation differences between the individual materials or elements and the compound which is formed when they are brought together.   
     
     
         30 . The method of  claim 29  wherein one of the components is hydrogen and the second component is a metal with the metal remaining in the reactor and the hydrogen being transported to a separate container. 
     
     
         31 . The method of  claim 29  wherein the hydrogen is cooled by flowing the hydrogen through a heat exchanger, with the energy stored in a separate thermal storage container, before the hydrogen is stored. 
     
     
         32 . The method of  claim 29  wherein the hydrogen is stored within a hydride material which can reversibly release the hydrogen when required. 
     
     
         33 . The method of  claim 29  wherein the hydride material uses a flowing liquid reservoir surrounding the storage vessels, such as water, to maintain a constant hydride temperature. 
     
     
         34 . The method of  claim 29  wherein the flowing liquid, used to maintain the hydride storage tanks, uses the thermal heat capacity and temperature of the ground, to maintain the hydride storage tank temperature. 
     
     
         35 . The method of  claim 29  wherein the metal hydride sinks below the metal surface providing a fresh surface for the hydrogen reaction to occur. 
     
     
         36 . The method of  claim 29  wherein the hydrogen pressure is used to control the rate and direction of the exothermic and endothermic processes. 
     
     
         37 . A thermal storage system wherein the process of separating two materials provides a means for the storage of thermal energy in chemical form.
 Said materials release energy when they are recombined.   The direction of said materials to combine or separate is determined by the hydrogen gas pressure at a constant operating temperature.