Systems, Apparatus, and Methods for Storing and Discharging Thermochemical Energy

This application claims benefit of and priority from co-pending provisional U.S. Patent Application No. 63/659,827, filed Jun. 13, 2024, the content of which is hereby incorporated by reference in its entirety as if set forth herein in full, for all purposes.

This application and the subject matter disclosed herein (collectively referred to as the “disclosure”) generally concern energy storage and discharge technology and related systems and methods. More particularly, but not exclusively, this disclosure pertains to reactors to store and discharge energy from materials that possess high and lasting energy density, mechanical strength, and related components, systems, and methods (including methods of operating and designing such reactors).

Some solid materials react with a fluid and release energy in the form of heat. Such solid material systems include, for example, metal oxide/hydroxide systems such as CaO/Ca(OH), MgO/Mg(OH), salts such as, for example, Glauber salt, or metal oxide/carbonate systems such as, for example, CaO/CaCO, or metal oxide systems such as, for example, manganese oxide, or metal hydride systems such as, for example, MgH. Typically these material systems release fluids such as, for example, water vapor or COor Oor Hduring energy storage and they consume these respective fluids released during energy discharge. For example:

However, the chemical reactor and associated system to carry out such chemical reactions are complicated and expensive. The reactors further do not have efficient heat and mass transfer required for an energy storage system.

In some respects, concepts disclosed herein generally concern systems and methods for storing and discharging thermochemical energy. Some disclosed concepts pertain to systems, methods, and components to reactors suitable for carrying out chemical reactions that alternatively store or discharge energy. As but one example, some disclosed reactors enable reactions with a high roundtrip efficiency, allowing a significantly higher portion of stored thermochemical energy to be generated and recovered in a useful form as heat.

Thermochemical energy storage based on a solid/fluid reaction can provide high energy density, high reaction temperatures, and insulation-free storage. For example, some reactions involve a mixture of a gas (e.g., air) and water vapor in the form of steam or humidified air as the reaction gas. In other embodiments, reactions can involve compressed air as the reaction gas to carbonate or oxidize the solid material. In another embodiment, reactions involve hydrogen as the reaction gas to hydrate the solid material.

Such reactions have various attractive attributes. For example, the solid material in such an embodiment is non-toxic. Further, reactant gases such as, for example, water vapor or air or hydrogen can be stored. In the case of reactions involving water vapor, some disclosed principles can prevent or reduce condensation of water vapor compared to previously disclosed systems. Consequently, some disclosed concepts provide high roundtrip efficiency when energy is stored and released using a CaO/Ca(OH)system, a MgO/Mg(OH)system, and other systems.

Thermochemical storage systems involve storing and generating energy through chemical reactions. Charging (or energy storage) typically involves heating a hydrated or carbonated or oxidized or hydrogenated material (e.g., metal hydroxide, metal carbonate, metal oxide or metal hydride) to a high temperature, e.g., upwards of 120° C. to dehydrate or decarbonate or reduce or dehydrogenate, respectively, the material and form a dehydrated or a decarbonated or a reduced or a dehydrogenated material (e.g., metal oxide). Discharge (or energy release) involves initiating and maintaining a reaction by, in part, supplying a suitable reactant to the respective dehydrated or decarbonated or reduced or dehydrogenated material, such as, for example, supplying gaseous water, i.e., water vapor in form of steam or humidified air, to hydrate the dehydrated material, or supplying gaseous COto carbonate the decarbonated material, or supplying Oto oxidize the reduced material (e.g., metal oxide) or supplying gaseous Hto hydrogenate the dehydrogenated material (e.g., metal hydride) and reform the hydrated/carbonated/oxidized/hydrogenated material (e.g., metal hydroxide, metal carbonate or metal oxide or metal hydride).

Known classes of chemical reactors such as, for example, fixed bed, moving bed and fluidized bed reactors can be used to supply a gaseous reactant (e.g., water vapor/CO/O/H) to the charged material in the reactor. However, whether such reactors operate effectively depends on certain properties of the discharged material. For example, CaO in its natural form is typically a powder, and merely supplying steam, humidified air, or water to such a powdered form of CaO simply turns the material to an unusable sludge.

Relevant material properties that allow storage materials to be effective can include, for example, the material's physical strength and thermal conductivity. Applicant's co-pending U.S. patent application Ser. No. 63/632,282, filed Apr. 10, 2024, disclosed details of high-strength CaO/Ca(OH)pellets that can be used and recycled over thousands of cycles of charging and discharging without any major degradation of the strength or reactivity of the material.

Presently disclosed reactors, for example, moving bed reactors, can be used for charging and discharging of thermochemical storage material, including but not limited to materials described in the '282 application, to obtain high roundtrip efficiency. In addition to disclosing details of reactor embodiments, this disclosure also describes methods to optimize or otherwise to enhance the performance of disclosed reactors by effectively reusing byproducts of the reactions and the reactor. For example, many of the thermochemical reaction systems involve using HO in its liquid phase, gas phase, or a saturated mixture thereof, to discharge energy from a storage material, e.g., CaO.

Moreover, disclosed thermochemical energy storage systems can be generally deployed at sites that presently require steam for their current, regular operation. For example, industries that require heat to carry out an industrial process, water treatment plants, power generating stations that rely on steam turbines, etc., can integrate disclosed energy storage systems with one or more adjacent processes that demand steam. Incorporating disclosed storage and discharge systems and methods can improve overall process efficiency, as well as roundtrip efficiency of the energy storage and discharge system. These systems can be optimized to perform with a round-trip efficiency of 95% or greater, which is desirable across applications of disclosed energy systems. Similarly, reusing steam or other byproducts for preheating or fluidization (e.g., if the chemical reactor is a fluidized bed reactor) can also improve roundtrip efficiency.

An exemplary charging process can involve heating discharged material to a high temperature, e.g., using an available energy source, such as, for example, solar energy (e.g., directed or concentrated solar energy, or electricity generated using photovoltaics), wind energy (e.g., electricity generated using wind turbines), hydroelectric energy, combustion, e.g., combustion of organic material, petroleum-based fuel or natural gas (whether by heating directly by heating from electricity generated from a combustion-driven generator). Such heating can release water vapor or COor Oor Hdepending on the discharge material used. In some such embodiments, heating releases water molecules from a dehydratable material in the form of water vapor. The water vapor released can be used in multiple ways. For example, the water vapor can be condensed and stored as hot water in an insulated storage tank. Alternatively, it can be sent to a heat exchanger to provide heat to another heat-transfer fluid. As yet another alternative, the water vapor can be recirculated to supply necessary moisture for the discharge reaction.

A discharge process can involve passing one or more fluids, such as, for example, water in liquid or vapor form or COor Oor Hin gaseous form through the reactor to discharge a charged material compatible with the fluid. For example, water vapor can be used to hydrate a dehydrated material so as to release energy from the hydrated material. The final output from the reactor during such a discharge process in this embodiment is heated air at temperatures aboveC. The heated air can be sent to a heat exchanger to utilize the heat released in the respective application. The same reactor can be used to perform both charging and discharging. It will be appreciated that less than 100% of the fluid may be consumed as the mixture of the fluid and air passes through the reactor, and thus the “heated air” noted above may include a mixture having a minor portion of the fluid reactant present.

According to a disclosed aspect, a reaction chamber of a reactor can include a heating element and a fluid source (e.g., a source of water vapor or other fluid reactant) that are selectively operable according to whether an incoming material is in its charged state (e.g., a dehydrated state, for example) or discharged state (e.g., its hydrated state, for example). For example, the heating element can operate when an incoming material is in its discharged (e.g., hydrated) state, heating the material as it passes through the reaction chamber and driving off a gas (e.g., water in the form of water vapor or COor Oor Hin gaseous form). In this operational mode (a “charging mode”), the fluid source is inactive. Alternatively, the heating element can be turned off when an incoming material is in its charged (e.g., dehydrated) state. In this operational mode, the fluid source can be activated, allowing a portion of the incoming fluid to react with the charged material. In some embodiments, incoming water vapor hydrates the incoming, hydratable (charged) material which in turn generates (or releases) “chemically stored” heat and superheats the remaining water vapor passing through the reaction chamber. Alternatively, an external region of the reaction chamber can transfer the excess heat to another working fluid to supply energy to a load, e.g., a steam turbine, a heat exchanger for facility heating, or an industrial process that uses steam, to perform a mechanical process (work). Alternatively, the heat can be used to drive or facilitate a chemical process.

According to an aspect, a reactor for charging and discharging a thermochemical energy storage (TCES) material has an inlet for receiving a pelletized TCES material and an outlet for exhausting the pelletized TCES material. A selectively operable heater is configured to heat the pelletized TCES material in a charging mode. A blower is configured to urge a stream of air over the pelletized TCES material in the charging mode and to urge a stream of another fluid over the pelletized TCES material in a discharging mode. A reaction chamber houses the selectively operable heater. The reaction chamber is so configured to receive the pelletized TCES material within the reaction chamber from the inlet and configured to exhaust the pelletized TCES material from the reaction chamber to the outlet. The reaction chamber is further configured to direct the stream of stream of air over the pelletized TCES material in the charging mode and to direct the stream of another fluid over the pelletized TCES material in the discharging mode.

In some embodiments, the reactor also includes a hopper configured to direct the pelletized TCES material to the inlet. Further, some embodiments also include a conveyor configured to convey the pelletized TCES material from a storage container to the hopper.

A metering device can be configured to regulate a rate at which the pelletized TCES material enters the reaction chamber.

A conveyor can be configured to convey the pelletized TCES material exhausted from the outlet away from the reaction chamber.

A cyclone or other dust collector can be so coupled with the reaction chamber as to receive the stream of air in the charging mode, the stream of another fluid in the discharging mode, or both, from the reaction chamber. The cyclone or other dust collector can be configured to filter dust from the respective stream.

The reaction chamber can be further configured such that, in the discharging mode, the stream of another fluid comprises one or more of air, water vapor, humidified air, CO, H, and O. The reaction chamber can also be configured such that, in the discharging mode, the stream of another fluid exhausts from the reaction chamber at a temperature higher than a temperature at which the stream of another fluid enters the reaction chamber.

The temperature of the stream of another fluid as it exhausts from the reaction chamber is between about 30° C. and about 500° C.

The stream of another fluid can include predominately air and exhausts from the reaction chamber at a temperature above about 200°° C.

The stream of another fluid can include predominately COand exhausts from the reaction chamber at a temperature above about 500° C.

The stream of another fluid can include Hand exhausts from the reaction chamber at a temperature above about 250° C.

The stream of another fluid can include predominately water vapor and exhausts from the reaction chamber at a temperature between about 120° C. and about 300° C.

The reaction chamber can have an upper zone vertically positioned above a lower zone and a reaction zone positioned vertically between the upper zone and the lower zone.

The reaction chamber can be configured to add sensible energy to the pelletized TCES material as the pelletized TCES material passes through the upper zone in the charging mode and in the discharging mode.

The selectively operable heater can be positioned in the reaction zone of the reaction chamber.

The inlet for receiving a pelletized TCES material can be configured to convey the pelletized TCES material to the upper zone.

The outlet for exhausting the pelletized TCES material can be configured to convey the pelletized TCES material from the lower zone.

The selectively operable heater can be configured to heat the pelletized TCES material in the charging mode to a temperature at least as high as a decomposition temperature of the pelletized TCES material.

The reactor can be configured to continuously release about 100 kW from a pelletized TCES material comprising CaO/Ca(OH).

Methods also are disclosed. For example, a method of charging and discharging a thermochemical energy storage (TCES) material with a reactor can include receiving at an inlet to a reaction chamber a discharged formed of a pelletized TCES material. The discharged form of the pelletized TCES material can be heated to temperature at least as high as a decomposition temperature of the pelletized TCES material with a selectively operable heater positioned in the reaction chamber. A blower can urge a stream of air through the reaction chamber. The reaction chamber can be configured to direct the stream of air over the pelletized TCES material while the pelletized TCES material is being heated by the selectively operable heater. A charged form of the pelletized TCES material can exhaust through an outlet from the reaction chamber. The charged form of the pelletized TCES material can be hydrated or oxidized to release energy in the form of heat from the charged form of the pelletized TCES material.

The foregoing and other features and advantages will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

The following describes various principles related to systems and methods for storing and discharging thermochemical energy. For example, certain aspects of disclosed principles pertain to reactors for facilitating thermochemical reactions that store and release energy in the form of heat. That said, descriptions herein of specific apparatus configurations, material systems, and combinations of method acts are but particular examples of contemplated systems chosen as being convenient illustrative examples of disclosed principles. One or more of the disclosed principles can be incorporated in various other systems to achieve any of a variety of corresponding system characteristics.

Thus, systems having attributes that are different from those specific examples discussed herein can embody one or more presently disclosed principles, and can be used in applications not described herein in detail. Accordingly, such alternative embodiments also fall within the scope of this disclosure and the claims appended hereto.

Among various principles described herein are aspects pertaining to the design and use of a reactor that can be used to store and to discharge thermochemical energy. In some embodiments, this includes a continuously moving storage medium that can be charged by heating the material to a desired temperature and discharged (hydrated) through other means, such as, for example, passing humidified air, water vapor or liquid water or gaseous COor Oor Hthrough the reactor (and thereby exposing a charged material to fluid molecules, which in turn provides an exothermic chemical reaction). The means of discharging can depend on the type of material and the nature of the chemical reaction used for energy storage. For example, hydration and dehydration of oxide/hydroxide systems.

shows an embodiment of a moving bed reactorthat can be employed for charging and discharging of an energy-storage material. The illustrated reactor includes a cylindrical vesselwhose dimensions can be adjusted according to a desired reactor output, e.g., a power output. For example, a reactor vessel having a one-foot (1 ft.) diameter can facilitate a continuous reaction of a thermochemical energy storage material with water (e.g., CaO+water vapor) that releases about 100 kW.

As described in U.S. patent application Ser. No. 63/632,282, filed Apr. 10, 2024, the contents of which are hereby incorporated as fully as if reproduced herein in full, for all purposes, the energy storage medium can be a pelletized solid, e.g., spherical pellets with a diameter ranging from between about 2 mm and about 6 mm, such as, for example, between about 3 mm and about 5 mm, or about 4 mm. An upper regionof the reactorincludes a hopperthat directs material to a reactor inlet. The fresh reactive material (e.g., pellets) to be reacted, e.g., stored in a container such as, for example, a grain silo, can be fed to the hopperusing any of a variety of conventional conveying systems, e.g., a flexible screw conveyor(), a belt conveyor, or a bucket elevator. A rotary valveor other metering device can control a rate at which fresh material is fed into the reactor vessel.

The rate at which fresh material is added to, or a level of the fresh material added into, the reactor vessel can be monitored by a sensor, e.g., a sensor having a rotary paddle. The sensor can be positioned to facilitate accurate observation of a rate of the material feed. Output from a sensor so positioned can be used as an input to a controller used to regulate, e.g., to selectively control, the rate at which the material is fed. A suitable position can correspond, in part, to the type of sensor employed for observing such a feed rate. For example, if the sensor is continuously monitors a level of material, e.g., such as, for example, a radar sensor or a capacitive sensor, mounting the sensor directly above the material feed may be preferred. On another hand, a point level detection sensor such as, for example, a paddle switch, can be mounted on a side wall. In some embodiments multiple sensors can be mounted along a wall to account for variations in observed feed rates, e.g., that can result from, for example, the angle of repose of the material. A rotational speed of the rotary valve can correspond, in some embodiments, to a rate at which the fresh material is being added to the reactor. Similarly, a level (e.g., a fill level) of the material in the reactor can be monitored using another sensor, e.g., an optical sensor (not shown).

The fresh material can be gravity fed, e.g., can move through the hopperinto the vesselassisted by gravity. For example, after the material moves through the falling bed reactor, converted material can be conveyed away from a lower end region, allowing additional fresh material to be fed into the upper end region of the reactor.

Converted material that reaches a lower regionof the vesselcan be conveyed out of the reactorusing a selected conveying systems, e.g., as mentioned above. In an embodiment, the outlet conveying system is a screw conveyor(). A valve system, or a valve-like system, can inhibit or prevent air from leaking into a flow of pellets being fed into the reactor or being extracted from (e.g., taken out of) the reactor. For example, rotary airlocks and double flap valves can serve this purpose. In some embodiments, a pair of valves can be coupled in series with each other to inhibit or prevent air from leaking into a flow of pellets. For example, one of the pair of valves can be open while the other valve in the pair of valves is closed as material moves through the reactor. Inlet(s) and outlet(s) for the fluid flow can be covered with an appropriately sized mesh to prevent pellets from leaking out of the reactor while still permitting fluid to flow. In some embodiments, a surge hopper is installed at the top of the reactor to meter or otherwise regular a flow of material into the reactor vessel. The vesselcan be insulated to inhibit heat lost from the reactor. For example, suitable thermal insulation material can include any suitable ceramic-based insulation, such as, for example, fiberglass.

One or more heating elements(sometimes referred to individually as a “heater”) can be arranged within or throughout an interior of the reactor vesselto provide uniform (or selected non-uniform) heating of the material as it moves down through the reactor. The heating elementcan be chosen based on a desired reaction temperature range and a physical arrangement of the one or more heating elementsin the reactor. In some embodiments, a heating element can include or be configured as a cartridge heater, e.g., which can include a resistive heating element, e.g., a wire. A suitable material for such an electrical wire can be nichrome, e.g., for temperatures up to about 1000 C, or molybdenum disilicide or silicon carbide, e.g., for temperatures at or above about 1000 C. In either embodiment, each resistive heating element can be electrically insulated. In some embodiments, the electrical insulation can be made of magnesium oxide. A sheath provided on an exterior of the cartridge heater can be made from a selected grade of stainless steel, such as, for example,,or.

Although particular aspects of cartridge heaters are described above, any type of heater can be used within the reactor systemso long as it is capable of heating an incoming rate of energy storage material to a suitable temperature that facilitates a desired reaction. The number of heating elements used in the system can correspond, in part, to a desired output power of the reactor, heat loss from the reactor, and whether or to what extent any input heat is absorbed by a material as sensible or latent heat.

For example, an embodiment of a 100 kW reactor includes 18 heaters, each capable of generating 6.6 kW. As well, the spatial distribution of heatersthroughout the reactor vesselcan depend on a desired distance between adjacent heaters, e.g., a desired heat flux, a desired operating temperature within the reactor, a thermal conductivity of the material being charged, and a rate at which material is fed through and discharged from the reactor (which also corresponds to a power output of the reactor). For example, the desired reaction temperature for the CaO/Ca(OH)material system is above about 450° C. Hence, a distance between adjacent heaters in a 100 kW reactor designed to operate using CaO/Ca(OH)is, in some embodiments, between about 2 inches and about 4 inches, for example.

A suitable distribution of heatersfor such a reactor is shown by way of illustration inand. In the illustrated embodiment, the heatersare suspended vertically within the reactor from an upper region thereof. Accordingly, the heatersneed to be supported at or near their lower ends to inhibit or prevent deformation, e.g., due to a bending stress. Hence, a base plateis designed and installed in a lower regionof the reactor vessel to support the heaters. The reactor can be scaled up or down in size by increasing or decreasing the diameter of the vessel, the number of heaters, the rate at which the heaters generate heat, and the rate at which material is fed into, through and discharged from the reactor. In other embodiments, operating temperature within the reactor can be selected by selecting a suitable combination of density of heating elements, rate of heating generated by each element, and a rate of discharged material passing through the reactor. As well, some embodiments pre-heat the charged material before it is discharged. For example, there can be excess heat generated by the reactor compared to a load being driven by the reactor. Nevertheless, a consideration of whether or to what extent preheating may be available or desirable is whether available energy for charging exceeds the anticipated load, plus irreversible process losses, to be driven by the discharge process.

During a charging (or energy storage, e.g., dehydration) process, the heaters can be set to a desired output power (e.g., which, as noted, corresponds in part to a desired reaction temperature and feed-rate of material through the reactor). Storage material can be fed to the reactorthrough the hopper. As the energy storage material flows through the reactor, e.g., by virtue of gravity, the material gets heated up or charged (e.g. dehydrated).

In the CaO/Ca(OH)material system, charging involves heating Ca(OH)to a temperature above about 450° C. to form CaO and release water vapor. The height of the vessel(e.g., a “flow length” within the vessel through which material passes) can correspond, in part, to the reaction kinetics and can be selected such that the material stays above the reaction (or another desired) temperature for a desired amount of time as the material moves down through the bed. One or more thermocouplescan be placed along the heating element'slength to measure the temperature of the heater. Similarly, one or more thermocouples (not shown) can be placed along a wall (e.g., an interior wall) of the reactor vessel to measure temperature at each of a variety of positions, e.g., longitudinally along the reactor vessel from the upper regionto the lower region. A control unit can monitor the temperatures measured by the thermocouples and can adjust a rate at which material passes through the reactor vessel, e.g., can adjust the valve, or a rate of heating by the heaters. For an embodiment of a 100 kW reactor using CaO/Ca(OH)as the storage material, the height of the vessel can be about 12 ft, e.g., to provide a residence time of the material passing through the reactor of about 30 minutes.