HK1128311B - Storing and transporting energy - Google Patents

Abstract

Among other things, hydrogen is released from water at a first location using energy from a first energy source; the released hydrogen is stored in a metal hydride slurry; and the metal hydride slurry is transported to a second location remote from the first location.

Description

Storage and transport of energy

Technical Field

The present invention relates to the storage and transportation of energy.

Background

For example, energy in the form of electricity can be stored as hydrogen by applying electricity to the electrolysis process to dissociate hydrogen from oxygen in the water. Energy in the form of heat can also be stored in the form of hydrogen by using a thermal conversion process to dissociate hydrogen from oxygen in water.

Hydrogen can be safely and easily transported by incorporating it into a metal hydride. The hydrogen can then be released by mixing water with a metal hydride and used to power an automobile or the like.

Disclosure of Invention

In one aspect, a method is provided that includes generating hydrogen gas using electricity or heat, and combining the hydrogen gas with a pumpable fluid to form a pumpable hydrogen storage fluid. The pumpable hydrogen storage fluid does not evolve hydrogen gas significantly at room temperature and pressure.

In one aspect, a method is provided that includes releasing hydrogen from water at a first location using energy from a first energy source, storing the released hydrogen in a metal hydride slurry, and transporting the metal hydride slurry to a second location remote from the first location.

In one aspect, a system is provided, comprising: an electrolyzer to extract hydrogen from water at a first location using energy from a first energy source; and a charging device connected with the electrolytic cell. The charging apparatus has a slurry inlet, a slurry outlet, and a heating apparatus capable of heating the slurry in the charging apparatus to at least about 320 ℃.

In one aspect, a system is provided, comprising: an electrolytic cell comprising an electrical connection; and a hydride slurry charging device connected to the electrolytic cell.

In one aspect, a system is provided, comprising: a first device that uses electricity from a first energy source to produce hydrogen; a metal hydride slurry charging device coupled to the first device; a metal hydride slurry storage container connected to the metal hydride slurry charging device; and a pump to pump the slurry in the metal hydride slurry charging device into the metal hydride slurry storage container.

Implementations may include one or more of the following.

In some embodiments, the pumpable inert fluid comprises a reversible hydride former. In some embodiments, the reversible hydride former includes a reversible metal hydride former (e.g., magnesium) and/or a reversible metal alloy hydride former.

In some embodiments, the method further comprises releasing hydrogen from the metal hydride slurry to form hydrogen and an at least partially depleted metal hydride slurry.

In some embodiments, the method includes transporting the partially depleted metal hydride slurry from the second location to the first location, for example, to recharge the partially depleted metal hydride slurry. For example, the partially depleted metal hydride slurry can be recharged in some cases by releasing energy from the water at the first location using energy from the first energy source and storing the released hydrogen in the depleted metal hydride slurry to form the metal hydride slurry. In some embodiments, the metal hydride slurry can undergo depletion and recharging for at least 50 cycles.

In some embodiments, the first energy source may include a renewable energy source (e.g., wind energy, hydroelectric energy, geothermal energy, ocean power, solar energy, and/or combinations of these energy sources). The first energy source can be used in some embodiments to release hydrogen from water, and the hydrogen can be stored in the metal hydride slurry at a first location. In some embodiments, the metal hydride slurry can be transported from the first location to the second location by a vehicle (e.g., a rail car, a truck, a tanker truck, a pipeline, and any combination of these vehicles). In some embodiments, the hydrogen gas released from the metal hydride slurry (e.g., at the second location) can be used as an energy source (e.g., in a fuel cell). In this way, energy from the first energy source may be efficiently stored and transported to the second location. In some embodiments, the first location has a first energy demand, the second location has a second energy demand, and the first energy demand is lower than the second energy demand.

In some embodiments, the metal hydride slurry comprises magnesium, magnesium hydride, and mineral oil. In some embodiments, the metal hydride slurry further comprises a dispersant.

In some embodiments, the system is capable of maintaining a charging device pressure of at least about 150 psia. In some embodiments, the charging apparatus includes a pump to pump slurry in the charging apparatus through the slurry outlet, e.g., to a storage vessel connected to the charging apparatus slurry outlet. In some embodiments, the charging apparatus includes a regulator to maintain the temperature of the slurry contained in the charging apparatus at no greater than about 350 ℃.

In some embodiments, a system includes a discharge device including a heating device capable of heating a hydride slurry contained in the discharge device to at least about 370 ℃. In some embodiments, the discharge device includes a hydrogen outlet through which hydrogen gas discharged from the hydride slurry can pass.

In some embodiments, the first apparatus of the system comprises an electrolysis cell.

In some embodiments, the system includes a pump coupled to the storage vessel to transfer the slurry in the metal hydride slurry storage vessel to a slurry vehicle (e.g., a truck, boat, rail car, pipeline, or any combination of these vehicles).

In some embodiments, the system includes a metal hydride slurry discharge device that removes hydrogen from the metal hydride slurry.

In general, other aspects include features and aspects described above, alone and in other combinations, expressed as methods, apparatus, systems, program products, and in other ways.

Advantages of these and other features and aspects include one or more of the following.

Energy may be stored in the form of hydrogen at locations where energy is readily available (e.g., from wind and/or sun), but where demand for energy is relatively low, and transported to locations where energy demand is high.

Other features and advantages will be apparent from the description and from the claims.

Drawings

FIG. 1 is a schematic illustration of storing and transporting energy.

Fig. 2 is a schematic diagram of a metal hydride charging device.

Fig. 3 is a schematic diagram of a metal hydride discharge device.

Fig. 4 is a graph of temperature and pressure versus time for charging and discharging a metal hydride slurry.

Detailed Description

Generally, systems and methods for storing and/or transporting energy in the form of hydrogen are provided. For example, energy in the form of hydrogen may be stored by incorporating hydrogen into a reversible metal hydride slurry, which is a slurry that includes a component (e.g., a metal or metal alloy) that can accept hydrogen atoms (hydrogenate) in a reversible manner and can release hydrogen atoms (dehydrogenate), depending on the conditions (e.g., heat and/or pressure) to which the slurry is subjected. Generally, for slurries that include a reversibly hydrogenated component, when a substantial amount (e.g., 80% or more) of the hydrogenatable component is hydrogenated, it can be described as "charged"; where a substantial amount (e.g., 80% or more) of the hydrogenatable component is not hydrogenated, it can be described as "exhausted"; or when the slurry contains hydrogenated and unhydrogenated components, it can be described as "partially charged," wherein the hydrogenated component is present in an amount typically between about 20% and 80% of the total amount of hydrogenatable components. Typically 85% to 95% of the amount of hydrogenatable component is hydrogenated when charged with hydrogen and 5% to 15% is hydrogenated when depleted. In the worst case acceptable, it is possible that at least 70% is hydrogenated when charged and 5% when depleted. In general, a "charged" slurry may include a certain amount of non-hydrogenated hydrogenatable components, while a "depleted" slurry may include a certain amount of hydrogenated hydrogenatable components. Commercial considerations may be taken into account when deciding whether to consider the slurry as charged or depleted; for example, a slurry may be considered "charged" when it has sufficient hydrogenated material to provide the required amount of energy from the hydrogen when it is subjected to discharge. In deciding when to charge the slurry, the following factors may be considered: for example, the cost and time of hydrogenating the slurry, the cost of transporting the slurry to the site of hydrogen evolution, and the cost of alternative energy sources at the site of hydrogen evolution.

In the example of storing and transporting energy 10 shown in fig. 1, energy available at a first location 12, in this case a windmill farm in Kansas, is stored in a safe, easily handled medium, in this case hydrogen in a rechargeable metal hydride slurry, that is transportable to a second location, in this case New York, where it is used, for example in an automobile that is capable of burning hydrogen as fuel.

At the first site 12, the wind causes the rotor 19 of the windmill 15 to rotate, driving the generator 17 to generate electricity. The electricity is transferred to an electrical connection 18 of an electrolysis cell 20 via a cable 16. The cell is part of a charging system 13, which charging system 13 also comprises a charging device 30.

Using electricity, the electrolyzer 20 separates water into hydrogen gas 23 and oxygen gas 25. Water is supplied from a water source 21 through a pipe 22. The hydrogen gas 23 enters the charging device 30 through the hydrogen gas outlet 24 and the pipe 26. Oxygen 25 is discharged from the electrolysis cell 20 through an oxygen outlet 28 where it may be collected for further use or vented to the atmosphere at the oxygen outlet 28.

In some examples, the electrolyzer 20 pumps the hydrogen gas 23 into the charging device 30 under pressure (e.g., at least about 50psia pounds per square inch absolute) and maintains the contents of the charging device under pressure. The pressure may be in the range of about 100psia or greater, 150psia or greater, 200psia or greater, 250psia or greater, 500psia or greater, 1000psia or greater, or 1500psia or greater. The pressure level is set according to the ability of the charging device to withstand the pressure and to handle the heat generated by the reaction. The reaction between the metal hydride and the hydrogen gas will generate heat and charged metal hydride. The reaction rate of the depleted metal hydride with hydrogen generally increases with increasing pressure. An optimal system may use a hydrogen pressure that maximizes the system productivity while minimizing system cost. Higher production rates will generally require smaller and potentially less expensive charging equipment. On the other hand, a fast reaction rate may generate too much heat so that a heat removal system (heat removal system) becomes costly. The optimal system can balance the costs to produce a minimum cost design. One advantage of the metal hydride being in slurry form is that heat transfer can be assisted by agitating the slurry.

In some examples (not illustrated in fig. 1), the hydrogen gas 23 is collected in a hydrogen tank where it is pressurized and then transferred to the charging device 30. For example, if the cost of pressurizing hydrogen to a particular pressure is less than the cost of using an electrolysis device operating at that pressure, or if the hydrogen source is at a lower pressure than is required by the charging device, then the pressurized hydrogen tank may provide hydrogen at the necessary pressure.

In addition to hydrogen, the pressurized charging device 30 receives a flow of depleted reversible metal hydride slurry 34. The depleted reversible metal hydride slurry can be a slurry that has not been hydrogenated (e.g., a newly formed slurry) and/or a slurry that has been at least partially dehydrogenated. Each is described in more detail below. Depleted reversible metal hydride slurries (sometimes referred to simply as depleted slurries, metal hydride slurries or slurries) comprise a metal hydride and an elemental metal in a form capable of accepting additional hydrogen to form a metal hydride. The ratio of metal hydride to elemental metal in the slurry can be 1.2 wt% or greater.

Other components may be included in the depleted metal hydride slurry, such as a carrier liquid (e.g., an organic carrier) and/or a dispersant (e.g., a triglyceride or polyacrylic acid (about 1%) or oleic acid (about 0.125%)) for stabilizing the slurry. The depleted slurry is drawn from a depleted reversible metal hydride slurry source (e.g., depleted metal hydride slurry storage device 46) by a pump 40 through a conduit 42 and forced into the charging device 30 through the depleted metal hydride slurry inlet 31.

The slurry in the pressurized charging device 30 is then heated using the heating coil 36. When the slurry is heated, the metal hydride in the slurry can be further charged with hydrogen gas 23, whereby the amount of hydrogen in the form of metal hydride in the metal hydride slurry increases. For magnesium hydride, the reaction rate is very low until the hydride temperature is above about 280 ℃, so heating the magnesium hydride to this temperature accelerates the initial reaction. The rate is then typically faster and the temperature and/or pressure may be reduced to control the rate of reaction. By this process, the depleted metal hydride slurry becomes a charged metal hydride slurry 38, as described below. The temperature to which the pressurized slurry is heated for charging can be in a wide range, depending on the metal hydride used in the slurry, for example, in the range of about 50 ℃ to about 350 ℃. For magnesium hydride, the range of charging is from about 250 ℃ to about 400 ℃ (e.g., from about 260 ℃ to about 300 ℃). The preferred temperature range will generally depend on the rate of reaction between the hydrogen and the depleted metal hydride.

Generally, the temperature and pressure used in the hydrogenation slurry will depend on each other and will depend on the type of metal used in the slurry. For example, magnesium hydride requires relatively high temperatures and pressures to hydrogenate the slurry at an acceptable rate; the equilibrium temperature of magnesium hydride at 1 atmosphere was 279 ℃. Other metal hydrides can generally achieve similar reaction rates at lower temperatures and/or pressures.

After charging, the charged reversible metal hydride slurry 38 is cooled, for example, to room temperature. The cooled charged metal hydride slurry 38 does not release significant amounts of hydrogen gas if its temperature remains within the cooling range and thus can be safely stored and/or transported. By "significant amount" of hydrogen is meant an amount large enough to significantly affect the energy available at the site of hydrogen evolution or the cost-effectiveness of using the slurry as an energy source, or to create storage and/or transportation difficulties, such as those created by the increase in pressure due to the production of hydrogen. For example, in some embodiments, the cooled charged metal hydride slurry releases no more than about 1% of its total hydrogen (e.g., no more than about 10%, no more than about 1%, or no more than about 0.1% of its total hydrogen). In some cases, it is believed that the amount of hydrogen released will be less (even much less) than 0.1%. The usable temperature range for charged metal hydride slurries that do not release significant amounts of hydrogen depends on the metal hydride used in the slurry. For magnesium hydride, the slurry will not produce significant amounts of hydrogen at temperatures below about 200 ℃ (e.g., below about 100 ℃, below about 80 ℃, below about 60 ℃, or below about 40 ℃). Other reversible hydrides should generally be kept at lower temperatures.

Once the slurry is charged, a pump 48 pumps the charged slurry 38 from the charged metal hydride slurry outlet 37 through a conduit 50 to a charged slurry storage facility 52 where the charged metal hydride slurry can be stored for extended periods of time. The charged slurry storage facility 52 has an outlet 56 so that slurry can be drawn into a slurry carrier 60 (here a tanker truck) by a pump 58. The slurry vehicle 60 may be any vehicle capable of carrying fluids over long distances, such as a motor vehicle, rail car, ship, barge, and pipeline or other conduit. The vehicle may be a truck of the type used for transporting gasoline. The pump 58 may be part of a service station (service station) that supplies trucks from a single dispenser or may be used to supply trucks with multiple dispensers.

The slurry carrier 60 transports the charged metal hydride slurry 38 (including the energy stored in the hydride in the form of hydrogen) from the first location 12 to the second location 62.

At the second location, the unloading station for the transported slurry includes a conduit 76, and a pump 73 draws the slurry from the transport apparatus through the conduit 76 and pumps it into a hydrogen-charged slurry tank 75. When hydrogen is required, the charged slurry is pumped from the charged slurry tank 75 by pump 74 through conduit 77 to the slurry inlet 72 and into the discharge apparatus 70.

The discharge device contains a heater 78 (e.g., a heating coil) to heat the slurry to a temperature at which the metal hydride of the slurry discharges hydrogen gas. The heating temperature depends on the hydrogen evolution characteristics of the metal hydride in the slurry. For magnesium hydride, the heating temperature is from about 250 ℃ to about 400 ℃ (e.g., about 290 ℃ to about 370 ℃ or about 320 ℃ and 360 ℃). Other hydrides may have different temperatures at which hydrogen is released. Typically, the temperature will be at least about 150 ℃ (e.g., at least about 80 ℃, at least about 100 ℃, at least about 125 ℃, at least about 175 ℃, at least about 200 ℃, at least about 225 ℃, at least about 250 ℃, at least about 275 ℃, at least about 300 ℃, at least about 325 ℃, at least about 350 ℃, at least about 375 ℃, or at least about 390 ℃) and/or at most about 400 ℃ (e.g., at most about 390 ℃, at most about 375 ℃, at most about 350 ℃, at most about 325 ℃, at most about 300 ℃, at most about 275 ℃, at most about 250 ℃, at most about 225 ℃, at most about 200 ℃, or at most about 175 ℃).

The discharge device will typically operate at a pressure determined by the discharge characteristics of the metal hydride and the system economics. For magnesium hydride, the highest hydrogen evolution rate occurs at pressures close to atmospheric pressure or lower. However, if hydrogen is provided at a pressure in the range of 30psia to 100psia, the hydrogen compressor is typically less expensive. In this case, the discharge device may be operated in the range of 30psia to 100psia to reduce the cost of the hydrogen compressor. The pressure range will typically be selected to minimize the cost of the system. For example, if hydrogen is being consumed by a fuel cell, the required pressure may only be 16-20 psia. In this case, the discharge device would likely operate at a pressure of 16 to 20psia eliminating the need for a hydrogen compressor.

The discharge device is designed to insulate against air and water, in particular oxygen and water. The charging device is also designed to exclude air and water because these substances will react with the metal hydride and prevent it from absorbing or desorbing hydrogen.

As the charged metal hydride slurry 38 is heated and the hydrogen gas 23 is evolved, the slurry becomes a depleted metal hydride slurry 34 (a metal hydride slurry that includes less than a significant amount of hydrogen, e.g., because some hydrogen has been evolved from the slurry or because the slurry is newly formed and has not been hydrogenated). The depleted reversible slurry is pumped by pump 84 through gas outlet 80 into slurry carrier 60 (which may be, for example, the same truck used to carry the charged slurry) for transport back to the first location 12 (or another recharging facility) for recharging.

The hydrogen gas 23 evolved from the charged metal hydride slurry 38 is discharged through a gas outlet 80 and collected, for example, in a hydrogen cylinder 90. The bottled hydrogen can then be used as an energy source to efficiently transport energy from, for example, a wind farm in kansas to, for example, new york where the energy demand is higher than in kansas. For example, bottled hydrogen may be used to power fuel cells in vehicles. For example, hydrogen gas may be emitted from a bottle into a fuel cell of a vehicle at a filling station, or the bottle itself may be placed in the vehicle and may be progressively injected into the fuel cell of the vehicle. The hydrogen gas can be bottled in gaseous or liquid form. In some cases, the hydrogen may be used for purposes other than as an energy source. For example, hydrogen gas may be used in laboratory studies as a carrier gas for gas chromatography, as a reactant in chemical reactions requiring hydrogen, or as a welding gas (e.g., instead of acetylene).

In some embodiments, the rechargeable metal hydride slurry can be used directly as a source of energy for vehicles, rather than as a source of bottled hydrogen. For example, the rechargeable metal hydride slurry can be pumped directly into the vehicle, for example, into a storage tank of the vehicle. The vehicle may have a hydrogen-emitting device located within the vehicle for emitting hydrogen gas for use as a fuel source for the vehicle. In some embodiments, the vehicle may also have a recharging device such that the rechargeable metal hydride slurry can be recharged within the vehicle itself. Hydrogen gas from a hydrogen source can be pumped into the charging device of the vehicle for hydrogenating the slurry.

In some embodiments, the reversible metal hydride slurry may be initially formed at the first location 12, for example, in the charging device 30. To this end, an inert liquid (e.g., mineral oil) 105 may be pumped from the inert liquid tank 100 through an inert liquid conduit 102 and into the charging device 36 with a pump 104. Also included is a storage container 106 for storing a metal hydride former 107, such as an elemental metal in powder form. The storage vessel 106 is connected to the charging device 30 by a conduit for transfer into the charging device 30. Alternatively, one or both of the storage vessel 106 and the inert liquid apparatus 100 may be detachable from the charging apparatus; the inert liquid 105 and/or hydride former 107 may then be added by hand to the charging device 30. Other slurry components (e.g., dispersant and/or hydrogenation catalyst) may be stored and added to the charging device 30 to form a slurry. Hydride former 107, inert liquid 105, and optional other ingredients may be combined in charging device 30 to form initial depleted slurry 34.

In some examples, the reversible metal hydride slurry may be initially formed at another location and transported by truck to the first location 12 for use.

Although only one first site having one charging device and one second site having one discharging device are shown in fig. 1, the first site may include a plurality of charging devices, the second site may include a plurality of discharging devices, and there may be a plurality of first sites and second sites, thereby forming a distribution network of energy obtained at some sites and used at other sites.

In some examples, the slurry generally includes a carrier liquid (e.g., an organic carrier), a dispersant (e.g., a triglyceride) for stabilizing the slurry, and a reversible metal hydride and/or a reversible metal hydride former (i.e., a metal and/or alloy of the metal hydride in elemental form) dispersed in the carrier liquid. The concentration of hydride and/or hydride former in the slurry is typically in the range of 40 wt.% to 80 wt.% (e.g., 50 wt.% to 70 wt.% or 55 wt.% to 60 wt.%). The concentration typically depends on the metal hydride selected for use in the slurry. The use of a denser metal hydride will produce a higher concentration of metal hydride than a less dense metal hydride. The denser metal hydride is one having a density of at least about 1 g/ml and includes, for example, lanthanum penta-nickelate (lanthanum-nickel), while the less dense metal hydride has a density of no greater than about 1 g/ml and includes, for example, lithium hydride. The magnesium hydride slurry can have a hydride concentration of at least about 50 wt% (e.g., at least about 55 wt%, at least about 60 wt%, at least about 65 wt%, at least about 70 wt%, or at least about 75 wt%) and/or at most about 80 wt% (e.g., at most about 75 wt%, at most about 70 wt%, at most about 65 wt%, at most about 60 wt%, or at most about 55 wt%). Generally, a higher percentage results in a higher energy density (i.e., the amount of energy that can be obtained from a given volume of slurry) while being generally more viscous and requiring more force to pump, while a lower percentage is generally less viscous, requiring less force to pump, but results in a lower energy density.

The slurry can be safely stored and transported, and the hydrogen can be easily extracted for use as a fuel. The slurry is typically not highly flammable or combustible and can be safely handled, stored and transported. The slurry is stable at normal ambient temperatures and pressures, for example, so that hydrogen does not dissociate from the hydride and evolve. Because it is a liquid, the slurry can be easily pumped through a conduit and into a storage tank, a transportation device, and/or a charging and discharging device.

The slurry includes a carrier liquid, such as an inert liquid in which the metal hydride and/or the reversible metal hydride former is suspended. "inert liquid" includes liquids which do not react with H at the temperatures and pressures at which they are used₂Or the metal hydride and/or the reversible metal hydride former chemically react and convert H₂Dissociation of molecules into atoms or prevention of recombination of atoms into H₂The catalytic ability of the molecule does not passivate the hydride or the liquid at the surface of the hydride former. The inert liquid is capable of dissolving a measurable amount of hydrogen.

In some examples the carrier liquid is an organic carrier liquid, such as mineral oil or a low molecular weight hydrocarbon, such as an alkane (e.g., pentane or hexane). Other carrier liquids may include fluorinated hydrocarbons (e.g., perfluorodecane), silicone based (silicaneaded) solvents, saturated organic liquids (e.g., undecane, isooctane, octane, and cyclohexane), or mixtures of high boiling hydrocarbons (e.g., kerosene), and mixtures thereof.

In some examples, the inert carrier liquid is a non-toxic light mineral oil that exhibits a high flash point in the range of about 154 ℃ to about 177 ℃ and a viscosity in the range of about 42 Saybolt Universal seconds (S.U.S.) to about 59 S.U.S.. Mineral oils do not chemically react with metal hydrides, produce a relatively low vapor pressure, and remain liquid over a temperature range of about-40 ℃ to 200 ℃. The carrier liquid makes the slurry pumpable and as a safe liquid, easy to store or transport. The carrier can act as a barrier between the hydride and atmospheric water, reducing the reaction of the two to form the hydroxide, which can reduce the ability of the slurry to store and release hydrogen. The use of a slurry allows for easy refueling, such as by filling the tank. Other carriers may also function, including carriers that do not have a water bond (water bond) and preferably do not have an OH bond. A silicone based carrier may also work with the slurry.

In some cases, the slurry includes a dispersant. For example, the dispersant may be a triglyceride dispersant, which sterically stabilizes the slurry. For example, the triglyceride dispersant may be a triglyceride of oleic acid or a triolein (triolein). Other dispersants that may be used include polymeric dispersants, such as poloxamer (Hypermer)^TMLP 1. The dispersant may be a polymeric dispersant. Combinations of triglycerides with polymeric dispersants may also be used, and combinations may be particularly useful if the hydride is magnesium hydride. Other dispersants include oleic acid, polyacrylic acid, and cetyltrimethylammonium bromide (CTAB). In some cases the dispersant can be present at a concentration of at least about 0.05% (e.g., at least about 0.1%, at least about 0.5%, at least about 0.75%, at least about 1.0%, at least about 1.5%, at least about 2.0%, at least about 2.5%, at least about 3.0%, or at least about 3.5%) and/or at most about 4.0% (e.g., at most about 3.5%, at most about 3.0%, at most about 2.5%, at most about 2.0%, at most about 1.5%, at most about 1.0%, at most about 0.75%, at most about 0.5%, or at most about 0.1%). For example, a blend comprising magnesium hydride, light mineral oil, and a mixture of 0.0625% CTAB and 1% polyacrylic acid forms a stable slurry. CTAB makes the slurry more flowable and polyacrylic acid helps to break up the magnesium hydride particlesThe seed remains in suspension. One function of the dispersant is to attach to the hydride particles, increasing the resistance of the particles in the carrier fluid, and thus helping to prevent settling. The dispersant also helps to prevent the particles from coalescing. The dispersant promotes slurry formation and stabilization of the hydride in the mineral oil. In certain embodiments the dispersant may also have surfactant properties, which may also be useful for slurry formation.

The metal hydride is typically a reversible metal hydride, such as a reversible metal or metal alloy hydride. A reversible hydride former (e.g., a reversible metal hydride former) is any substance (e.g., any metal or alloy) that is capable of reacting reversibly with hydrogen to form a hydride (i.e., capable of changing reversibly from a hydrogenated form to a non-hydrogenated form, typically depending on the conditions to which the slurry is subjected). The reaction (in simplified form) involves contacting gaseous hydrogen with a hydride former. In the case of metal hydride formers, this reaction can be represented as follows:

M+x/2H₂←→MH_x

where M is the metal hydride former and X is the number of hydrogen atoms in the final hydrogenated product. This reaction is sometimes described as an adsorption process, rather than a bonding process.

The reaction direction is determined by the hydrogen pressure and/or the reaction temperature. In some examples utilizing magnesium hydride, the hydrogenation of the metal requires a temperature of about 250 ℃ to about 400 ℃ (e.g., about 280 ℃ to about 350 ℃ or about 290 ℃ to about 320 ℃), while a temperature of about 280 ℃ to about 400 ℃ (e.g., about 300 ℃ to about 380 ℃, about 320 ℃ to about 360 ℃, or about 310 ℃ to about 340 ℃) results in the dehydrogenation of the metal. Other hydrides can operate at significantly lower temperatures and pressures, such as absorption and desorption temperatures of no greater than about 250 ℃ (e.g., no greater than about 225 ℃, no greater than about 200 ℃, no greater than about 175 ℃, no greater than about 150 ℃, no greater than about 125 ℃, no greater than about 100 ℃, or no greater than about 80 ℃). In certain embodiments, mixtures of alloys and/or hydrides may improve the kinetics and the temperature range of use. Examples of which are provided below. Generally, for the hydrogenation of metals, an increase in hydrogen pressure causes an increase in hydrogenation reaction (hydrogenation reaction) and/or a decrease in the temperature required for hydrogenation. In some cases, the hydrogen pressure is at least about 15psia (e.g., at least about 50psia, at least about 100psia, at least about 150psia, at least about 200psia, or at least about 250psia) and/or at most about 300psia (e.g., at most about 250psia, at most about 200psia, at most about 150psia, at most about 100psia, or at most about 50 psia). The pressure will typically depend in part on the temperature (and vice versa). For example, while magnesium hydride slurries produce relatively rapid hydrogen absorption at 300 ℃ at a pressure of 150psia, lower temperatures may also provide faster reactions.

Generally, it is desirable that the reaction be rapid to reduce costs. However, heat is generated during absorption and should be removed from the system. The high heat release rate can potentially break down the oil in the slurry. In certain embodiments, a combination of temperature and pressure parameters may be used to control the direction and speed of the reaction, and thus the amount of heat generated. For example, the pressure may initially be relatively low, and may subsequently increase as the process progresses.

Because the hydrogenation reaction (hydride reaction) is reversible, the slurry of hydride former can be used to repeatedly transport energy in the form of hydrogen, multiple charges and discharges (e.g., at least about 5 times, at least about 10 times, at least about 20 times, at least about 25 times, at least about 50 times, at least about 75 times, at least about 100 times, at least about 125 times, at least about 150 times, at least about 250 times, at least about 500 times, at least about 1000 times, or at least about 2000 times). Generally, the greater the number of hydrogen charge/discharge cycles, the more cost-effective the system. For example, on a large scale, a chemical hydride slurry used in an irreversible manner (e.g., where hydrogen is evolved by mixing a metal hydride with water to form hydrogen and a metal hydroxide; as disclosed in U.S. application No. 10/044,813 entitled "Storage, Generation, and Use of Hydrogen" filed on 2002, 11, 14, and incorporated herein by reference) should be capable of delivering hydrogen at a cost of about $ 4 per kilogram of hydrogen gas. If the reversible magnesium hydride slurry carries only half the hydrogen at the point of delivery, the cost of a single use of hydrogen would be about $8 per kilogram of hydrogen. However, if the reversible magnesium hydride slurry can be cycled 100 times, the cost of hydrogen will be reduced to about the cost of hydrogen used in the slurry and the transportation cost of the slurry (e.g., $1.65+ $0.10+ $8/100 $1.83 per kilogram). Any reuse of the hydride slurry in a reversible system will reduce the cost of hydrogen. In some instances, one limiting factor on the number of times the slurry can be charged and discharged is the slow formation of the oxide or hydroxide form of the chemical hydride former (e.g., caused by exposure to atmospheric moisture or air). Another problem that may limit the life of the metal hydride slurry may be damage to the oil and dispersant. These problems may affect how often the hydride slurry is returned to the plant for recycling. To recycle the hydride slurry, the oil is first separated from the solids. The solid is subsequently reformed to pure metal. The metal is then fused to form a fresh hydride former and the fresh hydride former is reacted with hydrogen to form a fresh hydride slurry.

In general, any reversible hydride former is suitable, including metal and/or metal alloy hydride formers, such as magnesium, vanadium, FeTi, CaNi₅、MgNi₂NaAl or other metal hydride formers (elemental metal, metal alloy or intermetallic material). The intermetallic hydride former comprises LaNi_4.5Al_.5、LaNi₅And TiFe_.7Mn_.2. The metal hydride former includes transition metals (groups IIIA through VIIIA of the periodic table), including the lanthanide and actinide series. They all have a large hydrogen storage capacity and release hydrogen easily at moderate temperatures and pressures, and are capable of undergoing many absorption and desorption cycles with little reduction in hydrogen storage capacity.

Metals and metal alloys known to form reversible hydrides that reversibly trap hydrogen include: titanium alloys as listed in U.S. patent No. 4,075,312, lanthanum alloys as disclosed in U.S. patent No. 4,142,300, and other alloys as shown in U.S. patent No. 4,200,623. Elemental metals known to form Metal Hydrides are described in w.m. muller (Mueller), j.p. blanklaki (blackridge) and g.g. liberwitz, "Metal Hydrides", Academic Press, new york (n.y.), 1968. These patents and references are incorporated herein by reference.

A slurry is initially formed by adding a reversible hydride former and optionally a dispersant to a carrier liquid. The reversible hydride former is typically finely ground prior to mixing with the other components of the slurry. In some cases, the reversible hydride former powder is first combined with a mixture of mineral oil and dispersant, which is then milled (e.g., in a pulverizer or mill) to further reduce the size of the particles. In some cases, the final particle is predominantly about 1 micron to about 200 microns in size on its smallest dimension (e.g., about 1 micron to about 100 microns or about 1 micron to about 50 microns). In some cases, a small amount of hydride (e.g., a hydride comprising the same reversible hydride former to be added to the slurry) is added to the slurry prior to charging the slurry. In some embodiments, the amount of hydride added to the hydride former is from about 1% to about 50% (e.g., from about 3% to about 20%). The most cost effective range will generally depend on the reaction rate and the cost of the hydride former. For magnesium hydride, the hydride may act as a catalyst, increasing the rate at which the hydride is formed by a reversible hydride formation, for example, as described in U.S. patent 5,198,207, which is incorporated herein by reference. In some cases, such as when the depleted slurry is one that has not been charged and has not been discharged, it is assumed that some of the hydride remains in the hydride form and provides the catalyst function without the addition of a chemical hydride as a catalyst.

Examples of slurries may have liquid-like flow characteristics that enable the use of existing liquid fuel infrastructure (infrastructure) in the storage and transportation of slurries. The nature of the carrier liquid, the amount of dispersant and the size of the hydride particles all affect the viscosity of the slurry. The oil in the slurry prevents the hydride from undesirably contacting the moisture in the air. The slurry can serve as a dissipation path for the heat generated by the exothermic charging reaction. The dispersant maintains the hydride particles in suspension. The dispersant adheres to the particles and spaces adjacent particles to prevent coalescence of the particles.

The slurry is only burned upon application (e.g., by a torch) and maintained at an elevated temperature. After the heat was removed, the combustion of the slurry stopped and the flame extinguished.

The slurry is generally capable of holding between about 3% and about 6% hydrogen by weight. In some embodiments the slurry can absorb up to 100% of the theoretical amount of hydrogen that can be absorbed. In certain embodiments, the slurry can release about 70% to about 98% of the absorbed hydrogen (e.g., about 80% to 98% or 90% to 98% of the absorbed hydrogen). The remaining residual hydride can then serve as a catalyst for recharging the slurry.

The charging device includes a vessel containing the slurry and a heating device (e.g., a heating coil, a heat exchanger, a heating plug, and/or a counter-flow heat exchanger) for heating the slurry therein to a charging temperature. The charging device also includes a hydrogen gas inlet and optionally a pressure regulator for maintaining a hydrogen charging pressure in the container. Because the charging reaction is exothermic, the charging apparatus may include a heat rejection device (e.g., a heat pump, heat exchanger, and/or plug) to maintain the slurry undergoing charging within a desired temperature range. The charging apparatus may also include a stirring or mixing assembly to create a more uniform temperature distribution throughout the slurry and to promote distribution of hydrogen throughout the slurry.

The charging device may be supplied with a freshly produced slurry, an exhausted slurry, or a combination of both slurries.

In some instances, such as in fig. 1, the charging apparatus is operated batch-by-batch. Spent slurry was pumped into the apparatus, the apparatus was heated and hydrogen was supplied until the slurry was charged. The pressure is vented, the slurry is cooled, and the slurry is pumped from the apparatus (e.g., to a storage tank). The process is then repeated.

In other embodiments, the charging apparatus is continuously (continuously) operated, as the slurry is continuously pumped, heated, charged, cooled, and removed.

As shown in fig. 2, in a continuous mode charging apparatus 150, a depleted metal hydride slurry 152 is fed by a pump 154 into a first section of piping 156 where it is heated to a charging temperature by heating coils 158. After heating, the depleted metal hydride is pumped into a pressure chamber 160, the pressure chamber 160 having a headspace 161 above the slurry 152. Hydrogen 162 is introduced into headspace 161 through gas inlet 163, wherein hydrogen 162 is in direct contact with surface 153 of slurry 152. Hydrogen 162 is introduced at a pressure (assuming a selected temperature) sufficient to initiate the hydrogenation reaction. In conjunction with the flow rate of the slurry, the pressure chamber 160 has a sufficient length/such that the lag time (lag time) of the slurry in the pressure chamber 160 is sufficient for the slurry to substantially complete charging. As the metal in the depleted metal hydride slurry 152 is hydrogenated to form a charged metal hydride slurry 168, the slurry gives up heat. Optional heat exchanger 166 collects heat and transfers the heat from the slurry into first section of tubing 156 where it assists in heating the depleted metal hydride slurry. Once fully charged, the slurry exits the pressure chamber 160 and enters the third section of tubing 172 where it is cooled to about room temperature, such as by heat exchanger 166. The charged metal hydride slurry is then pumped out of the charging device 150.

In a variant of this configuration, the method can be started by: some of the purge slurry is pumped through a counter-current heat exchanger and then through a heater (which will raise the temperature of the purge slurry to the operating temperature until there is sufficient heat from the charged slurry exiting the charging section) and then into the charging volume where the hydrogen gas will contact the slurry. The reaction between the depleted hydride and hydrogen will generate heat, and some of the heat should be actively rejected to maintain the slurry temperature at the desired reaction temperature. After several hours (a couple hours) in the hydrogenation zone, the hydrogenation should be complete and the charged hydride slurry is passed back through the counter-current heat exchanger and into a separate vessel for the charged slurry. Hot slurry passing through one side of the counter flow heat exchanger will have its heat transferred to cold depleted slurry passing through the other side of the counter flow heat exchanger.

Generally, a discharge device is similar to a charging device. The discharge device typically includes a container containing a fluid and a heating device (e.g., heating coils, heat exchangers, and/or heating plugs) for heating the slurry therein to a discharge temperature. If magnesium hydride is utilized, the hydrogen evolution temperature may be at least about 280 ℃ (e.g., at least about 300 ℃, at least about 320 ℃, at least 340 ℃, at least about 350 ℃, at least about 360 ℃, at least about 370 ℃, at least about 380 ℃, or at least about 390 ℃) and/or at most about 400 ℃ (e.g., at most about 390 ℃, at most about 380 ℃, at most about 370 ℃, at most about 360 ℃, at most about 350 ℃, at most about 340 ℃, at most about 320 ℃, or at most about 300 ℃). Other hydrides can operate at lower temperatures and pressures. The apparatus further comprises a hydrogen outlet for releasing hydrogen from the vessel. The discharge apparatus optionally further comprises a heat rejection device (e.g., a heat pump, heat exchanger, or adiabatic counter-flow heat exchanger) to lower the temperature of the slurry after the slurry is depleted of releasable hydrogen.

In some instances, such as in fig. 1, the discharge device is operated batch-by-batch. The hydrogen-charged slurry was pumped into the apparatus and heated, at which time hydrogen gas was evolved from the slurry. The depleted slurry is then optionally cooled and pumped from the apparatus (e.g., to a storage tank). The process is then repeated.

In some examples, the charged slurry is continuously pumped to a discharge device, heated, depleted, cooled, and removed. Fig. 3 illustrates an example of a continuous mode discharge apparatus 200 in which a charged metal hydride slurry 202 is fed by a pump 204 into a first section of tubing 206 where it is heated to a desorption temperature using heating coils 208. After heating, the charged metal hydride slurry 202 is passed into a desorption chamber 210, the desorption chamber 210 having a headspace 211 above the surface 203 of the slurry 202. Hydrogen gas 212 is desorbed from the charged slurry 202 into the headspace 211 from which it is discharged through the gas outlet 212. Pressure valve 214 may be used to control the pressure within headspace 211. In conjunction with the flow rate of the slurry, the length l' of the desorption chamber 210 conduit is sufficient to desorb substantially all of the available hydrogen. The slurry (now depleted metal hydride slurry 216) exits the desorption chamber 210 and enters a third section of piping 220 where it is cooled to about room temperature, optionally using a heat exchanger 222 that absorbs heat from the depleted metal hydride slurry 216 and imparts it to the charged metal hydride slurry 202 entering the discharge device 200. The depleted metal hydride slurry 216 is then pumped (e.g., stored and/or transported) out of the discharge device 200.

The pressure valve 214 may be connected in some cases with a cooling system 226 to cool the hydrogen gas 212 and condense any oil 228 that has volatilized and is vented with the hydrogen gas 212. Any oil 228 so condensed can be added back to the depleted metal hydride slurry 216. In some cases, the hydrogen gas 212 may pass through a filter 230 (e.g., a charcoal filter) to remove any remaining oil or other impurities. The now purified hydrogen 212' may then be sent for further processing (e.g., bottling). Alternatively, the hydrogen gas 212' may be supplied to a hydrogen-consuming process (e.g., a fuel cell or a welding system).

Typically, a first energy source is used to form or extract hydrogen that is stored in a hydride slurry. In some instances the first energy source is an energy source that is readily available at a particular location (e.g., the first location) and/or is not readily available at the second location and/or is not readily transferable to the second location. These energy sources include renewable energy sources in the form of heat or electricity, such as wind energy, geothermal energy, hydroelectric energy, ocean energy (e.g., using ocean waves, tidal energy, or using thermal energy stored in the ocean), biological energy, and solar energy. These energy sources do not typically produce greenhouse gases and are not subject to exhaustion. Biomass produces greenhouse gases, but typically does not add significant amounts of additional greenhouse gases to the atmosphere because biomass uses greenhouse gases to form itself. In some embodiments, nuclear energy may be used to generate hydrogen. In other embodiments, fuels commonly used as energy sources (e.g., coal, oil, and/or natural gas) may be used to generate hydrogen. Hydrogen can be produced at small locations where care should be taken to reduce the pollution caused by the combustion of these fuels.

Unlike fossil fuels, many of these energy sources are not themselves readily transportable in an unused and/or stable form. In addition, many of these energy sources are located in locations where energy demand is low (e.g., areas with low population density and/or low levels of industrialization). For example, as illustrated in FIG. 1, the first site 12 (Kansas) has abundant available wind energy, but has a lower energy demand than other areas of the United states. In some locations, the available energy is greater than the energy demand. This excess energy can be stored and transported to locations of higher energy demand.

Example 1

A mixture of 50 wt% magnesium hydride and Paratherm NF heat transfer oil was placed in a barter autoclave (Parr autoclave) where it was subjected to the following experimental conditions. A graph of the temperature and pressure of the autoclave as a function of time can be seen in fig. 4.

The autoclave was purged five times with hydrogen at a pressure of 150psia to reduce the oxygen content of the gas in the vessel to no more than about 2 ppm. The pressure in the vessel was reduced to atmospheric pressure after each pressurization and after the last pressurization. The vessel is heated to 140 c at which temperature any water in the oil reacts with the magnesium hydride to form hydrogen gas. The resulting pressure rise will cause the produced hydrogen gas to leave the container and be collected in an inverted bottle filled with water; no bubbles were observed, indicating the absence of water in the oil.

The vessel was heated to 370 ℃ (the temperature at which hydrogen desorbs from the magnesium hydride) and hydrogen evolution was seen for about 2 hours, during which time about 80% of the hydrogen theoretically bound in the magnesium hydride was evolved. The evolved hydrogen gas was measured in an inverted bottle that displaced the water in the bottle.

The autoclave was then pressurized with 150psia of hydrogen while maintaining the temperature at about 370 ℃. The pressure dropped only a few psi over the course of 1.4 hours, indicating that the slurry absorbed little hydrogen. The temperature was then reduced to about 320 ℃. At which hydrogen is readily absorbed (i.e., readily incorporated into the magnesium hydride). The system was held at this condition for 1.5 hours with an additional hydrogen pressurization and subsequent cooling.

As can be seen in the graph of fig. 4, the slurry did not evolve hydrogen (indicated by a pressure near 0psia) when initially heated to about 370 ℃. A set amount of hydrogen was introduced, indicated by an increase in pressure to about 150psia at about 10000 seconds. At this temperature and pressure, the slurry does not absorb hydrogen (indicated by the pressure remaining at about 150psia over time). Once the temperature is reduced to an absorption temperature of about 320 ℃, the pressure drops, indicating that hydrogen is absorbed by the slurry. The rate of pressure decrease increases with time. This is believed to be the effect of the initially formed magnesium hydride acting as a catalyst, which accelerates the hydrogenation reaction (hydrideaction) and utilizes hydrogen gas at a faster rate. After more hydrogen was added to the system (indicated by the spike in pressure at about 18000 seconds), the rate of pressure decrease (indicative of the rate of hydrogen uptake) increased again, only decreasing as the temperature decreased at the end of the experiment.

Although the embodiments described above generally relate to the formation of hydrogen gas at or near a metal hydride formation or charging site, the hydrogen gas itself may be stored and transported to the metal hydride charging site. For example, hydrogen can be transported from a large scale steam methane reforming plant to a distant market (e.g., a market hundreds of miles away).

Other embodiments are within the scope of the following claims.

Claims (30)

1. A method of storing and/or transporting hydrogen gas, comprising:

pumping a pumpable hydrogen storage fluid into a discharge device, said pumpable hydrogen storage fluid comprising an inert fluid and a reversible hydride former, said reversible hydride former comprising a hydrogenated reversible hydride former, said pumpable hydrogen storage fluid not significantly evolving hydrogen gas at room temperature and pressure, wherein said pumpable hydrogen storage fluid is a slurry; and

heating the pumpable hydrogen storage fluid in the discharge device under anhydrous conditions to release hydrogen from the hydrogenated reversible hydride former and form an unhydrogenated reversible hydride former.

2. The method of claim 1, wherein the hydrogen-evolving device is designed to be insulated from oxygen and water.

3. The method of claim 1, wherein the unhydrogenated reversible hydride former is enabled to be rehydrogenated by combining the pumpable hydrogen storage fluid with hydrogen gas under pressure.

4. The method of claim 1, wherein 80% or more of the reversible hydride former of the pumpable hydrogen storage fluid is hydrogenated reversible hydride former when the pumpable hydrogen storage fluid is pumped into the discharge device.

5. The method of claim 1, wherein the unhydrogenated reversible hydride former comprises a metal or metal alloy.

6. The method of claim 5, wherein the unhydrogenated reversible hydride former is magnesium metal.

7. The method of claim 1, wherein the hydrogenated reversible hydride former is a metal hydride.

8. The method of claim 7, wherein the metal hydride is magnesium hydride.

9. The method of claim 1, wherein the pumpable hydrogen storage fluid comprises magnesium, magnesium hydride, mineral oil and a dispersant.

10. The method of claim 1, wherein the pumpable hydrogen storage fluid comprises a dispersant selected from the group consisting of: triglycerides, polyacrylic acid, a combination of triglycerides and polyacrylic acid, or oleic acid.

11. The method of claim 1, further comprising hydrogenating a reversible hydride former in the pumpable hydrogen storage fluid prior to pumping the pumpable hydrogen storage fluid into the hydrogen discharge apparatus.

12. The method of claim 11, wherein hydrogenating the reversible hydride former comprises using electricity or heat to produce hydrogen gas, and combining the hydrogen gas with the pumpable hydrogen storage fluid under pressure in a charging device, wherein combining the hydrogen gas with the pumpable hydrogen storage fluid comprises heating the pumpable hydrogen storage fluid to 50 to 350 ℃ and maintaining the pressure at least 150 psia.

13. The method of claim 1, wherein heating the pumpable hydrogen storage fluid in the hydrogen discharge apparatus under anhydrous conditions comprises heating the slurry to 250 ℃ -400 ℃, wherein the reversible hydride former is a magnesium hydride former.

14. The method of claim 1, wherein the hydrogen discharge apparatus is located within a vehicle and the discharged hydrogen is used as an energy source for the vehicle.

15. The method of claim 1, wherein said pumpable hydrogen storage fluid comprises said reversible hydride former at a concentration of 40 to 80 weight percent.

16. A system for storing and/or transporting hydrogen gas, comprising:

a pumpable hydrogen storage slurry comprising an inert fluid and a reversible hydride former having a hydrogenated state and an unhydrogenated state, said pumpable hydrogen storage slurry not significantly evolving hydrogen gas at room temperature and pressure when said reversible hydride former is in the hydrogenated state;

at least one charging device adapted to place the unhydrogenated reversible hydride former of the pumpable hydrogen storage slurry in a hydrogenated state,

at least one discharge device adapted to heat the pumpable hydrogen storage slurry under anhydrous conditions to release hydrogen from the hydrogenated reversible hydride former and form an unhydrogenated reversible hydride former.

17. The system of claim 16, wherein the hydrogen-evolving device is designed to be insulated from oxygen and water.

18. The system of claim 16, wherein the charging device is connected to an electrolyzer that extracts hydrogen from water using energy from a first energy source at a first location, wherein the charging device comprises a slurry inlet, a slurry outlet, and a heating device capable of heating the slurry in the charging device to at least 320 ℃, wherein the charging device is capable of maintaining a pressure in the charging device of at least 150 psia.

19. The system of claim 18, further comprising a storage vessel connected to the slurry outlet.

20. The system of claim 16, wherein the charging apparatus includes a regulator to maintain a temperature of a slurry contained in the charging apparatus at no greater than 350 ℃.

21. The system of claim 16, wherein the discharge device is capable of heating the pumpable hydrogen storage slurry to at least 370 ℃.

22. The system of claim 16, wherein the discharge device comprises a hydrogen outlet through which hydrogen gas discharged from the hydride slurry can pass.

23. The system of claim 16, wherein the charging device is at a first location, the discharging device is at a second location, and the first location is remote from the second location.

24. The system of claim 23, further comprising a slurry vehicle transporting said pumpable hydrogen storage slurry from said first location to said second location, wherein said slurry vehicle is selected from the group consisting of trucks, boats, rail cars, pipelines, and any combination of these vehicles.

25. The system of claim 16, wherein the reversible hydride former comprises a metal or metal alloy in an unhydrogenated state, wherein the reversible hydride former comprises a metal hydride in a hydrogenated state.

26. The system of claim 25, wherein the unhydrogenated reversible hydride former is magnesium metal, wherein the metal hydride is magnesium hydride.

27. The system of claim 16, wherein the pumpable hydrogen storage slurry comprises the reversible hydride former at a concentration of 40 to 80 weight percent.

28. The system of claim 16, wherein the pumpable hydrogen storage fluid comprises magnesium, magnesium hydride, mineral oil and a dispersant, wherein the dispersant is selected from the group consisting of: triglycerides, polyacrylic acid, a combination of triglycerides and polyacrylic acid, or oleic acid.

29. The system of claim 16, wherein the hydrogen discharge apparatus is located within a vehicle and the discharged hydrogen is used as an energy source for the vehicle.

30. The system of claim 16, wherein the pumpable hydrogen storage slurry is adapted to be charged from one or more charging devices and depleted from one or more discharging devices for at least 50 cycles.