A method and system for storing grid electricity and distributing the stored electricity on demand

Abstract

The present invention relates to a method for supplying electricity to an electrical load, the method comprising the steps of supplying an alkaline solution, reacting the alkaline solution with silicon to generate hydrogen, processing the hydrogen in a fuel cell to produce electricity, and supplying the electricity from the output of the fuel cell to the electrical load via a suitable electrical interface module.

Description

Cross-Reference to Prior Applications

[0001] This application claims the priority of Australian Provisional Patent Application No. 2022901973, filed on July 14, 2022. The entire disclosure thereof is incorporated herein by reference.

Technical Field

[0002] The present invention relates to the field of energy storage and power generation using hydrogen as a fuel source. Background of the Invention

[0003] Any discussion of prior art in this specification should not be regarded as an admission that such prior art is well known or forms part of the common general knowledge in the art.

[0004] The increasing use of renewable energy sources has been considered as a way to decarbonize the modern energy ecosystem. However, renewable energy sources are intermittent energy sources and cannot provide a stable, consistent, and reliable energy supply. Furthermore, certain renewable energies such as solar power generation cause over-generation of electricity during the day and require demand response to consume the surplus electricity. If the demand cannot balance the power supply, it will lead to the curtailment (i.e., underutilization) of renewable energy sources. For example, the world's largest wind farm in Gansu Province, China, only operated at 60% capacity throughout 2019 to avoid curtailment. Conversely, when people return home from work at the end of the day, the distributed energy demand on the power grid increases, and it is difficult to meet this increased energy demand because solar power generation stops during that time period. Pumped hydroelectric energy storage is currently the only grid-scale energy storage method, but it is limited by geographical location, the size of the storage facility directly related to the length of energy release, and seasonality. Hydrogen technology has been developed, but due to issues related to the cost, safety, scalability, storability, and transportability of hydrogen as a grid-scale energy source, fossil fuels and nuclear power still remain as an essential part of the energy ecosystem. Thermal energy storage is another area that has attracted attention to address intermittent energy sources. Currently, molten salt TES is the most used technology in this field due to its high technological maturity and application to concentrating solar power (CSP) plants. According to the U.S. Department of Energy's database on global energy storage, pumped hydroelectric energy storage accounts for 96% of the world's current storage capacity, with the remainder being thermal storage (1.6%), electrochemical batteries (1.1%), and mechanical storage (0.9%) (U.S. Department of Energy, n.d.). However, it should be noted that these figures do not include distributed small-scale storage such as household water heaters and batteries. SUMMARY OF THE INVENTION

[0005] The present invention aims to solve at least one of the above problems.

[0006] The present invention can include several broad forms. Embodiments of the present invention can include one or any combination of different broad forms described herein.

[0007] In a first broad form, the present invention provides a method of supplying electricity to an electrical load (e.g., a power grid). The method comprises (i) providing an alkaline solution; (ii) reacting the alkaline solution with silicon to produce hydrogen; (iii) processing the hydrogen in a fuel cell to produce electricity; and (iv) supplying the electricity from the output of the fuel cell to the electrical load via a suitable electrical interface module comprising.

[0008] Preferably, the silicon may comprise one or more portable units of silicon.

[0009] Preferably, the silicon may comprise porous silicon.

[0010] Preferably, the porous silicon (i) alloying silicon with at least one distillable alloying metal (e.g., zinc, magnesium, cadmium, antimony, or calcium) to form an alloy; (ii) reducing or minimizing oxidation of the alloy by grinding, crushing, or milling the alloy in a chamber of an inert or near-inert environment to form alloy pellets or particles; and (iii) distilling the alloying metal from the alloy pellets or particles to produce a porous structure may be manufactured according to.

[0011] Optionally, after step (iii), a further step of grinding, crushing, or milling the porous silicon structure to break it down into porous silicon particles may be carried out.

[0012] Optionally, after step (iii), a further step of compressing the porous silicon structured particles to form pellets may be carried out.

[0013] Preferably, the present invention may include a step of supplying hydrogen generated by the porous silicon to the fuel cell. This fuel cell is then converted into electricity. This electricity can then supply power to various applications and scenarios such as electrical loads and power supply to the grid. Further, the present invention can be used for on-demand hydrogen supply for powering hydrogen electric vehicles, thereby reducing the need for pressurized containers and cryogenic storage and transportation of hydrogen.

[0014] Preferably, the present invention may include a step of constructing a thermal energy system using the heat from the dissolution of NaOH, the heat generation from the hydrogen generation reaction, and the heat of the fuel cell. This heat can be used to supplement power supply in places where heat is required, such as commercial laundering, home heating, and aquifer thermal energy storage systems.

[0015] Preferably, the step of controllably supplying electricity may include charging a battery module using at least a portion of the electricity from the output of the fuel cell. This charged battery module is configured to function as a buffer between the fuel cell and the load, or to supply an appropriate amount of electricity to the electrical load to supplement the electricity directly supplied from the output of the fuel cell to the electrical load, or to be configured to apply the electrical interface module.

[0016] Preferably, the battery module may include a new battery module or a used EV battery.

[0017] In another broad form, the present invention provides a method of converting electricity received from a power source such as the power grid into an energy storage material, the method comprising: (i) receiving electricity from the power source; and (ii) Using the received electricity to perform carbothermal reduction of quartz to produce silicon and including wherein the silicon can be stored for later on-demand use to release energy by reacting the silicon with an alkaline solution to produce hydrogen and heat. Preferably, the silicon may be metallurgical grade silicon or other silicon sources that may have a purity greater than 98% to produce porous particles / pellets / structures as described above. Alternatively, in the above carbothermal reduction step, silica may be used instead of quartz.

[0018] In another broad form, the present invention provides a system for providing electricity to an electrical load, the system being operable to perform any one of the steps according to the first broad form of the present invention.

[0019] In another broad form, the present invention provides a portable unit of silicon configured to be used according to any one of the steps of the first broad form of the present invention.

[0020] In another broad form, the present invention produces a grid storage material capable of simultaneously generating electricity and heat on demand.

Brief Description of the Drawings

[0021] The present invention will be more fully understood from the following detailed description of preferred but non-limiting embodiments described in connection with the accompanying drawings.

[0022] FIG. 1 shows a process flowchart of a method for producing electricity from hydrogen generated on demand using porous silicon, whereby the produced electricity can support a power grid according to an embodiment of the present invention.

[0023] Figure 2 shows a process flowchart of a method for manufacturing porous silicon that is stored in a portable unit and can then be used to generate hydrogen on demand according to an embodiment of the present invention.

[0024] Figure 3 shows a system for generating hydrogen from porous silicon according to an embodiment of the present invention.

[0025] Figure 4 shows a system for producing electricity from hydrogen for delivery to an electrical grid and charging a battery module according to an embodiment of the present invention.

[0026] Figure 5 shows a comparison of the hydrogen generation capabilities of porous silicon and non-porous solid silicon.

[0027] Figure 6 shows an exemplary process schedule for semi-autonomously generating hydrogen from porous silicon according to an embodiment of the present invention. Detailed description

[0028] Here, preferred embodiments of the present invention will be described with reference to FIGS. 1 to 6. The exemplary embodiments store and utilize a portable unit of porous silicon (e.g., formed into an ingot, pellet, or other particulate structure) to generate hydrogen on demand, and then use that hydrogen to produce electricity for supplying an electrical load. These exemplary systems and methods also serve to control the amount of electricity supplied to the electrical grid by storing a portion of the electricity generated from hydrogen in a buffer battery module (either a new battery module or a used EV battery module), whereby the electricity from the battery module is supplied to the electrical grid during peak times and can help meet the load demand on the electrical grid during peak loads. In these embodiments, the electrical grid may be composed of, for example, an electrical grid for supplying electricity to a town or city, or may be composed of a smaller-scale electrical grid such as a microgrid for supplying electricity to a home, neighborhood, building, or other small-scale system.

[0029] FIG. 1 shows a process flowchart of a method for supplying electricity to a power grid according to the following embodiment: (i) storing an amount of porous silicon in one or more portable units (100); (ii) reacting the porous silicon with an alkaline solution to produce hydrogen (110); (iii) processing the hydrogen in a fuel cell to produce electricity (120); and (iv) supplying the electricity from the output of the fuel cell to the power grid via a suitable electrical interface module (130).

[0030] Furthermore, in this exemplary method, the porous silicon used to produce hydrogen on demand is produced according to the process flowchart of the method shown in FIG. 2 below: (i) silicon is alloyed with at least one distillable alloying metal selected from at least one of zinc, magnesium, cadmium, antimony, or calcium to form an alloy (200); (ii) pellets, particles or structures of the alloy are formed in a chamber of an inert environment to reduce or minimize oxidation of the alloy. Usually, the step of forming the pellets, particles or structures of the alloy may include a step of grinding, crushing or milling the alloy, for example, in a particular embodiment, a spraying or sintering step to form alloy particles with a diameter of about 100 nm to 150 nm; (iii) distilling the alloying metal from the alloy particles to produce a porous silicon structure (220).

[0031] In this exemplary method, hydrogen is generated from porous silicon using a system that includes a physical apparatus as shown in FIG. 3. The exemplary closed-loop system includes a water supply unit (300), a caustic dissolution tank (310), a hydrogen reactor (320), a thermoelectric generator (330), a first solid-liquid separator module (340), a sedimentation tank (350), and a second solid-liquid separator module (360). The clarified solution from the second solid-liquid separator module (360) can be concentrated and recycled to the caustic dissolution tank (310). This closed loop maximally stores NaOH and water throughout the H2 generation process. The detailed process will be further described in more detail below. Manufacture of Porous Silicon

[0032] In this exemplary embodiment, the porous silicon is produced from the material of the raw silicon. First, the material of the raw silicon is alloyed with any alloying metal that can be distilled from the alloy using an alloying device, such as magnesium, zinc, calcium, or antimony. This step is represented by (200) in FIG. 2. In these embodiments, the alloying metal used is magnesium. Since magnesium is highly flammable at high temperatures, the process of alloying magnesium with the material of the raw silicon is carried out in a vacuum or a controlled environment. This alloy is formed in a ratio of approximately 53% (atomic ratio) silicon and approximately 47% magnesium. Different ratios of silicon may be used. However, using this ratio, the size of the final porosity of the silicon particles can be controlled. Zinc, or a combination of both magnesium and zinc, can also be used as the alloying metal in other embodiments since the metal is distillable in both situations. Once the alloy is formed, it usually takes the form of an ingot or other particulate structure.

[0033] In certain embodiments, it may be possible to form alloy particles from a liquid melt by using a metallurgical atomization process. Advantageously, according to this method, the particle size of the alloy particles can be appropriately controlled, overcoming the problem that magnesium boils during solidification to generate magnesium vapor, which solidifies as highly explosive magnesium fine particles.

[0034] The alloy particles are preferably formed by a spraying method, and the resulting alloy particles will be in the range of several hundred microns. This step is represented by (220) in Figure 2. Preferably, these micron-sized particles are further sintered to form pellets, which can increase the recovery rate of the porous silicon material from the distillation process. As can be understood, the larger the pellets, the longer the distillation time. The distillation process is carried out by transferring the alloy particles into a vacuum furnace. Then, the temperature in the vacuum furnace is raised to distill the alloying metal from the alloy. The distillation temperature needs to be controlled below the melting point of the virgin alloy.

[0035] The distillation process can advantageously control the porosity of the final particles produced by creating pores within the silicon particles and using different percentages of Mg or Zn (e.g., distillable metals) in the alloy. The presence of these pores on the surface of the silicon particles, or an increase in the size and / or number of the pores, is particularly useful when the porous silicon particles react with an alkaline solution to produce hydrogen, and can produce hydrogen more efficiently compared to reacting non-porous or low-porosity silicon particles of the same mass / volume with an alkaline solution. The reasons are as follows: 1. When the material is passivated, there is more bulk elemental silicon relative to the surface oxide, and more hydrogen is produced compared to micron / nano-sized silicon particles. 2. Since the porosity of silicon is independent of the particle size, the porous silicon particles can be made to be in the size of mm or cm, which is clearly advantageous in terms of handling and use. Small particles may be susceptible to the influence of "necking" in various supply systems. 3. The large surface area of the porous silicon enables a continuous and complete reaction with the basic solution, and the generated hydrogen can be effectively controlled. 4. The complete reaction of the porous silicon also enables a high recovery of the silicate by-products of the hydrogen generation reaction, and the carbon footprint of this porous silicon hydrogen generation system is significantly reduced compared to other forms of hydrogen generation technologies / solutions.

[0036] In certain embodiments, any additional steps may be performed after distillation. Thus, to break down the porous structure composed of silicon particles (i.e., by ball milling or any other suitable process to break the particle structure into smaller particles), the obtained porous silicon particles may be further processed in a controlled environment. In these embodiments, the controlled environment includes filling the milling chamber with an inert gas such as argon and / or helium or a small amount of nitrogen. The distillation step can advantageously create pores within the silicon particles and control the porosity of the final particles produced by using different proportions of distillable metals in the alloy, such as Mg or Zn. The presence of these pores on the surface of the silicon particles, or an increase in the size and / or number of the pores, can be particularly useful when the porous silicon particles react with an alkaline solution to produce hydrogen. Also, hydrogen can be produced more efficiently compared to reacting non-porous or less porous silicon particles of the same mass / volume with an alkaline solution.

[0037] In certain alternative embodiments, the process of generating porous silicon particles from a source silicon material may involve a different series of processing steps. The source silicon material is first alloyed with an alloying metal such as magnesium or zinc to form an alloy ingot or other particulate structure. The alloy ingot is distilled to produce a porous, substantially pure silicon particle / pellet / ingot / structure. Before distilling the alloy ingot, the ingot may first be processed to form pellets. In certain embodiments, the pellets may have a diameter of about 1 cm.

[0038] The porous silicon particles may be stored in a portable unit for treatment with water or an alkaline solution (as further described below) to generate hydrogen on demand. The porous silicon may be formed as an ingot or other large structure, depending on its suitability for storage and / or transport. The storage and transportability of silicon solves an important problem that has hindered the wider introduction of hydrogen-based energy source technologies, in that silicon can be stored and transported relatively easily, react readily with an alkaline solution to produce hydrogen, and that hydrogen can be used on demand for power generation.

[0039] Standard blue barrel (42 gallons) of crude oil has a heating value of 1670 kWh when completely burned, while the recoverable energy stored in the same volume of porous silicon (filling density of about 50%) is 1562 kWh (i.e., 981 kWh as hydrogen from reaction with an alkaline solution and 581 kWh as heat). This is far higher than existing major hydrogen storage solutions, namely compressed hydrogen (316 kWh at 500 MPa storage), liquefied hydrogen (448 kWh at 21.2 K), highly toxic liquefied ammonia (557 kWh at 240 K), solid (zero void) sodium borohydride (663 kWh), and highly flammable magnesium hydride (695 kWh). Needless to say, the porous silicon has the property of being easily transportable at room temperature without the need for high-pressure compression or cryogenic cooling during the transport and storage processes. Generation of Hydrogen from Porous Silicon Particles

[0040] In these embodiments, hydrogen is generated according to a process having the following steps: (a) Provide an alkaline solution. (b) React the alkaline solution with porous silicon to generate hydrogen.

[0041] This process may further include the following: (c) Separate solids from the alkaline solution.

[0042] This process may further include the following: (d) Separate dissolved silicate from the alkaline solution.

[0043] This process may further include the following: (d1) Precipitate dissolved silicate from the alkaline solution to provide precipitated silicate; and (e) Separate the precipitated silicate from the alkaline solution.

[0044] An exemplary process includes reacting an alkaline solution with silicon to produce hydrogen gas. When using sodium hydroxide to produce the alkaline solution, the following reaction occurs in step (b) above: Si + 2H2O → SiO2 + 2H2 Equation 1 SiO2 + 2NaOH → Na2SiO3 + H2O Equation 2

[0045] In some embodiments, step (a) may include providing the alkaline solution by mixing water with a water-soluble hydroxide (such as ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, etc.). The water may be wastewater (e.g., gray water, etc.), rainwater, natural surface water (e.g., seawater, lake water, or rainwater, etc.), groundwater, tap water, or distilled water.

[0046] The temperature of the alkaline solution in step (a) and / or step (b) is preferably from about 20°C to about 80°C. In another embodiment, by utilizing the low melting point of the aqueous caustic solution with a eutectic melting point of about -33.4°C for the alkaline solution containing 20% NaOH, the temperature of the alkaline solution in step (a) and / or step (b) can be less than 0°C. This eliminates the need for antifreeze when the process is carried out in a cold environment.

[0047] The heat generated during the mixing of water and the hydroxide may be used to raise the temperature of the alkaline solution to the desired temperature, and the excess may be recovered. In some embodiments, this excess heat may be recovered and transferred to a thermoelectric generator, a heat exchanger, or other auxiliary units that utilize heat.

[0048] The heat generated during the reaction of the alkaline solution and silicon may be used to raise the alkaline solution in step (b) to the desired temperature, and the excess may be recovered. In some embodiments, this excess heat may be recovered and transferred to a thermoelectric generator (330), a heat exchanger, or other auxiliary units that utilize heat. In other embodiments, the excess heat generated in any part of the process may be recovered via a thermoelectric generator. In some embodiments, the silicon is micro- or nano-porous silicon. In one embodiment, the silicon is in the form of micron-sized porous particles.

[0049] The impurities and / or dopants of the porous silicon material can advantageously enhance the reactivity and / or protect the porous silicon from light oxidation.

[0050] The degree of reaction and dynamics of the present system can be controlled by controlling the amount of water, the active substance, the type and concentration of the basic / caustic solution, and the reaction temperature.

[0051] In some embodiments, the silicon has one or more of the following characteristics: · Specific surface area (SSA) measured by N2 physical adsorption (BET method): at least 1.5 m 2 / g, 1.6 m 2 / g, 1.7 m 2 / g, 1.8 m 2 / g, 1.9 m 2 / g, 2.0 m 2 / g, or 2.1 m 2 / g; or surface area: about 2.0 m 2 / g to about 2.5 m 2 / g, or about 2.0 m 2 / g to about 2.4 m 2 / g, or about 2.0 m 2 / g to about 2.3 m 2 / g, or about 2.0 m 2 / g to about 2.2 m 2 / g, or about 2.1 m 2 / g to about 2.2 m 2 / g, or about 1.9 m 2 / g to about 2.3 m 2 / g, or about 2.1 m 2 / g. · Aggregate particle size distribution: one or more of D10 0.512 μm, D25 1.115 μm, D50 2.305 μm, D75 3.980 μm, or D90 5.842 μm. · Average pore volume: about 0.004 mL / g to about 0.007 mL / g, or about 0.005 mL / g to about 0.006 mL / g, or up to about 0.01 mL / g. · Average pore diameter (4V / A by BET method): about 0.5 nm to about 50 nm, or about 0.5 nm to about 25 nm, or about 1 nm to about 20 nm, or about 10 nm to about 15 nm, or about 11 nm to about 15 nm, or about 12 nm to about 15 nm, or about 12 nm to about 14 nm, or about 11 nm to about 13 nm, or about 11 nm to about 12 nm. · SSA measured by BET method: about 0.85 m 2 / g to about 2.5 m 2 / g (corresponding to a particle size of 0.5 mm to 5 mm).

[0052] A method for preparing porous silicon that can be used in the process of the present disclosure is described in WO2018019266, the disclosure of which is incorporated herein by reference in its entirety.

[0053] Figure 5 shows a comparison of the hydrogen generation capabilities of porous silicon (denoted as "EAT-Si") and non-porous solid silicon (denoted as "solid-Si").

[0054] The silicon of EAT-Si has the following characteristics: ·SSA measured by N2 physical adsorption (BET method): about 2.1 m 2 / g; particle size distribution: D10 0.512 μm, D25 1.115 μm, D50 2.305 μm, D75 3.980 μm, or D90 5.842 μm. ·SSA measured by N2 physical adsorption (BET method): about 0.85 m 2 / g, particle size: 5 mm.

[0055] Following the reactions shown in the above formulas 1 and 2, (when the dissolved concentration in the liquid exceeds the solubility limit,) unreacted solids such as silicon, undissolved SiO x and undissolved silicate in the alkaline solution are removed using appropriate solid-liquid separation techniques (such as mechanical vapor recompression or distillation, filtration, centrifugation or sedimentation, etc.). Solid-liquid separation techniques are well known among those skilled in the art. In one embodiment, the separation is performed using a hydrocyclone.

[0056] Next, in step (d1), the dissolved silicate is precipitated and then separated from the alkaline solution. The precipitation can be achieved by adding one or several compounds that convert the silicate into a form that is insoluble in water. In some embodiments, the precipitation is achieved by adding calcium hydroxide or calcium chloride according to the following formulas 3 and 4. Na2SiO3 + 2Ca(OH)2 → 2NaOH + Ca2SiO 4(s) + H2O Formula 3 Na2SiO3 + 2CaCl2 + H2O → 2NaCl + Ca2SiO4(s) + 2HCl Formula 4

[0057] Due to the insolubility in water, solid Ca2SiO4 that precipitates is formed by both reactions. The precipitate has low cost and energy consumption and contributes to the efficiency of the overall process.

[0058] Following any one or more of step (c), step (d) and step (e), at least a part of the alkaline solution may be reused in step (b). In another embodiment, following step (e), at least a part or all of the alkaline solution may be concentrated to provide water and a concentrated alkaline solution. Here, the concentrated alkaline solution is reused in step (b). When the alkaline solution is reused, water and hydroxide are conserved, so the process efficiency is improved and there is no need to discard it.

[0059] The combination of step (b) and step (d1) is possible as a one-pot reaction by introducing stoichiometric amounts of Si, aqueous NaOH solution and solid Ca(OH)2 into a hydrogen reactor based on Formulas 1 to 3. The rate and efficiency of H2 generation are slightly higher than in step (b) as a result of the higher hydroxide concentration provided by dissolved Ca(OH)2, but are limited by the dissolution rate of Ca(OH)2, so a longer incubation time after H2 generation is required to complete Formula 3. The resulting Ca2SiO4 precipitate can be removed by simple solid-liquid separation as described in step (c) or step (e). The advantage of this step is that the aqueous NaOH solution can be recovered at the original concentration or a concentration close thereto without re-concentration.

[0060] In an alternative embodiment, the alkaline solution may be neutralized as part of step (d1). This can be achieved by equally dividing the alkaline solution into a first solution and a second solution, adding Ca(OH)2 to the first solution, and adding CaCl2 to the second solution. The first solution and the second solution each contain equimolar amounts of NaOH (Equation 3) and HCl (Equation 4), which can be mixed to neutralize each other (NaOH + HCl → NaCl + H2O).

[0061] The process may further include collecting, compressing, and storing the hydrogen gas generated in step (b). In some embodiments, following step (b), water vapor and / or caustic vapor may be removed from the hydrogen.

[0062] Hydrogen gas is highly flammable and easily forms explosive mixtures with air or oxygen. Therefore, there are problems in transporting hydrogen gas. The process of the present disclosure enables the safe preparation of hydrogen on-site for a given application, thus avoiding the need for transportation. Also, this process is environmentally friendly in that no toxic by-products are generated. In fact, the main by-product (silicate) of this process is used in several industries, such as absorbents, food additives, refractory materials, and fertilizer additives. This improves the commercial value of this process.

[0063] In another aspect of the present disclosure, an apparatus for generating hydrogen is provided, the apparatus comprising: A caustic dissolution tank having one or more inlets suitable for introducing water and hydroxide, an inlet for an active substance such as a porous silicon material, and an outlet for discharging the alkaline solution; an inlet for an acidic solution for quenching the system in an emergency; One or more hydrogen reaction tanks having one or more inlets suitable for introducing silicon and the alkaline solution, an outlet for discharging the generated hydrogen, and an outlet for discharging the alkaline solution, the one or more hydrogen reaction tanks being in fluid communication with the caustic dissolution tank; A first solid-liquid separator that is in fluid communication with the one or more hydrogen reaction vessels and removes unreacted solids present in the alkaline solution received from the one or more hydrogen reaction vessels; A precipitation tank that is in fluid communication with the first solid-liquid separator and precipitates the silicate dissolved in the alkaline solution received from the first solid-liquid separator; and A second solid-liquid separator that is in fluid communication with the precipitation tank and separates the silicate precipitated from the alkaline solution received from the precipitation tank.

[0064] In some cases, the precipitation tank can be "combined" with the hydrogen reaction tank.

[0065] Referring to FIG. 3 here, this apparatus comprises a caustic dissolution tank (310) having an inlet (311) for introducing water from a water supply section (300) and an inlet (312) for introducing a hydroxide. The caustic dissolution tank (310) may be made of an alkali-resistant material such as stainless steel, for example, and may be attached to a cooling jacket (not shown). The caustic dissolution tank (310) further comprises an outlet (313) for discharging the alkaline solution and a mechanical stirrer (314). The caustic dissolution tank (310) is in fluid communication with a hydrogen reaction tank (320) via a conduit (314). The hydrogen reaction tank (320) may be made of an alkali-resistant material such as stainless steel, for example, and may be attached to a cooling jacket (not shown). The hydrogen reaction tank (320) may also comprise a condenser (not shown). The hydrogen reaction tank (320) comprises an inlet (321) for introducing the alkaline solution received from the caustic dissolution tank (310) and an inlet (322) for introducing a silicon material. The hydrogen reaction tank (320) further comprises an outlet (323) for discharging the hydrogen generated within the hydrogen reaction tank (320), an outlet (324) for discharging the alkaline solution, and a mechanical stirrer (325). The first solid-liquid separator (340) is in fluid communication with the hydrogen reaction tank (320) via a conduit (326). The sedimentation tank (350) is in fluid communication with the first solid-liquid separator (340) via a conduit (341) and further comprises a mechanical stirrer (351). The second solid-liquid separator (360) is in fluid communication with the sedimentation tank (350) via a conduit (352). The second solid-liquid separator (360) is also in fluid communication with the caustic dissolution tank (310) via a conduit (361). The first solid-liquid separator (340) and the second solid-liquid separator (360) may be a hydrocyclone, a filtration device, a centrifugal separation device, or a sedimentation tank. This apparatus further comprises a thermoelectric generator (330). This apparatus may further comprise a pump (not shown) disposed between one or more of the following: the caustic dissolution tank and the hydrogen reaction tank, the hydrogen reaction tank, the first solid-liquid separator, the sedimentation tank, and the second solid-liquid separator for moving the alkaline solution between these components of the apparatus.

[0066] In use, the medium, water and hydroxide are each introduced into the caustic dissolution tank (310) via the inlets (311) and (312). When the resulting mixture is stirred, the hydroxide dissolves to obtain the alkaline solution and heat. This heat typically maintains the alkaline solution in the caustic dissolution tank (310) at a temperature of about 50 °C (however, the temperature and thus the reaction rate can be adjusted accordingly). The surplus heat is transported to the thermoelectric generator (330). The alkaline solution exits through the outlet (313) and moves through the conduit (314) and through the inlet (321) to the hydrogen reaction tank (320). Silicon is introduced into the hydrogen reaction tank (320) via the inlet (322). Then, the reactions described by Equation 1 and Equation 2 occur, producing hydrogen gas, silicon dioxide and silicate. The hydrogen gas produced exits the hydrogen reaction tank (320) via the outlet (323) and may subsequently be compressed and stored. Following the reactions of Equation 1 and Equation 2, the resulting alkaline solution exits through the outlet (324) and moves through the conduit (326) to the first solid-liquid separator (340). This solid-liquid separator (340) separates unreacted silicon and / or undissolved silicon dioxide from the alkaline solution. The alkaline solution is then transported to the precipitation tank (350) via the conduit (341). The precipitation of the dissolved silicate is carried out in the precipitation tank (350), for example, by adding calcium hydroxide and / or calcium chloride to the alkaline solution. The alkaline solution containing the precipitated silicate is then transported to the second solid-liquid separator (360) by the conduit (352), where the precipitated silicate is separated from the alkaline solution. The resulting alkaline solution is then returned to the caustic dissolution tank via the conduit (261). In an alternative embodiment, the alkaline solution may be returned to the hydrogen reaction tank (320).

[0067] In some embodiments, the process may be carried out as a batch process, a semi-batch process, a continuous process, or a semi-continuous process.

Examples

[0068] The present disclosure will be further described below with reference to non-limiting examples.

[0069] In the following example, a process for producing 150 kg of hydrogen per day using silicon will be described.

[0070] A stainless steel tank with a capacity of 1.41 m equipped with a cooling jacket, mixes water and NaOH while vigorously stirring to make the concentration of the hydroxide 8.9 M. Maintain the production rate of the alkaline solution at 470 L / h, and thereby utilize the heat generation during dissolution (0.11 kWh / L solution) to maintain the temperature of the alkaline solution at about 50 °C. Excess heat of up to 51.7 kW is transferred to the thermoelectric generator. 3 Transfer the caustic solution to a pair of hydrogen reaction tanks with a total capacity of 941 liters. This process is carried out semi - continuously according to the schedule shown in FIG. 6.

[0071] By controlling the distribution of silicon (90 kg / batch), hydrogen is reliably generated over a reaction period of 1.5 hours. Due to the net heat generation of the reaction (23.8 kWh / kg H2), the reaction medium in the hydrogen reaction tank self - heats, which is maintained at an optimal operating condition of about 80 °C. The excess heat is transferred to the thermoelectric generator. The hydrogen reaction tank also includes an internal condenser in the headspace for condensing the saturated water vapor (up to 15 kg / batch) accompanying the hydrogen gas stream exiting the reactor. The operating temperature of this system will largely depend on the ambient temperature.

[0072]

[0073] ​Unreacted silicon and / or undissolved silicon dioxide are separated from the alkaline solution using a hydrocyclone. The recovered alkaline solution contains dissolved Na2SiO3 (up to a concentration of about 3.5 M). This Na2SiO3 is precipitated using calcium hydroxide, resulting in the formation of Ca2SiO4. To treat the alkaline solution, in order to completely precipitate Na2SiO3, it is necessary to set the volume ratio of the saturated calcium hydroxide solution to the clarified solution to 300:1. The stirring speed during the precipitation process is kept low to promote the formation of a large amount of Ca2SiO4 precipitate. The Ca2SiO4 precipitate is separated from the alkaline solution using a hydrocyclone. The resulting caustic solution (about 0.032 M) is further concentrated to about 8.9 M and then recycled to a stainless steel tank. Generation of Electricity from Hydrogen and Generation of Heat from the Corresponding Reaction

[0074] The hydrogen fuel produced from the above process can be conveniently delivered directly to a fuel cell (400) for on-site power generation. Considering the ultra-high purity grade of the hydrogen stream, i.e., the extremely small amount of carbon monoxide is negligible, the options for fuel cells combined with this process are abundant, such as polymer electrolyte fuel cells (PEMFCs), alkaline fuel cells, carbonate fuel cells, solid oxide fuel cells, etc. In any case, in order to achieve the highest conversion efficiency, it is advantageous to use a low-temperature fuel cell, i.e., a PEMFC.

[0075] Direct power production has the advantage of avoiding the need for costly and dangerous high-pressure hydrogen storage or cryogenic hydrogen storage. Instead, storing power in a battery, whether new or recycled, is an easier option. Furthermore, the use of recycled batteries from EVs and other sources can be very beneficial from the perspective of carbon credits.

[0076] The production of H2 in the hydrogen reactor (320) of FIG. 3 can be carried out on demand or in a quasi-steady state as described in the above exemplary process. Assuming that 75 kg of H2 per day is directly supplied from the hydrogen reactor (320) to the anode feed of the fuel cell stack and the efficiency of the PEMFC is a conservative 64%, a maximum of 1600 kWh is generated per day. Here, a 50% single-pass conversion is assumed. The mixture of water and unconverted H2 in the anode outlet stream of the PEMFC is condensed and dried using a condenser (410), and this H2 is recycled to the feed. Considering the internal power consumption of the entire process, including the operation of pumps, heat exchangers, units, and control systems, the net electrical output per day will exceed 1200 kWh.

[0077] The generated direct current (DC) electricity can be boosted using a DC boost module (420) and optionally further converted to 50 / 60 Hz alternating current (AC, two-phase or three-phase) via a DC / AC converter (430). The high voltage enables high-power and / or multiple charging applications such as grid charging, EV charging, and emergency regenerators.

[0078] An additional battery pack (450) may be arranged as an electrical buffer after the fuel cell stack (400). This stores surplus power (not used in the intended application) and supplements additional electricity (when higher power is required than that directly output from the fuel cell stack (400) to the power grid via the distribution module (460)). As described above, the use of recycled batteries can be beneficial in terms of obtaining carbon credits. When the amount of power generated exceeds the amount required for direct end - use, the surplus power is directed to charging the battery module (450). Further voltage boosting is provided by any DC boost module (440) depending on the voltage required for battery charging. During periods when the load on the power grid peaks and the power directly supplied from the fuel cell stack (400) to the power grid is insufficient to meet the peak - load requirements, additional power may be controllably supplied from the charged battery module (450) to the power grid to enable the power grid to meet the peak - load requirements and supplement the power supplied by the fuel cell stack (400).

[0079] In another exemplary embodiment, the present invention provides a method for converting electricity received from a power source (e.g., electricity that has been curtailed from or not fully utilized by the power grid) into an energy storage material. The method includes performing a carbothermal reduction of quartz using the received electricity to produce silicon. Such carbothermal reactions can consume, in some examples, approximately 10 - 12 MWh per ton of the produced metallurgical grade silicon. The carbon source used to perform the carbothermal reaction can include natural or synthetic carbon such as wood chips, coal, coke, or carbonized materials. The produced silicon may be further processed to form porous silicon. In some examples, it can consume approximately 6 - 9 MWh per ton of the produced porous silicon. Thus, in some examples, the production of porous silicon from quartz can typically require approximately 16 - 21 MWh per ton. Additionally, other products such as NaOH may be produced via a chlor-alkali process driven by the electricity received from the power grid. Other products of the chlor-alkali process include hydrogen and chlorine gas, which may be used in the production of hydrochloric acid. The porous silicon, NaOH, and other products produced using the electricity received from the power grid can be stored relatively safely and indefinitely in an inert / vacuum environment and later used on demand to produce hydrogen, which can then be used to generate electricity, thus functioning as a grid storage material. More preferably, the received electrical energy that can be converted into an energy storage material may preferably include electricity curtailed from and / or not fully utilized by the power grid. In a specific exemplary scenario, reacting 1 kg of porous silicon with an alkaline solution can produce approximately 142.28 grams of hydrogen. Also, assuming a fuel cell efficiency of 60%, using 1 kg of hydrogen can produce approximately 20 kWh of electricity.

[0080] Porous silicon is produced in locations where there is an excess of curtailed power, preferably renewable power. The energy stored within the porous silicon can be released on demand when it reacts with NaOH (aqueous solution) in the form of hydrogen.

[0081] Recycled silicon or scrap silicon from solar cell manufacturers, or waste silicon materials from the electronics industry, can be used as feedstock in the production of porous silicon. In this scenario, the energy required to produce porous silicon is reduced in the range of 60 - 75%, and as a result, porous silicon will release more energy than is required for its production, opening the way for it to become the world's first negative-carbon grid storage material.

[0082] When the porous structure of the silicon material is stored in a vacuum or an inert environment, its reactivity is maintained indefinitely, making porous silicon an ideal grid storage material equivalent to a barrel of oil.

[0083] In addition to reacting porous silicon with an alkaline solution to produce hydrogen, such a reaction can also generate heat on demand. Such heat is released by the dissolution of NaOH in water, generating heat in the range of 1.2 - 6.88 kWh per kg of the generated H2. Here, the molar concentration of NaOH affects the following: a. The composition of the by-products of the chemical reaction that produces hydrogen; b. The rate of hydrogen production.

[0084] Continuous oxidation of porous silicon in a basic solution will produce hydrogen in any form of chemical reactor, and heat in the amount of 24 kWh will be released per kg of the generated hydrogen. Therefore, the total amount of heat generated by producing 1 kg of hydrogen is as follows: - Lower limit = 24 + 1.2 = 25.2 kWh - Upper limit = 24 + 6.88 = 30.88 kWh

[0085] The round-trip energy efficiency of this system is in the range of 45 - 55% assuming that energy is used to produce porous silicon from quartz and electricity is drawn from the grid, i.e., without power reduction, H2 + the released thermal energy. This makes it the most efficient transportable and storable energy carrier.

[0086] The freezing point of NaOH (aqueous solution) depends on its molar concentration. Therefore, at sub-zero temperatures, the original solution is already basic to prevent freezing. For this reason, the heat generated by further dissolution of NaOH will decrease.

[0087] For context, in an electrolyzer with a polymer electrolyte membrane (PEM), 60 kWh is required to produce 1 kg of hydrogen (including the energy consumed to produce deionized water). Energy balance = 33.33 / 60 = 55%. For hydrogen storage, depending on the storage pressure or form (i.e., compressed hydrogen or liquefied hydrogen), approximately 4 - 12 kWh per kg of hydrogen will be required. Also, the amount of hydrogen stored will be limited by the number of hydrogen tanks on the site. Pumped-storage hydropower can usually maintain continuous discharge for 4 - 16 hours.

[0088] Using the on-demand heat generated from the hydrogen or power generation (electrochemically generating electricity by passing hydrogen through a fuel cell), for example, it is possible to heat a house, perform the same function as aquifer thermal energy storage (ATES) without a storage tank in the aquifer, or support a commercial dehumidification system. Definitions

[0089] The following are some definitions that may be helpful in understanding the description of the present disclosure. These are intended as general definitions and do not limit the scope of the present disclosure to those terms only, but are described to better understand the following description.

[0090] Throughout this specification, unless otherwise specifically stated in the context, variations such as the word "comprises" or "comprising" are understood to mean that the recited element, integer, or step, or group of elements, integers, or steps is included, but not that any other element, integer, or step, or group of elements, integers, or steps is excluded.

[0091] As used herein, the term "one" is used to refer to one or more (i.e., at least one) of the grammatical objects of the article. By way of example, "one element" means one element or a plurality of elements.

[0092] In the context of this specification, the term "about" is understood to refer to a range of numerical values that are considered by those skilled in the art to be equivalent in the context of achieving the same function or result. The term "about" is understood to refer to + / - 10% of the recited value.

[0093] Any numerical range recited herein is intended to include all sub-ranges of the same numerical precision that are included within the recited range. For example, the range of 1.0 to 5.0 is intended to include all sub-ranges between the recited minimum value of 1.0 and the recited maximum value of 5.0. That is, the minimum value is 1.0 or greater and the maximum value is 5.0 or less (such as 2.1 to 4.5, etc.). Any maximum numerical limit recited herein is intended to include all lower numerical limits included therein, and any minimum numerical limit recited herein is intended to include all higher numerical limits included therein.

[0094] When a part is described as being "fixed", "coupled", "attached", "engaged", or "connected" to another part, etc., that part may be directly fixed to the other part or there may be an intermediate part, unless the contrary is stated explicitly or implicitly. When a part is described as being "disposed on" or "in" another part, that part may be directly disposed on or in the other part or there may be an intermediate part, unless the contrary is stated explicitly or implicitly.

[0095] Unless otherwise specified, all technical and scientific terms have the ordinary meaning as commonly understood by those skilled in the art. The terms used in this disclosure are for illustrative purposes only and not for limitation. The term "and / or" as used in this disclosure means each and every combination of one or more of the recited related items.

[0096] For the purpose of description, all documents referred to in this specification are hereby incorporated by reference in their entirety herein, unless otherwise specified.

[0097] Those skilled in the art will understand that the invention described herein is susceptible to variations and modifications other than those specifically described, without departing from the scope of the invention. All such variations and modifications that are obvious to those skilled in the art should be considered to be included within the spirit and scope of the invention as broadly described herein. As is understood, the invention includes all such variations and modifications. The invention also includes all of the steps and features individually or collectively referred to or shown herein, and any combination of two or more of these steps or features.

[0098] Any reference in this specification to prior art is not an admission or suggestion that such prior art forms part of the common general knowledge or should be so construed.

Claims

1. A method for supplying electricity to an electrical load, comprising: (i) providing an alkaline solution; (ii) reacting the alkaline solution with silicon to generate hydrogen; (iii) processing the hydrogen in a fuel cell to produce electricity; and (iv) supplying the electricity from the output of the fuel cell to the electrical load via a suitable electrical interface module A method comprising the steps of:

2. The method according to claim 1, wherein the silicon comprises one or more portable units of silicon.

3. The method according to any one of the preceding claims, wherein the silicon comprises porous silicon.

4. The porous silicon is (i) alloying silicon with at least one distillable alloying metal selected from at least one of zinc, magnesium, calcium, and antimony to form an alloy; (ii) forming pellets or particles of the alloy in an inert environment to reduce or minimize oxidation of the alloy; and (iii) distilling the alloying metal from the particles of the alloy to produce a porous silicon structure contained therein The method according to claim 3, which is produced according to the steps of:

5. The method according to any one of the preceding claims, further comprising controllably supplying electricity from the output of the fuel cell to the electrical load in response to variable load requirements necessary to supply power to the load.

6. The method according to any one of the preceding claims, further comprising controllably supplying hydrogen to a compression system to provide a hydrogen refueling station.

7. The step of supplying the electricity includes charging a battery module using at least a portion of the electricity from the output of the fuel cell, the charged battery module being configured to function as a buffer between the fuel cell and the load, or supplying an appropriate amount of electricity to the electrical load to supplement the electricity directly supplied from the output of the fuel cell to the electrical load, or being configured to apply the electrical interface module. The method according to any one of the preceding claims.

8. The method according to any one of the preceding claims, wherein the battery module includes a new battery module or a used EV battery.

9. The method according to any one of the preceding claims, wherein the electrical load includes a power grid.

10. A method for converting electricity received from a power source into an energy storage material, comprising: (i) receiving electricity from the power source; and (ii) performing carbon thermal reduction of quartz using the received electricity to generate silicon. The method further includes: storing the silicon for later on-demand use to release energy by reacting the silicon with an alkaline solution to generate hydrogen and heat. **Claim 11** The method according to claim 10, wherein the silicon includes porous silicon. **Claim 12** The method according to any one of claims 10 or 11, wherein the silicon is stored in a state suitable for transportation. **Claim 13** The method further includes generating NaOH via a chlor-alkali process using the received electricity, and storing the NaOH for later use as an alkaline solution that can react with the silicon to generate hydrogen and heat. The method according to any one of claims 11 to 13. **Claim 14** The method according to any one of claims 10 to 13, wherein the power source includes a power grid. **Claim 16** The method according to claim 15, wherein the electricity received from the power grid includes electricity that has been reduced or not fully utilized from the power grid. **Claim 17** The method according to any one of the preceding claims, wherein heat is generated on-demand from the hydrogen and / or electricity generation process. **Claim 18** A system for supplying electricity to an electrical load, wherein the system is operable to perform any one of the steps described in claims 1 to 9. **Claim 19** A system for converting electricity received from a power source into an energy storage material, wherein the system is operable to perform any one of the steps described in claims 10 to 17. **Claim 20** A portable unit of stored silicon or NaOH according to any one of the preceding claims, configured for use by any one of the steps described in claims 1 to 16.

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