초록 ▼

Storage systems based on latent heat storage have high-energy storage density, which reduces the footprint of the system and the cost. However, phase change materials (PCMs), such as NaNO3, NaCl, KNO3, have very low thermal conductivities. To enhave the storage of PCMs, macroencapsulation of PCMs wa

Storage systems based on latent heat storage have high-energy storage density, which reduces the footprint of the system and the cost. However, phase change materials (PCMs), such as NaNO3, NaCl, KNO3, have very low thermal conductivities. To enhave the storage of PCMs, macroencapsulation of PCMs was performed using a metal oxide, such as SiO2 or a graphene-SiO2, over polyimide-coated or nickel-embedded, polyimide-coated pellets The macro encapsulation provides a self-supporting structure, enhances the heat transfer rate, and provides a cost effective and reliable solution for thermal energy storage for use in solar thermal power plants. NaNO3 was selected for thermal storage in a temperature range of 300° C. to 500° C. The PCM was encapsulated in a metal oxide cell using self-assembly reactions, hydrolysis, and simultaneous chemical oxidation at various temperatures.

대표청구항 ▼

1. A method of manufacturing a thermal energy storage material, comprising the steps: providing a phase changing salt pellet, wherein the phase changing salt pellet is inorganic;coating the exterior surface of the phase changing salt pellet in a polyimide coating;wherein the polyimide coating compri

1. A method of manufacturing a thermal energy storage material, comprising the steps: providing a phase changing salt pellet, wherein the phase changing salt pellet is inorganic;coating the exterior surface of the phase changing salt pellet in a polyimide coating;wherein the polyimide coating comprises polyimide and a surface roughener disposed in the polyimide coating, where the surface roughener is nickel, silicon carbide, or carbon;curing the polyimide coating; andencapsulating the exterior of the polyimide coating with a metal oxide or a graphene-metal oxide composite. 2. The method of claim 1, wherein the phase changing salt pellet is aluminum phosphate, ammonium carbonate, ammonium chloride, caesium carbonate, caesium sulfate, calcium citrate, calcium carbonate, calcium chloride, calcium hydroxide, calcium oxide, calcium phosphate, calcium saccharate, calcium sulfate, cerium phosphate, chromic chloride, iron phosphate, lithium carbonate, lithium sulfate, magnesium chloride, magnesium sulfate, manganese chloride, manganese nitrate, manganese sulfate, potassium acetate, potassium carbonate, potassium chloride, potassium hydroxide, potassium phosphate, rubidium carbonate, rubidium sulfate, disodium tetraborate, sodium acetate, sodium bicarbonate, sodium bisulfate, sodium borate, sodium carbonate, sodium citrate, sodium chloride, sodium hydroxide, sodium nitrate, sodium percarbonate, sodium persulfate, sodium phosphate, sodium propionate, sodium selenite, sodium silicate, sodium sulfate, sodium tellurate, sodium tetraborate, sodium thiosulfate, strontium hydrophosphate, zinc acetate, zinc chloride, eutectic of Li2CO3 and Na2CO3, or a combination thereof. 3. The method of claim 1, wherein phase changing salt pellet is made either by using power press or a pelletizer. 4. The method of claim 1, wherein the polyimide coating is cured at up to 250° C. for 2 hours. 5. The method of claim 4, wherein the polyimide coating is cured at a temperature of between about 220° C. and about 250° C. for 2 hours. 6. The method of claim 1, wherein the polyimide coating is coated further comprising the steps: mixing the polyimide with N-methyl 2-pyrrolidinone and a plasticizer organic solvent;applying a thin layer of the NMP+polyimide mixture onto the phase changing salt pellet by dip coating, spray coating, or brushing; andcuring the polyimide layer. 7. The method of claim 4, further comprising heating the phase changing salt pellet up to 250° C. for 2 hours at 4° C./min. 8. The method of claim 1, further comprising: adding an additive to the polyimide prior to coating the exterior surface of the phase changing salt pellet in a polyimide,wherein the additive is nickel powder, silicon carbide, or carbon. 9. The method of claim 1, wherein the metal oxide encapsulant is silicon dioxide, titanium dioxide, zinc oxide, calcium oxide, barium oxide, titanium dioxide-silicon dioxide composite, cerium dioxide, iron (III) oxide, aluminum (III) oxide, magnesium oxide, lithium cobalt dioxide, lithium nickel dioxide, zinc oxide, zirconium dioxide, lithium, titanium oxide, lithium aluminum manganese oxide, lithium nickel manganese oxide, lithium dimanganese tetraoxide, indium tin oxide, or combinations thereof. 10. The method of claim 9, wherein the exterior of the polyimide coating is encapsulated in silicon dioxide or a graphene-silicon dioxide composite, further comprising the steps: obtaining a sol-gel silicon dioxide precursor, wherein the sol-gel silicon dioxide precursor is tetraethyl orthosilicate or tetraethyl orthosilicate containing graphene;mixing the sol-gel silicon dioxide precursor with 3-aminopropyltriethoxy silane to form a silicate precursor;placing the polyimide-coated phase changing salt pellets into the silicate precursor;heating the silicate precursor;adding ethanol and hydrochloric acid to the silicate precursor;permitting the silicate precursor to hydrolyze for about 5 to about 10 minutes;neutralizing the silicate precursor with sodium hydroxide; andpermitting the sol-gel silicon dioxide precursor to encapsulate the polyimide coated phase changing salt pellet. 11. The method of claim 10, wherein the sol-gel graphene-silicon dioxide precursor is cured at 250° C. at a rate of 4° C./minute for two hours. 12. The method of claim 1, further comprising: forming a void space in the phase changing salt pellet prior to polyimide coating, wherein the void space is formed by drilling, briquetting, or die casting the pellet with a void space. 13. The method of claim 12, further comprising: reducing the pressure in the void space, comprising:inserting a metal wire into the phase changing salt pellet during fabrication of the pellet;heating the phase changing salt pellet;removing the metal wire from the phase changing salt pellet;permitting heated gases to escape from the void space; andapplying the polyimide coating to the phase changing salt pellet to seal the void space. 14. The method of claim 1, further comprising functionalizing the surface of the phase changing salt pellet, comprising: soaking the phase changing salt pellet in a solution of hexane and silane for 24 hours prior to applying the polyimide coating to the phase changing salt pellet.