NOVEL MATERIAL AND PRODUCTION THEREOF FOR USE AS A STORAGE MEDIUM IN A SENSITIVE ENERGY STORAGE SYSTEM IN THE LOW-, MEDIUM- OR HIGH-TEMPERATURE RANGE

Abstract

The present invention relates to a modified red mud/a modified bauxite residue and also to processes for the production thereof and to a storage medium comprising a modified red mud, to a heat storage means comprising a storage medium and to numerous uses of a modified red mud as storage medium, in particular in a heat storage means. The modified red mud contains the following components: haematite (Fe.sub.2O.sub.3), corundum (Al.sub.2O.sub.3), rutile (TiO.sub.2) and/or anatase (TiO.sub.2), quartz (SiO.sub.2), optionally perowskite (CaTiO.sub.3) and optionally pseudobrookite ((Fe.sup.3+,Fe.sup.2+).sub.2(Ti,Fe.sup.3+)O.sub.5), nepheline ((Na,K)[AlSiO.sub.4]) and/or hauynite ((Na,Ca).sub.4-8[Al.sub.6Si.sub.6O.sub.24(SO.sub.4)]), wherein the modified red mud is substantially free from Na.sub.2O and/or glass. A novel material is thus provided, and the production thereof for use as a storage medium in a sensitive energy storage system in the low-, medium- or high-temperature range is described.

Claims

1-38. (canceled)

39. A modified red mud comprising: haematite (Fe.sub.2O.sub.3); corundum (Al.sub.2O.sub.3); rutile (TiO.sub.2) and/or anatase (TiO.sub.2); quartz (SiO.sub.2); and less than 0.5% by weight of Na.sub.2O and/or glass.

40. The modified red mud of claim 39 further comprising at least one of: perovskite (CaTiO.sub.3); pseudobrookite ((Fe.sup.3+,Fe.sup.2+).sub.2(Ti,Fe.sup.3+)O.sub.5); nepheline ((Na,K)[AlSiO.sub.4]); and hauynite ((Na,Ca).sub.4-8[Al.sub.6Si.sub.6O.sub.24(SO.sub.4)]).

41. The modified red mud of claim 39 further comprising: 48 to 55% by weight of haematite (Fe.sub.2O.sub.3); 13 to 18% by weight of corundum (Al.sub.2O.sub.3); 8 to 12% by weight of rutile (TiO.sub.2) and/or anatase (TiO.sub.2); 2 to 5% by weight of quartz (SiO.sub.2); and less than 0.03% by weight of Na.sub.2O and/or less than 0.1% by weight of glass.

42. The modified red mud of claim 39, wherein the modified red mud contains less than 0.5% by weight of aluminium titanate (Al.sub.2TiO.sub.5), iron (Fe), mayenite (Ca.sub.12Al.sub.14O.sub.33), ulvospinell (Fe.sub.2TiO.sub.4), and/or andradite (Ca.sub.3Fe.sub.2(SO.sub.4).sub.3).

43. The modified red mud of claim 39, wherein the modified red mud has a porosity of less than 15%, in particular in the range from 5 to 12%.

44. The modified red mud of claim 39, wherein the modified red mud has a density in the range from 3.90 to 4.0 g/cm.sup.3, in particular approximately 3.93 g/cm.sup.3.

45. The modified red mud of claim 39, wherein the modified red mud has a mean particle size d50 in the range from 3 to 10 m.

46. The modified red mud of claim 39, wherein the modified red mud has a specific thermal capacity at 20 C. in the range from 0.6 to 0.8 kJ/(kg*K) and/or a specific thermal capacity at 726.8 C. in the range from 0.9 to 1.3 kJ/(kg*K).

47. The modified red mud of claim 39, wherein the modified red mud has a specific thermal conductivity in the range from 3 to 35 W/(m*K).

48. The modified red mud of claim 39 further comprising one or more of the following components: an agent for preventing inclusion of air and air adsorption; an agent for improvement of the thermal conductivity, in particular selected from the group consisting of metal colloids, metal powder, graphite and substances containing silicon; and an agent for formation of a thixotropic composition.

49. The modified red mud of claim 39, wherein the modified red mud comprises an energy storage medium that can be repeatedly heated and cooled.

50. The modified red mud of claim 49 further comprising at least one device for charging and discharging heat to and from the modified red mud.

51. The modified red mud of claim 50, wherein the at least one device comprises resistance wires.

52. A method of producing a modified red mud comprising: heating a red mud to a temperature of at least 800 C., wherein the red mud has a mineral composition comprising: 10 to 55% by weight of iron compounds; 12 to 35% by weight of aluminium compounds 3 to 17% by weight of silicon compounds 2 to 12% by weight of titanium dioxide; 0.5 to 6% by weight of calcium compounds; and less than 0.5% by weight of Na.sub.2O.

53. The method of claim 52 further comprising washing and drying the red mud using iron(II)chloride prior to heating the red mud.

54. The method of claim 52 further comprising: granulating the red mud after the heating; and subsequently compressing the granulate.

55. The method of claim 52, wherein heating the red mud comprises heating the red mud in a non-reducing atmosphere.

56. A method of storing energy comprising: repeatedly heating and cooling a modified red mud that comprises the following components: haematite (Fe.sub.2O.sub.3); corundum (Al.sub.2O.sub.3); rutile (TiO.sub.2) and/or anatase (TiO.sub.2); quartz (SiO.sub.2); and less than 0.5% by weight of Na.sub.2O and/or glass.

57. The method of claim 56 further comprising storing heat energy within the modified red mud at a temperature of more than 100 C. and up to 1000 C.

58. The method of claim 56 further comprising simultaneously heating and cooling the modified red mud.

59. The method of claim 56 further comprising heating the modified red mud by means of electrical current and/or cooling the modified red mud while electrical current is generated.

60. The method of claim 59 further comprising heating the modified red mud by means of electrical power obtained from at least one renewable energy source.

61. The method of claim 59 further comprising heating the modified red mud by applying electrical current to resistance wires located within the modified red mud.

62. The method of claim 59 further comprising cooling the modified red mud by transferring thermal power stored in the modified red mud to another medium, wherein the another medium comprises one of water, steam, molten salt, thermal oil, and gas.

Description

[0126] Further objects and advantages of embodiments of the present invention are disclosed with reference to the following detailed description and the attached drawings.

[0127] FIG. 1 shows a particle size distribution of a dry conventional bauxite residue.

[0128] FIG. 2 shows the density characteristics of a test sample during the heating of red mud from 100 C. up to 1000 C. in an oxygen (O.sub.2) or a nitrogen (N.sub.2) atmosphere.

[0129] FIG. 3 shows a particle size distribution of a red mud tempered at 1000 C. according to an exemplary embodiment of the invention.

[0130] FIG. 4 is a graphical representation of the series of measurements shown in Table 3 for the specific thermal capacity of ALFERROCK according to an exemplary embodiment of the invention.

[0131] Further details of the present invention and further embodiments thereof are described below. However, the present invention is not limited to the following detailed description, but it serves merely for illustration of the teaching according to the invention.

[0132] It may be pointed out that features which are described in connection with an exemplary embodiment or an exemplary subject can be combined with any other exemplary embodiment or with any other exemplary subject. In particular, features which are described in connection with an exemplary embodiment of a modified red mud according to the invention can be combined with any other exemplary embodiment of a modified red mud according to the invention as well as with any exemplary embodiment of a method for production of a modified red mud, of a storage medium, of a heat storage means and of uses of a modified red mud, and vice versa, unless explicitly stated otherwise.

[0133] If a term is designated with an indefinite or definite article, such as for example a, an and the, in the singular, this also includes the term in the plural, and vice versa, so long as the context does not specify otherwise unambiguously. The expression comprise or have, such as is used here, includes not only the meaning of contain or include, but can also mean consist of and substantially consist of.

[0134] For the studies conducted within the context of the present invention, first of all the material to be studied was characterised at room temperature, and in particular the chemical as well as the mineralogical composition were determined. Furthermore, this material was heated slowly to 1000 C. heated, and in this case every 100 C. the mineralogical phases as well as the density and the specific thermal capacity were determined.

[0135] The characterisation of the material to be studied:

1. CHEMICAL COMPOSITION (TYPICAL FOR BAUXITE RESIDUE)

[0136] 10 to 50% by weight of iron compounds [0137] 12 to 35% by weight of aluminium compounds [0138] 5 to 17% by weight of silicon compounds [0139] 2 to 10% by weight of titanium dioxide [0140] 0.5 to 6% by weight of calcium compounds

2. MINERALOGICAL COMPOSITION

[0141] In the initial state of the study the following mineral phases were determined radiographically: [0142] haematite [0143] goethite [0144] anatase [0145] rutile [0146] perovskite [0147] boehmite [0148] gibbsite [0149] cancrinite [0150] quartz

3. PARTICLE SIZES

[0151] The particle diameters (m) are shown in FIG. 1. According to this the substance is very fine and has 3 maxima. With a good distribution it was to be expected that the substance has a high density, since the very fine crystals can be inserted into cavities in the medium-fine crystals and these latter can be inserted into cavities in the coarser crystals. The measured density of 3.63 (g/cm.sup.3) confirms this assessment.

[0152] By addition of thermally stable and chemically inert substances with arbitrary particle size distribution, any cavities still present can be reduced with an effect on mechanical, electrical and thermal characteristics. This constitutes a further optimisation of the storage mechanism in the context of the invention.

4. CONDUCT OF THE TEST

[0153] Samples of the test substance were heated in stages under oxygen and under nitrogen up to 1,000 C. Samples were taken in each case at 100 C., 200 C., 300 C., 400 C., 500 C., 600 C., 700 C., 800 C., 900 C. and 1000 C. and the changes to the mineralogical composition as well as the density were determined.

[0154] The specific thermal capacity was measured in the temperature range from room temperature (30.26 C.) to 584.20 C.

5. INTERPRETATION OF THE RESULTS

[0155] 5.1 Mineral Phases

[0156] The mineralogical composition of the substance changes in accordance with the temperature (see following Table 1).

[0157] At approximately 300 C. gibbsite decomposes, at approximately 400 C. goethite decomposes and at approximately 500 C. boehmite breaks down. At 573 C. alpha-quartz is transformed into beta-quartz.

[0158] Above 600 C. the CO.sub.2 emission of cancrinite Na.sub.6Ca.sub.2 [(AlSiO.sub.4).sub.6 takes place substantially from haematite (Fe.sub.2O.sub.3) and corundum (Al.sub.2O.sub.3) and, in smaller proportions, of TiO.sub.2, cancrinite and perovskite.

[0159] At 1000 C. cancrinite and the two TiO.sub.2 phases anatase and rutile are converted into the minerals pseudobrookite [(Fe.sup.3+).sub.2Ti]O.sub.5 and nepheline [(Na,K)[AlSiO.sub.4].

TABLE-US-00001 TABLE 1 Mineral phases bauxite residue (bulk density 0.944 g/cm.sup.3) T [ C.] Mineral phases Bauxite residue GEA [00001]$\mathrm{Density}.Math..Math.\frac{g}{\mathrm{cm}.Math..Math.3}$ 100 Haematite, goethite, anatase, rutile, perovskite, 3.63 boehmite, gibbsite, cancrinite, quartz 200 Haematite, goethite, anatase, rutile, perovskite, 3.64 boehmite, gibbsite, cancrinite, quartz 300 Haematite, goethite, anatase, rutile, perovskite, 3.74 boehmite, cancrinite, quartz, -Al.sub.2O.sub.3 400 Haematite, goethite, anatase, rutile, perovskite, 3.81 boehmite, cancrinite, quartz, -Al.sub.2O.sub.3 500 Haematite, anatase, rutile, perovskite, boehmite, 3.81 cancrinite, quartz, -Al.sub.2O.sub.3 600 haematite, anatase, rutile, perovskite, cancrinite, 3.89 quartz, -Al.sub.2O.sub.3 700 haematite, anatase, rutile, perovskite, cancrinite, 3.60 quartz, -Al.sub.2O.sub.3 800 haematite, anatase, rutile, perovskite, cancrinite, 3.71 quartz, -Al.sub.2O.sub.3 900 haematite, anatase, rutile, perovskite, cancrinite, 3.73 quartz, -Al.sub.2O.sub.3 1000 haematite, anatase, rutile, perovskite, quartz, 3.93 -Al.sub.2O.sub.3, nepheline, pseudobrookite

[0160] 5.2 Density

[0161] As can be seen from FIG. 2, the density develops as a function of the temperature from 3.63 (g/cm.sup.3) at 100 C. to 3.93 (g/m.sup.3) at 1000 C. The decomposition of mineral phases with elimination of water and CO.sub.2 as well as sintering processes reduce the density between 600 C. and 700 C., in order then up to 1,000 C. to rise again to a value of 3.93 (g/cm.sup.3).

[0162] For applications in the thermal range it is only possible to use substances which are stable as bodies and which in the respective arbitrary temperature ranges do not eliminate any further gases such as H.sub.2O or CO.sub.2 and also do not undergo any further sintering processes. Oxides such as Fe.sub.2O.sub.3, Al.sub.2O.sub.3, TiO.sub.2 or SiO.sub.2 hardly change significantly in the event of temperature increases. A significant characteristic is revealed by the fact that the density of the substance heated to 1,000 C. remained constant during cooling constant remained, for example no rehydrations occurred.

[0163] 5.3 Particle Size

[0164] The tempering of the substance according to the invention up to temperatures of 1,000 C. shifts the particle diameters to significantly higher values for example by decomposition of hydroxides, oxide hydrates or carbonates and by sintering processes (cf. FIG. 3). Thus for example [0165] the d.sub.10 values grow from 0.074 m to 1.341 m [0166] the d.sub.30 values grow from 0.261 m to 6.743 m [0167] the d.sub.90 values grow from 1.692 m to 28.17 m

[0168] 5.4 Specific Thermal Capacity

[0169] The specific thermal capacity of substances is a function of the temperature. As the temperature increases, the specific thermal capacity also increases. The following Table 2 shows corresponding examples.

TABLE-US-00002 TABLE 2 Specific thermal capacity at different temperatures: 20 C. 726.8 C. Fe.sub.2O.sub.3 (kJ/(kg * K)) 0.650 0.944 Al.sub.2O.sub.3 (kJ/(kg * K)) 0.775 1.223 SiO.sub.2 (kJ/(kg * K)) 0.732 1.148 TiO.sub.2 rutile (kJ/(kg * K)) 0.689 0.937 TiO.sub.2 anatase (kJ/(kg * K)) 0.691 0.943

[0170] In mixtures the specific thermal capacity is the sum of the specific thermal capacities of the respective components of the mixtures.

[0171] The characterisation of the substance provided shows a mixture of different mineral substances. During tempering, parts of the substances decompose, and for example eliminate water or CO.sub.2 with formation of oxides or other chemically stable mineral phases. Furthermore, sintering processes take place.

[0172] The measurement results of these substances show a value of 0.791 (kJ/(kg*K)) at 30 C. and a value of

[00002]$1.037.Math.\left(\frac{\mathrm{kJ}}{\mathrm{kg}*K}\right)$

at 584 C. At 1,000 C. a value of

[00003]$1.14-1.18.Math.\left(\frac{\mathrm{kJ}}{\mathrm{kg}*K}\right)$

can be assumed by extrapolation (cf. FIG. 4).

TABLE-US-00003 TABLE 3 Series of measurements of specific thermal capacity ALFERROCK Temperature of thermal capacity c.sub.p ALFERROCK the sample [ C.] [(kJ)/(kg * K)] 30.3 C. 0.791 50.1 C. 0.832 69.8 C. 0.858 89.6 C. 0.877 109.4 C. 0.89 129.2 C. 0.898 149.0 C. 0.907 168.8 C. 0.915 188.5 C. 0.922 208.3 C. 0.928 228.1 C. 0.935 247.9 C. 0.94 267.7 C. 0.948 287.5 C. 0.95 307.3 C. 0.96 327.0 C. 0.963 346.8 C. 0.969 366.6 C. 0.977 386.4 C. 0.985 406.2 C. 0.989 426.0 C. 0.999 445.7 C. 1.002 465.5 C. 1.01 485.3 C. 1.017 505.1 C. 1.02 524.9 C. 1.026 544.6 C. 1.031 564.2 C. 1.035 584.2 C. 1.037

[0173] During cooling of the substance heated to 1,000 C. the c.sub.p values revert to values which correspond to the respective temperatures. However, since the starting substance has changed due to decompositions of mineral phases and the formation of other substances and also sintering processes have taken place, after the cooling the substance will have different values of the specific thermal capacity from the starting substance. It is important to establish that after the tempering a stable substance is available, which can be heated and cooled with any frequency and which in this case does not undergo any further change to the individual substances in the mixture. As already mentioned, this also applies for the density.

[0174] 5.5 Specific Thermal Conductivity

[0175] The thermal conductivity of a system is inter alia a function of parameters such as pressure, temperature, mineralogical composition, porosity, density, etc.

[0176] As described, all thermally unstable components have been decomposed by heating of the substance provided. After the tempering a substance occurs which consists of corundum (Al.sub.2O.sub.3), haematite (Fe.sub.2O.sub.3), rutile and anatase (TiO.sub.2) as well as fireproof substances such as pseudobrookite [(Fe.sup.3+).sub.2Ti]O.sub.5 or nepheline [(Na,K)[AlSiO.sub.4].

[0177] The following Table 4 shows the values of the thermal conductivity and density of those substances which constitute the most important components of the tempered substance.

TABLE-US-00004 TABLE 4 Thermal conductivity and density of the individual components Thermal conductivity: Density Anatase TiO.sub.2 4.8-11.8 3.89 (g/cm3) (W/(m * k)) Rutile TiO.sub.2 4.8-11.8 4.25 (g/cm3) (W/(m * k)) Haematite Fe.sub.2O.sub.3 6 (W/(m * k)) 5.26 (g/cm3) Corundum Al.sub.2O.sub.3 3.0-35 3.99 (g/cm3) (W/(m * k)) Quartz SiO.sub.2 18.37 (W/(m * k)) 2.65 (g/cm3)

[0178] During the tempering process the particle diameter of the substances produced has increased significantly and in this case the surface area is decreased. Thus within the primary crystals the conductivity also increased to values which are set out in Table 4. In principle, in crystal mixtures the phonons are reflected on the crystal boundaries with simultaneous reduction of the thermal conductivity, i.e. there is a causal relationship between crystal structures and thermal conductivity of a substance.

[0179] Air is still contained in the substance mixture and as a poor conductor of heat it lowers the measured thermal conductivity. In order to avoid this effect, different methods are possible, including for example application of pressure, i.e. pressing the substance to form solid bodies.

[0180] Furthermore, substances can be added, which prevent air inclusions between the crystallites or on the surface of the crystallites and thus enable the production of solid substance blocks.

[0181] These include for example: [0182] metal colloids [0183] metal powder [0184] graphite [0185] sinterable pyrolysing substances based on Si

[0186] As well as the addition of the said substances, pressure and thermal energy can additionally be used.

[0187] It is crucial to be able to produce good heat conducting substance blocks. For the use of the substance obtained after the tempering as a heat storage means, a good thermal conductivity, in particular the prevention of air inclusions, is significant for the charging operation (heating of the substance) and for the discharging operation (transfer of the stored heat to systems which for example generate steam).

EXAMPLE

[0188] A mixture of the provided substance consisting of untempered substance and substance tempered up to 1,000 C. in the ratio of 1:1 is surface-modified with 5% PDMS (polydimethylsiloxane prepolymer) and is introduced into a BUSS kneader or a co-rotating double screw extruder. The compounding machine has a housing temperature of 135 C. and maximum vacuum degassing. The torque is set to 65-85% of the maximum. The material is removed by means of a cooling conveyor.

[0189] The resulting water-free and air-free product is introduced into the insulated container and is mechanically compressed. Then the temperature is slowly increased to 1,000 C. and thus the heat storage means is made ready for operation. Instead of PDMS, other substances can be used, such as metal dusts, graphite or salt solutions.

6. SUMMARY

[0190] After washing or neutralisation, bauxite residue/red mud which is largely free of alkali and alkaline earth is used as starting material. The objective is to obtain simple and clearly defined substance structures with clear parameters even after tempering to for example 1000 C. or higher temperatures.

[0191] During tempering up to temperatures of 1,000 C. all components within the substance mixture which are unstable in this temperature range decomposed. These include gibbsite, goethite, boehmite as well as cancrinite and the TiO.sub.2 phases which, where applicable, form pseudobrookite [(Fe.sup.3+).sub.2Ti]O.sub.5 and nepheline [(Na,K) (AlSiO.sub.4)] at 1,000 C.

[0192] After the cooling, a substance mixture was formed, consisting of oxides such as Al.sub.2O.sub.3, Fe.sub.2O.sub.3, TiO.sub.2, SiO.sub.2 and optionally substances which are resistant to high temperatures, such as pseudobrookite and nepheline, which did not show any further change after renewed tempering to 1,000 C.

[0193] With the aforementioned change to the material composition the density also changed from 3.63 (g/cm.sup.3) at room temperature to 3.93 (g/cm.sup.3) at 1,000 C. This expected operation was additionally accompanied by sintering effects. During cooling of the substance mixture tempered to 1,000 C., the density reached at 1,000 C. remains unchanged, since the density of oxides such as Al.sub.2O.sub.3, Fe.sub.2O.sub.3 as well as TiO.sub.2 and SiO.sub.2 does not change in the temperature ranges between 25 C. and 1,000 C.

[0194] These sintering effects and the decomposition of mineral phases have led to an increase in the particle diameter in the substance mixture. Whereas before the tempering for example d.sub.50=0.261 m and d.sub.90=1.692 m applied, after the tempering the following values could be measured: d.sub.50=6.743 m and d.sub.90=28.17 m. The enlargement of the particles means a reduction of the surface and a better thermal conductivity. The air content (poor conductor of heat) between the very small crystallites was reduced.

[0195] The study of the specific thermal capacity of the characterised substance showed an increase in the specific thermal capacity of 0.79 (kJ/(kg K)) at 25 C. to 1.037 (kJ/(kg K)) at 600 C. At 1,000 C. a value of 1.14-1.18 (kJ/(kg K)) is to be expected by extrapolation.

[0196] Since, as already stated, the density has also increased, the product of the density and the specific thermal capacity as a crucial criterion for applications as heat storage means reaches values higher than that of water. Water has a density at 20 C. of 998.2 (kg/m.sup.3) and an outstanding specific thermal capacity of 4.182 (kJ/(kg K)). This results in a volumetric thermal capacity of 4175 (kJ/(m.sup.3 K)). On the other hand, the provided substance has a density of 3890 (kg/m.sup.3) and a specific thermal capacity of 1.037 (kJ/(kg K)) and thus a volumetric thermal capacity of 4.034 (kJ/(m.sup.3 K)) at approximately 600 C. At 1000 C. values for the density of 3,930 (kg/m.sup.3) and a c.sub.p von 1.16 (kJ/(kg K)) are produced. Thus the volumetric thermal capacity reaches a value of 4.559 (kJ/(m.sup.3 K)). This value significantly exceeds the value of water.

[0197] A substantial difference between water and the specified substance is the temperature at which the storage media can operate. Whilst water ideally operates in temperature ranges between 40 C. and 90 C., that is to say it has a T of 50 C., the provided substance can operate in the temperature range up to 1,000 C., i.e. the substance can evaporate water above a temperature of 100 C. and thus can operate with a T of 900 C. For this reason the provided substance can store 15-20 times as much heat by comparison with water (based on volume).

[0198] In storage media the coefficient of thermal conductivity is more important for the charging operation (heating up of the storage device) than for the discharging operation. The thermal conductivity of the oxides substantially contained in the substance is between 3 and 35 (W/(m K). What is crucial for heat storage means is the necessity of being able to compact the substance used as storage medium to form solid blocks in which the thermal power can flow optimally, i.e. from the heating element into the storage substance, within the storage substance and from the storage substance into the systems consuming thermal energy. In this respect it is advantageous if poorly heat-conducting gases within the substance or on the surface of the substance are eliminated. in addition to applications of pressure substances can be added by which the primary crystals are stuck together. These include, for example, metal colloids, metal powder, graphite, sinterable pyrolysing substances containing Si. Above all, it is also crucial that in the tempering process of the provided substance up to 1,000 C. all unstable substances are decomposed and so a predominantly oxidic, thermally stable storage substance is made available which can be heated and cooled with any frequency without generating gases such as H.sub.2O or CO.sub.2 which can destroy the storage block.

[0199] Charging and discharging of the heat storage means take place simultaneously at an arbitrary temperature or in a narrow temperature range. As a result a permanent change to the coefficients of thermal expansion is prevented and the thermal shock behaviour and the thermal cycling behaviour is stabilised in the sense of a long service life expectation of the energy storage device.

[0200] Use of the Provided Substance as Storage Material for High-Temperature-Heat Storage Means

[0201] The Storage System

[0202] Both water and also solid substancesfor example the previously described substancebelong to the sensitive heat storage systems (sensitive, because the heat of the storage device is perceptible).

[0203] The heat storage means can be heated by means of force/heat coupling by electrical power from wind farms or solar installations. In still air or in darkness these heat storage means can for example generate steam which drives turbines which in turn generate electrical power (cogeneration by heat/force coupling) by means of generators connected downstream. Thus the heat storage means takes on the role of emergency generator or, on a large scale, of replacement power plants. If this process is successful, the power line systems can also be simply and effectively designed.

[0204] The requirements for energy accumulators are set out below: [0205] High energy density [0206] High power density [0207] Low cumulative energy consumption [0208] Low losses [0209] Low self-discharge [0210] Long cycle life [0211] Long service life [0212] Low investment costs [0213] Low operating costs

[0214] The provided substance meets the set requirements to a large extent.

[0215] The substance is [0216] inorganic [0217] safe [0218] with a long service life [0219] recyclable [0220] available in very large quantities [0221] highly economical [0222] operates in the temperature range up to 1,000 C. [0223] can be simultaneously charged and discharged [0224] can be simply manufactured.

[0225] In particular the fact that, as a sensitive high-temperature storage means, the provided substance can be simultaneously charged and discharged makes it possible to operate a controllable, permanently running storage power plant. In this way power generation deficiencies can be compensated for or higher demands can be met.

[0226] Furthermore heat storage means can be used in particular for wind farms or solar parks and thus render the power generated there capable of providing base load power as a package solution.

[0227] Furthermore, small heat storage units can be used for example for a complete power supply for example for residential buildings. These small units are heated for example by renewable energy sources and are then used as a routine replacement for the complete power supply, i.e. supply of thermal power and electricity, for residential buildings.

[0228] Furthermore, small heat storage units in machines of all types can be used for the purpose of power supply.

[0229] Furthermore, after cogeneration, electrical power can be made transportable in the form of heat storage means without line systems.

[0230] Vehicles can also be powered in this way. After cogeneration by heat/power coupling has taken place, heat storage means which are regularly replaced like batteries can operate electric motors, comparably to lithium batteries.

[0231] The equipment for the conversion of heat into electrical power can be provided as an integral component of the storage device take place or in units which are independent thereof.

EXAMPLE

[0232] The provided substance is a filter cake which first of all must be subjected to a thermal treatment, i.e. it must be heated slowly up to 1,000 C. In this case first of all the water content of the filter cake is evaporated, then up to 1,000 C. all minerals which are unstable in the high-temperature range are calcined. Then the substance consists only of oxides as well as stable inorganic phases such as nepheline or others. This substance is cooled and forms the storage mass.

[0233] The charging (i.e. heating) of the storage mass takes place directly by means of embedded resistance wires or heating elements, i.e. resistance wires in ceramic sleeves or other systems. By means of corresponding control devices the storage mass can be constantly adjusted to arbitrary temperatures.

[0234] The discharging takes place by means of a water circulation which passes through the storage mass at a suitable and optimal point of the temperature range/steam pressure. Water is evaporated, steam drives turbines, current is generated. The excess steam is guided back again into the water circulation by means of cooling equipment (cooling tower).

[0235] Optimal conditions can be set by means of the specific thermal conduction of the heat storage medium between the delivery of heat (hottest point) and the heat consumption.

[0236] The heat storage material is consolidated with heating means for the supply of heat and the pipe system (water) for the heat dissipation to form a block. This block is thermally insulated against the exterior.

[0237] The statement that the heat storage system characterised in this way can be simultaneously charged and discharged is crucial. As a rule storage facilities are designed so that either charging or discharging takes place; cf. in this connection pumped storage facilities. On the other hand, with the possibility of the simultaneous charging by renewable energy sources and the discharging it is possible to construct stable storage power plants which are capable of providing base load power.

[0238] Currently the most important heat storage system for sensitive heat storage means is water. This system is characterised in that it operates with water ideally in a temperature range from 40-90 C., since above 100 C. water is present as steam. Thus water has a T von 50 C.

[0239] In contrast to this, the heat storage system which operates with a storage mass which has been produced from the provided substance can operate at temperatures up to 1,000 C., i.e. the substance can evaporate water above a temperature of 100 C. and thus can operate with a T of 900 C. Thus this system is a high-temperature storage system.

EXAMPLE

[0240] Comparison of the Sensitive Water/ALFERROCK Heat Storage Means

[0241] Calculation of the Amount of Heat which can be Stored

[0242] The amount of heat Q which a storage material can store is calculated according to the following equation:

[00004]$Q=m*\mathrm{cp}*.Math..Math.T=*\mathrm{cp}*V*.Math..Math.T.Math.\left[J\right]$$m=\mathrm{mass}.Math.\left[\mathrm{kg}\right]$$c_p=\mathrm{specific}.Math..Math.\mathrm{thermal}.Math..Math.\mathrm{capacity}.Math.\left[\frac{\mathrm{kJ}}{\mathrm{kg}.Math..Math.K}\right]$$=\mathrm{density}.Math.\left[\frac{\mathrm{kg}}{m.Math..Math.3}\right]$$V=\mathrm{volume}.Math.\left[m^3\right]$$*c_p=\mathrm{volumetric}.Math..Math.\mathrm{thermal}.Math..Math.\mathrm{capacity}.Math.\left[\frac{\mathrm{kJ}}{m.Math..Math.3.Math..Math.K}\right]$$.Math..Math.T=\mathrm{temperature}.Math..Math.\mathrm{range}.Math.\left[K\right]$$Q_{\left(1.Math.{m.Math.}^3\right)}=\mathrm{volumetric}.Math..Math.\mathrm{thermal}.Math..Math.\mathrm{capaticy}*.Math..Math.T.Math.\left[J\right]$

[0243] 1. Water (for 1 m.sup.3)

[00005]$=998.2\left[\frac{\mathrm{kg}}{m.Math..Math.3}\right]$$c_p=4.182\left[\frac{\mathrm{kJ}}{\mathrm{kg}.Math..Math.K}\right]$$*c_p=4.Math.\text{,}.Math.175\left[\frac{\mathrm{kJ}}{m.Math..Math.3.Math..Math.K}\right]$$.Math..Math.T=50.Math..Math.K$$Q=4.Math.\text{,}.Math.175\left[\frac{\mathrm{kJ}}{m.Math..Math.3.Math..Math.K}\right]*50.Math..Math.K*1.Math..Math.m^3$$Q=208.7*{10}^3.Math..Math.\mathrm{kJ}$

[0244] Converted into Wh:

[0245] 1 J=1 Wh/3600

[0246] Q.sub.water=57.88 kWh

[0247] 2. ALFERROCK (for 1 m.sup.3)

[00006]$=3.Math.\text{,}.Math.930\left[\frac{\mathrm{kg}}{m.Math..Math.3}\right]$$c_p=1.16\left[\frac{\mathrm{kJ}}{\mathrm{kg}.Math..Math.K}\right]$$*c_p=4.Math.\text{,}.Math.558.8\left[\frac{\mathrm{kJ}}{m.Math..Math.3.Math..Math.K}\right]$$.Math..Math.T=900.Math..Math.K$$Q=4.Math.\text{,}.Math.558.8\left[\frac{\mathrm{kJ}}{m.Math..Math.3.Math..Math.K}\right]*900.Math..Math.K*1.Math..Math.m^3$$Q=4.Math.\text{,}.Math.102.9*{10}^3.Math..Math.\mathrm{kJ}$

[0248] Converted into Wh:

[0249] 1 J=1 Wh/3600

[0250] QALFERROCK=1.1397 MWh

[0251] 3. Comparison ALFERROCK/water

[00007]$\frac{Q.Math..Math.\mathrm{ALFERROCK}}{Q.Math..Math.\mathrm{water}}=\frac{1.1397.Math..Math.\mathrm{MWh}}{57.88.Math..Math.\mathrm{kWh}}=19.7$

[0252] ALFERROCK can store 19.7 times the amount of heat at an operating temperature up to 1,000 C.

[0253] The ALFERROCK high-temperature heat storage medium can also be used in an outstanding manner at lower temperatures as a heat storage means, heat exchanger and thermostat. It is worthy of note that during tempering of the provided substance the increase in the density from

[00008]$3.63.Math..Math.\frac{g}{\mathrm{cm}.Math..Math.3}$

at 100 C. to

[0254] [00009]$3.93.Math..Math.\frac{g}{\mathrm{cm}.Math..Math.3}$

at 1,000 C. does not decline, but remains constant at

[00010]$3.93.Math..Math.\frac{g}{\mathrm{cm}.Math..Math.3}.$

Thus the value *c.sub.p is increased by 9%.

[0255] In the following Table 5 the storable quantities of heat in the region of approximately 200 C., 300 C., 400 C., 500 C. and 600 C. are set out and present very attractive values.

TABLE-US-00005 TABLE 5 Requirements for energy accumulators Temperature [ C.] [00011]$\begin{array}{c}{C}_p\\ \left[\frac{\mathrm{kJ}}{\mathrm{kg}.Math..Math.K}\right]\end{array}$ Density [kg/m.sup.3] [00012]$\begin{array}{c}.Math.*.Math.\mathrm{cp}.Math.*.Math.V\\ \left[{10}^6.Math.\frac{J}{K}\right]\end{array}$ T [K] Q (for 1 m.sup.3) [J] 208.32 0.928 3930 3.65 100 365 * 10.sup.6 307.26 0.960 3930 3.77 200 754 * 10.sup.6 406.17 0.989 3930 3.88 300 1.16 * 10.sup.9 505.07 1.020 3930 4.01 400 1.60 * 10.sup.9 584.20 1.037 3930 4.08 500 2.04 * 10.sup.9