US20120312292A1 - Device and system for the intermediate storage of thermal energy - Google Patents

Abstract

A device for the intermediate storage of thermal energy and to a system comprising a plurality of such devices is provided. The device has a solids store and a pipe system, which is formed of individual pipes and runs through the solids store and through which an energy carrier medium flows. In order to be able to quickly and uniformly charge the solids store with thermal energy or discharge thermal energy therefrom, heat conducting elements are provided, each forming heat transmission regions with the individual pipes and each extending into the regions of the solids store that are free of individual pipes. The heat conducting elements also have a higher heat conductivity than the solids store.

Description

• This nonprovisional application is a continuation of International Application No. PCT/EP2010/007909, which was filed on Dec. 23, 2010, and which claims priority to German Patent Application No. DE 10 2009 060 911.3, which was filed in Germany on Dec. 31, 2009, and which are both herein incorporated by reference.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to a device and system for the intermediate storage of thermal energy.
• 2. Description of the Background Art
• In view of the dwindling primary raw materials worldwide as resources for energy production, regenerative and alternative concepts are becoming more and more important. Examples are the use of solar energy in solar thermal power plants or the use of waste heat from industrial manufacturing processes. Because these alternative forms of energy are coupled to solar radiation or to certain industrial processes, however, their continuous availability is not guaranteed. Their practical usability therefore depends greatly on the possible intermediate storage of energy accumulating at a certain time and the ability to provide it at a later time. The storage of thermal energy therefore has a key importance in the development and implementation of alternative concepts for energy recovery.
• Known systems for storing thermal energy comprise substantially a heat source, for example, a solar collector or an internal combustion engine, a heat accumulator with a thermally chargeable and dischargeable storage medium and at least one heat circuit for charging and discharging the heat accumulator, in which a working medium flows from the heat source to the heat point of use or from the heat accumulator to the heat point of use.
• The storage medium has central importance for the effectiveness of the entire system. It must satisfy substantially two requirements: namely, on the one hand, have a high thermal storage capacity, i.e., have as great a capability as possible to take up thermal energy per unit weight and unit volume, and, on the other, be characterized by a high thermal conductivity, i.e., the heat must be able to spread as rapidly as possible in the storage medium.
• Fluids that meet both of the above criteria are already known as a storage medium. For the low-temperature range to about 100° C., water is suitable as a storage medium, because it is available cost-effectively and is characterized by its high thermal storage capacity. A disadvantage, however, is the rapid increase in vapor pressure at temperatures above 100° C., which necessitates costly pressure vessels. For this reason, fluids with a higher boiling point are used for higher temperature ranges, e.g., heat transfer oils or salt melts. This is associated with a considerable increase in investment costs, however. A convective heat transfer results owing to the circulation of liquid storage media with the advantage of a rapid and uniform charging and discharging of the storage medium.
• Apart from liquid accumulators, solid storage media are also known, which may include, for example, metals such as steel or cast iron. Such metals are well suited as a storage medium because of their high specific weight and their high thermal conductivity but lead to high investment costs.
• DE 10 2008 047 557 A1 also discloses a solid storage medium made of a mineral material, through which a plurality of axis-parallel pipes run, in which an energy transfer medium flows in the heat circuit. The thermal energy of the energy transfer medium is introduced into the storage medium via the pipes and is distributed there gradually and uniformly over the entire volume. The mutual distance of the individual pipes and thereby their number are predetermined by the thermal conductivity of the storage material, because it must be assured for the practical usability of the heat accumulator that the thermal energy spreads within the entire storage device as rapidly and uniformly as possible in order to make possible a rapid charging and discharging of the energy storage device.
• Solid storage media made of a mineral material in fact have the great advantage of being able to be produced cost-effectively but during their use it must be accepted that they have only a limited thermal conductivity. In order to achieve a satisfactory heat conduction, nevertheless, the pipes are arranged at a relatively high density in the solid storage media, as a result of which their number and thereby again the production costs increase. A cost advantage achieved with the use of a mineral solid storage medium is thereby again partially nullified.
SUMMARY OF THE INVENTION
• It is therefore an object of the present invention to improve prior-art solid storage media in regard to their economy and function.
• The starting point for the invention comprises heat accumulators in which charging and discharging of the solid storage medium occurs via an energy transfer medium flowing in the pipe system, whereby the temperature gradient between the energy transfer medium and the solid storage medium is the driving force for the heat flow. Moreover, the thermal conductivity of the employed storage materials has a significant effect on the charging and discharging of the solid storage medium. For example, steel in comparison with concrete has a thermal conductivity that is higher by a factor of about 40, with the result that the thermal energy provided in the pipe system spreads only slowly in the solid storage medium. In a solid storage medium made of concrete, this has the result that areas, directly surrounding the individual pipes, of the solid storage medium are charged very rapidly thermally, however, with increasing distance from the individual pipes a great temperature drop is to be observed (FIG. 12a), and therefore a relatively long time interval is necessary until a very largely equalized energy state over the entire volume of the solid storage medium has been achieved. To shorten the charging and discharging times for the solid storage medium, the radial distance of the individual pipes to one another would have to be reduced consistently, which, however, because of the associated higher number of individual pipes would negatively impact the economy of such a heat accumulator.
• The invention resolves this problem with the aid of heat conducting elements, which have a higher thermal conductivity compared with the material of the solid storage medium and extend proceeding from the individual pipes into the solid storage medium. Preferred materials for the heat conducting elements are metals such as, for example, steel, aluminum, copper, or graphite, which can be available both as ground or compressed natural graphite and expanded or compressed natural graphite (graphite film). The heat conducting elements in this way form flow pathways for the rapid transport of thermal energy over greater distances within the solid body, from which then a uniform loading of the storage volume occurs over only relatively short distances. This allows for a rapid and uniform charging and discharging of the solid storage medium with the best possible utilization of the storage volume. The invention is thus characterized by a high specific heat output of the solid storage medium also at relatively great radial distances of the individual pipes of the pipe system and thus combines the seemingly contradictory requirements for a high thermal conductivity, on the one hand, and a cost-effective storage material, on the other.
• Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
• FIG. 1 shows an oblique view of the heat accumulator of the invention;
• FIG. 2 shows a longitudinal section through the heat accumulator shown inFIG. 1;
• FIG. 3 shows a cross section through the heat accumulator shown inFIG. 2 along line III-III;
• FIG. 4 shows an oblique view of a first embodiment of the heat accumulator of the invention without a depiction of the solid storage medium;
• FIG. 5 shows an oblique view of a second embodiment of a heat accumulator according to the invention;
• FIG. 6 shows an oblique view of a third embodiment of a heat accumulator according to the invention;
• FIG. 7aandbshow details for the embodiment illustrated inFIG. 5;
• FIG. 8 shows an exploded view of a fourth embodiment of a device of the invention;
• FIG. 9 shows a detail of a fifth embodiment of a heat accumulator of the invention in the heat transfer region;
• FIG. 10 shows an oblique view of a sixth embodiment of a heat accumulator according to the invention;
• FIG. 11 shows an oblique view of a seventh embodiment of a heat accumulator according to the invention;
• FIG. 12ashows an oblique view of an eighth embodiment of a heat accumulator according to the invention;
• FIG. 12bshows a detail of the heat accumulator illustrated inFIG. 12a;
• FIG. 13ashows an oblique view of a ninth embodiment of a heat accumulator according to the invention;
• FIG. 13bshows a detail of the heat accumulator illustrated inFIG. 13a;
• FIG. 14 shows an oblique view of a heat accumulator with horizontal bracing; and
• FIG. 15aandbshow cross sections through a heat accumulator of the invention with an illustration of the heat distribution during charging of the heat accumulator.
DETAILED DESCRIPTION
• FIG. 1 shows a heat accumulator1 of the invention in an oblique view andFIGS. 2 and 3 in associated sections. An essential element of heat accumulator1 is a block-shapedsolid storage medium2 with a considerable longitudinal direction, whose longitudinal ends are formed by front faces3 and4.Solid storage medium2 in the present example is made of concrete, which can occur both in in-situ concrete casting and also, as will be described in greater detail below, with precast concrete parts. Other materials such as, for example, ceramic, brick, or fireclay are also within the scope of the invention. Free-flowing mineral material can also be used as the solid storage medium, which is then available as fill within a housing. The dimensions of heat accumulator1 are not specified and are determined depending on the particular intended application. A preferred embodiment of a heat accumulator1 has a length of about 18 m, a height of about 4 m, and a width of about 2.5 m to 3 m.
• Another element of the invention is the pipe system labeled with thenumber5, which comprises a plurality ofindividual pipes6.Individual pipes6 go throughsolid storage medium2 in its longitudinal direction in an axis-parallel position, which is made clear inFIG. 1 by the omission ofsolid storage medium2 in a middle longitudinal section.Individual pipes6 in this case extend beyond front faces3 and4 with the formation of a projection.
• As is evident primarily fromFIG. 3,individual pipes6 are arranged preferably equidistantly in a plurality of horizontal levels, lying plane-parallel one over another, wherebyindividual pipes6 of two adjacent levels may have a lateral offset by half the horizontal distance of twoindividual pipes6. In this way, a uniform distribution ofindividual pipes6 over the cross section ofsolid storage medium2 arises, which results in a uniform introduction of the thermal energy intosolid storage medium2. In the case of solid storage media made of in-situ concrete, to maintain the above-described pattern over the entire length ofindividual pipes6, spacers, for example, made ofsteel mats8 are arranged withinsolid storage medium2 at predefined longitudinal distances in a cross-sectional level in each case; the cross and longitudinal rods of said spacers correspond to the predetermined pattern and are used for fasteningindividual pipes6. With greater longitudinal distances, the reinforcement ofindividual steel mats8 byprofile frames9 is possible (FIGS. 1 and 2).
• Individual pipes6 end as already described in cross-sectional levels, which run at a clear distance to front faces3 and4, for example, at a distance of 40 cm.Front plates11 and12, which are provided with through-openings according to the pattern ofindividual pipes6, are arranged in these cross-sectional levels, therefore plane-parallel to front faces3 and4.Individual pipes6 open on the back offace plates11 and12 into collection channels, which in turn are connected via connectingpipe sections16 to adistributor17 orcollector18, each of which have apipe connection19 for the inlet or outlet of heat accumulator1 (FIG. 2).
• A fluid energy transfer medium flows throughpipe system5, for example, a heat transfer oil, which is supplied to the circulation and transports the thermal energy for charging heat accumulator1 from a heat source, for example, a solar collector, to heat accumulator1 or for discharging accumulator1 the thermal energy present in accumulator1 to a user. The thermal energy inherent to the energy transfer medium is thereby first transferred topipe system5, from where it is fed intosolid storage medium2.
• To avoid damage due to temperature-induced different linear expansions betweensolid storage medium2 andpipe system5, a mechanical decoupling of these two components is provided, which can occur, for example, by providing a clear gap or a gap, filled with a thermally conductive material, betweensolid storage medium2 andpipe system5.
• FIGS. 4 to 11 show different embodiments of the invention, which enable a high specific heat output ofsolid storage medium2 in the case of simultaneously large radial distances ofindividual pipes6 ofpipe system5. To clarify the construction method and functioning of a heat accumulator1 of the invention, only small partial details ofsolid storage medium2 with its essential features are shown on a larger scale there.FIGS. 4 to 11 are therefore to be viewed together withFIGS. 1 to 3.
• FIG. 4 shows a first embodiment of heat conducting elements according to the invention in an oblique view of a partial detail ofpipe system5, whereby for a clearer illustrationsolid storage medium2 itself is not shown. Seen areindividual pipes6 in horizontally stacked levels and running axis-parallel to one another, said pipes which are arranged from one level to another with a lateral offset in the height of half the mutual lateral distance, so that the distance between twoindividual pipes6 is uniform at each place insolid storage medium2. In addition,individual pipes6 are mechanically decoupled fromsolid storage medium2, for example, by sheathing with a graphite film (not shown).
• Whereas primarily a heat distribution insolid storage medium2 occurs in the axial direction inindividual pipes6 due to the energy transfer medium flowing therein, horizontalheat conducting elements20 and verticalheat conducting elements21 are provided for lateral distribution of the thermal energy.Heat conducting elements20,21 in the present exemplary embodiment has flat metal bars.
• Horizontalheat conducting elements20 are placed with their longitudinal axis transverse toindividual pipes6 of a level on these and due to their length extend over severalindividual pipes6. The axial distance of horizontalheat conducting elements20 is within a range from 5 cm to 30 cm and is 15 cm in the present example. The contact-based placement of horizontalheat conducting elements20 onindividual pipes6 forms a substantially linear heat transfer region via which the thermal energy is introduced fromindividual pipes6 in to horizontalheat conducting elements20.
• In their simplest embodiment, because of their own weight,heat conducting elements20 rest onindividual pipes6 without other securing measures. Preferred, however, is their fixation at a predetermined place, for example, by welding or binding with binding wire. Another type of fixation can also occur by the interlacing of horizontalheat conducting elements20 inindividual pipes6 lying in a level, wherebyheat conducting element20 alternates the attachment side fromindividual bar6 toindividual bar6, therefore is guided once above and once below past individual bars6. Because of the elastic properties ofheat conducting elements20, the restoring forces in this case result in a pressing ofheat conducting elements20 againstindividual pipes6.
• For heat distribution in the vertical direction, the embodiment of the invention shown inFIG. 4 provides verticalheat conducting elements21, which in the present example also includes flat metal bars and which because of their length bridge at least the vertical distance of twoindividual pipes6 lying one above another. The fixation of verticalheat conducting elements21 can occur as previously described, namely, by welding, binding, or interlacing. The exemplary embodiment shown inFIG. 4 discloses, moreover, another option in which the upper end of verticalheat conducting elements21 is bent into a U-shape to form ahook22 and is hung withhook22 onindividual pipes6, whereas the opposite end lies againstindividual pipe6 lying below. Becausehook22 in part follows the perimeter ofindividual pipes6, an enlargement of the heat transfer region and thereby an improved heat transfer result.
• Apipe system5 prepared in this way can be provided for the completion ofsolid storage medium2, for example, in a closed formwork and concreted. In this way asolid storage medium2 of concrete forms, which is run through in the longitudinal direction byindividual pipes6 ofpipe system5 and in the horizontal and vertical lateral direction in addition by horizontalheat conducting elements20 and verticalheat conducting elements21. This type ofsolid storage medium2 can be charged or discharged uniformly with thermal energy with a very short time despite the limited thermal conductivity of the storage material.
• FIG. 5 shows a partial detail of a second embodiment of a heat accumulator1 of the invention. In this embodiment,solid storage medium2 has prefabricatedelements23, which are placed one on top of another inhorizontal layers24 in a modular manner, wherebyindividual pipes6 ofpipe system5 run in the horizontal butt joints ofadjacent layers24.
• As already mentioned, only the functional principle of heat accumulator1 is to be clarified with the type of presentation selected inFIG. 5, which is why only a small partial detail of heat accumulator1 is shown. In reality,prefabricated elements23, depending on the size ofsolid storage medium2, extend over the entire width and/or length ofsolid storage medium2 or only over a part thereof when a number ofprefabricated elements23 are strung together. The thickness ofprefabricated elements23 corresponds to the vertical distance ofindividual pipes6 ofpipe system5.
• Groove-shapedrecesses25 are formed in the top side ofprefabricated elements23 for receivingindividual pipes6 in the butt joint. Groove-shapedrecesses25 have a rounded bottom and a depth and width somewhat larger than the diameter ofindividual pipes6, which results in a U-shaped cross section of groove-shapedrecesses25.
• Groove-shapedrecesses25 extend over the entire length ofsolid storage medium2, so that if a number ofprefabricated elements23 are placed one behind the other in the longitudinal direction, groove-shapedrecesses25 run aligned over the entire length. The lateral distance of groove-shapedrecesses25 among one another corresponds to the lateral distance ofindividual pipes6, whereby depending on the width of prefabricated elements23 aprefabricated element23 may have up to a plurality of groove-shapedrecesses25.
• In addition, in the butt joint of twoprefabricated elements23 an upper horizontalheat conducting element26 and a lower horizontalheat conducting element27 can be seen, each of which has an thin-walled, planar structure and may include, for example, sheet metal or a graphite film.Heat conducting elements26 and27 extend over the entire width and/or length ofprefabricated elements23 or also only over a partial width and/or partial length, whereby in the latter case the stringing together of a number ofheat conducting elements26 and27 is possible.
• Whereas the upperheat conducting element26 is formed planar over its entire surface, the lowerheat conducting element27 in the regions assigned to groove-shapedrecesses25 has U-shaped bent areas to form through-shapedseats28 forindividual pipes6. In this way seats28 with their outer circumference fit form-fittingly in groove-shapedrecesses25 ofprefabricated elements23 and with their inner circumference onindividual pipes6.
• The building of such asolid storage medium2 occurs by the sequential layering of the individual components, as is shown inFIG. 5 in the right exploded illustration; the finished state is shown inFIG. 5 in the left section. In this state,individual pipes6 are embedded between the upperheat conducting element26 and lowerheat conducting element27. It is assured by the weight ofoverlying layers24 ofsolid storage medium2 that contact is created, on the one hand, betweenheat conducting elements26 and27 andprefabricated elements23 and, on the other, betweenheat conducting elements26 and27 andindividual pipes6. Thus, the thermal energy provided inindividual pipes6 can be introduced viaheat conducting elements26 and27 deep intoprefabricated elements23, or vice versa for the discharge process.
• The additional embodiment of the invention, shown inFIG. 6, corresponds very largely to the embodiment described forFIG. 5, so that the statements made in that regard apply. In contrast, the lower horizontalheat conducting element27′ is expanded by a verticalheat conducting bar29, which is disposed along an outer surface line ofseat28 ofheat conducting element27′ and is fixedly connected toseat28. Heat conductingbar29 thus extends at right angles to the main extension plane of horizontalheat conducting element27′.
• Prefabricated element23 is formed in a corresponding manner; i.e., it has avertical slot30, which extends from the bottom of groove-shapedrecess25 into prefabricatedelement23, as far as is possible for structural reasons. In the present case,slot30 extends over half the thickness ofprefabricated element23.
• It becomes clear fromFIG. 7aandbthat the invention for receivingindividual pipes6 provides not only solutions according toFIGS. 5 and 6, where groove-shapedrecesses25 completely receivingindividual pipes6 are arranged in only one of theprefabricated elements23 forming the joint (FIG. 7b). AsFIG. 7ashows, a design, symmetric to the joint plane, of the seats is also within the scope of the invention in which groove-shapedrecesses25″, whose depth is slightly more than half of the diameter ofindividual pipes6, are provided both on the lower side of an upperprefabricated element23 and also on the upper side of a lowerprefabricated element23. TheU-shaped seats28″ of horizontalheat conducting elements26″ and27″, arranged in the joint, fit here form-fittingly intolongitudinal grooves25″. As also in the previously described embodiments of the invention,heat conducting elements26″ and27″ advantageously can already be connected form-fittingly toprefabricated element23 during the production ofprefabricated elements23, for example, by insertion into the formwork before the concreting.
• The advantage of this embodiment of the invention is thatindividual pipes6 ofpipe system5, after being placed inseat28″ of a lowerheat conducting element27″ with their lower circumference form a projection in the butt joint in a lowerprefabricated element23. After theprefabricated elements23 of overlyinglayer24 are placed on top, thus a centering of the two overlyingprefabricated elements23 occurs via a form fit. A centering of the prefabricated elements can also be achieved by separate form-fitting component in the butt joint, such as, for example, groove bars and female connectors or pin and indentation.
• In the embodiments of the invention according toFIGS. 5 to 7, the longitudinal grooves can also be made larger in cross section than the individual pipes running through therein. The resulting gap between the individual pipe and heat conducting element makes it possible to compensate for production- and assembly-related tolerances. For an effective heat transfer between the individual pipe and solid storage medium to be nevertheless assured, the gap is filled with a thermally highly conductive material such as, e.g., ground natural graphite or metal filings or a suitable fluid.
• FIG. 8 discloses another embodiment of the invention in an exploded illustration. Asingle pipe6, from which heat conductingelements31 extend to the left and right and up and down, is visible in the center.Heat conducting elements31 can be both surface elements and strip elements and are welded, for example, to the outer circumference ofindividual pipes6. In the quadrants formed thereby,prefabricated elements32 are inserted alongindividual pipes6; these can have a bevel at the edge facingindividual pipes6 to assure complete contact betweenheat conducting elements31 andprefabricated elements32. As an alternative to the use ofprefabricated elements32, the production ofsolid storage medium2 also by in-situ concrete casting is an option here as well.
• The detail of another embodiment of the invention, as shown inFIG. 9, has a heat conducting element33, which includes a centralheat conducting pipe34, to which the radially upper and lower and left andright bars35 are connected. This type of heat conducting element33 is used advantageously in conjunction withprefabricated elements32, whereby it is already concreted during their production and is thus an integral component ofprefabricated element32.
• Heat conductingpipe34 surroundsindividual pipes6 ofpipe system5 in a coaxial manner, whereby the annular gap betweenheat conducting pipe34 andindividual pipe6 is filled with a thermallyconductive material41 such as, e.g., ground natural graphite or metal filings, to decouple mechanicallysolid storage medium2 andpipe system5 from each other and at the same time to assure the heat transfer fromindividual pipes6 to heat conducting element33. According to a variation of this embodiment of the invention, this function can also be assumed by fluids with which the annular gap sealed in each case on the front side is filled. Such embodiments of the invention are capable of compensating for dimensional differences betweenpipe system5 andsolid storage medium2, which can greatly facilitate the assembly of heat accumulator1.
• FIG. 10 shows an alternative embodiment of the invention, in which prefabricated star-shapedheat conducting elements36 are attached at axial distances toindividual pipes6.Heat conducting elements36 are made up of acylindrical section37, to which the radial bars38 connect at a uniform angular distance of 45°.Cylindrical section37 has an inside diameter, which corresponds somewhat to the outer diameter ofindividual pipes6, so thatheat conducting elements36 can be pushed ontoindividual pipes6, beforesolid storage medium2 is completed in in-situ concrete casting.
• The particular feature of the embodiment of the invention as shown inFIG. 11 is the use of planarheat conducting elements39, which are equipped withopenings40, which correspond in size and arrangement to the pattern ofindividual pipes6 ofpipe system5. It is possible as a result to slipheat conducting elements39 axially ontoindividual pipes6, which can occur either before concreting in the case of in-situ concrete solid storage media, or by sandwich-like insertion ofheat conducting elements36 between twoprefabricated elements41, as shown inFIG. 11. The heat transfer region betweenindividual pipes6 and heat conductingelement39 is formed by the reveal surfaces ofopenings40, which lie against the outer circumference ofindividual pipes6.
• FIGS. 12aandbshow another embodiment of the invention. Asolid storage medium2 is evident which includes a plurality of concreteprefabricated elements46. Concreteprefabricated elements46 are stacked one above the other in horizontal layers, whereby a planar horizontalheat conducting element47 is arranged in the butt joints of two overlying layers in each case. This produces a structure ofsolid storage medium2, in which concreteprefabricated elements46 andheat conducting elements47 are arranged alternately in the vertical direction. Heat conductingelement47 in this case corresponds in structure and material selection to those described in regard toFIGS. 1 to 11 and can include, for example, a sheet or a film.
• Concreteprefabricated elements46 of a horizontal layer have among one another a horizontal lateral distance to the neighboring concreteprefabricated element46; this results in alongitudinal gap49 aligned in the horizontal direction and extending over the entire height of concreteprefabricated elements46.Longitudinal gap49 is used to receiveindividual pipes6 ofpipe system5, which run at half the height of alongitudinal gap49 in the middle between the horizontalheat conducting elements47. The width oflongitudinal gap49 therefore corresponds at least to the diameter ofindividual pipes6.
• To transfer the thermal energy fromindividual pipes6 to horizontalheat conducting elements47 and vice versa, in each case strip-shapedheat conducting elements48 which enable a vertical heat transport and whoselong side50, assigned toindividual pipe6, is made concave in order to create as great a heat transfer region is possible, are arranged inlongitudinal gaps49. The oppositelong side51 of verticalheat conducting elements48 is made planar, in order to form as large a contact region as possible with horizontalheat conducting elements47. In cross section, in each case two suchheat conducting elements48 filllongitudinal gap49 above and below anindividual pipe6.
• During charging ofsolid storage medium2, therefore, the thermal energy supplied inindividual pipes6 is taken up linearly via verticalheat conducting elements48 and further fed into the planar horizontalheat conducting elements47, where a rapid and extensive distribution of the thermal energy insolid storage medium2 occurs. Proceeding fromheat conducting elements47, the supplying of concreteprefabricated elements46 with thermal energy for its storage then occurs.
• A variation of this embodiment is shown inFIG. 13aandb.Solid storage medium2 shown there corresponds substantially in it basic structure with its alternate arrangement of horizontal layers of concreteprefabricated elements52 and horizontalheat conducting elements47 to the medium described inFIG. 12aandb.Solid storage medium2 according toFIG. 13aandb, however, differs in that concreteprefabricated elements52 of a horizontal layer lie against one another with contact on the side; therefore there is no continuouslongitudinal gap49. Nevertheless, to be able to guideindividual pipes6 throughsolid storage medium2, the opposite long sides of two concreteprefabricated elements52 in the area of their upper and/or lower longitudinal edges each have an offset53.Offsets53 lying opposite in this way form, in the butt joint of two concreteprefabricated parts52,channel54, which is intended to receiveindividual pipes6 and is open only to horizontalheat conducting element47. To improve the heat conduction betweenindividual pipes6 and horizontalheat conducting elements47, heat-conducting molded parts55 are inserted inchannel54; these molded parts with their concave side form a bearing surface forindividual pipes6 and with their opposite planar side a bearing surface toward horizontalheat conducting element47.
• FIG. 14 disclosessolid storage medium2 made up ofprefabricated elements56. To stabilizesolid storage medium2,prefabricated elements56 are held together by horizontal prestressing anchors57, which extend from the one vertical long side ofsolid storage medium2 to the opposite side. To even out the load transfer,load distribution plates58 are arranged betweensolid storage medium2 and the anchor heads of prestressing anchors57.
• The effective mode of action of a heat accumulator1 of the invention compared with conventional heat accumulators comes across clearly inFIGS. 15aandb.FIG. 15ashows the heat distribution over the cross section of asolid storage medium2 without the heat conducting elements of the invention during thermal charging.Lines42 to45 represent in each case places with the same temperature, also called isotherms. The distance ofisotherms42 to45 is a measure of the temperature gradient withinsolid storage medium2. An approximately square region is evident, which is surrounded byisotherm42 and surrounds the centralindividual pipe6 and describes the zone with the highest temperature withinsolid storage medium2. The temperature insolid storage medium2 declines steadily with increasing distance from centralindividual pipe6. Only regions directly adjacent to otherindividual pipes6 have local, narrowly limited zones with a higher temperature.
• In contrast, the temperature profile shown inFIG. 15bof asolid storage medium2 of the invention withinisotherm42 shows an extensive zone of a maximum temperature, which extends over nearly the entire section surrounded by allindividual pipes6. A temperature drop is determined substantially between outerindividual pipes6 and the surface ofsolid storage medium2, whereisotherms42 to45 lie relatively close together and thereby indicate a large temperature gradient. It becomes clear as a result that the heat conducting elements of the invention contribute extremely effectively to a rapid and uniform supplying of the solid storage medium with thermal energy.
• Not shown in the drawing but still within the scope of the invention are embodiments of the invention, in which the heat conducting elements includes a paste-like or free-flowing material, for example, of metal filings or metal powder, which is applied like the already described sheets or graphite films in a uniform thickness between two layers of the solid body. These materials have the advantage that with the application of the load from the overlying layers a deformation and adaptation of the heat conducting elements to the surface contour of the layers occur and thus despite possible tolerances a snug butting of the heat conducting elements against the solid storage medium and thereby optimal heat transfer are assured. So that these materials do not escape from the solid storage medium in the edge regions, a sheathing of these materials can be provided.
• According to another embodiment of the invention, which is not shown, it is provided to design the heat conducting elements as a grid structure, which can be achieved in a simple way, for example, by the use of a wire-mesh-like network. Here as well, an automatic adaptation to possible irregularities occurs in the butt joint during the placement of two prefabricated parts one on top of another. Furthermore, the manageability and economy of the invention can be increased further with the saving of weight and materials.
• The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.

Claims (22)

1. A device for intermediate storage of thermal energy, the device comprising:

a solid storage medium;

a pipe system formed by individual pipes, the pipe system configured to run through the solid storage medium and through which an energy transfer medium flows;

heat conducting elements, which with the individual pipes, form heat transfer regions and which extend into the regions free of the individual pipes of the solid storage medium, the heat conducting elements having a higher thermal conductivity than the solid storage medium.

2. The device according toclaim 1, wherein the heat conducting elements have a relative movability relative to the individual pipes in the heat transfer regions.

3. The device according toclaim 1, wherein the heat conducting elements lie tangentially against the individual pipes to form the heat transfer regions.

4. The device according toclaim 1, wherein the heat conducting elements surround the individual pipes, in each case, at least partially on a peripheral side to form the heat transfer regions.

5. The device according toclaim 1, wherein the heat conducting elements are arranged in two layers and the individual pipes are each arranged between the two layers.

6. The device according toclaim 1, wherein the heat conducting elements are arranged each at a radial distance to the individual pipes and to regions between the heat conducting elements to form the heat transfer regions, and wherein the individual pipes are each filled with a heat-conducting material.

7. The device according toclaim 1, wherein the heat conducting elements are arranged in horizontal and/or vertical levels, each running substantially in the longitudinal axis of the individual pipes.

8. The device according toclaim 1, wherein the heat conducting elements are each arranged in a perpendicular plane to the longitudinal axis of the individual pipes.

9. The device according toclaim 1, wherein the heat conducting elements each extend linearly in the solid storage medium.

10. The device according toclaim 1, wherein the heat conducting elements each extend in a planar manner in the solid storage medium.

11. The device according toclaim 1, wherein the heat conducting elements each extend in the form of a planar grid in the solid storage medium.

12. The device according toclaim 1, wherein the solid body is made of in-situ concrete.

13. The device according toclaim 1, wherein the solid body is made of concrete prefabricated parts, which when joined with the formation of butt joints form the solid storage medium.

14. The device according toclaim 13, wherein in the butt joints centering aids are arranged, which determine a relative position of two adjacent precast concrete parts relative to one another.

15. The device according toclaim 13, wherein the heat conducting elements are each arranged in the butt joints between the concrete prefabricated parts.

16. The device according toclaim 13, wherein the precast concrete parts in the surfaces forming the butt joints have groove-shaped recesses for receiving the individual pipes.

17. The device according toclaim 16, wherein the groove-shaped recesses are each arranged only in one of the precast concrete parts forming the butt joints.

18. The device according toclaim 1, wherein the heat conducting elements are formed of metal, aluminum, magnesium, manganese, lead, iron, copper, zinc, silicon, or alloys thereof.

19. The device according toclaim 1, wherein the heat conducting elements are formed of graphite or compressed expanded graphite.

20. The device according toclaim 1, wherein the heat conducting elements have a free-flowing or paste-like material.

21. The device according toclaim 20, wherein the free-flowing or paste-like material is arranged within a sheath.

22. A system for intermediate storage of thermal energy with at least two heat accumulators, which can be supplied in series or parallel with the energy transfer medium, wherein the at least two heat accumulators are formed according to the device according toclaim 1.

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