CA1081935A

CA1081935A - Heat store and installation for the utilisation of solar energy

Info

Publication number: CA1081935A
Application number: CA250,987A
Authority: CA
Inventors: Ursula Kreibich; Rolf Schmid
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1975-04-28
Filing date: 1976-04-26
Publication date: 1980-07-22
Also published as: ES447356A1; FR2309823B1; CH617767A5; GB1538533A; JPS51130937A; FR2309823A1; DE2523234A1

Abstract

Abstract of the Disclosure A heat accumulator is provided which has a heat exchanger embedded in a crystalline substance and has a maximum operating tempe-rature greater than the melting point of the crystalline sub-stance. The latter and the heat exchanger are integrated in a moulding bonded by means of crosslinked plastic. Preferably, the crosslinked plastic is crystalline and, at the same time, forms the crystalline substance. There is also provided an installat-ion for the utilization of solar energy. The installation com-prises a heat accumulator as described hereinbefore, a useful-heat exchanger and a solar energy absorber, which are connected together to form 8 heat transfer circuit. The installation is of particular use for the production of warm water.

Description

8~g35 The invellt]on re~Lates to a nea~ acc~lulator which has a hea~ e~chan~er wllicll is el~edded in a crysLallinc su~s~ance and has a maximum operating tempera-ture grea-ter than the melt,ing poin-t of the crys-talline substance, and to a use thereof.
Known installa-tions for the s-torage of solar energy, was-te heat, such as was-te s-team energy and off-gas,energy and the like generally consis-t of a collector, which collects the hea-t to be stored, a sys-tem of pipelines, which con-tains heat transfer liquids, and the actual heat s-tore. In most cases, the lat-ter contains a salt mix-ture or salt solution as the storage material.
When salt solutions and salt melts are used in heat ~ccu-m~rs,-there are frequently severe corrosion problems. For -this reason, corrosion-resistant metal containers are in the ~ain required to contain the sal,ts, but these containers are heavy and conduct heat well. Both properties are dis-advantageous, quite apart from the fact that such containers make the total installation expensive. Furthermore, fractures and leaks of the sal-t containers and pipes must always be expected and this results in -the extremely undesir-able exuda-tion of the solu-tions or melts.
The continuous change in the state of aggregation from solid to liquid and vice versa places a-particular stress on the containers. As is known, every time salts remelt thermal stresses arise, which-lead to bulging of the salt containerD The volume of the bulge is completely filled by the salt mel-t. Af-ter the melt has solidified, the ., .

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precondition for the next bulging then exists. Stress of this type in particular very rapidly leads to the installation devel-oping leaks, as feared.
Accordingly, the invention provides heat accumulator which has a heat exchanger which is embedded in a crystalline substance and has a maximum operating temperature greater than the melting point of the crystalline substance, the crystalline substance being a cross-linked plastic and forming a molding wherein the heat exchanger is integrated.
Thus, disadvantages of the prior art are avoided by the crystalline substance and the heat exchanger being integrated in a moulding which is bonded by means of cross-linked plastic, the cross-linked plastic being crystalline and, at the same time, forming the crystalline substanc~. In the present document and in accordance with the present invention, a crystalline plastic or synthetic resin is to be understood as a product which is usually partially crystalline. The preferred embodiment at the same time avoids a further considerable disadvantage of the known heat accumulators, that is to say the fact that it is not always possible, with the known salt-containing storage media, even when different salts are mixed, to obtain the particular melting point which is optimum for the intended application. A virtually free choice of the melting point of the storage substance is of fundamental importance, particularly for the storage of solar energy. Depending on the position and construction of the heat-ing system it must be possible, for optimum utilisation, to employ -storage substances which have different melting points. However, this is not ensured in the case of salts and salt mixtures. If a salt mixture which does not correspond to a ~_A , , ' , - ; . . .

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~18~935 eu-tec-tic coinposl-tion is chosen, deraixing phenomena always occur when -the melt solidifies. Only purely eu-teetic mix-tures crystallise in a cons-tan-t composition. However, euteetie melts have a grea-t tendency -to supercooling and must therefore be seeded, This, in turn, however, has the eonsequence that here again demixing phenomena gradually mani-fest themselves. It is not possible to realise every desired mel-ting point by choosing eutec-tie salt mixtures, if only because the number of eu-tectics is limited. Further-more, some eutec-tic melting points ean only be obtained by ehoosing expensi~e salts, whieh a priori preeludesthe praetical realisation of sueh euteetics. `
In comparison with salts, the crystalline, erosslinked plas-tic contained in the heat aeeumulator aeeording to the inven~Dn exhibits the peeuliarity, and the advantage, that no ehange in -the state of aggregation (that is to say from "solid" to "liquid" and viee versa) oeeurs when i-t is eharged wi-th heat energy and when this energy is diseharged. It is true that the erystallites eontained in the plastie melt in the region of the erystallite melting poin-t. However, the solid state, and thus the given shape, remains preserved. At the same time, in mos-t eases the plastie turns transparent and there may be a tra~sition to the rubbery-elas-tie state, with simul-t,aneous absorption of the heat of fusion~ By suitable ehoiee of the basic components - preferably polyesters and their acids - and of the eros~linking system (epoxide eompounds, ~ensity of eross]inking) used for the manufaeture of the _ L~
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~08~l935 crosslinked crystalline plas-tic i-t is possible, above all in the temperature range of about 30-70C, which is of most in-teres-t in prac-~ice, to obtain vir-tually any desired crystal-li-te melting point and thus to suit the heat-stor.ing substance in an optimum manner to its intended use.
The invention is explained in more detail below with the aid of an illustrative embodimen-t shown in the drawing.
The single figure in the drawing shows a section through a heat accumula~according to the invention in use in an installation for the utilisation of solar energy.
The two-s-tage installation for the utilisation of solar energy which is shown comprises, as the cen-tral part, a heat acc~ulat~r 1 and also, in addition, two solar energy absorbers.

-2 and 3, -two useful-heat exchangers 4 and 5, two circulating pumps 6 and 7 and a pipe system which is provided wi-th valves -to 11 and which joins the parts mentioned, in a manner which is yet to be described, to two separate heat transfer liquid circuits The heat accumulator 1 comprises two concentri~ bloc~s 13 and 14, which consist of a crosslinked crystalline plastic which will be specified in more detail below and are separa-ted by an insulating layer 12, and is provided with an all-round heat insulating foam jacket 15 The crystallite melting point of the outer block 14 is set at 45C and that of the inner block 13 is se-t at 60C. The foam jacket is designed in -two layers, the ou-ter layer 15a consisting of rigid foam and the inner layer 15 consis-ting of sof-t elastic plastic foam.

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-The insulatillg layer 12 also consis-ts of a sof-t elas-tic foam.
By this means changes in volume which arise on warming and cooling are evened ou~.
A hea-t exchanger, in the form of copper -tube coils 16 and 17 respec-tively, is embedded in each of the plas-tic blocks 13 and lL~, which form -the storage media, the heat exchanger forming an integral body wi-th -the particular plastic block.
Of course, virtually any o-ther type of heat exchanger is also suitable, in place of copper -tube coils. In particular, for reasons of insulation, it is appropriate to use -those heat exchangers in which -the heat transfer medium in the course of its passage flows -through the heat exchanger from the periph-eral zonesto the central zonesor vice versa. As is shown in the drawing, a heat exchanger of this type can be realised, for example, by two or more communicating coaxial -tube coils.
The coils can, for example, ~lso be provided with fins, which increase the surface area, or the like In order to keep the heat losses due to radiation and -the like as small as possible, the heat accumula~or 1 ~as a cylindrical shape. As is known, this geome-tric shape represents a favourable compromise between the demand for a surface to volume ratio which is as small as possible and shaping which meets -the requirements in practice. Of course, other geometric shapes are also suitable and possible.
In contrast to the heat accumulator 1, the solar energy absorbers 2 and 3, only a sec-tion of which is shown in the drawing, are designed wi-th a large surface area~ They are ., ~ 9 ~
of a construc-tion which is in i-tself ~own and each consists of a flat heat e~changer, 22 and 23 respectively, which is arranged in a casing, 18 and 19 respec-tively, with double glazing, 20 and 21 respec-tively. The surface area of the two absorbers together is approximately 30 m2.
The two use~ul-hea-t exchangers 4 and 5 each consis-t of a heat--insulated ke-ttle, 24 and 25 respectively, and in each kettle two coils 26 and 27 and, respectively? 28 and 29 and an electric heater, 30 and 31 respectively, are located.
Each ket-tle also has an inlet, 32 and 33 respectively, and an outlet, 34 and 35 respectively. The two ke-ttles 24 and 25 are connected in series. They are, for example, in an ins-tallation, which is not shown, for the production o~
warm wa-ter, in which case cold water passes through the inlet 32 into the kettle 24 and warm wa-ter can be removed from the kettle 25 through its outlet 35.
The two heat exchange coils 27 and 29 are also connected in series They ~orm part of the circui-t of a heating installation, which is not shown, for warm wa-ter and serve to heat the heating water.
As can be seen from the drawing, two separate circuits are provided for the heat transfer med3um, which in this case L also is wa-ter. One circuit comprises the heat exchanger 16, which is embedded in the outer block 14 of the heat acc~n~
the solar energy absorber and collector 2, the circulating pump 6 and the exchanger coil 26, which is located in the use~ul-heat exchanger 4 9 and the three-wa~ valves 8 and 9, .. . .

which are located in -the pipes, ~rhich are no-t shown, The sec~
ond circui-t comprises the heat exchanger 17 of the inner hea-t storage block 13, the solar energy absorber 3, the circulating pump 7 and -the exchanger coil 28 in the useful-hea-t exchanger 5, as well as the two three-way valves 10 alld 11, .
In order to s-tore the solar energy absorbed by the absorbers and collectors 2 and 3, the valves 8 to 11 are brought into the position shown and the circulating pumps are switched on. The heat transfer media warmed in the collectors now flow through the particular heat exchangersin the storage blocks 13 and 14 and through the useful-heat exchangers 4 and 5, In this way, on the one hand~ -the storage blocks 13 and lL~ are charged and, on the other hand, the use~ul water in the kettles 24 and 25, and thus also indirectly the useful water in the heat exchanger coils 27 and 29, is warmed. The useful-heat exchanger 4 has the function of a pre-heater. The temperature reached in this pre-heater is about 35C. The useful-heat exchanger 5 heats the useful water, pre-warmed in this way, to a tempera-ture of about 50C, ready for use. This -two-stage system permits optimum utilisa-tion of the solar energy.
In order to discharge the heat accumulator, the three way valves 8-11 are brought into a position which bridges the solar energy collectors and excludes these from the cycles. The useful water is thus heated, with extremely small losses, by neans of the heat contained ln the accumulato~

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gL~8~935 In periods in which -the solar irradia-tion is weaker, or is no-t adequate for comple-te charging of the heat accumulator, the lacking amount of heat is supplied by -the electric heaters provided in the useful--hea-t exchangers. A mixed opera-tion, in which, for example, charging of the accumulator is effected via solar energy in one circuit and via elec-trical energy in the o-ther circuit9-is also possible Of course, the shown assembly of -the individual parts of the ins-tallation for the utilisation of solar energy is not the only possible assembly For example, it can also be advantageous, for certain purposes, -to provide even further s-tages and/or to connect several s-tages in series ins-tead of in parallel. Of course, a single stage can alsc be adequate for some purposes.
I-t is, fur-thermore, also possible to design the heat accu~
m~a~itself as a solar energy collector. Of course, it is then necessary to choose a geome-tric shape which has as large a surface area as possible, coupled with a small volume.
It is evident that the heat accumu~ator according to the invention cannot only be employed on earth but, in particular because of the absence of a liquid phase, is also fully capable of functioning in a vacuum, that is to say9 for example, in space, and is therefore particularly suitable for such applications.
The crystalline crosslinked plastic of the heat accumulator according to the invention is preferably a casting resin of a type which permi-ts the manufac-ture of mouldings having a . .
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~ 3 5 lar~e volume.
Of course, it is no-t absolutely necessary for the heat-storing ma-terial in -the heat store according -to the inven-tion to be a crys-talline, crosslinked plas-tic. For example, it could also consist of a foam of crosslinked plastic having closed cells which enclose a sui-table storage medium.
~urthermore, it is also possible to fill crystalline sub-stances, such as, for example, paraffin, palmitic acid, lauric acid and -the li~e, into sui-table containers of small volu~e and to pot these by means of a casting resin, prefer-ably of a crystalline, crosslinked polymer of the types indicated further above, and thus to form an integral body together with the embedded heat exchanger.
Several plastics, which are particularly suitable as - ~ ;
a heat-s-toring substance, and the manufacture thereof are discussed in more detail in the text which follows.
~ he heat accumulator according to the in~en~ion preferably contains, as the crystalline, crosslinked plastic, an epoxide resin or polyurethane resin or polyester resin or a mixture of these synthetic resins which all contain, as crystallite-form-ing blocks, radicals of long-chain dicarboxylic acids or di-alcohols of the formula I

X - A - X (I) in which Xl and x2 each represent a -CO.O- group or a -O-group and in which A deno-tes a substantially linear radical, in which polymethylene chains alternate re~llarly with ether . . .

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. ~ ... ... ~., . , . -~)8~335 oxygen a-toms or carboxylic acid es-ter groups, and the quotient Z/Q, wherein Z i.s -the number of CH2 groups present in the recurring structural element of the radical A and Q is the number o~ oxygen bridges presen-t in the recurring structural element of -the radical A, must be a-t least 3 and preferably at least 5 or 6 and wherein, fur-thermore, -the total number of the carbon atoms present in the radical A in alternating carbon chains is a-t leas-t 30, Epoxide resins of this type which all contain radicals of long-chain dicarboxylic acids of the formula I are described, for example, in a publication by Hans Batzer et al. in "Die : :
angewandte makromolekulare Chemie" 29/30 (1973), on page 349 :: .
to 412.
Such special epoxide resins also include, in par-ticular, crystalline, crosslinked epoxide resins (L), which are manu-fac-tured by reaction of epoxide compoundsg containing two or more epoxide groups 9 a) with polyester-polycarboxylic acids A, which essentially contain segments of the formula IV ::

-to-(cH2)n~-co-(cH2)m-co~p- (IV) in which n and m are iden-tical or dif~erent and denote 2 or a higher number than 2, and ~o which the condition n ~ m = 6 to 30 applies 9 and in which p denotes a number from 2 to L~o ~
which 9 however, is sufficiently large -that the segment con-tains at least 30 -CH2- groups 9 and b) with polyester-polycarboxylic acids B which essentially .

, ~(38~935 con-tain segments of` the formula V

~[O~Rl~O~CO~R2~COlq (V ) in which R- and R2 are iden.tical or different and denote an alkylene radical with a-t least 2 C atoms in the chain and in which, per 0 bri.dge, an average of at least 3.5 and at most ~0 C atoms, wi-thout -taking into account the C atoms of -the -C0-0- radicals, are present in -the chain, and wherein the radicals Rl and R2 together con-tain at least one alkyl ~roup or cycloalkyl group or one aryl group as a substi-tuent for one ~ :
H atom or one ring-forming, optionally substituted alkylene group as a subs-tituent for 2 H atoms of a chain, and in which q denotes a number from.2 to ~0, whic~ however,is sufficiently large that the segment contains at least 30 C
atoms, without taking into account the C atoms of the -C0.0-radicals, in the chain, and c) if appropriate, with curing agents C, and, if appropriate~ :
in the presence of accelerators, ~ .
in a ratio such that 0.5 -to 1.2 equivalents of polyester-polycarboxylic acid are present per equivalen-t of epoxide compound, that 5/10 to 9/10 of these 0 5 to 1,2 equivalents -are at-tribu-table to the polyester-polycarboxylic acid A and the remaining 5/10 to 1/10 to -the polyester-polycarboxylic acid B., and -that up to 0.6 equivalen-t of curing agent C is present per equivalent of epoxide compound, with the proviso that, in the cases in which only difunctional epoxide com- :
pounds and difunctional polyester-polycarboxylic acids ~ and .:
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, : ' B are employed, ~he epo~ide groups must be present in excess and the reaction ~ith a curing agent C is essen-tial, Pre-ferably,-the concli-tion n -~ m = 6 to 24 applies to the formula IV.
PrePerably, the procedure followed for -the manu-fac-ture of the epoxide resins (L) is such that 0,7 to 1.2, especially O,9 -to 1 1, equivalents of polyes-ter-polycarboxylic ~ .
acid are present per equivalent of epoxide compound. ~:
The polyester-polycarboxylic acids A and B used in the reaction can,for practical purposes,be manufactured by ~he same basic process, by esterification of corresponding ali-phatic dialcohols and aliphatic dicarboxylic acids.or by forming esters of sui-table derivatives of these alcohols and dicarboxylic acids, such as, for example, the anhydrides, acid chlorides and the like. The dicarboxylic acids must be ;
presen-t in excess, . ~here small amounts oP aliphatic polyalcohols with at least 3 OH groups, especially glycerol, are also used, branched, that is to say at least 3-functional, polyester-polycarboxylic acids A and B are obtained.
Branched polyester-polycarboxylic acids A and B,which are obtained if smaIl amo~nts of polycarboxylic acids, or their anhydrides, with at least 3 carboxyl groups (such as, Por example" trimellitic acid) are also present during the manuPacture oP the polyester-polycarboxylic acids, are equally suitable for the manufactu~e of the epoxide resins (L).
However, it is als~ possible to employ branched poly - 13 - . :.

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es-ter-polycarboxylic acids A and B, ~Jhich are oh-tainable by es-terification of the terminal OH groups o~ long-chain poly-ester-polyols, especially of polyes-ter-diols, with poly-ca-rboxylic acids which con-taln at least 3 -CO.OH groups, such as, ~or example, -trimellitic acid, or wi-th corresponding anhydrides.
The basic rules for the manu~ac-ture of the polyester~
polycarboxylic acids A and B used as starting substances for the epoxide resins (L) in other respec-ts entirely correspond to those ~hich have to be observed for the manufacture of the "long-chai~ dicarboxylic acids" employed according to Bri-tish Patent 1,164,584, and which are described in detail in this Bri-tish patent. Further data on -the basic principles of the manu~acture of such long-chain, aliphatic polyester- : .
polycarboxylic acids are also to be found in a publica-tion by Hans Batzer et al. in "Die Angewandte Makromolekulare Chemie"
1973, page 349-412.
Examples of suitable polyester-polycarboxylic acids A
are those based on the ~ollo~ing polyalcohols and polycarhoxy-lic acids:
16 mols of adipic acid - 15 mols of hexane-1,6-diol 21 mols of succinic acid - 20 mols o~ butane-1,4-diol ll mols of sebacic acid - lO mols o~ hexane-1,6-diol Glycerol - succinic acid - butanediol (1:24:21) 11 mols o.~ succinic acid - lO mols of butanediol 11 mols of dodecanedicarboxylic acid - lO mols of hexanediol ll mols of dodecanedicarboxylic acid - lO mols o~ butanediol _ 1L~ _ :
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' ~8~935 11 mols ol dodecanedicarboxylic acid - 10 mols of propane-1,3-diol 7 mols of dodecanedicarboxylic acid - 6 mols of hexanediol 7 mols of dodecanedicarboxylic acid - 6 mols of dodecanediol 7 mols of sebacic acid - 6 mols of dodecanediol 11 mols of sebacic acid - 6 mols of dodecanediol Trimethylhexanediol - succinic anhydride - bu-tanediol (1:30:27) 11 mols of dodecanedicarboxylic acid - 10 mols of ethylene glycol 5 mols of decanedicarboxylic acid - 4 mols of dodecanediol 11 mols of dec~nedicarboxylic acid - 10 mols of hexanediol Examples of suitable polyester-polycarboxylic acids B
are those based on the following polyalcohols and poly-carboxylic acids:
11 mols of sebacic acid - 10 mols of neopentylglycol 8 mols of adipic acid - 7 mols of neopentylglycol 13 mols of adipic acid - 12 mols of neopentylglycol 8 mols of adipic acid - 7 m~ls of trimethylhexanediol 8 mols of trimethyladipic acid - 7 mols of neopentylglycol 1~ mols of adipic acid - 13 mols of neopentylglycol 4 mols of dimerised fatty acid - 3 mols of diethylene glycol 4 mols of dimerised fatty acid - 3 mols of hexanediol

3 mols of dimerised fatty acid - 2 mols of hexanediol Glycerol - adipic acid - butanediol - neopentylglycol (1:9:3:3) Trimethylhexanediol - adipic acid - hexanediol - neopentyl glycol (1:8:2:3) 14 moJ.s of s~.ccinic acid - 13 mols o:~ neopentylglycol `

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4 mols o~ hexahydrophthalic anhydride ~ 3 mols o~ neopentyl~
glycol.
With regard -to the alipha-tic polyes-ter-polycarboxylic acids descri~ed, it must also be s-ta-ted -tha-t -the same or similar compounds are also -the basic structural lmits of the abovementioned more general epoxide resins and polyurethane resins and polyes-ter resins which contain radicals of the formula I. General epoxide resins of this type are also manufactured by analogous processes, the only dif~erence being that only one polyester-polycarboxylic acid is employed in each case.
As epoxide compounds con-taining two or more epoxide groups it is possible -to employ virtually all the polyepoxy compounds known,to -those skilled in the art, from publications and patent specifications. One or more dif~erent epoxide compounds can be reacted. Triglycidyl isocyanurate and triglycidyl compounds which contain one or more hydantoin groups and/or dihydrouracil groups, especially epoxide com-po~nds of the ~ormula III

O C113 >1 ~ > ~ - C113 / \
CH - Cll-CII~-N N-C1~2-ll;Cl12-1 ~ C~2 F 2 (III) C~1 c~

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~ 81935 are par-ticularly suitable.
In principle, the reaction ~or the manu~acture of -the epoxide resins (L) can be carried out either in 1 stage or in several stages. If -the epoxide compounds used have at leas-t 3 epoxide groups, and polyester-dicarboxylic acids A and B are employed, it is possible, for example, to carry ou-t -the reaction in 1 stage, that is to say to start ~rom a reaction mixture which contains all the reactants simultaneously. It is possible -to proGeed in exactly the same way (that is -to say in 1 stage) if, instead of the dicarboxylic acids, polyester-polycarboxylic acids A and B which have at least 3 carboxyl groups are employed, In the converse case, that is to say when using polyester-carboxylic acids A and B containing at least 3 carboxyl groups, and using diepoxy compounds, working in 1 stage is again possible and is the normal method of reaction for such cases.
If only diepoxy compounds and only polyester-dicarboxylic acids are employed, it is only possible to work in one stage if an excess of epoxide compounds is used and at the same time a polycarboxylic acid anhydride is added.
In the multi-s~age method, an adduct containing epoxide groups is initially manufactured, in a first stage, from the epoxide compounds and the polyester-polycarboxylic acids A and/or B, preferably using 0.5 to 1 equivalent o~
polyester-polycarboxylic acid per 2 equivalents of epoxide compounds. In a second reaction stage, the crosslinking is then carried out, by reaction of the adducts with the remainder :,^ ' .

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of the polyes-ter~polycarboxylic acids A and/or B It is also possible -to proceed by carrying out -the crosslinking in the second s-tage in the presence o:~ cus-tornary curing agen-ts.
It is also possible addi-tionally -to adcl ye-t further monorneric epoxide compounds and correspondingly larger amoun-ts of curing agents.
As custorna~y curing agents for epoxide resins i-t is possible to emplo-y all the subs-tances which are described in the numerous publications and paten-ts rela-ting -to epoxide resins In-ter alia, the following subs-tances may be listed here: compo~lds wi-th amino groups, polyalcohols, poly~
carboxylic acids and their anhydrides, acid amides, polyesters, phenol-formaldehyde condensates and amino-resin precondensa-tes.
Ter-tiary amines and imidazoles may be men-tioned as examples of sui-table accelerators.
The sta-temen-ts made above with regard to the single stage and multi-stage procedure for the manufacture of the epoxide resins (L) analogously also apply quite generally to the manufacture of epoxide resins in a wider sense, which resins all contain, as crystallite-forming blocks, radicals of long chain dicarboxylic acids or dialcohols of the formula I.
Furthermore, the following applies -to -the manufac-ture of epoxide resins in general:
- The reaction is preferably carried out in the melt.
For this, preferably temperatures of between 50 and 200C
and reaction times of more than 1 hour and up to about 20 hours are required In principle, the reaction can also be - ,. ,, - ~

~ L~8~935 carried out ill solu-tion.
Of course, the plas-tics can contai.n further customary addi-tives, such as fil].ers, reinforcing aKents, mould-release agen-ts, agents to protect aga].ns-t aging, flameproofing sub-s-tances, dyestuffs or pigments.
Suitable fillers or reinforcing agents are fibrous or pulverulent inorganic or organi.c substances Quar-tz powder, aluminium oxide trihydrate, mica, aluminium powder, iron oxide, ground dolomite, chalk powder, gypsum, slate powder, vnburnt kaolin (bolus), burnt kaolin, glass fi.bres, boron fibres and asbes-tos fibres may be men-ti.oned A content of ma-terials, in the form of fibres and powders, which assis-t the heat con-duc-tivity can aIso prove parti.cularly advantageous. Examples of such materials are metals (for example aluminium powder), carbon, such as carbon black and graphi.te in powder form, and carbon fibres.
For the purpose of optimum and accelerated development of the crystal structure of the polymers it is also appropriate to add nucleating agents, such as phthalocyanines, car.bon black or the like le 1 ~ 80 g (0.567 equivalent) of an acid polyester con-sisting of 11 mols of sebacic acid and 10 mols of hexanediol (prepared by the melt process) were warmed to 100C and mixed well with 9L~.6 g (0 567 equivalent) of the triglyci.dyl com-povnd of -the formula III and the system was evacuated and the mix-ture poured in-to an Anticorodal mould which had dimensions - 19 ~

~08~93~
of 200 x 200 x 21~ mm, had been pre-warmed -to 120C and had been treated with a silicone mould-release agen-t. A copper tube whlch was about 130 cm long, onto which copper fins had been soldered and which was bent -to and fro 5 times in a meandering manner,was located in -the castin~ mould. The internal width of the tube was 4 mm and the wall -thickness was 6 mm, The tube runs in the spiral had a heigh-t of 17 cm and a spacing of 2,5 cm each.
The epoxide resin system was warmed -to 140C ~or ]6 hours, A crystalline, tough storage system was obtained.
The epoxide resin had a crystalli-te mel-ting point of 62~C and an enthalpy of melting of 20 cal/g, The epoxide resin was rubbery-elastic above the mel-ting poin-t, One sur~ace of the accumulator was coloured black and, with a glass insulation, was mounted as a collector and exposed to the sun, After an exposure -time of 5 hours, the centre of the collector had warmed to 72C. It was completely rubbery-elastic and thus had absorbed (stored) the heat of ,~
fusion as well as the specific heat. This means that energy of about 1,000 kcal/m2 had been absorbed by -the collector over a period of 5 hours. The experiment was carried out in Basle on 21.2,1975, Example 2 A further heat accumulator with dimensions o~ 200 x 200 x 48 mm was cast analogously to Example 1.
The accumulator was insulated with polystyrene fQam 10 cm thick and warmed with warm water at 65Cc Aiter 5 hours , .. : .

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the crystalline poly~er was completely "mel-ted", that is to say it was in a r~bbery-elastic state, a temperature of 63C
being recorded in the centre of the panel and on the surface.
Wa-ter at 22 was passed through the accumula~or wa~med to 63 C. I-t was possible to warm 2,7 1 o~ wa-ter -to 40C.
The experiment shows that, of the 34 kcal heat o~
crystallisation and -the 20 kcal for the specific heat, about ~8 kcal could be recovered, A collector according to the state of' the art (200 x 600 mrn sheet copper painted black) was connected to an ac ~ ~or according to Example 1. After exposure to the sun for 4 hoursS a -tempera-ture~ of 74C was measured in the storage panel. Thus, it was possible to charge ~he accumulator by solar energy by means of the collector which was present, that i:~ to say to convert the accumulator into the rubbery-~elastic state.
The experiment was carried out on 27,2,].975 in Baslè
(sunny weather but somewhat hazy).
Example 4 An accumulator with dimensions of 200 x 200 x 54 mm was manufactured analogously to Example 1 but in place of the -sebacic acid polyester a polyester ob-tained from 11 mols of adipic acid and 10 mols of hexanediol was used. The acc~ulator was warmed analogously to Example 3. After exposure to the sun for 4 hours, the accumulator reached a tempera~ure of 51C `
(initial ternperature = 31C). I-t could be charged in this ;
way, that is to say converted into the rubbery-elastic state.

. . .

... . ..
.

:': : . ' .;
~ .
.~

. : . . ..

iL081935 The e~erimen-t was carried ou-t on 26.2.1975 in Basle (sunny bu-t very hazy).
Exam~le 5 24.85 kg of a polyes-ter ob-tained from 11 mols of adipic acid and 10 mols of hexanediol (prepared by the melt process) with an acid equivalent weight of 1,130 were mel-ted and warmed -to 140C. 3.67 kg of the -triepoxide compound of the formula III and 330 g of phthalocyanine blue were ad-mixed to the melt. After adding 36.7 g of dimethylamino-benzylamine, the system was again mixed well and the mix-ture .: . .
was poured into a cylindrical, slightly conical cylinder -30 cm in diame-ter and 38 cm in height. A copper spiral (external diameter = 6 mm, internal diameter = 4 mm) was laid in the still liquid warm mix-ture, the tubes being laid down with spacings of 2.5-3 cm. After curing at 140C for 16 hours, a moulding was obtained which was rubbery-elastic when ho-t and which, wi-thout additional.insulation, started to crystallise at the edge at 40C only after 24 hours. For about 10 hours the temperature at a distance of about 2 cm from the edge remained at 40- 41C. Inside -the moulding, the temperature remained above 35C for a considerably longer period (40 hours)~ .
The experiment shows that, even with relatively modest insulation, it is possible, particularly in the case of relatively large mouldings, to store the heat for more than two days, -the outer layer of the store servi.ng as an additional insulation ~, . .

.
. . .
-: ' . ' ' '. , ' ' .. . . ." .

Example 6 A mouldirlg was manufac-tured in the same way using an 11:10 sebacic acid - hexanediol polyes-ter in place of the adipic acid - hexanediol polyes-ter, 1.0 equivalen-t of the epoxide resin used in Exarnple 5 being used per 1.0 equivalent of polyes-ter The moulding was manu:Eactured withou-t the addition of ph-thalocyanine blue and exhibited a crys-tallisa--tion -temperature of 48-49C.
Example 7 23.2 kg of an acid polyester obtained from 11 mols -of dodecanedioic acid and 10 mols of hexanediol (acid equivalent weight ~ 643) and 1.13 kg of an aci.d polyester obtained from 8 mols o~ adipic acid and 7 mols of neopentylglycol (equiva-lent weight = 700) are warmed to 110C and mixed well with 2.61 kg of the he-terocyclic -triepoxide compound lII (equivalent weight = 167) (equivalent ratio = 0.9:1.0:1.0) and 270 g of a naph-thoic acid, as the nucleating agent, and 70 g of l-methyl-imidazole, as the accelerator, the system is evacuated and the mixture is poured into a mould, analogously to Example 5.
After curing for 24 hours a-t 130C, a moulding is obtained which is rubbery-elastic when ho-t and which c.hanged into the partially crystalline state at room temperature, with the release of heat. After release from the mould, the moulding is insulated by means of 20 cm of polys-tyrene foam (cork base panel) and warmed to 80 by means of -the copper spiral (1.88 kg ofcopper-tube per 27.0 kg of resin). On cooling, the temperature at the centre of the moulding is : : .

.
.

.

~8~935 64C after 1~> hours and still 61C after 44 hours, The temperature o~ an equally large con-tainer filled wi-th water is 60 after 10 hours and only 50C after 15 hours. Thus, considerably be-tter storage of the energy is made possible by the crystalline, crosslinked plastic.
Crys-tallite melting point = 68C
Enthalpy of mel-ting = 19.2 cal/g Using the same resin mix-ture as in Example 7 an identical moulding is cast but -this, however, in addi-tion to the copper spirals, additionally contains 6 2 kg of paraffin, filled into tubes 3.5 cm in diameter. On cooling, this moulding has a temperature of 66C after 10 hours and a temperature of 61C af-ter 30 hours This moulding with -the potted paraffin thus also displays good storage of heat.
Example 9 63 kg of the following mixture: 1.0 equivalent of a polyester obtained from 11 mols of adipic acid and 10 mols of hexanediol (equivalent weight = 1,080), 1 0 équivalen-t of the heterocyclic triepoxide compound III (equivalent weigh-t =
167), 3% by weight of finely powdered urea-formaldehyde resin, 1% by wéight of melamine, 0.1% by weight of ~-Cu ph-thalocyanine (blue) and 0.3/0 by weight of l-methylimidazole, which had been evacuated at llODC, were cast in a rectangular mould which had a base area of 17 x 100 cm and contained a copper spiral with an internal diameter of 3 mm and an ex-ternal , .~. :; : :

;.

;. , : : . ~ ; .

~ 0 ~ 35 diame-ter of 10 mm (a to-tal of 5 kg of copper). The M.iX-ture is cured over -the copper spiral at 120C (about 40 hours) and, after cooling, is released from -the mould, Af-ter insulating with 20 cm of polys-tyrene foam, the moulding is warmed -to 80. On cooling~-the following curve is obtained for the ~all in tempera-ture:
aE-ter 70 hours: L~8C
after 160 hours: ~4C
The crystallites o~ the epoxide resin crystallise out at 44-48 and are able to maintain the tempera-ture at this level ,or a surprisingly long period of time. Despite the relatively small thickness of the mouldings, -these already exhibit a good storage effect.

1,324 g = 0.7 equivalent of an acid polyester obtained from 10 mols of dodecanedioic acid and 9 mols of dodecanediol with an equivalen-t weight o~ 1,892 are warmed to 110C and mixed well with 117 g = 0.7 equivalent of the heterocyclic epoxide resin III and 4 g of l-methylimidazole, the system is evacuated and the mixture is poured into a 1,5 1 glass beaker which contains a copper spiral. After curing for 16 hours at 130C, a white moulding which is rubbery-elastic when warm and crystalline at room temperature is obtained, The moulding is warmed to 100C and, when insulated with 10 cm of polystyrene, is cooled. The temperature in the centre is 73C after 2 hours and 71C after 4 hours and thereafter falls more rapidly again at a rate of 3-4/hour. In -the range . .

.
, 3l~)B~935 be-tween 1:l an~ 73C, the moulding glves an entha:lpy of crystalllsation of 23 cal/g.
]e 11 -1 0 equivalen-t of a polyes-ter ob-tained from 10 mols of sebacic acid and 11 mols of hexane-1,6-diol is reac-ted hot (70C) with 1.2 mols of toluylene 2,4-diisocyana-te, with exclusion of moisture and in a ni-trogen atmosphere. The adduct has an isocyanate equivalent weight of ~62 (-theory 868).
862 g = 1 0 equivalent of -the resul-ting adduct are warmed -to 80C and mixed with 44.6 g (= 1.0 equivalent) o~
hexanetriol, the system is evacuated and the mixture is poured into a glass beaker which contains a copper spiral After curing for 2 hours at 70C, for 2 hours a-t 120C and for 2 hours a-t 140C 9 a moulding which is rubbery-e]astic when ho-t and white and crys-talline at room temperature is obtained:
crystallite melting point = 51C
enthalpy of melting = 16 ca~/g The accumulator is warmed to 100C and le~t to cool in an insulation of 10 cm thick polystyrene foam. As a result of the crys-tallisa-tion o~ the crosslir~ed polymer, cooling is retarded in the temperature range between 45 and 35C, , ' .
1 0 equivalent of the polyester described in ~xample 11 (OH equivalent weight = 1,006) is reacted, at 150C, with 1 mol of maleic anhydride, a poly-ester with terminal carboxylic acids and double bonds resulting (equivalent weigh-t = 1,070).
70 g of the resulting polyes-ter are mlxed, at 70C, wi-th 30 g ~ 26 ~

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, , - . . ~

~4~81935 of s-tyrene and 2 g of 505S strength benzoyl peroxi.de and, a~ter evacuating the system, -the mix-ture is poured into a tube 3.5 cm in diarneter. After curinK for 2 hours at 70C, for 2 hours at 120C and for 2 hours at 140C, a mouldinK is obtaine~d which is rubbery-elastic when hot and changes in-to the crystalline state on cooling.
Crystalli-te melting poin-t = ~3C
En-thalpy of melting = 8 cal/g

Claims

New Claims

1. Heat accumulator which has a heat exchanger which is embedded in a crystalline substance and has a maximum operating tempera-ture greater than the melting point of the crystalline sub-stance, the crystalline substance being a crosslinked plastic and forming a molding wherein the heat exchanger is inte-grated.

2. Heat accumulator according to Claim 1, wherein the moulding contains flameproofing fillers.

3. Heat accumulator according to Claim 1, wherein the moulding contains nucleating agents.

4.Heat accumulator according to Claim 1, wherein the moulding is reinforced by fibre material.

5. Heat accumulator according to Claim 1, wherein the moulding contains at least two crystalline zones with different mel-ting points.

6. Heat accumulator according to Claim 5, wherein at least one of the zones contains a heat exchanger with separate connections.

7. Heat accumulator according to Claim 5, wherein at least some of the heat exchangers integrated in the individual zones are connected in series.

8.Heat accumulator according to Claim 1, wherein the moulding is surrounded by a jacket of heat-insulating insulating material, this jacket forming an integral part of the moulding and consisting of at least two layers of foam, the innermost of which is soft elastic.

9. Heat accumulator according to Claim 5, wherein at least two of the zones are insulated from one another by a heat-insulating layer.

10. Heat accumulator according to Claim 9, wherein the insula-ting layer forms an integral part of the moulding and con-sists of a soft elastic foam.

11. Heat accumulator according to Claim 1, wherein the moulding has a surface area which is small in comparison with its volume and is spherical or cylindrical.

12. Heat accumulator according to Claim 5, wherein the zones are arranged concentrically to one another.

13. Heat accumulator according to Claim 12, wherein the inner zones have a higher melting point than the outer zones.

14. Heat accumulator according to Claim 1, wherein the moulding has a surface area which absorbs heat which is large in comparison with its volume.

15. Heat accumulator according to Claim 14, wherein a region of the surface area is designed as a solar energy absorber.

16. Heat accumulator according to Claim 1, wherein the melting point of the crystalline substance or substances is the range of about 30° - 70°C.

17. Heat accumulator according to Claim 5, wherein one zone has a melting point in the range of about 30° - 50°C
and another zone has a melting point in the range of about 40° - 70°C.

18. Heat accumulator according to Claim 1, wherein the cry-stalline substance is an epoxide resin or polyurethane resin or polyester resin or a mixture of these synthetic resins which all contain, as crystallite-forming blocks, radicals of long-chain dicarboxylic acids or dialcohols of the formula I

X1 - A - X2 (I) in which X1 and X2 each represent a -CO.O- group or a -O-group and in which A denotes a substantially linear radical, in which polymethylene chains alternate regularly with ether oxygen atoms or carboxylic acid ester groups, and the quotient Z/Q, wherein Z is the number of CH2 groups present in the recurring structural element of the radical A and Q
is the number of oxygen bridges present in the recurring structural element of the radical A, must be at least 3 and wherein, furthermore, the total number of the carbon atoms present in the radical A in alternating carbon chains is at least 30.

19. Heat accumulator according to Claim 18, characterised in that the crystalline substance is an epoxide resin which is obtained by reacting polyester-dicarboxylic acids with poly-epoxide compounds having at least 3 epoxide groups, about 1 equivalent of polycarboxylic acid being present per equi-valent of epoxide compound.

20. Heat accumulator according to Claim 18, characterised in that the crystalline substance is an epoxide resin which is obtained by reacting polyester-polycarboxylic acids having at least 3 carboxyl groups with epoxide compounds having at least 2 epoxide groups, about 1 equivalent of polyester-carboxylic acid being present per equivalent of epoxide compound.

21. Heat accumulator according to Claim 18, characterised in that the crystalline substance is an epoxide resin which is obtained by reacting diepoxide compounds with polyester-dicarboxylic acids and with dicarboxylic acid anhydrides in an equivalent ratio of 1 : 0.4 to 0.9 : 0.1 to 0.6.

22. Heat accumulator according to Claim 18, characterised in that the crystalline substance is an epoxide resin which is obtained by reacting polyester-polycarboxylic acids with epoxide compounds from the group comprising triglycidyl iso-cyanurate and triglycidyl compounds which contain one or more hydantoin groups or dihydrouracil groups, with the epoxide compound of the formula III

(III)

23. Heat accumulator according to Claim 18, characterised in that the crystalline substance is a crosslinked, elastomeric epoxide resin (L), which is manufactured by reaction of epoxide compounds, containing two or more epoxide groups, a) with polyester-polycarboxylic acids A, which essentially contain segments of the formula IV

-[O-(CH2)n-O.CO-(CH2)m-CO]p- (IV) in which n and m are identical or different and denote 2 or a higher number than 2, and to which the condition n + m = 6 to 30 applies, and in which p denotes a number from 2 to 40, which, however, is sufficiently large that the segment con-tains at least 30 -CH2- groups, and b) with polyester-polycarboxylic acids B which essentially contain segments of the formula V

-[O-R1-O.CO-R2-CO]q (V) in which R1 and R2 are identical or different and denote an alkylene radical with at least 2 C atoms in the chain and in which, per O bridge, an average of at least 3.5 and at most 30 C atoms, without taking into account the C atoms of the -CO.O- radicals, are present in the chain, and wherein the radicals R1 and R2 together contain at least one alkyl group or cycloalkyl group or one aryl group as a substituent for r one H atom or one ring-forming, optionally substituted alkylene group as a substituent for two H atoms of a chain, and in which q denotes a number from 2 to 40, which, however, is sufficiently large that the segment contains at least 30 C atoms, without taking into account the C atoms of the -CO.O- radicals, in the chain, and c) if appropriate, with curing agents C, and, if appropriate, in the presence of accelerators, in a ratio such that 0.5 to 1.2 equivalents of polyester-polycarboxylic acid are present per equivalent of epoxide compound, that 5/10 to 9/10 of these 0.5 to 1.2 equivalents are attributable to the poly-ester polycarboxylic acid A and the remaining 5/10 to 1/10 to the polyester-polycarboxylic acid B, and that up to 0.6 equivalent of curing agent C is present per equivalent of epoxide compound, with the proviso that, in the cases in which only difunctional epoxide compounds and difunctional polyester-polycarboxylic acids A and B are employed, the epoxide groups must be present in excess and the reaction with a curing agent C is essential.

24. Heat accumulator according to Claim 1, characterised in that the crystalline substance is a casting resin.

25. Installation for the utilization of solar energy com-prising a heat accumulator having at least a heat exchanger, at least one useful-heat exchanger and at least one solar energy absorber; said heat exchanger, useful-heat exchanger and solar energy absorber being connected together to form a heat transfer circuit, the heat exchanger of the heat store being embedded in a crystalline substance, the heat accumulator having a maximum operating temperature greater than the melting point of the crystalline substance, and the substance being a crosslinked plastic and forming a moulding wherein the heat exchanger of the heat accumulator is integrated.

26. Installation according to Claim 25, wherein at least one solar energy absorber can be bridged.

27. Installation according to Claim 25, wherein the heat accumulator has at least two zones which have different crystallite melting points and each of which has a separate heat exchanger, each of which is located in a heat transfer circuit which, in each case, contains at least one solar energy absorber and one useful-heat exchanger, the sides of the useful-heat exchangers which do not form part of the heat transfer circuit being connected in series.

28. Installation according to Claim 25, wherein at least one useful-heat exchanger has electrical heaters for warming the heat transfer liquid circulating in the circuit.