US20110277956A1

US20110277956A1 - Method for transporting heat, transport system for a heat carrier and the use thereof

Info

Publication number: US20110277956A1
Application number: US13/120,286
Authority: US
Inventors: Michael Hermann; Stefan Gschwander
Original assignee: Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Priority date: 2008-09-24
Filing date: 2009-09-23
Publication date: 2011-11-17
Also published as: DE102008048655B4; DE102008048655A1; EP2338021B1; EP2338021A2; WO2010034482A3; WO2010034482A2

Abstract

The invention relates to a transport system for a heat carrier which has at least one transport network, at least one heat carrier and also at least one drive device for the heat carrier. The invention likewise relates to a method for transporting heat using this transport system. The transport system according to the invention is used for example for transporting heat in solar plants.

Description

The invention relates to a transport system for a heat carrier which has at least one transport network, at least one heat carrier and also at least one drive device for the heat carrier. The invention likewise relates to a method for transporting heat using this transport system. The transport system according to the invention is used for example for transporting heat in solar plants.
Pipeline systems based on liquids or gases are the state of the art in the field of heat transport. A heat carrier fluid is hereby transported continuously from one or more heat sources to one or more heat sinks with the help of pipelines. The heat storage medium hereby fills the entire pipeline network and is circulated generally by pumps. In the case of networks which distribute heat, the network often consists of a heat source which delivers heat at a specific set temperature level and of distributed heat sinks which dissipate the heat of the transport and storage medium and as a result lower its temperature to a lower level. In the case of networks which serve for cooling, heat is transported generally in a circulation from one or more heat sources to a central heat sink. Mobile heat transport applications are new in development: standard containers as are used nowadays in international trade are used, filled with a heat storage material and supplied with industrial waste heat. Lorries transport these containers then to the heat sink or to a consumer. It has also been proposed as an extension to this approach to transport these containers by trains between heat source and heat sink. This system, whether now transport by lorry or by train, is based on the existing transportation infrastructure and operates according to the principles of goods transportation. Heat can be transported economically by this system only in correspondingly large quantities. Automation of the transport between heat source and sink has to date not been achieved in the state of the art.
Starting herefrom, it was the object of the present invention to provide a transport system for heat carriers which also enables economical transport of heat in small quantities.
This object is achieved by the transport system having the features of claim 1 and the method for transporting heat having the features of claim 13. The further dependent claims reveal advantageous developments. Uses according to the invention are mentioned in claim 16.
According to the invention, an automated transport system for a heat carrier is provided, which has at least one transport network, at least one heat carrier and also at least one drive device for the heat carrier. By means of heat absorption at a heat source and/or heat discharge at a heat sink, which are situated at defined points of the transport network, the heat carrier can thereby change its thermodynamic state and/or its physical and/or chemical properties. The at least one heat carrier is thereby encapsulated in at least one container.
The invention thereby provides automation both during loading and unloading and during the actual transport of the containers within the transport network. There are included here for example “finding the correct route” from a starting point to an end point in the network.
Fundamental to the invention described here is that the function of the heat storage of a material is decoupled from the transport function, i.e. that, in contrast to for example hot water networks, the transport function and the heat storage function can be produced independently of each other. Whilst, in standard cooling or heating networks, the heat carrier not only stores the heat which is intended to be transported but also it is pumped through the pipes of a network, i.e. also takes over the transport of the heat directly by its flow, the heat storage material in the case of the invention described here only has the function of pure heat storage. Thus for example the viscosity of the material does not play any role since it is not pumped directly but is transported packed in a container. The separation of transport function and heat storage function makes it possible to transport any materials—completely independently of their aggregate state. Hence it becomes possible to transport, in one and the same network, different heat storage materials at the same time independently of their respective temperature level. The transport between heat source and heat sink is taken over by a transport system which is independent of the heat storage material. This is achieved by the already mentioned encapsulation of the heat storage material in containers which are conveyed by a transport system in an automated fashion between heat sources and heat sinks.
As a result of packing the heat storage materials in containers which then serve for the transport, it becomes possible to use different materials for heat or cold storage in one heating or cooling network. In addition, each container can transport heat at a temperature level which is independent of the temperature level and/or of the heat storage materials of other containers. In contrast to the above-mentioned mobile heat transport by means of lorries or rail, the system described here requires an infrastructure which, in addition to the transport network, also comprises heat transfer stations at each heat source or sink, in which the heat is supplied automatically to the container or removed therefrom as soon as it is intended to be sent or stored in accordance with availability or need or as soon as it arrives loaded. Furthermore, the invention differs, relative to the state of the art, by its ability to be scaled. Thus, for example overland networks are likewise conceivable, such as short-range heating and cooling networks in a residential area or even the distribution of the heat within a building. The exchange of heat takes place completely automatically and the system can be scaled from the millilitre to the tonne scale.
Since the temperature level in each container can be adjusted individually by choice of heat storage material, heat can be transported in one and the same transport system within a very wide temperature range, for example containers for low temperatures and containers for high temperatures being transported at the same time within one network.
With respect to the drive device for the encapsulated heat carrier, various variants can be selected. A first variant provides that the transport system is conceived as a standard pneumatic tube system, i.e. in which the transport network is constructed as a pipe system and transport of the containers is effected in the pipes on the basis of air pressure differences in the pipe. In this case, a compressed air and/or vacuum device is used as drive device.
A second variant according to the invention provides that the transport system is based on the principle of magnetic levitation technology, for which purpose then corresponding electromagnetic drive devices are required.
A third variant according to the invention provides that the transport system is conceived corresponding to a rail vehicle, i.e. a mechanical system in which the containers are guided via rails and are driven forward for example by an electrical drive device.
A fourth variant according to the invention provides that the transport system is based on an air cushion principle, i.e. that the containers slide on an air cushion for example through a pipe.
Likewise, it is also possible that the four above-described variants are combined with each other.
A preferred variant provides that the containers are essentially cylindrical or spherical so that their transport can be effected according to the principle of a pneumatic tube and/or by rollers.
All materials which are currently used for this purpose can be considered as heat carriers. There are included herein for example phase-change materials (PCM), which melt for example by means of heat absorption at the location of the heat source and discharge the latently stored heat again upon solidification at the location of the heat sink. Likewise, it is possible that phase-change liquids, e.g. in the form of emulsions or suspensions made of a carrier fluid and a phase-change material, are filled into the containers. For the purpose of heat exchange, the phase-change liquid is then removed from the container in an external heat exchanger.
There can also be used as heat carriers, sorbents, e.g. zeolites, silica gels, activated carbon, metal oxide compounds (metal oxide framework MOF), aluminophosphates (AlPO), silicoaluminophosphates (SAPO), layer silicates and mixtures thereof. In this case, the heat carrier then discharges fluid contained therein by desorption by means of heat absorption at the location of the heat source. At the location of the heat sink, the heat supplied during the desorption is then discharged again by absorption of fluid (adsorption). Thus it is possible for example that the fluid discharged during the desorption in the vapour phase is conducted via a semipermeable membrane which is permeable for vapour but impermeable for liquid fluid into a separate region of the container where it can condense and be removed again automatically by adsorption for the purpose of heat discharge.
A further variant according to the invention provides that the heat which is coupled into the material situated in the container serves for the purpose of setting physical processes or chemical reactions in motion, which change the material or the materials situated in the container is a desired manner. In the case of the heat transport task, each individual container can contain a material adapted to the respective heat transport task. This system makes it possible to transport for example heat from a heat source A which is present at a very high temperature level (e.g. 150° C.) to a heat sink B which can use the heat up to a temperature level of e.g. 100° C. At the same time, heat from a heat source C which is present for example at 80° C. can be delivered to a heat sink D which also needs the heat only at this lower temperature level. In addition, it is possible that the heat sink B, if it has run down the heat container from the heat source A to 100° C., can send the latter further to the heat sink D and thus the heat which is present is used in a substantially more efficient manner. The principle of addressing heat in a network according to the respective temperature level, increases the exergetic efficiency and contributes to a drastic reduction in CO₂emissions.
A further variant provides that the heat carrier is a substance which, as a result of temperature and reversibly, is endothermally and/or exothermally reactive.
It is hereby preferred that the containers are filled with one or more substances which react reversibly to form one or more substances by means of an endothermal chemical reaction, which substances can be specifically returned to the exothermal reverse reaction for the purposes of heat discharge.
The substances produced by the endothermal reaction are preferably separated from each other automatically in the container and are guided back together specifically in order to induce the exothermal reaction. Preferably, the exothermal reaction is induced by achieving a specific temperature.
It is further preferred that the at least one container has a heat-conducting inner structure which enables heat conduction between heat carrier and heat source or heat sink. This inner structure can connect the region of the heat coupling and heat decoupling to the at least one heat carrier situated therein.
A further preferred variant provides that the at least one container has an inner channel structure through which the heat carrier can flow. A further preferred variant provides that the heat transport is effected by means of at least one heat pipe.
The containers can likewise have devices for reducing thermal losses. There are included herein for example a double-walled configuration of the container wall according to the Dewar principle.
A further preferred embodiment provides that the transport system comprises a thermally insulated magazine as heat store for storage or intermediate storage of the encapsulated heat carriers. It is thereby also possible that a magazine which is thermally insulated in this manner is configured such that it can be used itself as container in the transport system according to the invention. A further possibility resides in the magazine having a plurality of cells which can rotate like a revolver about the cylinder axis so that distribution of the capsules from individual cells into the transport network can be effected for example in the form of pipes.
A further preferred variant provides that the thermally insulated magazine is designed such that containers can be filled at the top and removed at the bottom and an automatic advance of the containers situated in the magazine is effected solely by gravity, e.g. rollers on inclined tracks.
The containers can be disposed preferably in a planar manner adjacently or one above the other for the purpose of heat adsorption or discharge. In this way, constructions for solar collectors, e.g. roof installation, façade installation or as window collector, can be produced just like heating or cooling ceilings, cooling walls and cooling floors.
A further variant according to the invention provides that the transport network is constructed from pipes, the pipes being optically transparent for solar radiation in the region of the heat source and being positioned in the focal line of a radiation-concentrating system, the containers having, at least in regions, a material which absorbs solar radiation or a coating which absorbs solar radiation, in particular a spectrum-selective coating. For example, the containers can have a double-walled design according to the principle of a Dewar vessel, at least the outer wall consisting of a material which is transparent for solar radiation, preferably made of glass, whilst the inner wall is provided with an absorber coating and the region between the walls is evacuated for the purpose of reducing thermal loss or is filled with a noble gas.
According to the invention, a method is likewise provided for transporting heat using the above-described transport system, in which the at least one heat carrier is encapsulated in at least one container, the containers are transported through the network with the help of the drive device, heat absorption or heat discharge being effected at defined points of the network, as a result of which the at least one heat carrier changes its thermodynamic state and/or its physical and/or chemical properties.
With respect to the heat absorption or heat discharge, various variants according to the invention exist. According to a first variant, the heat is coupled into or decoupled by means of radiation without contact between heat source or heat sink and container wall. A second variant provides that the heat is effected via conduction by contact between heat source or heat sink and container wall. In the case of a third variant, the coupling is effected via convection by means of a liquid or gaseous fluid between heat source or heat sink and container wall.
The transport system according to the invention is used in heating and cooling networks or also for the transport of heat in a solar plant, both in the case of purely thermal use and in the case of current production in a solar-thermal power station.
Since, with the heat transport system described here, any heat source can feed heat independently of the others and each consumer can draw heat from any heat provider, such a network offers the ideal trading centre for heat. In one and the same network, solar heat can be sold just as waste heat from industrial processes. Prices are then produced, such as in the stock market, by supply and demand. Thus, the owner of a solar-thermal small unit at his private home can supply his excess heat into the network in the summer. Hence, industrial processes or for example also the local swimming baths can be heated. In the case of very many participants in such a heat transport network, also special distribution apparatus must be used. There are possible here for example all possibilities already known from pneumatic tube systems. In addition, also new approaches are however conceivable, which produce connection of different partial regions of such a network—e.g. connection of a main network with various sub-networks. Such apparatus could for example be designed as a drum or revolver which receives one or more containers from a pipe of such a network and distributes them to other pipes by rotation.
Since the distribution of heat in the system described here is based on packing a material in a container, the application of the described heat network is not only restricted to the distribution of heat. The mentioned containers need not necessarily comprise a heat carrier material, they can also comprise any other product. Thus, the heat network can also be used in a standard manner as pneumatic tube and serve for dispatching goods. The network makes it possible that each participant can directly exchange goods with any other participant. As a result of this multiple use in combination with the flexibility with respect to the temperature level, the economics of the system relative to standard short-range or long-range heating networks according to the state of the art is significantly increased.
The subject according to the invention is intended to be explained in more detail with reference to the subsequent Figures without restricting said subject to the special embodiments shown here. Hence also any combinations between the embodiments shown in the Figures are included in the present invention.

FIG. 1 shows, with reference to a schematic drawing, a first variant of a heat transport system according to the invention which is based on the pneumatic tube principle.

FIG. 2 shows a first variant of a container according to the invention in which a heat carrier is encapsulated.

FIG. 3 shows a container according to the invention according to FIG. 2 during the heat coupling by means of solar radiation.

FIG. 4 shows a variant of a heat transport system according to the invention in a solar-thermal power station.

FIG. 5 shows a magazine according to the invention for intermediate storage of the containers encapsulating the heat carrier.

FIG. 6 shows a cylindrical magazine according to the invention in which the containers are mounted rotating (according to the revolver principle).

In FIG. 1 a first variant of an automated heat transport system is represented, which is constructed according to the standard pneumatic tube system. Containers 2 in which the heat carrier is encapsulated are thereby transported through the transmission pipes 1 on the basis of air pressure differences. The air pressure differences can be built up via compressors 3. The pipes 1 can have switch points 4 at defined positions, as a result of which branches can be incorporated in the transport network. The transport of the containers 2 encapsulating the heat carrier is effected up to a transfer station 5. This transfer station comprises a heat exchanger 6 and also a heat carrier pipeline 7 by means of which transport of the heat to the end consumer is effected.
In FIG. 2, a container 8 in which a heat carrier is encapsulated is represented. The container 8 thereby has a construction according to the DEWAR principle, i.e. of concern is an evacuated double-walled container, preferably made of glass. A buffer 9 is disposed at the closed end of the container 8, whilst, at the open end, a further buffer 10 which has the function of a cover is disposed. A heat storage material 11, e.g. PCM, is introduced in the container 8. Furthermore, the container has heat exchangers 12 which are constructed helically in the present variant. These serve for coupling and for discharge of heat into or out of the container.
FIG. 3 shows the above-described container 8 in a variant for the heat coupling. In addition to the components described in FIG. 2, the container has a spectrum-selective coating 13 which is disposed on the inside of the double-walled container 8. Heating of the heat storage material 11 in the container 8 can hence be effected by incident solar radiation 14.
In FIG. 4, use of a heat transport system according to the invention, given by way of example, in a solar-thermal power station is represented. The Figure shows a reflector 15 in the form of a parabolic mirror and also a transparent transmission pipe 16, e.g. made of glass, which is disposed in the focal line of the parabolic mirror 15. The containers 17 are transported through the focal line and hereby absorb the concentrated solar radiation 18. The heat storage material situated in the containers is thereby heated.
In FIG. 5, a variant for the intermediate storage of the containers containing the heat carrier is represented. The magazine 19 represented here contains a large number of cells 20 for receiving the containers 21. Each individual cell 20 has in addition also heat insulation 22 on the inside thereof.
In FIG. 6, a further development of the magazine according to FIG. 5 is represented. The cells 20 for receiving the containers are hereby disposed in a revolver-like manner about an axis of rotation 23. At the same time, the system has two transmission pipes 24 and 24′, the cells being positioned by rotation such that the transport of the containers 25 into the respective transmission pipe can be effected. Both the axis of rotation 23 and the cells 20 are disposed in a cylindrical magazine 26 which can be transported in turn in a transmission pipe 27. Since the magazine represented here is based on the revolver principle, a plurality of containers can be received from one pipe of the transport network and be distributed by rotation to other pipes.

Claims

1. An automated transport system for a heat carrier comprising:

at least one transport network,

at least one heat carrier which, by means of heat absorption at a heat source and/or heat discharge at a heat sink at defined points in the network, changes its thermodynamic state and/or its physical and/or chemical properties, and

at least one drive device for the heat carrier, wherein the at least one heat carrier is present encapsulated in at least one container.

2. The transport system according to claim 1, wherein the drive device is selected from the group consisting of compressed air or vacuum devices, magnetic and electrical drive devices and combinations thereof.

3. The transport system according to claim 1, wherein the at least one container is cylindrical or spherical.

4. The transport system according to claim 1, wherein the at least one heat carrier is selected from the group consisting of water, phase-change materials and also emulsions or suspensions thereof, sorbents, in particular zeolites, silica gels, activated carbon, metal oxide compounds, aluminophosphates, silicoaluminophosphates, layer silicates and mixtures thereof.

5. The transport system according to claim 1, wherein the heat carrier is a substance which, as a result of temperature and reversibly, is endothermally and/or exothermally reactive.

6. The transport system according to claim 1, wherein the at least one container has a heat-conducting inner structure which enables heat conduction between heat carrier and heat source or heat sink.

7. The transport system according to claim 1, wherein the at least one container has an inner channel structure through which the heat carrier can flow.

8. The transport system according to claim 1, wherein the at least one container has at least one heat pipe for coupling or discharge of heat.

9. The transport system according to claim 1, wherein the at least one container has devices for reducing thermal losses, including a double-walled configuration of the container wall according to the Dewar principle.

10. The transport system according to claim 1, wherein the transport system has a thermally insulated magazine as heat store for storage of the encapsulated heat carriers.

11. The transport system according to claim 1, wherein transport network is constructed from pipes.

12. The transport system according to claim 11, wherein the pipes are optically transparent for solar radiation in the region of the heat source and are positioned in the focal line of a radiation-concentrating system, the containers having, at least in regions, a material which absorbs solar radiation or a coating which absorbs solar radiation.

13. A method for transporting heat comprising:

providing at least one transport network, and at least one heat carrier which, by means of heat absorption at a heat source and/or heat discharge at a heat sink at defined points in the network, changes its thermodynamic state and/or its physical and/or chemical properties, and at least one drive device for the heat carrier, wherein the at least one heat carrier is present encapsulated in at least one container; and

transporting the at least one container through the network with the help of the drive device, heat absorption or heat discharge being effected at defined points of the network, as a result of which the at least one heat carrier changes its thermodynamic state and/or its physical and/or chemical properties.

14. The method according to claim 13, wherein the transport is effected by means of pressure differences in the transport system, magnetically levitating, via rails and/or by means of air cushions.

15. The method according to claim 13, wherein the heat absorption or heat discharge between heat source or heat sink and heat carrier is effected without contact via radiation, by means of conduction or convection.

16. A method comprising:

transporting heat via the at least one transport network in heating and cooling networks, in solar plants and in solar-thermal power stations.