WO2017210805A1

WO2017210805A1 - Urban heat-exchange network

Info

Publication number: WO2017210805A1
Application number: PCT/CH2017/000067
Authority: WO
Inventors: François Ignace GEINOZ
Original assignee: CUENI, Marcel
Priority date: 2016-06-06
Filing date: 2017-06-06
Publication date: 2017-12-14
Also published as: CH712526A1; CH712526B1

Abstract

The invention relates to an urban heat-exchange network (10) which includes a thermal-energy production unit (14), a plurality of user thermal-energy devices (15), and ducts (11) for carrying a heat-transfer liquid (13) between the thermal-energy production unit (14) and the user thermal-energy device (15). The user device is provided with a point (16) for bleeding heat-transfer fluid in order to extract thermal energy therefrom, and an injection point (17) for injecting said calorific fluid (13) back into the network. The duct (11) carrying the heat-transfer fluid (13) is at least indirectly in contact with a phase-change material (21, 30) and the network includes management means (14a) for maintaining the mean temperature of said heat-transfer fluid (13) at a value different from the mean temperature of the surrounding land. Each bleeding point (16) is associated with a heat pump (18) for extracting thermal energy from said heat-transfer fluid in order to supply said user device (15).

Description

URBAN THERMAL EXCHANGE NETWORK Technical Area

The present invention relates to an urban heat exchange network, comprising at least one thermal energy production unit, at least one duct for conveying a heat-transfer liquid at least partially charged with thermal energy supplied by said thermal production unit. at least one user device for the thermal energy conveyed by said heat transfer fluid, wherein said user device comprises a heat transfer fluid withdrawal point for extracting thermal energy and an injection point for reinjecting said heat transfer fluid into said duct, wherein said withdrawal point is associated with a heat pump for extracting heat energy from said heat transfer fluid to supply said user device, and wherein said at least one duct is deposited in a trench formed in the surrounding land and filled with fill materials.

Prior art

Remote heating networks, commonly referred to as district heating systems, usually comprise at least one pair of ducts, the first of which, called a "go tube", is connected between a hot source and at least one heat-energy consuming device, by way of intermediate of a draw point and the second, called "return tube" is connected between the drawpoint and the hot source to bring cooled coolant into the network. The purpose of these networks is to supply the consumer device, which is for example a house, a utility room or the like, in calories taken from the heat transfer fluid. In this embodiment, the ducts are separate and arranged parallel to each other.

These networks are intended to distribute calories for the heating of individual houses and / or collective, the source is always a hot source and the system is intended exclusively for heating. In other cases, the ducts used to convey a hot heat transfer fluid are composed of a central metal tube, for example steel, surrounded by a thick layer of insulating material to provide thermal insulation of the central tube, and a sealed peripheral conduit, which constitutes the return conduit. The thick layer of insulating material is preferably made of a synthetic material, such as for example a polyurethane foam. The annular peripheral duct may be made of a synthetic material or metal. For such an embodiment, the tube should be insulated with care to avoid excessive heat loss in the surrounding terrain.

These installations usually use as a hot source either a hot water generator or a steam generator and the heat transfer fluid is, as the case, hot water or superheated steam, brought to a high temperature. The heat loss in the conduits carrying the heat transfer fluid is in principle proportional, per unit length, to the difference between the temperature of the coolant and the environment of the conduits that convey it, so that in known installations Insulations are very efficient, and therefore very expensive, the energy losses are high and the facilities lose efficiency. In both cases, the energy balance is poor and the costs of the installations as well as the operating costs are very high.

As a result, the current district heating networks are based on the following principle:

in phase 1, a heat-transfer fluid is supplied with a sufficient quantity of energy to enable it to bring sufficient heat energy to satisfy all consumers of the network fed by said heat transfer fluid;

in phase 2, said "charged" heat transfer fluid is circulated in the "out" duct, so that the consumers can be supplied through their draw point; in order to best avoid losses, the ducts must be effectively insulated;

in phase 3, said circulating heat transfer fluid "discharged" in the conduit "return", to bring it back to the heat source to recharge it; as for phase 2, in order to best avoid losses, the ducts must be effectively isolated.

Current distribution networks are penalized both for their installation and their operation because of the costs of energy production and insulation. In addition, they are generally only usable for transporting heat and are not suitable for conveying cold. As a result, they have not become widespread and do not solve the problems related to the cost of thermal energy for the consumer. The publications below illustrate the defined prior art and present in part or in full the disadvantages described. These are the German publication DE 10 2008 041715, the German publication DE 32 24 854 A1, the German publication DE 31 02 869 A1 and the Japanese publication JP 2014 102039 A which illustrate centralized heating systems that make circulating a heat transfer fluid inside a network coupled to users.

Presentation of the invention

The present invention proposes to overcome all of the disadvantages mentioned above by developing a remote heating network that is efficient and economical because it is designed to increase the capacity of existing thermal energy sources locally by capturing the free thermal energy and available to automatically integrate it into the network, to substantially store the available thermal energy and distribute it by restoring the stored energy according to the momentary needs of consumers. These goals are achieved by the district heating network, as defined in the preamble and characterized in that:

said at least one duct conveying said heat transfer fluid is made of a thermally good conducting material;

said at least one conduit conveying said coolant is at least indirectly in contact, without intermediate thermal insulation, with said backfill materials of said trench; and

said urban network comprises management means for maintaining said coolant at a temperature Ti, such as the difference ΔΤ between the temperature Ti of said coolant and the average temperature T2 of the surrounding terrain, to a predetermined value.

According to a first advantageous solution, said difference ΔΤ is between 0 and 10 ° C and preferably between 1 and 5 ° C.

Said management means are advantageously arranged to constantly maintain the temperature T1 of said heat transfer fluid to a value greater than its freezing value. Preferably, said trench containing said backfill material may contain at least one phase change material.

Advantageously, said backfill materials comprise fractional elements which at least partially fill said trench, said fractionated elements comprising at least a first phase-change material in the form of solid particles mixed with said fractionated elements.

According to one embodiment, said fractionated elements at least partially filling said trench, are in direct contact with the walls of said at least one conduit carrying said heat transfer fluid, wherein said walls of this conduit are made of a thermally good conducting material. According to another embodiment, said at least one conduit for conveying a coolant liquid comprises a peripheral tube and an inner tube disposed inside said peripheral tube, said inner tube being arranged to convey said heat transfer fluid and defining a peripheral space formed between said peripheral tube and said inner tube, said peripheral space containing at least a second phase change material, and wherein the walls of said peripheral tube, are made of aimally good conductor material. Advantageously, said second phase change material may be different from said first phase change material.

According to another embodiment, said at least one conduit for conveying a coolant liquid comprises a first peripheral tube and an inner tube (23a) disposed inside said peripheral tube, said inner tube being arranged to convey said heat transfer fluid and defining a first peripheral annular space formed between said first peripheral tube and said inner tube, said peripheral space containing at least one second phase change material, and a second peripheral tube disposed coaxially outside said first peripheral tube, to define a second a peripheral space formed between said first peripheral tube and said second peripheral tube, said second peripheral space containing at least a third phase change material, wherein the walls of said first peripheral tube, and the walls of said first peripheral tube, are made of a material thermally good driver.

Said management means advantageously comprise temperature sensors and valves for controlling the volume and / or the rate of circulation of the coolant to regulate the value of its temperature Ti and the difference ΔΤ between the temperature Ti of said coolant and the temperature T ₂ average of the surrounding terrain according to the consumption of said at least one user. According to a particular embodiment, said second phase change material and said third phase change material are in the liquid state at the temperature Ti of the heat transfer liquid. Preferably, said second phase change material and said third phase change material are formic acid.

Said first phase change material may be a solid particle compound at the use temperature and inert with respect to mineral fill materials of said trench.

Said second phase change material may be incorporated into longitudinal segments consisting of pairs of nested half-shells, mounted at the periphery of said at least one conduit.

Each half-shell of each pair of interlocked half-shells may comprise a semi-cylindrical casing and a filling mass which is at least partially constituted of one of said phase-change materials.

Brief description of the drawings

The present invention and its main advantages will appear better in the description of a preferred embodiment, with reference to the appended drawings in which: FIG. 1 is a schematic view of a heat exchange network according to the invention, FIG. 2 is a schematic cross-sectional view of a first embodiment of a pipe section of said heat exchange network disposed in a trench, FIG. 3 is a diagrammatic cross-sectional view of a second embodiment of a pipe section of said heat exchange network disposed in a trench, FIG. 4 is a partial longitudinal sectional view of the pipe section represented by FIG. Figure 4, and

Figures 5A and 5B illustrate, respectively in longitudinal section and in cross section a particular embodiment, in which a phase change material is incorporated in two interlocking half-shells. better way (s) to achieve the invention

With reference to the figures, and in particular to FIG. 1, the heat exchange network 10 comprises at least one, and preferably a plurality of ducts 11, which preferably form a plurality of main loops 12 of ducts 11 conveying a coolant 13 to transport it between a source or a generator 14 of thermal energy and user devices 15 also called consumers. Each of said main loops 12 comprises at least one drawpoint 16 and an injection point 17 which correspond to one or more user devices 15. These user devices 15 can also be individual or collective. In the case of a collective user device, the distribution of the thermal energy taken is distributed inside a building, for example a rental building, according to specific criteria of occupancy of the building. The withdrawal points 16 are arranged to take heat transfer fluid 13 and to distribute it to the corresponding user devices 15 and the injection points 17 are arranged to bring the heat transfer fluid 13 out of the user devices 15 to reinject it into the network. At the outlet of each withdrawal point 16 is disposed a heat pump 18 for taking thermal energy from said heat transfer fluid 13 in order to deliver it to the user device 15 concerned. The network is designed according to local needs and the main loops can be connected in series or in parallel depending on the location of users 15 and the geography of the area in which they are placed. The connection connections are simple, since only the circulation of heat transfer fluid is important, and that the insulation of the ducts 11 is completely secondary, as will be described later, while the concern for optimal insulation constitutes the essential concern of all the operators of the urban networks of the prior art. FIG. 2 represents a cross-sectional view of a trench 20 in which a duct 11 has been put in place which conveys the coolant 13. It will be noted that the ducts 1 which constitute the main loops 12 as well as the ducts which convey the heat transfer fluid 13 to the draw-off points 16 supplying the users 15 and from the injection points in the network from the users 15, are uninsulated conduits, made of a thermally good conducting material, in particular steel, to be able to exchange thermal energy with the surrounding environment. The first embodiment shown in FIG. 2 illustrates the ducts 11 which convey the coolant 13, deposited in a trench 20, containing backfill material 22. In order to increase the thermal energy storage capacity in the materials of FIG. embankment and because of the exchange made possible by virtue of the characteristics of good thermal conduction of the walls of the conduits which convey the coolant 13, a phase-change material 21 is contained in the form of divided particles mixed in bulk with backfill materials 22 The duct 11 which is placed at the bottom of the trench 20 consists of a single single-walled tube 23 made of a thermally good conducting material, such as for example steel. By conveying the heat transfer fluid 13, it exchanges thermal energy with the surrounding materials and in particular the materials contained in the trench 20, including the solid particles of phase change material. In the context of this invention, a desired objective is for example to charge the heat transfer fluid 13 into "hot" thermal energy, that is to say in calories, that it is advantageous to capture in part when they are released by the surrounding ground, through the wall 24 of the tube 23 in favor of the coolant, the average temperature of the heat transfer fluid must be lower than the average temperature of the ground, so that the heat exchange can be made from the ground to 24. On the other hand, when, in the context of this invention, the objective sought is to charge the heat transfer fluid 13 with "cold" heat energy, that is to say in negative frigories or calorie, which should partly be released by the surrounding ground through the wall 24 of the tube 23 in favor of the heat transfer fluid, the average temperature of the coolant must be higher than the average temperature the ground so that the heat exchange can take place from inside the tube 24 to the surrounding ground.

The backfill materials contained in the trench 20, for example stones in the upper zone or an embankment mass comprising for example gravel and sand 22, mixed with particles of phase-change materials 21, for example example in the form of solid particles, in the lower part of the trench 20, communicate their thermal state to the coolant 13 flowing in the tube 23. This system can convey both hot thermal energy and energy cold thermal and especially to capture thermal energy naturally available in the surrounding terrain for use by various user devices arranged along the branches of the network.

Another embodiment of the duct 11 is illustrated in FIG. 3, which shows a cross-sectional view of a trench 20 in which a duct 11 has been put in place which conveys the coolant 13. second embodiment, wherein the conduit 11 is composed of a first inner tube 23a having a peripheral wall 24a and a second outer tube 23b having a peripheral wall 24b, which surrounds the inner tube 23a. The inner tube 23a conveys a coolant 13 and the outer tube 23b, disposed coaxially around the inner tube 23a, conveys a phase change material 30. As previously, the conduit 11 is placed at the bottom of the trench 20 and the peripheral walls 24a and 24b, respectively of the inner tube 23a and the outer tube 23b are preferably made of a thermally good material conductor. The heat transfer fluid 13 which circulates in the inner tube 23a exchanges thermal energy with the phase-change material 21 which circulates in the outer tube 23b which itself can exchange thermal energy with the surrounding materials and in particular the materials contained in trench 20 and the surrounding terrain. The trench 20 contains backfill material, for example stones or rubble 26, in the upper zone or a mass of embankment comprising for example gravel and sand 22, in the lower part surrounding the outer tube 23b.

One could envisage a mixed variant encompassing both the embodiment of FIG. 2 and that of FIG. 3. In this case, the trench contains at least a first phase-change material 21 in the form of solid particles. at the temperature of use and the outer tube 23b contains a second phase-change material 21a, in the liquid state, at least during the capture of the thermal energy.

In these three embodiments, the phase change materials are intended to store thermal energy momentarily to be able to restore it to the coolant 13, at a time when the heat energy requirement of the user devices is detected .

A fourth embodiment is illustrated in Figure 4, as well as the operation of the device of the installation. The heat transfer fluid of the tube 23a provides, as shown by the arrow Ai, thermal energy to a heat pump 18 and returns heat transfer fluid, as previously, in the conduit 23a, as shown by the arrow A2. The inner conduit 23a is surrounded by a first coaxial conduit 24a with a peripheral wall 24b which is itself surrounded by a second coaxial conduit 25a with a peripheral wall 25b. These coaxial conduits define two spaces respectively filled with phase change materials which are advantageously in liquid form, such as formic acid at room temperature.

The exchange of thermal energy is illustrated by the double arrow A3 which illustrates the heat exchange between the coolant and the phase change material 21 a. The double arrow A4 illustrates the exchanges of heat energy and the surrounding ground that may contain said first phase-change material 21. The arrow As illustrates possible exchanges between the phase change materials 21a and 21b.

The network is provided with means for detecting the thermal energy requirements, these means being in particular based on temperature measurements of the coolant. Depending on whether the objective is to provide heat or cold, a drop in temperature or an increase in temperature identify the need for calories or frigories, these needs then being met by at least one thermal energy generator of the network, which is complementary to the various "contributors" of thermal energy distributed on the network.

With reference to FIGS. 5A and 5B, said second phase-change material 21a is incorporated in longitudinal segments 40 made up of pairs of half-shells 41 and 42 nested, mounted on the periphery of the duct 11. Each half-shell 41 and 42 comprises a semi-cylindrical casing 41a and 42a, preferably made of a thermally good conductive material and a filling mass 41b and 42b which is at least partially made of one or more phase-change materials. This mass filling can provide a partial or total filling, its purpose being both to capture thermal energy, to store it when it can not be used immediately and to restore it when the network Se asks, solicited by the or users via temperature sensors, for example.

Direct contact with the ground is ensured, possibly through trench fill materials, so that heat exchange can be effected effectively with virtually no loss. The objectives of the invention are fulfilled simply and economically.

Various variants could be devised by those skilled in the art, as regards the construction and layout of the conduits that constitute the network, but they remain included in the features defined by the claims.

Claims

1. Urban heat exchange network (10), comprising at least one unit (14) for producing thermal energy, at least one conduit (11) for conveying a heat transfer liquid (13) at least partially charged with heat thermal energy supplied by said thermal production unit (14), at least one user device (15) of the thermal energy conveyed by said heat transfer liquid (13), in which said user device comprises a fluid withdrawal point (16) heat transfer medium to extract thermal energy and an injection point (17) to reinject said heat fluid (13) into said conduit (11).

in which said withdrawal point (16) is associated with a heat pump (18) for extracting thermal energy from said heat transfer fluid to power said user device (15), and

in which said at least one conduit (11) is deposited in a trench (20) made in the surrounding ground and filled with backfill materials, characterized in that:

said at least one conduit (11) conveying said heat transfer fluid (13) is made of a thermally good conductor material;

- said at least one conduit (11) conveying said heat transfer fluid (13) is at least indirectly in contact, without intermediate thermal insulation, with said backfill materials of said trench (20); And

said urban network (10) comprises management means (14a) for maintaining said heat transfer fluid (13) at a temperature Τ, such as the difference ΔΤ between the temperature ΤΊ of said heat transfer fluid (13) and the average temperature T2 of the surrounding terrain , to a predetermined value.

2. Urban network (10) according to claim 1, characterized in that said difference ΔΤ is between 0 and 10°C and preferably between 1 and 5°C.

3. Urban network (10) according to claim 1, characterized in that said management means (14a) are arranged to constantly maintain the temperature Ti of said heat transfer fluid (13) at a value greater than its freezing value.

4. Urban network (10) according to claim 1, characterized in that said trench containing said backfill materials contains at least one phase change material.

5. Urban heat exchange network according to claim 5, wherein said backfill materials comprise split elements which at least partially fill said trench, said split elements comprising at least a first phase change material (21) in the form of solid particles mixed with said fractionated elements.

6. Urban heat exchange network, according to claim 5, in which said split elements at least partially filling said trench, are in direct contact with the walls (23) of said at least one conduit (11) conveying said heat transfer fluid (13). ), in which said walls of this conduit are made of a thermally good conductor material.

7. Urban heat exchange network, according to claim 4, in which said at least one conduit (1 1) for conveying a heat transfer liquid (13) comprises a peripheral tube (24a) and an inner tube (23a), arranged at the interior of said peripheral tube (24a), said inner tube (23a) being arranged to convey said heat transfer fluid (3) and defining a peripheral space provided between said peripheral tube (24a) and said inner tube (23a), said peripheral space containing at least a second phase change material (21a), and in which the walls (24b) of said peripheral tube (24a) are made of a thermally good conductor material.

8. Urban heat exchange network according to claim 7, wherein said second phase change material (21 a) is different from said first phase change material (21).

9. Urban heat exchange network, according to claim 4, in which said at least one conduit (11) for conveying a heat transfer liquid (13) comprises a first peripheral tube (24a) and an inner tube (23a), arranged at the interior of said peripheral tube (24a), said inner tube (23a) being arranged to convey said heat transfer fluid (13) and defining a first peripheral annular space provided between said first peripheral tube (24a) and said inner tube (23a), said peripheral space containing at least a second phase change material (21a), and a second peripheral tube (25a), arranged coaxially outside said first peripheral tube (24a), to define a second peripheral space provided between said first peripheral tube (24a) and said second peripheral tube (25a), said second peripheral space containing at least a third phase change material (21b), in which the walls (24b) of said first peripheral tube (24a), and the walls (25b) of said first peripheral tube (25a), are made of a thermally good conductive material.

10. Urban heat exchange network, according to claim 1, in which said management means (14a) comprise temperature sensors and valves for controlling the volume and/or the speed of circulation of the heat transfer fluid to regulate the value of its temperature Ti and said difference ΔΤ between the temperature Ti of said heat transfer fluid (13) and the average temperature T2 of the surrounding terrain as a function of the consumption of said at least one user.

11. Urban heat exchange network, according to any one of claims 4 to 10, wherein said second phase change material (21a) and said third phase change material (21b) are in the liquid state at the temperature Ti of the heat transfer liquid (13).

12. Urban heat exchange network, according to any one of claims 4 to 10, in which, said second phase change material (21a) and said third phase change material (21b) are formic acid.

13. Urban heat exchange network, according to any one of the preceding claims, in which, said first phase change material (21) is a compound of solid particles at the temperature of use and inert with respect to materials backfill minerals from said trench.

14. Urban heat exchange network, according to any one of the preceding claims, in which said second phase change material (21a) is incorporated in longitudinal segments (40) consisting of pairs of nested half-shells, mounted at the periphery of said at least one conduit (1).

15. Urban heat exchange network, according to claim 14, in which each half-shell of each of the pairs of nested half-shells (41a, 41b; 42a, 42b) comprises a semi-cylindrical envelope (41a, 42a) and a filling mass (41b, 42b) which is at least partially made up of one of said phase change materials (21, 21a, 21b).