DK201670093A1

DK201670093A1 - Faseændringsmateriale-baseret varmesystem

Info

Publication number: DK201670093A1
Application number: DKPA201670093A
Authority: DK
Inventors: Knud Vandsø Madsen; Morten Veis Donnerup
Original assignee: Suntherm Aps
Priority date: 2016-02-23
Filing date: 2016-02-23
Publication date: 2017-04-10
Also published as: DK178864B1; WO2017144059A1

Abstract

A heating system is disclosed with a heat storage comprising a Phase Change Material (PCM) in direct physical contact with a heat-transferring medium, wherein the heat-transferring medium is arranged to be brought in to contact with the PCM through a diffuser unit (17) arranged beneath the PCM. Furthermore, a diffuser unit (17) for such a heating system is disclosed.

Description

PCM-based heating system

The present invention relates to a complete integrated heating system for heating of residential buildings and domestic hot water therefore.

Background of the invention

During the last decades, the focus on developing energy-efficient systems for heating and cooling of buildings has been constantly increasing and new heat energy sources, such as solar heating and geothermal heating, have been introduced. Even though these new sources have gradually reached a certain level of "maturity", however, typical heating systems known in the art still exhibit certain difficulties when it comes to integrating the different heat energy sources in common system in a truly energy-efficient and intelligent way. US 4219072 A discloses a heat exchanger with a heat storage comprising a Phase Change Material (PCM), in which a heat-transferring medium is arranged to be brought in contact with the PCM through a diffuser.

Brief description of the invention

It is an object of the present invention to provide an integrated heating system, which overcomes the above-mentioned disadvantage of solutions known in the art.

The present invention relates to a heating system with a heat storage comprising a Phase Change Material (PCM) in direct physical contact with a heat-transferring medium, wherein the heat-transferring medium is arranged to be brought into contact with the PCM through a diffuser unit arranged beneath the PCM, and wherein the diffuser unit is provided with a bypass circuit through which a heat-transferring medium can pass for melting solidified PCM around the diffuser unit, for instance after longer periods, during which the heating system has been out of operation.

Thus, the present invention differs from the known solutions within the art as described in US 4219072 A, inter alia, in that the diffuser unit is provided with a bypass circuit through which a heat-transferring medium can pass for melting solidified PCM around the diffuser unit.

The use of "Direct Heat Transfer" through the direct physical contact between the PCM and the heat-transferring medium ensures an efficient use of the heat storage.

The use of a bypass circuit ensures that the heating system can be started up, even in situations where the PCM has solidified in large, massive crystal formations, which are hard or even impossible for the heat-transferring medium to penetrate.

In an embodiment of the invention, the diffuser unit comprises a perforated plate through the perforations of which the heat-transferring medium is arranged to penetrate the PCM from the bottom and upwards.

The use of such a diffuser unit ensures an equally distributed and effective penetration of the PCM by the heat-transferring medium.

In an embodiment of the invention, the perforated plate is a metal plate with at least 1000, preferably at least 5000, perforations, with diameters in the range from 1 mm to 5 mm, preferably around 2 mm.

The use of this number and dimensions of the perforations ensures and efficient penetration of the PCM by the heat-transferring medium and prevents small flakes of solidified PCM from ending up under the perforated plate.

In an embodiment of the invention, the PCM is sodium acetate trihydrate or another salt with similar latent heat properties.

Sodium acetate trihydrate has proven to have latent heat properties very well suited for this purpose.

In an embodiment of the invention, the heat-transferring medium is a mineral oil.

Mineral oil has proven to have excellent heat-transferring properties and does not dissolve sodium acetate trihydrate, which is soluble in water.

In an embodiment of the invention, the heating system further comprises a controller, which is connected, for instance wirelessly via the internet, to a central server, which central server is arranged to monitor and control one or more such heating systems in such a way that the heat production of each of the one or more such heating systems is optimised with respect to economic operation of the heating system.

In an embodiment of the invention, when planning the heat production of a given heating system, the central server is arranged to take into consideration one or more of the following parameters: vital operational data from the given heating system reported to the central server from the controller of that heating system information from electricity networks about actual loads and electricity prices meteorological information such as local weather forecasts for the location of the given heating system registered consumption patterns of the given heating system.

The use of such a controller connected to a central server makes it possible to obtain an optimised heat production and operation of the heating system.

In an aspect of the invention, it relates to a diffuser unit for a heating system as described above, which diffuser unit comprises a perforated plate through the perforations of which the heat-transferring medium is arranged to penetrate a Phase Change Material (PCM) from the bottom and upwards, and wherein the diffuser unit is provided with a bypass circuit through which a heat-transferring medium can pass for melting solidified PCM around the diffuser unit.

The drawings

In the following, a few exemplary embodiments of the invention are described in further detail with reference to the drawings, of which

Fig. 1 is a perspective front view of a heating system according to an embodiment of the invention,

Fig. 2 is a perspective side view of the same heating system with removed side covers,

Fig. 3 is a perspective side view of a diffuser unit of a heating system according to an embodiment of the invention,

Fig. 4 is a perspective bottom view of the diffuser unit of Fig. 3, and

Fig. 5 is a schematic diagram of the piping and different elements of a heating system according to an embodiment of the invention.

Detailed description of the invention

Fig. 1 is a perspective front view of a heating system according to an embodiment of the invention. Basically, the heating system consists of an upper section 1 and a lower section 6 with an open connection there between, the upper section 1 being arranged on top of the lower section 6.

The upper section 1 comprises the necessary components to control the heating system. In the illustrated embodiment of the invention, for instance, at least one or more energy meters 2 and flow meters 3, a oil-circulating pump 4 and one or more motor valves 5 are arranged on the forward-facing outside of the upper section 1 of the system.

Furthermore, Fig. 1 illustrates some of the external connections to and from the heating system, namely an inlet for domestic cold water 7, a central heating return 8, a refrigerant inlet 9 and a refrigerant outlet 10.

The lower section 6 comprises a heat storage in the form of a Phase Change Material (PCM), into which a heat-transferring medium in the form of a mineral oil can be diffused.

In a preferred embodiment of the invention, the PCM is sodium acetate trihydrate, which is a salt with its melting point at 58° C. In the melting process, this salt accumulates large amounts of thermal energy, which is gradually released again as the salt solidifies. Thus, the salt works as a heat storage, in which heat energy is stored when the salt melts and "withdrawn" when the salt solidifies.

One reason for choosing an oil as heat-transferring medium is that sodium acetate trihydrate is soluble in water. Thus, if the material is diluted with water, its latent heat capacity will be reduced significantly.

In a preferred embodiment of the invention, a mineral oil is used as heat-transferring medium according to the "Direct Heat Transfer" principle, which means that the heat-transferring medium is in direct physical contact with the PCM to and from which heat energy is transferred.

This use of the latent heat of fusion from sodium acetate trihydrate makes it possible to obtain a very large heat storage capacity within a limited physical volume. This "heat battery" is arranged so that it can be "charged" with heat energy, for instance, from solar panels or from a heat pump. In the case of a solar panel, the mineral oil can be circulated directly through the solar panels, whereas a (plate) heat exchanger between the oil and the refrigerant of the heat pump will be used, if a heat pump is chosen as heat source for the heating system.

The heating system according to the present invention can deliver the necessary heat energy for the central heating system of a building (radiators, floor heating and/or caloriferes) as well as for domestic hot water at 50° C for a normal private household. A Smart Grid Controller connected to a central server via the internet controls the heating system. Thus, it is ensured that heat energy is produced under optimal meteorological and economic conditions and with the highest possible Coefficient of Performance (COP) taking into account the consumption levels and patterns of the house.

The controller collects all vital operational data from the heating system and reports to the central server, from where the operation of a large number of installed heating systems can be monitored and controlled. The central server is also arranged to collect information from electricity networks about actual loads and electricity prices as well as meteorological information such as local weather forecasts.

Furthermore, the central server is arranged to adapt to the different consumers' individual consumption patterns taking the weekly cycle into consideration when planning the heat production of the individual heating systems monitored and controlled by the server.

Being dependent on internet access, the controller is equipped with an internet connection (for instance Ethernet, WiFi or 3G). In case the controller loses the connection to the central server, a thermostatic control will take over and ensure that the consumer does not experience any lack of heat or hot water.

Thus, the heating system according to the present invention constitutes a complete integrated heating system for heating and domestic hot water of residential buildings. The system is especially developed in order to offer a direct substitution for oil, gas or pellet furnaces in the older part of the housing stock. However, the system is also suitable for substitution of other heat sources and in modem buildings.

Fig. 2 is a perspective side view of the same heating system as shown in Fig. 1 with some of the side covers removed so that some of the components inside the heating system are revealed.

For instance, it can be seen that the upper section 1 is more or less filled with an oil layer 11 within which the heat exchanger array 12 is arranged. This oil layer 11 rests upon the salt layer 13 within the lower section 6 because the salt has a significantly higher density than the oil.

As mentioned, all heat exchangers 30, 31, 32 in the heat exchanger array 12 are arranged within the heated oil in the upper section 1. This ensures an optimal efficiency of the heating system because there is no heat loss out of the system and any solidified salt within the heat exchangers 30, 31, 32 can be melted by means of the bypass circuit 14, 15, 18, which is described below.

As mentioned above, the lower section 6 constitutes a salt layer 13. For the sake of visibility, the salt in this salt layer 13 is not shown. What is visible therein is a diffuser unit 17 comprising an oil-circulating pipe 16 and a bypass coil 18 with a bypass forward pipe 15 and a bypass return pipe 14 as described below. A check valve 21 is arranged just after the oil-circulating pump 4 to ensure that the oil within the central oil-circulating pipe 16 is not displaced by the brine of melted salt so that there is only oil within the circulation circuit. This check valve 21 is necessary, because the density of the salt is about twice the density of the oil. If there was no check valve 21, the salt could press the oil back through the circulating pipe 16 to the level of the salt layer in case the pump 4 was stopped.

Figs. 3 and 4 are a perspective side view and a perspective bottom view, respectively, of the diffuser unit 17 shown in Fig. 2. The main part of this diffuser unit 17 is a micro-perforated plate 19, typically a metal plate perforated with a large number of perforations with diameters in the range from 1 mm to 5 mm.

The micro-perforated plate 19 covers the bottom of the salt layer 13 within the lower section 6 and is connected with the oil layer 11 within the upper section 1 through an oil-circulating pipe 16 ending in a centrally arranged oil-circulating outlet 20 on the bottom side of the micro-perforated plate 19. Mineral oil, which has been heated or cooled in the heat exchanger array 12 is pumped through the oil-circulating pipe 16 to the bottom side of the micro-perforated plate 19, where it is equally distributed across the bottom of the salt layer 13 and from where it penetrates the salt from the bottom and upwards through the perforations. The direct physical contact between the oil and the salt ensures an optimal heat transfer between the two substances.

The perforations also function as a sieve ensuring that small flakes of solidified salt does not end up under the micro-perforated plate 19 if the oil is pressed back through the micro-perforated plate 19 due to the higher density of the salt.. Such flakes of salt under the micro-perforated plate 19 would be disruptive for the equal distribution of oil there.

In some cases, for instance at cold start-ups of the system after installation or maintenance, or when the system has been out of operation for a longer time, for instance in case of power failure or system defects, the salt can solidify in large, massive crystal formations, which are hard or even impossible for the oil to penetrate. In such cases, the bypass coil 18 and the bypass forward pipe 15 and the bypass return pipe 14 come into use.

Heated mineral oil can be pumped through the bypass forward pipe 15, the bypass coil 18 and the bypass return pipe 14, whereby the salt will start melting from the bottom up and along the two pipes 14, 15 passing through the salt layer 13. As "channels" for the oil gradually open within the solidified salt, the pressure drop in the primary oil circuit will decrease and the bypass coil has done its job. In preferred embodiments of the invention, the bypass coil 18 arranged under the micro-perforated plate 19 and the two pipes 14, 15 all consist of a corrugated or smooth pipe made from copper, steel or another suitable metal.

Fig. 5 is a schematic diagram of the piping and different components of a heating system according to an embodiment of the invention.

On the left side of the diagram, the tank with an upper section 1 and a lower section 6 is displayed, inside which the salt layer 13 and the oil layer 11 is separated by the dotted line.

Oil is pumped from the oil-circulating inlet 34 by the oil-circulating pump 4 and channeled through the heat exchanger array 12 consisting of the domestic hot water heat exchanger 30, the central heating heat exchanger 31 and the refrigerant heat exchanger 32.

If the motor valve for domestic hot water 45 is open, the domestic hot water heat exchanger 30 is fed with hot oil, thus enabling domestic hot water production. This motor valve for domestic hot water 45 is triggered if the domestic hot water flow switch 37 registers consumption on the hot water tap. From the domestic hot water heat exchanger 30, the oil flows through the oil-circulating pipe 16 to the diffuser unit 17. On the water side, the domestic hot water heat exchanger 30 is connected to the inlet for domestic cold water 7 and supplies domestic hot water through the domestic hot water outlet 55.

If, on the other hand, the motor valve for domestic hot water 45 is closed and either the motor valve for diffuser flow 35 or the motor valve for bypass flow 36 is open, the oil is channeled through the central heating heat exchanger 31 and thereafter through the refrigerant heat exchanger 32. The central heating heat exchanger 31 produces heat to the central heating circuit 42 of the building through the mixing valve 43. Within the central heating circuit, the central heating circulating pump 41 circulates the brine, the expansion vessel 39 absorbs the expansion of the brine due to the temperature changes, and the pressure can be monitored on the pressure meter 40.

In normal operation of the heating system, the oil flows through the open motor valve for diffuser flow 35 and through the oil-circulating pipe 16 to the diffuser unit 17. In some cases, however, the motor valve for diffuser flow 35 closes and the motor valve for bypass flow 36 opens. In such cases, the heated oil from the refrigerant heat exchanger 32 flows through the bypass forward pipe 15 to the bypass coil 18 arranged at the bottom of the lower section 6 below the diffuser unit 17 before it returns to the bypass oil return 33 within the oil layer 11 through the bypass return pipe 14.

The bypass circuit serves different purposes: 1. Restart of the heating system after system malfunction: In case the heating system has been without electricity for several days, there is a risk that the salt has frozen, at least partly, to a solid mass. By triggering a bypass operation, it is possible to channel the heat from the heat pump 47 to the bottom of the salt layer 13, causing the heat to melt the salt slowly, thereby opening channels for the oil circulation via the diffuser unit 17 to start. 2. Low temperature bypass: If low temperature operation is chosen by the controller, the motor valve for bypass flow 36 opens and the heat pump 47 produces heat at a defined temperature, which is controlled by the controller. 3. Oil filtration option: An optional oil filter 50 can be arranged within the bypass circuit 14, 15, 18 for filtration of the oil. 4. Auxiliary electrical heating option: Optional auxiliary electric heating can be arranged within the bypass circuit 14, 15, 18 if electrical resistive heating is preferred.

When oil flows through the refrigerant heat exchanger 32 and heat energy must be added to the heat storage, the heat pump 47 is switched on by the controller. Heated refrigerant then flows through the refrigerant heat exchanger 32 and delivers heat energy to the oil.

When the sun is shining, the solar pump 53 is switched on, and oil is circulated from the solar suction point 51 to the solar thermal collectors 52 and back to the solar return point 54 within the oil layer 11. The speed of the solar pump 53 is controlled by the controller.

List of reference numbers 1. Upper section 2. Energy meter 3. Flow meter 4. Oil-circulating pump 5. Motor valve 6. Lower section 7. Inlet for domestic cold water 8. Central heating return 9. Refrigerant inlet 10. Refrigerant outlet 11. Oil layer 12. Heat exchanger array 13. Salt layer 14. Bypass return pipe 15. Bypass forward pipe 16. Oil-circulating pipe 17. Diffuser unit 18. Bypass coil 19. Micro-perforated plate 20. Oil-circulating outlet 21. Check valve 30. Domestic hot water heat exchanger 31. Central heating heat exchanger 32. Refrigerant heat exchanger 33. Bypass oil return 34. Oil-circulating inlet 35. Motor valve for diffuser flow 36. Motor valve for bypass flow 37. Domestic hot water flow switch 38. Energy meter, domestic hot water 39. Expansion vessel 40. Pressure meter 41. Central heating circulating pump 42. Central heating circuit 43. Mixing valve 44. Energy meter, central heating 45. Motor valve for domestic hot water 46. Flow meter, oil circulation 47. Heat pump 48. Circulating pump for thermal fluid 49. Optional auxiliary electric heating 50. Optional oil filter 51. Solar suction point 52. Solar thermal collectors 53. Solar circulating pump 54. Solar return point 55. Domestic hot water outlet

Claims

PHASE CHANGE MATERIAL-BASED HEATING SYSTEM

A heating system having a heat storage comprising a phase change material in direct physical contact with a heat transfer medium, wherein the heat transfer medium is arranged to be contacted with the phase change material through a spacer (17) arranged below the phase change material and the spacer is provided with a bypass circuit (14, 15, 18) through which a heat transfer medium can pass for melting of the fractured phase change material around the spreading unit, for example after longer periods during which the heating system has been out of operation.

A heating system according to claim 1, wherein the spreading unit comprises a perforated plate (19) through which perforations the heat transfer medium is arranged to penetrate the phase change material from the bottom upwards.

A heating system according to claim 2, wherein the perforated plate is a metal plate having at least 1000, preferably at least 5000, perforations having diameters ranging from 1 mm to 5 mm, preferably about 2 mm.

4. A heating system according to any one of the preceding claims, wherein the phase change material is sodium acetate trihydrate or another salt having similar latent heat properties.

5. Heating system according to any of the preceding claims, wherein the heat transfer medium is a mineral oil.

A heating system according to any one of the preceding claims, further comprising a control unit connected, for example, via the internet, to a central server, which central server is arranged to monitor and control one or more such heating systems. in such a way that the heat production for each of the one or more such heating systems is optimized with regard to the economical operation of the heating system.

7. Heating system according to claim 6, wherein the central server is arranged to take into account one or more of the following parameters when planning the heat production for a given heating system: vital functional data from the given heating system reported to the central server from the controller. this heating system - information from the electricity grids about actual loads and electricity prices meteorological information such as local weather forecasts for the position of the given heating system recorded consumption patterns for the given heating system.

A spreading unit (17) for a heating system according to any one of the preceding claims, which spreading unit comprises a perforated plate (19) through which perforations the hot co-protruding medium is adapted to penetrate a bottom phase change material and upwardly, and wherein the spreading unit is provided with a bypass circuit (14, 15, 18) through which a heat transfer medium can pass to melt the molded phase transfer material around the spreading unit.

Spreading unit according to claim 8, wherein the perforated plate is a metal plate having at least 1000, preferably at least 5000, perforations with diameters ranging from 1 mm to 5 mm, preferably about 2 mm.