WO2021136725A1

WO2021136725A1 - A heating system and a method for heating a chosen media

Info

Publication number: WO2021136725A1
Application number: PCT/EP2020/087634
Authority: WO
Inventors: Adam Fjaestad
Original assignee: Sunfuria Ab
Priority date: 2020-01-03
Filing date: 2020-12-22
Publication date: 2021-07-08
Also published as: SE544220C2; ZA202208529B; SE2050001A1

Abstract

The invention relates to a heating system for heating a substance, preferably a liquid, comprising a heat storage vessel (2) with a heat storage medium (HM1) to be heated by means of a heat source (5) and a sealed tubing (4) arranged to transfer heat to a heat transfer unit (7), said sealed tubing (4) having a partial filling of a substrate partially in liquid state (W) and partially gas state (G) and comprising a return tube (41) arranged to return substrate in liquid state (L) from said heat transfer unit (7) and a supply tube (40) arranged to supply heat in gas state (G) to said heat transfer unit (7), wherein a part of said sealed tubing includes a condensing tubing (77) that is included in said heat transfer unit (7) and positioned above a third system level (L3) and the upper liquid level of said heat storage medium (HM1) is positioned below said third system level (L3), characterized in that an outlet tube (77B) of said condensing tubing (77) is connected to a control member (410) at a second system level (L2), which control member (410) includes a movable connector part (413), wherein said movable connector part (413) is controllably, movably arranged between a first position (415) and a second position (416) a vertical distance (L) apart, wherein said first position (415) coincides with said third system level (L3) or is at a second system level (L2) above said third system level (L3) and said second position (416) is in level with a first system level (L1), wherein a substantial portion of said condensing tubing (77) corresponding to a contained condensing volume (VM) is positioned below said first system level (L1). It also relates to a method for heating a substance.

Description

A HEATING SYSTEM AND A METHOD FOR HEATING A CHOSEN MEDIA

TECHNICAL FIELD This invention relates to a system for heating liquid, comprising a heat storage vessel that acts as a heat storage, a first sealed duct having a partial filling of water under sub- atmospheric pressure, having an upper part arranged to supply heat from the heat storage vessel to a heat exchanger device acting as a heat transfer unit, and in some cases a second sealed duct of the same kind arranged to supply heat to the heat storage vessel from, e.g. a solar heat-collecting panel.

BACKGROUND

It is known to use different types of technologies and methods for cooking and heating of liquids, e.g. water. For instance, one can use solid fuel, gas, electric resistance heaters or induction, the latter being a relatively new technology that is efficient and allows for fast heating. It is also known to use solar heat for the heating of water, both for domestic hot water and for cooking, which could help make life easier for many people, especially in poor areas of the world. In that regard it is known to use phase changes of different media, e.g. water, for heat transportation.

From GB 2032613 there is known a system for water heating in domestic hot water systems, wherein the water heating system utilizes the principle of heat transfer by vapour generated at low pressure, to convey heat from a solar heat-collecting panel to a vessel in which water is to be heated. It comprises a vapour transfer heating with a sealed duct partially filled with a liquid under sub atmospheric pressure. The duct has a first part arranged in heat exchange relation with the water and a second part located within the solar heat collecting panel, the arrangement of the duct being such that in use of the system vapour produced by heating of the second part of the duct passes into the first part of the duct where it condenses, giving up heat to the water in the vessel. Thereafter the condensed liquid is conveyed back to in a closed cycle. This known system has its advantages in regard to using solar energy to warm water for use within buildings, e.g. to be used as warm tap water. However, there is disadvantage with the known system in that it may only provide moderately heated water. From W02016185031 there is known a system that is an improvement over the prior art, such that boiling water may be provided, in a cost-efficient and flexible manner. It discloses a system for heating liquid, comprising a heat storage vessel that acts as a heat storage, a first sealed duct having a partial filling of water under sub-atmospheric pressure, having an upper part arranged to supply heat from the heat storage vessel to a heat exchanger device acting as a heat transfer unit, and a second sealed duct of the same kind arranged to supply heat to the heat storage vessel from, e.g. a solar heat- collecting panel. This system fulfils its purpose but presents some disadvantages from a design perspective.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved liquid heating system that may provide for boiling water, by transferring heat from a heat source or a heat storage to the heat transfer unit as defined in claim 1.

Thanks to the invention many applications can draw benefit from rapid heating of chosen media, e.g. water, to boiling temperature, e.g. kitchen appliances for cooking and hot water for cleaning purposes, etc, wherein quickly different modes can be chosen to either use the heat source to directly heat the heat transfer unit or to store heat in the heat storage.

Thanks to the invention according to one embodiment according to the invention a solar heating system makes it possible for many people to make easy use of solar energy to heat water or other liquids that may be used for cooking food and/or preparation of hot drinks and also for other purposes.

In transferring heat from the heat storage vessel to the heat transfer unit the system makes use of the phase change between liquid and gas, in the claims referred to as transfer medium. Water can be used as well as refrigerants with no or little temperature glide. Water is an easily available liquid and the temperature at which water boils is reduced as the pressure on the water is reduced, likewise the boiling temperature is higher if the pressure is higher. Thanks to the fact that the heat transfer in the heat storage vessel and in the heat transfer unit takes place essentially through the evaporation and the condensation of the water in sealed ducts, the operation of the system is potentially highly efficient since there will be a negligible temperature gradient between the two heat exchanger devices. In the example of water, to a part filling the ducts/tubes in lower section and the higher being filled with water vapour, will boil and condensate at the same temperature set by the balance between the two parts. This process will continue as long as there is a driving force, e.g. a temperature difference between the lower part of the tube and the higher. A possible preferable combination of temperature and pressure when the energy storage vessel is loaded with energy can be 160 C and 6 bar(A). In one exemplary use of the system of the invention, with the tubes half filled with water in liquid state that are connected to an associated solar heat collecting device that is exposed to the sun may cause water within the tube to boil at 160 C, producing vapour which is heated further before leaving the solar heat collecting device and then passes through the tubing either directly to the heat transfer unit or to the heat storage vessel, where the water vapour condenses, giving up its latent and sensible heat. If to the heat medium in the storage vessel, the condensed water will return to the solar-heat- collecting device. If directly to the heat transfer unit, the condensed water will also return to the solar-heat-collecting device. The hot heat medium in the heat storage vessel in a similar manner may, when the heat source is off, cause water to boil at 160 C, producing vapour which passes to the cooking device, where it quickly can cause water to boil by condensation and the condensed water therefrom will return to the heat storage vessel in a similar manner may, when the heat source is off, cause water to boil at 160 C. The system preferably relies upon gravity to maintain the circulation of water in the sealed ducts, by arranging that the heat/vapour producing parts at a lower level than the heat emitting condensation parts.

BRIEF DESCRIPTION OF THE FIGURES The invention will now be further described, by way of example, with reference to the accompanying schematic figures, in which:

Figure 1 is a schematic view of an embodiment of the invention, in a one stage of operation,

Figure 2 is a schematic view of the same embodiment of the invention as Fig 1, in a first different stage of operation.

Figure 3 is a schematic view of the same embodiment of the invention as Fig 1, in a second different stage of operation.

Figure 4 is a schematic view of the same embodiment of the invention as Fig 1, in a third different stage of operation. Figure 5 is a cross-sectional schematic view of an alternate embodiment of a cooking vessel within the heat transfer unit, and In Fig 6 and 7 it is shown that in alternate embodiments of the invention the basic principles thereof may also be used in connection with two separate closed systems.

DETAILED DESCRIPTION The principle of the invention is to primarily use the latent heat in the phase changes between liquid and vapour of a transfer medium in order to transport heat to a colder medium, wherein a sealed tubing 4 is used having a partial filling of a liquid, wherein water is the preferred medium. The transfer medium and pressure within the sealed tubing 4 including it is chosen to have appropriate vaporisation/condensation levels. When using water, it is preferred to arrange a slight over pressure, within the sealed tubing 4, e.g. a pressure of about 1,4 to - 1,6 bar, to obtain a vaporisation temperature in the range of 150 - 200 °. The system preferably relies upon gravity to maintain the circulation of liquid in the sealed tubing, by arranging the heat absorbing vaporization parts of a heat transfer tubing 4 to pass through heat importing members 2, 5 at a lower level than the level of the heat delivering condensation parts of the heat transfer tubing 4, hereinafter referred to as a heat transfer unit 7. As shown in figures 1-4, the invention comprises a heat storage vessel 2 arranged below the heat transfer device unit 7. The heat storage vessel 2 serves as a heat storage and a heat exchanger device that may provide heat to the heat transfer unit 7, which in turn may transfers heat to a cooking vessel 70 containing a liquid W to be heated, e.g. water, positioned in the heat transfer unit 7. The space V of the heat storage vessel 2 containing a volume V’ of a heat medium HM1 that should not boil at the operating temperatures, preferably filled with oil, e.g. 500 - 2000 litres.

The invention also includes a sealed tubing 4 that comprises a supply tube 40 that may transfer heat from the heat storage vessel 2 to the heat transfer unit 7. The supply tube 40 leads to a condensation space 73A within the heat transfer unit 7. In a return tube 41 fluid from the heat transfer unit 7 may be returned to the heat storage vessel 2. The tubes 40, 41 may be made of solid or flexible material, but must regardless be completely sealed. In the preferred embodiment metal is used in the sealed tubing 4, for good heat conduction, e.g. cupper tubes having a diameter of 15- 30 mm.

The condensation space 73A is preferably contained in a storage vessel 73 that is filled with a heat transfer fluid HM2, e.g. frying oil, in an amount V” substantially smaller than V, e.g. about 1 - 5% of the volume V’ of oil in the heat storage vessel 2. The cooking vessel 70 may be withdrawable from an opening 701 at the top that matches the outer diameter of the cooking vessel. Preferably there is arranged some kind of collar and sealing means 70C at the outer surface of the cooking vessel 70 that both supports the cooking vessel 70 in the heat transfer unit 7 and seals, e.g. a labyrinth seal, wherein the seal enables vapor/steam to escape from the inner but hinders water from entering into the opening 710. The collar and sealing means 70C, is positioned at level such that a desired portion 70A of a lower part of the cooking vessel 70 is contained within the oil in the condensation space 72A, i.e. in direct heat conducting contact with the cooking vessel 70.

The heat transfer unit 7 has a housing 71 that has an isolating layer 71A to minimize heat leakage out from the inner of the heat transfer unit 7. The storage vessel 73 is positioned inside the housing 71. Within the inner of the heat transfer device 7, the sealed tubing 40,41 includes a central condensing tubing part 77C, e.g. in the form of a back and forth running tubing part 77C. A substantial portion of said central condensing tubing part 77C is positioned within the condensation space 73 A. The central condensing tubing part 77C preferably provides a relatively long path, e.g. 15 - 30 m. Partly to provide a large surface exposure, partly to contain a desired volume VH.

Preferably, a major portion of the central condensing tubing part 77C that is arranged within the condensation space 73A is in the form of a spirally wound tubing part 77A, that is arranged outside of /enclosing a desired portion 70A of the lower part of the cooking vessel 70. The condensation space 73A need not be sealed. An inlet tube 77A leads from above into the heat transfer unit 7 and there connects to the central condensing tubing part 77C and an outlet tube 77B leads away from and downwards from the heat transfer unit 7. Hereinafter these tube parts 77A-C will be referred to as the condensing tubing 77. A control member 410, preferably pivotable, e.g. in the form of a U-shaped tube part 410 is connected in between the heat transfer unit 7 and the return tube 41, which U- shaped tube part 410 comprises a first leg 411, a second leg 412 and a connector part 413. The pivoting axis 415 is positioned at a second system level L2 that may coincide with a lowest point of the outlet tube 77B from the heat transfer unit 7. When the U- shaped tube part 410 is positioned vertically (see Fig. 1) the connector part 413 will be at a position corresponding to a first system level LI that determines the maximum volume VM of liquid that may be contained in the condensing tubing 77. In the shown example the first system level LI is above a highest possible water level Wl, e.g. above the highest point of an inlet tube 77A to the heat transfer unit 7, connecting to the supply tube 40. The highest point of the inlet tube 77A connects to an uppermost part of the supply tube 40 and from that point gravity will arrange for flow into the condensing tubing 77. Accordingly, this position 416 of the connector part 413 will cause a hinder increasing the level of pressure needed in the supply tube 40 for fluid to circulate in the tubes 40, 41 and due to the fact that the pressure is constant within the sealed tubing 4 no circulation will then occur. In the figures it is shown an exemplary embodiment where the highest point of the inlet tube 77 A is positioned at a distance away from the housing 71. However, the highest point may also be positioned near housing 71 or at the outer wall of the housing 71 or even inside the housing 71. The heat storage vessel 2 is positioned below a third system level L3. This third system level L3 is positioned below the condensing tubes 77 of the heat transfer device 7, i.e. between the heat storage vessel 2 and the active parts of heat transfer device 7. Preferably the heat storage vessel 2 is substantially filled with the heat storage medium HM1, preferably at least above 90%. Within the inner of the heat storage vessel 2 there is an exchange tubing 42, which may include back and forth running tubing parts, or a plurality of parallel arranged tubes (not shown), e.g. of a smaller diameter than that of the condensing tubing 77. In total the tubing must contain a desired volume VS that is substantially equal to the volume VH of the condensing tubing 77. For both tubing 42,

77 the surface exposure may be enlarged by arranging fins/flanges (not shown).

The basic heat importing member of the system is a solar collector 5, having a concave reflecting collector surface 500 that reflects the collected sun beams into an axis where a collector tube 430 of a solar supply tube member 43 is positioned. As mentioned above the system preferably relies upon gravity to maintain the circulation of liquid in the sealed tubing 4, wherein different parts of the system are mounted at positions related different horizontal levels LI, L2, L3 and L4 of the system. The collector tube 430 is therefore preferably positioned below a fourth system level L4, wherein the fourth system level extends below the heat storage vessel 2. The solar supply tube member 43 connects to the supply tube 40 at a position 43A that is above the heat storage vessel 2. The design of the concave reflecting collector surface 500 is preferably such that a temperature of above 400° C is obtained in the collector tube 430 of the solar supply tube member 43. Accordingly, the solar energy impinging upon the solar collector 5 heats the water within the collector tube 430 and causes the latter to boil at a temperature which will be determined by the pressure and kind of liquid within the sealed tubing 4, wherein water is preferred, and a pressure is chosen to typically obtain vaporisation at between 150 C and 180 C.

The common heat transfer process as shown in figures 1-4 operates according to the following principle.

To start with it is assumed that the system is totally empty of stored energy, which has been achieved by first positioning the pivotable control member 410 in its low position 415, (see Fig. 2) whereby stored heat is taken out and thereafter (due to no sun during night) all parts assume the same temperature of the surroundings. This implies that the temperature within the heat transfer unit 7, the heat storage vessel 2 and the sealed tubing 4 is more or less the same and all liquid W is collected in a lower part of the sealed tubing 4 (see Fig. 2).

During start of the process the pivotable control member 410 is preferably set in its blocking position (see Fig. 3), i.e. having the connecting member 413 at a position 416 at or above the first system level LI, to start storing heat in the heat storage vessel 2. Now, when sun impinges upon the solar collector 5 and vapor starts to produce in the collector tube 430, vapor will move up into the solar supply tube 43, due to the existence of liquid W within the lower part 41B of the return tube 41, below the collector tube 430. Vapor will reach the connection point 43 A to the supply tube 40 and then, at least partly, move into the condensing tubing 77, where it will condense and start filling the condensing tubing 77 (see Fig. 4) and eventually fill the condensing volume VM with liquid W 1 (see Fig. 1). At this latter stage no further circulation through the heat transfer unit 7 will be possible. However, circulation may then occur between the solar collector 5 and the heat storage vessel 2. Vapor produced in the collector tube 430 will continue to move up into the solar supply tube 43, due to the liquid W2 within the lower part 41B of the return tube 41 below the collector tube 430. The vapor will come to the connection point 43A to the supply tube 40 and thereafter be moved down into the exchange tubing 42 within the heat storage vessel 2. The heat exchange tubing 42 will be, at least partly, in gas state, due to the fact that a first amount of liquid W1 is trapped within the condensing tubing 77 (see Fig 1), which in this state corresponds to a maximum volume possible contained volume VM. A second amount of liquid W2 is then contained in the lower part 4 IB of the return tubing 41.

Within the heat storage vessel 2 the vapor will condense and thereby supply heat to the storage media HM1 within the heat storage vessel 2. Thereafter the condensed liquid will flow out of the heat storage vessel 2 at branch 41 A connecting the exchange tubing 42 with the return tubing 41at a position above the lower part 41B of the return tubing

41. Via the lower supply part 41B the solar collecting tube part 430 of the solar collector 5 will again be replenished. This process will continue until there is reached a level of saturation, e.g. when the temperature Tmax of the storage medium HM within the heat storage vessel 2 has reached a high enough temperature wherein the leakage of heat out from the heat storage vessel 2 is equal to the heat input from the solar collector 5. According to the preferred design concept the saturation temperature will be between 200 - 280°C. At this stage the system is loaded with a large amount of stored heat energy within the heat storage vessel 2. The stored heat energy may be freely used at desired times, simply by pivoting the pivotable control member 410 into the second system level L2, i.e. having the connecting member 413 at its lower position 415 whereby heat will start to be transferred from the heat storage vessel 2 to the heat transfer unit 7.

The process will then be that liquid W 1 from the condensing tubing flows down through the return pipe 41 and fills the exchange tubing 42. In turn vapor will be produced within the exchange tubing 42 in the heat storage vessel 2 and move into the heat transfer unit 7 where it condenses and transfers heat to the cooking vessel 70. As is evident the process may continue until a saturation level is achieved, e.g. when the temperature of the oil HM in the heat storage vessel 2 is at a level where it coincides with the vaporization temperature of the water in the sealed tubing 4. However, thanks to the control member 410 the process may be controlled, such that heat supply to the heat transfer unit 7 may be immediately stopped, by again moving the connecting member 413 to its upper position 416. Hence also during build up of heat in the heat storage vessel 2 cooking may be provided by means of the heat transfer unit 7 in a flexible and simple manner.

As can be noted in figure Fig. 1 the first phase of the above described heating transfer process will result in a build-up of an upper water buffer W 1 within the part of the heat transfer device 7, at the same time as the amount of water in the heat storage vessel 2 is diminished. When the upper water buffer W1 is totally filled and the connecting member 413 at its lower position 415 there will be continuous refill of the water into the heat storage vessel 2 thanks to the circulation wherein a continuous addition of condensed water will flow back through the return pipe 41 into the exchange tubing 42 of the heat storage vessel 2.

As mentioned above if the solar collector 5 is active it may be realised that the vapor produced within the tubing 43 of the solar collector 5 will normally be hotter (e.g. 460° C) than the temperature (e.g. 270° C) of the heat storage media HM in the heat storage vessel 2. As a consequence, the refill of heat energy to the heat transfer unit 7 will normally be provided directly from the active solar collector 5, once the connecting member 413 is set at its lower position 415. Consequently, the heat storage vessel 2 will be more or less inactive / bypassed, in this situation. Hence the condensed water supplied through the return tubing 41 from the heat transfer unit 7 will then directly return to the solar collector 5 and circulation will occur more or less without any influence from the heat storage vessel 2.

As is evident this system aspect may advantageously be used if there is spontaneous need of cooking during a heat up-phase of the heat storage vessel 2. Hence, if there is a spontaneous need to interrupt the heat storage build-up it is feasible to quickly arrange for heat delivery at the heat transfer unit 7, by simply pivoting the pivotal control member 410 from its locking, vertical position to its horizontal position. Once the spontaneous need of cooking has been fulfilled, the pivotal control member 410 may again be put into its locking position and the process of building up heat in the heat storage vessel 2 may continue.

Regarding Figs. 5, 6 and 7 it is referred to W02016185031, which is herewith introduced by way of reference. In Fig 5 there is shown an alternate cooking vessel 70 that also may be used in connection with the basic principles of the invention, wherein the condensing tubing 77 includes a cylindrical condensation space 77 of a cooking vessel 70 that is fixed within the heat transfer unit 7. In Fig 6 and 7 it is shown that in alternate embodiments of the invention the basic principles thereof may also be used in connection with two separate closed systems, one 5 for the input of heat and one for the heat transfer to the cooking vessel 70. Briefly describing the principle as shown in Fig 6, there is shown a space G connected to the supply tube 40 above a line P that is filled with vapour G. The supply tube 40 transfers moving vapour to the sealed condensation space 77 of the heat transfer unit 7, that has a heating vessel 70 providing a space filled with a cold liquid (e.g. water), being colder than the vapour. The vapour in the condensation space 77 will then condense against the inner wall and thereby transfer heat to the cold liquid. The condensation results in a high output of heat transfer and the cold liquid is heated in a rapid manner. The condensate flows down and back to the heat heat storage vessel 2 through the return pipe 41, and then recirculated, i.e. eventually again heated up to vapour.

Furthermore, it is evident that also the basic principles according to the invention may be of such dimensions that it is easily moved.

In a test that was performed with a solar heating system 5 according to the invention the following applied;

The oil used had a caloric value of Cp=1.97kJ/kg*K, a density of p=918 kg/m 3, and the volume of the vessel 2 was 10L,

The following values were obtained when performing the test;

The temperature of the oil (emp 1=130-53) was heated about 77 °C The time for heating of the oil was about 210min=12600s

With an energy accumulation of, Q=m*Cp*(T2-Tl)=(918*0.01)*1.970*77=1392kJ, which in turn implies a power input, (qin=Q/deltatimel=1392000/12600) of 110W.

Also, during the charging of the system, all materials such as valves, pipes, tank and the fluids, e.g. in both of the tubing’s 4,5 are heated up. This meaning that the average power in is in fact higher than 110 W.

The material of the tubes 4, 5 is preferably copper: Cp=0.39kJ/kg K, having a thermal conductivity k=401W/(m K).

The initial mass of water was 0.25kg, having Cp, water = 4.2kJ/kg K, The average power as indicated in middle diagram, (up to boiling of water, = Cp,water*m, water* deltaTemp,water/deltatime2 = 4.2*0.25 *(100-33)/28), i.e. 5kW.

The invention is not limited to what is exemplified above but may be varied within the scope of the claims. For instance, it is evident for the skilled person that another liquid than oil may be used with the heat storage vessel 2, e.g. water, but from a safety point of view oil is preferred, and especially a non-toxic oil, such as vegetable oil. Further it is evident for the skilled person that another liquid than water may be used within the sealed tubing 4, e.g. alcohol, but from an availability view point water is preferred.

Moreover, it is evident for the skilled person that the principles of the invention may be used for a variety of heat transfer units/cooking vessels 70, of a different design than that shown in the figures, e.g. instead an oven like space for heating of different items, e.g. non liquid food, or a plate like interface for indirect heating stuff in a pan, or similar cooking vessel. Further, it is evident for the skilled person within the field that the first system level LI must not be positioned above the upper point of the inflow tube 70A. An essential aspect in regard to this feature is that the amount of volume contained in the condensing tubing 77 between the upper and lower positions 416, 415 contains sufficient amounts of liquid to provide for the essential effect according to the invention, i.e. arrange for possibility to relatively quickly change from a mode where a major amount of the supplied heat energy (via ref. 5) is stored in the heat storage vessel 2 to a mode where a major amount of the supplied heat energy is directly supplied to the heat transfer unit 7 and there quickly may heat the cooking vessel 70. In a similar manner also the lowest point 415 must not be positioned below all parts of the condensing unit 77.

Claims

1. A heating system for heating a chosen media, preferably a liquid, comprising a heat storage vessel (2) with a heat storage medium (HM1) to be heated by means of a heat source (5) and a sealed tubing (4) arranged to transfer heat to a heat transfer unit (7), said sealed tubing (4) having a partial filling of a transfer medium partially in liquid state (W) and partially gas state (G) and comprising a return tube (41) arranged to return transfer medium in liquid state (W) from said heat transfer unit (7) to said heat storage vessel (2) and/or heat source (5) and a supply tube (40) arranged to supply heat from said heat storage vessel (2) and/or heat source (5) by means of condensation of said transfer medium in gas state (G) to said heat transfer unit (7), wherein a part of said sealed tubing includes a condensing tubing (77) that is included in said heat transfer unit (7) and positioned above a third system level (L3) and the upper liquid level of said heat storage medium (HM1) is positioned below said third system level (L3), characterized in that an outlet tube (77B) of said condensing tubing (77) is connected to a control member (410) at a second system level (L2), which control member (410) includes a movable connector part (413), wherein said movable connector part (413) is controllably, movably arranged between a first position (415) and a second position (416) a vertical distance (H) apart, wherein said first position (415) coincides with said third system level (L3) or is at a second system level (L2) above said third system level (L3) and said second position (416) is in level with a first system level (LI), wherein a substantial portion of said condensing tubing (77) corresponding to a contained condensing volume (VM) is positioned below said first system level (LI).

2. A heating system according to claim 1, wherein the highest point of an inlet tube

(77 A) of said condensing tubing (77) is positioned below said second position (416).

3. A heating system according to claim 1 or 2, characterized in that said heat source is in the form of a solar collector (5) and that a collector tube (430) is arranged to absorb solar energy from concentrated solar energy within said solar collector (5) arranged to provide a temperature of at least 300°C within said collector tube (430), preferably least 350°C, more preferred at least 400°C.

4. A heating system according to claim 3, characterized in that there is a solar supply tube member (43) connecting the collector tube (430) with said supply tube (40) at a position (43A) downstream of an exchange tubing (42) of the heat storage vessel

(2).

5. A heating system according to claim 3, characterized in that said heat storage vessel (2) is mounted above a fourth system level (L4) and that said collector tube (430) is mounted below said fourth system level (L4).

6. A heating system according to claim 4, characterized in that said condensing volume (VM) contained within said substantial portion of said condensing tubing (77) is substantially equal to a total volume (VS) contained within the exchange tubing (42), wherein the volume difference is less than 10%, preferably less than 5%, more preferred less than 2%.

7. A heating system according to any of claim 1-6, characterized in that said heat transfer unit (7) includes a condensing space (73 A) and that a substantial part of a central condensing tubing (77C) is arranged within said condensing space (73A).

8. A heating system according to claim 7, characterized in that said condensing space (73 A) is limited by a vessel (73) and that said vessel (73) contains a heat transfer medium (HM2).

9. A heating system according to claim 8, characterized in that the volume (VHM1) of the heat medium (HM1) in the heat storage vessel (2) is substantially larger than the volume (VHM2) of heat transfer medium (HM2) in said condensing vessel (73), wherein preferably VHM1 > 10 VHM2.

10. A heating system according to any preceding claims, characterized in that said control member (410) is in the form of tubes in a U-shape having two legs (411, 412), wherein said movable connector part (413) connects said two legs (411, 412) at their ends, and wherein said U-shaped member (411, 412, 413) is arranged to be moved between said two positions (415, 416) either by means of a pivot arrangement or by the use of bendable legs (411, 412).

11. A method for heating a chosen media, preferably a liquid, with a heating system according to any of claims 1-10, comprising the steps of extracting heat from a heat source (5) and by means of a sealed tubing (4) transferring said heat to a heat storage medium (HM1) in a heat storage vessel (2) and/or to a heat transfer unit (7), characterized by providing a control member (410) including a movable connector part (413) and controllably moving said movable connector part (413) between a first position (415) and a second position (416) a vertical distance (H) apart, to control if a major part of said extract heat is to be transferred to the heat storage vessel (2) or to the heat transfer unit (7).