AT18587U1 - Combined hot water and heating storage tank - Google Patents

Abstract

The present invention relates to a combined hot water and heating storage tank (21) comprising a lower storage part (2) and an upper storage part (1), wherein both storage parts (1, 2) each have a storage chamber for storing heating water, wherein the storage chambers of the two storage parts (1, 2) are hydraulically separated from each other, wherein the storage parts (1, 2) each have a flow connection (9, 12) and each have a return connection (10, 13), wherein the lower storage part (2) has a heating circuit flow connection (11) and a heating circuit return connection (14, 16), wherein the upper storage part (1) and the lower storage part (2) are arranged one above the other and connected to each other as a single structural unit, wherein a thermal intermediate insulation (7) is arranged between the two storage parts (1, 2) which thermally insulates the two storage parts (1, 2) from each other, wherein both storage parts (1, 2) are connected by means of a common thermal external insulation (6) are enclosed, which thermally insulate the two storage parts (1, 2) from an environment, wherein an upper heat exchanger (4) is arranged in the storage space of the upper storage part (1) and a lower heat exchanger (3) is arranged in the storage space of the lower storage part (2), each being provided and equipped for heating the drinking water, wherein the lower heat exchanger (3) has a cold water connection (15) for supplying untempered drinking water and the upper heat exchanger (4) has a hot water connection (8) for discharging heated drinking water, wherein the two heat exchangers (3, 4) are hydraulically connected to each other and connected in series.

Description

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Description

COMBINED HOT WATER AND HEATING STORAGE TANK

[0001] The present application relates to a combined hot water and heating storage tank according to claim 1. The combined hot water and heating storage tank serves for the preparation of hot water and heating of buildings in conjunction with a heating device, for example and preferably with at least one heat pump.

[0002] Heat pumps for space heating of buildings and for heating domestic hot water exhibit significantly better efficiency the lower the flow temperature supplied by the heat pump. The aim with heat pumps is therefore always to operate them with low flow temperatures for as much of their operating time as possible.

[0003] Heat pumps typically supply the building with hot drinking water, for example for showering, and with hot heating water to meet the heating demand, i.e., for space heating. As a rule, the temperatures required for providing hot drinking water are significantly higher than the temperatures of the heating water for space heating. Depending on the demand, the heat pump regularly switches between the operating states of "hot water" and "heating". The switchover for charging the storage tank for hot heating water for domestic hot water or for hot heating water for space heating is carried out, for example, by means of a diverter valve or by means of two circulation pumps in the flow line of the heat pump.

[0004] The heating circuit(s) of the respective heating distribution system (e.g. a static heating circuit with radiators and/or a heating circuit with underfloor heating) are generally supplied with one or more additional circulation pumps (heating circuit pump), which pump the heating water from the respective heating storage tank into a heating distribution system that has appropriate pipes for sub-distribution to the respective heating devices (radiators or underfloor heating).

[0005] In normal residential buildings, the majority of the annual heating work is for space heating (about 75%), so the heat pump can be operated at the lower temperatures for space heating in most operating conditions.

STATE OF THE ART

[0006] Two types of storage solutions are typically installed in conjunction with heat pumps:

[0007] Variant 1: separate hot water and heating storage tanks. In this variant, two storage tanks are installed:

ij) A hot water storage tank for the provision of hot drinking water, which is usually operated at 50°C to 60°C.

ii) A storage tank for space heating, which typically operates at lower temperatures of 30°C to 50°C (depending on the heat distribution system, i.e., radiators or underfloor heating). Storage tanks are primarily used to ensure the minimum operating time of heat pumps when, during heating operation, the heat pump's flow rate exceeds the flow rate drawn from the heating circuit. The excess heat energy is then temporarily stored in the storage tank. Furthermore, storage tanks are used to store heat energy, for example, when the heat pump is powered by inexpensive electricity from a home photovoltaic system.

[0008] Disadvantages of setting up two separate storage tanks include an increased space requirement due to the larger installation area and an increased heat loss due to the overall larger external surface area of the two storage tanks.

[0009] Variant 2: Layered storage. Another common storage solution is so-called

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Stratified storage tanks, also called "stratified storage tanks," use a single, shared storage tank for both domestic hot water and space heating. Due to the smaller external surface area, heat losses are lower than in the previously described variant 1. The overall space requirement is also smaller, although the stratified storage tank itself is larger than a single domestic hot water tank or a single heating storage tank from variant 1.

[0010] The entire stratified storage tank is filled with heating water. The domestic hot water is heated either by an internal heat exchanger (for example, and preferably made of stainless steel), through which the domestic hot water flows, or by an external heat exchanger. An internal heat exchanger is typically formed by a helically shaped tube body that is inserted into a storage chamber of the stratified storage tank and is surrounded by the heating water, so that thermal energy can be exchanged through a tube wall of the heat exchanger with the domestic hot water flowing within the heat exchanger.

[0011] The upper section of a stratified storage tank is used exclusively for heating domestic hot water, while the lower section is used for supplying space heating and preheating domestic hot water. The upper section of the stratified storage tank is heated by the heat pump to higher temperatures (e.g., 50°C to 60°C), and the lower section to lower temperatures (e.g., 30°C to 50°C). Due to the temperature-dependent density of water and gravity, this temperature stratification is maintained for a certain period of time.

[0012] However, thermal conduction, entrained currents, and kinetic energy during charging counteract temperature stratification. This results in a partial mixing of temperatures within the stratified storage tank, causing the upper part of the tank to cool down and thus requiring more frequent recharging with higher temperatures by the heat pump. The resulting increase in the proportion of high temperatures in the overall heating work of the heat pump reduces the heat pump's efficiency.

[0013] A circulation system for hot drinking water, which is present in many houses via a circulation pipe system and ensures that hot drinking water is quickly available at the taps, can also cause the upper part of the stratified storage tank to cool down significantly faster. This is particularly the case if the drinking water circulating through the heat exchanger first flows through the lower, cooler area of the stratified storage tank and then through the upper, warmer area of the stratified storage tank.

[0014] The maximum stratification efficiency achievable on the test bench for very good stratified storage tanks is between 80% and a maximum of 90%. In practical operation, however, the stratification efficiency is often significantly lower due to changing flow rates. A stratification efficiency of 100% describes perfect temperature stratification of the heating water in the storage tank without disturbances, while a stratification efficiency of 0% describes complete mixing of the storage tank. One advantage of a stratified storage tank with an internal heat exchanger is that the lower section of the storage tank, which is intended for room heating, can preheat the domestic hot water as the domestic hot water flows through the heat exchanger from bottom to top. In this case, a cold water connection is provided at one lower end of the stratified storage tank and a hot water connection at one upper end.

[0015] Both of the aforementioned variants of storage solutions that are common today for operation with heat pumps have their own advantages and disadvantages.

[0016] A further disadvantage arises with both variants in the hydraulic integration of heating storage tanks or stratified storage tanks as buffer tanks. Heating storage tanks and stratified storage tanks are very frequently installed as so-called "buffer tanks" in conjunction with heat pumps for the heating system. This hydraulic integration describes the situation that the heat pump has its own flow connection for the warmer flow of the heat pump in the upper part of the heating storage tank for charging the heating storage tank or stratified storage tank.

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chers (in the middle area of stratified storage tanks) and a separate return connection for the cooler return of the heat pump in the lower area of the heating storage tank or the stratified storage tank to charge the respective storage tank.

[0017] The heating distribution system, which, for example, extracts thermal energy from the respective storage tank to supply radiators, also uses its own heating circuit supply connection. This connection is located in the upper section of standard heating storage tanks and in the middle section of stratified storage tanks. Furthermore, each storage tank has its own heating circuit return connection in the lower section. For example, the heating circuit supply is approximately 5 K to 10 K warmer than the heating circuit return in the case of heat pumps. Integration as a buffer storage tank is advantageous because the flow rate of the heat pump for supplying heat to the storage tank and the flow rate of the heating distribution system for extracting thermal energy for space heating can fluctuate considerably and differ from each other. Both flow rates are conveyed by their own separate circulation pumps. This also leads to a mixing of temperatures within a heating storage tank or in the lower area of a stratified storage tank, namely in this described case not between the area for heating the domestic hot water and the area for space heating, but due to the different flow and return temperatures of the heating distribution system only in the heating storage tank or in the lower area of the stratified storage tank.

[0018] If the heat pump charges the storage tank, for example with a flow temperature of 40°C, the mixing may result in the heating distribution system being supplied with a flow temperature of, for example, only 38°C, which in turn means a loss of efficiency for the heat pump.

TASK

[0019] The present invention is therefore based on the objective of providing a hot water and heating storage tank which, in conjunction with a heating device designed as a heat pump, avoids the disadvantages of the known variants, which have a negative impact on the efficiency of the heat pump.

SOLUTION

[0020] The underlying problem is solved by means of a combined hot water and heating storage tank with the features of claim 1. Advantageous embodiments are described in the dependent claims, the description, and the exemplary embodiment.

[0021] The hot water and heating storage tank according to the invention comprises a lower storage part and an upper storage part. Both storage parts each have a storage chamber for storing heating water that has been tempered by the heat pump. The storage parts can, for example, each be formed by steel tanks, and both storage parts can be the same size or of different sizes. Preferably, both storage parts can be rotationally symmetrical and have at least substantially the same diameter.

[0022] The storage chambers provided by the storage components, each of which can hold a volume of heating water, are hydraulically separated from one another. In this way, the volumes of heating water held in the storage chambers of the storage components cannot mix.

[0023] The two storage compartments each have a flow connection for connecting the respective storage compartment to a flow line of the heat pump and each have a return connection for connecting the respective storage compartment to a return line of the heat pump. To provide different temperatures, the flow connections can be connected to different flow lines of the heat pump. However, the flow connections can also be connected to the same flow line of the heat pump. The same applies to the return connections.

[0024] The lower storage part has a heating circuit supply connection for connecting the storage tank.

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The lower storage compartment is connected to a flow pipe of the building's heating distribution system and to a return pipe of the heating circuit. Thus, the lower storage compartment serves for space heating. In other words, the heating distribution system is supplied with heated water from the lower storage compartment. The temperature of the heating water in the lower storage compartment is lower than in the upper storage compartment, for example, in the range between 30°C and 50°C. In the upper storage compartment, the temperature of the heating water is, for example, and preferably, between 50°C and 60°C.

[0025] The upper storage part and the lower storage part are arranged one above the other and connected to each other as a single structural unit. For example, and preferably, the two storage parts can be mechanically screwed, welded, or glued together, or a combination thereof. Preferably, the upper storage part is supported on the lower storage part by means of connecting feet. The lower storage part can, for example, and preferably, interact with feet by means of which the lower storage part can be placed on a surface.

[0026] Preferably, thermal insulation is arranged between the two storage parts, which thermally isolates the two storage parts from each other. This insulation can, for example, and preferably, be thermal insulation known in the art for insulating water storage tanks. The insulation reduces the exchange of heat energy between the two storage parts.

[0027] Furthermore, both storage components are enclosed by a common external thermal insulation, which thermally insulates the two storage components from the environment. In this way, the loss of heat energy to the environment or to the outside is reduced. The external insulation can be made of thermal insulation material known per se, which is commonly used for insulating water storage tanks. In particular, the intermediate insulation and the external insulation can be made of the same material.

[0028] An upper heat exchanger is arranged in the storage space of the upper storage section, and a lower heat exchanger is arranged in the storage space of the lower storage section. Both heat exchangers are, for example, and preferably, made of stainless steel. For example, the heat exchangers can each be designed in the form of a coiled pipe. The heat exchangers are each designed and configured for heating the drinking water. In particular, thermal energy from the heating water can pass through a wall (especially a pipe wall) of the respective heat exchanger into the drinking water flowing within the heat exchanger, thereby successively heating the drinking water as it flows through the heat exchangers.

[0029] The lower heat exchanger has a cold water connection for supplying unheated drinking water, and the upper heat exchanger has a hot water connection for discharging heated drinking water. The two heat exchangers are hydraulically connected and flow-wise arranged in series, so that unheated drinking water from the cold water connection first flows through the lower heat exchanger and is heated by the heating water located in the storage chamber of the lower storage unit. The (pre-)heated drinking water can then flow from the lower heat exchanger into the upper heat exchanger and through it towards the hot water connection. Here, the drinking water is further heated by the heating water located in the storage chamber of the upper storage unit. Finally, the (fully) heated drinking water can exit the upper heat exchanger at the hot water connection.

[0030] The combined hot water and heating storage tank specified in claim 1 has many advantages. In particular, it utilizes the advantage of a smaller storage shell (low heat loss and smaller footprint) with complete thermal separation of both temperature ranges, i.e., of the two storage components (heating of domestic hot water in the upper storage part).

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(and extraction of heating water for space heating in the lower storage section). There is no mixing of the volumes of heating water held in the storage chambers of the two storage sections, and consequently, no associated efficiency losses. Furthermore, the potable water is preheated in the lower storage section as it flows through the lower heat exchanger, thus reducing the proportion of high temperatures required for heating the potable water to a desired final temperature level (e.g., 50°C) in the upper storage section, relative to the overall heating work of the heat pump. The invention allows the heat pump to be operated significantly more efficiently, resulting in lower overall electricity consumption.

[0031] In an advantageous embodiment, the combined hot water and heating storage tank includes a bypass lance by means of which the flow connection of the lower storage section and the heating circuit flow connection are directly connected to each other in terms of flow flow. The bypass lance thus allows the heating water to flow directly from the heat pump flow into the heating circuit flow without first having to enter the storage space of the lower storage tank. The bypass lance extends through the storage space of the lower storage section and has an annular gap through which heating water can flow into the storage space of the lower storage section and heating water can flow from the storage space of the lower storage section into the bypass lance. In other words, it is possible both to introduce water from the heat pump's flow pipe through the annular gap into the storage chamber of the lower storage tank section, thereby "charging" it (with thermal energy), and to extract thermal energy from the storage chamber, with the heating water flowing through the annular gap and the overflow lance to the heating circuit flow connection. Consequently, the overflow lance allows for the transfer of different flow rates from the flow connection of the lower storage tank section to the heating circuit flow connection on the one hand, and from the flow connection of the lower storage tank section into the storage chamber of the lower storage tank section on the other.

[0032] This design has the advantage that the flow temperature generated by the heat pump can always flow directly into the heating circuit flow without temperature mixing whenever the volume flow of heated heating water provided by the heat pump (i.e., the volume flow in the heat pump circuit) is greater than the volume flow in the heating circuit, which corresponds to the majority of operating conditions during the heating season. In this context, there are two operating conditions during the heating season. 1. Operating condition: the heat pump is in operation; warm flow water flows directly into the heating circuit flow, and an excess volume flow flows through the annular gap into the lower part of the storage tank. 2. Operating condition: the heat pump is not in operation; in this case, the heating circuit is supplied only with the stored heat from the lower part of the storage tank, and the heating water is supplied to the heating circuit via the annular gap of the overflow lance.

[0033] Furthermore, such a configuration of the combined hot water and heating storage tank can be advantageous in which it has a circulation connection for connection to a building circulation system, wherein the circulation connection is arranged on a connecting pipe between the upper heat exchanger and the lower heat exchanger and is hydraulically connected to both heat exchangers. For example, and preferably, the circulation connection can be arranged in the area of the intermediate insulation between the two storage parts, with the connecting pipe of the two heat exchangers extending through the intermediate insulation to hydraulically connect the two heat exchangers. The arrangement of the circulation connection has the advantage that the recirculated drinking water, which still has a relatively high temperature, can be introduced directly into the upper heat exchanger, i.e., bypassing the lower heat exchanger. In this way, an indirect exchange of heat energy between the two storage parts, which would otherwise occur through the drinking water circulating in the circulation system, is avoided. In other words, the position of the connection prevents the recirculated drinking water, which still has a fairly high temperature, from first cooling down in the lower heat exchanger due to the lower storage temperature and then from becoming hotter.

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additionally cools the upper storage area.

EXAMPLES OF EXECUTION

[0034] The invention is explained in more detail below with reference to an embodiment illustrated in the figures. It shows:

Fig. 1: Sectional drawing of the combined hot water and heating storage tank from the side,

Fig. 2: Section of the combined hot water and heating storage tank from above.

[0035] The exemplary embodiment comprises a combined hot water and heating storage tank 21. This comprises two storage parts 1, 2, namely an upper storage part 1 and a lower storage part 2. The two storage parts 1, 2 are arranged one above the other, with the upper storage part 1 being mounted on the lower storage part 2 by means of connecting feet 19. The lower storage part 2 is placed on a base by means of feet. When the hot water and heating storage tank 21 is in an operating state, both storage parts 1, 2 are filled with heating water.

[0036] The upper storage section 1 has a flow connection 9 for connecting the upper storage section 1, or its storage space, to a flow line of a heat pump (not shown in the figures). The flow connection 9 is located in an upper region of the upper storage section 1. Furthermore, the upper storage section 1 has a corresponding return connection 10, which is located in a lower region of the upper storage section 1. Heating water is circulated back to the heat pump via the return connection 10. In other words, the storage space of the upper storage section 1 is connected to a return line of the heat pump by means of the return connection 10. Similarly, the lower storage section 2 also has a flow connection 12 for a flow line of the heat pump and a return connection 13 for the return line of the heat pump.

[0037] Both storage parts 1, 2 are also each equipped with a vent 17, 18.

[0038] The lower storage section 2 supplies at least one heating circuit (for example, two heating circuits, one for radiators and one for underfloor heating) and serves to preheat the domestic hot water. It is charged by the heat pump with a low temperature level (e.g., 30°C to 50°C). The upper storage section 1 is used for heating the domestic hot water and is charged by the heat pump with higher temperatures (e.g., 50°C to 60°C).

[0039] However, unlike stratified storage tanks, which consist of a single container, the two storage sections 1 and 2 are not directly connected via the heating water, but are hydraulically separated from each other. In other words, there is no direct hydraulic connection between the storage chambers of the two storage sections 1 and 2, in which the storage sections 1 and 2 hold the heating water. Mixing of the volumes of heating water stored in the storage chambers of the storage sections 1 and 2 is thus prevented. In other words, no mixing of the water masses takes place between the hot water section (upper storage section 1) and the heating section (lower storage section 2).

[0040] An intermediate insulation 7 is installed between the storage parts 1, 2, so that the effect of heat transfer between the two storage parts 1, 2 by heat conduction is also minimized.

[0041] For heating the drinking water, a heat exchanger 3, 4 is arranged in each of the two storage sections 1, 2. The heat exchangers 3, 4 are, and preferably, at least substantially identical in construction. The heat exchangers 3, 4 are each made of stainless steel, specifically each of a stainless steel corrugated tube. In other words, the heat exchangers 3, 4 each comprise a stainless steel tube arranged in a coil. The heat exchangers 3, 4 are arranged in the storage chambers of the storage sections 1, 2 such that they are surrounded by the heating water stored therein.

[0042] The cold drinking water first flows through a cold water connection 15 into the lower

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The water enters the heat exchanger 3 of the lower storage section 2 and is preheated there as it flows through the lower heat exchanger 3. In this process, thermal energy from the heating water, which is stored in the storage space of the lower storage section 2, is transferred through a pipe wall of the heat exchanger 3 to the potable water flowing through the heat exchanger 3.

[0043] The preheated drinking water then flows through a connecting line from the lower heat exchanger 3 to the upper heat exchanger 4, which is located in the upper storage section 1. The upper heat exchanger 4 reheats the drinking water to its final temperature due to the higher temperature of the heating water in the upper storage section 1. The heated drinking water can then be drawn off at a hot water connection 8 and supplied to the taps in the respective building. The preheating in the lower storage section 2 reduces the amount of heat required for the upper storage section 1 with its higher temperatures.

[0044] Both storage components 1, 2, arranged one above the other, are protected against heat loss to the outside by means of a common external insulation 6. The footprint of the combined hot water and heating storage tank 21 is smaller than with a separate installation of two separate storage tanks, and the heat losses are also lower due to the smaller surface area.

[0045] The combined hot water and heating storage tank 21 has, in the lower storage section 2, which is used to supply the at least one heating circuit with heating water, here and preferably an overflow lance 5. This is installed in such a way that it extends through the storage space of the lower storage section 2. During heating operation, the overflow lance 5 ensures that the flow temperature of the heat pump can flow directly into a heating circuit flow connection 11 for a heating distribution system of the heating circuit via the flow connection 12 of the lower storage section 2.

[0046] The overflow lance 5 comprises an inner pipe with a smaller diameter through which the heating water flows from the heat pump via the flow connection 12 of the heat pump. Furthermore, the overflow lance 5 comprises an outer pipe which has a larger diameter compared to the inner pipe. The inner diameter of the outer pipe is preferably a few millimeters, for example 3 mm, larger than the outer diameter of the inner pipe. This creates an annular gap between the outer and inner pipes. The inner pipe is inserted a few centimeters, for example 4 cm, into the outer pipe.

[0047] If the flow rate of the heating water originating from the heat pump and supplying the lower storage section 2 with heat energy via the supply connection 12 of the lower storage section 2 is not identical to the flow rate of the heating water entering the at least one heating circuit via the heating circuit supply connection 11 and thus extracting heat energy from the lower storage section 2, the difference in flow rates can be compensated for by the open annular gap of the overflow lance 5. In most operating conditions, the flow rate originating from the heat pump is greater than the flow rate supplied to the heating circuit – for example, driven by a heating circuit pump. The temperature produced by the heat pump, that is, the portion of the heated water flow supplied by the heat pump that is drawn by the heating circuit, then flows unimpeded through the bypass lance 5 into the heating circuit supply connection 11. Any excess flow not drawn by the heating circuit flows into the upper section of the storage chamber of the lower storage tank 2, which consequently stores the excess heat energy. This results in a higher temperature reaching the heating circuit than with the conventional integration of a heating storage tank as a buffer tank. Consequently, the heat pump's supply temperature can be reduced.

[0048] In summer, i.e., outside the heating season, only the upper storage section 1 is active, which minimizes heat losses. If the heat pump has a cooling function, the cold drinking water, which also flows through the lower heat exchanger 3 of the lower storage section 2 in summer, cools the heating water in the lower storage section 2 and thus assists in

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The cooling function is naturally integrated. Even when cooling, the drinking water is preheated from approximately 10°C to 15°C, which reduces the heating requirement for hot water during the summer months.

[0049] For the return flow of the heating distribution system, the lower storage section 2 has at least one heating circuit return connection 14, 16. In the example shown, two heating circuit return connections 14, 16 are provided, which are formed at different height levels on the lower storage section 2 in order to allow for different hydraulic configurations. For example, depending on the flow rate of the heating circuit, it may also be advantageous to connect the heating circuit return not in the lower area of the lower storage section 2, but in the middle area of the storage section 2.

[0050] In the example shown, a circulation system for hot drinking water is installed in the house to which the combined hot water and heating storage tank 21 belongs. This circulation system is connected to the heat exchangers 3, 4 by means of a circulation connection 20. The circulation connection 20 is positioned here, and preferably on the connecting pipe that links the upper heat exchanger 3 and the lower heat exchanger 4. This ensures that the hot drinking water circulates only through the upper heat exchanger 4 in the upper storage section 1. This prevents the temperatures of the lower storage section 2 and the upper storage section 1 from equalizing, even with a circulation system for the drinking water present.

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REFERENCE MARK LIST

1 upper storage section

2 lower storage part

3 lower heat exchangers

4 upper heat exchanger

5 Overflow lance

6 External insulation

7 Intermediate insulation

8 Hot water connection

9 Flow connection of the upper storage section 10 Return connection of the upper storage section 11 Heating circuit flow connection

12 Flow connection of the lower storage section 13 Return connection of the lower storage section 14 Heating circuit return connection

15 Cold water connection

16 second heating circuit return connection

17. Venting of the upper storage section

18. Venting the lower part of the storage tank

19 connecting feet

20 Circulation connection

21 combined hot water and heating storage tank

Claims (3)

A hes AT 18 587 U1 2025-12-15 Ss N Claims 1. Combined hot water and heating storage tank (21) for heating domestic hot water and for heating water for heating a building in conjunction with a heat pump, comprising - a lower memory section (2), - an upper memory section (1), wherein both storage parts (1, 2) each have a storage space for storing heating water tempered by the heat pump, wherein the storage spaces of the two storage parts (1, 2) are hydraulically separated from each other, wherein the storage parts (1, 2) each have a flow connection (9, 12) for connecting the respective storage space to a flow of the heat pump and each have a return connection (10, 13) for connecting the respective storage space to a return of the heat pump, wherein the lower storage part (2) has a heating circuit flow connection (11) for connecting the storage space of the lower storage part (2) to a flow of a heating distribution system of the building and a heating circuit return connection (14, 16) for connecting the storage space of the lower storage part (2) to a return of the heating distribution system of the building, wherein the upper storage part (1) and the lower storage part (2) are arranged one above the other and connected to each other as a single structural unit, wherein a thermal intermediate insulation (7) is arranged between the two storage parts (1, 2), which thermally insulates the two storage parts (1, 2) from each other, wherein both storage parts (1, 2) are enclosed by means of a common thermal external insulation (6) which thermally insulates the two storage parts (1, 2) from the environment, wherein an upper heat exchanger (4) is arranged in the storage space of the upper storage part (1) and a lower heat exchanger (3) is arranged in the storage space of the lower storage part (2), each of which is provided and equipped for heating the drinking water, wherein the lower heat exchanger (3) has a cold water connection (15) for the supply of unheated drinking water and the upper heat exchanger (4) has a hot water connection (8) for the discharge of heated drinking water, wherein the two heat exchangers (3, 4) are hydraulically connected and connected in series, so that unheated drinking water from the cold water connection (15) can first flow through the lower heat exchanger (3) and be heated by the heating water located in the storage space of the lower storage part (2), the drinking water thus heated can then flow from the lower heat exchanger (3) into the upper heat exchanger (4), flow through this in the direction of the hot water connection (8) and be further heated by the heating water located in the storage space of the upper storage part (1) and the heated drinking water can exit the upper heat exchanger (4) at the hot water connection (8). 2. Combined hot water and heating storage tank (21) according to claim 1, characterized by an overflow lance (5) by means of which the flow connection (12) of the lower storage part (2) and the heating circuit flow connection (11) are fluidically connected to each other, wherein the overflow lance (5) extends through the storage space of the lower storage part (2), wherein the overflow lance (5) has an annular gap through which both heating water can flow into the storage space of the lower storage part (2) and heating water can flow from the storage space of the lower storage part (2) into the overflow lance (5), so that by means of the overflow lance (5) different volume flows are possible from the flow connection (12) of the lower storage part (2) to the heating circuit flow connection (11) on the one hand and from the flow connection (12) of the lower storage part (2) into the storage space of the lower storage part (2) on the other hand. 10 / 13 3. Combined hot water and heating storage tank (21) according to claim 1 or 2, characterized by a circulation connection (20) for connection to a circulation piping system of the building, wherein the circulation connection (20) is arranged on a connecting pipe between the upper heat exchanger (4) and the lower heat exchanger (3) and is hydraulically connected to both heat exchangers (3, 4). This includes 2 sheets of drawings