LOW-TEMPERATURE HEATING NETWORK

Description

[0001] The invention relates to a low-temperature heat network for supplying buildings with heat for heating and hot water according to the preamble of claim 1, a building station according to the preamble of claim 9, and a method for operating a low-temperature heat network according to the preamble of claim 10.

[0002] Such low-temperature heating networks, building stations for them and methods for operating such networks are generally known, for example from DE 197 40 398 A1.

[0003] Within the scope of this disclosure, a building to be served may contain multiple building stations, each specifically assigned to a separate building unit, such as an apartment. A building to be served could be, for example, a single-family home, an apartment building, a terraced house, or a residential building or block with multiple separately supplied apartments. Each building unit, i.e., each apartment, can be assigned its own building station, which is then also referred to as an apartment station. Within the scope of this disclosure, a building station is therefore also understood to be an apartment station if the building unit to be served is an apartment. In principle, it is also possible for one building station to serve multiple units within a building, such as multiple apartments.

[0004] Although considerable progress has been made in recent years regarding the efficient use of energy for heating buildings, including the integration of renewable energy sources, it is nevertheless evident that a significant proportion of the energy used still remains unused. When the term "heat" is used in the following text, it refers to "thermal energy."

[0005] The use of exhaust air by heat pumps for hot water preparation in a building, such as an apartment or other building unit, is generally known. The problem is that, in order to achieve an acceptable performance value (COP = Coefficient of Performance; a quality criterion for heat pumps also known as "performance factor"), such heat pumps must operate at a more or less fixed operating point. This means they cannot be regulated in the sense that the supply of exhaust air – i.e., its volume flow – cannot be increased according to demand. In practice, therefore, a considerable amount of electrical energy is supplied to the hot water storage tank (boiler) to produce a sufficient quantity of hot water when the heat pump cannot extract enough heat from the exhaust air.This disadvantage exists regardless of whether the building heating is provided by a central supply unit, located more or less far away and serving several buildings, whose operating process is based, for example, on combined heat and power (CHP), or by an individual heating system, such as a gas or pellet boiler. If the building is heated via a central supply, not only does the aforementioned demand for electrical energy for the heat pump in the building's heating system lead to an unfavorable energy balance, but significant additional losses occur, particularly due to waste heat from the operating process in the supply unit, as well as in the supply and return lines between the supply unit and the heat exchanger, due to the comparatively high temperatures of the working fluid in practice. These temperatures can reach 80 to 85°C in the supply line and approximately 50°C in the return line.Significant heat losses due to distance cannot be prevented even with comparatively good thermal insulation of the supply and return lines. The object of the invention is to avoid these disadvantages in the prior art. This object is achieved by the features of independent claims 1, 9, and 10.

[0006] The invention is therefore characterized, according to one aspect, by the fact that the building station of the heat pump not only supplies the exhaust air from the room as a primary heat source, but also the return flow from the heating circuit, so that the heat pump can additionally utilize the heat contained in the return flow from the heating circuit. Particularly during the winter months, the control unit can thus supply the return flow from the heating circuit to the heat exchanger as an additional primary heat source if the exhaust air from the room is too low in temperature or if a sufficiently large volume flow of exhaust air cannot be provided to supply the required energy with an optimal COP for domestic hot water preparation.Thanks to the invention, the control unit can regulate the operation of the heat pump depending on the respective availability and demand situation, in such a way that the contributions of the different primary heat sources room exhaust air on the one hand and heating circuit return on the other hand are varied accordingly.

[0007] A key advantage of this concept is that during the winter months, the otherwise unused heating circuit return flow can be used to support the primary side of the heat pump. This allows the heat pump to operate at its optimal operating point even with insufficient heat input from the exhaust air, thus achieving the best possible COP. In summer, on the other hand, sufficient heat is available from the outside air (and therefore ultimately from solar energy), which can be supplied to the building station via the fresh air intake from outside the building, resulting in even warmer exhaust air.

[0008] The use of the heating circuit return as an additional primary heat source for the primary-side heat exchanger of the heat pump according to the invention leads to a significantly improved energy balance already in the building station, since additional electrical energy for hot water preparation is no longer necessary or can at least be reduced to a minimum.

[0009] This concept constitutes an independent subject matter according to claim 9 (building station) and according to an aspect of claim 1 (heating network) and of claim 10 (operating method).

[0010] According to a further aspect of the invention, which is fundamentally independent of the first aspect but can be particularly advantageously combined with it, it is provided that additional heat is extracted from the return flow of the network heat exchanger in the building substation and used to heat the thermal storage tank. This allows even more energy from the network supply flow to be used for heating this storage tank. Furthermore, it makes it possible to give the network return flow between the transfer station and the distribution center a temperature that is much lower than before. While previously the network return flow typically had temperatures in the range of about 50°C, or in other known low-temperature district heating networks still around 10°C, thanks to the invention the working fluid in the network return flow can, for example, have a temperature of only about 2 to 4°C or even less.This can drastically reduce heat losses in the network return line, or – depending on the specific circumstances – even allow for heat recovery via the network return line. For example, the working fluid in the network return line, in which the pipeline for the network return is typically buried, can be warmed by the surrounding soil on its way to the supply center, increasing its temperature from an initial 2 to 4°C to approximately 8 to 9°C.

[0011] It goes without saying that this eliminates the need for thermal insulation of the network return pipe, resulting in significant cost savings. Furthermore, this allows for even greater optimization by routing the network return pipe close to the network supply pipe, so that any heat losses occurring there can be at least partially used to heat the network return pipe, which is "cooled" thanks to the invention, and thus effectively eliminate losses.

[0012] The comparatively low temperature of the network return at the supply center, achieved thanks to the invention, offers the further advantage of enabling effective heat recovery from the waste heat generated during the operational process at the supply center. This includes, for example, the waste heat from the exhaust gas of a combined heat and power (CHP) process that constitutes the operational process at the supply center. Currently, these exhaust gases have temperatures of up to 100°C, and at best, no less than 35°C. A heat exchanger allows the waste heat from the operational process to be utilized and fed into the network return. In this way, the temperature of the exhaust gases from a CHP process can be reduced to, for example, 12 to 15°C, meaning that the waste heat from the operational process at the supply center can be almost completely utilized.This in turn reduces the energy input at the supply center for heating the network supply and thus the primary energy share.

[0013] As already mentioned, this second aspect of the invention is particularly advantageous in combination with the first aspect, because by extracting heat from the building's heating circuit return, this return flow reaches the transfer station, i.e., the intermediate storage tank, at a lower temperature than before, namely at a temperature of, for example, approximately 20 to 22°C or even less, for example, approximately 15°C. This advantageously reduces the energy input for the heat pump of the transfer station, which serves to extract heat from the return flow of the network heat exchanger and additionally supply this heat to the intermediate storage tank. Furthermore, especially when the temperature of the building return flow corresponds at least approximately to the temperature of the return flow of the network heat exchanger, the latter can operate particularly efficiently, i.e., the network heat exchanger then possesses a particularly good transfer quality.

[0014] In simplified terms, the invention – with regard to the building station – is characterized by the fact that the return flow of the heating circuit is used to make hot water preparation more efficient, and – with regard to the transfer station – by the fact that the return flow of the network heat exchanger is used to make the heating of the intermediate storage tank more efficient and to achieve further advantages, in particular the associated reduction in the temperature of the network return flow, which in turn enables energy recovery on the route to the supply center and from the waste heat of the supply center, i.e., as a result, a minimization of the energy input at the supply center for heating the network supply flow.

[0015] The combination of the two aspects of the invention results in – as explained above – even more synergy effects, which make it possible to operate a low-temperature heating network with a minimum of energy input – beyond the use of renewable energy.

[0016] When, in the context of this disclosure, reference is made to a "forward" or a "return" or a "circulation" or a "storage", this refers, depending on the context, to the respective fluid working medium, in particular water, or to a conduit or container in which this working medium flows or in which this working medium is contained.

[0017] Advantageous further developments of the invention are specified in the dependent claims, the description and the drawing.

[0018] The building station according to the invention can be provided in the form of a transportable unit that can be handled as a whole and is particularly suitable for installation in the wet areas of a building unit, such as in a bathroom or toilet. The heat pump and a hot water storage tank (boiler) can be combined into a single structural and functional unit, as is already the case with currently known devices.

[0019] According to a further embodiment of the invention, an additional ventilation heat exchanger can be provided in the building station, in which heat exchange takes place between the supplied outside air and the room exhaust air and which can be operated together with the heat pump in at least two different switching configurations, wherein in a winter switching configuration the room exhaust air is supplied to the ventilation heat exchanger before entering the heat pump in order to heat the outside air, and in a summer switching configuration the room exhaust air is first supplied to the heat pump and then to the ventilation heat exchanger in order to cool the outside air.

[0020] With just one additional component to the heat pump—a standard ventilation heat exchanger—the building station can function optimally at any outside temperature, i.e., at any outside air temperature. The outside air can be either heated or cooled by the exhaust air from the building. In either case, the exhaust air passes through the heat pump's intake heat exchanger and is then discharged from the building station as energy-efficient exhaust air, ready to be released into the surrounding environment, i.e., from the building. This simultaneously enables temperature control (cooling or heating) of the outside air and ventilation of the building in which the building station is installed.

[0021] This means that an additional ventilation system is unnecessary, which is required in conventional heat pump systems to expel heated indoor air during the winter months. This is necessary because modern, highly airtight windows necessitate dehumidification through ventilation. While these conventional ventilation systems do recover heat from the warm indoor air being expelled, this process is not very efficient.

[0022] The ventilation heat exchanger and the heat pump are combined into a single unit.

[0023] Preferably, switchable valves are provided to allow switching between different circuit configurations. These valves can be controlled via the building station's control unit.

[0024] In an advantageous embodiment of the invention, the exhaust air from the room is not only extracted in the building station, but is simultaneously dehumidified by means of the primary-side heat exchanger of the heat pump. The cooler and drier exhaust air leaving the primary-side heat exchanger of the heat pump can then be released from the building as exhaust air. This occurs in winter. In summer, however, according to a further possible embodiment of the invention, as already explained above, this exhaust air, cooled by the primary-side heat exchanger of the heat pump, can be used to cool warmer fresh air (outside air) drawn in from outside the building by means of a downstream air-to-air heat exchanger. In this way, advantageous room temperature control can be achieved in summer.Cooling requirements and available solar energy, the latter in the form of warm outside air usable by the heat pump, thus coincide advantageously. Consequently, hot water can be produced without additional heat sources, in particular without additional energy from a central supply unit.

[0025] According to further possible embodiments of the invention, at least one conduit intended for a fluid working medium, in particular water, and especially a conduit for the network supply, the network return, the building supply, and / or the building return, can simultaneously be designed as an electrical conductor or as a carrier for an electrical conductor for the transmission of electrical energy. In this case, heat losses due to electrical resistance can be used to heat the working medium flowing in the conduit. This utilization of otherwise wasted heat represents a further possible synergistic effect of the invention.

[0026] As described in more detail elsewhere, the transfer station can additionally be equipped with at least one electrical storage unit that can be powered by electrical energy from an external source, e.g., a photovoltaic system or the central power supply. This electrical storage unit can supply the transfer station and / or the building substation, or several building substations connected to the transfer station, with electrical energy, particularly during nighttime hours. The aforementioned supply lines E and J and / or return lines F and K can be used for the electrical connection of this electrical storage unit, provided they are appropriately configured.

[0027] According to further possible embodiments of the invention, it can be provided that in the building station a further heat exchanger is assigned to the hot water storage tank, which can be connected via the control unit to the building supply and / or to the heating circuit supply in order to provide heat from the hot water storage tank to the building supply or the heating circuit supply and / or heat from the building supply to the hot water storage tank depending on the respective availability and demand situation.

[0028] These interconnection and control options allow, particularly during the transitional periods between summer and winter, when sufficient solar energy is available to supply heat to the hot water storage tank via the building's heat pump, but heating is still required, the building can be heated at least partially using solar energy, i.e., via the hot water storage tank, without experiencing a shortage of hot water. It is also possible to transfer heat from the hot water storage tank, heated by solar energy and the building's heat pump, and the control unit to the intermediate storage tank of the heat exchanger.

[0029] Furthermore, according to the invention, it is preferably provided that a control unit is provided in the transfer station, via which the building supply and the building return are connected to the thermal intermediate storage and which is designed to control the operation of the heat network - at least with regard to the transfer station and the building station or each building station connected to this transfer station - depending on the respective availability and demand situation.

[0030] Both control units can be considered a single overall control system for the respective building station, which essentially records, monitors, controls and regulates everything relevant to the desired heat supply of the building to which the building station belongs.

[0031] In particular, the interplay of the devices and controls disclosed herein, as illustrated in more detail in the figures below, enables a highly efficient heat supply for buildings or building units, such as apartments, primarily powered by solar energy. It should also be emphasized that excess solar energy generated during the day can be stored both in the electrical buffer tank and – for each connected building station via the arrangement of heat pump, hot water storage tank, and building supply line – in the thermal buffer tank.

[0032] The possible further developments of the building station or the described facilities present in the building station described in connection with the heating network according to the invention are hereby also disclosed as further developments of the building station according to the invention or its respective facilities and - if they concern aspects relevant to control or requiring or enabling control - also as further developments of the method according to the invention.

[0033] The invention is described below by way of example with reference to the drawing. The drawing shows: Fig. 1 a schematic overview of a low-temperature heating network according to the invention, Fig. 2 schematically further details of a low-temperature heating network according to the invention, Fig. 2 the apartment station (building station) of Fig. 2 in an enlarged view, Fig. 2b the transfer station of Fig. 2in an enlarged view, and Fig. 2c further details of the building station of Fig. 2 .

[0034] As already mentioned at the outset, the low-temperature heat network according to the invention comprises one or more building stations 1 (which are also referred to here as apartment stations), a supply center 3, which is assigned to a plurality of building stations 1, and a transfer station 2 between each building station 1 and the supply center 3.

[0035] The invention relates to both a building station 1 and a low-temperature heating network, which, in addition to one or more building stations 1 according to the invention, comprises at least one transfer station 2 and at least one supply center 3.

[0036] The building station 1 according to the invention, which is installed, for example, in the form of a transportable device in a bathroom or toilet of an apartment (hereinafter simply: building), is supplied with exhaust air A, which is drawn from the building and leaves the building station 1 as energy-used exhaust air B. Details of this will be discussed elsewhere. The building station 1 serves to supply hot water C to the building and to supply a heating circuit D of the building via a control unit SE ( Fig. 2a ), wherein the heating circuit D comprises a heating circuit flow DVL and a heating circuit return DRL.

[0037] The building station is connected to the transfer station 2 via the building supply line E and the building return line F.

[0038] Transfer station 2 is connected to supply center 3 via the network supply line J and the network return line K. The small arrows on the network supply line J indicate that heat losses to the surrounding soil occur along the respective supply line. The small arrows pointing in the opposite direction towards the return line K indicate that, due to the low temperature of the working fluid in network return K (as explained earlier), this working fluid can absorb heat from the surrounding soil, which may originate at least partially from the heat emitted (i.e., the heat loss) of the network supply line J.

[0039] For transfer station 2, solar energy H can be used directly or indirectly, for example, by means of a photovoltaic system (PV). For this purpose, transfer station 2 is equipped with an electrical storage unit (not shown), namely a battery, which can be charged by the photovoltaic system (PV) and thus by solar energy. Alternatively or additionally, the electrical storage unit of transfer station 2 can also be supplied with electricity from the central power supply unit 3. The electrical storage unit serves to supply the equipment in building station 1 and in transfer station 2, particularly during the night. As mentioned elsewhere, the lines for the individual supply lines E and J and / or return lines F and K can be used for the electrical connection of this electrical storage unit.

[0040] The supply of electrical energy I to transfer station 2 from supply center 3 and the supply of electrical energy G to building station 1 by transfer station 2 can – as already explained above – be carried out via the lines of the respective supply line J or E and / or return line K or F. Separate electrical lines can then be omitted, which in Fig. 2 and accordingly also in the Fig. 2a and 2b as indicated by the dashed lines at H and I.

[0041] How Fig. 2aAs shown, the control unit SE, which is connected to the building supply E and the building return F, serves to distribute and adjust, and thus influence, the individual working fluid flows, particularly with the aid of appropriate valve actuators. The heating circuit supply DVL and the heating circuit return DRL are also connected to the control unit SE. According to the invention, the primary side of the heat pump WP1 can be supplied not only with the room exhaust air A, but also with the heating circuit return DRL via the control unit SE. This occurs via a further refrigerant-to-water heat exchanger WT2, which is connected to the primary side of the heat pump WP1 and in series with the air-to-refrigerant heat exchanger WT1 for the room exhaust air A. The control unit SE can supply the heating circuit return DRL to this heat exchanger in a demand-based manner.This allows two different primary heat sources to be supplied to the primary circuit of the heat pump WP1, namely the room exhaust air A and the heating circuit return DRL.

[0042] The discharge heat exchanger WT3 of the heat pump WP1 heats the working medium, in particular water, in the hot water storage tank WW for the building's hot water supply C via its working medium (refrigerant). The control unit SE can also supply heat to the hot water storage tank WW via an additional heat exchanger WT4, if necessary. For information on the possible integration and use of this additional heat exchanger WT4, please refer to the corresponding explanations in the introduction.

[0043] With the exception of the additional supply of heat from the heating circuit return DRL to the primary side of the heat pump WP1 according to the invention - here via the additional primary-side heat exchanger WT2 - this construction of a building station 1 is basically known.

[0044] Regarding further details and, in particular, possible temperatures or temperature ranges of the individual circuits or supply and return lines, reference is also made to the rest of this disclosure, including the labels in the figures. This also applies to the explanations relating to transfer station 2 and supply center 3.

[0045] In Fig. 2 and 2a Two ventilation heat exchangers WTP are shown in the illustrations. In fact, only a single such ventilation heat exchanger WTP, namely an air-to-air heat exchanger, is provided, as will be explained below in conjunction with Fig. 2c will be discussed in more detail. The simplified representation in this regard is presented in Fig. 2 and 2a The two ventilation heat exchangers WTP are only intended to illustrate two possible, different circuit configurations that can be implemented with the one ventilation heat exchanger WTP and the heat pump WP1.

[0046] Fig. 2c The diagram illustrates the arrangement of the ventilation heat exchanger WTP and the heat exchanger WT1 of the heat pump WP1 in two different circuit configurations, which will be briefly explained below. For the sake of simplicity, the respective air or component will be indicated below only by its reference symbol (A = room exhaust air, etc., see list of reference symbols). Whether a line is shown as a dashed line or not is irrelevant here.

[0047] The path from "M" to "N" via the secondary side of the WTP is and always remains the same. This always involves fresh outside air M, which is either heated (winter) or cooled (summer) in the WTP and then supplied to the rooms as supply air N.

[0048] In contrast, "A" is always the "used" (CO2 and moisture-containing, i.e., correspondingly enriched) room exhaust air, which, in principle, regardless of how it is redirected by the valves V1 - V3, always leaves this "structure" as room (building) exhaust air (used air) via "B".

[0049] The room exhaust air "A" is also always routed through the WT1 of the WP1. "Basic setting" = Winter operation:

[0050] Air "A" is conveyed upwards via V1 to the primary side of the WTP (heat transfer pump) and warms the colder outside air "M" there via heat exchange. Cooled by this energy factor, "A" leaves the WTP and is fed via V3 to WT1 of WP1 (heat pump). "A" finally leaves WT1 cooled and dehumidified, passes through V2 on a direct path to the outside, and becomes exhaust air "B". Summer operation:

[0051] "A" passes through V1 again, which has been switched and now carries "A" (diverted downwards) via a line to V3, which has also been switched and now has two paths open: "6 o'clock" (bottom) and "3 o'clock" (right), as well as "9 o'clock" (left) and "12 o'clock" (top). Thus, "A" now enters the WT1 of WP1 directly, is cooled there, and leaves WT1 via V2, which has also switched and now carries "A" via the further line to the WTP. In the WTP, the cooled "A" is used via its primary side and the heat exchange process to cool the now (in summer) warmer outside air "M". "A", having absorbed heat, leaves the WTP thus warmed and passes through V3 and the "9 o'clock" (left) and "12 o'clock" (top) paths on its way to "B", and is thus released as exhaust air "B" from the building station and therefore from the building.

[0052] Air dehumidification always takes place in the WT1 of the WP1, in both circuit configurations, with the outside air M also being dehumidified in the WTP during the summer.

[0053] The flow paths described above can be summarized as follows: Summer:

[0054] A (warm) -> V3 -> WT1 (cooling and dehumidification there) -> V2 -> WTP (there (i) absorption of heat from M and (ii) dehumidification) -> 1V3 -> B (as cooled and dehumidified room exhaust air from the building).

[0055] M (warm) -> WTP (where heat is released and dehumidified) -> N (= cooled fresh air; "room temperature control"). Winter:

[0056] A (warm) -> WTP (cooling there by preheating M) -> V3 -> WT1 (cooling and dehumidification there) -> B (as cooled and dehumidified room exhaust air from the building).

[0057] M (cold) -> WTP (where preheating is carried out by A) -> N (= preheated fresh air).

[0058] Another advantage of this configuration is that the air "A" is always slightly cooler after leaving the WTP (despite the heat absorbed from the outside air in the WTP) due to its design and the way the air is guided at the same switching flap of the V3 by the air mass flow and thus the cooling on the aforementioned valve switching flap of the V3, heat can be extracted from the still slightly warmer room exhaust air "A" flowing past it on the other side, which benefits the cooling capacity of the WT1 and WP1, because this cooling capacity has "natural" physical limits.

[0059] Also the transfer station 2 according to Fig. 2bis known with regard to its basic structure. The network supply J heats the intermediate storage ZS via the network heat exchanger WT7, which together with the building return F and the building supply E forms a building circuit that is hydraulically separated from the supply or network circuit, which in addition to the network supply J and the network heat exchanger WT7 includes the network return K, to which the return L of the network heat exchanger WT7 leads.

[0060] According to the invention, the return flow L of the network heat exchanger WT7 is additionally used to heat an intermediate storage tank ZS via a further heat pump WP2. The return flow L of the network heat exchanger WT7 is fed to the primary-side heat exchanger WT5 of this heat pump WP2 in order to heat the intermediate storage tank ZS by means of the output-side heat exchanger WT6 of the heat pump WP2. The medium of the intermediate storage tank ZS, and thus of the building circuit, is also referred to as building system water, which – as mentioned – is hydraulically separated from the supply or network system water (i.e., from the network circuit with network supply J, network heat exchanger WT7, and network return K) in a generally known manner.

[0061] The primary-side heat exchanger WT5 of the heat pump WP2 extracts further heat from the return flow L of the network heat exchanger WT7, resulting in the network return flow K having the aforementioned low temperature of, for example, 2 to 4°C. This yields the further advantages already mentioned elsewhere.

[0062] During operation of this low-temperature district heating network, the working fluid of the network circuit is fed via the network supply line J to a management, supply, or control unit SE located in the transfer station 2. This unit decides which level (middle level or upper level) of the network heat exchanger WT7 the high-temperature medium is fed to in order to transfer the heat to the intermediate storage tank ZS. In a possible operating situation, the lowest temperature level of the working fluid at the outlet of the network heat exchanger WT7, i.e., at its return line L, is approximately at the same temperature level as the working fluid of the building's return line F.Through the so-called recuperator in the form of the primary-side heat exchanger WT5 of the heat pump WP2 and the delivery heat exchanger WT6, further heat is extracted from the network working medium, so that the network return K has a temperature of about 2 to 4°C (and thus a receptive temperature level for extracting heat from environmental influences (e.g. from the surrounding ground)) and the extracted heat is supplied to the intermediate storage ZS via the heat exchanger WT6.

[0063] As mentioned elsewhere, transfer station 2 is also equipped with a control unit SE, to which the building supply E and the building return F with the thermal intermediate storage ZS are connected and which is designed, together with the control unit SE of building station 1 and the control unit SE to which the network supply J leads, to control the operation of the heat network - at least with regard to transfer station 2 and the or each connected building station 1 - depending on the respective availability and demand situation.

[0064] Regarding the building's heating circuit, which is separate from the mains circuit and uses the working fluid heated in the intermediate storage tank ZS and supplied to the building's control unit SE via the building's supply line E, the control unit SE is responsible for domestic hot water preparation in the hot water storage tank (WW) and for heating the building via heating circuit D. The heating circuit return flow DRL is metered by the control unit SE and routed through the additional heat exchanger WT2 on the primary side of the heat pump WP1. The working fluid circuit there – comprising heat exchanger WT1 for the room exhaust air A, the additional heat exchanger WT2, the heat pump WP1, and its delivery heat exchanger WT3 – is appropriately metered to include a portion of heat from the heating circuit return flow DRL, which is necessary for the operation of the heat pump WP1 at its optimal operating point with the best possible COP.

[0065] In Fig. 2a , 2b and 2c- and thus also in Fig. 2 - is indicated by an area enclosed by a dashed line, which has been added by the invention to a fundamentally known structure of a building station or a transfer station in order to achieve the advantages and synergy effects explained above, which are summarized again below.

[0066] The particular advantage of the low-temperature heat network according to the invention - when considered as a whole - lies in the use and bundling of a number of individual advantages and synergy effects, namely as follows: Supply center

[0067] In the supply center 3, a significantly higher proportion of usable primary energy is achieved compared to the prior art. The primary energy used is fully utilized there. Furthermore, the supply center 3 can simultaneously generate both the electricity required for operating the heating network and the supply heat, advantageously enabling demand-based generation. Ultimately, this completely eliminates the losses incurred during conventional power generation. Moreover, thanks to the "cold" network return K, the energy loss that would otherwise escape with the waste heat (exhaust gases from the work process) of the supply center 3 can be almost completely transferred to the working medium in the network return K and the network supply J. Consequently, the supply center 3 according to the invention is characterized by the following features: Energy generation exclusively on demand. Simultaneous generation of electricity and heat. Complete utilization of waste heat. The proportions of "electricity generation" and "heat generation" can be regulated independently of each other depending on the respective demand. This results in an overall almost complete and therefore highly efficient use of primary energy. Working medium lines (pipes) as electrical conductors

[0068] The lines supplying the fluid working media to building stations 1 can – as mentioned elsewhere – simultaneously serve as electrical conductors for powering these stations. Consequently, additional power lines are unnecessary. This means that line losses due to electrical resistance are not entirely lost but can be transferred to the fluid working medium as heat due to its low operating temperature. The pipes carrying the working media have a comparatively large cross-section. This allows for a direct power supply with a safety voltage and, in particular, with relatively high currents. This avoids conversion losses and eliminates the need for complex safety devices. Priority use of solar energy

[0069] In general, the low-temperature heating network according to the invention enables the direct and priority use of solar energy. Firstly, solar energy can be used directly as operating current and as charging current for the electrical buffer storage unit in the transfer station 2 via photovoltaics. This electrical buffer storage unit is therefore also referred to as the operating current buffer storage unit. Thanks to the system-related, consistently optimal operating point of the heat pumps WP1 used in the individual building stations 1, it is possible to operate them efficiently with a comparatively low solar operating current and at an optimally usable temperature level. Excess solar energy generated during the day can be stored in the transfer station 2 both as electricity, namely in the electrical buffer storage unit, and as heat, namely in the thermal buffer storage unit ZS.Any surplus solar energy can be distributed via the existing grid and / or stored elsewhere. These existing storage options mean that the solar energy supply can be "stretched" over a longer period, so that ultimately, the heat supply can be provided primarily from solar energy in a CO2-neutral manner. Thanks to the electricity generated by the photovoltaic (PV) system, the combination of heat pump and ventilation heat exchanger, explained in more detail elsewhere, allows for simultaneous air cooling and hot water production during the summer months without requiring additional primary energy. One device - many functions

[0070] In buildings or building units (e.g., apartments), several functions previously requiring multiple different devices can be performed with a single unit (building station 1), namely the combination of heat pump and ventilation heat exchanger described in more detail elsewhere. These functions include ventilation, energy recuperation, cooling, hot water preparation, and heating energy supply. The invention thus eliminates the need for additional equipment. Furthermore, ventilation and cooling result in no energy losses. It is particularly noteworthy that no additional primary energy is required for cooling (room temperature control). District heating network with minimal losses

[0071] In general, the low-temperature heating network according to the invention is characterized, among other things, by the fact that energy losses are minimized and existing heat can be used to its maximum extent and even partially recovered, in particular by means of the "cold" network return K, which is able to absorb heat from the surrounding ground. The network return K is therefore completely loss-free.

[0072] As mentioned elsewhere, this eliminates the need to insulate the return line K. Only the supply line J needs to be insulated. This alone represents a 50% cost reduction in terms of the effort required for insulating the lines.

[0073] A minimization of energy loss also results, among other things, from the fact that, according to the invention, significantly lower flow temperatures (especially significantly less than 50°C) are used compared to conventional heating networks.

[0074] Thanks to the "cold" network return K, the spectrum of use of renewable energy, solar energy and waste energy is greatly expanded. transfer station

[0075] As regards the transfer station 2, it simultaneously serves as a hydraulic separation device, a means of preventing energy loss, and a recuperator. Through the heat exchanger WT5 with unit WP2 provided in the transfer station 2 according to the invention, the transfer station 2 actively prevents the loss of thermal energy from the connected buildings via the district heating network. Furthermore, the transfer station 2 forms the heat circuit for the respective building to be supplied, while simultaneously – especially on the return side – a hydraulic-thermal separation from the district heating network takes place, so that the heat circuit of the building in question remains loss-free relative to the district heating network.

[0076] Furthermore, the inventive design of the transfer station 2 enables it to be used as a thermal intermediate storage unit (ZS). Additionally, the transfer station 2 allows for the arrangement and connection of an electrical intermediate storage unit.

[0077] The use of the heat pump WP2 in the transfer station 2 makes it possible to extract heat from the return flow of the heating network, i.e. from the return flow L of the network heat exchanger WT7, in order to bring heat back into the heating circuit of the building in question through this recuperation. Method of using solar energy

[0078] According to the invention, solar energy is used by the photovoltaic system (PV) and – during the summer months – by the warm outside air. This concept has a decisive advantage over other concepts that attempt to collect as much solar energy as possible using thermal solar collectors, since thermal solar collectors cannot be dimensioned large enough with reasonable effort to utilize the theoretically infinite reservoir of available solar energy.In contrast, the outside air heated by solar energy is available in unlimited quantities and can be used as an inexhaustible reservoir as needed by the use of heat pumps WP1 in the building stations 1, provided that - and this is ensured by the invention - the heat pumps WP1 can always be operated at the optimal operating point with the best possible COP and no additional primary energy is required for the operation of the heat pumps WP1, the latter being ensured by the use of electricity generated from solar energy via the photovoltaic system PV.

[0079] And thanks to the aforementioned operating point of WP1, which is always kept within the optimal range, even with appropriately sized photovoltaic (PV) systems, diffuse solar radiation is sufficient to provide the necessary minimum operating current. This significantly expands the usable range for the solar energy component compared to known configurations of this type. Reference symbol list

[0080] 1 Building station 2 Transfer station 3 Supply center A Room exhaust air B Building exhaust air M Outside air N Room supply air (fresh air) C Hot water supply D Heating circuit DVL Heating circuit flow DRL Heating circuit return E Building flow F Building return G Electrical energy HS Solar energy I Electrical energy J Grid flow K Grid return L Return of grid heat exchanger SE Control unit WW Hot water storage tank WP1 Heat pump of the building station WTP Ventilation heat exchanger of the building station WP2 Heat pump of the transfer station WT1 Heat exchanger WT2 Heat exchanger WT3 Heat exchanger WT4 Heat exchanger WT5 Heat exchanger WT6 Heat exchanger WT7 Grid heat exchanger PV Photovoltaic system ZS Intermediate storage tank V1 Valve V2 Valve V3 valve

Claims

1. A low-temperature heating network for supplying buildings with heat for heating and for hot water, comprising - a supply center (3); - at least one building station (1) which can be installed in a building to be supplied, - a transfer station (2) between the supply center (3) and the building station (1), - a network feed (J) extending from the supply center (3) to the transfer station (2) and a network return (K) extending from the transfer station (2) to the supply center (3), wherein, in the supply center (3), the network return (K) is heated by a working process, in particular by a combined heat and power process, and is provided as the network feed (J) for the transfer station (2), and - a building feed (E) extending from the transfer station (2) to the building station (1) and a building return (F) extending from the building station (1) to the transfer station (2), wherein the transfer station (2) comprises a thermal temporary store (ZS), to which the building feed (E) and the building return (F) are connected, and a network heat exchanger (WT7), to which the network feed (J) is connected at the input side and whose return (L) leads to the network return (K) and via which heat can be discharged from the network feed (J) to the temporary store (ZS) for the building feed (E), wherein the building station (1) comprises - a control unit (SE) which is connected to the building feed (E) and the building return (F) and which is connected to a heating circuit feed (DVL) and a heating circuit return (DRL) of a heating circuit (D) of the building, - a hot water tank (WW) for supplying the building with hot water, and - a heat pump (WP1) which comprises a primary side having a receiving heat exchanger (WT1), to which room exhaust air (A) from the building can be fed as a primary heat source, and a discharge side having a discharging heat exchanger (WT3) via which heat extracted from the room exhaust air (A) can be discharged to the hot water tank (WW), characterized in that, - in the building station (1), the heating circuit return (DRL) of the heating circuit (D) of the building is connected to the primary side of the heat pump (WP1) to extract heat from the heating circuit return (DRL) and to feed this heat to the primary side of the heat pump (WP1) in addition to the room exhaust air (A) as a further primary heat source, and / or - in that the transfer station (2) comprises a heat pump (WP2) which comprises a primary side having a receiving heat exchanger (WT5), which is connected between the return (L) of the network heat exchanger (WT7) and the network return (K), and a discharge side having a discharging heat exchanger (WT6) via which the heat extracted from the return (L) of the network heat exchanger (WT7) can additionally be discharged to the temporary store (ZS).

2. A heating network according to claim 1, wherein, in the building station (1), the heating circuit return (DRL) of the heating circuit (D) of the building is connected to the primary side of the heat pump (WP1) via the control unit (SE), and / or wherein, in the building station (1), the heating circuit return (DRL) is connected to the receiving heat exchanger (WT1) for the room exhaust air (A) and / or to a further receiving heat exchanger (WT2) of the primary side of the heat pump (WP1), in particular wherein the further receiving heat exchanger (WT2) is connected in series with the receiving heat exchanger (WT1) for the room exhaust air (A).

3. A heating network according to claim 1 or 2, wherein the control unit (SE) of the building station (1) is configured to control the operation of the heat pump (WP1), in particular wherein the control of the operation of the heat pump (WP1) includes varying the contributions of the different primary heat sources room exhaust air (A), on the one hand, and heating circuit return (DRL), on the other hand, for heating the hot water tank (WW) in dependence on the respective availability and demand situation.

4. A heating network according to any one of the preceding claims, wherein, in the building station (1), an additional ventilating heat exchanger (WTP) is provided, at which a heat exchange between the fed outside air (M) and the room exhaust air (A) takes place and which can be operated together with the heat pump (WP1) in at least two different switching configurations, wherein, in a winter switching configuration, the room exhaust air (A) is fed to the ventilating heat exchanger (WTP) before entering the heat pump (WP1) to heat the outside air (M) and, in a summer switching configuration, the room exhaust air (A) is first fed to the heat pump (WP1) and then to the ventilating heat exchanger (WTP) to cool the outside air (M).

5. A heating network according to any one of the preceding claims, wherein the building station (1) is furthermore configured to dehumidify the room exhaust air (A) fed to the heat pump (WP1) and to discharge it from the building as building exhaust air (B) from which heat has been extracted by the primary heat exchanger (WT1) of the heat pump (WP1) and which has furthermore been dehumidified, and / or wherein, in the supply center (3), in addition to the heat from the working process, waste heat produced during this working process is fed to the network return (K), in particular waste heat obtained from the exhaust gas of a combined heat and power process forming the working process.

6. A heating network according to any one of the preceding claims, wherein at least one line provided for a fluid working medium, in particular water, in particular a line for the network feed (J), for the network return (K), for the building feed (E) and / or for the building return (F), is simultaneously configured as an electrical conductor or as a carrier for an electrical conductor for transmitting electrical energy.

7. A heating network according to any one of the preceding claims, wherein, in the building station (1), the hot water tank (WW) is assigned a further heat exchanger (WT4) which can be connected to the building feed (E) and / or to the heating circuit feed (DVL) via the control unit (SE) to provide heat from the hot water tank (WW) to the building feed (E) or the heating circuit feed (DVL) and / or heat from the building feed (E) to the hot water tank (WW) in dependence on the respective availability and demand situation.

8. A heating network according to any one of the preceding claims, wherein an electrical temporary store is additionally provided in the transfer station (2), in particular wherein the electrical temporary store can be supplied with electrical energy by means of a photovoltaic system and / or by the supply center (3), and / or wherein, in the transfer station (2), a control unit (SE) is provided via which the building feed (E) and the building return (F) are connected to the thermal temporary store (ZS) and which is configured, together with the control unit (SE) of the building station (1), to control the operation of the heating network in dependence on the respective availability and demand situation.

9. A building station (1) for supplying buildings with heat for heating and for hot water, in particular for a low-temperature heating network according to any one of the preceding claims, - wherein the building station (1) can be installed in a building to be supplied and can be connected via a building feed (E) and a building return (F) to a supply belonging to the building or to an external supply assigned to the building, and - wherein the building station (1) comprises - a control unit (SE) which can be connected to the building feed (E) and the building return (F) and which can be connected to a heating circuit feed (DVL) and a heating circuit return (DRL) of a heating circuit (D) of the building, - a hot water tank (WW) for supplying the building with hot water, and - a heat pump (WP1) which comprises a primary side having a receiving heat exchanger (WT1), to which room exhaust air (A) from the building can be fed as a primary heat source, and a discharge side having a discharging heat exchanger (WT3) via which heat extracted from the room exhaust air (A) can be discharged to the hot water tank (WW), and wherein, in the building station (1), the heating circuit return (DRL) of the heating circuit (D) of the building is connected to the primary side of the heat pump (WP1) to extract heat from the heating circuit return (DRL) and to supply this heat to the primary side of the heat pump (WP1) in addition to the room exhaust air (A) as a further primary heat source, characterized in that the primary side of the heat pump (WP1) has a further receiving heat exchanger (WT2) to which the heating circuit return (DRL) of the heating circuit (D) of the building can be connected via the control unit (SE).

10. A method for operating a low-temperature heating network for supplying buildings with heat for heating and for hot water, wherein the heating network comprises - a supply center (3); - at least one building station (1) which can be installed in a building to be supplied, - a transfer station (2) between the supply center (3) and the building station (1), - a network feed (J) extending from the supply center (3) to the transfer station (2) and a network return (K) extending from the transfer station (2) to the supply center (3), wherein, in the supply center (3), the network return (K) is heated by a working process, in particular by a combined heat and power process, and is provided as the network feed (J) for the transfer station (2), and - a building feed (E) extending from the transfer station (2) to the building station (1) and a building return (F) extending from the building station (1) to the transfer station (2), wherein the transfer station (2) comprises a thermal temporary store (ZS), to which the building feed (E) and the building return (F) are connected, and a network heat exchanger (WT7), to which the network feed (J) is connected at the input side and whose return (L) leads to the network return (K) and via which heat can be discharged from the network feed (J) to the temporary store (ZS) for the building feed (E), and wherein the building station (1) comprises - a control unit (SE) which is connected to the building feed (E) and the building return (F) and which is connected to a heating circuit feed (DVL) and a heating circuit return (DRL) of a heating circuit (D) of the building, - a hot water tank (WW) for supplying the building with hot water, and - a heat pump (WP1) which comprises a primary side having a receiving heat exchanger (WT1), to which room exhaust air (A) from the building can be fed as a primary heat source, and a discharge side having a discharging heat exchanger (WT3) via which heat extracted from the room exhaust air (A) can be discharged to the hot water tank (WW), wherein the method is characterized in that - heat is extracted from the heating circuit return (DRL) and this heat is fed to the primary side of the heat pump (WP1) as a further primary heat source in addition to the room exhaust air (A), and / or - heat is extracted from the return (L) of the network heat exchanger (WT7) and this heat is made available to the temporary store (ZS) of the transfer station (2) in addition to the heat from the network feed (J).

11. A method according to claim 10, wherein the heat is extracted from the return (L) of the network heat exchanger (WT7) by means of a heat pump (WP2) of the transfer station (2).

12. A method according to claim 10 or 11, wherein the operation of the heat pump (WP1) is controlled by the control unit (SE) of the building station (1), in particular wherein, in the control of the operation of the heat pump (WP1) by the control unit (SE), the contributions of the different primary heat sources room exhaust air (A), on the one hand, and heating circuit return (DRL), on the other hand, for heating the hot water tank (WW) are varied in dependence on the respective availability and demand situation.

13. A method according to any one of the claims 10 to 12, wherein, in the building station (1), an additional ventilating heat exchanger (WTP) is provided with which a heat exchange between the fed outside air (M) and the room exhaust air (A) is performed, wherein the ventilating heat exchanger (WTP) and the heat pump (WP1) are operated in at least two different switching configurations in dependence on the temperature of the outside air (M), wherein, in a winter switching configuration, the room exhaust air (A) is fed to the ventilating heat exchanger (WTP) before entering the heat pump (WP1) to heat the outside air (M) and, in a summer switching configuration, the room exhaust air (A) is first fed to the heat pump (WP1) and then to the ventilating heat exchanger (WTP) to cool the outside air (M).

14. A method according to any one of the claims 10 to 13, wherein the room exhaust air (A) fed to the heat pump (WP1) is dehumidified in the building station (1) and is discharged from the building as building exhaust air (B) from which heat has been extracted by the primary heat exchanger (WT1) of the heat pump (WP1) and which has furthermore been dehumidified.

15. A method according to any one of the claims 10 to 14, wherein, by extracting heat from the return (L) of the network heat exchanger (WT7), the temperature of the network return (K) is reduced to such an extent that the network return (K) can heat up on the route from the transfer station (2) to the supply center (3) due to environmental influences, and / or wherein, in the supply center (3), in addition to the heat from the working process, waste heat produced during this working process is fed to the network return (K), in particular waste heat obtained from the exhaust gas of a combined heat and power process forming the working process.