Defrost control and heat pump network

Abstract

The invention relates to a defrost control (48) of a heat pump system (12) with several cascaded heat pumps (14), comprising the steps of providing (50) the heat pump system (12), detecting (52) a defrosting requirement (54) at at least one first heat pump outdoor unit (20) of a first heat pump (16) of the heat pump system (12), initiating (68) a defrosting process at at least the first heat pump outdoor unit (20) by supplying heat energy to the first heat pump outdoor unit (20) depending on the detected defrosting requirement, wherein during the defrosting process the required heat energy is directly provided by at least one other second heat pump (18) of the heat pump system (12) and transferred to the first heat pump outdoor unit (20), wherein the initiation (68) of the defrosting process at the first heat pump outdoor unit (20) only takes place if no other start criterion (70) is present. Heat pump outdoor unit (23,24) of the other heat pumps (14) of the heat pump system (12) simultaneously performs a defrosting process. The invention further relates to a heat pump system (12).

Description

The invention relates to a defrost control system according to the preamble of claim 1. Furthermore, the invention relates to a heat pump system. State of the art In a heat pump system, several heat pumps can be cascaded together to cover higher heating energy demands. A critical factor influencing the performance and reliability of heat pumps is icing, especially when using air as the heat source. Icing occurs when the temperature at the evaporator of the heat pump's outdoor unit falls below the dew point of the ambient air, and this temperature is below freezing. In this case, moisture from the air condenses on the evaporator and freezes. This leads to a reduction in the heat transfer coefficient and increases the flow resistance at the heat exchanger. The resulting drop in performance can impair the efficiency and operational reliability of the heat pump system. Disclosure of the invention According to the present invention, a defrost control system with the features of claim 1 is proposed. This allows defrosting in the heat pump system to be carried out more efficiently and in a more controlled manner. The heat required for defrosting the heat pump system can be reduced. The heat pumps in the heat pump network can be connected in series and / or parallel. The heat pumps in the heat pump network can be identical, in particular having the same nominal heating capacity. The heat pump system can be used for heating and optionally also for cooling at least one building, in particular an apartment building or an office or industrial building. At least one heat pump in the heat pump network can be an air-to-water heat pump, specifically using outside air as a heat source. Most, in fact all, heat pumps can be air-to-water heat pumps. At least one heat pump, in particular the first heat pump, can have a closed refrigerant circuit in the first outdoor unit as a monobloc configuration. At least one heat pump, in particular the first heat pump, can have a split configuration with a first indoor unit connected to the first outdoor unit by a refrigerant circuit. At least one outdoor heat pump unit, in particular the first outdoor heat pump unit, may have at least one heat exchanger for exchanging thermal energy between a refrigerant from a refrigerant circuit of the first outdoor heat pump unit and the ambient air. At least one outdoor heat pump unit may have an evaporator for absorbing thermal energy from the ambient air. The heat pump system can comprise exactly two or more than two heat pumps. The heat pumps are interconnected via a fluid transfer system through cascading connections. The second heat pump can have a second outdoor unit. At least one other heat pump in the system can have another outdoor unit. All heat pumps in the system can each have one outdoor unit. The defrosting process is carried out, in particular, to defrost at least one heat exchanger, especially an air-to-refrigerant heat exchanger, of the first outdoor unit of the heat pump. The heat exchanger can ice up at low air temperatures around it and when there is an increased heating demand at the first heat pump. During the defrosting process, the thermal energy required for defrosting the first outdoor unit can be supplied directly adjacent to the second heat pump by at least one other heat pump in the heat pump system. The heat pumps in the heat pump network can each output a status parameter indicating whether a defrost cycle is in progress. This status parameter can be binary, specifically 1 for no defrost cycle and 0 for a defrost cycle in progress on the respective heat pump. Determining the defrosting requirement and / or controlling the defrosting process can be carried out by at least one defrost control unit to which the heat pumps are connected. The defrost control unit can be assigned to a control unit for managing the operation of the heat pumps. The control unit can be a central control unit or that of a master heat pump in the heat pump network, which controls the other heat pumps in the network as slave heat pumps. In a preferred embodiment of the invention, it is advantageous if the detection of the defrosting requirement includes the determination of a first requirement parameter of the first heat pump outdoor unit, indicating an existing defrosting requirement. The first requirement parameter can be binary, where, for example, 1 indicates an existing defrosting requirement and 0 indicates no existing defrosting requirement. The first requirement parameter can be determined by the control unit. In a preferred embodiment of the invention, if the first demand parameter indicates an existing defrosting requirement for the first heat pump outdoor unit, the defrosting process for the first heat pump outdoor unit is postponed if a defrosting process is already running for another heat pump outdoor unit. Therefore, if a defrosting process is already running for another heat pump outdoor unit, the start criterion is not met. In a preferred embodiment of the invention, it is advantageous that if the defrosting process for the first heat pump outdoor unit is postponed, the first heat pump is switched off, at least until the defrosting process for the first heat pump outdoor unit can be carried out. This protects the first heat pump from damage and / or prevents inefficient operation. In an advantageous embodiment of the invention, the detection of the defrosting requirement includes the determination of a second requirement parameter of the first heat pump outdoor unit. The second requirement parameter can be provided by the first heat pump in addition to the first requirement parameter. The second requirement parameter can also be part of the first requirement parameter. For example, the first and second requirement parameters can be combined into a single, multi-valued requirement parameter. The second requirement parameter can be determined by the control unit. In a specific embodiment of the invention, it is advantageous if the second demand parameter indicates at least one imminent defrosting requirement for the first heat pump outdoor unit. The second demand parameter can, for example, be 0 for no imminent defrosting requirement and 1 for an imminent defrosting requirement. The imminent defrosting requirement can be one that will arise in a few more minutes, particularly in a maximum of 20 minutes, 10 minutes, or 5 minutes. In a preferred embodiment of the invention, the time at which the defrosting process is initiated in the first outdoor unit of the heat pump is set depending on the second demand parameter. This allows for time-based control of the start time of the defrosting process. In a preferred embodiment of the invention, it is advantageous that if an impending defrosting requirement of the first heat pump outdoor unit is indicated based on the second demand parameter, the defrosting process for the first heat pump outdoor unit is initiated at an earlier start time, provided the start criterion is also met at that start time. The start time at which the defrosting process is carried out can thus be brought forward compared to the start time of the defrosting process, which would only have been carried out when a defrosting requirement actually existed. The defrosting process can therefore also be initiated when an impending defrosting requirement is indicated, for example, when the heat exchanger of the first heat pump outdoor unit is not yet iced up or is beginning to ice up, particularly to eliminate incipient icing or to prevent impending icing. When setting the start time, a calculated defrost duration can also be taken into account. This duration is an average, estimated, and / or derived time based on a previous defrost cycle. For example, past defrost cycle distributions for the heat pump outdoor units can be used to predict an imminent defrosting requirement for another heat pump outdoor unit, which would occur before the first heat pump outdoor unit completes its defrost cycle with the calculated duration. In this case, a defrost cycle for the first heat pump outdoor unit can be postponed, and the system can wait for the actual defrosting requirement to arise. In a preferred embodiment of the invention, it is advantageous if, during the defrosting process, the heat energy is transferred from the second heat pump to the first heat pump, bypassing a heat buffer storage tank. This allows the heat energy in the heat buffer storage tank to be excluded from use during the defrosting process. According to the present invention, a heat pump system with the features according to claim 10 is further proposed. Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations. Character description The invention is described in detail below with reference to the figures. Specifically, the figures show: Fig. 1: A heating system with a heat pump network in a particular embodiment of the invention. Fig. 2: A defrost control system in a particular embodiment of the invention. Fig. 1 shows a heating system with a heat pump network in a specific embodiment of the invention. The heating system 10 for heating or cooling at least one building comprises a heat pump network 12 with several cascaded heat pumps 14, including a first heat pump 16, a second heat pump 18, and several further heat pumps 14'. The heat pumps 14 are connected via data links 17 to a control unit 19 for data transmission and / or energy transfer, which controls the cascaded operation of the heat pumps 14. The control unit 19 can be a central control unit or that of a master heat pump of the heat pump network 12, which controls the other heat pumps as slave heat pumps of the heat pump network 12. The heat pumps 14 are preferably designed as air-to-water heat pumps and can have the same nominal heating capacity. The first heat pump 16 comprises a first outdoor heat pump unit 20 with at least one evaporator, by which thermal energy is transferred from the outside air in the vicinity 22 of the first outdoor heat pump unit 20 to a refrigerant via a heat exchanger. The second heat pump 18 can also have such a second outdoor heat pump unit 23, and further heat pumps 14' of the heat pump system 12 can have such further outdoor heat pump units 24. The outdoor heat pump units 20, 23, and 24 can have a closed refrigerant circuit, and the heat energy can be transferred from the refrigerant circuit to the building's heating water. Alternatively, each outdoor heat pump unit 20, 23, and 24 can be assigned an indoor heat pump unit, which also share a common refrigerant circuit. The indoor heat pump unit can then transfer the heat energy from the refrigerant circuit to the building's heating water. A flow pipe 25 of each heat pump 14 is connected to a heating circuit manifold 26 and via this manifold to those of the other heat pumps 14. A return pipe 28 of each heat pump 14 is also connected to the heating circuit manifold 26 and via this manifold to those of the other heat pumps 14. The heating circuit manifold 26 is connected to a thermal buffer storage tank 32 via a common supply line 30, from which a common return line 34 runs to the heating circuit manifold 26. Heating devices 36 for heating and optionally for cooling the building, for example, at least one underfloor heating system 38 and / or at least one radiator 40 of the building, each with a heating circuit supply line 42 and a heating circuit return line 44, can be connected to the thermal buffer storage tank 32. The thermal buffer storage tank 32 can be connected to the control unit 19 for data transmission via a data connection 17'. At low outside temperatures, the respective heat exchanger of the heat pump outdoor unit 20, 23, 24 can ice up and must be defrosted by a defrosting process to maintain effective operation of the associated heat pump 14. A defrost control unit 46 for determining the defrosting requirement and / or for controlling the defrosting process can be assigned to the control unit 19. Fig. 2 shows a defrost control in a special embodiment of the invention. The defrost control 48 initially comprises providing 50 the heat pump network 12 with the cascaded heat pumps 14, of which a first heat pump 16, a second heat pump 18 and further heat pumps 14' each have a heat pump outdoor unit. A defrosting requirement 54 at the first outdoor unit 20 of the first heat pump 16 of the heat pump system 12 is determined by a first demand parameter 58 of the first heat pump 16, which indicates an existing defrosting requirement at the first outdoor unit 20, and a second demand parameter 62 of the first heat pump 16, which indicates an impending defrosting requirement at the first outdoor unit 20. The first demand parameter 58 can be 1 to indicate an existing defrosting requirement at the first outdoor unit 20 and otherwise 0. The second demand parameter 62 can be 1 to indicate an impending defrosting requirement at the first outdoor unit 20 and otherwise 0. During a defrosting process, the heat energy required for defrosting is supplied directly by the second heat pump 18 of the heat pump network 12 and transferred to the first outdoor heat pump unit 20. The heat energy for the defrosting process is thus generated directly by the second heat pump 18, bypassing a thermal buffer storage tank. A omission 66 of a defrosting process for the first heat pump outdoor unit 20 occurs when the first demand parameter 58 is 0, i.e., when there is no defrosting requirement. The defrosting process (defrosting) of the first heat pump outdoor unit 20 is initiated only if, as a start criterion 70, no other heat pump outdoor unit 14 in the heat pump network 12 is simultaneously performing a defrosting process. This condition can be queried using a status parameter 64, which each heat pump 14 outputs. For example, the status parameter of a heat pump 14 can be 1 if that heat pump 14 is not performing a defrosting process and 0 if that heat pump 14 is performing a defrosting process. The defrosting process is initiated only if the status parameters 64 of all heat pumps are 1. All status parameters 64 of the heat pumps 14 can be combined, for example, using a logical AND operation. The start criterion 70 is met, for example, if the result of the logical operation is 1 and not met if the result of the logical operation is 0. If the first demand parameter 58 indicates an existing defrosting requirement 54 at the first heat pump outdoor unit 20, where the first demand parameter 58 is 1, but the start criterion 70 is not met because at least one status parameter 64 of another heat pump is 0, the defrosting process at the first heat pump outdoor unit 20 is postponed 72, at least until the defrosting process at the first heat pump outdoor unit 20 can be carried out, since a defrosting process is already underway at another heat pump outdoor unit. This ensures that sufficient immediate heat energy is always available for the defrosting process at the first heat pump outdoor unit 20 from the other heat pumps 14. During the deferral period 72, the first heat pump 16 can continue to operate. If continued operation is not permitted, the first heat pump 16 is shut down 74, while the defrosting process for the first heat pump outdoor unit 20 is postponed. This protects the first heat pump 16 from damage and / or prevents inefficient operation of the first heat pump 16. If the second demand parameter 62 indicates an impending defrosting requirement for the first heat pump outdoor unit 20, by setting the second demand parameter 62 to 1, then, if the demand parameter is 0 (i.e., if there is currently no defrosting requirement for the first heat pump outdoor unit 20), the initiation of the defrosting process for the first heat pump outdoor unit 20 can be brought forward to an earlier start time, provided that the start criterion 70 is also met at this start time. The defrosting process can thus be initiated even if an impending defrosting requirement is indicated, for example, if the heat exchanger of the first heat pump outdoor unit 20 is not yet iced up, particularly to eliminate incipient icing or to prevent impending icing. The defrost control unit can query the first and second demand parameters 58 and 62, as well as the status parameter 64, and control the defrosting process. For example, the status parameter 64 can be queried first, followed by the first demand parameter 58, and then, or simultaneously, the second demand parameter 62.

Claims

Defrost control (48) of a heat pump network (12) with several cascaded heat pumps (14), comprising the steps of providing (50) the heat pump network (12), detecting (52) a defrosting requirement (54) at at least one first heat pump outdoor unit (20) of a first heat pump (16) of the heat pump network (12), initiating (68) a defrosting process at at least the first heat pump outdoor unit (20) by supplying heat energy to the first heat pump outdoor unit (20) depending on the detected defrosting requirement, characterized in that during the defrosting process the heat energy required for this is directly provided by at least one other second heat pump (18) of the heat pump network (12) and transferred to the first heat pump outdoor unit (20), wherein the initiation (68) of the defrosting process at the first heat pump outdoor unit (20) only takes place if no other start criterion (70) is present. Heat pump outdoor unit (23,24) of the other heat pumps (14) of the heat pump network (12) simultaneously performs a defrosting process. Defrost control (48) according to claim 1, characterized in that the detection (52) of the defrosting requirement (54) includes a determination (56) of a first requirement parameter (58) of the first heat pump outdoor unit (20) indicating an existing defrosting requirement at the first heat pump outdoor unit (20). Defrost control (48) according to claim 2, characterized in that if the first demand parameter (58) indicates an existing defrosting requirement at the first heat pump outdoor unit (20), the defrosting process at the first heat pump outdoor unit (20) is postponed if a defrosting process is already running at another heat pump outdoor unit (23, 24). Defrost control (48) according to claim 3, characterized in that if the defrosting process is postponed at the first heat pump outdoor unit (20), the first heat pump (16) is switched off, at least until the defrosting process can be carried out at the first heat pump outdoor unit (20). Defrost control (48) according to one of the preceding claims, characterized in that the detection (52) of the defrost requirement includes a determination (60) of a second requirement parameter (62) of the first heat pump outdoor unit (20). Defrost control (48) according to claim 5, characterized in that the second demand parameter (62) indicates at least one imminent defrosting requirement for the first heat pump outdoor unit (20). Defrost control (48) according to claim 5 or 6, characterized in that the time of initiation (68) of the defrosting process at the first heat pump outdoor unit (20) is set depending on the second demand parameter (62). Defrost control (48) according to claim 7, characterized in that if an impending defrost requirement of the first heat pump outdoor unit (20) is indicated on the basis of the second demand parameter (62), the initiation (68) of the defrosting process at the first heat pump outdoor unit (20) is started at an earlier start time if the start criterion (70) is also met at this start time. Defrost control (48) according to one of the preceding claims, characterized in that during the defrosting process the heat energy is transferred from the second heat pump (18) to the first heat pump (16) bypassing a heat buffer storage tank (32). heat pump system (12) comprising several cascaded heat pumps (14) connected to each other, at least several of which have a heat pump outdoor unit (20, 23, 24) and including a first heat pump (16) of the heat pump system (12) comprising a first heat pump outdoor unit (20) which is defrostable by a defrost control (48) according to one of the preceding claims.

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