EP3594588A1

EP3594588A1 - Geothermal heat pump device

Info

Publication number: EP3594588A1
Application number: EP17899277.2A
Authority: EP
Inventors: Yoshiro Aoyagi; Kazutaka Suzuki; Koji Matsuzawa
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-03-09
Filing date: 2017-03-09
Publication date: 2020-01-15
Anticipated expiration: 2037-03-09
Also published as: EP3594588B1; EP3594588A4; WO2018163347A1; JPWO2018163347A1

Abstract

A geothermal heat pump device includes a heat pump heat source unit having a refrigerant circuit in which a compressor, a water-refrigerant heat exchanger, an expansion valve, and a refrigerant-brine heat exchanger in which a heat medium from an underground heat exchanger buried underground is connected such that the heat medium circulates are serially connected, a warm-water heater unit configured to supply warm water heated at the water-refrigerant heat exchanger to heating and air conditioning and hot water supply such that the warm water circulates, and a controller configured to control an upper limit of an operation frequency of the compressor based on a heat collection limit value set by comparing a unit necessary evaporation capacity calculated from information on the underground heat exchanger with a unit actual evaporation capacity calculated from inlet and outlet temperatures and a circulation flow rate of the heat medium circulating through the refrigerant-brine heat exchanger.

Description

Technical Field

The present invention relates to a geothermal heat pump device that uses the ground as a heat source, causes a heat medium to circulate through an underground heat exchanger, collects heat using a heat pump, and supplies warm water to a load side.

Background Art

A geothermal heat pump system that uses the ground and lakes as heat sources, causes a heat medium to circulate through an underground heat exchanger, collects and releases heat using a heat pump, and supplies warm water for heating or household use to a load side is a device using renewable energy. In particular, because of the use of geothermal heat of which the temperature is stable all year round, the geothermal heat pump system is regarded as a highly efficient device with low running cost and is capable of reducing the emission of CO2, and hence has attracted more attention recently.
To keep using a geothermal heat pump system all year round, it is necessary to cause the ground to store heat during summertime and to effectively use the stored heat during wintertime. Since the amount of stored heat is limited, in a case where a heating operation is excessively performed during wintertime, the amount of heat consumed is large, the stored heat is consumed before winter ends, the heating operation is no longer performed, and an underground heat exchanger buried underground for heat collection may be frozen and broken in the end. Thus, an outlet temperature of heat medium water is made measurable using a temperature sensor, a soil temperature is calculated from the outlet temperature of the heat medium water, and limit values for heat collection and heat release to be performed by an underground heat exchanger are made settable. In addition, not to exceed the set limit values, a heat pump can stop operating or be operated less actively (for example, see Patent Literature 1).
As a method for setting limit values, an outlet temperature of heat medium water is measured using a temperature sensor, a soil temperature is calculated from the outlet temperature of the heat medium water by a controller in which a program or data that has been input in advance is installed, and the limit values for heat collection and release are set. Furthermore, the limit values are determined also on the basis of the soil temperature of the previous year. A technology for grasping an operation status and geothermal heat characteristics as needed, estimating operation and performance on the basis of the operation status and geothermal heat characteristics, and adjusting system operating time and the amount of heat to be collected or released is disclosed (for example, see Patent Literature 2).

Citation List

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2006-292310
Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2012-233669

Summary of Invention

Technical Problem

However, the above-mentioned existing systems require a great many programs and many pieces of data to deal with environmental conditions, such as places where the devices are used and climates of the places, and various types of grounds and underground heat exchangers, thereby requiring complicated controllers. In a case where appropriate control is not possible, there is a problem in that underground heat exchangers may be frozen and broken and a complaint that heating is insufficient may arise.
The present invention has been made to solve the above-described problem, and an object thereof is to set a limit value for heat collection from underground by using a simple method using, for example, detection data obtained from a geothermal heat pump device and specifications of a geothermal heat pump device, and provide pleasant air conditioning and hot water supply that meet users' requests without the freezing and breakdown of an underground heat exchanger.

Solution to Problem

A geothermal heat pump device according to an embodiment of the present invention includes a heat pump heat source unit having a refrigerant circuit in which a compressor, a water-refrigerant heat exchanger, an expansion valve, and a refrigerant-brine heat exchanger in which a heat medium from an underground heat exchanger buried underground is connected such that the heat medium circulates are serially connected, a warm-water heater unit configured to supply warm water heated at the water-refrigerant heat exchanger to heating and air conditioning and hot water supply such that it circulates, and a controller configured to control an upper limit of an operation frequency of the compressor based on a heat collection limit value set by comparing a unit necessary evaporation capacity calculated from information on the underground heat exchanger with a unit actual evaporation capacity calculated from inlet and outlet temperatures and a circulation flow rate of the heat medium circulating through the refrigerant-brine heat exchanger.

Advantageous Effects of Invention

A geothermal heat pump device of an embodiment of the present invention includes a heat pump heat source unit having a refrigerant circuit in which a compressor, a water-refrigerant heat exchanger, an expansion valve, and a refrigerant-brine heat exchanger in which a heat medium from an underground heat exchanger buried underground is connected such that the heat medium circulates are serially connected, a warm-water heater unit configured to supply warm water heated at the water-refrigerant heat exchanger to heating and air conditioning and hot water supply such that the warm water circulates, a controller configured to control an upper limit of an operation frequency of the compressor based on a heat collection limit value set by comparing a unit necessary evaporation capacity calculated from information on the underground heat exchanger with a unit actual evaporation capacity calculated from inlet and outlet temperatures and a circulation flow rate of the heat medium circulating through the refrigerant-brine heat exchanger. An effect is achieved that the limit value for heat collection from underground is set by using a simple method using, for example, detection data obtained from the geothermal heat pump device and specifications of the geothermal heat pump device, and pleasant air conditioning and hot water supply that meet users' requests can be provided without the freezing and breakdown of the underground heat exchanger.

Brief Description of Drawings

[Fig. 1] Fig. 1 is a circuit diagram illustrating a schematic configuration of a geothermal heat pump device according to Embodiment 1 of the present invention.
[Fig. 2] Fig. 2 is a block diagram illustrating an electrical configuration of a controller of the geothermal heat pump device according to Embodiment 1 of the present invention.
[Fig. 3] Fig. 3 is a flowchart illustrating a control operation of the geothermal heat pump device according to Embodiment 1 of the present invention.
[Fig. 4] Fig. 4 is a characteristic diagram illustrating compressor operation frequency control performed by the geothermal heat pump device according to Embodiment 1 of the present invention.

Description of Embodiments

Embodiment

1

Fig. 1 is a circuit diagram illustrating a schematic configuration of a geothermal heat pump device according to Embodiment 1 of the present invention, and Fig. 2 is a block diagram illustrating an electrical configuration of a controller of the geothermal heat pump device. The overall configuration will be described on the basis of Figs. 1 and 2.
A geothermal heat pump device 15 of Fig. 1 is a heat-pump hot water system using geothermal heat. The heat-pump hot water system causes a heat medium to circulate through an underground heat exchanger, collects heat using a heat pump, and supplies warm water for heating or living to a load side. The geothermal heat pump device 15 includes a heat pump heat source unit 22 and a warm-water heater unit 23, the heat pump heat source unit 22 performing a heat pump cycle (refrigeration cycle) operation using a refrigerant circuit, the warm-water heater unit 23 having a function of supplying warm water for heating to an indoor space and including devices, such as a heated-water tank 12 that stores warm water. An underground heat exchanger 18 or 19 buried underground is connected to the heat pump heat source unit 22, a heat medium is caused to circulate, and heat is collected using the heat pump.
The geothermal heat pump device 15 of the present invention is a heat-pump air-conditioning hot water system that exchanges heat between refrigerant inside the refrigerant circuit of the heat pump heat source unit 22, which performs the heat pump cycle (refrigeration cycle) operation, and a heat medium (for example, such as brine) of a circulation circuit using the underground heat exchanger, exchanges heat between the refrigerant inside the refrigerant circuit of the heat pump heat source unit 22 and water in a water circuit connected to the warm-water heater unit 23, performs a heating operation by supplying, through the circulation of this water, warm water for heating to an indoor space, and that can further perform a hot-water supply operation by heating water stored in the heated-water tank 12.
Here, the underground heat exchangers 18 and 19 will be described. There are two kinds of heat collection systems: a borehole system in which a 100-m to 150-m vertical hole is bored in the ground and a heat exchange pipe is inserted therein, and a horizontal loop system in which a heat exchange pipe is horizontally buried into a shallow ground (1 m to 2.5 m) and heat is collected. In Fig. 1, the underground heat exchanger 18 is used to show the borehole system, and the underground heat exchanger 19 is used to show the horizontal loop system.
Examples of the refrigerant used in the refrigeration cycle of the heat pump heat source unit 22 include a HFO single refrigerant such as HFO-1234yf, a mixed refrigerant containing a HFO refrigerant and a HFC refrigerant such as R32, and natural refrigerants such as hydrocarbon, helium, and carbon dioxide.
The heat pump heat source unit 22 is equipped with structural devices of the refrigerant circuit such as a refrigerant-brine heat exchanger (for example, a plate heat exchanger) 4 configured to exchange heat between a ground side heat medium and refrigerant, a water-refrigerant heat exchanger (for example, a plate heat exchanger) 2 configured to exchange heat between water on the warm-water heater side and refrigerant, a compressor 1 configured to compress refrigerant, and an expansion valve 3.
In addition, the heat pump heat source unit 22 is provided with a heat collection pump 5 for causing the heat medium to circulate through the underground heat exchanger 18, 19, a heat collection flow rate sensor 6 configured to detect flow rate of the heat medium for heat collection, and a heat collection return sensor 7 and a heat collection supply sensor 8 for heat collection control and protection.
The warm-water heater unit 23 is provided with, in addition to the heated-water tank 12, a pump 9 configured to cause water inside the water circuit to circulate, the water having exchanged heat with refrigerant inside a refrigerant circuit in the water-refrigerant heat exchanger (for example, a plate heat exchanger) 2, an electric heater 10 capable of further complementarily heating warm water heated at the water-refrigerant heat exchanger 2 at the time of heating, a three-way valve 21 serving as a channel switching unit that performs switching of a circulation destination of the water having exchanged heat at the water-refrigerant heat exchanger 2, a warm-water circulation flow rate sensor 14 for water flow rate detection, a controller 16 configured to perform overall operation control, a remote control 17 through which a user can perform a setting operation, and water temperature sensors 11 and 13 used for control and protection for a heating operation and a hot-water supply operation.
In Fig. 1, the directions of arrows indicate the direction of flow of the refrigerant at the time of heating, the direction of flow of the water, and the direction of the heat medium in the ground.
At the time of a heating operation or a hot-water supply operation through which the water stored in the heated-water tank 12 is heated at the warm-water heater unit 23, refrigerant is discharged from the compressor 1 in the directions of the arrows in Fig. 1 and water is heated by the refrigerant at the water-refrigerant heat exchanger 2 in the heat pump heat source unit 22, so that warm water (hot water) is generated. Thereafter, the pressure on the refrigerant is reduced by the expansion valve 3, and the refrigerant exchanges heat at the refrigerant-brine heat exchanger 4 with the heat medium circulating through the underground heat exchanger 18 or 19 buried underground. The refrigerant is superheated, returns to the compressor, is compressed again, and is discharged. This operation cycle continues during the heating operation.
The warm water obtained from the heat pump heat source unit 22 reaches the three-way valve 21 via the electric heater 10. The three-way valve 21 can switch a circulation destination of the warm water between a water-supply path to an indoor-side air-conditioning radiator and the side where the heated-water tank 12 is provided. Heating can be performed by switching the circulation destination to the indoor side at the three-way valve 21 and causing the warm water to circulate through the indoor radiator. Moreover, the water stored in the heated-water tank 12 can be heated by switching the circulation destination to the tank 12 side at the three-way valve 21 and causing the warm water to circulate through the tank. The water whose temperature has been reduced by passing through an indoor space or the heated-water tank 12 returns to the water-refrigerant heat exchanger 2 via the warm-water circulation pump 9 and circulates again.
The heated-water tank 12 is substantially cylindrically shaped, and at least its outside is composed of, for example, a metal material, such as stainless steel. A water supply pipe that supplies water from, for example, a waterworks outside the system is connected to a lower portion of the heated-water tank 12. Water supplied from the water supply pipe flows into and stored in the heated-water tank 12. The water stored in the heated-water tank 12 is heated by performing the heating operation described above, and warm water is generated. In the heated-water tank 12, hot water is stored so as to form temperature layers such that high temperature layers are on the upper side and low temperature layers are on the lower side. A hot-water output pipe is connected to an upper portion of the heated-water tank 12 to remove warm water generated in the heated-water tank 12. The warm water generated in the heated-water tank 12 is supplied to the outside of a geothermal heat pump system 12 through the hot-water output pipe and is used as, for example, water for domestic use. The heated-water tank 12 is covered by a heat insulator to suppress heat dissipation from the stored warm water.
Next, the heat pump heat source unit 22 will be described. The compressor 1 is a capacity controllable type whose rotation speed is controlled by an inverter, and provides a high-temperature, high-pressure state by suctioning and compressing refrigerant. The expansion valve 3 is an electronic expansion valve whose opening degree is variably controlled. The water-refrigerant heat exchanger 2 exchanges heat between water and refrigerant by using, for example, the warm-water circulation pump 9. The refrigerant-brine heat exchanger 4 exchanges heat between the heat medium flowing in the underground heat exchanger 18, 19 and refrigerant by using, for example, the heat collection pump 5.
Fig. 2 is a control block diagram according to Embodiment 1 of the present invention.
Fig. 2 illustrates a connection configuration of the controller 16 configured to perform various types of measurement control on the geothermal heat pump device 15 of Embodiment 1 and operation information, actuators, and other devices connected to the controller 16.
The controller 16 of the geothermal heat pump device 15 controls, for example, an operation frequency of the compressor 1 of the heat pump heat source unit 22 and the opening degree of the expansion valve 3 on the basis of measurement information from the temperature sensors 7, 8, 11, and 13 and operation details instructed and set by the user of the geothermal heat pump device 15.
An operation of the heat pump heat source unit 22 will be described. At the time of a heating and hot-water supply operation, a high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the water-refrigerant heat exchanger 2 in the refrigerant circuit of the heat pump cycle. The gas refrigerant condenses and liquefies while dissipating heat at the water-refrigerant heat exchanger 2 serving as a condenser to become a high-pressure, low-temperature liquid refrigerant. Heat dissipated from the refrigerant is supplied to water on the load side to warm the water. Thereafter, the high-pressure, low-temperature refrigerant output from the water-refrigerant heat exchanger 2 flows into the refrigerant-brine heat exchanger 4 serving as an evaporator, absorbs heat and evaporates there, and is gasified. Thereafter, the gas is suctioned by the compressor 1 and circulates.
To adapt the geothermal heat pump device to various types of grounds and underground heat exchangers and use the geothermal heat pump device all year round and not to use up geothermal heat stored during summertime before winter ends, when a main body of the geothermal heat pump device 15 is locally installed, an installation contractor inputs, from the remote control 17, sets, and registers a necessary heating capacity estimated from a use-side set load and information on, for example, conditions for the underground heat exchanger 18, 19 or for the ground side. For example, for the underground heat exchange 18, 19, data such as the total length of a vertical hole in the case of a borehole system and a tube buried area in the case of a horizontal loop system is input. In addition, information on the total quantity of heat collection pre-designed and estimated for underground heat exchangers to be used is also input through the remote control 17.
In the geothermal heat pump device according to the present invention, to keep using the geothermal heat pump system all year round, the controller 16 sets a heat collection limit value calculated from a computation performed using detected temperature data to prevent occurrence of a case where stored heat is used up before winter ends by performing a heating operation excessively during wintertime and the underground heat exchanger for heat collection is frozen and broken. The operation of the heat pump is stopped or made less active such that the set limit value is not exceeded.
That is, the controller 16 sets the heat collection limit value on the basis of the input ground-side information and the necessary capacity information, and controls the upper limit of the operation frequency of the compressor. This control will be described below together with a flow chart of Fig. 3 illustrating a control procedure.
First, a necessary evaporator capacity Q2required is calculated by subtracting a compressor input Wcomp in a heat pump cycle from ground-side information input from the remote control 17, such as the total length Dinput of a vertical hole in the case of a borehole system, and a necessary heating capacity Q1 required (step S1). A unit necessary evaporation capacity QDrequired per unit length is calculated from the necessary evaporator capacity Q2required and the total length Dimput of the vertical hole regarding and for burying the underground heat exchanger 18 (step S2).
Next, an actual evaporation capacity Qacutual is calculated from the flow rate of a heat medium that actually flows and the difference between an inlet temperature and an outlet temperature of the refrigerant-brine heat exchanger. The flow rate of the heat medium that actually flows is measured by the heat collection flow rate sensor 6, and the difference between the inlet temperature and outlet temperature of the refrigerant-brine heat exchanger is calculated from measurement values of the heat collection return sensor 7 and the heat collection supply sensor 8.
A unit actual evaporation capacity QDacutual per unit length is calculated by dividing the calculated actual evaporation capacity Qacutual by a total length Dactual of an actual vertical hole for the underground heat exchanger 18 to be actually used for heat collection. In this case, to calculate the total length Dactual of the actual vertical hole, the calculation is performed using the flow rate of the heat medium that actually flows and the time required for the heat medium to travel from the inlet to the outlet of the refrigerant-brine heat exchanger. The flow rate of the heat medium that actually flows is measured by the heat collection flow rate sensor 6, and the time required to travel from the inlet to the outlet of the refrigerant-brine heat exchanger is measured by the controller 16 (step S3).
The controller 16 compares the unit necessary evaporation capacity QDrequired per unit time with the unit actual evaporation capacity QDacutual per unit length, which have been calculated so far (step S4).
This comparison shows that, in a case where the unit necessary evaporation capacity QDrequired per unit length, which is preset, is smaller than the unit actual evaporation capacity QDacutual per unit length for an actual heat collection operation, the unit necessary evaporation capacity QDrequired, which is calculated, is set as a limit value for heat collection from underground and is used for a compressor operation in a heat pump refrigeration cycle (step S5). This makes it possible to keep using the heat pump heat source unit 22 of the geothermal heat pump device 15 all year round (geothermal heat stored during summertime is not used up until winter ends), thereby resulting in a high energy saving effect since no electric heater is used.
In contrast, in a case where the unit necessary evaporation capacity QDrequired per unit length is greater than the unit actual evaporation capacity QDacutual per unit length, the unit actual evaporation capacity QDacutual, which is calculated, is set as a limit value for heat collection in a heat pump device operation (step S6), and the controller 16 performs control such that operation switching is conducted so that the difference between the unit necessary evaporation capacity QDrequired and the unit actual evaporation capacity QDacutual, which is calculated, corresponds to a heating operation to be performed by the electric heater 10.
In a case where the unit necessary evaporation capacity QDrequired per unit length is greater than the unit actual evaporation capacity QDacutual per unit length, the unit actual evaporation capacity QDacutual, which is calculated, is set as the limit value for heat collection in the heat pump device operation, and operation control is conducted such that the heating operation is performed in which the difference is compensated with additional heating performed by the electric heater 10 capable of conducting supplemental heating. To cause the heat pump device to operate as much as possible, the upper limit of the operation frequency of the compressor is limited on the basis of a heat collection cumulative limit value, a cumulative evaporation capacity, and the temperature of the heat medium circulating through the underground heat exchanger.
As illustrated in Fig. 4, the upper limit of the operation frequency of the compressor is limited on the basis of the heat collection cumulative limit value and the temperature of the heat medium circulating through the underground heat exchanger, the heat collection cumulative limit value being based on the cumulative evaporation capacity calculated cumulatively from the total operation time and the flow rate of the heat medium by using the unit actual evaporation capacity. In Fig. 4, the vertical axis represents the heat collection cumulative limit value, and the horizontal axis represents the upper limit of the operation frequency of the compressor. The difference between the heat collection cumulative limit value and the cumulative evaporation capacity is calculated as needed, and in a case where half the difference and the temperature of the heat medium circulating through the underground heat exchanger at the time when the heat medium flows into the refrigerant-brine heat exchanger 4 are lower than a predetermined temperature T1, the upper limit of the operation frequency of the compressor is limited. As illustrated in Fig. 4, as the difference between the heat collection cumulative limit value and the cumulative evaporation capacity is reduced, the upper limit of the operation frequency of the compressor is limited and decreased. In this case, the predetermined temperature T1 is higher than a freezing start temperature of a brine heat medium by α deg and is a value based on brine characteristics. For example, in the case of propylene glycol, α = 0 degrees C.
That is, even when half the difference between the heat collection cumulative limit value and the cumulative evaporation capacity is reached, in a case where the inflow temperature at the refrigerant-brine heat exchanger 4 is greater than or equal to T1 degrees C, the upper limit of the operation frequency is not limited and the operation continues as is.
In a case where the difference between the heat collection cumulative limit value and the cumulative evaporation capacity reaches 0, the heat pump heat source unit 22 stops operating and the operation is completely switched to an operation performed by the electric heater 10. In this manner, in a case where the difference between the heat collection cumulative limit value and the cumulative evaporation capacity reaches 0, the operation is switched to an operation performed by the electric heater 10 and a heating operation is handled, thereby lessening the energy saving effect. Learning control is thus performed in the next winter such that the upper limit of the operation frequency of the compressor is limited in a case where half the difference between the heat collection cumulative limit value and the cumulative evaporation capacity and the inflow temperature at the refrigerant-brine heat exchanger 4 are below (T1 + 1) degrees C, thereby making it possible to prolong a period during which the heat pump can perform a heating operation.
In this manner, to perform optimization by performing learning control year after year, to prolong the period during which the heat pump can operate, and to keep using the geothermal heat pump device all year round on various types of grounds and geothermal water heat exchangers, operation control is possible such that the geothermal heat stored during summertime is not used up before winter ends. An effect is achieved that the limit value for heat collection from underground is set by using a simple method using, for example, detection data obtained from the geothermal heat pump device and specifications of the geothermal heat pump device, and pleasant air conditioning and hot water supply that meet users' requests can be provided without the freezing and breakdown of the underground heat exchanger. Reference Signs List
1 compressor 2 water-refrigerant heat exchanger 3 expansion valve 4 refrigerant-brine heat exchanger 5 heat collection pump 6 heat collection flow rate sensor 7 heat collection return sensor 8 heat collection supply sensor 9 warm-water circulation pump 10 electric heater 11 warm-water circulation supply water temperature sensor 12 heated-water tank 13 warm-water circulation return water temperature sensor 14 warm-water circulation flow rate sensor 15 geothermal heat pump device 16 controller 17 remote control 18 underground heat exchanger (borehole system) 19 underground heat exchanger (horizontal loop system) 20 heated-water tank sensor 21 three-way valve 22 heat pump heat source unit 23 warm-water heater unit

Claims

A geothermal heat pump device comprising:
a heat pump heat source unit having a refrigerant circuit in which a compressor, a water-refrigerant heat exchanger, an expansion valve, and a refrigerant-brine heat exchanger in which a heat medium from an underground heat exchanger buried underground is connected such that the heat medium circulates are serially connected;

a warm-water heater unit configured to supply warm water heated at the water-refrigerant heat exchanger to heating and air conditioning and hot water supply such that the warm water circulates; and

a controller configured to control an upper limit of an operation frequency of the compressor based on a heat collection limit value set by comparing a unit necessary evaporation capacity calculated from information on the underground heat exchanger with a unit actual evaporation capacity calculated from inlet and outlet temperatures and a circulation flow rate of the heat medium circulating through the refrigerant-brine heat exchanger.
The geothermal heat pump device of claim 1, comprising a heat collection flow rate sensor configured to measure a flow rate of the heat medium circulating between the underground heat exchanger and the refrigerant-brine heat exchanger, wherein the unit actual evaporation capacity is calculated using a circulation flow rate detected by the heat collection flow rate sensor.
The geothermal heat pump device of claim 1 or 2, comprising a remote control connected to the controller, wherein a length of a pipe of the underground heat exchanger buried underground and a preset necessary heating capacity are registered through the remote control.
The geothermal heat pump device of any one of claims 1 to 3, wherein in a case where the unit necessary evaporation capacity is smaller than the unit actual evaporation capacity, an upper limit for underground heat collection is set from the unit necessary evaporation capacity, and in a case where the unit necessary evaporation capacity is greater than the unit actual evaporation capacity, an upper limit value for underground heat collection is set from the unit actual evaporation capacity and operation control is performed such that additional heating for a heat shortage corresponding to a difference is performed by an electric heater provided at a warm water circuit of the warm-water heater unit.
The geothermal heat pump device of any one of claims 1 to 3, wherein the upper limit of the operation frequency of the compressor is limited using a difference between a cumulative evaporation capacity for heat collected so far based on the unit actual evaporation capacity and a heat collection cumulative limit value.