EP4375592A1

EP4375592A1 - Energy monitoring system for a heat pump

Info

Publication number: EP4375592A1
Application number: EP23211784.6A
Authority: EP
Inventors: Francesco Mirandola; Antonio CAVALER
Original assignee: Ferroli SpA
Current assignee: Ferroli SpA
Priority date: 2022-11-24
Filing date: 2023-11-23
Publication date: 2024-05-29

Abstract

An energy monitoring system for a heat pump (100), having a compressor (101), an evaporator (102), an expansion valve (103), and a condenser (104), which form a refrigerant cycle through which the working fluid circulates, comprises: a sensing system, for detecting a first temperature parameter and a second temperature parameter; a memory containing reference data representative of mathematical relations which link the input power and/or the output cooling power to the first and second temperature parameter; a processing unit, for deriving, in real time, an estimated value of the input power and/or of the cooling power from the heat pump (100), based on the first and the second temperature parameter and based on the reference data. The evaporator (102) receives a heat flux in an adjoining space from a fluid (A). The first temperature parameter is representative of a temperature of the working fluid at the evaporator (102) or of the temperature of the fluid (A) which releases the heat flux to the evaporator; the second temperature parameter is representative of the temperature of the exchanging fluid or of the temperature of the working fluid at the condenser.

Description

The present invention relates to an energy monitoring system for a heat pump. With the increasingly widespread use of heat pumps, it is becoming necessary to have a monitoring system of their energy consumption or thermal energy produced. With regard to energy consumption, in a heat pump, its estimate is mainly linked to the consumption of the power components used, such as the compressor, the fans and, where present, the electrical resistors.
However, on the one hand, if the consumption can be well estimated for fans and resistors in relation to their time and mode of use, in a heat pump the input power and the cooling/thermal power generated by the compressor cannot be determined so well, being strongly linked to the following parameters:

saturation evaporation temperature,
saturation condensation temperature,

overheating of the evaporating gas
sub-cooling of the condensing liquid.

The term "saturation evaporation temperature" refers to the saturation temperature of the gas (refrigerant in the gas state) in the vapour phase corresponding to the evaporation pressure measured at the inlet of the compressor.
The term "saturation condensation temperature" refers to the saturation temperature of the gas in the vapour phase corresponding to the condensation pressure measured at the outlet of the compressor.
Observing typical graphs of a compressor used in heat pumps, it can be noted that both the cooling power and the input electrical power depend on the relationship between the saturation evaporation temperature and the saturation condensation temperature for specific overheating and sub-cooling values.
Typically, to calculate the input power or the cooling/thermal power generated by the heat pump, the saturation evaporation temperature and the saturation condensation temperature are calculated and the value of the output cooling/thermal power and the input power are obtained/estimated from the compressor graphs (provided by the manufacturer), which illustrate the saturation evaporation temperature and the saturation condensation temperature in association with the cooling power and the input power.
Usually, pressure transducers placed at the suction and discharge of the compressor must be used for the calculation of the saturation evaporation temperature and the saturation condensation temperature and therefore, based on the type of refrigerant, use equations (available in the literature) which allow the calculation thereof.
The accuracy of the calculation of the evaporation and condensation temperature is directly linked to the accuracy of the pressure transducers used for the measurement.
In this context, patent document CN109086447A provides a method for detecting the energy consumption and the cooling/thermal energy produced by a heat pump device.
Furthermore, the scientific articles reported below describe the derivation of the power/energy consumption of a compressor in an air conditioning system.: GUO YABIN ET AL: "Development of a virtual variable-speed compressor power sensor for variable refrigerant flow air conditioning system", INTERNATIONAL JOURNAL OF REFRIGERATION, ELSEVIER, AMSTERDAM, NL, vol.74; KIM WOOHYUN ET AL: "Fault detection and diagnostics analysis of air conditioners using virtual sensors", APPLIED THERMAL ENGINEERING, PERGAMON, OXFORD, GB, vol.191.
These documents concern reversible direct expansion systems for cooling or heating air.
In particular, GUO YABIN ET AL concerns the derivation of the power of a compressor in an air conditioning system. According to this article, the compressor power can be obtained from a virtual variable speed compressor power sensor (VVCP sensor) using three input parameters (frequency, condensation temperature and evaporation temperature). The compressor power obtained is used for the monitoring, control, diagnostics and maintenance of the VRF (Variant Refrigerant Flow) system.
KIM WOOHYUN ET AL concerns evaluating, implementing and demonstrating fault detection and diagnostics based on a series of virtual sensors in the field of air conditioners. According to this document, to monitor the health status of the HVAC system (i.e., heating, ventilation and air conditioning), the virtual compressor power sensor (VCP) is used to estimate the energy consumption of the compressor with physical sensors. The VCP sensor is used to estimate the power absorbed by the compressor based on second order functions in terms of condensation and evaporation temperature and compressor suction density.
However, the energy monitoring systems and methods for a heat pump of the prior art have some drawbacks and can be improved. In particular, the known energy monitoring systems and methods are complex and expensive. There is a need in this field to create an energy monitoring system for estimating the electrical energy consumed and the cooling/thermal energy produced by a heat pump with greater efficiency and less complexity.
It is an object of the present invention to provide an energy monitoring system for a heat pump which overcome the aforementioned drawbacks of the prior art.
Said object is fully achieved by the system and by the method which are the subject-matter of the present invention, which is characterized by what is contained in the claims below.
According to an aspect of the present description, the present invention provides an energy monitoring system for a heat pump. The heat pump comprises a compressor. The compressor has an inlet. The compressor also includes an outlet. The compressor is configured to increase the pressure of a working fluid. In an example, the working fluid is a refrigerant. The heat pump also includes an evaporator. The evaporator has an inlet.
The inlet of the evaporator is for receiving the working fluid in liquid state. The evaporator also includes an outlet. The outlet of the evaporator is configured to release the working fluid in gas state. The evaporator receives a heat flux in an adjoining space. The evaporator receives the heat flux from a fluid. In an example, the evaporator receives an external air flow. The external air flow can be hot air. There is a heat exchange between the evaporator and the external air. The evaporator receives a heat flux from the external air. In another example, the evaporator can exchange heat with a liquid (e.g., water).
The heat pump also includes an expansion valve. The expansion valve is for expanding the working fluid.
The heat pump includes a condenser. The condenser is configured to receive the working fluid in gas state. The condenser is configured to release liquid low temperature working fluid.
The condenser releases a heat flux to an exchange fluid. The condenser releases the heat flux in a space adjoining the exchanging fluid. The exchanging fluid can be liquid or gas. In an example, the exchanging fluid is water.
The compressor, evaporator, condenser and expansion valve form a refrigeration cycle. The working fluid circulates through said refrigeration cycle.
The energy monitoring system comprises a sensing system. The sensing system includes a first temperature detection device. The first temperature detection device is configured to detect a first temperature parameter. In an example, the first temperature parameter can be representative of a temperature of the working fluid at the evaporator. In another example, the first temperature parameter can be representative of the temperature of the fluid which releases the heat flux to the evaporator. In an example, the first temperature parameter can be representative of the temperature of the external air flow flowing through the evaporator. In the case in which the evaporator exchanges heat with a liquid, the first temperature parameter can be representative of the temperature of the liquid which is in contact with the evaporator. The sensing system includes a second temperature detection device. The second temperature detection device is configured to detect a second temperature parameter. In an example, the second temperature parameter is representative of the temperature of the exchanging fluid. In another example, the second temperature parameter is representative of the temperature of the working fluid at the condenser. The energy monitoring system comprises a memory. The memory contains reference data. The reference data can be representative of mathematical relations. In an example, said mathematical relations link the input power (i.e., input electrical power) and/or the output power (i.e., cooling/thermal power) of the heat pump to the first and second temperature parameters. The term "input power" refers to the electrical power which the pump uses to operate. The term "output power" refers to the amount of heat which the pump is capable of providing or yielding. The term cooling power refers to the cooling power extracted from the evaporator. The term thermal power refers to the thermal power yielded to the condenser. The energy monitoring system comprises a processing unit. The processing unit is connected to the sensing system. The processing unit is configured to the memory. The processing unit is programmed to derive, in real time, an estimated value of the input power and/or of the output power of the heat pump. The processing unit derives the estimated value of the input power and/or the output power of the (i.e., cooling/thermal power of the heat pump) based on the first and second temperature parameters and based on the reference data.
It should be noted that the first and second temperature detection devices are normally present in a heat pump to ensure the proper operation of the heat pump. Therefore, according to an aspect of the present description, it is envisaged that the input power and the cooling/thermal power of the heat pump are estimated using devices which are usually present in a heat pump and without using additional devices for measuring other parameters. Such solution allows to obtain an energy monitoring system for monitoring both the input power and the output power of a heat pump with less complexity and greater cost efficiency.
In particular, in known systems the evaporation and condensation temperature are measured, while in the present solution the temperatures which are normally measured in a heat pump are used to estimate the saturation evaporation temperature and the saturation condensation temperature to estimate the power of the heat pump.
In an example, said mathematical relations comprise a plurality of functions. Each function of the plurality of functions can link the input power (i.e., the input electrical power) and/or the cooling/thermal power of the heat pump to one out of the first and second temperature parameter, for a predetermined value of the other one of the first temperature parameter and the second temperature parameter. The memory can include interpolation data. The interpolation data are used to perform an interpolation between the plurality of functions. The interpolation between the plurality of functions is performed in response to a detected value of the other one of the first and second temperature parameter.
Therefore, it is possible to obtain the input power and/or the cooling/thermal power for the detected values of the first and second temperature parameter, in real time, using the plurality of functions and if the detected value of the other one of the first and second temperature parameter is not present among the predetermined values of the other one of the first temperature parameter and second temperature parameter, it is possible to perform an interpolation by means of the interpolation data.
In an example, for each function of the plurality of functions, the reference data include predetermined intervals, for said one of the first and second temperature parameter. In an example, for each function of the plurality of functions, the reference data also includes a function defined in each predetermined interval, for the other one of the first and second temperature parameter. In an example, said function defined in each predetermined interval is a linear function. Alternatively, said function defined in each predetermined interval can be another type of polynomial function.
In an example embodiment, the heat pump is an air-to-water heat pump. In this example, the condenser is placed outside a water tank. The condenser is preferably made from a serpentine-wound tube. The serpentine surrounds the water tank. The serpentine is provided with a plurality of coils. Alternatively, the condenser can be placed inside the water tank. The water tank contains water to be heated through heat exchange with the condenser. Furthermore, the second temperature detection device can comprise a first temperature probe, located at the top part of the tank, or a second temperature probe, at the bottom part of the tank, or a third probe located at the outlet of the condenser, or a fourth probe located at the inlet of the condenser. Therefore, according to an example, the temperature of the exchanging fluid is the temperature of the tank water. In an example, the temperature of the working fluid at the condenser is the temperature of the working fluid at the outlet of the condenser. In another example, the temperature of the working fluid at the condenser is the temperature of the working fluid at the inlet of the condenser.
In an embodiment example, the first temperature parameter is representative of the temperature of the fluid which releases the heat flux to the evaporator. In an example, the first temperature parameter can be representative of the temperature of the external air flow flowing through the evaporator.
Furthermore, in such an example, the second temperature parameter is representative of the temperature of the exchanging fluid. In this example, said mathematical relations connect the temperature of the fluid which releases the heat flux to the evaporator and the temperature of the exchanging fluid to the input and/or output power. In another example, the first temperature parameter is representative of the temperature of the fluid which releases the heat flux to the evaporator and the second temperature parameter is representative of the temperature of the working fluid at the condenser. In such an example, said mathematical relations connect the temperature of the fluid which releases the heat flux to the evaporator) and the temperature of the working fluid at the condenser to the input and/or output power.
The mathematical relations connect the temperature of the exchanging fluid to the input and/or output power of the heat pump at predetermined temperatures of the fluid which releases the heat flux to the evaporator. Therefore, it is possible to estimate the input and/or output power using only two temperature detection devices.
It should be noted that if the first temperature parameter is representative of the temperature of the fluid which releases the heat flux to the evaporator and the second temperature parameter is representative of the temperature of the working fluid at the condenser, the mathematical relations connect the temperature of the working fluid at the condenser to the input and/or output power of the heat pump at predetermined temperatures of the fluid which releases the heat flux to the evaporator.
In another example embodiment, the first temperature parameter is the temperature of the working fluid at the evaporator. In such an example, the processing unit is configured to estimate a saturation evaporation temperature parameter of the working fluid. The processing unit is also configured to estimate a saturation condensation temperature parameter of the working fluid. The saturation evaporation temperature parameter and the saturation condensation temperature parameter of the working fluid are estimated based on the first and second temperature parameter, respectively. In an example, the second temperature parameter is representative of the temperature of the exchanging fluid. In another example, the second temperature parameter can be representative of the temperature of the working fluid at the condenser. Said mathematical relations can link the saturation evaporation temperature parameter and the saturation condensation temperature parameter to the input power and/or cooling/thermal power of the heat pump.
In an example, the reference data includes a saturation evaporation temperature correction factor. The reference data can also include a saturation condensation temperature correction factor. The processing unit can be programmed for deriving the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the working fluid based on the first and the second temperature parameters and based on the saturation evaporation temperature correction factor and the saturation condensation temperature correction factor, respectively.
Therefore, unlike the known systems in which the evaporation and condensation temperature are measured, in the present solution the temperatures which are normally measured in a heat pump are used to estimate the saturation evaporation temperature and the saturation condensation temperature to estimate the power of the heat pump.
According to an aspect of the present description, the present invention provides a heat pump system. The heat pump system is preferably an air-to-water heat pump system. The heat pump system is preferably a system for heating water (water heater).
The heat pump system comprises a compressor. The compressor has an inlet. The compressor also includes an outlet. The compressor is configured to increase the pressure of a working fluid. In an example, the working fluid is a refrigerant.
The heat pump system also includes an evaporator. The evaporator has an inlet. The inlet of the evaporator is for receiving the working fluid in liquid state. The evaporator also includes an outlet. The outlet of the evaporator is configured to release the working fluid in gas state. The evaporator receives a heat flux in an adjoining space. The evaporator receives the heat flux from a fluid. Preferably, the evaporator receives an external air flow. The external air flow can be hot air. There is a heat exchange between the evaporator and the external air. The evaporator receives a heat flux from the external air. In another example, the evaporator can exchange heat with a liquid (e.g., water).
The heat pump also includes an expansion valve. The expansion valve is for expanding the working fluid.
The heat pump system includes a condenser. The condenser is configured to receive the working fluid in gas state. The condenser is configured to release liquid low temperature working fluid.
The condenser releases a heat flux to an exchange fluid. The condenser releases the heat flux in a space adjoining the exchanging fluid. The exchanging fluid can be liquid or gas. Preferably the exchanging fluid is water.
The compressor, evaporator, condenser and expansion valve form a refrigeration cycle. The working fluid circulates through said refrigeration cycle. The heat pump system includes an energy monitoring system. The energy monitoring system is according to one or more aspects of the present description.
According to an aspect of the present description, the present invention provides a method for monitoring energy in a heat pump.
The heat pump comprises a compressor. The compressor has an inlet. The compressor also includes an outlet. The compressor is configured to increase the pressure of a working fluid.
The heat pump also includes an evaporator. The evaporator has an inlet. The inlet of the evaporator is for receiving the working fluid in liquid state. The evaporator also includes an outlet. The outlet of the evaporator is for releasing the working fluid in gas state. The evaporator receives a heat flux in an adjoining space. The evaporator receives the heat flux from a fluid. In an example, the evaporator receives an external air flow. Therefore, in an example, the fluid which releases the heat flux to the evaporator is the external air flowing through the evaporator. The external air can be hot.
The heat pump also includes an expansion valve. The expansion valve is for expanding the working fluid.
The heat pump includes a condenser. The condenser receives the working fluid in gas state. The condenser is configured to release liquid low temperature working fluid.
The condenser releases a heat flux in a space adjoining an exchanging fluid.
The compressor, evaporator, condenser and expansion valve form a refrigeration cycle. The working fluid circulates through said refrigeration cycle.
The method comprises a step of detecting a first temperature parameter. The first temperature parameter can be representative of a temperature of the working fluid at the evaporator or of the temperature of the fluid which releases the heat flux to the evaporator. In an example, the first temperature parameter can be representative of the temperature of the external air flow flowing through the evaporator.
The method comprises a step of detecting a second temperature parameter. The second temperature parameter can be representative of the temperature of the exchanging fluid. Alternatively, the second temperature parameter can be representative of the temperature of the working fluid at the condenser.
The method comprises a step of providing a memory. The memory comprises reference data. In an example the reference data are representative of mathematical relations. The reference data are representative of mathematical relations which link the input power and/or the cooling/thermal power to the first and second temperature parameters. The method comprises a step of estimating, by a processing unit, in real time, a value of the input power and/or the cooling/thermal power of the heat pump. The value of the input power and/or the cooling/thermal power of the heat pump is estimated based on the first and second temperature parameters and based on the reference data.
In an example, said mathematical relations include a plurality of functions. Each function of the plurality of functions links the input power and/or the cooling/thermal power to one out of the first and second temperature parameter, for a predetermined value of the other one of the first temperature parameter and the second temperature parameter. In an example, the memory includes interpolation data. The method can include a step of performing an interpolation between the plurality of functions, in response to a detected value of the other one of the first and second temperature parameter.
In an example, for each function of the plurality of functions, the reference data include predetermined intervals, for said one of the first and second temperature parameter. Furthermore, for each function of the plurality of functions, the reference data include a linear function defined in each predetermined interval, for the other one of the first and second temperature parameter. In another example, said functions in each predetermined interval can be non-linear.
In an example, the heat pump is an air-to-water heat pump. The method can include a step of positioning the condenser outside a water tank. The water tank contains water to be heated through heat exchange with the condenser. The method comprises a step of detecting the second temperature parameter through a first temperature probe located at the top part of the tank, or through a second temperature probe at the bottom part of the tank, or through a third probe located at the outlet of the condenser, or through a fourth probe located at the inlet of the condenser.
In an example, the first temperature parameter is representative of the temperature of the fluid which releases the heat flux to the evaporator. In such an example, the second temperature parameter can be representative of the temperature of the exchanging fluid. In this example, said mathematical relations can link the temperature of the exchanging fluid and the temperature of the fluid which releases the heat flux to the evaporator to the input power and/or to the cooling/thermal power.
In another example, the second temperature parameter is representative of the temperature of the working fluid at the condenser.
In this example, said mathematical relations can link the temperature of the working fluid at the condenser and the temperature of the fluid which releases the heat flux to the evaporator to the input power and the cooling/thermal power.
In an example, the method comprises a characterization step. During the characterization step, said mathematical relations are obtained. In an example, a plurality of temperatures of the exchanging fluid are measured during the characterization step. Furthermore, during the characterization step, input power and/or cooling/thermal power values are measured corresponding to each of the measured temperatures of the exchanging fluid. In particular, input power and cooling/thermal power values corresponding to each of the measured temperatures of the exchanging fluid are detected at predetermined temperatures of the fluid which releases the heat flux to the evaporator, so that the mathematical relations link the temperature of the exchanging fluid to the input power of the heat pump at the predetermined temperatures of the fluid which releases the heat flux to the evaporator. It should be noted that if the second temperature parameter is representative of the temperature of the working fluid at the condenser, during the characterization step a plurality of temperatures of the working fluid at the condenser and input power and/or cooling/thermal power values corresponding to each of the measured temperatures of the working fluid at the condenser at predetermined temperatures of the fluid which releases the heat flux to the evaporator are measured.
In another example, the first temperature parameter is the temperature of the working fluid at the evaporator. The second temperature parameter is representative of the temperature of the exchanging fluid or of the temperature of the working fluid at the condenser. In this example, the method can include a step of estimating, by the processing unit, a saturation evaporation temperature parameter and a saturation condensation temperature parameter of the working fluid. The saturation evaporation temperature parameter and the saturation condensation temperature parameter of the working fluid are estimated based on the first and second temperature parameter, respectively. Furthermore, the mathematical relations link the saturation evaporation temperature parameter and the saturation condensation temperature parameter to the input power and/or cooling/thermal power of the heat pump.
In an example, the reference data includes a saturation evaporation temperature correction factor. The reference data can also include a saturation condensation temperature correction factor.
The method can include a step of correcting, by the processing unit, the first and the second temperature parameter. The first and second temperature parameters are corrected based on the saturation evaporation temperature correction factor and the saturation condensation temperature correction factor, respectively.
The method can comprise a step of deriving the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the working fluid based on the corrected first and second temperature parameter, respectively.
These and other features will become more apparent from the following description of a preferred embodiment, illustrated purely by way of nonlimiting example in the accompanying drawings, wherein:

figure 1 illustrates a heat pump,
figures 2-4 illustrate mathematical relations used by the energy monitoring system according to the present description.

With reference to the accompanying drawings, a heat pump is indicated by the number 100. A heat pump is a device capable of heating a space by transferring thermal energy from the outside using a refrigeration cycle. Many heat pumps can also operate in the opposite direction, cooling the space by removing heat from the enclosed space and repelling it outside.
In heating mode, a refrigerant is compressed and as a result, the refrigerant becomes hot. This thermal energy can be transferred to an internal unit (located in the space to be heated). After being moved externally again, the refrigerant is decompressed and evaporated; thus, the refrigerant has lost a part of its thermal energy and returns colder than the environment. Now the refrigerant can absorb the surrounding energy from the air before the process is repeated. Compressors, fans and pumps operate with electricity. In the refrigeration cycle, the refrigerant absorbs heat from one space, it is compressed and thus increases its temperature before being released into another space.
The heat pump 100 comprises a compressor 101. The compressor 101 has an inlet. The compressor also includes an outlet. The compressor 101 is configured to increase the pressure of a working fluid. The working fluid is a refrigerant.
The heat pump 100 also includes an evaporator 102. The evaporator has an inlet I. The inlet I of the evaporator 102 is for receiving the refrigerant in liquid state. The evaporator 102 also includes an outlet O. The outlet of the evaporator is for releasing the refrigerant in gas state. The evaporator receives a heat flux in an adjoining space. The evaporator receives the heat flux from a fluid A.
In an example, the evaporator 102 receives an external air flow A. The external air can be hot. In an example, the fluid which releases the heat flux to the evaporator is the external air flowing through the evaporator.
The evaporator can include a fan for sucking the external air A.
The heat pump 100 also includes an expansion valve 103. The expansion valve 103 is for expanding the refrigerant.
The heat pump includes a condenser 104. The condenser is configured to receive the refrigerant in gas state. The condenser is configured to release the liquid low temperature refrigerant.
The condenser releases a heat flux to an exchange fluid.
The compressor 102, the evaporator 102, the condenser 104 and the expansion valve 103 form the refrigeration cycle. The refrigerant circulates through said refrigeration cycle.
Furthermore, the heat pump can include an inversion valve which selects between heating and cooling modes. The heat pumps have two heat exchangers, one associated with the external heat source and the other with the internal heat. In heating mode the external heat exchanger is the evaporator 102 and the internal one is the condenser 104; in cooling mode the roles are reversed. In an example, the heat pump 100 is an air-to-water heat pump. The heat pump can also be water-to-air, air-to-air or water-to-water or water-to-air. When the heat pump 100 is an air-to-water heat pump (and in heating mode), the condenser 104 is located inside or outside a water tank T. The water tank contains water to be heated through heat exchange with the condenser 104.
The heat pump 100 can also have a hot gas valve 106. The hot gas valve is a bypass valve which provides a load on the evaporator, introducing a portion of high pressure and high temperature gas into the evaporator side of the heat pump.
The heat pump can also include a filter 107. The filter is located between the expansion valve 103 and the condenser 104.
The energy monitoring system comprises a sensing system. The sensing system comprises a first temperature detection device 105A. The first temperature detection device 105A detects a first temperature parameter. The first temperature detection device can include a first plurality of temperature probes Pa, Pb, Pc and Pd. In an example, a first probe Pa of the first plurality of probes is located at the inlet I of the evaporator 102. The first probe Pa of the first plurality of probes detects the temperature of the refrigerant at the inlet of the evaporator. Furthermore, a second probe Pb of the first plurality of probes can be located at the outlet O of the evaporator 102. The second probe Pb of the first plurality of probes detects the temperature of the refrigerant at the outlet of the evaporator. A third probe Pc of the plurality of probes can be located inside the evaporator 102. The third probe Pc of the first plurality of probes detects the defrosting temperature. A fourth probe Pd of the first plurality of probes of the first temperature detection device can detect the temperature of the fluid temperature which releases the heat flux to the evaporator A. In an example, the first temperature parameter can be representative of the temperature of the external air flow flowing through the evaporator.
It should be noted that the first temperature detection device 105A detects one or more temperature values. One or more temperature values detected by the first temperature detection device are used to obtain the first temperature parameter. In particular, the temperature values detected by the first temperature detection device are detected by the first plurality of temperature probes Pa, Pb, Pc and Pd.
In an embodiment example, the first temperature parameter is representative of a temperature of the refrigerant at the evaporator 102. In this example, the first temperature parameter can be obtained from the temperature detected by the first probe Pa, the second probe Pb or the third probe Pc of the first plurality of probes. Preferably, the first temperature parameter is obtained from the temperature value detected by the first probe Pa of the first plurality of probes.
In another embodiment example, the first temperature parameter is representative of the temperature of the fluid which releases the heat flux to the evaporator. In an example, the first temperature parameter can be representative of the temperature of the external air flow flowing through the evaporator. In such an example, the first temperature parameter is obtained from the value detected by the fourth probe Pd of the first plurality of probes. The sensing system includes a second temperature detection device 105B. The second temperature detection device detects a second temperature parameter.
The second temperature detection device can include a second plurality of temperature probes P1, P2, Pe, Pf.
It should be noted that the second temperature detection device 105B detects one or more temperature values. One or more temperature values detected by the second temperature detection device are used to obtain the second temperature parameter. In particular, the temperature values detected by the second detection device are detected by the second plurality of temperature probes P1, P2, Pe, Pf.
If the heat pump 100 is an air-to-water heat pump, the second temperature detection device 105B can comprise a first temperature probe P1 located at the top part of the tank T. The second temperature detection device 105B can also comprise a second temperature probe P2, at the bottom part of the tank T. The second temperature detection device 105B can also comprise a third temperature probe Pf located at the outlet of the condenser to measure the temperature of the refrigerant at the outlet of the condenser. The second temperature parameter can be representative of the temperature of the exchanging fluid or the temperature of the refrigerant at the condenser. The second temperature parameter can be obtained from the value detected by the first temperature probe P1 or by the second temperature probe P2 of the second temperature detection device 105B or the third probe Pf of the second temperature detection device 105B. The second temperature detection device 105B can include a fourth probe Pe. The fourth probe Pe of the second temperature detection device 105B can be located at the outlet of the compressor 101 to measure the temperature of the refrigerant at the outlet of the compressor. In another example, the second temperature parameter can be obtained from the value detected by the fourth temperature probe Pe of the second temperature detection device.
The energy monitoring system can comprise a memory. The memory contains reference data. The reference data are representative of mathematical relations which link the input power and/or the cooling/thermal power (i.e., the output power or capacity of the heat pump) to the first and second temperature parameters.
The energy monitoring system comprises a processing unit. The processing unit is connected to the sensing system and to the memory. The processing unit is programmed to derive, in real time, an estimated value of the input power and cooling/thermal power of the heat pump 100. The value of the input power and cooling/thermal power of the heat pump 100 is estimated by means of the processing unit based on the first and second temperature parameters and based on the reference data.
The term "real time" refers to a process of analysing data in input as soon as they enter a data processing system.
Said mathematical relations can comprise a plurality of functions. Each function of the plurality of functions links the input power and cooling/thermal power to one out of the first and second temperature parameter, for a predetermined value of the other one of the first temperature parameter and the second temperature parameter. The functions can be a plurality of graphs which illustrate the input power and cooling/thermal power of the heat pump in association with one out of the first and second temperature parameter, for predetermined values of the other one of the first temperature parameter and the second temperature parameter. The memory can include interpolation data, for performing an interpolation between the plurality of functions. The interpolation is performed in response to a detected value of the other one of the first and second temperature parameter. That is, the first and second temperature parameter are detected by the first and second temperature detection device. The plurality of functions is used by the processing unit to estimate the value of the input power and cooling/thermal power for the detected values of the first and second temperature parameter. As explained above, the functions provide graphs which illustrate the input power and cooling/thermal power of the heat pump as a function of one out of the first and second temperature parameter, for predetermined values of the other one of the first temperature parameter and the second temperature parameter. If the detected value of the other one of the first temperature parameter and the second temperature parameter is not present among predetermined values of the other one of the first temperature parameter and the second temperature parameter provided by the graphs, the processing unit performs an interpolation between the predetermined values provided by the functions to obtain the input power and cooling/thermal power. Figures 2 and 4 illustrate an example of said functions.
In an example, for each function of the plurality of functions, the reference data include predetermined intervals, for said one of the first and second temperature parameter. Furthermore, for each function of the plurality of functions, the reference data include a linear or polynomial function defined in each predetermined interval, for the other one of the first and second temperature parameter.
In an embodiment example, the first temperature parameter is representative of the temperature of the fluid which releases the heat flux to the evaporator. In an example, the first temperature parameter can be representative of the temperature of the external air flow flowing through the evaporator. Therefore, in such an example the first temperature parameter is obtained by means of the temperature value detected by the fourth probe Pd of the first plurality of probes. Furthermore, in this example said mathematical relations connect the temperature of the fluid which releases the heat flux to the evaporator A and the temperature of the exchanging fluid (or the temperature of the refrigerant at the condenser) to the input power. Furthermore, said mathematical relations connect the temperature of the fluid which releases the heat flux to the evaporator and the temperature of the exchanging fluid (or the temperature of the refrigerant at the condenser) to the output power. The mathematical relations can be obtained in a characterization step. The characterization step is performed before the operation of the energy monitoring system of the heat pump. In an example, during the characterization step, the energy monitoring system is executed and to obtain each function of the plurality of functions, at a fixed temperature of the external hot air flow, the input and/or output power of the heat pump at a respective detected temperature of the exchanging fluid (or the temperature of the refrigerant at the condenser) is detected. Such an operation (characterization) is repeated for a plurality of temperatures of the external hot air flow. Therefore, the relations provide the functions which connect the temperature of the exchanging fluid (or the temperature of the refrigerant at the condenser) to the input power and cooling/thermal power of the heat pump at predetermined temperatures of the external hot air flow.
It should be noted that the values of the temperature of the exchanging fluid provided by the functions fall within an interval which covers the minimum and maximum temperature of the temperature of the exchanging fluid during the operation of the heat pump. As explained above, if the detected temperature of the fluid flow which releases the heat flux to the evaporator is not present among the predetermined values provided by said functions, the input and/or output power is estimated by means of interpolation. Figure 4 illustrates the relations which link the temperature of the exchanging fluid to the input power for two predetermined temperatures (0 and 42ºC) of the temperature of the fluid which releases the heat flux to the evaporator. In the example of figure 4, said fluid is the external air flowing through the evaporator.
In another example embodiment, the first temperature parameter is the temperature of the refrigerant at the evaporator. Therefore, in such an example, the first temperature parameter is detected by one of the first, second or third temperature probes of the first plurality of probes of the first temperature detection device 105A. The processing unit is configured to estimate a saturation evaporation temperature parameter and a saturation condensation temperature parameter of the refrigerant, based on the first and second temperature parameters, respectively.
In particular, the temperature of the refrigerant at the evaporator and the temperature of the exchanging fluid (or the temperature of the refrigerant at the condenser) are used to estimate the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the refrigerant. However, the temperature of the refrigerant at the evaporator and the temperature of the exchanging fluid must be corrected, to obtain a sufficiently precise value. The reference data include a saturation evaporation temperature correction factor and a saturation condensation temperature correction factor. Furthermore, the processing unit is programmed for deriving the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the refrigerant based on the first and the second temperature parameters and based on the saturation evaporation temperature correction factor and the saturation condensation temperature correction factor, respectively. That is, the processing unit corrects the temperature of the refrigerant at the evaporator and the temperature of the exchanging fluid (or the temperature of the refrigerant at the condenser) using the saturation evaporation temperature correction factor and the saturation condensation temperature correction factor, respectively, to obtain the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the refrigerant. Furthermore, the processing unit estimates the input and/or output power of the heat pump using the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the refrigerant and the mathematical relations.
The mathematical relations link the saturation evaporation temperature parameter and the saturation condensation temperature parameter to the input and/or output power of the heat pump. In particular, in this example, said relations provide graphs illustrating the input and/or output power as a function of the saturation evaporation temperature for predetermined values of saturation condensation temperature. The functions include a plurality of curves (figures 2 and 3); each curve corresponds to a predetermined value of the saturation condensation temperature. Furthermore, with good approximation, all the curves can be made linear in sections according to predetermined intervals. The reference data can include, for each relation, predetermined intervals for the saturation evaporation temperature and each curve of said curves can be made linear in each interval of the predetermined intervals (e.g., from -15 to -5 ºC). Therefore, each curve can be made linear in sections and each section can be represented according to the equation of the line y=mx+q. Therefore, the values of the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the refrigerant are detected by the processing unit using the first and second temperature parameters and the saturation evaporation temperature correction factor and the saturation condensation temperature correction factor, respectively. Subsequently, using the values of the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the refrigerant and using the mathematical relations (reference data), the input and/or output power is estimated. If the estimated value of the saturation condensation temperature parameter is not present among the predetermined values provided by the relations (the curves), an interpolation is performed between the predetermined values to obtain the input and/or output power.
Furthermore, it is possible to calculate the value of the thermal power of the heat pump using the estimated values for the input power and the output power (output cooling power). In particular, the following formula is used to calculate the thermal power generated by the compressor: $Ptcp = Pfcp + k * Pacp$
where k is a coefficient obtained from experimental tests which takes into account the electrical input power dispersed in the environment and not transferred to the fluid (air or water) used for condensation.

Claims

An energy monitoring system for a heat pump (100), wherein the heat pump (100) comprises:
- a compressor (101), having an inlet (I) and an outlet (o), for increasing the pressure of a working fluid;

- an evaporator (102), having an inlet (I) for receiving the working fluid in liquid state and an outlet (O) for releasing the working fluid in gas state, wherein the evaporator (102) receives a heat flux in an adjoining space, from a fluid (A);

- an expansion valve (103) for expanding the working fluid,

- a condenser (104) for receiving the working fluid in gas state and for releasing liquid low temperature working fluid, wherein the condenser (104) releases a heat stream to an adjoining space to exchange heat with an exchanging fluid,
wherein the compressor (101), the evaporator (102), the condenser (104), and the expansion valve (103) form a refrigeration cycle through which the working fluid circulates,
the energy monitoring system comprising:
- a sensing system, having
a first temperature detection device (105A), for detecting a first temperature parameter, representative of either a temperature of the working fluid at the evaporator (102) or of the temperature of the fluid (A) which releases the heat flux to the evaporator (102),

a second temperature detection device (105B), for detecting a second temperature parameter representative of either the temperature of the exchanging fluid or of the temperature of the working fluid at the condenser (104);

- a memory containing reference data, the reference data being representative of mathematical relations which link the input power and/or the output power of the heat pump to the first and second temperature parameters;

- a processing unit, connected to the sensing system and to the memory and programmed to derive, in real time, an estimated value of the input power and/or the output power of the heat pump (100), based on the first and the second temperature parameters and based on the reference data.
The energy monitoring system according to claim 1, wherein said mathematical relations include a plurality of functions, wherein each function of the plurality of functions links the input power and/or the output power to one out of the first and second temperature parameter, for a predetermined value of the other one of the first temperature parameter and the second temperature parameter, and wherein the memory includes interpolation data, for performing an interpolation between the plurality of functions, responsive to a detected value of the other one of the first and second temperature parameter.
The energy monitoring system according to claim 2, wherein, for each function of the plurality of functions, the reference data include
predetermined intervals, for said one of the first and second temperature parameter and

a linear function in each predetermined interval, for the other one of the first and second temperature parameter.
The energy monitoring system according to any of the previous claims, wherein the heat pump (100) is an air-to-water heat pump and wherein the condenser (104) is placed outside a water tank (T), containing water to be heated through heat exchange with the condenser (104), wherein the second temperature detection device (105B) includes a first temperature probe (P1) located at a top part of the tank (T) or a second temperature probe (P2) at the bottom part of the tank (T) or a third temperature probe (Pf) at the outlet of the condenser (104) or a fourth temperature probe (Pe) at the inlet of the condenser (104).
The energy monitoring system according to any of the previous claims, wherein the first temperature parameter is representative of the temperature of the fluid (A) which releases the heat flux to the evaporator (102), and the second temperature parameter is representative of the temperature of the exchanging fluid and wherein said mathematical relations link the temperature of the exchanging fluid and the temperature of the fluid (A) which releases the heat flux to the evaporator to the input power and/or the output power, wherein the mathematical relations link the temperature of the exchanging fluid to the input power and/or the output power of the heat pump at predetermined temperatures of the fluid (A) which releases the heat flux to the evaporator.
The energy monitoring system according to any of the previous claims from 1 to 4, wherein the first temperature parameter is the temperature of the working fluid at the evaporator (102) and wherein the processing unit is configured to estimate a saturation evaporation temperature parameter and a saturation condensation temperature parameter of the working fluid, based on the first and the second temperature parameters, respectively, wherein the mathematical relations link the saturation evaporation temperature and the saturation condensation temperature parameter to the input power and/or the output power of the heat pump, wherein the reference data includes a saturation evaporation temperature correction factor and a saturation condensation temperature correction factor, wherein the processing unit is programmed for deriving the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the working fluid based on the first and the second temperature parameters and based on the saturation evaporation temperature correction factor and the saturation temperature condensation correction factor, respectively.
A heat pump system (100) comprising:
- a compressor (101), having an inlet (I) and an outlet (o), for increasing the pressure of a working fluid;

- an evaporator (102), having an inlet (I) for receiving the working fluid in liquid state and an outlet (O) for releasing the working fluid in gas state, wherein the evaporator (102) receives a heat flux in an adjoining space, from a fluid (A);

- an expansion valve (103) for expanding the working fluid,

- a condenser (104) for receiving the working fluid in gas state and for releasing liquid low temperature working fluid, wherein the condenser (104) releases a heat stream to an adjoining space to exchange heat with an exchanging fluid, wherein the compressor (101), the evaporator (102), the condenser (104), and the expansion valve (103) form a refrigeration cycle through which the working fluid circulates,

- an energy monitoring system, wherein the energy monitoring system is according any of the previous claims,
wherein the heat pump system is an air-to-water heat pump system.
A method for monitoring energy in a heat pump (100), wherein the heat pump (100) comprises:
- a compressor (101), having an inlet (I) and an outlet (O), for increasing the pressure of a working fluid;

- an evaporator (102), having an inlet (I) that receives the working fluid in liquid state and an outlet (O) and releases the working fluid in gas state, wherein the evaporator (102) receives a heat flux in an adjoining space, from a fluid (A);

- an expansion valve (103) that expands the working fluid,

- a condenser (104) that receives the working fluid in gas state and releases liquid low temperature working fluid, wherein the condenser (104) releases a heat stream to an adjoining space to exchange heat with an exchanging fluid,
wherein the compressor (101), the evaporator (102), the condenser (104), and the expansion valve (103) form a refrigeration cycle through which the working fluid circulates,
the method comprising the following steps:
- detecting a first temperature parameter, representative of either a temperature of the working fluid at the evaporator or the temperature of the fluid (A) which releases the heat flux to the evaporator (102),

- detecting a second temperature parameter representative of either the temperature of the exchanging fluid or of the temperature of the working fluid at the condenser (104);

- providing a memory including reference data, the reference data being representative of mathematical relations which link the input power and/or the output power to the first and second temperature parameters;

- by a processing unit, estimating, in real time, a value of the input power and/or the output power of the heat pump (100), based on the first and the second temperature parameters and based on the reference data.
The method according to claim 8, wherein said mathematical relations include a plurality of functions, wherein each function of the plurality of functions links the input power and/or the output power to one out of the first and second temperature parameter, for a predetermined value of the other one of the first temperature parameter and the second temperature parameter, and wherein the memory includes interpolation data, wherein the method includes a step of performing an interpolation between the plurality of functions, responsive to a detected value of the other one of the first and second temperature parameter.
The method according to claim 9, wherein, for each function of the plurality of functions, the reference data include
predetermined intervals, for said one of the first and second temperature parameter and

a linear function in each predetermined interval, for the other one of the first and second temperature parameter.
The method according to any of the previous claims from 8 to 10 wherein the heat pump (100) is an air-to-water heat pump and wherein the method includes the following steps:
- placing the condenser (104) outside a water tank (T) which contains water to be heated through heat exchange with the condenser (104),

- detecting the second temperature parameter through a first temperature probe (P1) at a top part of the tank (T) or, through a second temperature probe (P2) at the bottom part of the tank (T), or through a third temperature probe (Pf) at the outlet of the condenser (104) or through a fourth temperature probe (Pe) at the inlet of the condenser (104).
The method according to any of the previous claims from 8 to 11, wherein the first temperature parameter is representative of the temperature of the fluid (A) which releases the heat flux to the evaporator (102), and the second temperature parameter is representative of the temperature of the exchanging fluid, and wherein said mathematical relations link the temperature of the exchanging fluid and the temperature of the fluid (A) which releases the heat flux to the evaporator to the input power and/or output power.
The method according to claim 12, wherein the method incudes a characterization steps during which the mathematical relations are obtained and wherein during the characterization step, a plurality of temperatures of the exchanging fluid are measured and values of input power and/or output power corresponding to each of the measured temperatures of the exchanging fluid are detected at predetermined temperatures of the fluid (A) which releases the heat flux to the evaporator, so that the mathematical relations link the temperature of the exchanging fluid to the input power and/or output power of the heat pump at the predetermined temperatures of the fluid (A) which releases the heat flux to the evaporator.
The method according to any of the previous claims from 8 to 11, wherein the first temperature parameter is the temperature of the working fluid at the evaporator (102) and wherein the method includes a step of estimating, by the processing unit, a saturation evaporation temperature parameter and a saturation condensation temperature parameter of the working fluid, based on the first and the second temperature parameters, respectively, wherein the mathematical relations link the saturation evaporation temperature and the saturation condensation temperature parameter to the input power and/or output power of the heat pump, wherein the reference data includes a saturation evaporation temperature correction factor and a saturation condensation temperature correction factor, wherein the method includes the following steps:
- correcting, by the processing unit, the first and the second temperature parameters based on the saturation evaporation correction factor and the saturation condensation correction factor, respectively,

- deriving the saturation evaporation temperature parameter and the saturation condensation temperature parameter of the working fluid based on the corrected first and the second temperature parameters.