FIELD

The present invention relates to a heat pump arrangement.

BACKGROUND

Heat pumps are used to improve extraction of heat from a media, such as liquid or air.

Even though heat pumps are widely used and the technology has developed over decades, there is still room for improvements. In some aspects, the currently used solutions are complex, expensive and take are inconvenient to install and use.

SUMMARY

The object of the invention is to provide an improved heat pump arrangement to alleviate at least some of the disadvantages associated with the prior solutions.

The object is achieved with an invention defined in the independent claim. Some advantageous embodiments have been disclosed in the dependent claims.

DRAWINGS

The invention and some advantageous embodiments have been illustrated in the accompanying drawings, where

Figure 1 shows an illustration of a heat circuit;

Figure 2 shows a second illustration of a heat circuit;

Figure 3 shows an embodiment of an arrangement according to the invention.

DESCRIPTION OF SOME EMBODIMENTS

Figure 1 shows an example of a heat pump circuit 100. To the circuit there is associated a heat source providing input heat Qin to the system. The heat source may be ground, for instance, wherein liquid is circulated in a piping arranged to the ground for collecting heat stored in the ground.

The input heat Qin is lead to an evaporator/vaporizer 102 belonging to the heat pump circuit 100. As input to the evaporator liquid is received in the evaporator and the due to the input heat, the circulating fluid/liquid vaporizes. After the evaporator 102, the gas is lead to a compressor 104 for increasing the pressure and temperature of the gas. The compressor is operated by a motor 110.

The gas whose pressure has been raised is then lead to a condenser 106, which may be implemented as a heat exchanger with a heat utilization circuit (not shown) receiving the output heat Qout. The heat utilization circuit may be heat distribution piping of a utility, for instance. In the condenser 106, due to the released heat Qout, the input gas is at least partly converted to liquid form again. The temperature of the liquid may be further reduced in the choke/th rottie 108 whereafter the process starts again by inputting the liquid to the evaporator 102.

Figure 2 shows another heat pump arrangement. The basic arrangement and operation of the heat circuits correspond to the one presented in Figure 1. In Figure 2, however, there are two closed sub-circuits each having their own circulating fluid. The two sub-circuits are connected via a heat exchanger 206, which operates as a condenser for the lower sub-circuit 202-204-206-208, and as an evaporator for the higher sub-circuit 206-214-216-218.

Figure 3 shows an embodiment of heat pump arrangement 300 of the invention. The heat pump arrangement comprises a compression unit 330, which is arranged to receive energy from a heat source 350 and eventually output energy to an energy consumer 352. Without limiting the invention thereto, the heat source 350 may be an ice-hall where heat is extracted from icing of the ice, and the heat consumer 352 is a swimming hall utilizing the received energy in warming the swimming hall and the washing water, for instance, used therein.

The compression unit 330 comprises a power source 332 for rotating a shaft 334 of the power source. The power source may comprise a combustion engine, an electric motor or a hydraulic motor, for instance. The compression unit 330 is arranged to receive heat from a heat source 340. To the shaft 334 are operatively connected three compressors 304, 314 and 324. By operational connection is meant here that the rotation of the shaft 334 causes the compressors 304, 314 and 324 to perform compression of gas in their respective circuits.

Referring to the situation of Figure 2, the compressor 304 corresponds to the compressor 204 of the first sub-circuit, and the compressor 314 corresponds to the compressor 214 of Figure 2. The heat exchanger 306 corresponds to the heat exchanger 206 of Figure 2. The heat exchanger 336, however, has no counter-part in Figure 2 as Figure 2 only has two sub-circuits and Figure 3 shows three sub-circuits in cascade arrangement with respect to each other.

The embodiments of the invention include arrangements where at least two compressors 304, 314 are operationally connected to the same motor shaft 334. The number of compressors can range from two up to six compressors. In one embodiment the compressors may be scroll compressors, however not limiting the invention to any specific compressor type but any type compressors may be applied in the system.

In one embodiment all the compressors are arranged for synchronous operation with respect to each other meaning that the compressors operate by having a direct dependence to the rotation speed of the shaft 334. In such an embodiment, all the compressors may be operated at the same rotation speed being the rotation speed of the shaft.

In other embodiments, the compressors may be arranged to rotate at different rotation speeds. In some embodiments, the difference between the rotation speeds of the compressors may be fixed, that is, it is always the same. In such embodiments, none or one or more of the compressors may operate at the rotation speed of the shaft, and at least one of the other compressors has a fixed higher or lower rotation speed than another compressor in the group of compressors.

In some other embodiments, the difference of the rotation speeds between at least two compressors in the group of compressors is adjustable. It may be provided, that the adjustment possibility is continuously available. During operation it may also be arranged that some of the compressors are switched off while one or more of the other compressors are still operating.

The different operation speeds for the compressors may be arranged by gear/gearing or other control mechanism such as a switch between the shaft and one or more compressors and/or or different shaft portions.

For this purpose, Figure 3 shows gears 342, 344 arranged on the shaft. That is, the shaft 334 may be divided into portions 334A, 334B, 334C, which are separately controllable by the gears whereby different rotation speeds may be arranged to different shaft portions and thereby further to different compressors according to heat production and storage needs of the system. Figure 3 shows also gears/switches 346, 347 and 348 arranged between the shaft 334 and the com- pressors, which may also be used for changing the rotation speeds of the respective compressors, or even couple a compressor off use while one or more of the other compressors is working.

It is to be noted that the speed control devices 342, 344 arranged on the shaft and the speed control devices 346, 347 and 348 may be alternative to each other or they may be complementary to each other such that there are provided e.g. gears both on the shaft and between the shaft and at least one of the compressors.

There is provided a control device 340 for controlling the gears 342, 344, 346, 347 and 348. The control device 340 may have a user interface for the user setting the speeds of the shafts or compressors. Alternatively, or additionally, the user interface may allow the user to set heat production targets and the system will automatically adjust the compressor speeds accordingly.

There may be provided a heat storage unit per each circuit corresponding to the compressors 304, 314 and 324. The heat storage unit may comprise a phaser, for instance. The heat storage unit may temporarily store energy of a circuit if not all compressors are needed. By way of an example, if the heat consumer 352 does not need more energy, and still it would be desirable to run the compressors 304 and 314, whilst having the compressor 324 stopped, the excess heat could be stored to a phaser connected to the circuit having the compressor 314. Later on, when heat energy is requested by the heat consumer 352, the compressor 324 alone of the compressors might be operated by utilizing the heat that has been earlier stored to a heat storage.

Thus, in one embodiment, the arrangement comprises a control unit for controlling a first compressor to operate while controlling the adjacent following second compressor to be stopped or to operate with reduced speed such that more heat is being accumulated to a first circuit corresponding to the first compressor than what is needed by a second circuit corresponding to the second compressor, the arrangement further comprising a heat storage associated with the first circuit for storing the excess energy for later use. By way of an example, if the arrangement has three compressors arranged into a sequence as shown in Figure 3, there may be provided heat storages for the first circuit and for the second circuit for storing excess heat produced by the associated circuits. In an exemplary case, if the heat consumer does not temporarily need or wish to have more heat energy, the third compressor may be stopped or it may operate at a very low speed. The first and/or second compressors may operate normally, however, and the heat produced by these may be stored to a heat storage associated with the second circuit, for instance.

In an embodiment, the arrangement comprises a heat storage for storing heat energy, and the arrangement is configured to operate a compressor by heat energy recovered from the heat storage while having one or more compressors of previous heat circuits stopped or operating at a lower operation speed that what would be needed for standard operation of the arrangement. Referring to the previous example, in an embodiment the third compressor may now be operated while having the first and second compressors stopped or operating at a low speed. The heat circuit of the third compressor may now receive the input energy from the heat storage of the second circuit where the heat energy was previously stored in.

In one embodiment, the motor unit 330 is arranged as a single apparatus having its own housing which may be incorporating within the walls of the housing the motor 332, the motor shaft 334, the compressors 304, 314, 324 and the heat exchangers 306, 336. This is highlighted by the dashed line around the motor unit 330. That is, the motor unit 330 may comprise the motor 332 and the compressors 304, 314, 324 arranged to the shaft 334 of the motor. The motor unit may comprise inlets and outlets for connecting to the fluid circuits of the respective compressors. For instance, there may be provide a fluid inlet and a fluid outlet for the circuit of the compressor 324 and similarly for other compressors.

Figure 3 also shows a drive or control unit 338 for controlling the motor 332.

In one embodiment, the control of the motor may be arranged based on the highest demanding circuit. There may be provided gas pressure measurement after each compressor, and the control of the motor rotation speed may be based on these measurements. The user of the system may set an overall heat production demand for the system and this may result into different rotation speed estimates for the compressors. For instance, in a three-compressor system the first compressor may have a request to have a rotation speed X, the second compressor may have a request 1 ,1X, and the third compressor may have a rotation speed request 1.2X. In such a scenario, if all the three compressors would be directly connected to the shaft without gearing, the system would opt for rotating the shaft according to the highest demand being 1 ,2X. The invention provides a plurality of advantages. One advantage is simplicity of the arrangement and also that less space is needed as there is only one motor 332 needed, which can operate several compressors. Only one motor simplifies also the installation and the maintenance of the system as there are less components to service and less piping work to carry out. The small number of components (motor, drive unit etc.) provides also savings in the total cost of the system.

One important advantage is that all the cold technology is in one apparatus, such as the motor unit 330 making the system safer and reduces the risk for leakages of the fluids used in the system.

During use, the invention provides for the advantage of having smaller mechanical losses due to a smaller number of mechanical components.

The invention enables using air heat pumps in colder countries where generally one circuit heat pump can no longer provide energy at temperatures below -20 Celsius. The present invention may take, at temperature -38 Celsius, being the lowest sizing temperature in Finland, take the second compressor in use and achieve a COP (Coefficient of Performance) between 1 .5 to 2.5 or better. Thus, by means of the solution according to the embodiments, the performance at very low temperatures can be improved when compared to existing solutions.

Even though the embodiments disclose the arrangement to be used for heat generation, the arrangement may alternatively and reversely be arranged for cooling purposes.

In an aspect there is provided a heat pump arrangement, the arrangement comprising at least two heat circuits, wherein each circuit is arranged to circulate a fluid specific for the circuit, and each circuit comprises an evaporator for evaporating the fluid from liquid to gas, a compressor for compressing the evaporated gas to increase the pressure of the gas, and a condenser for condensing the gas back to liquid, which heat circuits are arranged in cascade arrangement such that the evaporator of one heat circuit is operatively connected to a condenser of an adjacent heat circuit. The compressors are connected to a common power source for operating the compressors. In the embodiments, the heat circuits are arranged to cascade arrangement meaning that the heat circuits form a chain of heat circuits where the heat circuits and the end of the chain are operatively connected to one other heat circuit whereas the heat circuits in other positions of the chain than the ends are operatively connected to two other heat circuits. Each of the heat circuit has a compressor for compressing the fluid circulating in the closed circuit. In the embodiments, at least two of the compressors of the circuits are connected to the same power source, such as a motor.

In the embodiments, the power source comprises a motor and a motor shaft rotatable by the motor, and the compressors of each of the at least two heat circuits are mechanically connected to the motor shaft. By mechanical connection it is meant that the compressors may be directly connected to the shaft such that they follow the rotation speed of the shaft. Alternatively, the compressors may be connected to the shaft via gearing such that their rotation speeds are different and they follow the rotation speed as determined by the gearing.

In preferred embodiments, the arrangement comprises between 2 to 6 compressors arranged to the same motor shaft.

In some embodiments, the compressors are connected to the motor shaft such that the rotation speeds of the compressors are adjustable, whereby the rotation speeds of at least two compressors may be adjusted to the same or different from each other.

In some embodiments, at least one of the at least two compressors is connected to the motor shaft via gearing such that the rotation speed of the compressor corresponds to the rotation speed of the shaft as determined by the gearing. In some embodiments, there may be one or more compressors connected directly to the shaft and one or compressors mechanically connected to the shaft via gearing.

In some embodiments, at least one of the at least two compressors is connected to the motor shaft via a switch such that the compressor can be switched off from operation while the shaft is rotating.

In some embodiments, the shaft is divided into two or more shaft portions, which are connected to each other by gearing to allow the different shaft portions to rotate by different rotation speed to each other.

In some embodiments, the arrangement comprises a control unit for controlling the gearing and/or switch such that the compressor connected to the shaft via the gearing provides a heat output according to a current heat output need from the arrangement. The control unit may be configured to control the rotation speed of the motor and the shaft based on the request of such a compressor of the at least two compressors requesting the highest rotation speed. The other compressors may be adjusted to have the same or lower rotation speed. The first heat circuit of the at least two heat circuits is operatively connected to a heat source for receiving heat from the heat source, and the last heat circuit of the at least two heat sources is operatively connected to a heat consumer for conveying heat from the last heat circuit to the heat consumer.

The arrangement comprises a control unit for controlling a first compressor to operate while controlling the adjacent following second compressor to be stopped or to operate with reduced speed such that more heat is being accumulated to a first circuit corresponding to the first compressor than what is needed by a second circuit corresponding to the second compressor, the arrangement further comprising a heat storage associated with the first circuit for storing the excess energy for later use.

The arrangement comprises a heat storage for storing heat energy, and the arrangement is configured to operate a compressor by heat energy recovered from the heat storage while having one or more compressors of previous heat circuits stopped or operating at a lower operation speed that what would be needed for standard operation of the arrangement.

In an aspect, there is provided a method, comprising steps of circulating fluids in at least two closed heat circuits, each heat circuit comprising the phases of evaporating the fluid from liquid to gas, compressing the evaporated gas to increase the pressure of the gas, and condensing the gas back to liquid, which heat circuits are arranged in cascade arrangement such that the evaporator of one heat circuit is operatively connected to a condenser of an adjacent heat circuit. In the method, the compressors of the at least two heat circuits are operated by having the compressors connected to a common power source.

It is evident that when the technology develops, the invention can be implemented in other ways. The invention and the embodiments are thus not limited to the preceding embodiments but can vary in the scope of the attached claims.