The invention relates to a multi-mode refrigeration system. Background

IPC class F25 discloses combined heating and refrigeration systems. As sustainable development becomes more important, further sophistication in development and operation of such systems is desirable.

Brief description

The present invention seeks to provide an improved multi-mode refrigeration system.

According to an aspect of the present invention, there is provided a multi-mode refrigeration system as specified in claim 1.

According to another aspect of the present invention, there is provided a control unit for the multi-mode refrigeration system as specified in claim 9.

According to another aspect of the present invention, there is provided a computer-readable medium comprising computer program code for the control unit as specified in claim 10.

The invention may provide the advantage that the same multi-mode refrigeration unit may be used flexibly and optimized for different cooling functions. An optimized efficiency may be obtained as the system operates in two different operation modes taking into account cooling and heating needs.

List of drawings

Example embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawing, in which Figure 1 illustrates example embodiments of the multi-mode refrigeration system. Description of embodiments

The following embodiments are only examples. Although the specification may refer to "an" embodiment in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

As illustrated in Figure 1, a multi-mode refrigeration system 100 comprises a refrigeration unit 140 to produce cold, referenced with and a heat recovery unit 130 coupled with the refrigeration unit 140 to produce heat, referenced with '+'.

In an example embodiment, the refrigeration unit 140 operates according to the well-known vapour-compression cycle.

In an example embodiment, the heat recovery unit 130 operates according to the well-known heat pump principle. Note that the heat recovery unit 130 may comprise one or more heat reclaim accumulators 132. In such a system, the refrigeration unit 140 acts as a heat source, and the heat reclaim accumulators 132 as the heat sink.

Furthermore, the multi-mode refrigeration system 100 comprises three interfaces: a first interface 150 to exchange heat energy +- with a first external refrigeration system 170 with a first temperature requirement, a second interface 152 to exchange heat energy +- with a second external refrigeration system 180 with a second temperature requirement, and a control interface 154 to control, referenced with 'C, a third external refrigeration system 182.

The first interface 150 and the second interface 152 may be implemented with appropriate tubes and valves controllable by the control unit The control interface 154 as well as the other control interfaces C controlled by the control unit 102 may be implemented with appropriate wired/wireless communication technologies and standard/proprietary protocols such as an industrial control bus. In an example embodiment, the wireless communication is implemented with a suitable cellular communication technology such as GSM, GPRS, EGPRS, WCDMA, UMTS, 3GPP, IMT, LTE, LTE-A, etc. and/or with a suitable non-cellular communication technology such as Bluetooth, Bluetooth Low Energy, Wi-Fi, WLAN, Zigbee, etc.

In an example embodiment, the wired communication is implemented with a suitable communication technology utilizing coaxial cable, twisted pair or fibre optic such as LAN or the Ethernet. In an example embodiment, a fieldbus (such as PROFIBUS, DANBUSS, or Modbus) may be utilized for the communication. The communication traffic may also be transported (in an encrypted form, for example) in the Internet.

The multi-mode refrigeration system 100 also comprises a control unit

102 to select 110 an operation mode (for the multi-mode refrigeration system 100).

The multi-mode refrigeration system 100 operates in two different modes.

In the first mode, the control unit 102 activates 112 the first interface

150 and sets C a first evaporation temperature to the refrigeration unit 140 to optimize operation with the first external refrigeration system 170 to maintain the first temperature requirement.

In the second mode, the control unit 102 activates 114 the second interface 152 and sets C a second evaporation temperature to the refrigeration unit 140 to optimize operation with the second external refrigeration system 180 to maintain the second temperature requirement, sets a target for heat + produced with the heat recovery unit 130, controls C the heat recovery unit 130 to produce an amount of heat + meeting the target, and transmits C a control signal through the control interface 154 to the third external refrigeration system 182 to regulate its operation so that the second external refrigeration system 180 is capable of producing enough heat + reclaimed with the heat recovery unit 130 to meet the target.

With these two modes 112, 114, the multi-mode refrigeration system 100 is capable of operating with two different entities: in the first mode 112 with the first external refrigeration system 170, and in the second mode 114 in concert with the second external refrigeration system 180 and the third external refrigeration system 182 and the heat recovery unit 130. An advantage may be that an utilization rate of the multi-mode refrigeration system 100 may be increased. This may be especially beneficial if the multi-mode refrigeration system 100 operates in a more efficient manner with the second external refrigeration system 180 than the third external refrigeration system 182.

Note that the first evaporation temperature and the second evaporation temperature are selected such that each of them optimizes the operation in their mode with the refrigeration unit 140. As the first evaporation temperature and the second evaporation temperature are different, an energy- optimized solution in each operation mode 112, 114 is obtained.

In an example embodiment, the operation of the first external refrigeration system 170 is periodical, and operation of the second external refrigeration system 180 is auxiliary to a third external refrigeration system 182.

The periodical nature may refer to seasons: in colder climates, the first external refrigeration system 170 may need to be used only during the summer months, for example. The periodical nature may also refer to time of day: the first external refrigeration system 170 may need to be used only during daytime. The periodical nature may also refer to some other periodicity: the first external refrigeration system 170 needs to be used during previously determined periods or during "on-the-fly" determined periods.

In an example embodiment, the control unit 102 maintains a clock and receives an outdoor temperature, and time (and date or day of week) and outdoor temperature are used as parameters in determining a beginning and an end for the operation period of the first mode. The operation of the second external refrigeration system 180 may then occur between these periods, according to a predetermined plan or on a "as needed" basis.

The second external refrigeration system 180 may be 'auxiliary' to the third external refrigeration system 182 in the sense that the third external refrigeration system 182 is the main system, and its operation may be adjusted so that the second external refrigeration system 180 gets enough use (regarding time and required cooling power) so that the heat recovery unit 130 is able to match its required heat output.

In an example embodiment, the control unit 102 may obtain temperatures from temperature sensors placed in various places, by a tank 144, between an evaporation unit 142 and the tank 144 etc. in order to optimize the operation. The control unit 102 performs the control by adjusting a pump of the evaporation unit 142, the refrigeration unit 140 and its suction pressure, pumps interacting with the interfaces 150, 152, a pump of the heat recovery unit 130, various valves, and temperature settings.

In an example embodiment, the first external refrigeration system 170 belongs to an air conditioning system 172 of a building 190, and the second external refrigeration system 180 augments another cooling process 184 in a building 190. The air conditioning system 172 of the building 190 may be a part of HVAC (heating, ventilation and air conditioning) of the building 190.

As was explained earlier, in certain climates, the first external refrigeration system 170 needs to be operated as a part of the air conditioning system 172 only during summer months.

In an example embodiment, the other cooling process 184 implements a cold store 186 in a confined space in the building 190. The cold store 186 may be a warehouse for refrigerated or frozen goods, for example. The cold store 186 may be a part of HVAC&R (heating, ventilation, air conditioning and refrigeration) of the building 190.

Even though Figure 1 only illustrates one building, 190, the operation of the multi-mode refrigeration system 100 may be coupled with one or more buildings 190. Accordingly, in an example embodiment, the first external refrigeration system 170, the second external refrigeration system 180, the third external refrigeration system 182 and the heat recovery unit 130 direct their effect to one or more buildings 190.

In an example embodiment, the heat recovery unit 130 is configured to output + the produced heat to at least one of a heating unit 160 of a building 190, a heating unit 160 of a water supply, a defrosting unit 160 of the first external refrigeration system 170, a defrosting unit 160 of the second external refrigeration system 180, a defrosting unit 160 of the third external refrigeration system 182.

In an example embodiment, the refrigeration unit 140 comprises one or more evaporation units 142 and one or more refrigeration system tanks 144, and the first evaporation temperature or the second evaporation temperature optimizes the operation by optimizing operation of the one or more evaporation units 142 and the one or more refrigeration system tanks 144. Note that this may provide an advantage that the components, the evaporation unit 142, the tank 144 and the required liquid circuit, need not be duplicated, but the same components operate, alternatively, with the first external refrigeration system 170 or the second external refrigeration system 180.

In an example embodiment, the refrigeration unit 140 operates with liquid carbon dioxide 146 as a refrigerant.

In an example embodiment, the refrigeration unit 140 operates with supercritical carbon dioxide as the refrigerant, wherein the carbon dioxide is in a fluid state where it is held at or above its critical temperature and critical pressure.

However, the example embodiments are not restricted to these refrigerants, but other refrigerants known in the art may be applied as well.

In an example embodiment, the control unit 102 may be implemented as an industrial controller. The control unit 102 may operate in a centralized fashion, even as a single control apparatus, or, in a distributed fashion, comprising more than one interacting and communicating control apparatuses. In an example embodiment, the control unit 102 may be implemented as a stand-alone computing apparatus, such as a computer or a server.

Depending on the required processing power, the control unit 102 may be implemented with computer technology, such as a laptop, an industrial computer, or an unit with one or more microprocessors.

In an example embodiment, the control unit 102 is a general-purpose off-the-shelf computing device, as opposed to a purpose-build proprietary equipment, whereby research & development costs will be lower as only the special-purpose software (and not the hardware) needs to be designed, implemented and tested. Also, the server may be implemented as a general- purpose off-the-shelf computing device with an appropriate software.

Alternatively, or additionally, at least a part of the required processing may be performed according to a client-server architecture, a cloud computing architecture, a peer-to-peer system, or another applicable computing architecture.

In an example embodiment, the control unit 102 for the multi-mode refrigeration system 100 comprises one or more processors 104, and one or more memories 106 including computer program code 108.

The one or more memories 106 and the computer program code 108 are configured to, with the one or more processors 104, cause the control unit 102 to select 110 the operation mode and perform the above-described operations.

An example embodiment provides also a computer-readable medium 120 comprising the computer program code 108 for the control unit 102, which, when loaded into the control unit 102 and executed by the control unit 102, causes the control unit 102 to select 110 the operation mode and perform the described operations.

The term 'processor' 104 refers to a device that is capable of processing data. Depending on the processing power needed, the control unit 102 may comprise several processors 104 such as parallel processors or a multicore processor. The term 'memory' 108 refers to a device that is capable of storing data run-time (= working memory) or permanently (= non-volatile memory). The working memory and the non-volatile memory may be implemented by a random-access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), a flash memory, a solid state disk (SSD), PROM (programmable read-only memory), a suitable semiconductor, or any other means of implementing an electrical computer memory.

The processor 104 and the memory 106 may be implemented by an electronic circuitry. A non-exhaustive list of implementation techniques for the processor 104 and the memory 106 includes, but is not limited to: logic components, standard integrated circuits, application-specific integrated circuits (ASIC), system-on-a-chip (SoC), application-specific standard products (ASSP), microprocessors, microcontrollers, digital signal processors, special-purpose computer chips, field-programmable gate arrays (FPGA), and other suitable electronics structures.

The computer program code 108 may be implemented by software and/or hardware. In an example embodiment, the software may be written by a suitable programming language (a high-level programming language, such as C, C++, or Java, or a low-level programming language, such as a machine language, or an assembler, for example), and the resulting executable code 108 may be stored on the memory 106 and run by the processor 104. In an alternative example embodiment, the functionality of the hardware may be designed by a suitable hardware description language (such as Verilog or VHDL), and transformed into a gate-level netlist (describing standard cells and the electrical connections between them), and after further phases the chip implementing the processor 104 memory 106 and the code 108 may be fabricated with photo masks describing the circuitry.

In an example embodiment, the operations of the computer program code 108 may be divided into functional modules, sub-routines, methods, classes, objects, applets, macros, etc., depending on the software design methodology and the programming language used. In modern programming environments, there are software libraries, i.e. compilations of ready-made functions, which may be utilized by the computer program code 108 for performing a wide variety of standard operations. In an example embodiment, the computer program code 108 may be in source code form, object code form, executable file, or in some intermediate form.

The computer-readable medium 120 may comprise at least the following: any entity or device capable of carrying the computer program code 108 to the control unit 102, a record medium, a computer memory, a read-only memory, an electrical carrier signal, a telecommunications signal, and a software distribution medium. In some jurisdictions, depending on the legislation and the patent practice, the computer-readable medium 120 may not be the telecommunications signal. In an example embodiment, the computer-readable medium 120 may be a computer-readable storage medium. In an example embodiment, the computer-readable medium 120 may be a non-transitory computer-readable storage medium.

It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the example embodiments described above but may vary within the scope of the claims.