US20170010051A1 - Combined heating and cooling systems - Google Patents

Combined heating and cooling systems Download PDF

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Publication number
US20170010051A1
US20170010051A1 US15/205,567 US201615205567A US2017010051A1 US 20170010051 A1 US20170010051 A1 US 20170010051A1 US 201615205567 A US201615205567 A US 201615205567A US 2017010051 A1 US2017010051 A1 US 2017010051A1
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Prior art keywords
circuit
cooling
coolth
heating
heat
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US15/205,567
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Steve Connolly
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ARRIBA COOLTECH Ltd
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ARRIBA COOLTECH Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B29/00—Combined heating and refrigeration systems, e.g. operating alternately or simultaneously
    • F25B29/003—Combined heating and refrigeration systems, e.g. operating alternately or simultaneously of the compression type system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
    • F28D20/0039—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material with stratification of the heat storage material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D11/00—Central heating systems using heat accumulated in storage masses
    • F24D11/002—Central heating systems using heat accumulated in storage masses water heating system
    • F24D11/003—Central heating systems using heat accumulated in storage masses water heating system combined with solar energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D12/00—Other central heating systems
    • F24D12/02—Other central heating systems having more than one heat source
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
    • F24D3/00—Hot-water central heating systems
    • F24D3/005—Hot-water central heating systems combined with solar energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
    • F25B25/005—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 using primary and secondary systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B27/00—Machines, plants or systems, using particular sources of energy
    • F25B27/002—Machines, plants or systems, using particular sources of energy using solar energy
    • F25B27/005—Machines, plants or systems, using particular sources of energy using solar energy in compression type systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00—Heat pumps
    • F25B30/02—Heat pumps of the compression type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F25B49/022—Compressor control arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F27/00—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus
    • F28F27/02—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus for controlling the distribution of heat-exchange media between different channels
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F2221/00—Details or features not otherwise provided for
    • F24F2221/18—Details or features not otherwise provided for combined with domestic apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2339/00—Details of evaporators; Details of condensers
    • F25B2339/04—Details of condensers
    • F25B2339/047—Water-cooled condensers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/01—Heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/22—Refrigeration systems for supermarkets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/24—Storage receiver heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2507—Flow-diverting valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2111—Temperatures of a heat storage receiver
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/14—Thermal energy storage

Definitions

  • This invention relates combined heating and cooling systems, in particular using carbon-dioxide as a working fluid, and to control schemes for such systems.
  • a carbon-dioxide-based cooling and heating apparatus can be found in US2008/0245505. This describes an apparatus and method with two refrigerating cycle circuits and a sublimation heat exchanger.
  • a heat pump using carbon-dioxide as a refrigerant and natural water such as well water and the like as a heat source is described in US2007/0261432.
  • a cooling-heating device for an ice rink facility is described in CA2,748,027A. In broad terms this addresses the problem of maintaining a ratio of recovered heat to generated heat, and describes a system with multiple heat exchangers in the CO 2 refrigerant line and a valve to control the flow rate of the CO 2 refrigerant.
  • a combined heating and cooling system comprising: a working fluid circuit comprising a compressor, a gas cooler and an evaporator; a heating circuit, thermally coupled to said working fluid circuit via said gas cooler; and a cooling circuit, thermally coupled to said working fluid circuit via said evaporator; wherein said heating circuit further comprises a thermal storage tank, in particular a stratified thermal storage tank, controllably coupled to said heating circuit to controllably store heat for said heating circuit.
  • Embodiments of the above described system are adapted for control to facilitate efficient operation of the system.
  • a controllable thermal store it is easier both to operate the system in an efficient regime when simultaneously heating and cooling and also to achieve stable control of the combined heating and cooling system.
  • the thermal storage tank is configured such that the tank is stratified, in particular into one or more of layers of fluid separated by one or more thermoclines (although a mechanically stratified tank may alternatively be employed).
  • a single tank is employed with a thermocline which moves up and down within the tank according to the amount of heat stored in the tank; optionally multiple such tanks may be provided “in parallel”.
  • the stratified thermal storage tank may comprise a plurality of tank vessels or chambers coupled “in series”, for example stacked one above another or side-by side, and coupled together by one or more fluid flow conduits to allow fluid to move between them.
  • a conduit from the top (or an upper portion) of one vessel/chamber may couple to the bottom (or a lower portion) of the next vessel/chamber.
  • two (or more) conduits may couple each vessel to each adjacent vessel, optionally one conduit allowing fluid flow in one direction (for example, up) and a second conduit allowing fluid flow in a second direction (for example, down).
  • the moving thermocline may be approximated by a change in the number of vessels containing hot (warmer) as opposed to cold (cooler) fluid (for example water). Suitable devices are known to those in the art and are also available for purchase.
  • stratified thermal storage tank Use of a stratified thermal storage tank is advantageous as this separates relatively warmer and cooler portions of the heating circuit fluid. This in turn facilitates achieving a low temperature for the input to the gas cooler, this low temperature in the heating circuit facilitating efficient operation of the working fluid circuit.
  • employing stratified thermal storage not only facilitates obtaining a higher temperature for the portion of the heating circuit used for heating, it also facilities achieving a lower temperature in a different portion of the heating circuit which facilitates efficient operation of the overall system.
  • a stratified thermal storage tank allows the thermal storage tank to be used as a gauge in which the degree of stored thermal energy can be determined from a set of temperature sensors at different levels within the tank. This in turn facilitates control of the system based upon stored energy rather than on temperature per se.
  • the stored thermal energy gauge may be provided by a count of the number of vessels/chambers containing hot (warmer) as opposed to cold (cooler) fluid. It is not, however, essential to employ stratified thermal storage as in principle the advantages of such an approach may be achieved in other ways, for example by means of multiple smaller thermal storage tanks.
  • the system also includes a thermal dump system to enable heat to be dumped from said heating circuit, again to facilitate efficient overall system control, counter-intuitively dumping thermal energy facilitating an overall energy saving.
  • the heating circuit is configured, for example using valves, to direct or switch flow in the circuit between the thermal storage tank and the thermal dump, for example when the thermal store does not need to be replenished.
  • a heating side control system controls storage and dumping of heat for the heating circuit, in particular based on a level of stored energy. In embodiments this is measured by a set of temperature sensors in the stratified thermal storage tank, that is control is effectively based upon thermal energy stored in the heating circuit.
  • the heating side control system controls the compressor with the aim of maintaining the stored thermal energy at a substantially steady state, which may be defined by a target range. For example the virtual temperature gauge provided by the stratified thermal storage tank may be controlled to a target percentage/percentage range (of full capacity).
  • Preferred embodiments of the system also include a measure of stored coolth (the term of art “coolth” is explained in more detail later).
  • the stored coolth may be measured by one or more temperature sensors in the cooling circuit.
  • the heating side control system is responsive to both stored heat energy and to stored coolth, in particular to control the compressor and/or to dump heat from the heating circuit.
  • Preferred embodiments of the system also include a controllable coolth dump to allow coolth to be dumped from the cooling circuit.
  • This may comprise, for example, a controllable heat exchanger to exchange heat with an ambient, typically external environment. Such a heat exchanger may also be used for “warmth dumping”, that is for free cooling where the ambient temperature is less than a target temperature for the cooling circuit.
  • a cooling side control system is preferably included to control the coolth dump responsive to a sensed temperature of coolant within the cooling circuit, in particular to control a heat input to the evaporator provided by the coolant.
  • the coolant temperature for the cooling side control system is measured in a coolant flow path to an input to the evaporator, more particularly in the mixer header described later.
  • the cooling circuit has a coolth output (the ‘ring-main’ in the example described later), and is controllably reconfigurable between parallel and series modes of operation.
  • the controllable coolth dump In the parallel mode the controllable coolth dump is coupled in parallel with the coolth output, and in the series mode these are coupled in series.
  • a configuration may be provided in which a portion of the output of the coolth dump may be mixed with a portion of the output from the evaporator.
  • control is provided, preferably by the cooling side control system, to switch the cooling circuit between the series and parallel modes of operation dependent upon an ambient temperature (of the controllable coolth dump). More particularly the series mode may be selected when the ambient temperature is below a target temperature for the coolth output.
  • a solar thermal energy capture system may be coupled to the heating side of the circuit to facilitate use of ‘free’ solar heating when available.
  • the invention provides a method of controlling a combined heating and cooling system, in particular as described above, the method comprising: determining one or both of a stored heat in said heating circuit and a stored coolth in said cooling circuit; and controlling one or both of said compressor and said coupling of said stratified thermal storage tank to said heating circuit responsive to said determination of stored heat/coolth to maintain one or both of said stored heat and said stored coolth in a steady state, more particularly within a respective target range.
  • the stratified thermal storage tank may comprise a single tank or a set of stacked vessels (tanks/vessels may be coupled “in series” and/or “in parallel”).
  • the heating circuit is controlled to control the stored heat and/or stored coolth, for example to maintain this is a steady state, in embodiments to achieve a target or target range of stored heat and/or stored coolth. In embodiments this is achieved by controlling the compressor and preferably also by controlling dumping of heat from the heating circuit. Whilst it might be thought that it would be most efficient to store all the heat generated, counter-intuitively the overall system efficiency can at times be increased by dumping heat.
  • the invention provides a method of controlling a combined heating and cooling system, in particular as described above, the method comprising: determining a temperature of coolant circulating in said cooling circuit; and controlling dumping of coolth from said cooling circuit responsive to said coolant temperature to control a heat input to said evaporator provided by said coolant.
  • the overall system efficiency can at times be increased by dumping coolth from the cooling side of the system, so as effectively to heat the input to the evaporator (from the cooling circuit) and increase the efficiency of the working fluid circuit.
  • the coolth may be dumped by controlling the rate at which a heat exchanger operates (in embodiments, to exchange heat with an ambient, generally external environment); and/or by selecting a series or parallel mode of operation for the cooling circuit.
  • the method further comprises selecting a series mode of operation when ‘free’ cooling is available, that is when an ambient environment of the coolth dumping device is less than a target desired temperature for the coolant in the coolth output of the cooling circuit.
  • both of the above control methods are implemented in a combined heating and cooling system of the type we describe.
  • the working fluid comprises carbon-dioxide.
  • the working fluid circuit is configured to operate (by default) with a transcritical cycle.
  • the invention provides a carbon dioxide-based combined heating and cooling system, the system comprising: a working fluid circuit comprising a compressor, a gas cooler and an evaporator; a heating circuit, thermally coupled to said working fluid circuit via said gas cooler and having heat output; and a cooling circuit, thermally coupled to said working fluid circuit via said evaporator and having a coolth output; and a first control system to control said working fluid circuit responsive to one or both of heat stored in said heating circuit and coolth stored in said cooling circuit to partly satisfy heat and coolth demands from respective said heat and coolth outputs with stored heat and/or coolth.
  • the system is controlled based (partly) on stored heat and/or coolth, and preferably operates to control storage and/or dumping of heat and/or coolth.
  • the control is further facilitated by controlled dumping of either heat or coolth, for example to facilitate achieving an approximately steady state of stored heat and coolth (even with varying heat and coolth demands).
  • a steady state may involve the stored heat and coolth being approximately in the middle of their respective ranges (for example 50%+/ ⁇ 30%), but alternatively the system may be biased towards greater or lesser storage of heat and/or coolth.
  • a further control system preferably operating with a shorter cycle time, operates to control the cooling side circuit to control the temperature of the coolant flowing into the evaporator, again preferably by controlling at least dumping of coolth from the cooling side circuit.
  • the second control system may operate to control the coolant temperature up towards a target temperature. In broad terms this is advantageous because this raises the pressure of the working fluid (carbon dioxide) in the evaporator, which in turn increases the mass flow of working fluid through the evaporator and compressor, without causing a proportionate rise in the shaft power of the compressor. This helps to raise the “Coefficient of Performance” (COP) of the refrigeration cycle.
  • COP Coefficient of Performance
  • the second control system also controls the coolant temperature down towards a target to achieve a target cooling effect (from a coolth output of the cooling side circuit).
  • the second control system may also selectively couple the coolth dump (heat exchanger) either in series or in parallel with the coolth output responsive to a sensed ambient temperature. That is a parallel configuration may be selected if the ambient temperature is greater than a target temperature of the coolant.
  • the system controls the heating side of the system in response to a determined stored heat gauge and/or a determined stored coolth gauge.
  • the heating circuit includes a controllable heat dump to (indirectly) control the efficiency of operation of the working fluid circuit, in particular to facilitate dumping heat from the working fluid (carbon dioxide) circuit.
  • FIGS. 1A and 1B show a cooling circuit of an integrated heating/cooling system according to a preferred embodiment of the present invention, configured respectively into a parallel mode of operation and a series mode of operation;
  • FIG. 2 shows a heating side of the integrated heating/cooling system of FIG. 1 ;
  • FIG. 3 shows a control system for the integrated heating/cooling system of FIGS. 1 and 2 ;
  • FIG. 4 shows a pressure-enthalpy curve illustrating operation of part of the integrated heating/cooling system of FIGS. 1 and 2 ;
  • FIG. 5 shows a stratified thermal storage tank instrumented with a temperature sensors for use with the integrated heating/cooling system of FIGS. 1 and 2 ;
  • FIGS. 6A and 6B show, respectively, a compressor control procedure a thermal store/dump control procedure for the integrated heating/cooling system of FIGS. 1 and 2 ;
  • FIG. 7 shows regions of a lookup table for controlling operation of the integrated heating/cooling system of FIGS. 1 and 2 ;
  • FIGS. 8A, 8B and 8C illustrates a first example of operation of the integrated heating/cooling system of FIGS. 1 and 2 ;
  • FIGS. 9A, 9B, 9C, 9D and 9E illustrate a second example of operation of the integrated heating/cooling system of FIGS. 1 and 2 .
  • a chilled water circuit and a heated water circuit are provided, for example a chilled water ring main and a low temperature hot water (LTHW) ring main.
  • chilled water we generally refer to chilled water but the skilled person will understand that this may include an antifreeze such as glycol or salt (in which latter case the chilled water may be brine).
  • an antifreeze such as glycol or salt (in which latter case the chilled water may be brine).
  • the techniques we describe are not limited to use with any particular working fluid such as water (in the heating or cooling circuits), or even carbon dioxide.
  • ring main this merely refers to any form of circuit (which may include series and/or parallel sub-circuits).
  • cooling we describe further below what is meant by “free cooling”, but in outline some preferred embodiments of the system employ a heat exchanger, more particularly an air-blast heat exchanger in the chilled water circuit, located in the external (outside) environment.
  • a heat exchanger more particularly an air-blast heat exchanger in the chilled water circuit, located in the external (outside) environment.
  • the ambient air can be used for “free” cooling of the chilled water.
  • the heating/cooling system uses a vapour-compression refrigerating principle and is fitted with a gas cooler that is controlled to operate in a transcritical range of CO 2 pressures.
  • the integrated heating/cooling system includes a system for heat (hot water) storage, in embodiments a thermally layered storage tank. This storage facilitates control of the system, in particular facilitating the joint operation of the heating and cooling portions of the system in a manner which provides some tolerance to varying loads on either side of the system (heating and cooling), such that the operation of the system can be overall more efficient.
  • the integrated heating/cooling system additionally or alternatively includes a mechanism to effectively provide cold (chilled water) storage, for similar reasons.
  • this can be considered to be provided by the circulating chilled water in combination with a measure of a cooling requirement to be provided by the circulating chilled water.
  • the measure may comprise a temperature difference between a target cold temperature and the temperature of the circulating chilled water at a point prior to its use for cooling, that is, for delivering coolth to a process.
  • a measure of such a temperature difference may be used as a proxy for the stored coolth in the chilled water (brine) circuit.
  • a control system 300 is shown schematically; in embodiments it comprises a general purpose computer system or dedicated controller 310 including stored program code to control the operation of the system.
  • the control system 300 also includes one or more interfaces 302 for controlling the heating and cooling circuits, more particularly valves, optionally pumps, and for controlling a CO2 refrigerant compressor of the combined heating/cooling system. It preferably also includes one or more sensor interfaces 304 for sensing temperatures and/or pressures within the system, and optionally for monitoring correct operation of components of the system.
  • the control system may still further comprise a user interface 306 for interacting with, monitoring, configuring, and/or controlling the heating/cooling system; and optionally a wired or wireless network interface 308 for external communications and remote monitoring/control.
  • FIGS. 1A and 1B show a cooling (chilled brine) circuit 100 a of the system, with valves controlled to put the circuit into parallel and series modes of operation respectively.
  • parallel refers to an air blast heat exchanger and chilled ring-main configured so that fluid flows through both systems take place in parallel (ie fluid enters both systems from a common source at the same time)
  • series refers to an air blast heat exchanger and chilled ring-main configured so that fluid flows in series, firstly through the air-blast heat exchanger and then after that into a chilled water circuit.
  • FIG. 2 shows a heating (LTHW) portion of the circuit 100 b .
  • FIGS. 1 and 2 together show a complete system—evaporator 102 is common to FIGS. 1 and 2 .
  • the evaporator has a relatively lower pressure side 102 a connected to the cooling circuit, more particularly through which the chilled water (brine) circulates, and a relatively higher pressure side 102 b connected to the CO2 circuit, more particularly through which the CO2 liquid circulates.
  • the chilled ring main typically comprises one or more cooling devices such as (air) coolers 107 a - c which may be used, for example, for comfort cooling (air conditioning), for food conservation (to cool a food chiller cabinet), or the like.
  • Air-blast heat exchanger 104 is preferably located outside a building or in some other environment external to or outside the regions heated/chilled by the system 100 .
  • a typical air-blast heat exchanger used in embodiments of the invention may comprise a coiled or meandering piped liquid path in combination with one or more fans to force air over the piped liquid.
  • the external air-blast heat exchanger may be used to dump (jettison) excess coolth from the chilled water (brine) circuit in what might be termed a “sky cooling mode” of operation.
  • This mode is operable when the chilled water (brine) temperature inside the air-blast heat exchanger is more than a threshold colder, for example 2 or more degrees Celsius colder, than the ambient air.
  • a threshold colder for example 2 or more degrees Celsius colder
  • the air-blast heat exchanger may be used to dump (jettison) excess warmth from the chilled water (brine) circuit
  • the range of values of the ambient/outside temperature may overlap with the target temperature range for the chilled water circuit, perhaps ⁇ 5° C. to +15° C. (the higher end encompassing air conditioners).
  • the target temperature range for the chilled water circuit perhaps ⁇ 5° C. to +15° C. (the higher end encompassing air conditioners).
  • ambient air may provide an important part of the overall system control.
  • a chilled water circuit operating with a 12° C. flow and 7° C.
  • the chilled liquid circuit comprises two main pumps, a first pump 106 and a second pump 108 .
  • the first pump 106 may be termed a chilled circuit pump because it circulates chilled liquid through the air coolers 107 a - c of ring main 107 , either directly (parallel mode) or indirectly (series mode).
  • the second pump 108 may be termed an evaporator pump because it draws chilled liquid through the evaporator.
  • first pump 106 circulates the cooled liquid through cooling devices (air coolers) 107 a - c and the second pump 108 circulates the cooled liquid through air-blast heat exchanger 104 to chill the ambient air (dump excess coolth).
  • first pump 106 circulates chilled water (brine) sequentially through the air-blast heat exchanger 104 and next through air coolers 107 a - c ; this may be a substantially constant circulation of liquid.
  • the second pump 108 may operate intermittently or not at all to circulate liquid in the cooling circuit, in particular to mix liquid in a mixing tank, mixing header 110 .
  • Mixing header (or “discharge header”) 110 is, essentially, a junction box so that the circulating flows meet and mix prior to flowing back through evaporator 102 and/or air coolers 107 .
  • a suction header 112 is included in the path of liquid exiting the evaporator 102 , to provide a “junction box” with parallel flow outputs on this side of the evaporator (in operation the “suction header” is substantially entirely full of liquid).
  • the cooling circuit 100 a of FIG. 1 includes a number of controllable valves, which may be controlled by the control system to configure the circuit for either a series or a parallel mode of system operation.
  • the valves thus operate as mode selection valves; in embodiments the valves are controlled electrically by control system 200 to select fluid flow paths through the valves.
  • the lower pressure side 102 a of evaporator 102 has an output fluid flow path or conduit 130 coupled to (suction) header 112 , which in turn has first and second output conduits 132 , 134 .
  • Conduit is used broadly to mean any fluid flow path).
  • Conduit 132 provides a first input to a first controllable (mode selection) valve 114 , which has a second input from conduit 150 and an output conduit 136 .
  • Valve 114 is controllable to direct either the first or second input to output 136 .
  • the second output conduit 134 of evaporator 102 is coupled to an input (suction side) of evaporator pump 108 .
  • the output conduit 136 provides a first input to an optional (but preferable) mixing valve 116 , which has a second input conduit 138 , and an output conduit 140 .
  • Conduit 140 provides an input to chiller circuit pump 106 .
  • the second input 138 to mixing valve 116 is from liquid which has passed through the chilled circuit 107 , and which has thus been warmed by this passage, thus helping to warm the input to the chilled “ring main” in a condition in which there is excess coolth in the suction header.
  • Valve 116 is preferably controllable to selectively mix input 138 with the flow between input 136 and output 140 . We describe control of valve 116 later, but in embodiments if the chilled water (brine) temperature inside the suction header is greater than a threshold difference lower than a desired target temperature some of the output of the ring main may be mixed in.
  • An output conduit 142 of chiller circuit pump 106 provides an input to a second controllable (mode selection) valve 120 , which has a first output conduit 144 to air-blast heat exchanger 104 and a second output conduit 146 to chilled “ring main” 107 .
  • Valve 120 is controllable to direct the input 142 to either the first or second output 144 , 146 .
  • the output conduit 146 of valve 120 is coupled to ring main 107 , to provide a chilled water input to the air coolers 107 a - c of ring main 107 .
  • An output conduit 148 from ring main 107 provides a first input to (mixing) header 110 .
  • Pump 108 has an output conduit 152 which provides an input to a third controllable (mode selection) valve 118 .
  • Valve 118 has a first output conduit 154 joining conduit 144 , to provide an input to (external) air-blast heat exchanger 104 , and a second output conduit 156 which provides a second input to (mixing) header 110 .
  • Valve 118 is controllable to direct the input 152 to either the first or second output 154 , 156 .
  • An output conduit 158 from air-blast heat exchanger 104 provides an input to a fourth controllable (mode selection) valve 122 , which has a first output conduit 160 , and a second output conduit 162 which provides a third input to (mixing) header 110 .
  • the first output conduit 160 is coupled to conduit 146 , so that circulating liquid from air blast heat exchanger 104 can provide an input to ring main 107 .
  • Valve 122 is controllable to direct the input 158 to either the first or second output 160 , 162 (in series and parallel mode respectively).
  • the (mixing) header 110 has a first output conduit 150 , which provides an input to valve 114 to enable circulation of liquid through the external air blast heat exchanger 104 and ring main 107 in series mode.
  • the (mixing) header 110 has a second output conduit 164 which provides an input to the higher temperature side 102 a of evaporator 102 and, in embodiments, provides a continuous path through evaporator 102 to output conduit 130 .
  • evaporator 102 acts as a heat exchanger and the path 164 , 130 through evaporator 102 provides one part of the flow through this heat exchanger.
  • the fluid conduit may be defined in many ways, for example by tubes, plates, baffles and the like.
  • valves and conduits may be varied whilst still providing a cooling circuit which can be switched between parallel and series modes of operation.
  • liquid circulates sequentially through the external air-blast heat exchanger and chilled “ring main” (optionally but preferably water is also circulated through evaporator in a second circuit).
  • ring main optionally mixing the output from the ring main with the input to the ring main, so that the ring-main feed-in temperature is not excessively cold.
  • temperatures of the circulating liquid depend upon the application. Nonetheless it is helpful for understanding embodiments of the invention to provide illustrative example temperatures.
  • the input 146 to these may be at around ⁇ 5° C. whilst the output 148 from these may be at around ⁇ 1° C. (for an air conditioning circuit the input temperature may be higher, for example around +10° C.).
  • an air cooler has air at, say, +1° C. blown over a conduit, radiator or the like carrying the chilled liquid (brine), so that the air is cooled to, say, around ⁇ 2° C. whilst the brine is heated from, say, ⁇ 5° C. to ⁇ 1° C.
  • the output 130 from the evaporator 102 may have become significantly colder than the targeted chilled ring-main feed-in temperature (it may have reached ⁇ 8° C. for example, at the same time brine being fed into the air-blast heat exchanger 104 would also be at ⁇ 8° C.).
  • Parallel mode is selected when the external air temperature is high enough to allow dumping of coolth, for example ⁇ 8° C. coolth can easily be dumped into ambient air of +9° C., and thus the output 158 from the air-blast heat exchanger could be substantially warmer than the water exiting air coolers 107 a - c .
  • the mixing header may receive one flow at around ⁇ 1° C. and another flow at around +5° C. (assuming 9° C. ambient).
  • the outlet 148 from coolers 107 a - c on the chilled water (brine) ring-main may again be at around ⁇ 1° C.
  • the ambient temperature is sufficiently low in this mode of operation for the air-blast heat exchanger 104 to be able to at least partially cool the output from the chilled ring-main 107 .
  • the cooling for the chilled ring-main can at times be provided solely by the air-blast heat exchanger 104 .
  • FIG. 2 this shows a heating (LTHW) portion of the circuit 100 b , in which evaporator 102 is common to the circuits shown in FIGS. 1A, 1B and 2 .
  • the heating circuit side of system 100 includes a vapour (gas) compression refrigeration system.
  • the evaporator 102 of FIG. 2 is the same evaporator 102 as illustrated in FIGS. 1A and 1B .
  • conduit 202 carries high pressure dense gas, in particular carbon dioxide, towards an expansion valve 204 , which allows the pressure to reduce, with a concomitant reduction in CO2 temperature.
  • expansion valve 204 may be an automatically adjustable small bore needle valve. Expansion valve 204 converts the gas, which at this point is a dense mist, into a cold, mostly liquid state in conduit 206 leading away from expansion valve 204 .
  • the temperature of the liquid in conduit 202 may be around 30° C. whilst the temperature of the fluid in conduit 206 may be around ⁇ 10° C. For efficient operation it is preferred that there is some turbulence in the flow within conduit 206 .
  • vapour carbon dioxide
  • Conduit 206 provides a continuous path through evaporator 102 to output conduit 208 .
  • the carbon dioxide is boiled, for example at 10° C. to the point where 5K or more of superheat is generated by the counter-flowing liquid (brine/glycol) in the conduit 164 to 130 .
  • the brine is reduced in temperature eg. from ⁇ 1° C. at inlet to 102 to say ⁇ 5° C. at the outlet from evaporator 102 .
  • conduit 208 is preferably provided with a droplet separator 210 to remove residual liquid droplets from the flow prior to compression.
  • an output 212 of (optional) droplet separator 210 is provided to a compressor 214 , and this in turn has an output 216 to an optional oil separator 218 (to remove residual compressor oil), and thence to conduit 220 .
  • Compressor 214 raises the pressure of the carbon dioxide, and also the temperature of the carbon dioxide, for example to around 85° C.
  • Conduit 220 provides an input to a heat exchanger 222 , which may be referred to as a “gas cooler”: During its passage through this element the temperature of the carbon dioxide is reduced prior to its passage through expansion valve 204 , using the preceding figures to around 30° C. (the temperature in conduit 202 ).
  • a mechanical filter 226 is preferably provided between an output conduit 224 of heat exchanger 222 and expansion (needle) valve 204 .
  • Heat exchanger 222 is coupled to a water heating circuit.
  • this circuit For convenience we will sometimes refer to this circuit as an LTHW (low temperature hot water) circuit, but the skilled person will appreciate that other types of heating circuit may also be implemented.
  • heat exchanger 222 has an input conduit 228 and an output conduit 230 , together forming part of the LTHW (heating) circuit.
  • input conduit may carry water at around 28° C., which cools the counter-flowing carbon dioxide gas flowing through conduits 220 , 224 , in turn heating the water so that output conduit 230 may, for example, be at around 55° C.
  • the skilled person will appreciate that the degree of heating depends both on the temperature of the counter-flowing gas and also on the mass flows of the gas and water.
  • the output conduit 230 from heat exchanger 222 provides a source of hot water for thermal storage device 232 , in preferred embodiments a layered (stratified or thermocline) thermal storage device.
  • Conduit 230 provides an input to an upper, high temperature region of the tank where the water temperature may be, for example, around 55° C.
  • Stratification within tank 232 maintains a temperature differential between upper and lower regions of the tank and thus a lower region of the tank may at the same time be at a much lower temperature, for example around 30° C., without substantial mixing between the stratified layers.
  • An output conduit 234 from a lower region of tank 232 provides a lower temperature outlet and a lower temperature return to conduit 228 , an input to heat exchanger/gas cooler 222 . In embodiments this return is via a liquid pump 236 (although it will be appreciated that the pump may be located elsewhere); this pump may be termed a gas cooler pump.
  • the LTHW circuit also includes a heat exchanger 240 which is usable to dump excess heat, and which may therefore be termed a hot side dump exchanger.
  • This heat exchanger may be a liquid-to-liquid heat exchanger or a liquid-to-gas heat exchanger; in the latter case it may be situated in any convenient location to dump heat, for example external to a heated environment/building.
  • An input to heat exchanger 240 is provided by a conduit 248 , a branch of conduit 230 .
  • a return conduit 242 from thermal-dump heat exchanger 240 is coupled a first input of a (dump) changeover valve 244 .
  • Valve 244 has a second input from conduit 234 , and an output conduit 246 which provides an input to pump 236 .
  • valve 244 is controllable to either permit or inhibit a heated water flow through thermal-dump heat exchanger 240 .
  • Valve 244 is likewise controllable to either permit or inhibit a heated water flow into (through) the thermal store 232 , and thus effectively to switch flow between the thermal store and thermal dump.
  • One or more additional shut-off valves may be operated in coordination with valve 244 so that gas passing through 222 is cooled either via the thermal store 232 or via the hot-side dump exchanger 240 .
  • a solar water heater 260 may also be coupled to thermal store 232 , as shown in simplified form, to enable solar thermal heating input to the system.
  • the solar thermal panel(s) would serve (instead of the gas cooler) as a means of generating heat into the thermal store.
  • a heating circuit 250 in embodiments an LTHW “ring main”, is coupled to thermal storage tank 232 . More particularly in embodiments a first conduit 252 from an upper, heated region of tank 232 provides an input to heating circuit, which has a second, output conduit 254 providing an input to a lower, cooler region of the tank.
  • a pump 256 pumps water through heating circuit 250 , which includes one or more heating devices 256 a - c , for example radiators.
  • vapour gas compression refrigeration circuit
  • this operates in a transcritical mode, that is as it circulates through the refrigeration circuit the carbon dioxide defines a transcritical cycle (enclosing the critical point) on a pressure (p) enthalpy (H) graph for the carbon dioxide.
  • p pressure
  • H enthalpy
  • FIG. 4 shows such a pressure-enthalpy curve with labelled points A to D corresponding to labelled locations A to D in FIG. 2 .
  • the critical point is labelled X and lies at the top of the dome defined by the saturated liquid line (to the left) and saturated vapour line (to the right). It can be seen that the closed curve defining the carbon dioxide cycle extends above the critical point encompassing part of the supercritical region.
  • Point D labels the output from expansion valve 204 , the input to evaporator 102 .
  • the (mostly liquid) carbon dioxide passes through the evaporator at substantially constant pressure it is boiled at ⁇ 10° C. (at the saturated vapour line), and then heated-up further, to ⁇ 5° C. (in the superheated region), to arrive at point A where it has 5° C. of superheat.
  • the skilled person will appreciate that the extent of the superheating at point A is variable.
  • the vapour is then compressed by compressor 214 , moving from point A to point B at the output of the compressor and heating the gas to, for example, 85° C. At point B the gas is beyond the critical point X, in a supercritical region.
  • the vapour is cooled at approximately constant pressure, for example to 30° C., to arrive at point C, the input to the expansion valve 204 .
  • Expansion valve 204 reduces the pressure, down to point D, reducing the temperature, for example to around ⁇ 10° C., liquefying the vapour. It should be noted that whilst transcritical operation is the default mode (when the gas cooling pump connects via the thermal storage tank) it may be the case that the CO2 refrigerating cycle operates entirely below the critical point when the hot-side dump exchanger is engaged.
  • thermal storage on the heating and cooling sides of the system. This may be inherent, provided by the heated/cooled liquid circulating within the respective circuits and/or additional thermal storage may be provided, for example using a layered thermal storage tank as previously described. Thus we refer below to stored heat and stored coolth. Efficiency may still further be increased by taking advantage of effectively free cooling which may be provided by a cold external ambient environment (by comparison with a target temperature) at certain times of year.
  • control system should aim to address.
  • suitable control schemes two control schemes operate, one for the CO2 refrigerating system and one for the air-blast heat exchanger 104 . Although these systems are essentially distinct it is the case that changes made by one control system may lead to changes needing to be made by the other control system.
  • the stratified thermal storage tank 232 is instrumented with a set of temperature sensors at different levels within the tank, so that the stored energy in the tank can be determined.
  • the stored energy level (SEL) may then be defined as 25%, 50%, 75% or 100% according to whether T1; T1 and T2; T1, T2 and T3; or T1, T2, T3 and T4 are at greater than a threshold temperature (preferably the same but potentially different for each of T1 to T4).
  • a 0% level may be defined if T1 is not greater than the threshold.
  • An example table for determining the stored (heat) energy level is shown below (Table 1). Conceptually this provides a stored heat or energy level “fuel gauge” for the system, as shown in the inset to FIG. 5 . It will be appreciated that this approach may be adapted for other numbers of temperature sensors.
  • control system 300 measures temperatures T1 to T4 at intervals, for example every five minutes, and determines the stored (heat) energy level, for example in terms of a percentage, as above.
  • the cooling (chilled brine) circuit 100 a is instrumented with at least one temperature sensor to measure a temperature of liquid circulating within the circuit, in embodiments a temperature, T SH , of the input to chilled ring main 107 ( FIGS. 1A and 1B ), measured by a sensor located in the suction header 112 .
  • T target a target temperature
  • T SH the chilled brine ring-main could in this circumstance run for some time without further cooling of the brine because of the coolth stored in it
  • T SH is at a temperature of, say, ⁇ 4° C.
  • the chilled brine ring-main could not operate for long (if at all) without additional coolth being provided by the evaporator 102 .
  • the target temperature is approximately the same as the measured T SH but in principle other temperatures may be used, for example a target temperature of fresh foods being chilled by an air cooler
  • control system 300 measures T SH at intervals, for example at around the same time as T1-14, say every five minutes, and determines the stored coolth level, for example in terms of a percentage, as above. This gives information about the level of cooling that is (or is not) being delivered whilst heat is also being (or is not being) delivered by the compressor to the thermal storage tank.
  • system data from the stored energy level (SEL) and stored coolth gauge (SCG) are processed jointly to control the compressor 214 , gas cooling pump 236 , and changeover valve 244 (to control heat dumping).
  • control system operates with the aim of keeping both the stored heat and stored coolth (“gauges”) at around 50% full. In this way there is heating potential available in the heating circuit and cooling potential available in the cooling circuit. This approach also tends to optimise (power) efficiency. Alternatively, however, the system may be run with a bias towards either the heating or the cooling circuit.
  • embodiments of the system may operate with a control cycle which operates at intervals of, say, 300 seconds, to monitor the SEL and SCG and in response control the heating circuit side of system, more particularly the compressor, gas cooling pump and dump changeover valve.
  • the control cycle is adaptive, and may change depending upon the SEL and/or SCG.
  • Preferred embodiments of the control system define a set of (discrete) compressor speeds and then control the compressor by incrementing or decrementing the compressor speed between one level to another (although a similar concept may also be applied to a continuously variable compressor speed).
  • increasing the speed is referred to as “loading” the compressor and decreasing the speed as “unloading” the compressor; “stay” denotes leaving the compressor speed unchanged.
  • control system employs a lookup table to determine whether to load, stay or unload the compressor, as shown in the table below (Table 3).
  • Table 3 also defines whether the dump changeover valve 244 is controlled so that pump 236 pumps to the layered thermal store 232 (“thermal store”) or to the hot-side dump heat exchanger 240 (“hot dump”).
  • Table 3 may also be implemented by the procedures shown in FIGS. 6A and 6B (although use of a lookup table is potentially more flexible).
  • FIG. 6A which shows a compressor control procedure
  • the system reads the SEL and SCG gauges and, at S 606 , determines whether either is at 25%. If so the compressor is loaded (sped up), S 608 , and the procedure loops; otherwise if both are at 50% the compressor speed is unchanged (S 612 ).
  • the compressor is unloaded (the compressor speed is decreased).
  • FIG. 6B shows a control procedure for the thermal store/dump:
  • the procedure reads the SEL gauge and if this is less than or equal to 50% (S 626 ), heat is stored (S 628 ), and if the gauge is at 100% (S 630 ) heat is dumped (S 632 ). Otherwise SEL is at 75% and the procedure stores heat if the compressor is being unloaded by the compressor control procedure and dumps heat if the compressor is being loaded by the compressor control procedure.
  • control logic/procedures may optionally be state-dependent, that is the control applied may depend upon a previously applied control output.
  • the compressor was unloaded (decreased) in a previous control cycle, and a subsequent unload (decrease) is indicated then it may be unloaded (decreased) faster.
  • a similar approach may be applied when loading (increasing) the compressor.
  • the cycle period may be shortened in such situations.
  • embodiments of the combined procedures aim to keep one or both the SEL and SCG gauges at a steady state. This may, for example, be at around 50% or some other value—for example if providing a constant summer air conditioning load, say during times of low demand for low temperature hot water, then the SEL might read say 75% all day long whilst the SCG oscillates between say 25% and 50%.
  • compressor control may be based upon just one of these by simply assigning a false value to the gauge that is not needed.
  • the SEL parameter could be assigned a value of 100% to inhibit the compressor from altering its speed for any reason other than for the maintenance of temperatures in the suction header (chilled brine circuit).
  • the air-blast heat exchanger control operates to facilitate a mixing header temperature that is consistent with energy efficient operation. It also preferably (but not essentially) switches the brine circuitry between series and parallel modes of operation, in such a way that the mixing header ( 110 ) temperature can be raised (parallel) or lowered (series)
  • the air-blast heat exchanger control measures a temperature of the circulating coolant (for example water/brine/glycol) in the mixing header ( 110 ), and an ambient (air) temperature at entry into air-blast heat exchanger 104 , T MH and T amb respectively.
  • the circulating coolant temperature is preferably measured at a location in the return path to the evaporator 102 , conveniently at the mixing header 110 .
  • the air-blast heat exchanger control system operates to control a rate of exchange of heat with the ambient air by controlling the air-blast heat exchanger fan speeds, series-parallel switchover valves, and on/off operation of pumps 106 , 108 .
  • the control system employs a lookup table to define a control strategy for controlling these elements.
  • Table 4 shows an example lookup table, where T_glycol refers to T MH (noting that the coolant need not be glycol). As described further below, Table 4 encodes information for mode, pump and air-blast heat exchanger control but in practice multiple separate tables may be employed. Table 4 is also referred to later as the Glycol Ambient Matrix (GAM).
  • GAM Glycol Ambient Matrix
  • Table 4a shows regions A, C and E of FIG. 7 ;
  • Table 4b which should be considered as lying horizontally to the right of Table 4a, shows regions B and D of FIG. 7 .
  • FIG. 7 shows a version of the table in which regions A, B and C are regions in which the system operates in a parallel mode ( FIG. 1A ) and in which region D denotes a region of series operation ( FIG. 1B ).
  • Region E denotes a region in which the system may be configured for either series or parallel operation—for example this region may be selected to be one or the other mode (by default, series), or hysteresis may be applied so that the region denotes parallel operation if approached from a parallel region (typically region C) or series operation if approached from series region D.
  • the numbers in Table 4 denote a percentage rate of fan speed of the air-blast heat exchanger fans.
  • the quantum of heat exchange in air-blast heat exchanger 104 is a function of fan speed and temperature difference (between the ambient air and the brine flowing through the air-blast heat exchanger).
  • the evaporator pump 108 is preferably ON in all operational regions except for region B (orange “0”s in Table 4), where evaporator pump 108 is preferably OFF.
  • Table 4 above is an example table for a target coolant temperature, T MH , of ⁇ 1° C. (suitable for merchandising refrigerators).
  • the target coolant temperature is preferably, but not essentially, measured in the mixing header.
  • different target temperatures will employ different lookup tables.
  • T MH may be around +14° C.
  • T MH may be higher, for example around +20° C.
  • air-blast heat exchanger 104 is controlled so as to reduce the value of T MH until it is equal to (or close to) its target temperature. Air-blast heat exchanger 104 is able to work in this way so long as the ambient air being passed across the air blast heat exchanger is colder (by a margin, for example of 2 or more degrees Celcius) than the targeted T MH .
  • the heat exchange capacity of air-blast heat exchanger 104 is proportional to the temperature difference between the brine inside the heat exchanger and the temperature and mass flow of the air flowing across the outside of the heat exchanger.
  • air-blast heat exchanger 104 is controlled so as to increase the value of T MH until it is equal to (or close to) its target temperature. If the ambient air is colder than the targeted T MH then the air-blast heat exchanger fans are operated only to the point where they can no longer increase actual T MH (regions A and C of FIG. 7 ). For example, if the actual T MH is ⁇ 8° C. and if the air ambient air temperature is ⁇ 3° C. then it might be possible to warm the brine inside the mixing header to a temperature of say ⁇ 6° C. (allowing for a temperature difference between the ambient air and the brine inside the mixing header). There would be no benefit to be gained by attempting to warm the brine any further and so fans would at this point be switched off even if the actual T MH was colder than the target T MH .
  • control loops there are two control loops; one that operates according to a set of temperature measurements taken in the thermal storage tank and in the suction header ( 112 ) and which affects the behaviour of the compressor and the heat storage/dumping system and another that acts according to prevailing temperatures in the mixing header ( 110 ) and which influences the behaviour of the fans fitted to air-blast heat exchanger 104 , pumps 106 and 108 and a set of mode selection valves for parallel and series configuration
  • These control loops interact indirectly in that the temperature inside the mixing header (which may be influenced by the control of the air blast heat exchanger) and the temperature inside the suction header (which may be influenced by the CO2 compressor) will affect one another.
  • the mixing header is being cooled by the air-blast heat exchanger whilst the suction header is simultaneously being cooled due to the compressor.
  • the air-blast heat exchanger inhibits the build-up of excessively warm water at the exit of the cooling ring-main 107 whilst the compressor system inhibits the build-up of excessively warm water at the entry into cooling ring-main 107 .
  • Achieving balanced operation in which the two control loops reinforce (rather than work against) one another is facilitated by setting appropriate time intervals for the operation of the two control loops.
  • the air-blast heat exchanger (“GAM control”) may operate every 90 seconds, whilst the compressor (SEL/SCG control) loop may operate once every 300 seconds.
  • the air-blast heat exchanger control operates 5 or more times more frequently than the SEL/SCG control; preferably the intervals at which each control scheme operates are adjustable.
  • Balanced operation is further facilitated by assigning appropriate target temperatures to T MH and T SH .
  • a practical method of controlling the thermal output of the coolth emitters is to maintain a stable brine temperature at exit from the emitters whilst at the same time allowing the brine temperature at inlet to the emitters to float.
  • the brine exit temperature (T MH ) from a chilled brine ring-main could be held at say 14° C. whilst the brine inlet temperature (T SH ) might in practice be allowed to fluctuate between 9° C. and 12° C.
  • T MH the brine exit temperature
  • T SH the brine inlet temperature
  • the air blast heat exchanger 104 would by targeting a brine exit temperature of 14° C. effectively be delivering a brine temperature at entry to the coolth emitters of 9° C. to 12° C. Allowing for dead band effects on temperature set points it can be seen that in this example a SCG set point of say 10° C. may well result in the SCG reading a stored coolth value of 50%, which in the absence of a low SEL reading for stored warmth would not necessarily require for the compressor to be put into operation. In other words a free-cooling service via the air blast heat exchanger 104 acting alone would be sufficient to keep the air conditioning system operating within its required operating range.
  • the compressor was later compelled by a low SEL reading to operate (at the same time as which the air blast heat exchanger 104 was operating) then in practice the air blast heat exchanger would need to reduce its cooling output and its fans would be therefore slowed down. Indeed if the compressor was operated at high enough speed for long enough then the air blast heat exchanger 104 fans would be switched off and parallel configuration might be engaged, eventually leading to the fans being switched back on so that the air blast heat exchanger could dump excess coolth emanating from the evaporator as a result of the compressor being in operation.
  • a LTHW system and a chilled brine system may be driven from a common heatpump-chiller that automatically switches its emphasis between LTHW production (in which case the heatpump-chiller focuses on providing load to the thermal storage tank) and heat dumping (in which case heat is deliberately dumped in order to generate extra cooling effect in the brine circuit).
  • FIGS. 8A-8B which corresponds to FIG. 1B , this example illustrates the effect of using an air blast heat exchanger 104 for cooling during colder weather.
  • FIG. 8C corresponds to a version of FIG. 7 and illustrates the main features of a lookup table for control of the (fan of) cooler 104 .
  • FIG. 8A corresponds to point a 1 in FIG. 8C and FIG. 8B to point a 2 .
  • the target coolant temperature (in the mixing header) is, in this example, 21° C., a temperature suitable, for example, for an industrial process.
  • the ambient temperature is significantly lower than this and if the temperature of the mixing header becomes excessive this can quickly be brought under control by the control of the cooler fan(s), even if the compressor is not providing much cooling effect.
  • the scan rate of the GAM control procedure may be 90 seconds as compared to 600 seconds for the heating side (SCG+SEL) control.
  • the GAM control “fine tunes” the step changes implemented by the heating side control.
  • FIGS. 9A-9D which corresponds to FIG. 1A , this example illustrates operation of the system with the cooling side in a parallel mode of operation.
  • FIG. 9E illustrates the main features of a lookup table for control of the (fan of) cooler 104 .
  • the recirculation port 138 of mixing valve 116 is closed; in FIG. 9B it is partially open; in FIG. 9C it is wide open; and in FIG. 9D it is partially open once again.
  • the SEL and SCG “gauges” are also illustrated as insets.
  • the target coolant temperature (in the mixing header) is, in this example, 15° C., and the target suction header temperature is 10.0° C.
  • the air blast heat exchanger fan(s) and valves are operated in such a way as to influence the temperature of the mixer header 110 .
  • the SCG uses the temperature of the suction header 112 as a means of determining how much or how little coolth is available to the pumps which draw from the suction header.
  • T AMB 23° C.
  • T MIX 22° C.
  • Cooler fan(s) NIL.
  • the cooling side circuit is set in parallel mode.
  • the set point for T SUC-HDR 10° C.;
  • T SUC-HDR (ACTUAL) 14.5° C.
  • T SUC-HDR (ACT-TGT)>1 therefore the stored Coolth Gauge (SCH) reads 25% t 6 mins (b 2 )— FIG. 9B
  • the Stored Energy Level (SEL) in the thermal store reads 25%.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Combustion & Propulsion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Sustainable Energy (AREA)
  • Air Conditioning Control Device (AREA)
US15/205,567 2015-07-08 2016-07-08 Combined heating and cooling systems Abandoned US20170010051A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20210239668A1 (en) * 2020-01-31 2021-08-05 Weiss Umwelttechnik Gmbh Test chamber and a method for its control
WO2023149879A1 (fr) * 2022-02-03 2023-08-10 Vilter Manufacturing Llc Système et procédé de chauffage ou de refroidissement utilisant une pompe à chaleur

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2635647B2 (es) * 2017-04-17 2018-04-24 Ecoforest Geotermia, S.L. Sistema y método de aprovechamiento de excedentes de energía eléctrica procedentes de una instalación con generación eléctrica renovable
WO2019176143A1 (fr) * 2018-03-14 2019-09-19 株式会社島津製作所 Appareil de séparation de fluide supercritique
CN110360767A (zh) * 2019-06-05 2019-10-22 天津城建大学 一种带有补燃装置的柔性燃气机驱动型压缩式热泵系统

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4143642A (en) * 1976-09-24 1979-03-13 Vapor Corporation High temperature thermal storage system utilizing solar energy units
GB2067275A (en) * 1979-11-22 1981-07-22 Trendpam Eng Ltd Combined refrigeration and heating system
US20070199337A1 (en) * 2006-02-27 2007-08-30 Sanyo Electric Co., Ltd. Refrigeration cycle device
KR100869971B1 (ko) * 2008-02-12 2008-11-21 브이에스에너지 주식회사 히트펌프를 이용한 냉동, 냉장 및 온수축열시스템
US20110083462A1 (en) * 2008-04-24 2011-04-14 Vkr Holding A/S Device for obtaining heat
US7954336B2 (en) * 2006-07-26 2011-06-07 Jacobi Robert W Thermal storage unit for air conditioning applications

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100473823B1 (ko) * 2002-08-06 2005-03-08 삼성전자주식회사 냉수 및 온수 제조 장치를 구비한 공기 조화기
JP3876911B2 (ja) * 2005-06-29 2007-02-07 ダイキン工業株式会社 給湯装置
JP4338690B2 (ja) * 2005-09-14 2009-10-07 三洋電機株式会社 冷却装置
JP2007085685A (ja) * 2005-09-26 2007-04-05 Sanyo Electric Co Ltd ソーラー発電を用いたｃｏ２サイクル駆動装置

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4143642A (en) * 1976-09-24 1979-03-13 Vapor Corporation High temperature thermal storage system utilizing solar energy units
GB2067275A (en) * 1979-11-22 1981-07-22 Trendpam Eng Ltd Combined refrigeration and heating system
US20070199337A1 (en) * 2006-02-27 2007-08-30 Sanyo Electric Co., Ltd. Refrigeration cycle device
US7954336B2 (en) * 2006-07-26 2011-06-07 Jacobi Robert W Thermal storage unit for air conditioning applications
KR100869971B1 (ko) * 2008-02-12 2008-11-21 브이에스에너지 주식회사 히트펌프를 이용한 냉동, 냉장 및 온수축열시스템
US20110083462A1 (en) * 2008-04-24 2011-04-14 Vkr Holding A/S Device for obtaining heat

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20210239668A1 (en) * 2020-01-31 2021-08-05 Weiss Umwelttechnik Gmbh Test chamber and a method for its control
US11561211B2 (en) * 2020-01-31 2023-01-24 Weiss Technik Gmbh Test chamber and a method for its control
WO2023149879A1 (fr) * 2022-02-03 2023-08-10 Vilter Manufacturing Llc Système et procédé de chauffage ou de refroidissement utilisant une pompe à chaleur

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WO2017006126A1 (fr) 2017-01-12
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GB2540167A (en) 2017-01-11
GB201511907D0 (en) 2015-08-19

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