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EP-4367377-B1 - HEAT PUMP SYSTEM AND A METHOD OF OPERATING A HEAT PUMP SYSTEM

EP4367377B1EP 4367377 B1EP4367377 B1EP 4367377B1EP-4367377-B1

Inventors

  • WHITTAKER, KENNETH
  • WATT, Keith Graham
  • GRAESSNER, MATTHIAS

Dates

Publication Date
20260506
Application Date
20220708

Claims (16)

  1. An electrically connectable heat pump system comprising a regenerative thermal machine (1, 1*, 1**, 1***) in fluid communication with one or more heat reservoirs (21, 31), wherein the regenerative thermal machine (1, 1*, 1**, 1***) comprises working fluid compression and expansion spaces (11, 12); wherein the regenerative thermal machine (1, 1*, 1**, 1***) further comprises a phase change means (160) operable to change the phase relationship between the said working fluid compression and expansion spaces (11, 12) of the regenerative thermal machine (1, 1*, 1**, 1***), wherein the heat pump system further comprises an electrical machine (130) that is electrically connectable to an electricity distribution grid (2); characterised in that the phase change means (160) is configured to change the operation of the regenerative thermal machine (1, 1*, 1**, 1***) from a heat pump mode in which a drive mechanism (124) comprising an input/output drive end (125) of the regenerative thermal machine (1, 1*, 1**, 1***) is driven by the electrical machine (130), and an engine mode in which the input/output drive end (125) of the regenerative thermal machine (1, 1*, 1**, 1***) drives the electrical machine (130) to generate electricity, and vice versa ; wherein a direction of rotation of the input/output drive end (125) of the drive mechanism (124) is maintained as the regenerative thermal machine (1, 1*, 1**, 1***) changes mode from heat pump to heat engine and vice versa ; wherein the phase change means (160) is operable to change the operation seamlessly between heat pump mode and engine mode, without reversing the direction of rotation of the input/output drive end (125) of the regenerative thermal machine (1, 1*, 1**, 1***); and wherein the electrical machine (130) is configured to interchangeably operate as a motor in which it receives electrical motive power from the electricity grid (2) in order to drive the regenerative thermal machine (1, 1*, 1**, 1***) in the heat pump mode, and operate as a regenerative thermal machine (1, 1*, 1**, 1***) driven generator to produce and feed electrical power into said electricity grid (2).
  2. A heat pump system as claimed in claim 1, wherein the electrical machine (130) is a synchronous motor (130) and is permanently connected to the electricity grid (2).
  3. A heat pump system as claimed in claim 1, wherein the electrical machine (130) is an asynchronous motor (133) and is connected to the electricity grid (2) via a variable frequency drive device (132).
  4. A heat pump system as claimed in any preceding claim, wherein the drive mechanism (124) is adapted to vary the volume of the said compression and expansion spaces (11, 12) with respect to one another.
  5. A heat pump system as claimed in any preceding claim, wherein the phase change means (160) comprises any one or more of:- a stepper motor, a brake mechanism, an electrically actuated mechanism, a mechanically actuated mechanism, a hydraulically actuated mechanism and a pneumatically actuated mechanism.
  6. A heat pump system as claimed in claim 5, wherein the phase change means (160) is a phase change gearbox which mechanically couples one portion of the drive mechanism (124) to another portion of the drive mechanism (124), wherein the phase change transmission is adapted to change the relative angle between the two portions of the drive mechanism (124) and thereby the phase relationship between the compression and expansion spaces (11, 12), wherein the phase change means (160) comprises two drive mechanisms, one drive mechanism being provided for each of the compression and expansion spaces (11, 12), and a respective electrical machine (130) coupled to each separate drive mechanism for driving a change of volume for each of the compression and the expansion spaces (11, 12), wherein each respective electrical machine (130) is operable to control the phase angle between each said separate drive mechanism..
  7. A heat pump system as claimed in any preceding claim, further comprising a releasable coupling (140) wherein the input/drive end (125) is mechanically connectable to the electrical machine (130) via said releasable coupling (140), wherein said releasable coupling (140) comprises a clutch (140), wherein the heat pump system further comprises one or more inertial masses (150), wherein the one or more inertial masses (150) is/are at least one flywheel device (150), wherein the inertial mass (150) is located intermediate the regenerative thermal machine (1, 1*, 1**, 1***) and the electrical machine (130).
  8. A heat pump system as claimed in any preceding claim, wherein the heat pump system comprises a first heat exchanger (20) and a second heat exchanger (30), wherein one heat exchanger (20) is a hot side heat exchanger (Hx) (20) in use and one heat exchanger (30) is a cold side heat exchanger (Cx) (30) in use and wherein the respective heat exchangers (20, 30) are in fluid communication with a respective compression and expansion space (11, 12) of the regenerative thermal machine (1, 1*, 1**, 1***), wherein at least one heat reservoir (21) is in fluid communication with the hot side heat exchanger (Hx) (20) and at least one heat reservoir (31) is in fluid communication with the cold side heat exchanger (Cx) (30), wherein the heat pump system further comprises a recuperator intermediate and in fluid communication with the hot side heat exchanger (Hx) (20) and the cold side heat exchanger (Cx) (30), wherein the heat pump system comprises a hot store (22) intermediate the hot side heat exchanger (Hx) (20) and a heat reservoir (21).
  9. A heat pump system as claimed in any preceding claim, wherein the one or more heat reservoirs (21, 31) comprise one or more heat sources or heat sinks (21, 31), wherein the one or more heat sources or heat sinks (21, 31) include any one or more of the group comprising: ground loop, ground water, rivers, lakes, sea, air, water in mineshafts, buildings, district heating, greenhouses, swimming pools, sewage plants, supermarkets, fridges/freezers, solar absorbers, water tanks, Phase Change Material (PCM) batteries, wherein the heat pump system further comprises an internal heat exchanger (regenerator (Rx) (40), wherein the internal heat exchanger regenerator (40) is intermediate and in fluid communication with the hot side heat exchanger (Hx) (20) and the cold side heat exchanger (Cx) (30), wherein heat extracted from the cold reservoir (31) is stored in the hot store (22) when the heat pump system is in heat pump mode, wherein a plurality of heat sources and/or heat sinks (21, 21*) are connected to the hot store (22), wherein heat extracted from the hot store (22) is dissipated in a cold reservoir (31) when the heat pump system is in engine mode, wherein the heat pump system comprises one or more cold store(s) (32), wherein the one or more cold store(s) (32) are located intermediate the cold side heat exchanger Cx (30) and a respective cold reservoir (31), wherein heat extracted from the cold store (32) is stored in the hot store (22) when the heat pump system is in heat pump mode, wherein heat extracted from the hot store (22) is dissipated in the cold store (32) when the heat pump is in engine mode.
  10. A heat pump system as claimed in any preceding claim, wherein the regenerative thermal machine (1, 1*, 1**, 1***) is a Stirling cycle machine.
  11. A heat pump system as claimed in any preceding claim, further comprising a controller (350) adapted to control at least part of the heat pump system, wherein the controller (350) is configured to receive one or more input signals from said one or more inputs and is arranged to output one or more signals to control one or more components of the heat pump system, wherein the controller (350) is adapted to control the operation of the phase change means (160), wherein the controller (350) comprises an electronic control system, which permits the heat pump system to be tuned to one of:- i) the point of maximum efficiency, ii) the point of maximum thermal output, and iii) a point in between i) and ii) wherein the electronic control system provides a feedback electronic control system arranged to control the regenerative thermal machine (1, 1*, 1**, 1***) and enable the regenerative thermal machine (1, 1*, 1**, 1***) to interact with the electricity distribution grid (2), wherein the electronic control system is adapted to meet peak heating demand whilst meeting specified efficiency targets averaged over a particular period in time, wherein the electronic control system is adapted to change the power output by the regenerative thermal machine (1, 1*, 1**, 1***) and thereby reverse the operation of the regenerative thermal machine (1, 1*, 1**, 1***), such that the regenerative thermal machine (1, 1*, 1**, 1***) transforms between being a heat pump and a generator, wherein the electronic control system provides a feedback electronic control system arranged to control the regenerative thermal machine (1, 1*, 1**, 1***) and enable the regenerative thermal machine (1, 1*, 1**, 1***) to interact with the electricity distribution grid (2).
  12. A heat pump system as claimed in claim 11, wherein the feedback electronic control system enables the heat pump system to provide ancillary services to the electricity distribution grid (2) including one or more of:- a) Firm Frequency Response (FFR); b) Frequency Control by Demand Management (FCDM); c) Short Term Operating Reserve (STOR); d) Inertia; e) Reactive power; and f) Black Start.
  13. A method of providing ancillary services to an electricity distribution grid (2), the method comprising the steps of providing one or more heat pump system(s) as claimed in any one of claims 1 to 12 and operatively connecting said one or more heat pump system(s) to the electricity distribution grid (2).
  14. A method of providing ancillary services to an electricity distribution grid (2) as claimed in claim 13, the method comprising providing a plurality of heat pump systems and distributing said plurality of heat pump systems around the electricity distribution grid (2) in an aggregated distribution, the method further comprising the step of remotely activating the or each heat pump system(s), wherein the heat pump systems operate as part of a smart grid, wherein one or more of the heat pump systems are electronically controlled from one or more centralised location(s) which can control each individual heat pump system, wherein the method further comprises, in the event of a black out of at least a part of the electricity distribution grid (2), actuating one or more of the heat pump systems to change the operation of each said respective heat pump system into its respective engine mode and engaging the respective clutch (140) (if it is not already engaged) of each heat pump system to drive the respective electrical machine (130) of each heat pump system to provide a black start to the grid (2), wherein the method further comprises using thermal energy stored within any one or more than one of:- hot or cold stores (22, 32); and/or heat sources or heat sinks; (21, 31) and/or cold or hot reservoirs (21, 31) associated with the respective regenerative thermal machine (1, 1*, 1**, 1***) of the respective heat pump system, wherein the method further comprises using thermal energy provided by direct firing of a regenerative thermal machine (1, 1*, 1**, 1***) of the respective heat pump system with suitable fuel.
  15. An electricity distribution grid (2) comprising at least one or more heat pump systems as claimed in any one of claims 1 to 12.
  16. A method of operating an electrically connectable heat pump system, comprising:- providing a heat pump system comprising a regenerative thermal machine (1, 1*, 1**, 1***) in fluid communication with one or more heat reservoirs (21), wherein the regenerative thermal machine (1, 1*, 1**, 1***) comprises working fluid compression and expansion spaces (11, 12) and further comprises a phase change means (160) operable to change the phase relationship between the said working fluid compression and expansion spaces (11, 12) of the regenerative thermal machine (1, 1*, 1**, 1***); further providing an electrical machine (130) and electrically connecting said electrical machine (130) to an electricity distribution grid (2), and configuring said electrical machine (130) to interchangeably operate as a motor in which it receives electrical motive power from the electricity grid (2) in order to drive the regenerative thermal machine (1, 1*, 1**, 1***) in the heat pump mode, and operate as a regenerative thermal machine (1, 1*, 1**, 1***) driven generator to produce and feed electrical power into said electricity grid (2); and operating the phase change means (160) to change the phase relationship between the said working fluid compression and expansion spaces (11, 12) of the regenerative thermal machine (1, 1*, 1**, 1***); and further operating the phase change means (160) to change the operation of the regenerative thermal machine (1, 1*, 1**, 1***) seamlessly between a heat pump mode in which a drive mechanism (124) comprising an input/output drive end (125) of the regenerative thermal machine (1, 1*, 1**, 1***) is driven by the electrical machine (130), and an engine mode in which the input/output drive end (125) of the regenerative thermal machine (1, 1*, 1**, 1***) drives the electrical machine (130) to generate electricity, and vice versa, wherein the direction of rotation of the input/output drive end (125) of the drive mechanism (124) is maintained as the regenerative thermal machine (1, 1*, 1**, 1***) changes mode from heat pump to heat engine and vice versa.

Description

The present invention relates to a heat pump system incorporating a thermodynamic machine which preferably utilises the Stirling Cycle and which is usable as a heat pump and is optionally interchangeably usable as a heat pump and a heat engine, and an electricity distribution grid ancillary service support system comprising one or more of such heat pump systems, and preferably many of such heat pump systems aggregated throughout the electricity distribution grid. BACKGROUND TO THE INVENTION In order to fulfil commitment made upon signing the Paris Climate Agreement, many countries have set the ambitious target of reducing carbon dioxide emissions to 'net-zero' by 2050. To achieve 'net-zero' carbon dioxide emissions will involve fundamental changes to current means of generating and distributing electricity, heating homes and providing transportation. The greatest change can be considered to be the wholesale 'decarbonisation' of electricity generation, heating and transportation systems. As a result, electricity generation must evolve to become predominantly renewable, fossil fuelled boilers must be replaced by heat pumps and internal combustion engines in vehicles replaced with electric power. For example, it is planned that no gas boilers will be installed in new-build homes in the United Kingdom after 2025. However, a problem that is rarely discussed is that with increasing penetration of renewable technologies such as wind turbines and solar photovoltaic panels, electrical grids, for example the National Gird in the United Kingdom, are likely to become increasingly unstable. The loss of fossil-fuel power generation in itself is not the issue, but rather the loss of the associated large rotating machines will inevitably reduce the stability of future electricity networks. This is because traditional generators store kinetic energy in their rotating mass and this means of energy storage (often referred to as inertia) will be reduced as renewables penetration into the electricity grid system increases. In the event a large electrical load is placed on the distribution system, or if a large generator fails, the resulting imbalance between supply and demand is accommodated by the kinetic energy stored in rotating synchronous generators. In simple terms, the generators slow down slightly, giving up (a typically relatively small portion of) their stored kinetic energy, thus providing sufficient time for back-up systems to respond. Somewhat serendipitously, this type of energy storage provides a valuable advantage over to battery-based fast frequency response storage in that it does not depend on fast acting and robust communication systems, but rather is present for whenever it is needed. Future electricity systems, as currently envisaged, will have very low inertia and this is expected to lead to problems with grid stability and resilience. Electrical Systems Operators (ESOs) must therefore solve this problem if penetration of renewable generation is to continue to increase in line with government commitments.. High-inertia rotating stabilizer synchronous machines have been developed to help overcome the problem of instability in electrical grid networks. Rotating stabilizers can help stabilize frequency deviations by generating and absorbing reactive power and maintain grid performance by replicating the synchronous inertia response provided by traditional thermal power generation means such as coal or gas power plants. Manufactures of such stabilisers include GE Power Conversion. Energy converters utilising the Stirling Cycle (typically called "Stirling cycle machines") are also well known and come in various configurations. A typical so called "alpha" type Stirling cycle machine has two pistons reciprocating within respective cylinders. The cylinders are connected by a passage or network of passages accommodating three heat exchangers. The first (hot) heat exchanger is connected to a hot (typically hotter) reservoir, whilst the second (cold) heat exchanger is connected to a cold (typically colder) reservoir. The third heat exchanger, known as a regenerator, is located between said hot and cold heat exchangers. The pistons are both connected to a crankshaft and flywheel via a connecting rod and, possibly, a crosshead. A working fluid of constant mass, typically gas, is hermetically contained within the cylinders, connecting passages and the said three heat exchangers. One cylinder, also known as the hot cylinder or expansion cylinder1, is in fluid communication with the hot heat exchanger which heats the gas (adds heat). The other cylinder, also known as the cold cylinder or compression cylinder, is in fluid communication with the cold heat exchanger which cools the gas (extracts heat). The working fluid is cycled back and forth between the expansion cylinder and the compression cylinder, passing through the regenerator twice per cycle, whilst the regenerator alternately absorbs heat from, and releases heat