Work recovery in shape memory alloy heat pumps.

Abstract

A shape memory alloy heat pump system (20) and method comprising a first shape memory alloy core (21) and a second shape memory alloy core (22). A power conversion device (23) is connected to the first shape memory alloy core and the second shape memory alloy core, and a flywheel device (24) is configured to recover and store energy from the first shape memory alloy core when unloaded via the power conversion device and return the stored energy to the second shape memory alloy core when under load via the power conversion device.

Description

[Technical Field]

[0001] This disclosure relates to shape memory alloy (SMA) heat pumps, and more particularly to work recovery in solid-state SMA heat pumps. [Background technology]

[0002] Recent research into the elastocaloric (EC) effect has demonstrated its potential as a solid-state alternative to traditional vapor-compression refrigeration and / or heat pump approaches. EC cycles utilize the superelastic behavior of shape memory alloys, which facilitates the absorption of heat from a cold source and the rejection of that heat to a hot sink through cyclic uniaxial loading and unloading.

[0003] Heat pump (HP) technology is widely used commercially in heating, ventilation, air conditioning, and refrigeration (HVAC-R) applications. They can offer energy savings and emissions reductions and are typically deployed in heating and cooling systems in buildings, automobiles, and electronic equipment, for example.

[0004] Heat pumps using SMA materials in the form of SMA cores are known in the art. An exemplary SMA heat pump is disclosed in PCT Patent Application Publication No. WO 2021 / 219667, assigned to Exergyn Ltd. SMAs are alloys that retain their shape when deformed by an external force below a critical temperature, but recover their original shape after being heated to the critical temperature through a shape recovery force. SMAs, such as titanium-nickel alloys, are manufactured at elevated temperatures to achieve a predetermined shape. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 219667 Summary of the Invention [Problem to be solved by the invention]

[0006] The efficiency of a heat pump is determined by its COP or EER, where COP is the heat output divided by the work input, and EER is the cooling divided by the work input. Therefore, to increase the performance of a heat pump, the net work input must be reduced.

[0007] Due to the cyclical nature of state changes in SMA-based heat pump systems, it is desirable to make the system as energy-efficient as possible. Recovering the work done by uniaxial cyclic loading is an essential energy-efficient aspect of SMA heat pumps with two or more SMA cores. This cannot be easily achieved by connecting an SMA core in a high-energy state part of the cycle with a core in a low-energy state. This is because an equilibrium would be reached, thereby losing some or all of the work done. Additionally, mechanically loading the core and adding the energy storage mass to the core itself is technically very challenging. This approach is flawed because it requires hundreds of tons of mass and forces that exceed the ability to directly load it mechanically.

[0008] Therefore, there is a need for an SMA heat pump that improves work recovery in a multi-SMA core heat pump while minimizing energy losses, and this is an object of the present invention. [Means for solving the problem]

[0009] The present invention relates to an SMA-based heat pump system and a method of operating an SMA heat pump, as set out in the accompanying claims.

[0010] In one embodiment of the present invention, a shape memory alloy heat pump system is provided, the shape memory alloy heat pump system comprising: a first shape memory alloy core; a second shape memory alloy core; a power conversion device connected to the first shape memory alloy core and the second shape memory alloy core; and a flywheel device configured to recover and store energy from a first shape memory alloy core when unloaded via a power conversion device, and return the stored energy to a second shape memory alloy core when loaded via the power conversion device.

[0011] The present invention utilizes a power conversion device, such as a hydro-mechanical rotary converter, to store energy from an unloaded core as rotational kinetic energy in a flywheel device. This stored energy can then be reapplied to a loaded core through the hydro-mechanical converter to operate the core. The energy in a flywheel is proportional to the square of the rotational speed. Large torques are possible down to zero rotational speed, where the torque is converted to pressure by the hydro-mechanical converter and then converted to force on the core by a hydraulic cylinder. Therefore, the maximum force that can be applied to a loaded core is not limited by the amount of stored energy.

[0012] In one embodiment, the power conversion device is configured to convert linear mechanical energy into hydraulic energy and then into rotational mechanical energy.

[0013] In one embodiment, the power conversion device includes at least one hydraulic piston connected to the core and a hydraulic pump or motor.

[0014] In one embodiment, the power conversion device comprises at least one hydraulic piston connected to the core and a hydraulic cylinder connected to the linear-to-rotary conversion device.

[0015] In one embodiment, the power conversion device comprises a mechanical-hydrostatic-mechanical conversion device.

[0016] In one embodiment, the power conversion device comprises a mechanical system of pulleys that converts high force linear motion into low torque rotational motion.

[0017] In one embodiment, the power conversion device comprises a rotary cam system that converts linear motion to rotary motion.

[0018] In one embodiment, the power conversion device includes an electro-mechanical actuator having a motor-driven ball screw rod actuator, with a flywheel disposed between the motor and the ball screw rod.

[0019] In another embodiment of the present invention, there is provided a heat pump system, the heat pump system comprising: a first shape memory alloy core; a second shape memory alloy core disposed in fluid communication with the first shape memory alloy core; a hydro-mechanical converter connected to the first and / or second core; and a flywheel device configured to store energy from a first shape memory alloy core under no load via a hydraulic-mechanical conversion device and return the stored energy to a second shape memory alloy core under load via a hydraulic-mechanical conversion device.

[0020] In one embodiment, the power conversion device comprises a hydraulic pump / motor.

[0021] In one embodiment, the power conversion device comprises a hydraulic cylinder connected to a linear-to-rotary conversion device.

[0022] In one embodiment, the first and second cores are loaded and unloaded 180 degrees out of phase with each other.

[0023] In one embodiment, a pressure relief valve is connected to the high pressure fluid line of the first and / or second core and configured to prevent pressure buildup within the heat pump system.

[0024] In one embodiment, a check valve is connected to the low pressure fluid line and configured to allow the hydro-mechanical conversion device to draw fluid from the tank.

[0025] In one embodiment, an electric motor is connected to the flywheel to provide the energy input.

[0026] In one embodiment, a hydraulic motor is connected to the flywheel to provide the energy input.

[0027] It will be appreciated that the flywheel device provides torque to the hydro-mechanical conversion device, which is converted into pressure, which is converted by the hydraulic cylinder into force on the core and applied to the core during loading.

[0028] In one embodiment, the gearbox is located on one side of the flywheel device and is configured to optimize the rotational speed of the flywheel and the energy input device.

[0029] In one embodiment, a third shape memory alloy core is added and the valve assembly is connected to the first, second, and third shape memory alloy cores. It will be understood that any number of shape memory alloy cores can be used.

[0030] In one embodiment, the valve assembly includes a core isolation valve configured to allow three or more cores to operate.

[0031] In one embodiment, the valve assembly includes a core isolation valve configured for unidirectional operation of the hydraulic pump / motor.

[0032] In one embodiment, the control valves and check valves are configured to allow the hydraulic pump / motor to operate unidirectionally above zero rotational speed.

[0033] In one embodiment, the heat pump system includes a third shape memory alloy core and a fourth shape memory alloy core.

[0034] In one embodiment, the first, second, and third shape memory alloy cores operate 120 degrees out of phase with each other.

[0035] In another embodiment, a method of controlling operation of a shape memory alloy heat pump is provided, the method comprising: placing the first shape memory alloy core in fluid communication with the second shape memory alloy core via a hydro-mechanical conversion device; a flywheel device configured to recover and store energy from the shape memory alloy core during an unloaded state via a hydraulic-mechanical conversion device; providing stored energy to the shape memory alloy core under load via a hydro-mechanical conversion device.

[0036] In a further embodiment, there is provided a method of controlling operation of a shape memory alloy heat pump, the method comprising: disposing the first shape memory alloy core together with the second shape memory alloy core connected via a power conversion device; a flywheel device configured to recover and store energy from the shape memory alloy core during no load via a power conversion device; providing stored energy to the shape memory alloy core under load via a power conversion device.

[0037] In another embodiment, a shape memory alloy heat pump system is provided, the shape memory alloy heat pump system comprising: a first shape memory alloy core; a second shape memory alloy core arranged in fluid communication with the first shape memory alloy core; a mechanical-to-translational rotation converter connected to the first shape memory alloy core and the second shape memory alloy core; and a flywheel device configured to recover and store energy from the first shape memory alloy core under no load via, for example, an electrically powered mechanical-to-translational rotation converter, and return the stored energy to the second shape memory alloy core under load via the mechanical-to-translational rotation converter. The function of the electro-mechanical mechanical-to-translational conversion device is the same as that of the hydro-mechanical motor described above in this specification and claims. The electro-mechanical conversion device is suitable for lower operating forces.

[0038] In a further embodiment, a shape memory alloy heat pump system is provided, comprising: a shape memory alloy core; a hydraulic-mechanical or mechanical-translational-rotational conversion device connected to the shape memory alloy core; and a flywheel device configured to recover and store energy when the shape memory alloy core is unloaded via the hydraulic-mechanical or mechanical-translational-rotational conversion device, and return the stored energy to the shape memory alloy core via the hydraulic-mechanical or mechanical-translational-rotational conversion device during a load phase. [Brief explanation of the drawings]

[0039] The invention will be more clearly understood from the following description of embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a high-level system diagram of an SMA material-based heat pump system. [Figure 2] FIG. 1 is a block diagram illustrating the main components for achieving work recovery in an SMA-based heat pump. [Figure 3] FIG. 10 illustrates two SMA cores connected together using a hydraulic pump and flywheel circuit configuration, according to one embodiment of the present invention. [Figure 4]FIG. 10 illustrates two SMA cores connected together via a hydraulic cylinder connected to a linear-to-rotary converter and flywheel circuitry, according to one embodiment of the present invention. [Figure 5] FIG. 1 illustrates an SMA heat pump with multiple SMA cores actuated by hydraulic pistons and connected to a hydraulic-to-mechanical conversion device and a flywheel device using a control valve assembly. [Figure 6] FIG. 1 illustrates an SMA heat pump with multiple SMA cores actuated by hydraulic pistons and connected to a hydraulic-to-mechanical conversion device and a flywheel device using a control valve assembly. [Figure 7] FIG. 1 illustrates an SMA heat pump with multiple SMA cores actuated by hydraulic pistons and connected to a hydraulic-to-mechanical conversion device and a flywheel device using a control valve and check valve assembly. [Figure 8] FIG. 1 illustrates an SMA heat pump with multiple SMA cores actuated by hydraulic pistons and connected to a hydraulic-to-mechanical conversion device and a flywheel device using a control valve and check valve assembly. [Figure 9] FIG. 10 illustrates three SMA cores actuated by hydraulic pistons and connected together using hydraulic pump and flywheel circuitry, according to one embodiment of the present invention. [Figure 10a] 4 is a number of graphs illustrating various parameters during operation of the first and second SMA cores shown in FIG. 3; [Figure 10b] 4 is a number of graphs illustrating various parameters during operation of the first and second SMA cores shown in FIG. 3; [Figure 10c] 4 is a number of graphs illustrating various parameters during operation of the first and second SMA cores shown in FIG. 3; [Figure 10d] 4 is a number of graphs illustrating various parameters during operation of the first and second SMA cores shown in FIG. 3; [Figure 11a]10 is a number of graphs illustrating various parameters during operation of the three SMA cores shown in FIG. 9; [Figure 11b] 10 is a number of graphs illustrating various parameters during operation of the three SMA cores shown in FIG. 9; [Figure 11c] 10 is a number of graphs illustrating various parameters during operation of the three SMA cores shown in FIG. 9; [Figure 11d] 10 is a number of graphs illustrating various parameters during operation of the three SMA cores shown in FIG. 9; DETAILED DESCRIPTION OF THE INVENTION

[0040] The operation of heat pumps using SMA materials is known and fully described in PCT Patent Application Publication No. WO2019 / 149783, which is assigned to the present applicant and is incorporated herein by reference in its entirety. The present invention particularly relates to heat pump systems having two or more connected SMA cores. In the context of the present invention, it is envisioned that any number of SMA cores can be used in an SMA-based heat pump, according to various embodiments of the present invention.

[0041] Figure 1 is a high-level system diagram of an SMA material-based heat pump system generally designated by the reference numeral 10. A housing 11 contains two or more SMA cores in fluid communication with a heat sink 12 and a heat source 13, which can function as a heating or cooling system depending on the required application.

[0042] 2 is a block diagram illustrating the main components for achieving work recovery in an SMA-based heat pump according to the present invention. A power conversion device is suitably connected to the first shape memory alloy core and the second shape memory alloy core. A flywheel device is configured to recover and store energy from the first shape memory alloy core under no load via the power conversion device and return the stored energy to the second shape memory alloy core under load via the power conversion device. The power conversion device can be embodied in several different ways, as described with reference to the accompanying description and / or figures. The power conversion device enables efficient work recovery, which is applicable to any concept of loading an SMA core to convert high-force, low-speed linear motion into high-speed, low-torque rotational motion.

[0043] FIG. 3 shows a heat pump system, designated by reference numeral 20. Here, two SMA cores 21 and 22 are connected to each other using a power conversion device, such as a hydraulic pump circuit 23, and a flywheel circuit 24. The two cores 21 and 22 are directly connected to each other through the hydraulic pump 23, which does not have a control valve. The SMA cores 21 and 22 are actuated by hydraulic pistons 21a and 22a, respectively, which are connected to the hydraulic pump circuit 23 to form the power conversion device. The hydraulic pump circuit 23 is used to convert power from the fluid domain to the rotational mechanical domain. A flywheel device 24 is disposed on the pump shaft with a work input device (not shown) behind the flywheel. The work input device (not shown) can be powered by a battery, a power grid, or another suitable power source. The flywheel device 24 stores energy from the core when the core is unloaded and then supplies the energy to the core when it is loaded, increasing the pressure on the core when it is loaded. The work input device supplies energy to the system to compensate for the energy lost due to SMA hysteresis and system losses.

[0044] As the unload / load cycle for the SMA core begins, a large pressure difference develops across the hydraulic pump circuit 23, causing the pump to act as a motor, accelerating the shaft and the flywheel assembly 24, which in turn stores energy through the angular momentum of the flywheel assembly 24. As the pressures in the two cores equalize, the acceleration of the flywheel becomes zero, the rotational speed becomes maximum, and maximum energy is stored in the flywheel assembly. The hydraulic pump / motor now acts as a pump, drawing energy from the shaft and moving fluid from one core to the other, creating a pressure drop across them. This causes the flywheel assembly 24 to slow down. The flywheel provides the energy to pump fluid through the loaded core until the pressure is reached that is needed to bring the shaft rotational speed to zero. Then, the operation is reversed, and the rotational speed of the flywheel assembly 24 is also reversed.

[0045] The valveless hydraulic system, hydraulic pump / motor, flywheel device, and energy input device configuration provides an efficient method for operating or loading the core, as the only significant losses are the mechanical and hydraulic losses of the hydraulic pump / motor, which are typically very low. By utilizing a flywheel to store energy when the core is unloaded and return it when the core is loaded, the physical device can be much smaller, as only the flywheel experiences peak torque. Energy input devices, such as motors and inverters, can be sized and operated at constant power and constant torque, which means high component utilization and reduced size and cost. This results in excellent work recovery in the heat pump. It will be appreciated that in this embodiment, no valves are required for efficient loading of each core, while at the same time enabling efficient work recovery in the heat pump system.

[0046] Hydraulic pumps / motors can leak fluid into the tank as losses. Therefore, the fluid volume in the system will gradually decrease, requiring a check valve arrangement to allow the pump to draw fluid from the tank back into the system. Optionally, a pressure relief valve can be included as a safety measure to ensure that the system pressure remains below a critical level.

[0047] Figure 4 shows two SMA cores hydraulically connected to each other via a hydraulic cylinder 35 connected to a linear-to-rotation converter 36 and flywheel circuitry 24. The operation of Figure 4 is similar to that of Figure 3, except that the system uses a hydraulic cylinder and mechanical translation-to-rotation converter 36 to convert from the fluid domain to the rotational domain. The flywheel device 24 is then attached to a rotating shaft with a work input behind it. The hydraulic cylinder 35 has a cross-sectional area (Cross-Sectional Area: CSA) significantly smaller than that of the cores to reduce forces and increase speed in the system. The translation-to-rotation converter provides an additional mechanical advantage, increasing rotational speed and reducing load.

[0048] To further optimize the rotational speed, an optional gearbox may be installed on one side of the flywheel device 24. This can result in a reduction in the size of the flywheel device 24 and / or the work input device when the physical dimensions of the SMA heat pump are important.

[0049] Optional pressure relief valves 26, 27 are connected to the cores 21, 22, respectively, and are configured to prevent the heat pump system from overpressurizing.

[0050] In the embodiment of Figure 4, the hydraulic cylinder 35 has no fluid loss to the tank, so a check valve from the tank is essentially not required and the system can operate as a hermetically sealed system. If pressure relief valves are included and operated, the check valves 28, 29 allow the mechanical-hydraulic-mechanical converter to draw fluid from the tanks 30, 31 when there is no fluid remaining in the core.

[0051] Figures 5 and 6 show an SMA heat pump with multiple SMA cores connected to the mechanical-hydraulic-mechanical converter and flywheel device 24 using a control valve assembly 40. By adding a control valve assembly 40 to each core to isolate the cores, operation with more than two cores is possible. In the systems of Figures 5 and 6, the heat pump system can operate with multiples of two cores. The phase angle between the cores can be set to 360° / n cores, where "n" is the number of cores in the system and "n" is greater than or equal to three. At any given time, one core is off-load and one core is on-load, while the remaining cores are held either on-load or off-load.

[0052] Figure 5 shows a hydraulic pump / motor and flywheel system using a control valve assembly. In this system, the hydraulic pump / motor can operate in either a counter-rotating or unidirectional manner. However, to allow the valve time to change position, it must reach zero rotational speed at the end of each load / unload cycle, during which the valve is not open. The advantage of this system is that three or more cores can be operated with a phase difference of 360° / n cores.

[0053] Figure 6 is similar to Figure 5 and operates in the same way. The hydraulic pump / motor is replaced by a hydraulic cylinder 35 connected to a linear-to-rotary converter 36. The control valve assembly 40 operates in the same way to isolate different SMA cores between loaded and unloaded when there are more than two SMA cores in the system.

[0054] Figures 7 and 8 show an SMA heat pump with multiple SMA cores connected to a mechanical-hydraulic-mechanical converter, a flywheel device, check valve assemblies 41, 42, 43, and 44, and a control valve assembly 40. The addition of the check valve assemblies allows for continuous flow through the hydraulic pump, meaning the pump never reaches zero rotational speed. Another advantage is that it allows for an odd number of cores. Check valves 41, 42, 43, and 44 allow the valves of the next core under load to open before closing the previous core valve, allowing fluid to flow through the hydraulic pump 23 and keep the hydraulic pump above zero rotational speed. In this way, the system can be tuned to operate within the peak efficiency range of the hydraulic pump / motor and electric motor.

[0055] The configuration of Figure 8 operates similarly to the configuration of Figure 6, except that any number of cores can be operational, whereas in Figure 6 only an even number of cores are connected.

[0056] Figure 9 shows three SMA cores connected together using a hydraulic pump and flywheel circuit configuration according to the configuration shown in Figure 4. In the three-core system shown in Figure 9, valve assemblies 41, 42, and 43 are required to connect each core 21, 22, and 22a to either the pressure or return line of the hydraulic pump circuit 23. Preferably, for a three-core system, each core operates 120 degrees out of phase. The hydraulic pump circuit 23 rotates unidirectionally. A pressure relief valve 26 prevents the system from overpressurizing. A single check valve 29 allows the pump to draw from the tank 30 if one of the cores has no fluid remaining.

[0057] The combination of the hydraulic system and the valves means that the pump can be operated in one direction. For example, the connection to the core switching can be achieved in the following sequence: - 120° on the high pressure side of the pump -Separation 60° -Low pressure side of pump 120° -Separation 60°

[0058] Figures 10a to 10d show several graphs illustrating various parameters during operation of the first and second SMA cores shown in Figure 3. In these examples, times 454 to 466 are taken as one cycle.

[0059] Figure 10(a) shows the fluid inlet and outlet temperatures for each core. In this example, the cores are operating on a 12-second cycle, with the first and second cores 6 seconds, or 180 degrees, apart in phase. During the heating phase, the SMA material is compressed, causing the fluid stream to heat up, which can be seen in Figure 10(a) from time 454 to 460 for core 2. During the cooling phase, the load is released from the SMA material, causing the stream to cool, in this example from time 460 to 466 for core 2. The graph in Figure 10(b) shows a fully reversed hydraulic pump cycle, with the hydraulic fluid in core 1 being pumped from core 1 to core 2 from time 454 to 460. Initially, the fluid pressure in core 1 is very high and the fluid pressure in core 2 is very low. This large pressure delta is converted by the hydraulic motor into a large torque, which increases the rotational speed of the flywheel and thus inputs energy into the flywheel. At time 457 seconds, the fluid pressures in cores 1 and 2 are equal, so no torque is produced by the hydraulic motor. This is the highest rotational speed point in the cycle and, therefore, the point at which the most energy is stored in the flywheel. From 457 seconds to 460 seconds, the pressure in core 2 is higher than core 1, so the hydraulic pump must be activated to move the remaining fluid from core 1 to core 2. The energy previously stored in the flywheel is now used to drive the pump, slowing the rotational speed until it reaches zero and the flywheel energy is completely depleted. At this point, core 2 is fully operational and core 1 is completely unloaded. In Figure 9b, this process is then reversed from time 460 to 466, with energy being returned from core 2 to core 1 via the flywheel and pump, and it can be seen that the system works in reverse to accomplish this.

[0060] In an ideal system, there would be no losses and no hysteresis, so the system could theoretically continue indefinitely without any energy input. However, because materials have hysteresis, some of the energy applied to the material under load is converted to heat and is unavailable as work under no load. In addition, there are hydraulic losses due to friction and leakage, and flywheel losses due to friction and wind resistance. Therefore, energy must be input to keep the system running. As long as the total energy input to the system over the half cycle exactly matches the energy lost, the system will operate continuously from cycle to cycle.

[0061] Figure 10c shows the core stress versus time for each core in this example. In this case, zero stress means that the core is completely unloaded. The 1,000 MPa figure in this example represents a fully loaded core. It will be appreciated that the operable range is wide and not limiting; for example, some cores will be loaded below 200 MPa, while some will reach 1400 MPa.

[0062] Figure 10d shows the core strain, which is correlated with the stress and motor rotation speed and therefore naturally follows the same trend.

[0063] Figures 11(a) through 11(d) include several graphs showing various parameters during operation of the three SMA cores shown in Figure 9. Adding a third core to the system results in a heat exchanger utilization rate of nearly 100%, reducing the internal fluid temperature delta within the heat pump. As shown in Figure 11a, even though more heat output is achieved, the core temperature delta is much lower. Figure 11b shows the motor rotational speed during the cycle. While this rotational speed is much more consistent than that of the two-core example, the acceleration and deceleration patterns correlated with the storage and release of energy into the flywheel remain the same. Figure 11d shows the strain for each core. The rate of change of strain during loading and unloading is fairly constant due to the pump operating at a constant rotational speed. There is a constant maximum strain at one-sixth of the cycle and a constant minimum strain at one-sixth. Figure 11c shows the stress for each core. Unlike strain, stress changes continuously due to changes in temperature.

[0064] In the context of the present invention, the power conversion system used to provide a load to the SMA heat pump can take many forms, for example, hydraulic, electromechanical, or any other suitable means. The end result of all of these systems is the same: each system converts the very high force, low speed linear motion of the core into high speed, low torque rotational motion using energy input from a high speed rotating device such as an electric motor.

[0065] Each SMA core is loaded and unloaded like a spring, but with hysteresis. SMA cores have inherent spring-like properties due to the expansion and contraction of the SMA material between loading and unloading. Most of the energy input to load the SMA core is returned upon unloading the SMA core. It is desirable to have a work recovery system that efficiently recovers work during unloading, minimizing net work input and maximizing COP and EER. In effect, an SMA core connected to a flywheel device via a power conversion device can function as a mass-spring system. To load the SMA core, it is desirable to go from rest to full compression and return, or from rest to full extension and return.

[0066] Increased heat pump performance is possible through the use of SMA cores, power conversion devices, and flywheel devices. The following examples show how the mass of each SMA core in a mass-spring system can be calculated with and without a flywheel device. Example 1 - No flywheel device Required force: 950kN Displacement: 18mm Cycle time: 10 seconds Spring constant per core: Force / displacement = 52.78MN / m Total spring constant = 52.78 * 2 = 105.55MN / m Natural frequency=√(k / m)rad / sec Required mass: k / ((2*pi()) / 10)^2)=2.67e8kg

[0067] To reach a natural period of 10 seconds, the heat pump system would require a mass of approximately 267 kT. To put this into perspective, this is equivalent to the mass of 1,340 Boeing 747s, which is not feasible. Example 2 - With flywheel device

[0068] Using the same figures as in Example 1, the required inertia of a flywheel device using the present invention can be calculated. -Assuming two cores, a cycle time of 10 seconds, and a displacement of 0-18-0 mm. -Assuming a motor whose rotation speed varies from -3000 rpm to +3000 rpm. There is a displacement of 18mm over half the cycle (5 seconds), so the average velocity is 3.6mm / s. Because the vibration is sinusoidal, the peak velocity is 3.6*pi() / 2=5.655mm / s. Converting 3000 rpm to rad / sec gives us 314.159 rad / sec. Therefore, the effective gear ratio of the load system is 314.159 / 5.655e-3=55556.

[0069] When comparing mass / inertia values ​​against gear ratio, the gear ratio is squared, so to calculate the required flywheel inertia, we need 1.34e8 / (55556^2)=0.08663kg.m 2 This becomes:

[0070] In accordance with the present invention, the required heat pump pressure is 0.08663 kg.m when using an SMA core, power conversion device, and flywheel device. 2 Example 1, as shown, requires a huge and totally unworkable mass of 267kT, compared to a small and very workable inertia of 267kT.

[0071] It will be appreciated that the flywheel system can function with any number of cores, or even just one core if a suitable spring is utilized in place of the second core. As the number of cores in the system increases, more energy can be transferred directly from one core to the next, with the remaining energy being stored in the flywheel device.

[0072] In another embodiment, a PI(D) controller is provided to control the motor torque / power based on the measured peak load. If the peak load is too low, the controller increases the torque / power slightly. If the peak load is too high, the torque / power is decreased.

[0073] In the context of the present invention, it will be understood that the use of flywheels and power conversion devices for efficient and low-cost work recovery is applicable to any load concept that converts high-force, low-speed linear motion into high-speed, low-torque rotational motion. Non-limiting examples of such designs could include: -Hydraulic load system utilizing a hydraulic motor. -Hydraulic loading systems utilize hydraulic pistons with or without valves, where the hydraulic pistons act to connect multiple cores together, resulting in a reduction in force and an increase in rotational speed. A linear to rotary converter (e.g., a ball screw) is then added to convert linear motion to rotary motion. At this point, a flywheel can be added, or finally, a gearbox is added to further increase rotational speed, onto which the flywheel and motor are attached. -Mechanical pulley system, in which a system of pulleys and / or wires is used both to convert linear to rotary motion and to provide a significant mechanical advantage. -Mechanical cam systems where multiple cores are driven by a cam mechanism. Rotary cams can benefit from a high ratio gearbox fitted with a flywheel and motor. Linear oscillating cam systems require a linear to rotary converter such as a ball screw followed by an optional gearbox. Direct operation by an electro-mechanical actuator, for example a motor-driven ball screw actuator, where a flywheel is placed between the motor and the ball screw rod, and an optional gearbox is provided in addition to the ball screw to further increase the rotational speed. Direct operation by electro-mechanical actuators, e.g. motor-driven roller screw and rack-and-pinion actuator systems.

[0074] As used herein, the terms "comprise, comprise, comprised, and comprising" or any variation thereof, and the terms "include, includes, included, and including" or any variation thereof, are considered to be fully interchangeable and all of them should be given the broadest possible interpretation, and vice versa.

[0075] The invention is not limited to the embodiments described hereinabove, which may be varied in both structure and detail.

Claims

1. A shape memory alloy heat pump system, a first shape memory alloy core; a second shape memory alloy core; a power conversion device connected to the first shape memory alloy core and the second shape memory alloy core; A shape memory alloy heat pump system comprising: a flywheel device configured to recover and store energy from a first shape memory alloy core when unloaded via the power conversion device, and return the stored energy to a second shape memory alloy core when loaded via the power conversion device.

2. The heat pump system of claim 1 , wherein the power conversion device is configured to convert linear mechanical energy to hydraulic energy and then to rotational mechanical energy.

3. The heat pump system of claim 1 , wherein the power conversion device comprises at least one hydraulic piston connected to the core and a hydraulic pump or motor.

4. The heat pump system of claim 1 , wherein the power conversion device comprises at least one hydraulic piston connected to the core and a hydraulic cylinder connected to a linear-to-rotary conversion device.

5. The heat pump system of claim 1 , wherein the power conversion device comprises a mechanical-hydraulic-mechanical conversion device.

6. 10. The heat pump system of claim 1, wherein the power conversion device comprises a mechanical system of pulleys that converts high force linear motion to low torque rotational motion.

7. The heat pump system of claim 1 , wherein the power conversion device comprises a rotary cam system for converting linear motion to rotary motion.

8. 2. The heat pump system of claim 1, wherein the power conversion device comprises an electro-mechanical actuator having a motor-driven ball screw rod actuator, and the flywheel is disposed between the motor and the ball screw rod.

9. The heat pump system of claim 1 , wherein the first and second cores are loaded and unloaded 180° out of phase with each other.

10. 10. The heat pump system of claim 1, further comprising a pressure relief valve connected to the high pressure fluid line of the first and / or second core and configured to prevent pressure buildup within the heat pump system.

11. 11. The heat pump system of claim 1, further comprising a check valve connected to a low pressure fluid line and configured to allow the power conversion device to draw fluid from a tank.

12. 12. A heat pump system according to any preceding claim, comprising an electric motor connected to the flywheel to provide energy input.

13. 13. A heat pump system according to any preceding claim, comprising a hydraulic motor connected to the flywheel to provide energy input.

14. 14. The heat pump system of claim 1, wherein the flywheel device provides torque to the power conversion device, the torque being converted into pressure, and the pressure being converted into force on the core by the hydraulic cylinder and applied to the core during load.

15. 15. The heat pump system of claim 1, further comprising a gearbox arranged on one side of the flywheel arrangement and configured to optimize the rotational speed of the flywheel and the energy input device.

16. 16. The heat pump system of claim 1, comprising a valve assembly connected to each shape memory alloy core.

17. 17. The heat pump system of claim 16, wherein the valve assembly comprises a core isolation valve configured to maintain rotational regions operating in a unidirectional manner and to allow any even number of cores to operate.

18. 18. The heat pump system of claim 16 or 17, comprising control valves and check valves configured to maintain the rotating region operating in a unidirectional manner above zero rotational speed and to allow any number of cores to operate.

19. 19. The heat pump system of any one of claims 16 to 18, wherein the shape memory alloy cores operate out of phase with each other by an angle equal to 360° divided by the number of cores.

20. The heat pump system of claim 1 , comprising a third shape memory alloy core and a fourth shape memory alloy core.

21. 1. A method of controlling operation of a shape memory alloy heat pump, comprising: disposing a first shape memory alloy core together with a second shape memory alloy core connected via a power conversion device; a flywheel device configured to recover and store energy from the shape memory alloy core during no load through the power conversion device; providing the stored energy to a shape memory alloy core under load via the power conversion device.

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