EP3426905A1

EP3426905A1 - Stirling engine type energy generating system

Info

Publication number: EP3426905A1
Application number: EP17763658.6A
Authority: EP
Inventors: Torbjörn Birging; Lars Birging; Jan BJÖRKMAN
Original assignee: Zigrid AB
Current assignee: Zigrid AB
Priority date: 2016-03-07
Filing date: 2017-03-07
Publication date: 2019-01-16
Anticipated expiration: 2037-03-07
Also published as: SE1650297A1; SE541034C2; PL3426905T3; EP3426905B1; WO2017155452A1; EP3426905A4

Abstract

An energy generating system (1) comprising: a main piston system (V), comprising, a first cylinder (14) comprising a first reciprocatable piston (15), wherein the first piston (15) divides the first cylinder (14) into a first (14a) and second (14b) variable space, wherein the first space (14a) comprises a first fluid medium (140) a first energy transfer device (30a), a first heat exchanging system (11), a second cylinder (24) comprising a reciprocatable piston (25), wherein the second piston (25) divides the second cylinder (24) into a third (24a) and fourth (24b) variable space, wherein the third space (24a) comprises a second fluid medium (240), a second energy transfer device (30b), a second heat exchanging system (21) in fluid connection with the third space (24a), wherein the energy generating system (1) is adapted to synchronize heating of the first fluid medium (140) with cooling of the second fluid medium (240) whereby the first and second energy transfer devices (30a, 30b) transfer the kinetic energy from the reciprocating movement of the reciprocatable pistons (15,25) to an energy generating device (30). The second and fourth spaces are fluidly interconnected so that mechanical resistance is minimized.

Description

STIRLING ENGINE TYPE ENERGY GENERATING SYSTEM

Technica! field

[0001 ] The present invention relates generally to an energy generating system for generating energy from temperature differences of fluids.

Background art

[0002] It is known to use energy generating system for generating energy from temperature differences.

[0003] A drawback of known solutions is their limited ability and feasibility to sufficiently capture surplus of energy in temperature intervals for instance provided by waste heat in industrial processes or natural temperature difference in the environment.

Summary of invention

[0004] An object of the present invention is to alleviate some of the

disadvantages of the prior art and to provide an energy generating system which transforms low temperature energy to kinetic energy based on temperature differences. A further object of the present invention is to provide an energy generating system which transforms energy from temperature differences wherein the warm side of the temperature difference exist below zero degrees Celsius. A further object of the present invention is to provide an energy generating system having a modular design adaptable to need and requirements.

[0005] According to one embodiment of the invention, an energy generating system is provided, comprising: a main piston system, further comprising, a first cylinder comprising a first reciprocatable piston, wherein the first piston sealably divides the first cylinder into a first and second variable space, wherein the first space comprises a first fluid medium and the second space comprises a fluid medium, a first energy transfer device connected to the first cylinder, a first heat exchanging system in fluid connection with the first space, wherein the first heat exchanging system is adapted to alternately heat and cool the first fluid medium, whereby pressure in the first space is increased and reduced respectively, a second cylinder comprising a reciprocatable piston, wherein the second piston sealably divides the second cylinder into a third and fourth variable space, wherein the third space comprises a second fluid medium and the fourth space comprises a fluid medium, a second energy transfer device connected to the second cylinder, a second heat exchanging system in fluid connection with the third space, wherein the second heat exchanging system is adapted to alternately heat and cool the second fluid medium, whereby pressure in the third space is increased and reduced respectively, wherein the energy generating system is adapted to control heating of the first fluid medium and cooling of the second fluid medium and conversely cooling of the first fluid medium and heating of the second fluid medium, whereby the resulting pressure increase from heating and pressure reduction from cooling in the first space and the third space respectively, causes the first piston and the second piston to reciprocate between an expansion movement during heating wherein the first and third variable spaces increases, and a compression movement during cooling wherein the first and third variable spaces decreases, whereby the first and second energy transfer devices transfer kinetic energy from the reciprocating movement of the reciprocatable pistons to an energy generating device arranged for being in an energy-transfer connection to the first and second reciprocatable pistons, whereby during the expansion movement of the first piston the fluid medium is forced out of the second space as well as into the fourth space aiding the compression movement of the second piston, and whereby during the expansion movement of the second piston the fluid medium is forced out of the fourth space as well as into the second space aiding the compression movement of the first piston 15.

[0008] According to one embodiment, the first and second energy transfer devices comprises a first and second fluid line respectively, respectively

connecting the second variable space and fourth variable space with a further piston system, whereby the fluid lines, transfers the kinetic energy of the

reciprocatable pistons via the further piston system, to the energy generating device. [0007] According to one embodiment, the second and fourth variable spaces of the main piston system, via the fluid lines are in fluid connection with a first cylinder of the further piston system via a valve device, and wherein the second and fourth variable spaces of the main piston system, via the fluid lines are in fluid connection with a second cylinder of the further piston system via a valve device, wherein the valve devices are controlled by a valve control unit.

[0008] According to one embodiment, the first cylinder of the further piston system comprises a reciprocatable piston, sealab!y dividing the cylinder into a first and second variable space, wherein the first space comprises a fluid medium, and the second space comprises a fluid medium, wherein the second cylinder of the further piston system comprises a reciprocatable piston, sealably dividing the second cylinder into a third and fourth variable space, wherein the third space comprises a fluid medium, and the fourth space comprises a fluid medium, wheresn the second space is in fluid connection with the fourth space, wherein the second and fourth variable spaces of the main piston system, via the fluid lines, are in fluid connection with the first and third variable spaces of the further piston system,

[0009] According to one embodiment, the second and fourth spaces of the main piston system are in fluid connection with a plurality of further pistons systems, comprising at least a first and second further piston system, in a similar

arrangement as described in claims 2-4,

[0010] According to one embodiment, a movement cycle of the reciprocation of the pistons of the further piston system is time shifted in relation to the cycle time of at least one of the plurality of further piston systems,

[001 1 ] According to one embodiment, the energy generating system further comprising a second main piston system similar to the first piston system according to any of the preceding claims 1 -14, wherein the second main piston system is arranged to the further piston system according to claims 2-4, whereby the first and second energy transfer devices of the second main piston system transfer the kinetic energy from the reciprocating movement of the reciprocatable pistons to the energy generating device arranged for being in an energy-transfer connection to the first and second reciprocatable pistons, wherein a movement cycle of the reciprocation of the pistons of the second main piston system is time shifted in relation to the movement cycle of the pistons of the first main psston system.

[0012] According to one embodiment, the energy generating system further comprising a second main piston system similar to the first main piston system according to any of the embodiments described herein, wherein the second main piston system is arranged to the second further piston system, according to any of the embodiments described herein, wherein a movement cycle of the reciprocation of the pistons of the second main piston system is time shifted in relation to the movement cycle of the pistons of the first main piston system.

[0013] According to one embodiment, a preload cylinder, similar to the first cylinder of the further piston system as described in any of the embodiments herein, is arranged in fluid connection with the second space and the fourth variable space of the first cylinder of the further piston system for generating a preload to the fluid of the second space and the fourth variable space.

[0014] According to one embodiment, the first energy transfer device is connected to the first reciprocatable piston, and the second energy transfer device is connected to the second reciprocatable piston, wherein the second space is in fluid connection with the fourth space, whereby during expansion movement of the first piston the fluid medium is forced out of the second space into the fourth space aiding a compression movement of the second piston so that the third space is decreased, and whereby during expansion movement of the second piston the fluid medium is forced out of the fourth space into the second space aiding a compression movement of the first piston so that the first space is decreased.

[0015] According to one embodiment, the first heat exchanging system comprises a first heat exchanger, comprising a first valve to which a line for a hot medium and a line for cold medium is connected for selectively receiving a hot medium and a cold medium into the first heat exchanger, wherein the second heat exchanging system comprises a second heat exchanger comprising a second valve to which a line for a hot medium and a line for a cold medium is connected for selectively receiving a hot medium and a cold medium into the second heat exchanger, wherein the first and second valves are controlled by a valve control unit.

[0016] According to one embodiment, the first heat exchanger is in fluid connection with the cylinder via a third valve, and the second heat exchanger is in fluid connection with the cylinder via a fourth valve, wherein the opening and closing of valves are controllable by the valve control unit.

[0017] According to one embodiment, the first heat exchanging system and the second heat exchanging system comprises two separate heat exchangers respectively, wherein a first heat exchanger of the first system is adapted to heat the first fluid medium, and a first heat exchanger of the second system is adapted to heat the second fluid medium, and a second heat exchanger of the first system is adapted to cool the first medium, and a second heat exchanger of the second system is adapted to cool the second fluid medium.

[0018] According to one embodiment, the first heat exchanging system is arranged within the first variable space of the cylinder, and/or the second heat exchanging system is arranged within the third variable space of the cylinder.

[0019] According to one embodiment, the first heat exchanging system is arranged externally of the cylinder, and/or the second heat exchanging system is arranged externally of the cylinder.

[0020] According to one embodiment, the fluid medium of the second space and the fluid medium of the fourth space is an incompressible liquid.

[0021 ] According to one embodiment, the fluid medium of the first space and the fluid medium of the third space is an incompressible liquid.

[0022] According to one embodiment, the fluid medium of the second space and the fluid medium of the fourth space is an incompressible liquid. [0023] According to one embodiment, the liquid is oil.

[0024] According to one embodiment, the fluid medium, is propane or R410A.

[0025] According to one embodiment, the fluid medium, undergoes a phase transfer from a gaseous phase into a liquid phase during the compression movement and back into a gaseous phase during the expansion movement.

[0026] According to one embodiment, the fluid medium is a gaseous medium, e.g. nitrogen.

[0027] According to one embodiment, the fluid medium comprises a gaseous medium.

[0028] According to one embodiment, the hot medium is hot water and the cold medium is cold water.

[0029] According to one embodiment, the energy transfer devices comprises one of a mechanical transfer device such as a crank-link mechanism, magnets or coils.

[0030] According to one embodiment, the energy generating device comprises one of a rotating shaft in a crank-link mechanism, magnets, coils, and a generator.

[0031 ] According to one embodiment, the energy generating system is adapted to control heating of the first fluid medium substantially simultaneously with cooling of the second fluid medium and conversely cooling of the first fluid medium substantially simultaneously heating of the second fluid medium,

Brief description of drawings

[0032] The invention is now described, by way of example, with reference to the accompanying drawings, in which: [0034] Fig. 2 shows a side view of an energy generating system.

[0035] Fig. 3a shows a side view of an energy generating system.

[0036] Fig. 3b shows a side view of a check valve.

[0037] Fig. 3c shows a side of the check valve of Fig. 3b. .

[0038] Fig. 3d shows a side view of the check valve of Fig. 3b.

[0039] Fig. 3e shows a side view of an energy generating system.

[0040] Fig. 4a shows a side view of an energy generating system.

[0041 ] Fig. 4b shows a side view of an energy generating system.

[0042] Fig. 5a shows a side view of an energy generating system,

[0043] Fig. 5b shows a side view of an energy generating system,

[0044] Fig. 6 shows a side view of an energy generating system.

[0045] Fig. 7 shows a side view of an energy generating system.

[0046] In the following, a detailed description of the invention will be given. In the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. It will be appreciated that these figures are for illustration only and are not in any way restricting the scope of the invention.

[0047] Fig. 1 shows a side view of an energy generating system 1 for generating energy from temperature differences of fluids. According to one embodiment, the energy generating system 1 comprises a first cylinder 14 comprising a first reciprocatable piston 15, wherein the first piston 15 sealably divides the first cylinder 14 into a first 14a and second 14b variable space, wherein the first space 14a comprises a first fluid medium 140 and the second space 14b comprises a fluid medium 145. Further, the energy generating system 1 comprises a first energy transfer device 30a connected to the first cylinder 14.

[0048] The energy generating system 1 further comprises a first heat

exchanging system 1 1 in fluid connection with the first space 14a, wherein the first heat exchanging system 1 1 is adapted to alternately heat and cool the first fluid medium 140, whereby pressure in the first space 14a is increased and reduced respectively, a second cylinder 24 comprising a reciprocatable piston 25, wherein the second piston 25 sealably divides the second cylinder 24 into a third 24a and fourth 24b variable space, wherein the third space 24a comprises a second fluid medium 240 and the fourth space 24b comprises a fluid medium 245. The energy generating system 1 further comprises a second energy transfer device 30b connected to the second cylinder 24, and a second heat exchanging system 21 in fluid connection with the third space 24a, wherein the second heat exchanging system 21 is adapted to alternately heat and cool the second fluid medium 240, whereby pressure in the third space 24a is increased and reduced respectively, wherein the energy generating system 1 is adapted to control heating of the first fluid medium 140 and cooling of the second fluid medium 240 and conversely cooling of the first fluid medium 140 and heating of the second fluid medium 240, whereby the resulting pressure increase from heating and pressure reduction from cooling in the first space 14a and the third space 24a respectively, causes the first piston 15 and the second piston 25 to reciprocate between an expansion movement during heating wherein the first and third variable spaces 14a, 24a increases, and a compression movement during cooling wherein the first and third variable spaces 14a, 24a decreases, whereby the first and second energy transfer devices 30a, 30b transfer the kinetic energy from the reciprocating movement of the reciprocatable pistons 15, 25 to an energy generating device 30 arranged for being in an energy-transfer connection to the first and second reciprocatable pistons 15, 25. According to one embodiment, during the expansion movement of the first piston 15 the fluid medium 145, 245 is forced out of the second space 14b as well as into the fourth space 24b aiding the compression movement of the second piston 25, and whereby during the expansion movement of the second piston 25 the fluid medium 145, 245 is forced out of the fourth space 24b as well as into the second space 14b aiding the compression movement of the first piston 15.According to one embodiment, the energy generating system 1 is adapted to control heating of the first fluid medium 140 substantially simultaneously with cooling of the second fluid medium 240 and conversely cooling of the first fluid medium 140 substantially simultaneously with heating of the second fluid medium 240.

[0049] According to one embodiment, the energy generating system 1 is adapted to synchronize heating of the first fluid medium 140 with cooling of the second fluid medium 240 and conversely cooling of the first fluid medium 140 with heating of the second fluid medium 240, whereby the resulting pressure increase from heating and pressure reduction from cooling in the first space 14a and the third space 24a respectively, causes the first piston 15 and the second piston 25 to reciprocate between an expansion movement during heating wherein the first and third variable spaces 14a, 24a increases, and a compression movement during cooling wherein the first and third variable spaces 14a, 24a decreases, whereby the first and second energy transfer devices 30a, 30b transfer the kinetic energy from the reciprocating movement of the reciprocatable pistons 15, 25 to an energy generating device 30 arranged for being in an energy-transfer connection to the first and second reciprocatable pistons 15, 25,

[0050] According to one embodiment, the stroke length of the reciprocatable pistons 15, 25 are 50-70cm,

[0051 ] According to one embodiment, the first and second fluid medium 140, 240 is propane or R410A. According to one embodiment, the selection of the fluid medium is dependent on the temperature range of the mediums of the heat exchanging systems, 1 1 , 21 . According to one embodiment, the first fluid medium 140 and second fluid medium 240 is a first gaseous medium 140 and second gaseous medium 240 respectively. According to one embodiment, the fluid medium 140, 240 undergoes a phase transfer from a gaseous phase into a liquid phase during the compression movement and back into a gaseous phase during the expansion movement,

[0052] According to one embodiment, the pressure of the first and second fluid medium during heating, i.e. as a result of the pressure increase, is 15-16 Bar or 1 ,5-1 ,6 MPa when using propane. According to one embodiment, the pressure of the fluid medium during heating, i.e. as a result of the pressure increase, is 30-40 Bar or 3-4 MPa when using propane. According to one embodiment, the pressure of the fluid medium during cooling, i.e. as a result of the pressure reduction, is 2-4 Bar or 0,2-0,4 MPa when using propane. According to one embodiment, the pressure of the fluid medium during cooling, i.e. as a result of the pressure reduction, is 2-4 Bar or 0,2-0,4 MPa when using propane.

[0053] According to one embodiment, the fluid medium 145 of the second space 14b and the fluid medium 245 of the fourth space 24b is an incompressible liquid. According to one embodiment, the liquid is oil. According to one embodiment, the fluid medium 145, 245 comprises a gaseous medium.

[0054] According to one embodiment, the energy transfer devices 30a, 30b, 30c, 30d comprises one of a mechanical transfer device such as a crank-link mechanism, magnets or coils. According to one embodiment, the energy generating device 30 comprises one of a rotating shaft in a crank-link mechanism, magnets, coils, and a generator, for generating energy from the movement of the reciprocatable pistons 15, 25,35, 45.

[0055] According to one embodiment, the first energy transfer device 30a is connected to the first reciprocatable piston 15, and the second energy transfer device 30b is connected to the second reciprocatable piston 25, wherein the second space 14b is in fluid connection with the fourth space 24b, whereby during expansion movement of the first piston 15 the fluid medium is forced out of the second space 14b into the fourth space aiding a compression movement of the second piston 25 so that the third space is decreased, and whereby during expansion movement of the second piston 25 the fluid medium is forced out of the fourth space 24b into the second space 14b aiding a compression movement of the first piston 15 so that the first space is decreased. According to one embodiment, an expansion tank 75 is adapted to be in fluid connection with the second space 14b and the fourth space 24b. According to one embodiment, the expansion tank 75 is provided between the second space 14b and the fourth space 24b. According to one embodiment, the expansion tank 75 provides for the fluid medium 145, 245 to enter the expansion tank 75 during an expansion movement of either the first piston 15 or the second piston 25. According to one embodiment, the expansion tank may be closed and comprising a gaseous medium such as e.g. air, having a bias pressure, wherein during entering of the fluid medium 145, 245, the gaseous medium is compressed further. According to one embodiment, this provides for a delaying of aiding a compression movement of the second piston or the first piston 15 respectively after the expansion movement has been initiated by the first piston 15 or the second piston 25 respectively. This enables the further cooling of the fluid medium 240 and 140 respectively before aiding of the compression movement may take place.

According to one embodiment, this provides for a more energy efficient process wherein the compression movement does not provide an unwanted and unnecessary counteraction to the expansion movement. According to one embodiment, this further enables the movement of the pistons 15 and 25 respectively to be asynchronous.

[0056] According to one embodiment, the first heat exchanging system 1 1 comprises a first heat exchanger 1 1 a, comprising a first valve 12 to which a line 12a for a hot medium and a line 12b for cold medium is connected for selectively receiving a hot medium, such as e.g. a fluid, and a cold medium, such as e.g. a fluid, into the first heat exchanger 1 1 , wherein the second heat exchanging system 21 comprises a second heat exchanger 21 a comprising a second valve 22 to which a line 22a for a hot medium and a line 22b for a cold medium is connected for selectively receiving a hot medium and a cold medium into the second heat exchanger 21 . According to one embodiment, the first and second valves 12, 22 are controlled by a valve control unit 50. According to one embodiment, the hot medium is hot water and the cold medium is cold water. According to one embodiment, the cold medium has a temperature of 4°-10°. According to one embodiment, the hot medium has a temperature of 15°-40°. According to one embodiment, the temperature difference between the hot medium and cold medium, ΔΤ, is in the range of 20X-5°C difference. According to one embodiment, the warm side if the temperature difference exist below zero degrees Celsius. According to one embodiment, the cold water is ground water. According to one embodiment, the hot water is waste water or water heated by being exposed to solar energy or more specifically by means of solar collectors. According to one embodiment, the cold medium has a temperature down to 4°C to -10°C. According to one embodiment, the hot medium has a temperature that are sufficient to realize a temperature difference between the hot medium and cold medium, ΔΤ, in the range of 10°C or more.

[0057] According to one embodiment, as seen in Fig. 1 , the first heat exchanger 1 1 is in fluid connection with the cylinder 14 via a third valve 13, and the second heat exchanger 21 is in fluid connection with the cylinder 24 via a fourth valve 23, wherein the opening and closing of valves 13, 23 are controllable by the valve control unit 50.

[0058] Fig. 2 discloses the energy generating system 1 of Fig. 1 , wherein the third valve 13 and the fourth valve 23 have been removed and the first heat exchanger 1 1 is in direct fluid connection with the cylinder 14, and the second heat exchanger 21 is in direct fluid connection with the cylinder 24.

[0059] Fig. 1 and Fig. 2 discloses the energy generating system 1 wherein the first heat exchanging system 1 1 is arranged externally of the cylinder 14, and/or the second heat exchanging system 21 is arranged externally of the cylinder 24.

[0060] According to one embodiment, the first heat exchanging system 1 1 and the second heat exchanging system 21 comprises two separate heat exchangers respectively (not shown), wherein a first heat exchanger of the first system 1 1 is adapted to heat the first 140 fluid medium, and a first heat exchanger of the second system 21 is adapted to heat the second 240 fluid medium, and a second heat exchanger of the first system 1 1 is adapted to cool the first medium 140, and a second heat exchanger of the second system 21 is adapted to coo! the second 240 fluid medium.

[0061 ] Fig. 3a discloses the energy generating system of Fig. 1 , wherein the first heat exchanging system 1 1 is arranged within the first variable space 14a of the cylinder 14, and/or the second heat exchanging system 21 is arranged within the third variable space 24b of the cylinder 24. According to one embodiment, a control valve 76a or 76b is provided and arranged in the fluid connection between the second space 14b and the fourth space 24b, for instance as described in the energy generating systems of Fig. 2 and 3, wherein the third valve 13 and the fourth valve 23 have been removed and the first heat exchanger 1 1 is in direct fluid connection with the cylinder 14, and the second heat exchanger 21 is in direct fluid connection with the cylinder 24. According to one embodiment, a valve control unit 50 is adapted to control the opening and closing of the control valve 76a, 76b. According to one embodiment, the control valve 76 when closed provides for a buildup of pressure of the first fluid medium 140 resulting from the heating of the first fluid medium 140 and prior to the expansion movement of the first piston 15. After sufficient reduction of the temperature of the second fluid medium 240, the control valve 76 may be opened to give a boost to the

compression movement of the second piston 25 sufficient to compress the second fluid medium to undergo a phase transfer and provide for even further

compression movement resulting from the sudden reduction in volume of the third variable space 24a. Naturally, an analogous process is occurring during the expansion movement of the second piston 25 instead. According to one

embodiment, as shown in Fig. 3a, a first control valve 76a and a second control valve 76b are provided and arranged in the fluid connection between the second space 14b and the fourth space 24b, for instance as described in the energy generating systems of Fig. 2 and 3. According to one embodiment, a valve control unit 50 is adapted to control the opening and closing of the control valve 76a and 76b. According to one embodiment, the first valve 76a and second valve 76b are arranged on either side of a expansion tank 75 or on either side of a common connection line to an expansion tank 75 as shown in Fig. 3a.. According to one embodiment, the first cylinder 14 comprises a first check valve 141 , and the second cylinder 24 comprises a second check valve 241 , arranged between the first piston 15 and the heat exchanging system 1 1 and the second piston 25 and the heat exchanging system 21 respectively. According to one embodiment the first 141 and second 241 check valves are adapted to lower the pressure and temperature of the first medium 140 and second medium 240 respectively when the fluid mediums 140, 240 pass through the check valves 141 , 241 in an unfolded position. According to one embodiment, the first check valve 141 is in a folded position, and the second check valve 241 is in an unfolded position in Fig. 3a. According to one embodiment, the first and second check valves 41 , 241 are arranged in the cylinders 14, 24 just below the lowermost position of the pistons 15, 25 in their lowermost compressed positions.

[0062] Fig. 3b shows a check valve such as a first and second check valve 141 , 241 in an unfolded position, seen in a direction from the piston 15, 15 towards the heat exchanging systems 1 1 , 21 . According to one embodiment, the first and second check valves 14 , 241 are essentially circular to fit snugly inside the cylinders 14, 24 cross section and are separate into two portions 141 a, 241 a, 141 b, 241 b connected by a hinge device 142, 242 which enables the check valve 141 , 241 by its first portions 141 a, 242a and second portions 141 b, 241 b, to swing in relation to each other between an unfolded position and a folded position.

According to one embodiment, the hinge device 142, 242 comprises two separate hinges 142a, 242a, 142b, 242b. According to one embodiment, the check valves 141 , 241 are provided with holes 143, 243. According to one embodiment, the holes have a larger entry diameter 143a, 243a than exit diameter 143b, 243b seen in a direction from the piston 5, 15 towards the heat exchanging systems 1 1 , 21 , wherein the holes form passages in the form of restrictions or throttles. According to one embodiment, the circumference of the portions 141 a, 241 a are tapered wherein a slit formed between the portions 141 a, 241 a is provided with a larger entry area than exit area, and wherein the circumference of the portions 141 a, 241 a facing the inner wall of the cylinders 14, 24 is provided with a larger entry area than exit area. These passages form restrictions or throttles. [0083] Fig 3c shows a side view of the check valve 141 , 241 of Fig. 3b in an unfolded position.

[0064] Fig. 3d shows a side view of the check valve 141 , 241 of Fig. 3b in a folded position. According to one embodiment, a process of use may be described as follows: When the first and second fluid mediums 140, 240 expands and move upwards in the respective cylinder 14, 24, the check valve 141 , 241 is swung from an unfolded towards a folded position wherein the fluid mediums 140, 240 may pass unhindered. When the fluid mediums 140, 240 shrinks the check valve 141 , 241 falls down to an unfolded position and becomes essentially planar wherein the fluid medium 140, 240 is forced to pass through all restrictions towards the heat exchanging systems 1 1 , 21 . During passage of the restrictions the temperature and pressure of the fluid mediums 140, 240 is reduced. According to one embodiment, the use of check valves 141 , 241 reduces the requirement of the temperature of the cold medium. According to one embodiment, no cold medium is required, only a hot medium, for the energy generating system 1 . Herein, the first heat exchanging system 1 1 also comprises the first check valve 141 adapted to cool the first fluid medium 140, and further comprises the second check valve 241 adapted to cool the second fluid medium 240. According to one embodiment, a process of the energy generating device 1 comprising the control first valve 76a and second control valve 76b and the expansion tank 75 may be described as follows: I n a starting position, the first piston 15 is in its lowermost and compressed position in the first cylinder 14. The second piston 25 is in its uppermost, expanded position, in the second cylinder 25. The first control valve 78a and second control valve 76b are closed. The first valve 12 is open to the line 12a wherein the first heat exchanging system 1 1 receives a hot medium, heating the first medium 140. The second valve 22 is open to a line 22b wherein the second heat exchanging system 21 receives a cold medium, colder than the hot medium, cooling the second medium 240. Essentially, the pressure of the first space 14a is at its highest level, and the pressure of the third space 24a is at its lowest level.

According to one embodiment, a first and second check valve 141 , 241 are provided, wherein the check valves 141 , 241 are in an unfolded position.

Hereafter, the first and second control valves 76a and 76b are opened simultaneously. The first check valve 141 is automatically opened, i.e. folded by the aid of the expansion of the first fluid medium 140. The first piston 15 is pressed upwards in an expansion movement, where the first energy transfer device 30a transfers the kinetic energy from the movement of the first piston 15 to the energy generating device 30. During this movement, the first piston 15 also presses the fluid medium 145 into the fourth space 24b where an overpressure is created pressing the second piston 25 downwards in a compression movement. The second piston 25 then simultaneously generates a higher pressure on the second medium 240 in the third space 24a than it adopted during cooling wherein the second fluid medium may undergo a phase change into liquid form which further reduces the volume of the second fluid medium 240 which, in turn, enables the compression movement of the second piston 25 to its lowermost position in the cylinder 24. When the second fluid medium 240 is pressed or forced through the unfolded check valve 241 , the cooling of the second medium 240 is enhanced, whereby the phase change of the fluid medium from gaseous state to a liquid state is accelerated. The pressure, driving the first piston 15 upwards during the expansion movement can be counteracted by that the shrinking process taking place in the third space 24a, and consequently the compression movement of the second piston 25 towards the lowermost position in cylinder 24, is a slower process. This may be overcome by the aid of the expansion tank 75 and/or the proper selection of the fluid medium 145, 245 allowing these fluid mediums to be compressed. When the first piston 15 reaches its uppermost expanded position, the first control valve 76a is closed, and the first valve 12 is opened towards the line 12b wherein a cold medium is received in the heat exchanging system 1 1 . When the second piston 25 reaches its lowermost position during the compression movement, the second control valve 78b is closed and the second valve 22 is opened towards the line 22a wherein hot medium is received in the heat exchanging system 21 . According to one embodiment, when the first and second mediums 140 and 240 has reached the temperature corresponding to the temperature of the hot and cold mediums flowing into and through the heat exchanging systems 1 1 and 21 respectively, the above process is repeated in the opposite direction, i.e. wherein the second piston 25 carry out the expansion movement and the first piston carry out the compression movement, with required controlling of the valves 12, 22, 76a and 76b, According to one embodiment, the energy transfer devices 30a, 30b transfer the kinetic energy into a rotating movement of the energy generating device 30, According to one embodiment, the energy transfer devices 30a, 30b are adapted to rotate the energy generating device during both their expansion movement and compression movement by e.g. a gear device. According to one embodiment, a plurality of further main piston systems 1 " as shown in Fig. 5, 6, 7 adapted to carry out the above process in an alternating manner, are provided and connected to the energy generating device 1 via energy transfer devices 30a, 30b in order to provide a continuous rotating movement of the energy generating device 1 .

[0065] Fig. 3e shows the energy generating system 1 according to one embodiment, wherein a respective cooling circuit 90a, 90b is provided to cool the first cylinder 14 and the second cylinder 24 respectively. According to one embodiment, the same source of cooling medium provided to the heat exchanging systems 1 1 and 21 are also provided to the cooling circuits 90a, 90b. According to one embodiment, the cooling circuits 90a, 90b are adapted to continuously cool the first cylinder 14 and the second cylinder 24 respectively. According to one embodiment, the cooling circuits are arranged to the cylinders 14, 24 whereby cooling of the portions of the cylinders covering the first space 14a and third space 24a in the most compressed position of the respective first and second piston 15 and 25 are avoided. As a result, the negative effect of unwanted cooling of these spaces 14a, 24a during the initial part of the expansion movement when the first and second fluid mediums 140 and 240 are heated by the hot medium is avoided. As a result, the process of compression movement of the first and second pistons 15 and 25 respectively is improved in that the time for lowering the temperature of the first and second fluid mediums 140 and 240 respectively and achieving a phase change of the same mediums is reduced. According to one embodiment, the process of compression and phase change from a gaseous state to a liquid state is more time consuming than the process of expansion and phase change from a liquid state to a gaseous state. According to one embodiment, the process of compression and phase change from a gaseous state to a liquid state is more time consuming than the process of expansion and phase change from a liquid state to a gaseous depending on the actual temperature of the hot medium, cold medium and the first and second fluid mediums,

[0066] Fig. 4a shows the energy generating system 1 according to one embodiment, wherein the first 30a and second 30b energy transfer devices comprises a first 30a, 30a1 , 30a2 and second 30b, 30b1 , 30b2 fluid line

respectively, respectively connecting the second variable space 14b and fourth variable space 24b with a further piston system 2, whereby the fluid lines 30a1 , 30b1 , 30a2, 30b2 transfers the kinetic energy of the reciprocatable pistons 15, 25 via the further piston system 2, to the energy generating device 30.

[0067] Thus, according to one embodiment, again as seen in Fig. 4a, the energy generating system 1 comprises a further piston system 2. wherein the further piston system 2 comprises: a first cylinder 34 comprising a first reciprocatable piston 35, wherein the first piston 35 sealably divides the first cylinder 34 into a first 34a and second 34b variable space, wherein the first space 34a comprises a fluid medium 340 and the second space 34b comprises a fluid medium 345, a first energy transfer device 30c connected to the first cylinder 34, a second cylinder 44 comprising a reciprocatable piston 45, wherein the second piston 45 sealably divides the second cylinder 44 into a third 44a and fourth 44b variable space, wherein the third space 44a comprises a fluid medium 440 and the fourth space 44b comprises a fluid medium 445, a second energy transfer device 30d

connected to the second cylinder 44, wherein the first 30a and second 30b energy transfer devices of the main piston system 1 ' comprises a first 30a, 30a1 , 30a2 and second 30b, 30b1 , 30b2 fluid line respectively, whereby the second variable space 14b of the main piston system 1 ' is connected to the first variable space 34a of the further piston system 2 via the first fluid line 30a, 30a1 , and further connected to the third variable space 44a of the further piston system 2 via the first fluid line 30a, 30a2, whereby the fourth variable space 24b of the main piston system 1 ' is connected to the first variable space 34a of the further piston system 2 via the second fluid line 30b, 30b1 , and further connected to the third variable space 44a of the further piston system 2 via a second fluid line 30b, 30b2, whereby the fluid lines 30a1 , 30b1 , 30a2, 30b2 transfers the kinetic energy of the reciprocatab!e pistons 15, 25 via the further piston system 2, to the energy generating device 30,

[0068] According to one embodiment, the second and fourth variable spaces 14b, 24b of the main piston system 1 ', via the fluid lines 30a1 , 30b1 are in fluid connection with a first cylinder 34 of the further piston system 2 via a valve device 33 comprising a respective valve 33a1 , 33b1 for the respective fluid line 30a1 and 30b1 , and wherein the second and fourth variable spaces 14b, 24 of the main piston system 1 ', via the fluid lines 30a2, 30b2 are in fluid connection with a second cylinder 44 of the further piston system 2 via a valve device 43 comprising a respective valve 43a1 , 43b1 for the respective fluid line 30a2, and 30b2.

According to one embodiment, the valve devices 33 and 43 are controlled by a valve control unit 50.

[0069] According to one embodiment, the fluid medium 340 of the first space 34a and the fluid medium 440 of the second space 44a is an incompressible liquid. According to one embodiment, the liquid is oil. According to one embodiment, the fluid medium 340 of the first space 34a and the fluid medium 440 of the second space 44a is the same fluid medium 145 of the second space 14b and the fluid medium 245 of the fourth space 24b.

[0070] According to one embodiment, the fluid medium 345 of the second space 34b and the fluid medium 445 of the fourth space 44b is an incompressible liquid. According to one embodiment, the liquid is oil. According to one embodiment, the fluid mediums 345, 445 is a gaseous medium, wherein the gaseous medium is nitrogen.

[0071 ] According to one embodiment, the first cylinder 34 of the further piston system 2 comprises a reciprocatable piston 35, sealably dividing the cylinder 34 into a first 34a and second 34b variable space, wherein the first space 34a comprises a fluid medium 340, and the second space 34b comprises a gaseous medium 345, wherein the second cylinder 44 of the further piston system 2 comprises a reciprocatable piston 45, sealably dividing the second cylinder 44 into a third 44a and fourth 44b variable space, wherein the third space 44a comprises a fluid medium 440, and the fourth space 44b comprises a gaseous medium 445, wherein the second space 34b is in fluid connection with the fourth space 44b, wherein the second 14b and fourth 24b variable spaces of the main piston system 1 ', via the fluid lines 30a1 , 30a2, 30b1 , 30b2, are in fluid connection with the first 34a and third 44a variable spaces of the further piston system 2. According to one embodiment, during the expansion movement of the first piston 15 the fluid medium 145, 245 is forced out of the second space 14b as well as into the fourth space 24b aiding the compression movement of the second piston 25, and whereby during the expansion movement of the second piston 25 the fluid medium 145, 245 is forced out of the fourth space 24b as well as into the second space 14b aiding the compression movement of the first piston 25.

[0072] Fig. 4b discloses the energy generating system 1 , according to one embodiment, wherein the energy generating system 1 similar to the embodiment of Fig. 4a comprises a main piston system 1 ' and a further piston system 2.

However, in the embodiment of Fig. 4b, the second space 34b is not in a direct fluid connection with the fourth space 44b. Instead, the first 30a and second energy transfer devices 30b , comprises respectively further first and second fluid lines 30a3, 30a4 and 30b3, 30b4 The second variable space 14b of the main piston system 1 ' is connected to the second variable space 34b of the further piston system 2 via the first fluid line 30a3„ and further connected to the fourth variable space 44b of the further piston system 2 via a the first fluid line 30a4.The fourth variable space 24b of the main piston system 1 ' is connected to the second variable space 34b of the further piston system 2 via the second fluid line 30b3, and further connected to the fourth variable space 44b of the further piston system 2 via second fluid line 30b4.The fluid lines 30a3, 30b3, 30a4, 30b4 hereby transfers the kinetic energy of the reciprocatable pistons 15, 25 via the further piston system 2, to the energy generating device 30. Thus, according to one embodiment, the second variable space 34b and the fourth variable space 44b comprise the same fluid medium as in the first and third variable spaces 34a, 44a respectively. According to one embodiment, respective valve devices 53 and 63 are comprising valves 53a1 , 53b1 and 63a1 , 63b1 respectively connects the fluid lines 30a3, 30b3 and 30a4, 30b4 to the second variable space 34b and 44b as similarly described for the valve devices 33 and 43 above. According to one embodiment, the valve control unit 50 is adapted to control the valve devices 53, 63 such as e.g. the opening and closing of the valve devices. According to one embodiment, the first and second energy transfer devices 30a, 30b transfer kinetic energy from the reciprocating movement of the reciprocatable pistons 15, 25 to an energy generating device 30 arranged for being in an energy-transfer connection to the first and second reciprocatable pistons 15, 25.

[0073] Thus, the relationship and dependency between the expansion movement of the first piston 15 and the compression movement of the second piston 25 respectively the expansion movement of the second piston 25 and the compression movement of the first piston 25 has been shown in the embodiments related to Fig. 1 -3, as well as Fig. 4a, 4b and later Fig. 5. Again, in Fig. 1 -3 according to one embodiment, this is provided by the aid of a fluid connection directly between the second space 14b, and the fourth space 14b of the main piston system 1 '. Again, in Fig. 4a, and later Fig. 5, according to one embodiment this is provided by the aid of the second space 34b being in fluid connection with the fourth space 44b, i.e. in an indirect manner via these spaces of the further piston system 2. In Fig. 4b this is provided by that the second and fourth space 14b and 24b of the main piston system 1 ' are respectively connected to all spaces 34a, 34b, 44a, 44b of the further piston system 2.

[0074] According to one embodiment, an expansion tank 85 (not shown) is adapted to be in fluid connection with the second space 34b and the fourth space 44b. The function of the expansion tank 85 for the further piston system 2 is analogous to the function of the expansion tank 75 for the main piston system 1 ' described above. According to one embodiment, a valve 86 is provided in the fluid connection between the second space 34b and the fourth space 44b. According to one embodiment, the valve control unit 50 is adapted to control the opening and closing of the valve 86. According to one embodiment, the function of the valve 86 for the further piston system 2 is analogous to the function of the valve 76 for the main piston system 1 ' described above. According to one embodiment, a first valve 86a and a second valve 88b are provided and arranged In the fluid connection between the second space 34b and the fourth space 44b, for instance as described in a similar manner in the energy generating systems of Fig. 2 and 3. According to one embodiment, a valve control unit 50 is adapted to control the opening and closing of the valve 86a and 86b. According to one embodiment, the first valve 86a and second valve 86b are arranged on a either side of a expansion tank 85, i.e. wherein the first valve 86a controls the flow of the fluid medium from the second space 34b into the expansion tank 85 during expansion movement of the first piston 35 and the second valve 86b controls the flow of the fluid medium from the fourth space 44b into the expansion tank 85 during expansion movement of the second piston 45. According to one embodiment, the function of the first and second valves 86a and 86b respectively for the further piston system 2 is analogous to the function of the first and second valves 76a and 76b for the main piston system 1 ' described above.

[0075] According to one embodiment, the first cylinder 14 and the second cylinder 24 of the main piston system 1 ' are selected to have a larger volume than the first cylinder 3 and the second cylinder 44 of the further piston system 2.

According to one embodiment, the expansion and compression movement cycle time of the further piston system 2, i.e. time required for both the first piston 35 and second piston 45 to respectively cany out an expansion and compression movement, is shorter than the expansion and compression movement cycle time of the corresponding first piston 15 and second piston 25 of the main piston system 1 '. Thus, as a result, the frequency of the further piston system 2 is higher than the frequency of the main piston system 1 .

[0076] According to one embodiment, the second and fourth spaces 14b, 24b of the main piston system 1 ' are in fluid connection with a plurality of further pistons systems 2, 2', comprising at least a first and second further piston system 2, 2' in a similar arrangement as described above (not shown).

[0077] According to one embodiment, a movement cycle of the reciprocation of the pistons of the further piston system 2 is time shifted in relation to the cycle time of at least one of the plurality of further piston systems 2', According to one embodiment, the time shifted movement cycle between further pistons systems 2, 2' is achieved by means of controlling of the valve devices 33, 43 by the control unit 50,

[0078] According to one embodiment, an energy generating system 1 is provided , wherein the energy generating system 1 comprises a second main piston system 1 " similar to the first piston system 1 ' as described above, wherein the second main piston system 1 " is arranged to the further piston system 2, in a similar manner as the first main piston system 1 ' is arranged to the first further piston system 2 as described above, whereby the first and second energy transfer devices 30a", 30b" of the second main piston system 1 " transfer the kinetic energy from the reciprocating movement of the reciprocatable pistons 15", 25" to the energy generating device 30 arranged for being in an energy-transfer connection to the first and second reciprocatable pistons 15", 25".

[0079] According to one embodiment, a movement cycle of the reciprocation of the pistons of the second main piston system 1 " is time shifted in relation to the movement cycle of the pistons of the first main piston system V.

[0080] Fig. 5a discloses the energy generating system 1 , according to one embodiment, wherein the energy generating system 1 comprises a second main piston system 1 " similar to the first main piston system 1 ' as described above, wherein the second main piston system 1 " is arranged to the second further piston systems 2', in a similar manner as the first main piston system V is arranged to the first further piston system 2 as described above, wherein a movement cycle of the reciprocation of the pistons of the second main piston system 1 " is time shifted in relation to the movement cycle of the pistons of the first main piston system V,

[0081 ] According to one embodiment as described in Fig. 5a, the first 30a and second 30b energy transfer devices of the main piston system 1 ' further comprises a first 30a, 30a , 30a2, and second 30b, 30b1 , 30b2, fluid line respectively, whereby the second variable space 14b of the main piston system V is further connected to the first variable space 54a of the second further piston system 2 via the first fluid line 30a, 30a1 , and further connected to the third variable space 64a of the second further piston system 2' via a the first fluid line 30a, 30a2, whereby the fourth variable space 24b of the main piston system V is connected to the first variable space 54a of the first further piston system 2 via the second fluid line 30b, 30b1 , and further connected to the third variable space 64a of the second further piston system 2' via a second fluid line 30b, 30b2, whereby the fluid lines 30a 1 , 30b1 , 30a2, 30b2 transfers the kinetic energy of the reciprocatable pistons 15, 25 via the second further piston system 2', to the energy generating device 30.

According to one embodiment, the valve devices 33 and 43 of the second main piston system 1 " comprises additional valves 33a1 , 33b1 and 43a1 , 43b1 respectively for connecting the respective fluid lines 30a1 , 30b1 and 30a2, 30b2 to the first variable space 54a and third variable space 64a, Additionally, an analogous set up can be provided between the second main piston system 1 " and the first further pistons system 2 as described.

[0082] Fig. 5b discloses the energy generating system 1 , according to one embodiment, wherein the energy generating system 1 comprises a first main piston system 1 ' according to any of the described main piston systems 1 ', and a second main piston system 1 " similar to the first main piston system 1 ', wherein the second main piston system 1 " is arranged to a second further piston system 2', in a similar manner as the first main piston system 1 ' is arranged to the first further piston system 2. The overall structure is thus similar to what is described in Fig. 5a, however, the plurality of further piston systems 2, 2' comprises or essentially comprises the features of the further pistons system 2 as described in Fig, 4b above. The energy generating system 1 further comprises a high pressure line HP and a low pressure line LP, wherein the high pressure line HP connects the first energy transfer device 30a comprising the first 30a, 30a1 , 30a2, 30a3, 30a4 fluid lines as described in Fig. 4b to the second variable space 14b via a valve 73a1 of valve device 73, and to the fourth variable space 24b via a valve 73b1 of the valve device 73, and the low pressure line LP connects the second energy transfer device 30b comprising the second 30b, 30b1 , 30b2, 30b3, 30b4 fluid lines as described in Fig. 4b, to the second variable space 24b via a valve 83a1 of a valve device 83, and to the fourth variable space 24b via a valve 83b1 of the valve device 83. Thus, the pistons 34, 44 and 54, 64 of the further piston systems 2, 2' respectively have two valves in both ends wherein on each end, one valve is connected to the high pressure line HP and the other valve is connected to the low pressure line LP, and the variable spaces 14b, 24b of the main piston systems 1 ', 1 " each have two valves, wherein one valve is connected to the high pressure line HP and the other valve is connected to the low pressure line LP, According to one embodiment, the high pressure line HP and low pressure line LP and all fluid lines comprise a common fluid medium. According to one embodiment, the fluid medium is hydraulic oil. According to one embodiment, an expansion tank 95, similar to the expansion tanks 75, 85 described above, is arranged in connection to the low pressure line LP as seen in Fig. 5b. According to one embodiment, a respective cooling circuit 90a, 90b as described in Fig. 3e is provided to cool the first 14 and second cylinder 24 respectively in a manner further described in relation to Fig. 3e. According to one embodiment, a first 141 and second check valve 241 as described in relation to Fig. 3a-3d are provided in the first 14 and second 24 cylinders respectively. According to the embodiment, shown in Fig. 5b, the energy generating system 1 comprises four main piston system cylinders and four further piston system cylinders, however the use of a common high pressure line HP and low pressure line LP enables the connection and addition of any suitable number of main piston system cylinders and further piston system cylinders to the energy generating system 1 . According to one embodiment, a possible process of the energy generating system 1 may be described as follows: In the cylinders of the main piston systems V, 1 ", e.g. the first cylinder 14, wherein the first fluid medium 140 is heated by the aid of the first heat exchanging system 1 1 , wherein the first fluid medium 140 carry out an expansion movement after sufficient heating of the first fluid medium 140, wherein the fluid medium in the second space 14b is pressed through an open valve 73a1 to the high pressure line HP. This may be carried out with the check valves swung to a folded position. In the cylinders of the main piston systems 1 ', 1 ", e.g. the second cylinder 24, wherein the second fluid medium 240 is cooled by the aid of the second heat exchanging system 21 as well as the cooling circuit 90b, the pressure of the second fluid medium 240 is reduced. A valve 83b1 is opened whereby fluid medium from the low pressure line LP is allowed to enter the fourth space 24b whereby pressure is increased on the second piston 25, whereby the pressure of the second fluid medium 240 is increased to a higher pressure than if it only been exposed to cooling which enables the phase change into a liquid phase whereby the volume of the second fluid medium is reduced further enabling the second piston to reach its lowest most compressed position. The check valve 241 in an unfolded state further accelerates the cooling of the second fluid medium 240, which increases the speed of the process. When any of the cylinders of the main piston systems 1 ', 1 " reaches an end position, the valves 73, 83 at the upper end are closed and the heat exchanging process shifts from heating to cooling or the opposite. When the heat exchanging process is finalized, and the fluid medium 140, 240 has reached the similar temperature as the heat exchanging system, the correct valve 73, 83 is opened and the piston 15, 25 forces the fluid medium of the second or fourth space 14, 24 to the high pressure line HP if the fluid medium 140, 240 was heated or the piston 15, 25 is pressed downwards from the low pressure line LP if the fluid medium 140, 240 was cooled. In parallel to the above described process, the cylinders 34, 44 of the further piston systems 2, 2' works

independently of the cylinders of the main piston systems 1 ', 1 ". The cylinders 34, 44 of the further piston systems 2, 2' also work independently of each other.

When a piston 35, 45 of the respective cylinders 34, 44 has reached an end position, the valve in that end opens to the high pressure line HP and a valve in the opposite end of the cylinder 34, 44 opens to the low pressure line LP. The piston 35, 45 is then forced/pressed by fluid medium in the high pressure line HP and forces/presses fluid medium in the cylinder 34, 44 to the low pressure line LP, at the same as the kinetic energy of the piston 35, 45 is transferred to the energy generating device 30, for instance by rotating a drive shaft. The piston 35, 45 as well as the energy transfer device is adapted to rotate the drive shaft in the same direction irregardless if the piston 35, 45 carry out an expansion or a compression movement. The expansion 95 is adapted to take up the over pressure that may be generated when the cylinders of the main piston systems 1 ', 1 " that are being cooled are not able to receive all fluid medium from the low pressure line LP at the same time since the expansion movemement and compression movement of the pistons 15, 15 of the main piston systems 1 ', 1 " are not synchronous. According to one embodiment, the use of an expansion tank 95 enables the asynchronous movement of the pistons 15, 25. According to one embodiment, the use of a fluid medium in the second and fourth variable spaces 14b, 24, and thus in the high pressure line HP and low pressure line LP, which is compressible enables the asynchronous movement of the pistons 15, 25 even though the expansion tank 95 has been removed, i.e. is not comprised in the energy generating system 1 .

According one embodiment, the cylinders of the energy generating system 1 comprises limit switches adapted to sense when the piston 15, 25, 35, 45, has reached its end position. According to one embodiment, the first and second energy transfer devices 30a, 30b transfer kinetic energy from the reciprocating movement of the reciprocatabie pistons 15, 25 to an energy generating device 30 arranged for being in an energy-transfer connection to the first and second reciprocatabie pistons 15, 25.

[0083] Fig. 6 discloses the energy generating system 1 , according to one embodiment, wherein a preload cylinder 74, similar to the first cylinder 34 of the further piston system 2 as described above, is arranged in fluid connection with the second space 34b and the fourth variable space 44b of the first cylinder 34 and second cylinder 44 of the further piston system 2 for generating a preload to the fluid of the second space 34b and the fourth variable space 44b. According to one embodiment, the preload cylinder 74, is arranged in fluid connection with the second space 54b and the fourth variable space 64b of the first cylinder 54 and the second cylinder 64 of the second further piston system 2' for generating a preload to the fluid of the second space 34b and the fourth variable space 44b. According to one embodiment, a valve device (not shown) is arranged in the lines connecting the first and second cylinder 34, 44 and first and second cylinder 54, 64 respectively. According to one embodiment, the preload is a slight

overpressure compared to the pressure in the first and second variable spaces 14a, 24a. According to one embodiment, the overpressure is in the range of 1 -2 Bar. According to one embodiment, the preload cylinder 74 provides a similar effect as the above described expansion tanks, 75, 85, 95, i.e. wherein an asynchronous movement of the first 35 and second piston 45 are enabled. [0084]Fig. 7 discloses the energy generating system 1 , according to one embodiment of the invention. The main pistons 5, 6, 7, 8 compressing first and second fluid mediums such as e.g. gaseous medium causing a phase transfer of the gas by cooling or expanding gas by heating, which alternately is provided to heat exchanging systems arranged in fluid connection with each main piston 5, 6, 7, 8. The gaseous medium is housed in the lower part of the main pistons as well as in each heat exchanging system. Cooling and heating in liquid form is provided and returned from the heat exchanging systems via two 3-way valves arranged to each heat exchanging system. The upper part of each main piston and the fluid lines connected to the lower parts of the piston pairs 1 , 2, 3, 4 is filled with e.g. hydraulic oil. The main pistons work in pairs, wherein main piston 5 is heated and has a relatively higher pressure than main piston 7 having a low pressure, connected to fluid line 56 and 78 respectively. Piston pairs 1 -4 is connected in sequence via valves to fluid lines 56 and 78 so that at least one piston pair drives and rotates the drive shaft, or, transfers energy to the energy generating device by any other means. In Fig. 7, a fluid line is connected to the fluid line 56 and presses one piston in the piston pair to an upper end position, while the other piston of the piston pair is pressed back to a lower end position and hydraulic oil back via fluid line 78 to main piston 7, Pressurization line connected to the upper part in the piston pairs has a slight overpressure compared to the lowest pressure obtainable by heat exchanging by cooling in the main pistons. This overpressure allows in this case the transfer of gas into liquid phase in the heat exchanging system and the lower part of main piston 7 where the pressure as a result decreases rapidly.

Eventually, the main pistons 5 and 7 have reached their end positions. At this point, the valves V56 and V78 switch over to main piston 6 and 8 and the process starts over. While main piston 6 and 8 work toward their end positions, main piston 5 and 7 are undergoing a heat exchange wherein the piston previously heated is now cooled (5) and the piston previously cooled is now heated (7) so that they are ready to start when main piston 6 and 8 are ready. According to one embodiment, as seen in Fig. 7 a valve device V51 , V61 , V71 , V81 , is provided on the inlet side to each heat exchanging device, 1 1 , 21 etc, corresponding to the above described first valve 12, wherein a heat supply and cold supply is connected said valve devices. Fig. 7 also discloses a valve devices V52, V62, V72, V82 arranged on the outlet side of the heat exchanging devices. The valve devices V52, V62, V72, V82 are connected to a heat return and a cold return wherein the heat and cold may be reused in the process. According to one embodiment, the valve control unit 50 controls the valves V51 , V61 , V71 , V81 , V52, V62, V72, V82. In order to avoid that cold medium is returned via the heat return and hot medium is returned via the cold return, which reduces the efficiency of the process, the valve devices V52, V82, V72, V82 on the outlet side are adapted to be switched between the heat and cold return with a slight delay after the heat exchanging system has stopped either the heating and cooling process of the fluid medium in the cylinders. Hot and cold medium still in the heat exchanging system are thereby allowed to exit the system, emptying the same, before switching the valve devices V52, V62, V72, V82,

[0085] A preferred embodiment of an energy generating system 1 according to the invention has been described. However, the person skilled in the art realizes that this can be varied within the scope of the appended claims without departing from the inventive idea.

[0086] All the described alternative embodiments above or parts of an

embodiment can be freely combined without departing from the inventive idea as long as the combination is not contradictory.

Claims

1 , An energy generating system (1 ) comprising: a main piston system (1 '), further comprising, a first cylinder (14) comprising a first reciprocatable piston (15), wherein the first piston (15) sealably divides the first cylinder (14) into a first (14a) and second (14b) variable space, wherein the first space (14a) comprises a first fluid medium (140) and the second space (14b) comprises a fluid medium (145), a first energy transfer device 30a connected to the first cylinder (14), a first heat exchanging system (1 1 ) in fluid connection with the first space (14a), wherein the first heat exchanging system (1 1 ) is adapted to alternately heat and cool the first fluid medium (140), whereby pressure in the first space (14a) is increased and reduced respectively, a second cylinder (24) comprising a reciprocatable piston (25), wherein the second piston (25) sealably divides the second cylinder (24) into a third (24a) and fourth (24b) variable space, wherein the third space (24a) comprises a second fluid medium (240) and the fourth space 24b comprises a fluid medium (245), a second energy transfer device 30b connected to the second cylinder (24), a second heat exchanging system (21 ) in fluid connection with the third space (24a), wherein the second heat exchanging system (21 ) is adapted to alternately heat and cool the second fluid medium (240), whereby pressure in the third space (24a) is increased and reduced respectively, wherein the energy generating system (1 ) is adapted to control heating of the first fluid medium (140) and cooling of the second fluid medium (240) and conversely cooling of the first fluid medium (140) and heating of the second fluid medium (240), whereby the resulting pressure increase from heating and pressure reduction from cooling in the first space (14a) and the third space (24a)

respectively, causes the first piston (15) and the second piston (25) to reciprocate between an expansion movement during beating wherein the first and third variable spaces (14a, 24a) increases, and a compression movement during cooling wherein the first and third variable spaces (14a, 24a) decreases, whereby the first and second energy transfer devices (30a, 30b) transfer kinetic energy from the reciprocating movement of the reciprocatable pistons (15, 25) to an energy generating device (30) arranged for being in an energy-transfer connection to the first and second reciprocatable pistons ( 5, 25) whereby during the expansion movement of the first piston (15) the fluid medium (145, 245) is forced out of the second space (14b) as well as into the fourth space (24b) aiding the compression movement of the second piston (25), and whereby during the expansion movement of the second piston (25) the fluid medium (145, 245) is forced out of the fourth space (24b) as well as into the second space (14b) aiding the compression movement of the first piston (25),

2. An energy generating system (1 ) according to claim 1 , whereby the first (30a) and second (30b) energy transfer devices comprises a first (30a1 , 30b1 ) and second (30a2, 30b2) fluid line respectively, respectively connecting the second variable space (14b) and fourth variable space (24b) with a further piston system (2), whereby the fluid lines (30a1 , 30b1 , 30a2, 30b2) transfers the kinetic energy of the reciprocatable pistons (15, 25) via the further piston system (2), to the energy generating device (30),

3, The energy generating system (1 ) according to claim 2, wherein the second and fourth variable spaces (14b, 24b) of the main piston system (1 '), via the fluid lines (30a1 , 30b1 ) are in fluid connection with a first cylinder (34) of the further piston system (2) via a valve device (33), and wherein the second and fourth variable spaces (14b, 24) of the main piston system (1 '), via the fluid lines (30a2, 30b2) are in fluid connection with a second cylinder (44) of the further piston system (2) via a valve device (43), wherein the valve devices (33) and (43) are controlled by a valve control unit (50).

4. The energy generating system (1 ) according to claim 3, wherein the first cylinder (34) of the further piston system (2) comprises a reciprocatab!e piston (35), sealably dividing the cylinder (34) into a first (34a) and second (34b) variable space, wherein the first space (34a) comprises a fluid medium (340), and the second space (34b) comprises a fluid medium (345), wherein the second cylinder (44) of the further piston system (2) comprises a reciprocatable piston (45), sealably dividing the second cylinder (44) into a third (44a) and fourth (44b) variable space, wherein the third space (44a) comprises a fluid medium (440), and the fourth space (44b) comprises a fluid medium (445), wherein the second space (34b) is in fluid connection with the fourth space (44b), wherein the second (14b) and fourth (24b) variable spaces of the main piston system (1 '), via the fluid lines (30a1 , 30a2, 30b1 , 30b2), are in fluid connection with the first (34a) and third (44a) variable spaces of the further piston system (2).

5. The energy generating system (1 ) according to any of the preceding claims 2-4, wherein the second and fourth spaces (14b, 24b) of the main piston system (1 ') are in fluid connection with a plurality of further pistons systems (2, 2'), comprising at least a first and second further piston system (2, 2'), in a similar arrangement as described in claims 2-4.

6. The energy generating system (1 ) according to claim 5, wherein a movement cycle of the reciprocation of the pistons of the further piston system (2) is time shifted in relation to the cycle time of at least one of the plurality of further piston systems (2').

7. The energy generating system (1 ) according to any of the preceding claims, comprising a second main piston system (1 ") similar to the first piston system (1 ') according to any of the preceding claims 1 -14, wherein the second main piston system (1 ") is arranged to the further piston system (2) according to claims 2-4 whereby the first and second energy transfer devices (30a", 30b") of the second main piston system (1 ") transfer the kinetic energy from the reciprocating movement of the reciprocatable pistons (15", 25") to the energy generating device (30) arranged for being in an energy-transfer connection to the first and second reciprocatab!e pistons (15", 25"), wherein a movement cycle of the reciprocation of the pistons of the second main piston system (1 ") is time shifted in relation to the movement cycle of the pistons of the first main piston system (1 ').

8. The energy generating system (1 ) according to any of the preceding claims 2-7, comprising a second main piston system (1 ") similar to the first main piston system (1 ') according to any of the preceding claims 1 -7, wherein the second main piston system (1 ") is arranged to the second further piston system (2'), according to claims 5-7, wherein a movement cycle of the reciprocation of the pistons of the second main piston system (1 ") is time shifted in relation to the movement cycle of the pistons of the first main piston system (1 ').

9. The energy generating system (1 ) according to any of the preceding claims 1 -8, a preload cylinder (74), similar to the first cylinder (34) of the further piston system (2) as described in any of the preceding claims 3-8, is arranged in fluid connection with the second space (34b) and the fourth variable space (44b) of the first cylinder (34) of the further piston system (2) for generating a preload to the fluid of the second space (34b) and the fourth variable space (44b).

10. The energy generating system (1 ) according to claim 1 , wherein the first energy transfer device (30a) is connected to the first recsprocatable piston (15), and the second energy transfer device (30b) is connected to the second reciprocatable piston (25), wherein the second space (14b) is in fluid connection with the fourth space (24b), whereby during expansion movement of the first piston (15) the fluid medium is forced out of the second space (14b) into the fourth space aiding a compression movement of the second piston (25) so that the third space is decreased, and whereby during expansion movement of the second piston (25) the fluid medium is forced out of the fourth space (24b) into the second space (14b) aiding a compression movement of the first piston (25) so that the first space is decreased,

1 1 . The energy generating system (1 ) according to any of the preceding claims 1 -10, wherein the first heat exchanging system (1 1 ) comprises a first heat exchanger (1 1 a), comprising a first valve (12) to which a line (12a) for a hot medium and a line (12b) for cold medium is connected for selectively receiving a hot medium and a cold medium into the first heat exchanger (1 1 ), wherein the second heat exchanging system (21 ) comprises a second heat exchanger (21 a) comprising a second valve (22) to which a line (22a) for a hot medium and a line (22b) for a cold medium is connected for selectively receiving a hot medium and a cold medium into the second heat exchanger (21 ), wherein the first and second valves (12, 22) are controlled by a valve control unit (50).

12. The energy generating system (1 ) according to any of the preceding claims 1 -1 1 , wherein the first heat exchanger (1 1 ) is in fluid connection with the cylinder (14) via a third valve (13), and the second heat exchanger (21 ) is in fluid connection with the cylinder (24) via a fourth valve (23), wherein the opening and closing of valves (13, 23) are controllable by the valve control unit (50)

13. The energy generating system (1 ) according to any of the preceding claims 1 - 2, wherein the first heat exchanging system (1 1 ) and the second heat exchanging system (21 ) comprises two separate heat exchangers respectively, wherein a first heat exchanger of the first system (1 1 ) is adapted to heat the first (140) fluid medium, and a first heat exchanger of the second system (21 ) is adapted to heat the second (240) fluid medium, and a second heat exchanger of the first system (1 1 ) is adapted to cool the first medium (140), and a second heat exchanger of the second system (21 ) is adapted to cool the second (240) fluid medium.

14. The energy generating system (1 ) according to any of the preceding claims 1 -13, wherein the first heat exchanging system (1 1 ) is arranged within the first variable space (14a) of the cylinder (14), and/or the second heat exchanging system (21 ) is arranged within the third variable space (24b) of the cylinder (24).

15. The energy generating system (1 ) according to any of the preceding claims 1 -14, wherein the first heat exchanging system (1 1 ) is arranged externally of the cylinder (14), and/or the second heat exchanging system (21 ) is arranged externally of the cylinder (24).

16. The energy generating system (1 ) according to any of the preceding claims 1 -15, wherein the fluid medium (145) of the second space (14b) and the fluid medium (245) of the fourth space (24b) is an incompressible liquid,

17. The energy generating system (1 ) according to any of the preceding claims 1 -16, wherein the fluid medium (340, 540) of the first space (34a, 54a) and the fluid medium (440, 640) of the third space (44a, 64a) is an incompressible liquid.

18. The energy generating system (1 ) according to any of the preceding claims 1 -17, wherein the fluid medium (345, 545) of the second space (34b, 54b) and the fluid medium (445, 645) of the fourth space (44b, 64b) is an

incompressible liquid.

19. The energy generating system (1 ) according to any of the preceding claims 1 -18, wherein the liquid is oil.

20. The energy generating system (1 ) according to any of the preceding claims 1 -19, wherein the fluid medium (140, 240) is propane or R41 OA.

21 . The energy generating system (1 ) according to any of the previous claims, wherein the fluid medium (140, 240) undergoes a phase transfer from a gaseous phase into a liquid phase during the compression movement and back into a gaseous phase during the expansion movement,

22. The energy generating system (1 ) according to any of the preceding claims 1 -21 , wherein the fluid medium (345, 445) is a gaseous medium, e.g. nitrogen.

23. The energy generating system (1 ) according to any of the preceding claims 1 -22, wherein the fluid medium (145, 245) comprises a gaseous medium.

24. The energy generating system (1 ) according to any of the preceding claims 1 -23, wherein the hot medium is hot water and the cold medium is cold water.

25. The energy generating system (1 ) according to any of the preceding claims 1 -24, wherein the energy transfer devices (30a, 30b, 30c, 30d) comprises one of a mechanical transfer device such as a crank-link mechanism, magnets or coils.

26. The energy generating system (1 ) according to any of the preceding claims 1 -25, wherein the energy generating device (30) comprises one of a rotating shaft in a crank-link mechanism, magnets, coils, and a generator.

27. The energy generating system (1 ) according to any of the preceding claims 1 -26, wherein the energy generating system (1 ) is adapted to control heating of the first fluid medium (140) substantially simultaneously with cooling of the second fluid medium (240) and conversely cooling of the first fluid medium (140) substantially simultaneously heating of the second fluid medium (240),