FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a device and a method for trans¬ forming a gas pressure into mechanical energy into electrical energy.

Electrical generators transform mechanical energy into electrical energy. Steam boilers may be used for producing water steam having a high pressure with an energy then transformed in a tur¬ bine into mechanical work. The water steam with a high pressure is produced by heating water to boil. The heating takes place in most types of steam boilers by combustion of oil, gas or solid fuels in the furnace of the steam boiler. These energy sources used for heating purposes have a negative influence upon our environment and the costs and accordingly the price for electrical energy get continuously higher for the consumers. Furthermore, use of these energy sources is associated with great losses through the flue gases, which we have today no real possibility to utilize.

Many of the systems for providing electricity of today are based on generation of electrical energy where the energy source or the plant is localized and then transport of the energy to the con¬ sumers through long and costly conducting networks, which are also sensitive to disturbances of different types.

GB 2344645 describes a system for generating electricity, in which solar energy is used for evaporating a liquid having a low boiling point, which vapour is accordingly used for driving an electrical generator through a turbine. However, there is a need of developing the electrical generators of today so as to be able to utilize such environmentally friendly energy sources for pro¬ ducing electrical energy to a lower cost than the systems of to¬ day for generating electricity.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a more efficient device than those already known for transforming a gas pressure into mechanical energy into electrical energy.

This object is obtained by providing a device having the features of the characterizing part of the appended claim 1. The device according to the invention comprises a device for transforming a gas pressure into mechanical energy into electrical energy com¬ prising a stationary body having at least one cylinder with a wor¬ king piston arranged on an axle being mounted movably in the longitudinal direction thereof within the stationary body. The de¬ vice comprises means for alternatively conducting a pressurized gas into said at least one cylinder and means for alternatively conducting gas out from the cylinder for driving the working piston to and fro in the longitudinal direction of said axle within the stationary body. The device also comprises members adapt¬ ed to slow down the axle while storing energy, which contributes to acceleration of the axle in the opposite direction when chang¬ ing the direction of movement thereof.

According to an embodiment of the invention said members com¬ prise at least one damping recess arranged in the stationary body and said axle is provided with at least one damping piston moving in said at least, one damping recess arranged so that upon compression of the gas/air volume enclosed in said at least one damping recess the movement of the axle will be slowed down. According to another embodiment said members comprise resilient means, such as a spring, for resetting said at least one working piston after having been moved by the influence of the pressured gas upon the working piston. Thus, the kinetical en- ergy of the axle in one direction is utilized for then accelerating the axle in the other direction. Accordingly, a short laps© be¬ tween the leading in and the leading out of the pressurized g as is achieved. Such a device is more efficient than the known dis- placement motors normally requiring great gas flows, which re¬ sults in a low total efficiency thereof.

According to a still further embodiment of the invention the de¬ vice comprises a stationary body having at least two cylin ders facing each other with a working piston each, the two working pistons being arranged on an axle in common, which is mou nted movably in the longitudinal direction thereof within the stationary body. The device also comprises means for alternatively con¬ ducting a pressurized gas into the cylinders and means for alter- natively conducting gas out from the cylinders, said means being adapted to conduct gas into one of the cylinders while gas is led out from the other cylinder for driving the working pistons to an fro in the longitudinal direction of said axle within the stationary body. The stationary body has at least two damping rece sses filled with gas and the axle in common is provided with at least two damping pistons moving in a damping recess each, so that upon compression of the gas/air volume enclosed in the damping recess the movement of the axle in common will be slowed down.

According to a preferred embodiment of the invention a mag netic core is mounted on the axle and the magnetic core is adapted to move inside a stator, so that the movements of the magnetic core generate energy in the stator winding. In case two workin g pi¬ stons are arranged on an axle in common the pressure difference occurring between the working pistons generates a force being the product of the pressure difference and the working p>iston area. The working pistons and the associated magnetic core will then move rapidly in the direction towards the lower pres sure. The axial movements of the magnetic core then generate el ectri- cal energy in the stator winding as in conventional generators. Thus, the device according to the invention may replace ge nera¬ tors in existing steam plants. According to another embodiment of the invention the axle is adapted to act upon a gear rack driving an output axle through gear wheels instead of mounting a magnetic core on the axle of the device.

According to another embodiment of the invention the movement of the magnetic core in at least one direction is generated by an arrangement having piston and cylinder designed according to the principle of a two-stroke combustion engine with associated fuelling system.

According to a further embodiment of the invention the leading-in means to the cylinder/cylinders comprises a change-over valve carrying out a rotation between two change-over positions and being arranged to not reduce the gas flow into the cylinder/ cylinders and accordingly not give rise to flow losses for example by the fact that the change-over valve has a valve body having a cylindrical space and a valve cradle with a concave surface mounted in the centre of the space. The concave surface is re¬ stricted in the longitudinal direction by circular walls provided with suitable sealings for sealing against the cylindrical working space of the valve in the valve body. The change over between inlet and outlet to the cylinder/cylinders of the change-over val- ves is preadjusted or adjusted during operation with respect to the turning positions of the working piston/working pistons.

According to an embodiment of the invention the pressurized gas is water steam or it is generated from a liquid, for example a Ii- quid having a boiling point lower than O0C, such as R410A, car¬ bon dioxide, propane, R134a, ammonia and others, or a mixture thereof. Use of such a liquid means a possibility to obtain a con¬ siderable steam pressure also at low temperatures.

According to another embodiment of the invention the leading-in means comprises a thermal-insulated container adapted to equa- lize possible pressure variations in the pressurized gas before leading it into the cylinder/cylinders.

The present invention also relates to a method for transforming mechanical energy into electrical energy, comprising the steps of generating a gas with a high pressure by heating a liquid to boil¬ ing and evaporating. The pressurized gas is led through a device comprising a stationary body having a cylinder with a working piston arranged on an axle being movable in the longitudinal di- rection thereof inside the stationary body and transforms the pressure of the gas on the surface of the working piston into me¬ chanical work which by the movement of the magnetic core re¬ sults in electrical energy. A pressurized gas is alternatively con¬ ducted into the cylinder and alternatively from the cylinder so as to drive the working piston to and fro in the longitudinal direction of said axle. The movement of the axle is slowed down while stor¬ ing energy, which contributes to acceleration of the axle in the opposite direction when changing the moving direction thereof.

According to an embodiment of the invention the axle is slowed down by means of a member comprising at least one damping recess arranged in the stationary body. The axle is provided with at least one damping piston moving in the damping recess so that upon compression of the gas/air volume enclosed in a damp- ing recess the movement of the axle will be slowed down. Accor¬ ding to another embodiment of the invention the axle is slowed down by means of a member comprising resilient means, such as a spring, for resetting the working piston after having been mov¬ ed by the pressurized gas.

According to an embodiment of the invention a magnetic core is mounted on the axle and adapted to move inside a stator, so that the movements of the magnetic core generates energy in the sta¬ tor winding. The axle may as an alternative act upon a gear rack driving an output rotating axle through gear wheels and back stop bearings instead of mounting a magnetic core on the axle. According to another embodiment of the invention a change-over valve is arranged, which carries out rotation between two change-over positions at the inlet to the cylinders, said change¬ over valve being arranged to not reduce the gas flow into the cylinder for example by the fact that the change-over cylinder comprises a valve body having a cylindrical space and a valve cradle with a concave surface mounted in the centre of the spa¬ ce. As an alternative the leading-in means comprises a cylinder from two-stroke combustion engine.

According to an embodiment of the invention the pressurized gas is water steam from another energy process or air having an over-pressure or it is generated from a liquid having a boiling point lower than O0C, such as R410A, carbon dioxide, propane, RI 34a, ammonia and others, or a mixture thereof.

According to another embodiment of the invention the pressur¬ ized gas is condensed into liquid after having passed through the transformer. When the pressurized gas passes through the transformer this takes place while delivering work through ex¬ pansion in the transformer, so that a great lowering of the tempe¬ rature and volume takes place in the gas. The expansion brings the gas into vapour phase, whereas the condensing into the liquid phase may take place in the following condenser. Accor- ding to a further embodiment of the invention the heat removed from the condensing gas is used for heating a liquid, such as water, or a gas, such as air. Thus, an apartment of a consumer may for example be provided with hot water or hot air.

According to an embodiment of the invention the pressurized gas is generated by heating a liquid having a boiling point lower than 00C. This means that the gas gets the same pressure and flow at much lower temperatures than needed for conventional steam boilers using water as the working liquid. Said liquid is selected depending upon among others the expansion coefficient, the vi¬ scosity and the boiling point thereof. The electricity generating system requires for example in cold climates liquids having a lower boiling point than required in warmer climates.

According to an embodiment of the invention the liquid having a boiling point lower than 00C is heated by solar energy, air heat, waste heat, excess heat, water heat, ground heat, geo heat, or any other heat carrying medium suited for the purpose or a com¬ bination of said heat carrying media. The heat is absorbed from these environmentally friendly energy sources through a conven- tional heat exchanger or fan evaporator or directly in a tube loop suitable for the task or any other suitable device containing the liquid with a low boiling point. When heating said liquid it is brought to boil in the heat exchanger or the evaporator or the tube loop, in which the liquid passes to the vapour gas phase, which results in an increase of the pressure in the system to a value corresponding to the vapour pressure of the gas at the end temperature obtained in connection with the passage through said heat exchanger or evaporator or tube loop.

According to another embodiment of the invention the heat car¬ rying medium is used as a cooled medium or so as to cool an ob¬ ject after having transferred the heat thereof to said liquid. Thus, a consumer may for example be provided with cooled water or cooled air.

According to a further embodiment of the invention the pressur¬ ized gas is led to a thermal-insulated container for equalizing possible pressure variations before conducting it to said device transforming mechanical energy into electrical energy.

According to an embodiment of the invention the electrical en¬ ergy produced is stored for example in an accumulator.

The device and the method according to the invention are suit- able for generating electrical energy and it may also as a by¬ product deliver hot water, hot gas or a cooled medium to areas having an excess of solar energy, with much air heat, waste heat, water heat, ground heat or any other heat carrying medium suitable for the task or a combination of said heat carrying media. The invention is applicable to stationary as well as movable and mobile electricity generating systems, such as in electrical or hybrid cars. The invention is especially but not exclusively suitable for transforming a gas pressure into mechanical energy directly into electrical energy, i.e. without any need of a gear box, so that accordingly shifting losses may be avoided.

Further advantages as well as advantageous features of the in¬ vention appear from the following description and the other de¬ pendent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a de¬ scription of preferred embodiments of the invention cited as examples.

In the drawings:

Fig. 1 shows a schematic view of a system for carrying out the method according to an embodiment of the inven- tion, and

Fig. 2 shows a device for transforming mechanical energy in¬ to electrical energy according to an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Fig. 1 illustrates an example of an electricity generating system comprising a pressure-tight liquid container 1 , containing a liquid 2 with a low boiling point connected to a pump module 4 of a gas pressure driven pump 3, which pump for example may be a con- ventional membrane or piston pump driven by pressure. The li¬ quid is for example R-410A having a boiling point of -51.53°C at 1 atm.

The liquid 2 is pumped to the secondary side of a heat exchanger 5, whereas a sun catcher is for example connected to the primary side of the heat exchanger 5. The liquid is brought through the water heated by sun radiation from the sun catcher to boil vio¬ lently resulting in a transition into vapour or gas form on its way through the heat exchanger 5. The required heat energy may also be absorbed from the atmospheric air by using an air heat exchanging evaporator. An electrically driven fan takes care of the flow of air through the air heat exchanging evaporator. The hot air passing delivers heat to the liquid/gas flowing in the eva- porator, so that cooled air may after the evaporator be taken care of for cooling dwellings or premises or for other purposes where coldness is desired. Heat generating electrical or electronical components may as an alternative be used for heating said liquid/gas.

The vapour or gas formed in the heat exchanger flows further with a pressure being a function of the temperature given to the vapour or the gas when passing through the heat exchanger 5. The R-410-gas/liquid mixture has for example at the outlet of the heat exchanger have a final temperature of +100C and a pres¬ sure of 10.8 bars.

The vapour/gas flow is distributed among the drive module 6 of the feeding pump 3 and a pressure tank 7 belonging to a trans- former or converter 8.

The vapour/gas flows from the pressure tank 7 through conduits 8a and 8b into change-over valves 9a and 9b and further to the cylinders of the transformer, where the gas pressurized by heat- ing carries out a work. If the valve cradle of the change-over valve 9a is set in the position for opening into the cylinder 10, then the valve cradle of the change-over valve 9b is automatically set in the closed position, so that vapour/gas does not pass into the cylinder 11 , but it is opened for evacuating vapour/gas from said cylinder 11 into the low pressure prevailing in the collecting tank 13, through conduits 14a and 14b, where a certain degree of condensing takes place. The vapour/gas partially condensed flows further to a condenser 15, in which the remaining heat en¬ ergy in the vapour/gas is removed through a method suitable for the task, for example an evaporator of a cooling machine con¬ nected to the secondary side of the condenser 15 and where ac- cordingly a final condensing into liquid takes place. Systems for cooling suitable for the purpose may as an alternative be con¬ nected, such as for example natural or chemical, or heat divert¬ ing electrical or electronical components or through expansion of pressurized gas in liquid phase from the pump 4 for leading into the heat exchanger 5 may be used for cooling said liquid/ gas. The condensed liquid flows after that further to the liquid con¬ tainer 1 . The heat from the cooling machine may be taken care of for production of hot water or as preheating of heat media to the heat energy absorbing unit (the heat exchanger 5) of the system.

According to an embodiment of the invention heat energy to the system is absorbed on daytime when the temperature of the sun/ atmospheric air is high, through sun catchers or through an air heat exchanging evaporator. The consumption of electrical ener- gy in households is relatively low during daytime but high in the evening. For meeting the energy demand during the part of the day when the consumption is highest heat energy may be stored in an insulated accumulator tank, from which heat needed by the system for being able to generate electrical energy continuously during the entire day may then be taken during the dark hours of the day.

The method may also be such that during daytime maximum power is withdrawn from the system and the electrical energy not consumed directly is connected to at least one electricity cartrid¬ ge heating the water in the accumulator tank. When the tempera¬ ture of the gas from the evaporator 5 falls below a set value, which is detected by a thermostat, a switching of the directing valves arranged before and after the evaporator takes place, so that the liquid/gas flows through the tube loop in the heated ac¬ cumulator tank. The hot water in the accumulator tank delivers heat to the liquid/gas in the tube loop of the accumulator tank, in which a required vapour pressure may be maintained for the con¬ tinuing generation of electricity.

Fig. 2 shows a device for directly transforming mechanical ener- gy into electrical energy according to an embodiment of the in¬ vention. The d evice comprises a stationary body 16. Two pistons 17 and 18 are connected to each other by means of a piston rod 19 in common. An electrowinded or permanent magnetized circu¬ lar magnetic core 20 having alternating magnetic field s North/ South is mounted on the axle 19 in common between the pistons 17 and 18.

When the vapour/gas pressure acts upon the piston 17 this will move to the right together with the piston rod 19, the magnetic core 20 and the piston 18, towards the turning position for the piston 18, where the valve cradles 21 and 22 change the position and the vapour/gas pressure then acts upon the piston 18. The pistons 17 and 18 with the piston rod 19 and the magnetic core 20 change the direction of movement towards the left turning position for the piston 17. The compression of the air/gas volume between the clamping piston 29 and the damping recess 31 and the damping piston 30 and the damping recess 32, respectively, prevents the movable mass 17, 18, 19, 20 from hitting against the stationary body 16.

Electrical energy will during each such movement of the magnetic core 20 be generated in the circular stator winding 23 which may be of one or multiple phase type. Each movement in the direction to the right or to the left may constitute an entire period of the sine-shaped alternative current. Electrical energy generated is tapped through terminal block 24 and rectified to direct current through a rectifier (not shown). The direct current obtained is connected to a conventional DC/AC-converter, in which the con¬ nection thereof always delivers the correct period number of the alternating current inde pendently of the operation frequency of the transformer.

In the position of the valve cradles 21 and 22 for evacuating from the respective cylinder 17 and 18 a change towards the l ower pressure takes place very rapidly. A powerful expansion of the enclosed vapour/gas then takes place and results in a decrease of the temperature thereof. The expanded vapour/gas flows through conduits 14a and 14b to the collecting tank 1 3 and further to the condense r 15 where a complete condensing takes place.

Each valve 9a, 9b is constructed so that the gas flow on the high pressure side through the conduits 8a and 8b, at the passage through the change-ove r valve 9a and 9b, respectively, does not meet any area reduction on its way into the cylinders 10 and 11 , respectively. This is achieved by a special construction in the form of the arrangement of a turnable valve cradle 21 and 22 in the centre of a cylindrical space 25 and 26, which cradle may as¬ sume two change-over positions, where the valve cradle 21 is shown in the inlet position and the valve cradle 22 is shown in the evacuating position.

A preferably rectangular opening 27 and 28, the width of which may be the same as the diameter of the cylinder 10 and 1 1 , respectively, has an opening area being larger or equal to the flowing area for the con duits 8a and 8b and has a design towards the cylinder 10 and 11 resulting in the lowest possible flowing re¬ sistance. The valve cradle 21 and 22, respectively, has an axial length completely covering the rectangular opening 27 and 28, respectively. Both valve cradles 21 and 22 change between an inlet position and an evacuating position at the same time through a mechanical forced control (not shown) at each end position for the respective piston 17 and 18. The magnetic core 20 is at each wall provided with a short cylin¬ drical damping piston 29 and 30 provided with a lip seaimg (not shown) each. A cylindrical space, i.e. recesses 31 and 32, suit¬ able for the damping pistons 29 and 30 is arranged in the statio- nary body 16 of the transformer. When the magnetic core 20 with associated damping pistons and 30 with high speed is moved from the left to the right in Fig. 2 an air volume will be enclosed in the damping recess 32. In connection with the presence of a damping piston 30 in the immediate proximity to the cylindrical space 32 the changing of the position for the valve cradle 21 and 22 is initiated and is completely carried out when the piston 30 passes half the depth of the cylindrical space 32. The air volume enclosed in the damping recess 32 will by the kinetic energy of the magnetic core 20 be compressed further until the pressure and the force on the piston 30 are that high that the movement is slowed down completely snd the magnetic core 20 changes movement direction to the other direction.

Upon compression of the enclosed air volume the air will be heavily heated by the compression work from the kinetic energy of the magnetic core, which contributes to the acceleration of the magnetic core 20 when changing the movement direction. An analogous process takes p lace when the magnetic core 20 with associated pistons 17 and i δ reaches the left side of the station- ary body 16.

The entire assembly shown in Fig. 2 is preferably freely sus¬ pended so that vibrations caused by the movements of the axle are not transferred to the supporting layer.

The working piston diameter is for example 100 mm and the working piston area 78.5 cm2, so that the force on the piston at the gas pressure 10.8 bars amounts to about 847.8 kp. The speed of the piston is abou t 1.8 m/sec. at the frequency of 20 Hz, so that the piston carries o ut a mechanical power of about 1 526 kpm/sec. An opposing pressure of 4 bars prevails on the oppo¬ site piston, so that the real power which may be delivered by the magnetic core will be about 960.8 kpm/sec. Approximately 80-85% of the power of the magnetic core is delivered as electrical en¬ ergy as in conventional rotary generators.

The gas expands after the transformer towards a lower pressure. By the expansion the temperature of the R-410A-gas is lowered to about -15°C at the connection to the subsequent condenser 15. When the gas is condens ed in the condenser the temperature thereof is lowered by further A0C.

The invention is of course not in any way restricted to the pre¬ ferred embodiments described above, but many possibilities to modifications thereof would be apparent for a person with ordi¬ nary skill in the art without for that sake departing from the basic idea of the invention as defined in the appended claims. The de¬ vice according to the invention may for example comprise a plurality of axles, in which each has one or more working pistons.