WO2022086312A1

WO2022086312A1 - Converter for converting heat energy stored in ocean waters and in the atmosphere into electrical energy

Info

Publication number: WO2022086312A1
Application number: PCT/MA2021/000018
Authority: WO
Inventors: Ahmed BYAH
Original assignee: Byah Ahmed
Priority date: 2020-10-19
Filing date: 2021-10-11
Publication date: 2022-04-28
Also published as: MA51537A1; MA51537B1

Abstract

Disclosed is a converter for converting heat energy of solar origin stored in ocean waters and in the atmosphere into electrical energy. The converter proposed by this invention is based on a special organic thermodynamic cycle and a hydraulic loop. The cycle uses propane as the working fluid. As a result of the physical properties of the latter and, in particular, its low boiling point, it is able to absorb calories from the ambient environment and be transformed into vapour. Heat energy is thus transformed into pressure energy, which is communicated to the hydraulic loop, whose components include a pressure accumulator and a hydraulic turbine coupled to an electric generator. This invention also proposes a method for liquefying vapour, and also proposes a method for synchronising the operation of a set of reservoirs, by using a digital control/command system to achieve a stable and continuous operating state from a discontinuous operating state. The converter also has the property of producing cold. The installation of such a converter on board large ships is capable of producing the energy required for propulsion and all on-board services.

Description

Converter of heat energy of solar origin stored in the waters of the oceans and in the atmosphere into electrical energy.

Technical area.

This invention relates to a converter of heat energy of solar origin stored in the waters of the oceans and in the atmosphere into electrical energy.

Prior technique.

The major natural sensors of solar radiation are the oceans and the atmosphere. Everyone thinks that the alternative source of energy to atomic energy and the fossil energy of tomorrow will certainly be the energy stored in the waters of the oceans and in the atmosphere. For the exploitation of thermal energy from the seas (ETM), recent studies estimate that the technically exploitable potential (TEP) is 100,000 TWh/a, and it represents 82% of the energies of the sea. These large reservoirs natural sources of heat energy constitute an inexhaustible, renewable, ecological and clean stock. Attempts to harness this energy source to produce electricity have so far remained insignificant.

It is known from the state of the art closest to the converter proposed by this invention, devices having been the subject of a patent application, one can cite for example the patent EP2929184A1.

Most ocean thermal energy conversion systems (ETM), also known in English (OTEC) for "Ocean thermal energy conversion", use the temperature difference between the relatively warm surface water (temperature between 23 and 28°C), and cold deep water (depth beyond 1000 m, and temperature = 5°C) to operate a classic thermodynamic cycle such as the organic Rankine cycle (ORC), to drive a heat engine in sight to produce electrical energy. OTEC power generation was identified in the late 1970s as a possible renewable energy source with a low to zero carbon footprint of the energy produced. Conventional ETM systems bring huge amounts of deep cold sea water to the surface to provide cooling. More than half produced in an OTEC plant would be needed to run the water pumps and cool the working fluid and to power the plant's auxiliary needs. According to experts, the overall low net efficiency of an MTE plant is not a commercially viable power generation option.

Still in the state of the art of the closest technique, we can cite the reference W02007101919A1 of a patent which describes a typical model of attempts to convert heat energy contained in the ambient medium or rejected by another device or sought specifically and transported by a fluid, in an energy usable as mechanical energy and/or electrical energy.

The new generations of high-temperature heat pumps are electrical appliances, which use the energy available free of charge in the environment to provide heating and the production of domestic water for homes, the expected purpose of these machines is to take calories from one medium and return them to another, without ever thinking of producing electricity. Today, the thermal energy of the seas is attracting renewed interest and an international consensus seems to be established according to which it could contribute to satisfying our primary energy needs. But the unsuitability of our so-called traditional production methods remains an obstacle to accessibility to this energy.

The Rankine cycle (inorganic and organic) is based on the cooling of the expanded vapor to liquefy it, and all the latent heat is transferred to the natural environment which is colder than the expanded vapor. But, if the natural environment is the hot source, then you have to use the cold production system to liquefy the steam, and in this case you spend more energy than you produce.

Therefore, finding a new thermodynamic cycle other than the organic Rankine cycle, in order to be able to exploit the calorific energy stored in the seas, the oceans and the atmosphere is the only solution.

Summary of the Invention.

To remedy the drawbacks presented above, the present invention proposes a converter using a new special thermodynamic cycle used in parallel with a hydraulic loop; a new method of energy conversion; and a new method of liquefying working fluid vapor using staged isenthalpic expansion; a method of synchronizing the operation of a set of intermediate tanks. Said converter is better adapted to the exploitation of the calorific energy of solar origin stored in the waters of the oceans and in the atmosphere. The energy stored in the waters of the oceans and in the atmosphere is very abundant on our earth, and it is free, renewable, inexhaustible, clean energy and does not emit greenhouse gases. This invention will certainly have a positive impact on the environment and on the climate, and will have positive consequences on the political, economic and social levels. This converter has the particularity of being based on simple techniques within the reach of all countries in the world.

The first aim of this invention is to propose a converter characterized by its operation based on a special organic thermodynamic cycle used in parallel with a hydraulic loop. Said cycle transforms the very low temperature calorific energy stored in the water of the oceans and in the atmosphere into pressure energy; the latter will be communicated to the hydraulic loop within which the transformations continue to finally lead to the production of electricity.

Another object of this invention is to provide a method of partial liquefaction of the steam inside the condensation line located in the condenser of the steam liquefaction stage, based on a staged isenthalpic expansion. The condensation line is an adiabatic line made up of a series of phase separators alternated by pressure regulators.

Yet another objective of this invention is to provide a method for synchronizing the stages of the operating cycle of a group of intermediate reservoirs using a digital control-command system, to guarantee the continuity and stability of the flow of water supplying the hydraulic turbine coupled to an electric generator. Yet another object of this invention is to provide an organic working fluid which must be non-harmful to the ozone layer and non-generating greenhouse effect, and must be insoluble or very slightly soluble in water, it must also have a low boiling point, and a high saturation vapor pressure at room temperature. It must also have its high critical temperature without approaching the boiling point of water. This last property makes it possible to exploit other sources of heat (generally heat coming from, recuperation or other hot sources of various origins.) whose temperature is higher than the ambient temperature, propane responds well to these properties, and it is he who will be adopted as the working fluid, pending the finding of another substitute working fluid with better properties.

Said converter proposed by this invention can be modeled by a special thermodynamic cycle, used in parallel with a hydraulic loop.

The special thermodynamic cycle consists of a number of stages corresponding to the number of transformations that the working fluid must undergo during its evolution in said thermodynamic cycle. It includes a stage of steam generators; an energy conversion stage; a steam liquefaction stage; and a pumping stage for reintroducing condensate into the steam generator, and for reintroducing uncondensed steam by compression into the liquefaction stage for recycling.

The hydraulic loop is a confined hydraulic circuit, in which fresh water circulates in a closed circuit, the temperature of the water must be that of the environment, that is to say the temperature of the environment where the steam generator. Said hydraulic loop is made up of the group of intermediate reservoirs also belonging to the special thermodynamic cycle; a pressure accumulator; a hydraulic turbine; a water tank or tarp to receive the water as it leaves the turbine; and a hydraulic pump.

The steam generator stage must contain at least one steam generator. In general, the function of the steam generator is to allow the heat exchange between the heat source and the organic working fluid, which, under the action of the heat flux passing through the wall, is brought to a boil and is transformed into steam under a certain pressure which is specific for each working fluid. In the case of this invention, the heat source is the calorific energy of solar origin stored in the water of the oceans and in the atmosphere, or quite simply our natural atmosphere.

The energy conversion stage must contain at least one group of three intermediate reservoirs, said group also belongs to the hydraulic loop, because it is in the intermediate reservoir that the communication of the pressure energy of the steam to the hydraulic loop.

The special thermodynamic cycle does not use the expansion of vapor (isentropic expansion) as the driving phase to produce work as in the normal organic Rankine cycle (ORC), but, it is limited to the passage of the working fluid from the liquid state in the vapor state, and uses only the saturated vapor pressure to drive out the water contained in the intermediate tank to take its place; the water, forced to escape through the outlet orifice to the pressure accumulator, which is a component of the hydraulic loop. At this point, the vapor pressure energy is communicated to a hydraulic circuit, and all that remains is to partially liquefy the steam; by taking advantage of its pressure which it has retained, to cause it to undergo staged isenthalpic expansion in the condensation line (which is an adiabatic line) composed of a number of phase separators alternated by pressure regulators also called Joule-Thomson valves that operate on the Joule-Thomson principle, which is a physical phenomenon in which the temperature of a gas decreases when that gas undergoes adiabatic expansion.

Each intermediate tank of a group must be insulated, its shape must preferably be cylindrical with a domed bottom, and mounted in a vertical position. In addition, each tank must have on its upper part a steam inlet coming from the steam generator, and a steam outlet towards the liquefaction stage. On the lower part, the tank must have a water inlet from a hydraulic pump, and a water outlet in the direction of the pressure accumulator.

The pressure accumulator is a pressurized tank. It is filled half its volume with fresh water, and the other half is occupied by vapor from the working fluid, forming a vapor chamber which keeps it under pressure. It has a water inlet and outlet at the level of the part occupied by the water, and also has at the level of the steam chamber an inlet equipped with a pressure regulator, and an outlet equipped with a relief valve.

The pressure inside said pressure accumulator must necessarily be lower than the saturated steam pressure which prevails in the steam generator and in the intermediate tank which discharges the water towards it; and this pressure must be kept constant by a regulating system, for the purpose of compensating for irregularities in the incoming water flow caused by the opening and closing of the valves of the group of intermediate tanks, and to ensure a flow of water constant outgoing to the hydraulic turbine. It is thanks to the pressure regulator installed on the steam inlet pipe in said accumulator, and to the relief valve installed on the steam outlet pipe, that the stability of the pressure inside said accumulator is ensured: when the pressure tends to drop, the pressure regulator lets the steam pass inside the steam chamber to compensate for this drop, and when the pressure tends to increase, the relief valve lets the steam escape. escape outside the vapor chamber to the condensation line to compensate for this increase.

The flow of water from the intermediate tank to the pressure accumulator cannot take place if certain precautions are not taken, for this the pressure inside the said accumulator must be kept constant and lower than that which reigns in the intermediate tank; this pressure difference has a great influence on the flow rate of the water, and on the section of the pipe which connects the two reservoirs.

The hydraulic turbine is indispensable for transforming the water pressure energy into mechanical rotational energy of the turbine rotor coupled to the electric generator, and it needs a continuous and stable water flow; to guarantee such a flow, it is essential to ensure the continuity of a supply of water entering the pressure accumulator, and to guarantee a regular and stable flow leaving in the direction of the hydraulic turbine. The continuity of the inflow is ensured by the synchronization method described below, while the outflow it is ensured by the pressure accumulator itself, since it is equipped with a regulation system allowing it to play this role. The hydraulic pump is essential to evacuate the water from the tank and push it back to the group of intermediate tanks to drive out the expanded steam and force it to go to the condensation stage.

The vapor liquefaction stage consists of at least one condenser comprising at least one condensation line. Said condensation line is an adiabatic circuit in which staged isenthalpic expansion takes place. It consists of a series of phase separators interposed by pressure regulators. The purpose of the separator is to retain the liquid phase and allow the vapor phase to pass; and the purpose of the pressure reducer-regulator is to cause the steam to undergo isenthalpic expansion.

Line alone isenthalpic expansion in the line of condensation gives two tenths of the mass of the working fluid in the form of superheated vapor, and the remainder, in the form of a diphasic mixture mainly in the vapor state. With a staged isenthalpic expansion composed of two expansions, the result improves, because the superheated steam is reduced, but the diphasic mixture remains mainly in the form of steam, unfortunately this is not the desired goal. With a stepped isenthalpic trigger composed of three triggers, a good result is obtained. There are several possibilities of realizing the three isenthalpic expansions; for example: the first isenthalpic expansion from 9.5 bars to 7 bars, and the second isenthalpic expansion from 7 bars to 2 bars and the third isenthalpic expansion from 2 bars to 1 bar, and at the end a diphasic mixture containing 20 % vapor and 80% liquid. These percentage values only give the proportions of the non-condensed vapor during the second isenthalpic expansion, therefore they have no relation to the total mass of the contents of the intermediate tank.

From the start of the staged isenthalpic expansion, at the moment of the opening of the valve for the outlet of the vapor from the intermediate reservoir, it can be considered that the fluid leaving the said reservoir is a two-phase mixture. The latter arrives in the first separator of the condensation line, the liquid phase is retained, and the vapor phase continues its way to the first pressure reducer-regulator set at 7 bars. This first stage of the staged isenthalpic expansion gives the outlet of said regulator a superheated vapor for a very short time, then, after a certain time, a two-phase mixture is obtained, mainly in the vapor state, at a temperature of 14°C. . This two-phase mixture arrives in the second separator, the liquid phase is retained and the vapor phase continues on its way to the second pressure reducer-regulator set at 2 bars. This second step of the stepped isenthalpic expansion gives the outlet of said regulator a two-phase mixture having a temperature equal to -26°C. with a balanced titration. This two-phase mixture arrives in the third separator, the liquid phase is retained and the vapor phase continues on its way to the third pressure reducer-regulator set at 1 bar. This third and final stage of the staged isenthalpic expansion gives, at the outlet of said regulator, a two-phase mixture mainly in the liquid state having a temperature equal to -42°C. This two-phase mixture arrives in the fourth separator, the liquid phase is retained and the vapor phase is sucked up by a compressor and reintroduced into the condensation line for recycling. All the condensates retained in each of the separators will be withdrawn by condensate pumps, then passed through heat exchangers to exploit their cold, and to heat the condensate before reintroducing it into the steam generator. If the volume of the intermediate tank is kept constant during the expansion, the escape of the vapor towards the line of condensation will cause a pressure drop of the temperature and the material; this change will have consequences on the staged isenthalpic expansion. Thus, when the pressure drops to 7 bars, the first regulator no longer plays its role, because it is completely open, and when the pressure drops to 2 bars, the second regulator no longer plays its role, because it is completely open, and when the pressure drops to 1 bar, the third regulator no longer plays its role, because it is completely open. At this point, the three regulator expansion valves are open, and at this moment they have started to pump water inside the intermediate tank, to fill it with water and to force the residual two-phase mixture to go towards the condensation line. .

Each splitter has one input and two outputs. The inlet is reserved for the two-phase liquid-vapor mixture, and for the two outlets: the main outlet is reserved for the condensate draw-off; and the secondary outlet is reserved for the steam outlet. Except for the separator reserved for receiving the non-condensed vapor to be recycled, which has a second inlet reserved for receiving the vapor from the compressor.

The pumping stage consists of all the condensate pumps; each separator has its own pump, the role of which is to compress the condensate for two reasons: first, to prevent its evaporation in the pipes, since its passage through the heat exchangers, will inevitably lead to an increase in its temperature; and the second reason is to facilitate its introduction into the steam generator in which a high pressure prevails.

The operating cycle of each intermediate tank consists of three stages, these three stages are distinguished from each other by the opening of one or more of the four valves fitted to said intermediate tank, and keeping the other valves closed : a first step of admitting steam and discharging water to the pressure accumulator; followed by the second stage of isochoric exhaust of steam to the condensation line; followed by the third stage of water filling and steam evacuation to the condensation line, the execution of each stage must meet the following conditions: the execution of the first stage is conditioned by the sending of a signal from the high water level detector to the digital control-command system, the latter checks whether the other two stages in the other two tanks have been completed, if so, it controls the simultaneous opening of the valve d steam inlet and water outlet to the pressure accumulator, and all other valves must be closed, this situation is maintained until the low water level sensor sends a signal to the digital control-command system; on receipt of the signal from the low water level detector by the digital control-command system, the latter checks whether the other two stages in the other two tanks have been completed, if so, it orders the execution of the second stage which consists of the simultaneous closing of the valves opened during the first stage, before the opening of the valve for the outlet of the steam to the liquefaction stage; all other valves must be closed. This stage corresponds to the expansion of the steam, and ends when the pressure inside the tank intermediate drops to 1 bar. At this moment, the pressure sensor sends a signal to the digital control-command system, thus marking the end of this stage; on receipt of the signal from the low water pressure sensor by the digital control-command system, the latter checks whether the other two stages in the other two tanks have been completed, if so, it commands the execution of the third stage, which consists of opening the water inlet valve in the intermediate tank while keeping the steam outlet valve open, and the other valves must be closed. This step corresponds to the evacuation of the expanded residual steam, and the filling of the tank with water to prepare it for a new cycle. This stage ends with the filling of the tank with water, and. it is signaled to the control-command system by the high water level detector.

The method of synchronizing the operation of a group of intermediate tanks is based on the operation cycle of a single intermediate tank; and it aims to ensure a continuity of a water flow towards the hydraulic loop so that, when the evacuation of the water towards the hydraulic loop ends in a tank, it must resume in the next tank. Since the cycle of operation of a tank consists of three stages, then a group of three intermediate tanks perfectly meets this requirement, the synchronization method therefore consists in having the three stages run at the same time, but, each in a tank different. So, during normal operation, when the first stage is running in the first tank, the third stage should be running in the second, and the second stage should be running. execution in the third tank, the steps must start simultaneously, provided that the steps are completed in all three tanks, this method requires a digital control system.

The physical properties of propane: it is only soluble in water in very small quantities (75 milligrams per liter at 20°C), so bringing it into contact with water does not pose a problem for proper operation of the thermodynamic cycle, especially in the conditions where it is placed in direct contact with water, as is the case in the intermediate reservoirs, and in the pressure accumulator; In addition to its low boiling point (-42°C) and its good saturation vapor pressure at ambient temperature (oceans and atmosphere) in tropical regions (where the temperature is around 25°C, which corresponds to a pressure of approximately 9.5 bar.); in addition to the availability of its MolUer enthalpy diagram on which is plotted the work cycle according to the operation of said converter object of this invention.

The use of propane as a working fluid in said converter which is the subject of this invention makes it possible to extract calories from media whose temperature is between -15° C. and 80° C.; for temperatures between -15°C to 30°C, the converter produces cold in addition to electricity, and between 30°C and 80°C, it tends to produce heat in addition to electricity .

The temperature difference between the boiling point and the critical point is very interesting. From a theoretical point of view, and according to the converter proposed by this invention, any cycle traced between these extreme temperatures must operate to produce electricity with more or less good efficiency depending on the flattening of the cycle. So, there are several possibilities to draw different cycles, which can be classified into three categories. A category that produces electricity and cold, a category that produces electricity, and a category that produces heat and electricity, there is also the possibility of making a staged cycle, to produce electricity from heat and cold at the same time. The most important thing in this possibility is to make the converter applicable in all places of the earth, because liquid water exists even under the ice floe in the polar regions.

Case of temperate regions, where the sea water temperature is 25 degrees Celsius. At this temperature, propane: liquefied petroleum gas (LPG), has a saturation vapor pressure equal to 8.5 bars (relative pressure), and a specific volume of 50 liters, as if 1 kg of propane, vaporizing , it is able to move a volume of water at a height of 85 meters, which represents a potential energy Ep = m.g.h - 42.5 KJ. Even with a hydraulic turbine with poor efficiency of 75%, and taking into account the consumption of electrical energy to supply the unit's auxiliaries, the overall balance will remain above 50%.

Case of a hot spring, where the water temperature is 78 degrees Celsius. At this temperature, propane: liquefied petroleum gas (LPG), has a saturation vapor pressure equal to 30 bar (relative). Such a pressure will have no effect on the performance of the installation operating according to the object process of this invention, but will have consequences on the cost of the equipment which will increase enormously, so here a change of the working fluid is necessary. , butane or isobutane or others, will be better suited to this type of situation.

Case of cold regions, where the sea water temperature is close to zero degrees Celsius. At this temperature, propane liquefied petroleum gas (LPG), has a saturation vapor pressure equal to 5 bars (relative pressure), and a specific volume of 100 liters, if we convert this pressure energy into potential energy Ep = mgh = 40 Kj. The advantage of working with low pressures is the possibility of using less expensive plastic material.

According to a particular preferred embodiment, and in accordance with the converter proposed by this invention, it consists of an individual micro-installation with a power of one kilowatt (1 KW). the design of such an installation depends on the parameters of the workplace; the choice of working fluid; and parameters dependent on the geometry of the machine; these last parameters depend on the choice of the designer of such a project.

The place imposes the ambient temperature (sea water or atmosphere); and the choice of the working fluid imposes a saturation vapor pressure, and consequently imposes the speed of the water which.acts.on.the.hydro.turbine. The power of the installation is. designer's choice. This choice can vary from an installation of a few kilowatts, to installations of the order of a gigawatt, or even more. Generally what makes the difference between a small and a large installation is the number of steam generators constituting the stage of the steam generators; the number of groups of intermediate tanks and the volume of the tanks, the number of hydraulic loops and the dimensions of the turbine or hydraulic turbines, as well as the number of condensation lines.

With regard to the installation of a power of one kilowatt, we start from an ambient temperature T = 25 °C; propane is the working fluid, its saturated vapor pressure = 9.5 bars, specific volume = 50 liters; the pressure inside the pressure accumulator which supplies water to the hydraulic turbine is fixed at 9 bars, from this pressure the speed of the water which acts on the hydraulic turbine is calculated, this speed is 40 m /s approximately, with a mass flow of 1.25 kg/s of water. the duration of a cycle which is related to the volume of the intermediate tanks, and the speed of liquefaction of the steam. In the case of the installation of a power of one kilowatt, a duration of 5 minutes per cycle is reasonable, this imposes a volume of the intermediate tanks of 125 liters each, and the tanks of the phase separators of a volume of 5 liters each, the speed of liquefaction of the steam plays an important role on the duration of the cycle, since the speed of the steam must be within the standards, a speed of 30 m is reasonable, and the section of the pipes must be adapted in which the steam circulates. the heat exchange surface of a copper tube with a diameter of 25 mm, a thickness of 3 mm, and a length of 2.5 m, is capable of generating 1.25 liters of steam per second.

According to a preferred embodiment of the converter object of this invention, which consists in installing all the components of the converter on board a floating or fixed platform, installed at sea not far from the coast. Such an installation is called a maritime installation, it benefits from the advantages of the high heat capacity of water, and the incessant agitation of seawater which is constantly renewing itself, which makes it possible to to save on the heat exchange surface of the steam generators.

In addition to the production of electricity, the installation can use all or part of the electricity produced, for the desalination of sea water. To facilitate access to the platform, and facilitate the electrical connection to the network public and the connection of the piping to the installations located on land, it would be wise for it to be very close to the coast. It is essential to ensure that the steam generators saw permanently submerged in water. In a marine installation, the use of propane or other similar fluid as the working fluid is the right choice.

According to another preferred embodiment of the converter which is the subject of this invention, which consists in mounting only the steam generator stage on board a floating platform as indicated previously, all the rest of the installation will be installed on land. Such an installation benefits from the advantages of a maritime installation, and from the advantages of an installation on land which avoids the personnel who watch over the smooth running of the installation having to move towards the floating platform. In this type of installation, the use of propane or another similar fluid as the working fluid is the right choice.

According to another preferred embodiment of the converter object of this invention, consists in mounting all the stages constituting the converter on board a large boat or on board a submarine to produce electricity for the propulsion and for all the other services on board, including the production of fresh water. Such an achievement will have positive consequences for international shipping. Using propane or another similar fluid as the working fluid is the correct choice.

According to another preferred embodiment of the converter which is the subject of this invention, consists in mounting all the stages constituting said converter on the ground. Such an installation is called a terrestrial or atmospheric installation, and it requires a larger heat exchange surface and ventilation, and therefore a greater investment. But under certain conditions, such an installation can prove to be very useful or even essential, such as for example the electrification of isolated places.

According to another preferred embodiment of the converter which is the subject of this invention, consists in pumping sea water towards an onshore installation. If the problem of the availability of space very close to the sea does not arise for the establishment of the station, despite the inevitable consumption of electrical energy by the pumps, the installation will be more advantageous in comparison with a atmospheric installation using air as a heat source.

According to another preferred embodiment of the converter object of this invention, is to use said converter to produce electricity and cold. In this case, the steam generator of said converter must be installed in the place from which the calories are to be extracted, such as for example: a cold room.

According to another preferred embodiment of the converter object of this invention, is to use the operating principle of said converter to produce electricity by manufacturing scale models of a few kilowatts for personal use, mounted on mobile carts.

Brief description of the drawings

In the drawings which illustrate the invention, FIG. 1 is a plot of the special thermodynamic cycle on a Mollier enthalpy diagram of propane R-290, illustrating the various transformations undergone by propane during this cycle. FIG. 2 is an illustration of the various stages of the special thermodynamic cycle, symbolically representing the stage of the steam generators; the energy conversion stage containing a group of 3 intermediate tanks and the hydraulic loop; the liquefaction stage containing a condensation line with phase separators and pressure regulators; and finally the condensate pumps and the non-condensed residual steam compressor including the cold recovery heat exchangers for other miscellaneous uses. Figure 3 is a schematic representation of an intermediate tank and the accessories necessary for its normal operation; the broken lines represent the circuits connecting the various sensors with the digital control-command system, and the control circuits of the actuators which perform the opening or closing of the various valves.

Detailed description:

The diagram which best suits to trace the special thermodynamic cycle, is the Mollier enthalpy diagram of propane. This diagram is also known as the refrigeration diagram, which is a specific diagram for each working fluid. It is a very useful diagram for tracing the thermodynamic cycle. It allows direct reading of certain parameters, the abscissa (horizontal bar) designates the value of the mass enthalpy (in KJ/Kg) and the ordinate (vertical bar), the value of the pressure (in absolute bar ) on the logarithmic scale, vertical lines denote isenthalps, and horizontal lines denote isobars. The bell-shaped saturation curve defines the state of the working fluid, with its critical point at its peak. Isotiters represent the ratio of the mass of the vapor to the total mass of the fluid. Isochores represent curves where the volume does not change during a transformation, they intersect with the dew curve (left side), cross the saturation curve while tending towards low pressures, and approaching more in addition to the evaporation curve (right side) without intersecting with it.

Propane has interesting physical properties. First, it is only soluble in water in very small quantities (75 milligrams per liter at 20°C), so bringing it into contact with water does not pose a problem for the operation of the thermodynamic cycle. ; but the contaminated water circuit must be contained. At 25°C (temperature assumed to be that of the environment where the steam generator is placed), its saturation vapor pressure is equal to approximately 9.5 bars, and its specific volume is equal to approximately 50 liters, and this is precisely its two properties that will be exploited to produce useful work, propane has a very low boiling point -42°C, it can produce cold by the steam liquefaction method. The high critical point temperature of 97.5°C makes it possible to exploit other sources of recovery heat with a temperature below 90°C.

In accordance with the converter provided by this invention, and with reference to the drawings, Figure 1 shows the plot of the special thermodynamic cycle on the Mollier diagram of propane. The temperature of the place (sea water or atmosphere) is assumed to be equal to 25°C. The plot of said cycle illustrates the various transformations undergone by propane since its introduction into the steam generator in the liquid state. The horizontal line segment (1-2) represents the isobaric evaporation process that takes place in the steam generator. The staircase represented by the segments (2-6, 6-9, 9-7, 7-10, 10-8, 8-3), represents staged isenthalpic relaxation. The segment (3-4) represents a secondary isobaric transformation, and finally, the segments (4-5 and 5-1) represent the compression of the condensate in order to be able to inject it into the steam generator.

In accordance with the converter proposed by this invention, and with reference to the drawings, FIG. 2 is a very simplified schematic representation and comprising the minimum of equipment, it represents the stages constituting the installation of the said converter: the stage of the steam generators (11) must contain at least one steam generator (110); and the steam energy conversion stage (12) must contain at least one group of three intermediate tanks (15); the steam liquefaction stage (13) must contain at least one condenser comprising at least one condensation line; and finally, the pumping stage (14) consisting of all the condensate pumps (42) and the compressor (43) of the non-condensed steam. Still according to figure 2, the hydraulic loop is a confined hydraulic circuit (to avoid any direct contact of water with the atmosphere, because it contains traces of propane in solution), in which fresh water circulates in circuit farm. Said loop is constituted by the group of intermediate reservoirs (15) also belonging to the special thermodynamic cycle; a pressure accumulator (16); a hydraulic turbine (19) coupled to an electric generator (20); a water pan (17) to receive water leaving the turbine (19); and a hydraulic pump (18). The role of the latter is to evacuate the water from the tank (1.7) and push it back to said intermediate tank (15) available.

Still according to Figure 2. The operation of the hydraulic loop depends totally on the operation of the special thermodynamic cycle, the exchange of energy between these two circuits takes place in the intermediate tank (15), thanks to the pressure of the steam exerted on the water contained in said tank (15), that it is forced to escape towards the pressure accumulator (16), which is a pressurized tank, acting as a flow regulator, since it is designed to support irregularities on its inlet (160), and providing a constant flow of water, on its outlet (161) to power a hydraulic turbine (19); after leaving said turbine (19), the water is collected in a tank (17), then sucked up by a hydraulic pump (18), and pushed back to the available intermediate reservoir (15).

Still according to Figure 2, the pressure accumulator (16) is a pressurized tank. It has a water inlet (160) and an outlet (161) at the level of the part occupied by the water, and also has a steam inlet (162) and an outlet (163) at the level of the chamber to steam. It is filled half of its volume with fresh water (22), and the other half is occupied by steam from the working fluid, forming a steam chamber (21) which keeps it under pressure; this steam chamber is supplied with steam from the steam generator through a pressure regulator (164) installed at the steam inlet (162); and exhaust is through a relief valve (165) installed at the steam outlet (163) to the condensing line.

The pressure inside said pressure accumulator (16) must necessarily be lower than the saturated steam pressure which prevails in the steam generator (110) and in the intermediate tank (15) which discharges the water towards it, and it must be kept constant. The regulation system consisting of the pressure regulator (164) and the relief valve (165) ensures that a preset pressure is maintained constant to compensate for irregularities in the inflow of water caused by the opening and closing of the valves (25) of the group of intermediate tanks (15), and to ensure a constant flow of water outgoing towards the hydraulic turbine: when the pressure tends to drop, the regulator (164) allows the steam to pass to compensate for this drop, and when the pressure tends to increase, the relief valve (165) lets the steam escape to the condensation line. According to the converter object of this invention and with reference to the drawings, Figure 3, each intermediate tank (15) of a group must be insulated, its shape must preferably be cylindrical, and mounted in a vertical position. In addition, each tank must have on its upper part a steam inlet (24) coming from the steam generator, equipped with a motorized shut-off valve (23) and a steam outlet (26) towards the floor of liquefaction equipped with a motorized stop valve (25. On its lower part, it must have a water inlet (30) coming from the pump of the hydraulic loop, equipped with a motorized stop valve (29 ) and a water outlet (28) to the pressure accumulator equipped with a motorized shut-off valve (27). All the motorized shut-off valves are controlled by the digital control-command system. Each intermediate tank must be equipped with sensors, such as water level detectors (31) and (32), and pressure sensors (33).

Still according to Figure 3, the operating cycle of each intermediate tank consists of three stages, these three stages are distinguished from each other by the opening of one or more of the four valves fitted to said intermediate tank and keep the others closed: a first stage of admission of steam and evacuation of water to the pressure accumulator: followed by the second stage of isochoric exhaust of steam to the condensation line; followed by the third stage of water filling and steam evacuation to the condensation line, the execution of each stage must meet the following conditions: the execution of the first stage is conditioned by the sending of a signal from the high water level detector (31) to the digital control-command system (34), the latter checks whether the other two stages in the other two tanks have been completed, if so, it controls the simultaneous opening of the steam inlet valve (23) and that of the water outlet (27) to the pressure accumulator, the other two valves (25) and (29) must be closed, this situation is maintained until the low water level detector (32) sends a signal to the digital control-command system (34); on receipt of the signal from the low water level detector (32) by the digital control-command system (34), the latter checks whether the two other stages in the other two tanks have been completed, if so, it controls the execution of the second stage which consists of the simultaneous closing of the open valves (23), and (27) during the first stage, before the opening of the outlet valve (25) of the steam to the liquefaction stage; the other three valves (23, 27 and 29) must be closed. This step corresponds to the expansion of the steam, and ends when the pressure inside the intermediate tank drops to one bar (1 bar). At this moment, the pressure sensor 33 sends a signal to the digital control-command system, thus marking the end of this stage; on receipt of the signal from the pressure sensor (33) by the digital control-command system (34), the latter verifies whether the two other stages in the two other tanks have been completed, if so, it controls the execution of the third stage, which consists of opening the water inlet valve (29) in the intermediate tank while keeping the steam outlet valve (25) open, and the other two valves (23 and 27) must be closed. This step corresponds to the evacuation of the expanded steam, and to the filling of the reservoir (15) with water to prepare it for a new cycle. This step ends with the filling of the tank with water, and it is signaled to the control-command system (34) by the high water level detector (31).

The method of synchronizing the operation of a group of intermediate tanks is based on the operation cycle of a single tank; and it aims to ensure continuity of a flow of water to the hydraulic loop so that when the evacuation of water to the hydraulic loop ends in a tank, it must resume in the next tank. Since the cycle of operation of a tank consists of three stages, then a group of three intermediate tanks perfectly meets this requirement, the synchronization method therefore consists in having the three stages run at the same time, but, each in a tank different. So, during normal operation, when the first stage is running in the first tank, the third stage should be running in the second, and the second stage should be running. execution in the third tank. The steps must start simultaneously, provided that the previous steps are completed in all three tanks, this method requires a digital control system.

In accordance with the converter proposed by this invention, and with reference to the drawings in FIG. 1 and FIG. 2, the liquefaction method consists in subjecting the pressurized steam contained in the intermediate tank 15 to a staged isenthalpic expansion. This method requires allowing the steam to escape to the last low pressure separator 41 in which there is a pressure equal to one bar (1 bar), through the condensation line.

From the start of the isochoric expansion, at the time of the opening of the steam outlet valve (25) of the intermediate tank (15), it can be considered that the fluid leaving said tank is a two-phase mixture. The latter arrives in the first separator (35) of the condensation line, the liquid phase is retained, and the vapor phase continues its way to the first pressure reducer-regulator (36) set at seven bars.

This first step of the staged isenthalpic expansion gives the outlet of the said expander for a very short time a superheated vapor represented by the small horizontal segment delimited by the points (6-6')(figure 1), then, after a certain time a two-phase mixture is obtained mainly in the vapor state at a temperature of 14°C. This diphasic mixture arrives in the second separator (37), the liquid phase is retained and the vapor phase continues its way to the second expansion valve (38) set at two bars.

This second step of the stepped isenthalpic expansion gives, at the outlet of the said regulator, a two-phase mixture with an average titration, having a temperature equal to -26°C. This diphasic mixture arrives in the third separator (39), the liquid phase is retained and the vapor phase continues on its way to the third expansion valve

(40) set at one bar.

This third and final stage of the stepped isenthalpic expansion gives, at the outlet of said regulator, a two-phase mixture, mainly in the liquid state, having a temperature equal to -42°C. This diphasic mixture arrives in the fourth separator

(41), the liquid phase is retained and the. vapor phase is aspirated by a compressor (43) is reintroduced into the condensation line for recycling. All the condensates retained in each of the separators will be withdrawn by condensate pumps (42), then passed through heat exchangers (43) to exploit their coldness, and to heat the condensate before it is reintroduced into the steam generator.

In the line of condensation, and in accordance with Figures 1 and 2, a graphic interpretation makes it possible to better explain the consequences of the escape of the two-phase mixture from the intermediate tank on the staged isenthalpic expansion represented by the staircase drawn in continuous lines formed by the segments (2-6, 6-9, 9-7, 7-10, 10-8 and 8-3).

Note that the opening of the expansion valve is a function of the pressure difference between its inlet and its outlet, and also note that the phase separators retain the liquid phase and allow only the vapor phase to pass. At the start of the isenthalpic expansion, the steam arrives at the inlet of each expansion valve (36, 38, 40) with a maximum pressure difference, see the vertical segments (2-6, 9-7 and 10-8) ; then, over time, the first expander-regulator (36) will begin to open as a result of the gradual drop in pressure at its inlet; as if the segment of the isenthalp (2-6) included between the section of the curve of the isochore 50 liters (56), and the isobar seven bars, moves horizontally on the segment (6-9), and becomes smaller and smaller, until points (2 and 6) merge with point (9) when the pressure drops to seven bars; at this time, the first expansion valve (36) is completely open.

Now, with the pressure continuing to drop, it is the turn of the second regulator-regulator (38) which is affected by the pressure drop across its inlet. At the start, the pressure difference (9-7) is maximum, then over time, this difference becomes smaller and smaller, as if the segment of the isenthalp (9-7) between the section of the curve of the fifty liter isochorus (56), and the two bar isobar moves horizontally on the segment (7-10), and becomes smaller and smaller, until the points (9) and (7) meet merge at point (10) when the pressure drops to two bars; at this moment, the second expansion valve is completely open. the same thing happens to the third expander-regulator (40), as soon as the second expander-regulator (38) is completely open. The pressure on its inlet, which was stable throughout the expansion when the two expander-regulators (36, 38) become operational, now the pressure will begin to drop on its inlet, which will affect the pressure difference ( 10-8) between its input and its output; as if the segment of the isenthalp (10-8) comprised between the stretch of the isochore curve fifty liters, and. the isobar a bar, moves horizontally on the segment (8-3), and becomes smaller and smaller, until the points (10) and (8) merge with the point (3) when the pressure drops to one bar; at this moment, the third expansion valve-regulator (40) is completely open. It should be understood that the foregoing detailed description is an example whose purpose is to facilitate understanding of the operation of said energy converter, and has no limiting character, because even if the operating principle remains the same, the execution options are very varied.

Claims

Claims.

1- Converter of very low temperature calorific energy, and in particular the calorific energy of solar origin stored in the water of the oceans and in the atmosphere into electrical energy, characterized by two closed circuits which exchange work between them, these two circuits are: a -) a closed circuit in which evolves a suitable working fluid in a closed circuit composed of the following stages:

- a stage of steam generators (11) comprising at least one steam generator (llü);

- an energy conversion stage (12) comprising at least one group of intermediate reservoirs (15);

- a steam liquefaction stage (13) comprising at least one condenser comprising at least one condensation line, which is an adiabatic circuit in which the steam undergoes staged isenthalpic expansion; and

- A pumping stage (14) and compression composed of all the condensate pumps (42), and the compressor (43) of the non-condensed steam. b -) a hydraulic loop comprising:

- a group of intermediate tanks (15) also belonging to the circuit of the special thermodynamic cycle;

- a pressure accumulator (16);

- a hydraulic turbine (17) which drives an electric generator (20);

- a tank (17) which receives the water as it leaves the turbine; and

- a hydraulic pump (18) which draws water from said tank and delivers it to said group of intermediate tanks (15) to drive out the expanded steam.

2 - The very low temperature calorific energy converter according to claim 1, characterized in that: said intermediate tank (15) has on its upper part an inlet and a steam outlet, and on its lower part, it has a inlet and an outlet for the water which circulates in the circuit of said hydraulic loop.

3 - The very low temperature calorific energy converter according to claim 1, characterized in that: each intermediate tank (15) is equipped with level detectors (31, 32), pressure detectors (33) and all the accessories necessary for connection to the control-command system (34) which ensures the synchronization of the operating steps of each group of intermediate tanks.

4 - The very low temperature calorific energy converter according to claim 1, characterized in that: said pressure accumulator (16) has on its upper part an inlet (162) and an outlet (163) of steam, and on its lower part it has a water inlet (160) coming from the intermediate reservoir (15) and a water outlet (161) to supply the hydraulic turbine (19).

5 - The very low temperature calorific energy converter according to claim 1 and 4, characterized in that: said pressure accumulator (16) is equipped on its upper part of a pressure regulation system composed of a pressure reducer-regulator (164) installed on the steam inlet (162), and a relief valve (165) installed on the steam outlet steam (163).

6 - The very low temperature calorific energy converter according to claim 1, characterized in that: inside said pressure accumulator (16), the lower part is occupied by a variable volume of water (22), surmounted a vapor chamber (21) with variable volume under a constant pressure fixed in advance.

7 - The very low temperature heat energy converter according to claim 1, characterized in that said condensation line comprises a head phase separator (35) and a final separator (41), and between the two there is installed a sufficient number of expanders-regulators (36, 38, 40) alternated by intermediate phase separators (37, 39).

8 - Very low temperature calorific energy conversion method, and in particular the calorific energy of solar origin stored in the water of the oceans and in the atmosphere into electrical energy, said method of conversion is characterized by the following steps : a - ) a first stage which takes place in the stage of the steam generators (11) during which said calorific energy is transformed into pressure energy, thanks to a special organic thermodynamic cycle using propane or other similar fluid as working fluid, suitable for the exploitation of very low temperature heat energy sources, and in particular said heat energy of solar origin; b - ) a second stage which takes place in the energy conversion stage (12) during which the steam pressure energy is communicated to said hydraulic loop, it is thanks to the action of the pressurized steam from the stage of the steam generators on the volume of water contained in the said intermediate tank, that the latter is expelled towards the pressure accumulator (16) of the said hydraulic loop, where there is a pressure lower than the vapor pressure of said intermediate tank (15); vs. - ) a third step which results in the production of electric current, which takes place within said hydraulic loop during which the energy communicated to said loop and stored in said pressure accumulator (16) in the form of potential energy , and it is returned in the form of a constant flow of water to supply a hydraulic turbine (19) coupled to an electric generator (20): and d - ) a fourth stage of liquefaction of the steam which takes place in the steam liquefaction stage, during which the steam undergoes staged isenthalpic expansion in said condensation line, which, according to the Joule-Thomson principle, results in a drop in temperature and partial liquefaction of the steam.

9 - The very low temperature calorific energy conversion method according to claim 8, characterized by a special thermodynamic cycle during which the working fluid undergoes the following transformations: a - ) isobaric transformation (1-2) during which the working fluid is brought to a boil, under the action of the heat flux which crosses the wall of the steam generator and is transformed into steam under pressure, thus the heat energy is transformed into pressure energy; b - ) staged isenthalpic transformation (2-6, 9-7, 10-8) which takes place in the steam liquefaction stage (13) during which the steam is partially liquefied; c - ) secondary isobaric transformation (3-4) during which the expanded steam which still occupies the intermediate tank (15) is forced to leave the latter, thanks to a hydraulic pump (18) which sucks up the water collected in said tray (17) at the outlet of the hydraulic turbine (19), and discharges it inside said intermediate reservoir (15); and d - ) isochoric transformation (4-5) during which the condensate is withdrawn from the phase separators (35, 37, 39, 41) by condensate pumps (42), and reintroduced into the said steam generator (110 ).

10 - The very low temperature calorific energy conversion method according to claim 8, characterized in that the hydraulic loop which is a closed and confined water circuit operates as follows: in said intermediate tank (15) supposed to previously filled with water, the action of pressurized steam expels the water contained therein towards said pressure accumulator (16) where there is a pressure lower than that of said intermediate tank where it is stored in the form of energy potential, and will be returned in the form of a constant flow to supply the hydraulic turbine (19) coupled to an electric generator (20) which produces the electric current, then, at the outlet of the turbine (19), the water is recovered in a tank (17), and finally, a hydraulic pump (18) sucks up this water and delivers it to said intermediate tank (15).

11 - The very low temperature calorific energy conversion method according to claim 8, characterized in that the operation of the pressure accumulator (16) requires certain precautions:

- for the flow of water from said intermediate tank (15) to said pressure accumulator (16) to take place, the pressure of said vapor chamber (21) inside said pressure accumulator must necessarily be lower to the saturated steam pressure which prevails in said steam generator (110) and in said intermediate tank (15) which discharges the water towards it;

- to compensate for irregularities in the incoming water flow caused by the opening and closing of the valves of said group of intermediate tanks (15), and to keep a stable regime at the outlet of said pressure accumulator (16), it is necessary to maintain the constant pressure in the vapor chamber (21) by an automatic regulation system (34); - said steam chamber (21) is supplied with steam from a generator, not necessarily the same steam generator (110) which supplies said group of intermediate tanks (15), through a pressure regulator installed at the steam inlet (164), and the exhaust must be to said condensation line through the relief valve (165) installed on the steam outlet pipe (163); and - the regulation system (34) reacts as follows: when the pressure tends to drop, the regulator (164) lets the steam pass into said pressure accumulator to compensate for this drop and when the pressure tends to increase the relief valve (165) lets the steam escape to said condensation line.

12 - The very low temperature calorific energy conversion method according to claim 8, characterized in that the operating cycle of each intermediate tank (15) consists of three stages, these three stages are distinguished from one of the another by opening one or more of the four valves (23, 25, 27, 29) fitted to said intermediate tank (15), and to keep the other valves closed: the first stage corresponds to the admission of steam and draining water to said pressure accumulator; the second stage corresponds to the isochoric escape of the vapor towards the said condensation line; and the third stage corresponds to the filling of said intermediate tank (15) with water and the evacuation of the steam towards the condensation line, the execution of each stage must meet the following conditions: - the execution of the first stage is conditioned by sending a signal from the high water level detector (31) to said digital control-command system (34), the latter checks whether the two other stages in the other two tanks (15) are completed, if so, it controls the simultaneous opening of the steam inlet valve (23) in said intermediate tank, and that of the water outlet (27) to the pressure accumulator, the other two valves (25, 29) must be closed, this situation is maintained until the low water level detector (32) sends a signal to the digital control-command system (34);

- upon receipt of the signal from the low water level detector (32) by the digital control-command system (34), the latter checks whether the two other stages in the other two tanks have been completed, if so , it controls the execution of the second stage which consists of the simultaneous closing of the valves opened (23, 27) during the first stage, before the opening of the steam outlet valve (25) to the floor liquefaction, the other three valves (23, 27, 29) must be closed, this step corresponds to the expansion of the steam in the said intermediate tank (15) caused by the exit of the steam, and ends when the pressure at the the interior of said intermediate tank (15) drops to 1 bar, at which time the pressure sensor (33) sends a signal to the digital control-command system (34), thus marking the end of this stage; and

- upon receipt of the signal from the pressure sensor (33) by the digital control-command system (34), the latter checks whether the other two stages in the other two tanks have been completed, if so, it controls the execution of the third step, which consists of opening the water inlet valve (29) in said intermediate tank ()15 while keeping the steam outlet valve (25) open, and the two other valves (23, 27) must be closed, this step corresponds to the evacuation of the expanded steam, and to the filling of the said tank (15) with water to prepare it for a new cycle, this step ends with the filling of the tank (15) in water, and it is signaled to the control-command system (34) by the high water level detector (31).

13 - The very low temperature calorific energy conversion method according to claim 8, characterized in that said condensation line is an adiabatic circuit in which the vapor of the working fluid undergoes a stepped isenthalpic expansion, which results according to the principle of Joule-Thomson by a cooling and a partial condensation of the vapor.

14 - Method of synchronizing the operation of said group of intermediate tanks according to all the preceding claims is based on said operating cycle of a single intermediate tank (15), and it aims to ensure continuity of a water current towards said hydraulic loop in such a way that when the evacuation of water to said hydraulic loop ends in one tank (15), it must resume in the next tank, since the operating cycle of a tank consists of three stages , then a group of three intermediate reservoirs (15) meets this requirement perfectly, the synchronization method therefore consists of having the three steps executed at the same time, but each in a different reservoir (15), thus, during normal operation, when the first stage is running in the first tank, the third stage should be running in the second, and the second stage should be running in the third tank, the stages must start simultaneously, provided that the three stages are completed in the three tanks, this method requires a digital control-command system (34).