WO2018069845A1

WO2018069845A1 - Regeneratively utilising heat in a thermodynamic cycle

Info

Publication number: WO2018069845A1
Application number: PCT/IB2017/056283
Authority: WO
Inventors: Johan Adam ENSLIN
Original assignee: Enslin Johan Adam
Priority date: 2016-10-11
Filing date: 2017-10-11
Publication date: 2018-04-19
Also published as: ZA201901887B

Abstract

This invention relates to a method of and system (100, 200) for regeneratively utilising heat in a thermodynamic cycle. The method includes the steps of extracting working vapour from a first reactor (102, 202), compressing and introducing the compressed working vapour to working liquid in the first reactor (102, 202). Working liquid (120, 222) is further extracted from the first reactor (102, 202), compressed, heated and evaporated to produce a first stream of heated working vapour (128, 232). This first stream of heated working vapor (128, 232) is expanded to obtain usable energy and produce a first stream of exhaust working vapour (132, 240). This first stream of exhaust working vapour (132, 240), combined with the compressed working vapour (116, 236), is introduced to a body of binary working liquid, whereby this working vapour is absorbed by the body of binary working liquid to thereby heat it.

Description

REGENERATIVELY UTILISING HEAT IN A THERMODYNAMIC CYCLE

FIELD OF INVENTION This invention relates to a method of and system for regeneratively utilising heat in a thermodynamic cycle. More particularly, but not exclusively, this invention relates to a method of and system for regeneratively utilising heat in a modified organic Rankine cycle that includes heat generation by means of heat of solution in binary fluid mixtures.

BACKGROUND TO THE INVENTION

The Rankine cycle, or variants thereof, is well known and widely used to convert heat energy into mechanical and as a result electrical energy. The Rankine cycle generally consists of the following four steps:

Step 1 : pumping a working medium, in a liquid form, and at low temperature and pressure to form high pressure working liquid;

Step 2: heating the high pressure working liquid to boiling (saturation) temperature and evaporating such working liquid at the constant high pressure to form heated high pressure working vapour;

Step 3: expanding (approximating isentropic expansion) the working vapour to a lower temperature and pressure, delivering power in this process; and Step 4: condensing the expanded low pressure vapour by latent heat removal with a cooling medium to a liquid condensate, ready for repeating the cycle starting again at step 1 described above. Conventionally, heat is provided to the input heat exchanger by means of hot combustion gasses of a furnace. Some of the heat is then transferred to the working liquid used in the Rankine cycle, by first heating the working liquid and then evaporating the liquid to vapour. The vapour may also be superheated to a degree to ensure that it remains a vapour during the expansion process in step 3 above, in order to avoid turbine blade erosion by liquid condensation droplets in the final stages of the turbine. For the same reason, some Rankine cycles have a series of sequential expansion turbines, with the partially expanded vapour exiting one turbine and reheated in a boiler section before expansion continues in the next turbine.

The Carnot cycle represents the thermodynamic cycle for a heat engine delivering the highest possible first order efficiency of any thermodynamic cycle for a heat engine working between the specific high and low temperatures and serves as the benchmark against which thermodynamic cycles for heat engines are measured. In the Carnot cycle, the pumping process of the Rankine cycle is replaced by an isentropic compression process, where heat from the compression and condensing processes heat the liquid to saturation. No heat is therefore required from a boiler (input heat exchanger) to heat the working liquid to the boiler saturation temperature. All boiler heat transferred to the working fluid in the Carnot cycle is done at a constant evaporation temperature, while all rejected heat is rejected at a single, constant lower condensation temperature. Due to its low power density, Carnot machines (or heat engines approaching Carnot efficiency) are generally only built for experimental purposes and have very low power output.

Real regenerative Rankine cycles, as used by utility power generation, use a stepwise approximation of the ideal regenerative Rankine cycle, by using a series of consecutive isentropic expansion turbines in cascade with vapour extraction points after each turbine. Extracted vapour is then used to stepwise heat the feed water to saturation temperature. If the expansion steps are very small, for example by having a large number of feed heaters, the approximation becomes better and the efficiency of the cycle improves closer to the ideal Carnot efficiency. Sometimes thermal energy is available at relatively low temperatures, typical of geothermal heat sources which may be available as hot water with very little, if any, vapour present. To make the most of any available energy in this heated medium, a so-called "Tri-lateral flash cycle" was developed after efficient dense fluid expanders became available on the market. Two patent applications were filed by U ir Liquide SA in respect of this cycle, the first of which was filed in 2006 under EP 1752615 and the second in 2008 under EP 2131 105. According to this cycle, a liquid medium is pumped by a liquid pump into an input heat exchanger (boiler), where the liquid is heated at constant pressure to a saturated liquid. No evaporation (or only a minimal amount) takes place in the boiler. The saturated liquid is then allowed to expand isentropically in a cascade or series of dense fluid expanders to produce power. As the isentropic expansion of a pure vapour is generally more efficient than expanding a mixture of liquid and vapour, additional vapour expanders are sometimes added to the cycle. The vapour portion of the two-phase mixture exiting the dense fluid expanders may then be routed to an additional pure vapour expander, which when exiting the additional pure vapour expander discharges into a condenser, where the latent heat in the vapour is rejected to cooling water at a low temperature being close to ambient.

Examples of such positive displacement type expanders include the likes of the so-called "Lysholm Turbine", sliding vane and screw-type expanders, liquid ring and scroll-type expanders, as well as the Helidyne LLC quad rotary helical interleaving rotors. A special two-phase turbine like the "Turbine Engine", invented by Jack Dean and published under WO 2007/053157 in May 2007, may also be used as a dense fluid expander. The "Turbine Engine" invention discloses a turbine developed for utilisation, amongst others, of a two-phase media for extracting power, with any liquid, vapour or combination thereof serving as working medium. It optimizes the nozzles used for the medium present at the nozzle inlet. In a previous disclosure also by Jack Dean, under international publication number WO 2013/064858, a method and apparatus for converting heat energy into mechanical energy was disclosed to operate on the regenerative Rankine cycle. According to this invention, liquid is stepwise pumped by a series of pumps from a condenser to an input heat exchanger or boiler, in counter flow to isentropically expanding vapour which exits from the boiler. After partial expansion of the vapour in a turbine, the discharging vapour is injected into a dense fluid expander to partially heat the liquid in the dense fluid expander before the vapour again discharges from the dense fluid expander into a second turbine to again partially expand further in the turbine. This sequence of isentropic expansion is repeated in various turbines resembling isothermal expansion.

In all the prior art discussed above, higher efficiency is sought by attempting to increase the expansion efficiency of the turbines or positive displacement expansion machines. In doing so, isentropic expansion can be approximated, while "carnotizing" by extracting heat from expanding media to form regenerative liquid heating trains. This led to higher efficiency, although still below the ideal carnot efficiency, but lower power density, and all of them still reject latent heat in a low temperature condenser. The thermodynamic efficiency of any heat engine is calculated as the power developed, divided by the heat input to the cycle.

Several attempts were also made to make use of latent heat, even if just using it for binary cycles to also generate refrigeration power with absorption refrigeration principles, in addition to power generation. One such thermodynamic cycle is the so-called Goswami Cycle which uses ammonia in water binary solutions to generate power, as well as provide refrigeration in the same cycle. This cycle is optimized for delivering power using an isentropic turbine, but also delivering refrigeration in the low turbine output vapour temperature. This cycle is further optimised for lowering the amount of heat rejection in an absorber. Cooling water carries away excess rejected heat from the low pressure and temperature absorber. The efficiency of this type of binary cycle can also not be readily compared to Carnot efficiency, as the generation of refrigeration make it necessary to add the refrigeration heat to the power developed before dividing it by the external heat input, making efficiency values appear higher than the (Carnot) maximum allowed first order thermodynamic efficiency.

Another example is disclosed in US Patent Application number US2016/0201521 , entitled "Energy generation from waste heat using the carbon carrier thermodynamic cycle". This disclosure teaches the principles of heat transformers, but specifically where pure carbon dioxide (CO2) is used as primary working fluid, using waste heat at some 20°C - 70°C to create much higher temperatures of 130°C - 200°C, by utilising the heat of solution ('HOS') of CO2 being dissolved. The heat transformer may also produce low temperatures as low as about -20°C for use as a refrigeration source. Further interesting developments is disclosed in the patent application of the so- called "Hygroscopic Cycle" under international publication number WO 2010/133726, entitled "Rankine cycle with an absorption step using hygroscopic compounds". This cycle avoids the low temperature (e.g. 30°C - 40°C) cooling water required by conventional Rankine cycle power generation, by replacing the condenser with a low-pressure absorber, which is pressure insensitive. The low- pressure steam is absorbed in liquid hygroscopic compounds (instead of being condensed), recycled by boiling it off in the heat generator or boiler. This way the heat rejection (at the same pressure as what the condenser was before) may take place at a much higher temperature of cooling water (e.g. 50°C - 60°C), increasing the power generated (and efficiency) of Rankine cycles by lowering the absorber pressure, even with higher temperature cooling water, especially those used in warmer climates.

OBJECT OF THE INVENTION

It is accordingly an object of the present invention to provide a method of and system for regeneratively utilising heat in a thermodynamic cycle that seeks to, at least partially, alleviate the above disadvantages and/or will be a useful alternative to the above described systems and methods, achieving a higher operating efficiency.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a method of regeneratively utilising heat in a thermodynamic cycle, the thermodynamic cycle utilising a working liquid and working vapour, each including a binary mixture containing a first chemical composition and a second chemical composition, the first chemical composition having a lower boiling point temperature than the second chemical composition, the method including the steps of:

- extracting working vapour, as a first stream of working vapour, from a first reactor having an operatively upper end and an operatively lower end, compressing the first stream of working vapour to produce a first stream of compressed working vapour, and introducing the first stream of compressed working vapour to working liquid in the first reactor whereby the compressed working vapour is absorbed by the working liquid to thereby heat the working liquid; - extracting working liquid, as a first stream of working liquid, from the first reactor, compressing the first stream of working liquid to produce a first stream of compressed working liquid, and heating by means of a first heat source, being in the form of a body of working liquid, the first stream of compressed working liquid to produce a first stream of heated working vapour;

- expanding the first stream of heated working vapour to obtain usable energy and produce a first stream of exhaust working vapour; and

- introducing the first stream of exhaust working vapour to the body of working liquid, whereby the exhaust working vapour is absorbed by the body of working liquid to thereby heat it.

The first reactor may be operated wherein the working vapour therein may be in communication with and located operatively above the working liquid therein. The first reactor may also be operated wherein the working vapour therein is present only in proximity of the operatively upper end.

There is provided for the body of working liquid to be located in and form part of the working liquid in the first reactor. Alternatively, the body of working liquid may be at least partially located in a second reactor.

The first stream of working vapour may be extracted from the proximity of the upper end of the first reactor. The first stream of compressed working vapour may be introduced in the proximity of the lower end of the first reactor.

The first stream of working liquid may be extracted from the proximity of the upper end of the first reactor.

The first stream of exhaust working vapour may be introduced in the proximity of the lower end of the first reactor. Alternatively, the first stream of exhaust working vapour may be introduced in the proximity of an operatively lower end of the second reactor.

The first reactor may be operated to have a temperature gradient from its operatively upper end to its operatively lower end, wherein the temperature increases in an operatively downwardly direction. According to example embodiments of the invention, there may be a temperature difference between the operatively upper and lower ends being any one of:

- at least 25 degrees Celsius;

- at least 50 degrees Celsius;

- at least 75 degrees Celsius; and

- at least 100 degrees Celsius.

The introduction of the first stream of compressed working vapour to the working liquid in the first reactor may assist in maintaining the temperature gradient over the first reactor. The first reactor may be operated to have a concentration gradient of the first chemical composition relative to the second chemical composition from its operatively upper end to its operatively lower end, wherein the concentration of the first chemical composition relative to the second chemical composition increases in an operatively upwardly direction. Similarly, the concentration of the first chemical composition relative to the second chemical composition decreases in an operatively downwardly direction.

According to example embodiments of the invention, working liquid in proximity of the operatively upper end and working liquid in proximity of the operatively lower end may respectively include any one of the following concentration distributions:

- the working liquid in proximity of the operatively upper end including at least 70 mole percent of the first chemical composition and less than 30 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 70 mole percent of the second chemical composition and less than 30 mole percent of the first chemical composition;

- the working liquid in proximity of the operatively upper end including at least 80 mole percent of the first chemical composition and less than 20 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 80 mole percent of the second chemical composition and less than 20 mole percent of the first chemical composition;

- the working liquid in proximity of the operatively upper end including at least 90 mole percent of the first chemical composition and less than 10 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 90 mole percent of the second chemical composition and less than 10 mole percent of the first chemical composition; and

- the working liquid in proximity of the operatively upper end including at least 95 mole percent of the first chemical composition and less than 5 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 95 mole percent of the second chemical composition and less than 5 mole percent of the first chemical composition.

The method may include the further step of additionally heating by means of a second heat source the first stream of compressed working liquid to produce a first stream of heated working fluid.

Alternatively, the method may include the further steps of:

- relaying a portion of the first stream of compressed working liquid, as a second stream of compressed working liquid;

- heating, by means of a second heat source, the second stream of compressed working liquid to produce a second stream of heated working vapour; and

- introducing the second stream of heated working vapour to the working liquid in the first reactor to thereby heat the working liquid. The second heat source may be an external heat source. The method may also include the further steps of relaying a portion of the first stream of heated working vapour, as a second stream of heated working vapour, and utilising the second stream of heated working vapour to compress the first stream of working vapour.

According to an example embodiment of the invention, the method may further include the steps of:

- extracting working liquid, as a second stream of working liquid, from the first reactor; and

- reducing the pressure of the second stream to produce a first stream of reduced pressure working liquid; and

- feeding the first stream of reduced pressure working liquid to the second reactor in order to augment the working liquid inside the second reactor.

According to a second aspect of the invention, there is provided a system for regeneratively utilising heat in a thermodynamic cycle, the thermodynamic cycle utilising a working liquid and working vapour, each including a binary mixture containing a first chemical composition and a second chemical composition, the first chemical composition having a lower boiling point temperature than the second chemical composition, the system comprising:

- a first reactor having an operatively upper end and an operatively lower end and including working liquid and working vapour therein;

- a first compressor device, in fluid flow communication with the first reactor, for receiving working vapour, as a first stream of working vapour, from the first reactor and compressing the received first stream of working vapour to produce a first stream of compressed working vapour, the first compressor device being in further fluid flow communication with the first reactor for introducing the first stream of compressed working vapour to the working liquid in the first reactor for absorption by the working liquid to thereby heat the working liquid;

- a second compressor device, in fluid flow communication with the first reactor, for receiving working liquid, as a first stream of working liquid, from the first reactor and compressing the received first stream of working liquid to produce a first stream of compressed working liquid;

- a first heat exchange element, in fluid flow communication with the second compressor device, for receiving the first stream of compressed working liquid and transferring heat thereto that is received from a first heat source, being in the form of a body of working liquid, to produce a first stream of heated working vapour; and

- an expansion device, in fluid flow communication with the first heat exchange element, for receiving and expanding the first stream of heated working vapour to obtain usable energy and produce a first stream of exhaust working vapour, the expansion device being in further fluid flow communication with the body of working liquid for introducing the first stream of exhaust working vapour to the body of working liquid for absorption by the body of working liquid to thereby heat it. The working vapour in the first reactor may be in communication with and located operatively above the working liquid in the first reactor. The working vapour in the first reactor may be present only in proximity of the operatively upper end thereof. There is provided for the body of working liquid to be located in and form part of the working liquid in the first reactor. Alternatively, the body of working liquid may be located in a second reactor.

The first heat exchange element may be located inside the first reactor. Alternatively, the first heat exchange element may be located inside a second reactor.

The first stream of exhaust working vapour may be introduced in the proximity of the lower end of the first reactor. Alternatively, the first stream of exhaust working vapour may be introduced in the proximity of an operatively lower end of the second reactor. The first reactor may have a temperature gradient from its operatively upper end to its operatively lower end, wherein the temperature increases in an operatively downwardly direction. According to example embodiments of the invention, there may be a temperature difference between the operatively upper and lower ends being any one of:

- at least 25 degrees Celsius;

- at least 50 degrees Celsius;

- at least 75 degrees Celsius; and

- at least 100 degrees Celsius.

The introduction of the first stream of compressed working vapour to the working liquid in the first reactor may assist in maintaining the temperature gradient over the first reactor.

The first reactor may have a concentration gradient of the first chemical composition relative to the second chemical composition from its operatively upper end to its operatively lower end, wherein the concentration of the first chemical composition relative to the second chemical composition increases in an operatively upwardly direction. Similarly, the concentration of the first chemical composition relative to the second chemical composition decreases in an operatively downwardly direction.

According to example embodiments of the invention, working liquid in proximity of the operatively upper end and working liquid in proximity of the operatively lower end may respectively include any one of the following concentration distributions: - the working liquid in proximity of the operatively upper end including at least 70 mole percent of the first chemical composition and less than 30 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 70 mole percent of the second chemical composition and less than 30 mole percent of the first chemical composition;

- the working liquid in proximity of the operatively upper end including at least 95 mole percent of the first chemical composition and less than 5 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 95 mole percent of the second chemical composition and less than 5 mole percent of the first chemical composition. There is further provided for the system to include a second heat exchange element, in fluid flow communication with the second compressor device, for receiving the first stream of compressed working liquid and transferring heat thereto that is received from a second heat source to produce a first stream of heated working fluid. The second heat source may be an external heat source.

Alternatively, there is provided for the system to include a second heat exchange element, in fluid flow communication with the second compressor device, for receiving a portion of the first stream of compressed working liquid, as a second stream of compressed working liquid and transferring heat thereto that is received from a second heat source to produce a first stream of heated working vapour, the second heat exchange element being in further fluid flow communication with the first reactor for introducing the first stream of heated working vapour to the working liquid in the first reactor to thereby heat it.

A portion of the first stream of heated working vapour may be relayed, as a second stream of heated working vapour, and utilised to drive the first compressor device.

According to a further example embodiment of the invention, the system may include a first pressure reducer device that is in fluid flow communication with the first reactor for receiving working liquid, as a second stream of working liquid, from the first reactor, reducing the pressure of the second stream to produce a first stream of reduced pressure working liquid, the first pressure reducer device being in further fluid flow communication with the second reactor for introducing the first stream of reduced pressure working liquid to the second reactor in order to augment the working liquid inside the second reactor. After vapour absorption, this augmented working liquid is transferred back from the second reactor, via a flooded (or liquid ring) expansion device that pressurise it, to the first reactor. These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention are described below, by way of non-limiting examples only, and with reference to the accompanying figures wherein: figure 1 is a schematic block and line diagram illustrating the arrangement of the main components of a system for regeneratively utilising heat in a thermodynamic cycle in accordance with a first embodiment of the invention; figure 2 is a schematic block and line diagram illustrating the arrangement of the main components of a system for regeneratively utilising heat in a thermodynamic cycle in accordance with a second embodiment of the invention; figure 3 is a schematic axial cross-section view of a first reactor forming part of the system of figure 2; figure 4 is a schematic axial cross-section view of a second reactor forming part of the system of figure 2; figure 5a is a schematic radial cross-section view of an expansion device forming part of the system of figure 2; and figure 5b is a schematic axial cross-section view of the expansion device of figure 5a. DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, a system for regeneratively utilising heat in a thermodynamic cycle in accordance with a first embodiment of the invention is generally indicated by reference numeral 100 in figure 1 , and a system for regeneratively utilising heat in a thermodynamic cycle in accordance with a second embodiment of the invention is generally indicated by reference numeral 200 in figure 2.

The thermodynamic cycle utilises a working liquid and a working vapour, each including a binary mixture that contains a first chemical composition and a second chemical composition. The first chemical composition has a lower boiling point temperature than the second chemical composition and is able to dissolve into the second chemical composition in an exothermic process. According to this example embodiment, the first chemical composition comprises ammonia (Nhh) and the second chemical composition comprises water (H2O). However, in other embodiments of the invention, the chemical compositions could comprise any two chemical compositions which fulfil the above criteria such as, for example, Lithium bromide (LiBr) and water, Carbon dioxide (CO2) and water, and the like. It is to be noted that at various positions in the systems 100, 200 the relative ratios between the respective chemical compositions differ and may even comprise only one of the chemical compositions at some locations.

The system 100 comprises a first reactor 102 that includes working liquid 104 and working vapour 106. The first reactor 102 has an operatively upper end 108 in the proximity of which the working vapour 106 is present and an opposing operatively lower end 1 10 in the proximity of which the working liquid 104 is present.

The working vapour 106 is in communication with and located operatively above the working liquid 104. As illustrated, according to this example embodiment, the working liquid 104 occupies a significantly larger volume in the first reactor 102, with the working vapour 106 being present only in proximity of the operatively upper end 108. Furthermore, the working liquid 104 is present from the lower end 1 10 to the proximity of the upper end 108. The first reactor 102 has a concentration gradient of the first chemical composition relative to the second chemical composition from its operatively upper end 108 to its operatively lower end 1 10, wherein the concentration of the first chemical composition relative to the second chemical composition increases in an operatively upwardly direction. Similarly, the concentration of the first chemical composition relative to the second chemical composition decreases in an operatively downwardly direction. According to a preferred embodiment of the invention, working liquid 104 in proximity of the operatively upper end 108 includes at least 95 mole percent of the first chemical composition and less than 5 mole percent of the second chemical composition. Similarly, working liquid 104 in proximity of the operatively lower end 1 10 includes at least 95 mole percent of the second chemical composition and less than 5 mole percent of the first chemical composition.

In further example embodiments of the inventions, and depending on the operating parameters such as the working media used and pressures and temperatures at which the system 100 is operated at, these values could, for example, respectively include:

- the working liquid 104 in proximity of the operatively upper end 108 including at least 70 mole percent of the first chemical composition and less than 30 mole percent of the second chemical composition, with the working liquid 104 in proximity of the operatively lower end 1 10 including at least 70 mole percent of the second chemical composition and less than 30 mole percent of the first chemical composition;

- the working liquid 104 in proximity of the operatively upper end 108 including at least 80 mole percent of the first chemical composition and less than 20 mole percent of the second chemical composition, with the working liquid 104 in proximity of the operatively lower end 1 10 including at least 80 mole percent of the second chemical composition and less than 20 mole percent of the first chemical composition; and

- the working liquid 104 in proximity of the operatively upper end 108 including at least 90 mole percent of the first chemical composition and less than 10 mole percent of the second chemical composition, with the working liquid 104 in proximity of the operatively lower end 1 10 including at least 90 mole percent of the second chemical composition and less than 10 mole percent of the first chemical composition.

The first reactor 102 furthermore has a temperature gradient from its operatively upper end 108 to its operatively lower end 1 10, wherein the temperature of the working liquid 104 increases in an operatively downwardly direction. The working liquid 104 in proximity of the operatively upper end 108 is maintained at a lower temperature relative to the working liquid in proximity of the operatively lower end 1 10. According to a preferred embodiment of the invention, the temperature difference is in excess of 100 degrees Celsius.

In further example embodiments of the inventions, and depending on the operating parameters such as the working media used and pressures at which the system 100 is operated at, the temperature difference could, for example, include:

- at least 25 degrees Celsius;

- at least 50 degrees Celsius; and

- at least 75 degrees Celsius.

Further in accordance with the system 100, a first compressor device 1 12 is in fluid flow communication with the first reactor 102 to receive working vapour, as a first stream of working vapour 1 14, from the first reactor 102 and compress it in order to produce a first stream of compressed working vapour 1 1 6. The first stream of working vapour 1 14 is extracted from the proximity of the upper end 108 of the first

The first compressor device 1 12 is further fluid flow communication with, preferably, the operatively lower end 1 10 of the first reactor 102, in order to introduce the first stream of compressed working vapour 1 16 to the working liquid 104 in the first reactor 102. The first stream of compressed working vapour 1 16 is thus introduced in the proximity of the lower end 1 10 of the first reactor 102. After being introduced, the compressed working vapour 1 16 is absorbed by the working liquid 104, which absorption heats the working liquid 104, specifically the working liquid 104 being positioned in the lower end 1 10. The extraction of the first stream of colder working vapour 1 14 from the upper end 108 and introduction of the first stream of compressed working vapour 1 16 at the lower end 1 10 assists in maintaining the temperature gradient across the first reactor 102.

A second compressor device 1 1 8 is in fluid flow communication with the first reactor 102 to receive working liquid, a first stream of working liquid 120, from the first reactor 102 and compress it in order to produce a first stream of compressed working liquid 122. The first stream of working liquid 120 is extracted from the proximity of the upper end 108 of the first reactor 1 02. A motor 124 could, for example, be utilised to drive the second compressor device 1 18.

A first heat exchange element 126 is in fluid flow communication with the second compressor device 1 18 to receive the first stream of compressed working liquid 122 from the compressor device 1 18. The first heat exchange element 126 transfers heat, that is received from a first heat source, being in the form of a body of working liquid, to the first stream of compressed working liquid 122 in order to produce a first stream of heated working vapour 128. In this example embodiment, the first heat exchange element 126 is located inside the first reactor 102 and receives heat from the working liquid 104 that, in turn, is being used to heat and evaporate the received first stream of compressed working liquid 122. As such, the body of working liquid is located in the first reactor 102 and comprises the working liquid 104 that is located inside it. An expansion device 130 is in fluid flow communication with the first heat exchange element 126 to receive the first stream of heated working vapour 128 and expand it to obtain usable energy and produce a first stream of exhaust working vapour 132. The heated working vapour 128 that expands in the expansion device 130 could drive a generator 134, that is being connected to the device 130, to generate electricity.

The expansion device 130, being in the example embodiment in the form of a standard isentropic turbine, is further in fluid flow communication with the body of working liquid, in this example embodiment being the working liquid 104 that is inside the first reactor 102 in order to introduce the first stream of exhaust working vapour 132 to the working liquid 104 inside the first reactor 102.

The first stream of exhaust working vapour 132 is introduced in the proximity of the lower end 1 10 of the first reactor 102. When introduced, the exhaust working vapour 132 is absorbed by the working liquid 104 inside the first reactor 102 to thereby heat it that, in turn, is again being used to heat, evaporate and superheat the first stream of compressed working liquid 122.

As indicated, a portion of the first stream of heated working vapour 128 is relayed, as a second stream of heated working vapour 136, and utilised to drive the first compressor device 1 12.

The system 100 further includes a second heat exchange element 138 that is located in-between and in fluid flow communication with the second compressor device 1 18 and the first heating element 126. The second heat exchange element 138 receives the first stream of compressed working liquid 122 and transfers heat thereto, that is received from a second heat source 140, being in the form of an external heat source, to produce a first stream of heated working fluid 142. The first stream of heated working fluid 142 is subsequently fed to and received by the first heat exchange element 126 that produces the first stream of heated working vapour 128.

In this example embodiment, a third heat exchange element 144 is in fluid flow communication with the first heat exchange element 126 to receive and super heat the first stream of heated working vapour 128 before it enters the expansion device 130. The third heat exchange element 144 is shown to be located inside the first reactor 102 and receives heat from the working liquid 104 that, in turn, is being used to superheat the received first stream of heated working vapour 128. Turning to figure 2, similar to as described above in relation to the system 100, the system 200 comprises a first reactor 202 that includes working liquid 204 and working vapour 206. The first reactor 202 has an operatively upper end 208 in the proximity of which the working vapour 206 is present and an opposing operatively lower end 210 in the proximity of which the working liquid 204 is present.

Again, according to this example embodiment, the working vapour 206 is in communication with and located operatively above the working liquid 204 and the working liquid 204 occupies a significantly larger volume in the first reactor 202, with the working vapour 206 being present only in proximity of the operatively upper end 208. Furthermore, the working liquid 204 is present from the lower end 210 to the proximity of the upper end 208.

The first reactor 202 also has a concentration gradient of the first chemical composition relative to the second chemical composition from its operatively upper end 208 to its operatively lower end 210, wherein the concentration of the first chemical composition relative to the second chemical composition increases in an operatively upwardly direction. Similarly, the concentration of the first chemical composition relative to the second chemical composition decreases in an operatively downwardly direction. According to a preferred embodiment of the invention, working liquid 204 in proximity of the operatively upper end 208 includes at least 95 mole percent of the first chemical composition and less than 5 mole percent of the second chemical composition. Similarly, working liquid 204 in proximity of the operatively lower end 210 includes at least 95 mole percent of the second chemical composition and less than 5 mole percent of the first chemical composition. In further example embodiments of the inventions, and depending on the operating parameters such as the working media used and pressures and temperatures at which the system 200 is operated at, these values could, for example, respectively include:

- the working liquid 204 in proximity of the operatively upper end 208 including at least 70 mole percent of the first chemical composition and less than 30 mole percent of the second chemical composition, with the working liquid 204 in proximity of the operatively lower end 210 including at least 70 mole percent of the second chemical composition and less than 30 mole percent of the first chemical composition;

- the working liquid 204 in proximity of the operatively upper end 208 including at least 80 mole percent of the first chemical composition and less than 20 mole percent of the second chemical composition, with the working liquid 204 in proximity of the operatively lower end 210 including at least 80 mole percent of the second chemical composition and less than 20 mole percent of the first chemical composition; and

- the working liquid 204 in proximity of the operatively upper end 208 including at least 90 mole percent of the first chemical composition and less than 10 mole percent of the second chemical composition, with the working liquid 204 in proximity of the operatively lower end 210 including at least 90 mole percent of the second chemical composition and less than 10 mole percent of the first chemical composition. The first reactor 202 furthermore has a temperature gradient from its operatively upper end 208 to its operatively lower end 210, wherein the temperature of the working liquid 204 increases in an operatively downwardly direction. The working liquid 204 in proximity of the operatively upper end 208 is maintained at a lower temperature relative to the working liquid in proximity of the operatively lower end 210. According to a preferred embodiment of the invention, the temperature difference is in excess of 100 degrees Celsius.

In further example embodiments of the inventions, and depending on the operating parameters such as the working media used and pressures at which the system 200 is operated at, the temperature difference could, for example, include:

- at least 25 degrees Celsius;

- at least 50 degrees Celsius; and

- at least 75 degrees Celsius.

Further in accordance with the system 200, a first compressor device 212 is in fluid flow communication with the first reactor 202 to receive working vapour, as a first stream of working vapour 214, from the first reactor 202 and compress it in order to produce a first stream of compressed working vapour 216. The first stream of working vapour 214 is extracted from the proximity of the upper end 208 of the first reactor 202. A motor 218 could, for example, be utilised to drive the first compressor device 212.

The first compressor device 212 is further fluid flow communication with, preferably, the operatively lower end 210 of the first reactor 202, in order to introduce the first stream of compressed working vapour 216 to the working liquid 204 in the first reactor 202. The first stream of compressed working vapour 216 is thus introduced in the proximity of the lower end 210 of the first reactor 202. After being introduced, the compressed working vapour 216 is absorbed by the working liquid 204, which absorption heats the working liquid 204, specifically the working liquid 204 being positioned in the lower end 210. The extraction of the first stream of colder working vapour 214 from the upper end 208 and introduction of the first stream of compressed working vapour 216 at the lower end 210 assists in maintaining the temperature gradient across the first reactor 202.

A second compressor device 220 is in fluid flow communication with the first reactor 202 to receive working liquid, a first stream of working liquid 222, from the first reactor 202 and compress it in order to produce a first stream of compressed working liquid 224. The first stream of working liquid 222 is extracted from the proximity of the upper end 208 of the first reactor 202. A second stream of working vapour 226 is extracted from the proximity of the upper end 208 of the first reactor 202 and utilised to drive the second compressor device 220.

A first heat exchange element 228 is in fluid flow communication with the second compressor device 220 to receive the first stream of compressed working liquid 224 from the compressor device 220. The first heat exchange element 228 transfers heat, that is received from a first heat source, being in the form of a body of working liquid 230, to the first stream of compressed working liquid 224 in order to produce a first stream of heated working vapour 232. In this example embodiment, the first heat exchange element 228 is located inside a second reactor 234 and receives heat from the body of working liquid 230 that, in turn, is being used to heat and evaporate the received first stream of compressed working liquid 224. As such, the body of working liquid 230 is at least partially located in the second reactor 234. A first stream of exhaust working vapour 236 exiting the second compressor device 220 is subsequently fed to the second reactor 234 to heat the body of working liquid 230 upon being absorbed by the body of working liquid 230.

An expansion device 238 is in fluid flow communication with the first heat exchange element 228 to receive the first stream of heated working vapour 232 and expand it to obtain usable energy and produce a second stream of exhaust working vapour 240. The heated working vapour 232 that expands in the expansion device 238 could drive a generator 242, that is being connected to the device 238, to generate electricity.

The expansion device 238 is further in fluid flow communication with the body of working liquid 230, in this example embodiment being the working liquid that is inside the second reactor 234 in order to introduce the second stream of exhaust working vapour 240 to the body of working liquid 230. The second stream of exhaust working vapour 240 is introduced in the proximity of an operatively lower end 244 of the second reactor 234. When introduced, the exhaust working vapour 240 is absorbed by the working liquid 230 inside the second reactor 234 to thereby heat it that, in turn, is again being used to heat and evaporate the first stream of compressed working liquid 224. The expansion device 238 is further in fluid flow communication with the second reactor 234 it receives from it heated working liquid, as a first stream of heated working liquid 246, extracts heat there from, and discharges it as a second stream of working liquid 248. The expansion device 238 is further in fluid flow communication with the first reactor 202, whereby the second stream of working liquid 248, discharged from the expansion device 238, is fed to the first reactor 202 where it joins and mixes with the working liquid 204 in it.

The system 200 further includes a second heat exchange element 250 that is in fluid flow communication with the second compressor device 220. The second heat exchange element 250 receives a portion of the first stream of compressed working liquid 224, as a second stream of compressed working liquid 252, and transfers heat thereto, that is received from a second heat source 254, being in the form of an external heat source, to produce a second stream of heated working vapour 256. The second heat exchange element 250 is in further fluid flow communication with the first reactor 202 to introduce the second stream of heated working vapour 256 to the working liquid 204 in the first reactor 202 to thereby heat it.

The system 200 also includes a first pressure reducer device 258 that is in fluid flow communication with the first reactor 202 to receive from the first reactor 202 working liquid, that passes through a third heat exchange element 260 in the first reactor 202, as a third stream of working liquid 262. The pressure reducer device 258 reduces the pressure of the third stream of working liquid 262 to produce a first stream of reduced pressure working liquid 264. The first pressure reducer device 258 is further fluid flow communication with the second reactor 234 to introduce the first stream of reduced pressure working liquid 264 to the second reactor 234 in order to transfer heat to working liquid 230 inside the second reactor 234.

In the further description of an example embodiment of the invention that follows, characteristics and values, as obtained though calculations, are included merely for purposes in providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention and not to limit the scope of the invention to such precise details. Turning to figure 3, the first reactor 202, in the form of a regenerative desorber, is a vertical, gravity, density differentiation liquid filled distillation reactor column with a temperature gradient from the operatively upper end 208 to the operatively lower end 210, as explain previously. The bottom 210 is maintained at an elevated temperature, being about the critical temperature of Nhte, at about 4 Bar absolute, in order to desorb most of the Nhte to a weak mixture of only a few percent NH3 in water, while the reactor top 208 is maintained at about 0°C, in order to provide near pure NH3 liquid at a pressure of about 4 Bar absolute. As stated previously, the reactor 202 contains working liquid 204 and working vapour 206. The second stream of working liquid 248, comprising a mixture of NH3 and water of which about 25% is NH3, is fed into the reactor through a first liquid inlet 310 at intermediate pressure of about 4 Bar absolute. Due to a density difference with the working liquid 204 inside the reactor 202, being a saturated mixture, the working liquid 248 migrates downwardly to the hotter bottom 210. As it is gradually heated up by direct contact heat exchange while moving down, some NH3 is desorbed, or boiled off. This continues until it reaches the bottom 210 at about 5% NH3 in water at 132°C. This weak ammonia solution present at the bottom 210, comprising a lean mixture of NH3 and water of which about 5% is NH3, then enters an opening 312 of the third heat exchange element 260, flows upwards in the element 260, and regeneratively heats the saturated mixture 204 in the reactor 202. Similarly, the lean mixture cools down as it flows upwards in the element 260 to the low designed temperature of the reactor column top 208, being about 0 °C, and leaves the reactor 202 close to the top 208 through a first liquid outlet 314 at a temperature of about 16°C.

Boiled-off NH3 vapour bubbles 316 rise upwards, but are re-absorbed as they flow into colder sections of the reactor 202, with the corresponding heat of solution heating up the saturated mixture 204 at the point of absorption. The lower density of pure (liquid) ammonia and very rich mixtures of NH3 in water gradually migrate upwards to leave the reactor 202 through a second liquid outlet 317 as (almost) pure NH3 liquid at the cold top 208 at about 0°C as the first stream of working liquid 222.

Additional heat, apart from the regenerative heat recovered from the cooling weak NH3 in water solution flowing upwards inside the heat exchange element 260, is provided for in this distillation process (desorption) and to maintain the temperature gradient over the reactor 202. Such additional heat is provided by the compressor 212 (refer to figure 2), by it extracting vapour 214 from the cold top 208 of the reactor 202 through a first vapour outlet 318, at about 0 °C and about 4 Bar absolute pressure, and supplying it to the hot bottom 210 through a first vapour inlet 320 in the form of the first stream of compressed working vapour 216, being compressed vapour bubbles of (almost) pure NH3, at about 3 °C and about 4.5 Bar absolute pressure. Further additional heat is provided by the second stream of heated working vapour 256 being compressed vapour bubbles of (almost) pure NH3, at about 3 °C and about 4.5 Bar absolute pressure, which is supplied to the hot bottom 210 through a second vapour inlet 322. It is envisaged that the reactor 202 could delay vapour bubbles from rising too quick by, for example, utilising stainless steel wool or similar packing, to ensure slow liquid and vapour flow for proper direct contact heat exchange. This way the heat of solution generates a local rise in temperature created by dissolving vapour bubbles, ensuring a uniform temperature gradient from the bottom 210 to the top 208 of the reactor 202.

Referring to figure 4, the second reactor 234, in the form of a pressure independent vapour absorber, receives the first stream of compressed working liquid 224 through a first liquid inlet 410, at about 0 °C and about 16 Bar absolute pressure and permits the liquid 224 to pass through a first heating element 228, which is shaped in the form of a coil. The second reactor 234 further receives the first stream of reduced pressure working liquid 264 through a second liquid inlet 412, at about 16 °C and about 1 Bar absolute pressure and permits the liquid 264 to pass around the heating element 228, as shown. The fully second stream of exhaust working vapour 240, at about 38 °C and about 1 Bar absolute pressure and the first stream of exhaust working vapour 236, at about 33 °C and about 1 Bar absolute pressure, are received by a first vapour inlet 414, in proximity of the second liquid inlet 412.

The second stream of exhaust working vapour 240, combined with the first stream of exhaust working vapour 236 comprising of (almost) pure NH3, are introduced into and easily absorbed by the first stream of reduced pressure working liquid 264, being a weak ammonia solution, causing the first stream of reduced pressure working liquid 264to be heated as a result of the heat of solution as well as the latent heat in the vapour 236 and 240.

As a result, the first stream of compressed working liquid 224 is regeneratively heated by the first stream of reduced pressure working liquid as it flows through the element 228, causing it to flash into vapour, being the first stream of heated working vapour 232, that leaves the reactor 234 through a first liquid outlet 416, at about 38 °C and about 15 Bar absolute pressure. As a result, the latent heat as well as the heat of solution of the second stream of exhaust vapour 240 combined with the first stream of exhaust working vapour 236 are used to heat the first stream of compressed working liquid 224. The first stream of heated working liquid 246 leaves the reactor 234 through a second liquid outlet 418, at about 42 °C and about 1 Bar absolute pressure.

By using the reactor 234, where the Nhte vapour is easily absorbed into a weak solution of NH3 in water at a constant low pressure, makes waste heat recovery possible with the heat exchange element 228 for heat removal inside the reactor 234. The heat of solution of the vapour into a low concentration NH3 in water solution (the process of NH3 vapour dissolving into the aqueous solution is exothermic) heats the solution to higher temperatures with only minimal rise in the absorber pressure, by design to an outlet temperature above the required evaporation temperature of the primary high pressure pure NH3 liquid, therefore recovering the latent heat in the vapour (and heat of solution) leaving the expansion device exhaust, and using it regeneratively to heat and evaporate the high pressure fluid to power the expansion device 238. This NH3 vapour dissolving process also increases the mass NH3 in solution in the absorber to a higher concentration. Virtually no heat is therefore rejected from the cycle, and part of the recovered heat is provided to power the expansion device 238, while the balance is routed to a heat of solution powered, heat pump driven regenerative reactor 202 to reclaim pure NH3. The absorber 234 is thus a heat recovery unit for the expansion device 238.

Turning to figures 5a and 5b, the expansion device 238, in the form of a liquid ring turbine, includes a stationary casing 510, a free-wheeling first rotor 512 rotatably mounted inside the casing 510, and a second rotor 514 rotatably mounted off-centre inside the first rotor 512 as well as the casing 510. The one axial side of the second rotor 514 is connected via a power shaft to the external generator 242. A first vapour inlet 516 is provided that extends through the casing 510 and first rotor 512 and into the second rotor 514 on the opposing axial side as the power shaft. The first vapour inlet 516 includes, at a first end thereof, a vapour inlet opening 518 through which the first stream of heated working vapour 232 is received, at about 38 °C and about 15 Bar absolute pressure, and, at an opposing second end thereof, an inlet housing 520 or hub in fluid flow communication with the inlet opening 518. The inlet housing 520 define at least one vapour discharge ports 522 (radial valve openings) through which the first stream of heated working vapour 232 exits the inlet 516 in a radial outward direction. The port 522 is in fluid flow communication with the vapour inlet opening 518 by means of a bore 524 defined in the housing 520. The second rotor 514 includes a cylindrically-shaped inner wall 526 which abuts against the inlet housing 520, axially spaced opposing disc-shaped end walls 528 extending radially outwardly from opposing ends of the inner wall 526, and a plurality of radially spaced curved compartment separators, vanes or blades 530 extending radially from the inner wall 526 and between the opposing end walls 528 so to define the plurality of radially-spaced compartments 532 between the inner wall 526, end walls 528 and adjacent vanes 530. It should be appreciated that the second rotor 514 could include any number of compartments 532. The inner wall 526 has an inner diameter fitting closely over the inlet housing 520 but still permitting it to rotate around the inlet housing 520, in use. The inner wall 526 portion of each compartment 532 includes at least one vapour inlet port 534 for receiving the first stream of heated working vapour 232 from the at least one vapour discharge ports 522, when they are in registration with each other.

The first rotor 512 includes a cylindrically-shaped rotor housing having closed axial ends. In use, the first rotor 512 includes a liquid ring 536 against an inner periphery thereof that is rotatably movable with the first rotor 512. The arrangement is such that as the second rotor 514 rotates 538, liquid of the liquid ring 536 sequentially fills the compartments 532 (almost) completely at a specific rotation angle. The backswept blades 530 leave the liquid ring 536 for a few degrees at the opposite side of the rotor 514, forming an exhaust port that allows trapped low pressure vapour to escape from the compartments 532 and exit the expansion device 238 through a first vapour outlet 540 as the second stream of exhaust working vapour 240, at about 36 °C and about 1 Bar absolute pressure.

The expansion device 238 further includes a first liquid inlet 542 for receiving the first stream of heated working liquid 246, at about 42 °C and about 1 Bar absolute pressure, and adding it to the liquid ring 536. At the correct radial distance from the rotation centre, an overflow opening is provided in the first rotor 512 to discharge excess liquid out of the first rotor 512, flowing radially outward along the side of the rotor 512 and exiting the stationary casing 510 via a first liquid outlet 544 provided in a side of the casing 510 as the second stream of working liquid 248, at about 36 °C and about 4 Bar absolute pressure. This keeps the liquid ring mass constant in the first rotor 512, regardless of rotation speed or pressures and heated liquid continuously washes through the expansion device 238. As such, the expansion device 238 includes a second rotor 514 with backswept blades 530 and both axial ends closed with end plates. The inner periphery of the first rotor 512 has a liquid ring 536 formed by the centrifugal force of the strong Nhte in water solution continuously filling the rotor with liquid via inlet 542 in the side of the casing 510.

High pressure NH3 vapour present in the inlet 516 coupled to the stationary central inlet valve of the second rotor 514 is injected by ports 522 and 534, rotating into registration with each other, into the second rotor 514 at a point where the specific chamber 532 is completely filled with liquid of the liquid ring 536. The high pressure vapour expands in the chamber 532, forcing the liquid 536 out radially (swept backwards with the blades) while putting a reaction torque on the second rotor 514, delivering rotation power to it, and thus to the generator 242 via the power shaft.

The liquid exiting the turbine chamber 532 into the liquid ring 536, retains some kinetic energy as it is thrusted outwards by the expanding vapour inside the chamber 532, speeding up to drive out all remaining vapour on the low-pressure side of the rotor 514, but also providing impulse power to the rotor 514, delivering more power to it. Only a small portion of the expanding vapour is absorbed in the liquid ring 536, even though the contact time of vapour to liquid is only a few milliseconds, making the NH3 in water mixture stronger by a few percent, for example 25% NH3 in water (as opposed to the inlet 23% NH3 in water), before leaving the expansion device 238. At the same time some heat of the liquid ring 536 is added to the isentropically expanding and cooling vapour to re-heat it, simulating an expander closer to isothermal than isentropic, with the resulting higher power output per mass NH3 vapour expanded and vapour outlet temperature closer to the input temperature.

Power is thus generated by expanding a high pressure NH3 vapour to lower pressure in expansion device 238, delivering rotational power to a shaft, turning the generator 242 in this embodiment as per Figure 2.

The expansion device 238 could be an isentropic expansion turbine, but the high- pressure differential makes the percentage liquid droplets in the exhaust low pressure vapour quite high (e.g. some 12% or more) with the corresponding lower power output resulting from it. Isentropic expansion also lowers the low pressure vapour outlet temperature substantially, making heat recovery difficult. Using an expander not affected by liquid in the vapour, like the liquid piston device as described, or a dense fluid expander like a flooded positive displacement vapour expansion device like a Chisholm screw or scroll expander would provide higher power output for the same mass vapour expanded. Also, using quasi-isothermal expansion guarantees higher expander outlet temperatures, better suited to the required heat recovery.

The simplified expander 130 used in the embodi ment of Figure 1 , use a standard isentropic turbine manufactured for organic rankine cycles, and the reactor 102 in figure 1 therefore has an additional heat exchanger 144 to superheat the NH3 vapour, to guarantee no vapour condenses into damaging liquid droplets while expanding isentropically. This is recommended for larger utility-scale systems, while the positive displacement type expanders would be more suitable for use in smaller applications.

As the complete desorption process of removing Nhte from the solution of NH3 in water is endothermic, additional heat is required in the reactor 202 for the heat balance around the full cycle (Hess's law) and this heat is extracted from the environment by allowing a small percentage liquid NH3 produced by the reactor 202 to flash in the second heat exchanger 250 that is in contact with the environment or waste heat source 254. The NH3 flashing takes place at the reactor 202 low temperature (in this example 3°C) so heat 254 is extracted from the environment at this low temperature to drive the system 200, in the form of a power cycle. The flashed vapour may be added to the reactor bottom 210 directly. With the compressor 218 mass NH3 flow the same as the power expansion device 238 mass NH3 flow (to ensure a small percentage vapour flow through the reactor 202 from bottom 210 to the top 208 without being absorbed to guarantee vapour everywhere in the reactor 202 where heat is needed), heat balance prove this additional heat load to be the same amount of energy as delivered by the power expansion device 238, minus the energy required to drive the compressor 218 as well as the compressor 220.

By using high pressure NH3 vapour to power the pump 220 directly (like in this example of Figure 2), as well as power the heat pump compression process by way of a vapour jet compressor (like in the example of Figure 1 ), the advantage of using less electricity from the developed power is offset by the requirement of the cycle to produce much more high pressure vapour which does not flow through a turbine for developing power, making the overall cycle efficiency slightly lower, but it may be practical under certain large-scale conditions.

The systems 100 and 200 are basically Organic Rankine Cycles (ORC) integrated with absorption heat recovery and vapour heat of solution powered regenerative desorption steps utilising the heat of solution / dissolution of binary media fluids into one another. In this example implementation we make use of ammonia and water solutions as the binary media fluids, although any two media where one dissolves into the other in an exothermic process may be used.

The systems 100 and 200 make use of heat transformer principles to elevate the normal heat rejection temperature without increasing the pressure, of a power turbine exhaust vapour to a value higher than the turbine high pressure vapour inlet temperature in order to recover all latent heat and do away with heat rejection. Waste heat absorbed from external sources is also done at a temperature lower than the turbine high pressure vapour inlet temperature by using a heat pump, and no heat is rejected in the desorber as the destruction of entropy is avoided by keeping the desorption process fully heat regenerative, assisted by the heat pump.

The nature of this thermodynamic cycle is also ideally suited to use as energy storage battery, by simply adding three storage reservoirs to the strong and weak NH3 in water solutions, as well as the pure NH3 liquid produced by the desorber. The pure NH3 liquid is produced at 0°C at a pressure of 4.35 Bar absolute, so a cheap way to store it, would be to drop the pressure to 1 Bar absolute, flashing a few percent of the produced liquid to vapour, which will cool the remaining liquid to about -34°C, allowing it to be stored in a thermally insulated accumulator or Dewar at atmospheric pressure, which is cheaper that storing it at elevated pressure, requiring an expensive (and much more safety hazardous) pressure vessel. The desorber may then be operated at a time when cheap electricity (e.g. wind or solar PV renewable energy) with external electricity powering the desorber, is available, effectively storing the electricity in the latent heat of liquid NH3. The power turbine may then use the liquid NH3 to generate electricity at a time when the stored energy is most needed, e.g. when the sun is not shining in the PV installation, or wind not blowing in the wind installation. The added advantage of the charge / discharge efficiency of nearly 800% due to environmental heat being converted to additional power make the storage battery so produced very cheap, allowing the cost of power produced to be only a small fraction of the cost of electricity used for charging. The only negative for using the cycle as an electricity storage device is the large mass of liquids required to store the electricity in.

Using the described regenerative heat of solution thermodynamic cycle, environmental heat available in concentrated form in e.g. pools of water, rivers or the sea at temperatures well above 3°C due to solar and geothermal actions, may be utilised to produce electricity at very low cost, as no fuel cost is applicable, but only the initial capital outlay. Marine vessels may use the cycle to be powered by the thermal energy in the sea, revolutionizing energy use in marine transport.

Even land- and aero transport would benefit greatly by the high heat to power conversion efficiency.

Even though the cycle operates at temperatures below the critical temperature of both the binary components used as media in the cycle, (for the example NH3 in water binary cycle, the turbine inlet temperature would be lower than about 80°C) the high heat to power conversion efficiency of and the simplicity of the thermodynamic cycle components guarantee an energy revolution, as cost savings for energy users using different implementation solutions are only limited by our imagination.

For example, should a 3-meter-high vertical tube be filled with a mixture of NH3 in aqua and kept at a constant pressure of 200 kPa abs, we will find the following: We may call this tube the bubble heated reactor, forming the heart of the cycle. Due to the liquid column gravity pressure, the column bottom should be about 223.5 kPa abs, as the average density of 800 kg/m3 with a 3m hydraulic height would generate a 23.5 kPa differential pressure. We note that saturated (at different temperatures) solutions of NH3 in water at a constant vapour pressure of 200 kPa absolute have the following known characteristics:

Table 1

At the constant pressure of 200 kPa Absolute noted in Table 1 above, the NH3 concentration has an inverted proportional relation to both the solution specific density and its specific saturation temperature. This has the consequence that if you apply heat to any section of the tube filled with a saturated mixture of ammonia in aqua, some vapour is boiled off immediately, rising upwards in the column as bubbles, to be absorbed again higher up in the column, while the heated, now leaner remaining solution have a greater density and higher temperature, and would therefore migrate downwards, displacing liquid with lower density. This has the effect that heat added anywhere along the length of vertical column, would gradually establish both a temperature gradient with the highest temperature trapped at the bottom of the column, as well as a NH3 concentration gradient with the highest concentration at the top of the column. These gradients would be maintained with the complete column being saturated at all level sections (but at different temperatures of course) as long as the heat addition continues, but conduction (and radiation) heat leakage from the hot bottom to the cold top of the reactor and NH3 concentration dispersion resulting from the natural diffusion of the high NH3 concentration at the top to the low concentration at the bottom, would soon disperse and break up both the concentration and temperature gradients if no heat is continually added to the column.

From the knowledge gained utilizing absorption refrigeration technology, we know that NH3 vapour would be very strongly absorbed in mixtures of NH3 in aqua, only as long as the mixture is sub cooled. With the mixture saturated, no vapour from a rising vapour bubble would diffuse into the surrounding liquid solution, and therefore no heat would be generated as no absorption will take place. Should a NH3 vapour bubble come in contact with a sub cooled section of liquid solution, the direct contact between vapour and liquid would facilitate the quick absorption of the vapour into the liquid, collapsing the bubble and generate absorption heat, consisting of both latent heat of condensation and heat of solution as already discussed when we described the absorber operation.

Introducing the vapour to the bottom of the column into the lean (10% NH3 in aqua) solution will firstly heat the vapour bubble from -1 °C to the liquid temperature of 80°C, using 72 kJ/kg, after which the bubble is absorbed into the sub-cooled hot liquid solution, releasing 1004 kJ/kg of heat to the bottom of the column, raising the temperature back from the sub-cooled 80°C to the saturation 1 10°C. This continuous bubble heating of the bottom of the column quickly establish and maintain both the temperature and concentration gradient, but if heat is not extracted by the submersed heat exchanger coils the column bottom temperature would be raised to the saturation level of 1 10°C with continued bubble absorption. At this temperature the column would be totally in saturation if the pressure is kept constant, so the vapour bubbles would pass through the column to the top without any absorption.

The interface of this thermodynamic cycle to the waste heat input source is the Environmental heat exchanger. We also take note that the Thermodynamic Cycle can extract heat from as low as -30°C if the absorber is kept at 100 kPa absolute, although the extracted heat is added to the thermodynamic cycle at the absorber outlet temperature, which is a few degrees higher, and also, no heat is rejected out of the cycle, meaning that no cooling tower would be required! In this layout the desorber would be operated at 500 - 600 kPa abs and the bottom of the desorber would operate at an elevated temperature of 100°C to 120°C. Note also the two pumps required for this layout, namely the feed pump, providing the high pressure required by the turbine inlet pressure, as well as a desorber mixture pump, providing the circulation of the absorber strong solution liquid to the pressure the desorber operate on.

The flashing vapour extracted from the top of the desorber by the vapour jet injector compressor cool the desorber top down below ambient temperature to some -2°C in this example, establishing the temperature gradient in the desorber of 120°C at the bottom while the top run at -2°C. Heat removed from the desorber bottom by the superheater as well as the recuperator heat exchange tubes provide the necessary sub-cooling to allow heating the desorber bottom by vapour bubble absorption.

The turbine exhaust vapour enters the bottom of the absorber and heat the absorber solution also by vapour bubble absorption. Most of this heat is used regeneratively to heat and evaporate the high-pressure feed pump pressurized liquid NH3 contained in the heat exchange tube inside the absorber, while some excess heat is carried in the strong solution (having absorbed the vapour from the turbine exhaust) which is pumped back to the higher pressure desorber.

A simpler layout of the thermodynamic cycle, where the absorption and desorption functions are done in the heated bottom section and the cooled top section respectively, of a single bubble reactor is sketched in Figure 1 . This layout has the advantage of using less components, like a single high-pressure feed pump, a single liquid-liquid heat exchanger for extracting waste heat input into the cycle from the external waste heat source, as well as the combined reactor, namely the absorber/desorber/superheater/evaporator vapour bubble heated heat exchanger, we call the "bubble reactor" and the normal vapour jet injector compressor as well as an isentropic turbine.

To maintain a constant reactor bottom temperature of 1 1 1 °C, the compressor inlet vapour mass flow is throttled by a valve in the suction line. This regenerative exhaust heat recovery ensures virtually no heat is rejected out of the cycle. It will be appreciated by those skilled in the art that the invention is not limited to the precise details as described herein and that many variations are possible without departing from the scope and spirit of the invention. The description is presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show details of the invention in more detail than is necessary for a fundamental understanding of the invention.

Claims

1 . A method of regeneratively utilising heat in a thermodynamic cycle, the thermodynamic cycle utilising a working liquid and working vapour, each including a binary mixture containing a first chemical composition and a second chemical composition, the first chemical composition having a lower boiling point temperature than the second chemical composition, the method including the steps of:

extracting working vapour, as a first stream of working vapour, from a first reactor having an operatively upper end and an operatively lower end, compressing the first stream of working vapour to produce a first stream of compressed working vapour, and introducing the first stream of compressed working vapour to working liquid in the first reactor whereby the compressed working vapour is absorbed by the working liquid to thereby heat the working liquid;

extracting working liquid, as a first stream of working liquid, from the first reactor, compressing the first stream of working liquid to produce a first stream of compressed working liquid, and heating by means of a first heat source, being in the form of a body of working liquid, the first stream of compressed working liquid to produce a first stream of heated working vapour;

expanding the first stream of heated working vapour to obtain usable energy and produce a first stream of exhaust working vapour; and introducing the first stream of exhaust working vapour to the body of working liquid, whereby the exhaust working vapour is absorbed by the body of working liquid to thereby heat it.

The method according to claim 1 , wherein first reactor is operated wherein the working vapour therein is in communication with and located operatively above the working liquid therein.

The method according to claim 1 or 2, wherein the body of working liquid is located in and forms part of the working liquid in the first reactor.

The method according to claim 1 or 2, wherein the body of working liquid is located in a second reactor.

The method according to any one of the preceding claims, wherein the first reactor is operated to have a temperature gradient from its operatively upper end to its operatively lower end, wherein the temperature increases in an operatively downwardly direction.

The method according to claim 5, wherein there is a temperature difference between the operatively upper and lower ends being any one of:

- at least 25 degrees Celsius;

- at least 50 degrees Celsius;

- at least 75 degrees Celsius; and

- at least 100 degrees Celsius.

The method according to claim 5 or 6, wherein the introduction of the first stream of compressed working vapour to the working liquid in the first reactor assists in maintaining the temperature gradient over the first reactor.

The method according to any one of the preceding claims, wherein the first reactor is operated to have a concentration gradient of the first chemical composition relative to the second chemical composition from its operatively upper end to its operatively lower end, wherein the concentration of the first chemical composition relative to the second chemical composition increases in an operatively upwardly direction, and the concentration of the first chemical composition relative to the second chemical composition decreases in an operatively downwardly direction.

The method according to claim 8, wherein working liquid in proximity of the operatively upper end and working liquid in proximity of the operatively lower end may respectively include any one of the following concentration distributions:

the working liquid in proximity of the operatively upper end including at least 70 mole percent of the first chemical composition and less than 30 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 70 mole percent of the second chemical composition and less than 30 mole percent of the first chemical composition; the working liquid in proximity of the operatively upper end including at least 80 mole percent of the first chemical composition and less than 20 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 80 mole percent of the second chemical composition and less than 20 mole percent of the first chemical composition;

the working liquid in proximity of the operatively upper end including at least 90 mole percent of the first chemical composition and less than 10 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 90 mole percent of the second chemical composition and less than 10 mole percent of the first chemical composition; and

the working liquid in proximity of the operatively upper end including at least 95 mole percent of the first chemical composition and less than 5 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 95 mole percent of the second chemical composition and less than 5 mole percent of the first chemical composition.

The method according to any one of the preceding claims, including additionally heating by means of a second heat source the first stream of compressed working liquid to produce a first stream of heated working fluid.

A system for regeneratively utilising heat in a thermodynamic cycle, the thermodynamic cycle utilising a working liquid and working vapour, each including a binary mixture containing a first chemical composition and a second chemical composition, the first chemical composition having a lower boiling point temperature than the second chemical composition, the system comprising:

a first reactor having an operatively upper end and an operatively lower end and including working liquid and working vapour therein;

a first compressor device, in fluid flow communication with the first reactor, for receiving working vapour, as a first stream of working vapour, from the first reactor and compressing the received first stream of working vapour to produce a first stream of compressed working vapour, the first compressor device being in further fluid flow communication with the first reactor for introducing the first stream of compressed working vapour to the working liquid in the first reactor for absorption by the working liquid to thereby heat the working liquid;

a second compressor device, in fluid flow communication with the first reactor, for receiving working liquid, as a first stream of working liquid, from the first reactor and compressing the received first stream of working liquid to produce a first stream of compressed working liquid;

a first heat exchange element, in fluid flow communication with the second compressor device, for receiving the first stream of compressed working liquid and transferring heat thereto that is received from a first heat source, being in the form of a body of working liquid, to produce a first stream of heated working vapour; and

an expansion device, in fluid flow communication with the first heat exchange element, for receiving and expanding the first stream of heated working vapour to obtain usable energy and produce a first stream of exhaust working vapour, the expansion device being in further fluid flow communication with the body of working liquid for introducing the first stream of exhaust working vapour to the body of working liquid for absorption by the body of working liquid to thereby heat it.

12. The system according to claim 1 1 , wherein the working vapour in the first reactor is in communication with and located operatively above the working liquid in the first reactor.

13. The system according to claim 1 1 or 12, wherein the body of working liquid is located in and forms part of the working liquid in the first reactor.

14. The system according to claim 1 1 or 12, wherein the body of working liquid is located in a second reactor.

15. The system according to any one of claims 1 1 to 14, wherein the first heat exchange element is located inside the first reactor.

16. The system according to any one of claims 1 1 to 14, wherein the first heat exchange element is located inside a second reactor.

17. The system according to any one of claims 1 1 to 16, wherein the first reactor has a temperature gradient from its operatively upper end to its operatively lower end, wherein the temperature increases in an operatively downwardly direction.

18. The system according to claim 17, wherein there is a temperature difference between the operatively upper and lower ends being any one of:

- at least 25 degrees Celsius;

- at least 50 degrees Celsius;

- at least 75 degrees Celsius; and

- at least 100 degrees Celsius.

19. The system according to claim 17 or 18, wherein the introduction of the first stream of compressed working vapour to the working liquid in the first reactor assists in maintaining the temperature gradient over the first reactor.

20. The system according to any one of claims 1 1 to 19, wherein the first reactor has a concentration gradient of the first chemical composition relative to the second chemical composition from its operatively upper end to its operatively lower end, wherein the concentration of the first chemical composition relative to the second chemical composition increases in an operatively upwardly direction, and the concentration of the first chemical composition relative to the second chemical composition decreases in an operatively downwardly direction.

21 . The system according to claim 20, wherein working liquid in proximity of the operatively upper end and working liquid in proximity of the operatively lower end respectively include any one of the following concentration distributions: the working liquid in proximity of the operatively upper end including at least 70 mole percent of the first chemical composition and less than 30 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 70 mole percent of the second chemical composition and less than 30 mole percent of the first chemical composition;

the working liquid in proximity of the operatively upper end including at least 80 mole percent of the first chemical composition and less than 20 mole percent of the second chemical composition, with the working liquid in proximity of the operatively lower end including at least 80 mole percent of the second chemical composition and less than 20 mole percent of the first chemical composition;

22. The system according to any one of claims 1 1 to 21 , including a second heat exchange element, in fluid flow communication with the second compressor device, for receiving the first stream of compressed working liquid and transferring heat thereto that is received from a second heat source to produce a first stream of heated working fluid.