US-12618344-B2 - Thermal energy system and method

Abstract

A thermal energy method for converting thermal to mechanical energy is disclosed. The method comprises circulating liquid and vapor phases of a working fluid in a closed loop comprising a recipient arranged at a lower part and a tube system comprising a rising part, a condenser section of a descending part and a hydrostatic pressure section of a descending part. A corresponding system is also disclosed.

Inventors

• Hans Gude Gudesen
• Per-Erik Nordal

Assignees

• Hans Gude Gudesen

Dates

Publication Date

20260505

Application Date

20230125

Priority Date

20220128

Claims (17)

1. 1 . A thermal energy method for converting thermal to mechanical energy, the method comprising: circulating liquid and vapor phases of a working fluid in a closed loop comprising a recipient constituting a variable volume within a fixed enclosing volume, arranged at a lower part and a tube system comprising a rising part, a descending part with a condenser section and with a hydrostatic pressure section, wherein the circulating comprises: heating the working fluid in the recipient providing working vapor, and compensating for thermal energy loss due to vaporization; condensing the working vapor in the condenser section providing condensed liquid phase working fluid, and setting up a pressure differential contributing to lifting the working vapor in the rising part; collecting the condensed working fluid in the hydrostatic pressure section providing a hydrostatic pressure head; extracting mechanical energy based on the hydrostatic pressure head wherein extracting mechanical energy contributes to expanding the variable volume; and returning the collected condensed working fluid to the recipient.
2. 2 . The thermal energy method according to claim 1 , wherein the heating of the working fluid in the recipient is arranged for maintaining a set temperature of the working fluid.
3. 3 . The thermal energy method according to claim 2 , wherein the set temperature is less than 50° C.
4. 4 . The thermal energy method according to claim 1 , further comprising heating the working vapor in the rising part avoiding condensation.
5. 5 . The thermal energy method according to claim 1 , wherein the condensing comprises exposing the working vapor to cooling surfaces in the condenser section, wherein the temperature of the cooling surfaces is below local dew point.
6. 6 . The thermal energy method according to claim 1 , comprising initially filling the closed loop with one or more non-condensing gases at a set pressure prior to introducing the working fluid.
7. 7 . The thermal energy method according to claim 1 , comprising: initially purging non-condensing gases from the closed loop.
8. 8 . The thermal energy method according to claim 7 , wherein the initial purging comprises evacuation, prior to introducing the working fluid.
9. 9 . The thermal energy method according to claim 1 , wherein the method further comprises: generating electrical energy by one of, a turbine or a piston engine arranged to be driven by the hydrostatic pressure head.
10. 10 . The thermal energy method according to claim 1 , wherein the working fluid comprises at least one of the following, alone or in a mixture: water, carbon dioxide, ammonia, a Freon compound, a hydrocarbon, a halogenated hydrocarbon, tetrafluoroethane, and pentafluoropropane.
11. 11 . The thermal energy method according to claim 1 , comprising the following: accumulating, including, heating, transporting, and collecting, wherein collecting comprises temporarily keeping the condensed working fluid in the hydrostatic pressure section, contributing to reducing the volume of, thus shrinking, the recipient; a hydropower generating including generating electrical energy by passing water through a turbine and into the enclosing volume vacated by the shrinking of the recipient, wherein hydrostatic pressure in the water exceeds vapor pressure in the closed loop, and provides pressure head for the turbine; and regenerating, wherein extracting mechanical energy and returning comprise allowing the working liquid in the hydrostatic pressure section expanding the variable recipient volume and forcing liquid out of the enclosing volume.
12. 12 . A thermal energy system comprising: a closed loop comprising a recipient constituting a variable volume within a fixed enclosing volume arranged at a lower part and a tube system comprising a rising part, and a descending part with a condenser section and with a hydrostatic pressure section; means for heating a working fluid in the recipient providing working vapor and compensating for thermal energy loss due to vaporization; means for condensing the working vapor in the condenser section providing condensed liquid phase working fluid, and setting up a pressure differential contributing to lifting the working vapor in the rising part; means for collecting condensed working fluid in the hydrostatic pressure section providing a hydrostatic pressure head; means for extracting mechanical energy based on the hydrostatic pressure head wherein extracting mechanical energy contributes to expanding the variable volume; and means for returning the collected condensed working fluid to the recipient.
13. 13 . The thermal system according to claim 12 , further comprising means for heating the working vapor in the rising part avoiding condensation.
14. 14 . The thermal energy system according to claim 12 , wherein the means for extracting mechanical energy comprises one of, a turbine or a piston engine.
15. 15 . The thermal energy system according to claim 12 , wherein the recipient volume comprises one of, an expandable bladder, bellows or a piston.
16. 16 . The thermal energy system according to claim 12 , wherein the system comprises: means for temporarily keeping the condensed working fluid in the hydrostatic pressure section, contributing to reducing the volume of, thus shrinking, the recipient; a turbine arranged for generating electrical energy by allowing water passing through the turbine and into the enclosing volume vacated by the shrinking of the recipient, wherein hydrostatic pressure in the water exceeds vapor pressure in the closed loop, and provides pressure head for the turbine; and means for controllably allowing the working liquid in the hydrostatic pressure section expanding the recipient volume and forcing water out of the enclosing volume.
17. 17 . The thermal energy method according to claim 2 , further comprising heating the working vapor in the rising part avoiding condensation.

Description

FIELD OF THE INVENTION The present invention relates to a method for converting thermal energy into mechanical energy and a corresponding system. BACKGROUND OF THE INVENTION Engines that are able to convert thermal energy into mechanical energy have played a central role since the dawn of the industrial revolution, and novel concepts in this field are still emerging. One important trend of particular relevance in the present context is towards operation with low temperature thermal sources. One example is the Organic Rankine cycle (ORC) (https://en.wikipedia.org/wiki/Organic_Rankine_cycle) where working fluids other than water, e.g. n-pentane and toluene, are employed with volatility characteristics that permit operation with low grade heat sources, typically in the range 100° C.-200° C. However, at the lower part of this temperature range and in particular below 70° C. there are at present no generally applicable concepts that can deliver adequate commercially relevant performance. Unfortunately, this is the temperature range where there exist vast untapped thermal energy resources around the globe. There is therefore a pressing need for concepts that can employ these energy reserves to generate mechanical power and electricity. SUMMARY OF THE INVENTION A first aspect of the invention is a thermal energy method for converting thermal to mechanical energy comprising circulating liquid and vapor phases of a working fluid in a closed loop comprising a recipient arranged at a lower part and a tube system comprising a rising part, a descending part with a condenser section and with a hydrostatic pressure section. The circulating comprises heating the working fluid in the recipient providing working vapor, i.e. vaporized working fluid, and compensating for thermal energy loss due to vaporization, condensing the working vapor in the condenser section providing condensed liquid phase working fluid, and setting up a pressure differential contributing to lifting the working vapor in the rising part, collecting the condensed working fluid in the hydrostatic pressure section providing a hydrostatic pressure head, extracting mechanical energy based on the hydrostatic pressure head, and returning the collected condensed working fluid to the recipient. Optionally, the heating of the working fluid in the recipient is arranged for maintaining a set temperature of the working fluid, and, further optionally, the set temperature is less than 50° C. Optionally, the method comprises heating the vaporized working fluid in the rising part avoiding condensation. Optionally, the condensing comprises exposing the working vapor to cooling surfaces in the condenser section, where the temperature of the cooling surfaces is below local dew point. Optionally, the method comprises initially filling the closed loop with one or more non-condensing gases at a set pressure prior to introducing the working fluid. Optionally, the method comprises initially purging non-condensing gases from the closed loop, and, further optionally, the initial purging comprises evacuation prior to introducing the working fluid. Optionally, the method further comprises generating electrical energy by a turbine or a piston engine arranged to be driven by the hydrostatic pressure head. Optionally, the working fluid comprises one or more of the following, alone or in a mixture: water, carbon dioxide, ammonia, a Freon compound, a hydrocarbon, a halogenated hydrocarbon, tetrafluoroethane, and pentafluoropropane. Optionally, the recipient constitutes a variable volume within a fixed enclosing volume, and where the extracting mechanical energy contributes to expanding the variable volume, where the method, further optionally, comprises the following steps: an accumulation step comprising the steps of heating, transporting and collecting, where the step of collecting comprises temporarily keeping the condensed working fluid in the hydrostatic pressure section, contributing to reducing the volume of, thus shrinking, the recipient;a hydropower generation step comprising generating electrical energy by passing water through a turbine and into the enclosing volume vacated by the shrinking of the recipient, where hydrostatic pressure in the water exceeds vapor pressure in the closed loop, and provides pressure head for the turbine; anda regeneration step where the steps of extracting mechanical energy and returning comprise allowing the working liquid in the hydrostatic pressure section expanding the variable recipient volume and forcing liquid out of the enclosing volume. A further aspect of the invention is a thermal energy system comprising means for performing the thermal energy method described above. Optionally, the system comprises: a closed loop comprising a recipient arranged at the lower part and a tube system comprising a rising part, and a descending part with a condenser section and with a hydrostatic pressure section;means for heating the working fluid in the re