U.S. patent application number 10/861350 was filed with the patent office on 2005-12-08 for method of and apparatus for producing hydrogen using geothermal energy.
Invention is credited to Zachar, Oron David.
Application Number | 20050269211 10/861350 |
Document ID | / |
Family ID | 35446499 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050269211 |
Kind Code |
A1 |
Zachar, Oron David |
December 8, 2005 |
Method of and apparatus for producing hydrogen using geothermal
energy
Abstract
The present inventive subject matter is drawn to apparatus for
producing hydrogen using geothermal energy comprising: heating
means for heating a solution for use in electrolysis with heat from
geothermal fluid and producing a heated solution; and electrolysis
means for producing hydrogen by electrolysis of said heated
solution. The present invention also relates to a method for
producing hydrogen using geothermal energy comprising: heating a
solution for use in electrolysis with heat from geothermal fluid
and producing a heated solution; and producing hydrogen by
electrolysis of said heated solution. In addition, in accordance
with the present invention, apparatus for producing hydrogen using
geothermal energy is provided comprising: heating means for heating
a solution for use in electrolysis with heat from geothermal fluid
and producing a heated solution; electrolysis means for producing
hydrogen by electrolysis of said heated solution; and power
producing means utilizing the pressure of said hydrogen for
producing power.
Inventors: |
Zachar, Oron David;
(Tel-Aviv, IL) |
Correspondence
Address: |
NATH & ASSOCIATES
1030 15th STREET, NW
6TH FLOOR
WASHINGTON
DC
20005
US
|
Family ID: |
35446499 |
Appl. No.: |
10/861350 |
Filed: |
June 7, 2004 |
Current U.S.
Class: |
205/637 |
Current CPC
Class: |
Y02E 60/366 20130101;
C25B 15/08 20130101; C25B 1/04 20130101; Y02E 70/10 20130101; Y02E
60/36 20130101 |
Class at
Publication: |
205/637 |
International
Class: |
C25B 001/02 |
Claims
What is claimed is:
1. Apparatus for producing hydrogen using geothermal energy
comprising: a) heating means apparatus for heating a solution for
use in electrolysis with heat from geothermal fluid and producing a
heated solution; and b) electrolysis means apparatus for producing
hydrogen by electrolysis of said heated solution.
2. The apparatus according to claim 1 wherein said heating means
for heating a solution for use in electrolysis with heat from
geothermal fluid and producing a heated solution comprises an
indirect heat exchanger for transferring heat from said geothermal
fluid to a solution for heating said solution.
3. Apparatus according to claim 1 including supply means for
supplying said heated solution to said electrolysis means for
producing hydrogen by electrolysis of said heated solution.
4. Apparatus according to claim 2 further including a separator for
separating said geothermal fluid into geothermal steam and
geothermal liquid and a pump for pumping geothermal liquid of said
geothermal fluid.
5. Apparatus according to claim 4 further including power producing
means that includes a vaporizer for vaporizing working fluid
present in said vaporizer and producing working fluid vapor using
heat present in said geothermal liquid, a vapor turbine for
expanding said working fluid vapor and producing power, and a
condenser for condensing the expanded working fluid exiting said
vapor turbine and producing working fluid condensate and a cycle
pump for supplying said working fluid condensate to said
vaporizer.
5. Apparatus according to claim 4 wherein said working fluid is an
organic working fluid.
6. Apparatus according to claim 4 further including supply means
for supplying heat depleted geothermal liquid exiting said
vaporizer to said indirect heat exchanger for heating said solution
and producing said heated solution for electrolysis.
7. Apparatus according to claim 6 wherein said pump pumps further
heat depleted geothermal liquid exiting said indirect heat
exchanger to an injection well.
8. Apparatus according to claim 1 including further means for
producing oxygen by electrolysis of said heated solution.
9. Apparatus according to claim 8 including further means for
utilizing said oxygen for producing power.
10. Apparatus according to claim 8 including storage means for
storing said oxygen for later use.
11. Apparatus according to claim 1 including further means for
utilizing said hydrogen for producing power.
12. Apparatus according to claim 1 including storage means for
storing said hydrogen for later use.
13. Apparatus according to claim 12 including apparatus for
producing power using stored hydrogen stored in said storage
means.
14. Apparatus according to claim 13 including apparatus for
producing power using stored hydrogen stored in said storage means
during period of peak electricity demand.
15. Apparatus for producing hydrogen using geothermal energy
comprising: a) heating means for heating a solution for use in
electrolysis with heat from geothermal fluid and producing a heated
solution; b) electrolysis means for producing hydrogen by
electrolysis of said heated solution; and c) power producing means
utilizing the pressure of said hydrogen for producing power.
16. The apparatus according to claim 15 wherein said heating means
for heating a solution for use in electrolysis with heat from
geothermal fluid and producing a heated solution comprises an
indirect heat exchanger for transferring heat from said geothermal
fluid to a solution for heating said solution.
17. Apparatus according to claim 15 including supply means for
supplying said heated solution to said electrolysis means for
producing hydrogen by electrolysis of said heated solution.
18. Apparatus according to claim 15 wherein said power producing
means utilizing the pressure of said hydrogen for producing power
includes a separator for separating said geothermal fluid into
geothermal steam and geothermal liquid and a pump using the
pressure of said hydrogen in pumping geothermal liquid of said
geothermal fluid.
19. Apparatus according to claim 18 wherein said power producing
means utilizing the pressure of said hydrogen for producing power
further includes a vaporizer for vaporizing working fluid present
in said vaporizer and producing working fluid vapor using heat
present in said geothermal liquid, a vapor turbine for expanding
said working fluid vapor and producing power, and condenser for
condensing the expanded working fluid exiting said vapor turbine
and producing working fluid condensate and a cycle pump for
supplying said working fluid condensate to said vaporizer.
20. Apparatus according to claim 19 wherein said working fluid is
an organic working fluid.
21. Apparatus according to claim 18 further including supply means
for supplying heat depleted geothermal liquid exiting said
vaporizer to said indirect heat exchanger for heating said solution
and producing said heated solution for electrolysis.
22. Apparatus according to claim 21 wherein said pump pumps further
heat depleted geothermal liquid exiting said indirect heat
exchanger to an injection well.
23. Apparatus according to claim 15 including further means for
producing oxygen by electrolysis of said heated solution.
24. Apparatus according to claim 23 including further means for
utilizing the pressure of said oxygen for producing power.
25. Apparatus according to claim 24 wherein said further means for
utilizing the pressure of said gas for producing power includes a
separator for separating said geothermal fluid into geothermal
steam and geothermal liquid, power producing means using said
geothermal liquid to produce power and means using the pressure of
said oxygen for pumping geothermal liquid of said geothermal
fluid.
26. A method for producing hydrogen using geothermal energy
comprising: a) heating a solution for use in electrolysis with heat
from geothermal fluid and producing a heated solution; b) producing
hydrogen by electrolysis of said heated solution; and c) utilizing
the pressure of said hydrogen for producing power
27. The method according to claim 26 wherein the step of heating a
solution for use in electrolysis with heat from geothermal fluid
and producing a heated solution is carried out by supplying said
geothermal fluid to an indirect heat exchanger for transferring
heat from said geothermal fluid to a solution for heating said
solution.
28. A method according to claim 26 including supplying said heated
solution to apparatus for use of said heated solution in
electrolysis for producing hydrogen.
29. A method according to claim 26 wherein the step of utilizing
the pressure of said hydrogen for producing power includes
separating said geothermal fluid into geothermal steam and
geothermal liquid, using geothermal liquid to produce power and
using the pressure of said hydrogen in pumping geothermal liquid of
said geothermal fluid.
30. A method according to claim 26 including the further step of
producing oxygen by electrolysis of said heated solution.
31. A method according to claim 29 including the further step of
utilizing the pressure of said oxygen for producing power.
32. A method according to claim 31 wherein the further step of
utilizing the pressure of said oxygen for producing power includes
separating said geothermal fluid into geothermal steam and
geothermal liquid, using said geothermal liquid to produce power
and using the pressure of said oxygen in pumping geothermal liquid
of said geothermal fluid.
33. A method according to claim 30 including the further step of
producing power using said oxygen.
34. A method according to claim 26 including the further step of
producing power using said hydrogen.
35. Apparatus for producing hydrogen using geothermal energy
comprising: (a) heating means for heating a solution for use in
electrolysis with heat from geothermal fluid and producing a heated
solution; (b) electrolysis means for producing hydrogen by
electrolysis of said heated solution; and (c) storage means for
storing said hydrogen for later use.
36. Apparatus according to claim 35 including apparatus for
producing power using stored hydrogen stored in said storage
means.
37. Apparatus according to claim 36 including apparatus for
producing power using stored hydrogen stored in said storage means
during period of peak electricity demand.
38. A method for producing hydrogen using geothermal energy
comprising: a) heating a solution for use in electrolysis with heat
from geothermal fluid and producing a heated solution; b) producing
hydrogen by electrolysis of said heated solution; and c) storing
said hydrogen for later use.
39. A method according to claim 38 wherein the further step of
storing said hydrogen for later use is carried out by storing said
hydrogen during off-peak periods of electricity demand for use
during periods of peak electricity demand.
40. A method according to claim 38 including the further step of
using said stored hydrogen for producing electricity.
41. Apparatus for producing hydrogen using geothermal energy
comprising: (a) heating means for heating a solution for use in
electrolysis with heat from geothermal fluid and producing a heated
solution; (b) electrolysis means for producing hydrogen by
electrolysis of said heated solution; and (c) power producing means
for producing power using heat present in said geothermal
fluid.
42. The apparatus according to claim 41 wherein said heating means
for heating a solution for use in electrolysis with heat from
geothermal fluid and producing a heated solution comprises an
indirect heat exchanger for transferring heat from said geothermal
fluid to a solution for heating said solution.
43. Apparatus according to claim 42 further including a separator
for separating said geothermal fluid into geothermal steam and
geothermal liquid and a pump for pumping geothermal liquid of said
geothermal fluid.
44. Apparatus according to claim 43 wherein said power producing
means includes a vaporizer for vaporizing working fluid present in
said vaporizer and producing working fluid vapor using heat present
in said geothermal liquid, a vapor turbine for expanding said
working fluid vapor and producing power, and a condenser for
condensing the expanded working fluid exiting said vapor turbine
and producing working fluid condensate and a cycle pump for
supplying said working fluid condensate to said vaporizer.
45. Apparatus according to claim 44 wherein said working fluid is
an organic working fluid.
46. Apparatus according to claim 45 further including supply means
for supplying heat depleted geothermal liquid exiting said
vaporizer to said indirect heat exchanger for heating said solution
and producing said heated solution for electrolysis.
47. A method for producing hydrogen using geothermal energy
comprising: a) heating a solution for use in electrolysis with heat
from geothermal fluid and producing a heated solution; b) producing
hydrogen by electrolysis of said heated solution; and c) producing
power using heat present in said geothermal fluid.
48. The method according to claim 47 wherein the step of heating a
solution for use in electrolysis with heat from geothermal fluid
and producing a heated solution is carried out by supplying said
geothermal fluid to an indirect heat exchanger for transferring
heat from said geothermal fluid to a solution for heating said
solution.
49. A method according to claim 47 including the steps of
separating said geothermal fluid into geothermal steam and
geothermal liquid, producing power from said geothermal liquid and
pumping the geothermal liquid of said geothermal fluid.
50. A method according to claim 49 wherein the step of producing
power from said geothermal liquid is carried out by supplying said
geothermal liquid to a vaporizer of a power producing means for
vaporizing working fluid present in said vaporizer and producing
working fluid vapor using heat present in said geothermal liquid,
said power producing means further comprising a vapor turbine for
expanding said working fluid vapor and producing power, and a
condenser for condensing the expanded working fluid exiting said
vapor turbine and producing working fluid condensate and a cycle
pump for supplying said working fluid condensate to said
vaporizer.
51. A method according to claim 50 wherein the step of vaporizing
working fluid present in said vaporizer and producing working fluid
vapor using heat present in said geothermal liquid for expansion in
said vapor turbine of said power producing means and production of
power is carried out by vaporizing an organic working fluid present
in said vaporizer.
52. A method according to claim 51 further including supplying heat
depleted geothermal liquid exiting said vaporizer to said indirect
heat exchanger for heating said solution and producing said heated
solution for electrolysis.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] This invention relates to a method and apparatus for
producing hydrogen using geothermal energy, and more particularly,
to a method and apparatus for producing hydrogen via electrolysis
using geothermal energy.
[0003] 2. Background of the Invention
[0004] Recently an increasing interest has been developing in
methods of producing renewable energy that produces little or
minimal pollution. One of the ways is using hydrogen to produce
power or electricity. However, the methods of producing hydrogen at
present are rather expensive and also can cause pollution.
[0005] U.S. Pat. No. 5,661,977 discloses a system for generation of
electricity from geothermal energy wherein one or more substances
are transported down a well to a depth at which geothermal heat
(whether from brine or steam reservoirs or hot, dry rock) is
sufficient to cause an endothermic reaction or an electrolysis
reaction to occur among substances. In a second embodiment of the
invention disclosed in this US Patent, a system is disclosed for
the generation of electricity from geothermal energy wherein one
juncture of a thermocouple is transported down a well to a depth at
which geothermal heat is sufficient to create a temperature
difference, relative to the temperature of the other juncture of
the thermocouple. Such systems are rather complicated to construct
so that the costs for constructing such system could be high.
[0006] Geothermal energy is conventionally produced using a
constant flow rate of the geothermal fluid. Due to this, such a
geothermal power plant operates at a fixed production level, while
on the other hand, consumer power demand varies significantly
between peak hours and off-peak hours. As a result, operation of
such geothermal power plants is not cost effective.
[0007] As far as room temperature electrolysis operated at
atmospheric pressure is concerned, the energy requirements are
relatively high. Thus, electrolysis is a relatively expensive
method of producing hydrogen.
[0008] Fouillac et al. (2003) discuss the use of geothermal heat to
pre-heat the solution for high temperature (around 900.degree. C.
or more) electrolysis with additional energy sources such as coal-
or gas-fired power being combined for such a use. In this paper, it
is suggested that the geothermal energy could be combined with
nuclear power plant energy.
[0009] It is therefore an object of the present invention to
provide a new and improved method of and apparatus for producing
hydrogen and operation of geothermal power plants wherein the
disadvantages as outlined above are reduced or substantially
overcome.
SUMMARY OF THE INVENTION
[0010] The present inventive subject matter is drawn to apparatus
for producing hydrogen using geothermal energy comprising: heating
means apparatus for heating a solution for use in electrolysis with
heat from geothermal fluid and producing a heated solution; and
electrolysis means apparatus for producing hydrogen by electrolysis
of said heated solution.
[0011] The present invention also relates to a method for producing
hydrogen using geothermal energy comprising: heating a solution for
use in electrolysis with heat from geothermal fluid and producing a
heated solution; and producing hydrogen by electrolysis of said
heated solution.
[0012] In a further embodiment of the present invention, apparatus
for producing hydrogen using geothermal energy is provided
comprising: heating means for heating a solution for use in
electrolysis with heat from geothermal fluid and producing a heated
solution; electrolysis means apparatus for producing hydrogen by
electrolysis of said heated solution; and power producing means
utilizing the pressure of said hydrogen for producing power.
[0013] In this embodiment, a method for producing hydrogen using
geothermal energy is also provided comprising: heating a solution
for use in electrolysis with heat from geothermal fluid and
producing a heated solution; producing hydrogen by electrolysis of
said heated solution; and utilizing the pressure of said hydrogen
for producing power.
[0014] The integration of geothermal and electrolysis plants of the
present invention as described herein is advantageous since the
efficiency of the integrated or combined geothermal and
electrolysis plant is higher than independently operated plants.
This is achieved by using the heat present in the geothermal fluid
for heating the solution prior to electrolysis and also permitting
the use of the pressure of the hydrogen and/or oxygen electrolysis
products in the pumping of brine to be injected into the injection
well of the geothermal power plant.
[0015] Furthermore, the method and apparatus of the present
invention permits the integrated or combined geothermal and
electrolysis plant to have flexible modes of operation during peak
and off-peak demand hours. In particular, the hydrogen and oxygen
produced by the electrolysis system of the present invention are
energy storage vehicles that enable the shift of off-peak
geothermal power to be sold and consumed during periods of peak
power demand. The local use of the electrolysis hydrogen and oxygen
products make it unnecessary to use high-pressure storage or
transportation of these gases. Consequently, the available pressure
of the electrolysis produced hydrogen and oxygen can be used for
other purposes. More importantly, the above-mentioned flexibility
of operation of the integrated or combined plant is achieved while
the geothermal fluid pumping rate remains substantially constant.
This is achieved by using a combination of valves that permits the
variable diversion of the geothermal fluid from the geothermal
power plant to the electrolysis system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] A description of the present inventive subject matter
including embodiments thereof is presented and with reference to
the accompanying drawings, the description is not meant to be
considered limiting in any manner, wherein:
[0017] FIG. 1 is a graphical representation of a combined power
plant;
[0018] FIG. 2 is a graphical representation of a further embodiment
of a combined power plant;
[0019] FIG. 3 is a graphical representation of an additional
embodiment of a combined power plant; and
[0020] FIG. 4 is a graphical representation of a still further
embodiment of a combined power plant.
[0021] Like reference numerals and designations in the various
drawings refer to like elements.
DETAILED DESCRIPTION
[0022] Turning now to the Figures, FIG. 1 represents an embodiment
of a combined power plant that operates in accordance with the
present invention. As can be seen from the figure, numeral 10A
designates a combined power plant for the production of hydrogen
using geothermal energy. Combined power plant 10A includes
vaporizer 12A of geothermal power plant 15A for vaporizing working
fluid present in the vaporizer using heat present in geothermal
liquid or brine supplied thereto, the geothermal liquid or brine
being produced by a separator (not shown) that separates the
geothermal liquid or brine as well as geothermal steam from
geothermal fluid extracted from production well 11A. Working fluid
vapor exiting vaporizer 12A is supplied to vapor turbine 14A where
it is expanded and power is produced as well as expanded working
fluid. Preferably, vapor turbine 14A drives electric generator 16A
for producing electric power. Expanded working fluid vapor exiting
vapor turbine 14A is supplied to condenser 17A, which is an
air-cooled condenser or a water-cooled condenser, and working fluid
condensate is produced which is supplied to vaporizer 12A using
cycle pump 18A. Preferably, an organic working fluid is used for
working fluid of geothermal power plant 15A. Examples of such
organic working fluids are butane, i.e. n-butane, or iso-butane,
pentane, i.e. n-pentane, or iso-pentane, hexane, i.e. n-hexane, or
iso-hexane, etc. and mixtures of the above-mentioned fluids,
preferably, pentane, i.e. n-pentane, or iso-pentane.
[0023] In accordance with this embodiment of the present invention,
heat depleted geothermal liquid or brine exiting vaporizer 12A is
supplied to heat exchanger 22A of electrolysis system 25A for
heating water or solution supplied thereto. Specific advantages of
using electrolysis together with a fuel cell are described in U.S.
Pat. No. 6,127,055. Thereafter, the further heat-depleted
geothermal liquid or brine is supplied to injection well 21A using
pump 20A. The heated water or heated solution exiting heat
exchanger 22A is supplied to electrolysis unit 24A wherein
electrolysis of the heated water or heated solution is carried out.
During electrolysis of the heated water or heated solution using
electrodes 26A hydrogen and oxygen are produced in hydrogen supply
means 28A and oxygen supply means 29A. Hydrogen may be used in
utilization device 30A to produce e.g. in electricity using e.g.
fuel cells, combustion processes such as in gas turbines, steam
turbines, internal combustion engines, etc. Alternatively, the
hydrogen produced can be used to produce methanol or ammonia.
Oxygen produced can be used in utilization device 32A e.g. in
combustion processes such as in gas turbines or steam turbines, or
used together with hydrogen in a fuel cell to produce
electricity.
[0024] In an additional embodiment, see FIG. 2, part of the heat of
condensation of the organic Rankine cycle turbine can be used for
pre-heating the water to be used in electrolysis. Thus, this
embodiment is very similar to the embodiment of the present
invention described with reference to FIG. 1 except that heater 19B
can be used for pre-heating water with heat present in expanded
vapors exiting turbine 14B prior to supplying the water to heat
exchanger 22B for further heating the water with geothermal fluid.
In this embodiment combined power plant 10B includes vaporizer 12B
of geothermal power plant 15B for vaporizing working fluid present
in the vaporizer using heat present in geothermal liquid or brine
supplied thereto, the geothermal liquid or brine being produced by
a separator (not shown) that separates the geothermal liquid or
brine as well as geothermal steam from geothermal fluid extracted
from production well 11B. Working fluid vapor exiting vaporizer 12B
is supplied to vapor turbine 14B where it is expanded and power is
produced as well as expanded working fluid. Preferably, vapor
turbine 14B drives electric generator 16B for producing electric
power. Expanded working fluid vapor exiting vapor turbine 14B is
first of all supplied to pre-heater 19B where it heats water
supplied to pre-heater 19B and heat depleted working fluid vapor
exiting pre-heater 19B is supplied to condenser 17B, which is an
air-cooled condenser or a water-cooled condenser. The working fluid
condensate produced in condenser 17B is then supplied to vaporizer
12B using cycle pump 18B. Preferably, an organic working fluid is
used for working fluid of geothermal power plant 15B. Examples of
such organic working fluids are butane, i.e. n-butane, or
iso-butane, pentane, i.e. n-pentane, or iso-pentane, hexane, i.e.
n-hexane, or iso-hexane, etc., and mixtures of the above-mentioned
fluids, preferably, pentane, i.e. n-pentane, or iso-pentane.
[0025] In accordance with this embodiment of the present invention,
heat depleted geothermal liquid or brine exiting vaporizer 12B is
supplied to heat exchanger 22B of electrolysis system 25B for
further heating water or solution supplied thereto from pre-heater
19B. Thereafter, the further heat-depleted geothermal liquid or
brine is supplied to injection well 21B using pump 20B. The further
heated water exiting heat exchanger 22B is supplied from heat
exchanger 22B to electrolysis unit 24B wherein electrolysis of the
heated water or heated solution is carried out. During electrolysis
of the further heated water or further heated solution using
electrodes 26B, hydrogen and oxygen are produced in hydrogen supply
means 28B and oxygen supply means 29B. Hydrogen may be used in
utilization device 30B to produce e.g. in electricity using e.g.
fuel cells, combustion processes such as in gas turbines, steam
turbines, internal combustion engines, etc. Alternatively, the
hydrogen produced can be used to produce methanol or ammonia.
Oxygen produced can be used in utilization device 32B e.g. in
combustion processes such as in gas turbines or steam turbines, or
used together with hydrogen in a fuel cell to produce electricity.
In accordance with the present invention, the embodiment of the
present invention can be used in any of the other embodiments of
the present invention.
[0026] FIG. 3 represents a further embodiment of a combined power
plant that operates in accordance with the present invention. As
can be seen from the figure, numeral 10C designates a combined
power plant for the production of hydrogen using geothermal energy.
Combined power plant 10C includes vaporizer 12C of geothermal power
plant 15C for vaporizing working fluid present in the vaporizer
using heat present in geothermal liquid or brine supplied thereto,
the geothermal liquid or brine being produced by a separator (not
shown) that separates the geothermal liquid or brine as well as
geothermal steam from geothermal fluid extracted from production
well 11C. Working fluid vapor exiting vaporizer 12C is supplied to
vapor turbine 15C where it is expanded and power is produced as
well as expanded working fluid. Preferably, vapor turbine 14C
drives electric generator 16C for producing electric power.
Expanded working fluid vapor exiting vapor turbine 14C is supplied
to condenser 17C, which is an air-cooled condenser or a
water-cooled condenser, and working fluid condensate is produced
which is supplied to vaporizer 12C using cycle pump 18C.
Preferably, an organic working fluid is used for working fluid of
geothermal power plant 15C. Examples of such organic working fluids
are butane, i.e. n-butane, or iso-butane, pentane, i.e. n-pentane,
or iso-pentane, hexane, i.e. n-hexane, or iso-hexane, etc., and
mixtures of the above mentioned fluids, preferably, pentane, i.e.
n-pentane, or iso-pentane.
[0027] Also in accordance with this embodiment of the present
invention, heat present in heat depleted geothermal liquid or brine
exiting the vaporizer of the geothermal power plant is used in the
electrolysis system. Thus, heat depleted geothermal liquid or brine
exiting vaporizer 12C is supplied to heat exchanger 22C of
electrolysis system 25C for heating water or solution supplied
thereto. Thereafter, the further heat-depleted geothermal liquid or
brine is supplied to injection well 21C using pump 20C. The heated
water or heated solution exiting heat exchanger 22C is supplied to
electrolysis unit 24C wherein electrolysis of the heated water or
heated solution is carried out. During electrolysis of the heated
water or heated solution using electrodes 26C hydrogen and oxygen
are produced in hydrogen supply means 28C and oxygen supply means
29C. The hydrogen or portion thereof may be used also here to
produce e.g. electricity using e.g. fuel cells, combustion
processes such as in gas turbines, steam turbines, internal
combustion engines, etc. Alternatively, also here, the hydrogen
produced or portion thereof can be used to produce methanol or
ammonia. Oxygen produced or portion thereof can be used also here
e.g. in combustion processes such as in gas turbines or steam
turbines, or used together with hydrogen in a fuel cell to produce
electricity. However, in accordance with this embodiment of the
present invention, hydrogen produced or portion thereof is used to
operate expander 34C for expanding the hydrogen from its present
pressure to a lower pressure such that expander 34C runs pump 19C
for supplying at least portion of further heat-depleted geothermal
liquid exiting heat exchanger 22C to the injection well. Likewise,
oxygen produced or portion thereof is used to operate expander 36C
for expanding the oxygen from its present pressure to a lower
pressure such that expander 36C runs pump 19C for supplying at
least portion of further heat-depleted geothermal liquid exiting
heat exchanger 22C to the injection well.
[0028] In a further embodiment, see e.g. FIG. 4, the hydrogen
and/or oxygen produced by the electrolysis system can be stored for
use at a different time e.g. during peak hours of electricity
demand rather than using the hydrogen online as produced.
Basically, the operation of this embodiment is similar to that of
the embodiment described with reference to FIG. 1 utilizing
geothermal power plant 15D and electrolysis system 25D except that
the hydrogen and/or oxygen produced by electrolysis system 25D is
stored in hydrogen storage apparatus 40D and in oxygen storage
apparatus 42D respectively for later use. Such later use can be
e.g. during peak hours of electricity demand and the hydrogen
and/or oxygen produced can be used in utilization devices 30D and
32D for producing electricity using e.g. fuel cells or combustion
apparatus such as gas turbines or steam turbines, internal
combustion engines, etc. Oxygen produced can be used in utilization
device 32D e.g. in combustion processes such as in gas turbines or
steam turbines, or used together with hydrogen in a fuel cell to
produce electricity. In such a case, the hydrogen and/or oxygen can
be stored for local used to that low-pressure (e.g. approximately
between 3-10 atmospheres) storage can be used. Combined power plant
10D includes vaporizer 12D of geothermal power plant 15D for
vaporizing working fluid present in the vaporizer using heat
present in geothermal liquid or brine supplied thereto, the
geothermal liquid or brine being produced by a separator (not
shown) that separates the geothermal liquid or brine as well as
geothermal steam from geothermal fluid extracted from production
well 11D. Working fluid vapor exiting vaporizer 12D is supplied to
vapor turbine 14D where it is expanded and power is produced as
well as expanded working fluid. Preferably, vapor turbine 14D
drives electric generator 16D for producing electric power.
Expanded working fluid vapor exiting vapor turbine 14D is supplied
to condenser 17D, which is an air-cooled condenser or a
water-cooled condenser, and working fluid condensate is produced
which is supplied to vaporizer 12D using cycle pump 18D.
Preferably, an organic working fluid is used for working fluid of
geothermal power plant 15D. Examples of such organic working fluids
are butane, i.e. n-butane, or iso-butane, pentane, i.e. n-pentane,
or iso-pentane, hexane, i.e. n-hexane, or iso-hexane, etc., and
mixtures of the above-mentioned fluids, preferably, pentane, i.e.
n-pentane, or iso-pentane.
[0029] In accordance with this embodiment of the present invention,
heat depleted geothermal liquid or brine exiting vaporizer 12D is
supplied to heat exchanger 22D of electrolysis system 25D for
heating water or solution supplied thereto. Thereafter, the further
heat-depleted geothermal liquid or brine is supplied to injection
well 21D using pump 20D. The heated water or heated solution
exiting heat exchanger 22D is supplied to electrolysis unit 24D
wherein electrolysis of the heated water or heated solution is
carried out. During electrolysis of the heated water or heated
solution using electrodes 26D hydrogen and oxygen are produced in
hydrogen supply means 28D and oxygen supply means 29D.
[0030] Also, the embodiments of the present invention described
with reference to FIG. 1, FIG. 2 and FIG. 3 can also be used in the
present embodiment. Thus, e.g. the hydrogen and/or oxygen produced
can be first expanded in expanders like 34C and 36C (see FIG. 3)
for driving pump 19C for supplying further heat-depleted geothermal
liquid or brine to the injection well prior to storing the hydrogen
and/or oxygen. However, in a further option, the stored hydrogen
and oxygen can be used and often transported, if preferred, in e.g.
certain industries, e.g. the manufacture of methanol or
ammonia.
[0031] In addition, in this embodiment, if preferred, the ratio of
geothermal liquid supplied to geothermal power plant 15D and to
electrolysis system 25D can be changed and controlled using valve
50D (and valve 52D) so that more geothermal liquid can be supplied
to electrolysis system 25D during e.g. off-peak electricity demand
so that more hydrogen can be stored and subsequently used e.g.
during peak hours of electricity demand to produce electricity.
[0032] By use of the present invention to heat the solution to be
used in electrolysis with heat from geothermal fluid, the
efficiency of the electrolysis process is increased. In addition,
by using the pressure of the hydrogen and/or oxygen produced in
accordance with the present invention, less electric power has to
be used for such a purpose.
[0033] Furthermore, the present invention, particularly as
described in the embodiment of the present invention with reference
to FIG. 4, permits increased production of electricity during e.g.
periods of peak demand for electricity. Moreover, the hydrogen
and/or oxygen can be used locally, without having to substantially
transport the gases, hydrogen and oxygen can be used at relatively
low pressures and their use does not suffer from various market
barriers which are often associated with hydrogen transport and
prolonged storage.
[0034] In addition, while the embodiment of the present invention
described with reference to FIG. 4 describes the use of a binary
cycle organic Rankline cycle turbine for producing electricity from
the geothermal fluid in e.g. a peaking power configuration, other
power systems can be used instead, e.g. geothermal Flash Steam
Power Plants, geothermal Steam Power plants, Enhanced Geothermal
Systems (EGS) Power Plants, Hot Fractured Roc (HFR) and Hot Dry
Rock (HDR) Power Plants. In such geothermal Flash Steam Power
Plants, geothermal Steam Power plants, geothermal steam produced
from the geothermal fluid can be used.
[0035] It should be pointed out that the present invention is
particularly advantageous for use with low to medium temperature
geothermal resources and geothermal fluids and does not need to
rely on supercritical geothermal steam or vapor. Furthermore, the
present invention can be used preferably for low temperature and
intermediate temperature electrolysis for solution temperatures up
to 350.degree. C.
[0036] It is believed that the advantages and improved results
furnished by the method and apparatus of the present invention are
apparent from the foregoing description of the invention. Various
changes and modifications may be made without departing from the
spirit and scope of the invention as described in the claims that
follow.
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