Note: Descriptions are shown in the official language in which they were submitted.
CA 02590490 2007-05-30
Pulsed Electrolysis Apparatus and Method of Using Same
FIELD OF THE INVENTION
The present invention relates generally to electrolysis systems and, more
particularly, to a high efficiency electrolysis system and methods of using
same.
BACKGROUND OF THE INVENTION
Fossil fuels, in particular oil, coal and natural gas, represent the primary
sources
of energy in today's world. Unfortunately in a world of rapidly increasing
energy needs,
dependence on any energy source of finite size and limited regional
availability has dire
consequences for the world's economy. In particular, as a country's need for
energy increases,
so does its vulnerability to disruption in the supply of that energy source.
Additionally, as fossil
fuels are the largest single source of carbon dioxide emissions, a greenhouse
gas, continued
reliance on such fuels can be expected to lead to continued global warming.
Accordingly it is
imperative that alternative, clean and renewable energy sources be developed
that can replace
fossil fuels.
Hydrogen-based fuel is currently one of the leading contenders to replace
fossil
fuel. There are a number of techniques that can be used to produce hydrogen,
although the
primary technique is by steam reforming natural gas. In this process thermal
energy is used to
react natural gas with steam, creating hydrogen and carbon dioxide. This
process is well
developed, but due to its reliance on fossil fuels and the release of carbon
dioxide during
production, it does not alleviate the need for fossil fuels nor does it lower
the environmental
impact of its use over that of traditional fossil fuels. Other, less developed
hydrogen producing
techniques include (i) biomass fermentation in which methane fermentation of
high moisture
content biomass creates fuel gas, a small portion of which is hydrogen; (ii)
biological water
splitting in which certain photosynthetic microbes produce hydrogen from water
during their
metabolic activities; (iii) photoelectrochemical processes using either
soluble metal complexes
as a catalyst or seiniconducting electrodes in a photochemical cell; (iv)
thermochemical water
splitting using chemicals such as bromine or iodine, assisted by heat, to
split water molecules;
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(v) thermolysis in which concentrated solar energy is used to generate
temperatures high enough
to split methane into hydrogen and carbon; and (vi) electrolysis.
Electrolysis as a means of producing hydrogen has been known and used for over
80 years. In general, electrolysis of water uses two electrodes separated by
an ion conducting
electrolyte. During the process hydrogen is produced at the cathode and oxygen
is produced at
the anode, the two reaction areas separated by an ion conducting diaphragm.
Electricity is
required to drive the process. An alternative to conventional electrolysis is
high temperature
electrolysis, also known as steam electrolysis. This process uses heat, for
example produced by
a solar concentrator, as a portion of the energy required to cause the needed
reaction. Although
lowering the electrical consumption of the process is desirable, this process
has proven difficult
to implement due to the tendency of the hydrogen and oxygen to recombine at
the technique's
high operating temperatures.
A high temperature heat source, for example a geothermal source, can also be
used as a replacement for fossil fuel. In such systems the heat source raises
the temperature of
water sufficiently to produce steam, the steam driving a turbine generator
which, in turn,
produces electricity. Alternately the heat source can raise the temperature of
a liquid that has a
lower boiling temperature than water, such as isopentane, which can also be
used to drive a
turbine generator. Alternately the heat source can be used as a fossil fuel
replacement for non-
electrical applications, such as heating buildings.
Although a variety of alternatives to fossil fuels in addition to hydrogen and
geothermal sources have been devised, to date none of them have proven
acceptable for a variety
of reasons ranging from cost to environmental impact to availability.
Accordingly, what is
needed is a new energy source, or a more efficient form of a current
alternative energy source,
that can effectively replace fossil fuels without requiring an overly complex
distribution system.
The present invention provides such a system and method of use.
SUMMARY OF THE INVENTION
The present invention provides an electrolysis system and method of using
same.
In addition to an electrolysis tank and a membrane separating the tank into
two regions, the
system includes a plurality of metal members and a plurality of high voltage
electrodes. The
plurality of metal members includes at least a first metal member and a second
metal member
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contained within the first region of the electrolysis tank and at least a
third metal member and a
fourth metal member contained within the second region of the electrolysis
tank. The plurality
of high voltage electrodes includes at least a first high voltage anode
contained within the first
region of the electrolysis tank and interposed between the first and second
metal members, and
at least a first high voltage cathode contained within the second region of
the electrolysis tank
and interposed between the third and fourth metal members. The high voltage
applied to the
high voltage electrodes is pulsed. Preferably the liquid within the tank is
comprised of one or
more of; water, deuterated water, tritiated water, semiheavy water, heavy
oxygen water, and/or
any other water containing an isotope of either hydrogen or oxygen.
Preferably the high voltage pulses occur at a frequency between 50 Hz and I
MHz, and more preferably at a frequency between 100 Hz and 10 kHz. Preferably
the high
voltage pulses have a pulse duration of between 0.01 and 75 percent of the
time period defined
by the frequency, and more preferably a pulse duration of between 1 and 50
percent of the time
period defined by the frequency. Preferably the high voltage is between 50
volts and 50
kilovolts, more preferably between 100 volts and 5 kilovolts. The metal
members and the high
voltage electrodes are fabricated from any of a variety of materials, although
preferably the
material is selected from the group consisting of stainless steel, titanium,
copper, iron, cobalt,
steel, manganese, zinc, nickel, platinum, palladium, carbon, graphite, carbon-
graphite, and alloys
of these materials and alloys thereof. The metal members and the high voltage
electrodes can
utilize any of a variety of surface shapes and can be either positioned
parallel to one another or
not parallel to one another.
In at least one embodiment, the concentration of electrolyte in the liquid is
between 0.05 and 10 percent by weight. In at least one other embodiment of the
invention, the
concentration of electrolyte in the liquid is between 0.05 and 2.0 percent by
weight. In yet at
least one other embodiment of the invention, the concentration of electrolyte
in the liquid is
between 0.1 and 0.5 percent by weight.
In at least one embodiment, the electrolysis system is cooled. Cooling is
preferably achieved by thermally coupling at least a portion of the
electrolysis system to a
portion of a conduit containing a heat transfer medium. The conduit can
surround the
electrolysis tank, be integrated within the walls of the electrolysis tank, or
be contained within
the electrolysis tank.
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In at least one embodiment, the electrolysis system also contains a system
controller. The system controller can be used to perform system optimization,
either during an
initial optimization period or repeatedly throughout system operation.
A further understanding of the nature and advantages of the present invention
may be realized by reference to the remaining portions of the specification
and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an illustration of an exemplary embodiment of the invention;
Fig. 2 is an illustration of an alternate exemplary embodiment utilizing
multiple
pairs of low voltage electrodes;
Fig. 3 is an illustration of an alternate exemplary embodiment utilizing
multiple
pairs of high voltage electrodes;
Fig. 4 is an illustration of an alternate exemplary embodiment utilizing
multiple
pairs of low voltage electrodes and multiple pairs of high voltage electrodes;
Fig. 5 is an illustration of an alternate exemplary embodiment utilizing a
horizontal cylindrical tank;
Fig. 6 is an illustration of an alternate exemplary embodiment utilizing a
horizontal cylindrical tank and a separation membrane running lengthwise in
the tank;
Fig. 7 is an illustration of one mode of operation;
Fig. 8 is an illustration of an alternate mode of operation that includes
initial
process optimization steps;
Fig. 9 is an illustration of an alternate, and preferred, mode of operation in
which
the process undergoes continuous optimization; and
Fig. 10 is an illustration of an exemplary embodiment based on the embodiment
of Fig. 1, except for the inclusion of a system controller.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
Fig. 1 is an illustration of an exemplary embodiment of the invention.
Electrolysis system 100 includes a tank 101 comprised of a non-conductive
material, the size of
the tank depending primarily upon the desired output of the system as well as
the dimensions of
the electrodes and the metal members contained within the tank. Although tank
101 is shown as
having a rectangular shape, it will be appreciated that the invention is not
so limited and that
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tank 101 can utilize other shapes, for example cylindrical, square,
irregularly-shaped, etc. Tank
101 is substantially filled with liquid 103. In at least one preferred
embodiment, liquid 103 is
comprised of water with an electrolyte, the electrolyte being either an acid
electrolyte or a base
electrolyte. Exemplary electrolytes include potassium hydroxide and sodium
hydroxide. The
term "water" as used herein refers to water (HZO), deuterated water (deuterium
oxide or D20),
tritiated water (tritium oxide or T20), semiheavy water (HDO), heavy oxygen
water (H2180 or
H217O) or any other water containing an isotope of either hydrogen or oxygen,
either singly or in
any combination thereof (for example, a combination of H20 and D20).
A typical electrolysis system used to decompose water into hydrogen and oxygen
gases utilizes relatively high concentrations of electrolyte. The present
invention, however, has
been found to work best with relatively low electrolyte concentrations,
thereby maintaining a
relatively high initial water resistivity. Preferably the water resistivity
prior to the addition of an
electrolyte is on the order of 1 to 28 megohms. Preferably the concentration
of electrolyte is in
the range of 0.05 percent to 10 percent by weight, more preferably the
concentration of
electrolyte is in the range of 0.05 percent to 2.0 percent by weight, and
still more preferably the
concentration of electrolyte is in the range of 0.1 percent to 0.5 percent by
weight.
Separating tank 101 into two regions is a membrane 105. Membrane 105 permits
ion/electron exchange between the two regions of tank 101 while keeping
separate the oxygen
and hydrogen bubbles produced during electrolysis. Maintaining separate
hydrogen and oxygen
gas regions is important not only as a means of allowing the collection of
pure hydrogen gas and
pure oxygen gas, but also as a means of minimizing the risk of explosions due
to the inadvertent
recombination of the two gases. Exemplary materials for membrane 105 include,
but are not
limited to, polypropylene, tetrafluoroethylene, asbestos, etc. In at least one
embodiment,
membrane 105 is 25 microns thick and comprised of polypropylene.
As noted herein, the present system is capable of generating considerable
heat.
Accordingly, system components such as tank 101 and membrane 105 that are
expected to be
subjected to the heat generated by the system must be fabricated from suitable
materials and
designed to indefinitely accommodate the intended operating temperatures as
well as the internal
tank pressure. For example, in at least one preferred embodiment the system is
designed to
operate at a temperature of approximately 90 C at standard pressure. In an
alternate exemplary
embodiment, the system is designed to operate at elevated temperatures (e.g.,
100 C to 150 C)
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and at sufficient pressure to prevent boiling of liquid 103. In yet another
alternate exemplary
embodiment, the system is designed to operate at even higher temperatures
(e.g., 200 C to 350
C) and higher pressures (e.g., sufficient to prevent boiling). Accordingly, it
will be understood
that the choice of materials (e.g., for tank 101 and membrane 105) and the
design of the system
(e.g., tank wall thicknesses, fittings, etc.) will vary, depending upon the
intended system
operational parameters (primarily temperature and pressure).
Other standard features of electrolysis tank 101 are gas outlets 107 and 109.
As
hydrogen gas is produced at the cathode and oxygen gas is produced at the
anode, in the
exemplary embodiment shown in Fig. 1 oxygen gas will exit tank 101 through
outlet 107 while
hydrogen gas will exit through outlet 109. Replenishment of liquid 103 is
preferably through a
separate conduit, for example conduit 111. In at least one embodiment of the
invention, another
conduit 113 is used to remove liquid 103 from the system. If desired, a single
conduit can be
used for both liquid removal and replenishment. It will be appreciated that
the system can either
be periodically refilled or water and electrolyte can be continuously added at
a very slow rate
during system operation.
The electrolysis system of the invention uses a combination of metal members
and high voltage electrodes. The metal members include at least two metal
members within
each region of the electrolysis tank. The high voltage electrodes include at
least one high
voltage cathode interposed between at least two metal members within one
region of the tank,
and at least one high voltage anode interposed between at least two metal
members within the
other region of the tank. Assuming multiple high voltage cathodes and/or
multiple high voltage
anodes, all cathodes are kept in one region of tank 101 while all anodes are
kept in the other tank
region, the two tank regions separated by membrane 105.
In the embodiment illustrated in Fig. 1, although a single high voltage
cathode
115 and a single high voltage anode 117 are shown, it should be understood
that the invention
can utilize more than one high voltage cathode and more than one high voltage
anode. High
voltage electrodes 115/117 are coupled to a high voltage source 119.
Preferably and as shown,
the faces of the individual high voltage electrodes are parallel to one
another. It should be
understood, however, that the faces of the electrodes do not have to be
parallel to one another.
As previously noted, the high voltage cathode (or cathodes) is positioned
between
at least one pair of metal members and the high voltage anode (or anodes) is
positioned between
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at least one pair of metal members. Thus in the exemplary embodiment shown in
Fig. l, high
voltage cathode 115 is positioned between metal members 121 and 123, and high
voltage anode
117 is positioned between metal members 125 and 127.
In one preferred embodiment, electrodes 115/117 and metal members
121/123/125/127 are comprised of titanium. In another preferred embodiment,
electrodes
115/117 and metal members 121 / 123/ 125/ 127 are comprised of stainless
steel. It should be
appreciated, however, that other materials can be used and that the same
material does not have
to be used for both the metal members and the high voltage electrodes, nor
does the same
material have to be used for both the high voltage anodes and the high voltage
cathodes, nor
does the same material have to be used for all of the metal members. In
addition to titanium and
stainless steel, other exemplary materials that can be used for the metal
members and the high
voltage electrodes include, but are not limited to, copper, iron, cobalt,
steel, manganese, zinc,
nickel, platinum, palladium, carbon, graphite, carbon-graphite, and alloys of
these materials.
Preferably the surface area of the faces of the metal members is a large
percentage of the cross-
sectional area of tank 101, typically on the order of at least 40 percent of
the cross-sectional area
of tank 101, and often between approximately 70 percent and 90 percent of the
cross-sectional
area of tank 101. The high voltage electrodes (e.g., electrodes115 and 117)
may be larger,
smaller or the same size as the metal members (e.g., metal members 121, 123,
125 and 127).
Typically the voltage applied to high voltage electrodes 115/117 by source 119
is
within the range of 50 volts to 50 kilovolts, and preferably within the range
of 100 volts to 5
kilovolts. Rather than continually apply voltage to the electrodes, source 119
is pulsed,
preferably at a frequency of between 50 Hz and 1 MHz, and more preferably at a
frequency of
between 100 Hz and 10 kHz. The pulse width (i.e., pulse duration) is
preferably between 0.01
and 75 percent of the time period defined by the frequency, and more
preferably between 1 and
50 percent of the time period defined by the frequency. Thus, for example, for
a frequency of
150 Hz, the pulse duration is preferably in the range of 0.67 microseconds to
5 milliseconds, and
more preferably in the range of 66.7 microseconds to 3.3 milliseconds.
Alternately, for example,
for a frequency of 1 kHz, the pulse duration is preferably in the range of 0.1
microseconds to
0.75 milliseconds, and more preferably in the range of 10 microseconds to 0.5
milliseconds. The
frequency and/or pulse duration can be changed during system operation, thus
allowing the
system output efficiency to be continually optimized. Although voltage source
119 can include
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internal pulsing means, preferably an external pulse generator 129 controls a
high voltage switch
131 which, in turn, controls the output of voltage source 119. Other means for
pulsing the
voltage source are clearly envisioned, for example using a switching power
supply coupled to an
external pulse generator or using a switching power supply with an internal
pulse generator.
As described herein, the electrolysis process of the invention generates
considerable heat. It will be appreciated that if the system is allowed to
become too hot for a
given pressure, the fluid within tank 101 will begin to boil. Additionally,
various system
components may be susceptible to heat damage. Although the system can be
turned off and
allowed to cool when the temperature exceeds a preset value, for example using
a control system
coupled to a thermocouple or other heat monitor which triggers the control
system when the
system (or tank fluid) exceeds the preset value, this is not a preferred
approach due to the
inherent inefficiency of stopping the process, allowing the system to cool,
and then restarting the
system. A more efficient, and preferred, approach uses means which actively
cool the system to
maintain the temperature within an acceptable range. In at least one preferred
embodiment, the
cooling system does not allow the temperature to exceed 90 C. Although it
will be appreciated
that the invention is not limited to a specific type of cooling system or a
specific implementation
of the cooling system, in at least one embodiment tank 101 is surrounded by
coolant conduit
133, portions of which are shown in Figs. 1-6 and 10. Within coolant conduit
133 is a heat
transfer medium, for example water. Coolant conduit 133 can either surround a
portion of the
electrolysis tank as shown, or be contained within the electrolysis tank, or
be integrated within
the walls of the electrolysis tank. The coolant pump and refrigeration system
is not shown in the
figures as cooling systems are well known by those of skill in the art.
As will be appreciated by those of skill in the art, there are numerous minor
variations of the system described herein and shown in Fig. 1 that will
function substantially the
same as the disclosed system. As previously noted, alternate configurations
can utilize
differently sized/shaped tanks, different electrolytic solutions, and a
variety of different electrode
configurations and materials. Additionally the system can utilize a range of
input powers,
frequencies and pulse widths (i.e., pulse duration). In general, the exact
configuration depends
upon the desired output as well as available space and power. Figs. 2-6
illustrate a few alternate
configurations, including the use of multiple sets of metal members (i.e.,
Fig. 2), multiple sets of
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high voltage electrodes (i.e., Fig. 3), multiple sets of metal members and
high voltage electrodes
(e.g., Fig. 4), and horizontal cylindrical tanks (e.g., Figs. 5 and 6).
Fig. 2 illustrates an alternate embodiment of the system shown in Fig. 1, the
alternate configuration replacing metal member 121 with four metal members 201-
204,
replacing metal member 123 with four metal members 205-208, replacing metal
member 125
with four metal members 209-212, and replacing metal member 127 with metal
members 213-
216. Note that in Fig. 2, membrane 105 hides all but a small portion of metal
member 211 and
all of metal member 212.
Fig. 3 illustrates an alternate embodiment of the system shown in Fig. 1, the
alternate configuration replacing high voltage electrode 115 with two high
voltage electrodes
301-302 and replacing high voltage electrode 117 with two high voltage
electrodes 303-304.
Fig. 4 illustrates an alternate embodiment of the system shown in Fig. 1, the
alternate configuration replacing metal member 121 with four metal members 401-
404,
replacing metal member 123 with four metal members 405-408, replacing metal
member 125
with four metal members 409-412, replacing metal member 127 with four metal
members 413-
416, replacing high voltage electrode 115 with two high voltage electrodes 417-
418 and
replacing high voltage electrode 117 with two high voltage electrodes 419-420.
Note that in Fig.
4, membrane 105 hides all but a small portion of metal member 411 and all of
metal member
412.
Fig. 5 illustrates an alternate embodiment of the system shown in Fig. 1, the
alternate configuration replacing tank 101 with a horizontally configured
cylindrical tank 501,
replacing membrane 105 with an appropriately shaped membrane 503, replacing
metal member
121 with disc-shaped metal member 505, replacing metal member 123 with disc-
shaped metal
member 507, replacing metal member 125 with disc-shaped metal member 509,
replacing metal
member 127 with disc-shaped metal member 511, replacing high voltage electrode
115 with
disc-shaped high voltage electrode 513, and replacing high voltage electrode
117 with disc-
shaped high voltage electrode 515.
Fig. 6 illustrates an alternate embodiment of the system shown in Fig. 1, the
alternate configuration replacing tank 101 with a horizontally configured
cylindrical tank 601
which utilizes a lengthwise membrane 603. Additionally, metal member 121 is
replaced with
metal member 605, metal member 123 is replaced with metal member 607, metal
member 125 is
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replaced with metal member 609, metal member 127 is replaced with metal member
611, high
voltage electrode 115 is replaced with high voltage electrode 613, and high
voltage electrode
117 is replaced with high voltage electrode 615.
It should be understood that the present invention can be operated in a number
of
modes, the primary differences between modes being the degree of process
optimization used
during operation. For example, Fig. 7 illustrates one method of operation
requiring minimal
optimization. As illustrated, initially the electrolysis tank is filled with
liquid, e.g., water (step
701). Assuming the use of an electrolyte as preferred, the electrolyte can
either be mixed into
the water prior to filling the tank or after the tank is filled. The frequency
of the pulse generator
is then set (step 703) as well as the pulse duration (step 705) and the output
of the high voltage
power supply (step 707). It will be appreciated that the order of set-up,
i.e., steps 703-707, is
clearly not critical to the electrolysis process. Once set-up is complete,
electrolysis is initiated
(step 709) and continues (step 711) until the process is terminated (step
713).
After process termination, electrolysis can be re-initiated when desired.
Prior to
electrolysis re-initiation, if desired the water in the electrolysis tank can
be removed (step 715)
and the tank refilled (step 717). Prior to refilling the tank, a series of
optional steps can be
performed. For example, the tank can be washed out (optional step 719) and the
electrodes can
be cleaned, for example to remove oxides, by washing the electrodes with
diluted acids (optional
step 721). Spent, or used up, electrodes can also be replaced prior to
refilling (optional step
723).
The above sequence of processing steps works best once the operational
parameters have been optimized for a specific system configuration since the
system
configuration will impact the heat production efficiency of the process and
therefore the system
output. Exemplary system configuration parameters that affect the optimal
electrolysis settings
include tank size, quantity of water, type and/or quality of water,
electrolyte composition,
electrolyte concentration, pressure, electrode size, electrode composition,
electrode shape,
electrode configuration, electrode separation, metal member size, metal member
composition,
metal member shape, metal member configuration, high voltage setting, pulse
frequency and
pulse duration.
Fig. 8 illustrates an alternate procedure appropriate, for example, for use
with
new, untested system configurations, the approach providing optimization
steps. Initially the
CA 02590490 2007-05-30
tank is filled (step 801) and initial settings for pulse frequency (step 803),
pulse duration (step
805) and high voltage supply output (step 807) are made. Typically the initial
settings are based
on previous settings that have been optimized for a similarly configured
system. For example,
assuming that the new configuration was the same as a previous configuration
except for the
composition of the electrodes, a reasonable initial set-up would be the
optimized set-up from the
previous configuration.
After the initial set-up is completed, electrolysis is initiated (step 809)
and the
output of the system is monitored (step 811), for example the rate of
temperature increase.
System optimization can begin immediately or the system can be allowed to run
for an initial
period of time (step 813) prior to optimization. The initial period of
operation can be based on
achieving a predetermined output, for example a specific rate of temperature
increase, or
achieving a steady state output (e.g., a specific temperature). Alternately
the initial period of
time can simply be a predetermined time period, for example 3 hours.
After the initial time period is exceeded, assuming that the selected approach
uses
step 813, the system output is monitored (step 815) while optimizing one or
more of the
operational parameters. Although the order of parameter optimization is not
critical, in at least
one preferred embodiment the first parameter to be optimized is pulse duration
(step 817)
followed by the optimization of the pulse frequency (step 818). Then the
voltage of the high
voltage supply is optimized (step 819). In this embodiment after optimization
is complete the
electrolysis process is allowed to continue (step 821) without further
optimization until the
process is halted, step 823. In another, and preferred, alternative approach
illustrated in Fig. 9,
optimization steps 817-819 are performed continuously throughout the
electrolysis process until
electrolysis is suspended. Alternately a subset of steps 817-819 are performed
continuously
throughout the electrolysis process.
The optimization process described relative to Figs. 8 and 9 can be performed
manually. In the preferred embodiment, however, the system and the
optimization of the system
are controlled via a system controller such as controller 1001 shown in Fig.
10. Assuming that
controller 1001 is used to control and optimize the pulse frequency, pulse
duration and high
voltage, system controller 1001 is coupled to the pulse generator and the
power supply as shown.
If the system controller is only used to control and optimize a subset of
these parameters, the
system controller is coupled accordingly (i.e., coupled to the pulse generator
to control pulse
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frequency and duration; coupled to the high voltage source to control the high
voltage). In order
to allow complete automation, preferably system controller 1001 is also
coupled to a system
monitor, for example at least one temperature monitor 1003 as shown. In at
least one preferred
embodiment system controller 1001 is also coupled to a monitor 1005, monitor
1005 providing
either the pH or the resistivity of liquid 103 within electrolysis tank 101,
thereby providing
means for determining when additional electrolyte needs to be added. In at
least one preferred
embodiment system controller 1001 is also coupled to a liquid level monitor
1007, thereby
providing means for determining when additional liquid needs to be added to
the electrolysis
tank. Preferably system controller 1001 is also coupled to one or more flow
valves 1009 which
allow water, electrolyte, or a combination of water and electrolyte to be
automatically added to
the electrolysis system in response to pH/resistivity data provided by monitor
1005 (i.e., when
the monitored pH/resistivity falls outside of a preset range) and/or liquid
level data provided by
monitor 1007 (i.e., when the monitored liquid level falls below a preset
value).
As will be understood by those familiar with the art, the present invention
may be
embodied in other specific forms without departing from the spirit or
essential characteristics
thereof. Accordingly, the disclosures and descriptions herein are intended to
be illustrative, but
not limiting, of the scope of the invention which is set forth in the
following claims.
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