Note: Descriptions are shown in the official language in which they were submitted.
CA 02613780 2007-12-07
On-Demand Water Heater Utilizing Circulated Heat Transfer Medium from a Pulsed
Electrolysis
System and Method of Using Same
FIELD OF THE INVENTION
The present invention relates generally to water heating systems.
BACKGROUND OF THE INVENTION
Water heaters are known in the art. One type of water heater, referred to as
an
instantaneous, flow-through, tankless or on-demand water heater, heats only
the amount of water
required by the end user. In such a water heater, when the end user opens a
hot water tap, the water
heater senses the demand and heats the water using a burner or heating element
for as long as the demand
continues. The amount of heat applied to the water passing through the water
heater can be fixed or
variable. In a fixed-capacity system, a constant amount of heat is provided by
the heating
element/burner. As a result of this configuration, as the demand increases the
water temperature drops.
In a variable-capacity system, the amount of heat provided by the heating
element/burner is varied by the
system controller, thus allowing more heat to be applied when the demand
increases, and less heat when
the demand decreases, thereby providing the same output temperature regardless
of the demand.
Although instantaneous water heaters cost more due to their complexity,
typically they are much more
efficient than a standard storage water heater.
Regardless of whether a water heater uses a gas flame or a resistive element
as the heat
source, ultimately the energy required to fuel the heater is a conventional
fossil fuel since few regions in
the world rely on alternative energy sources. As such, water heaters
contribute to the world's
dependence on fossil fuels, an energy source of finite size and limited
regional availability. Dependence
on fossil fuels not only leads to increased vulnerability to potential supply
disruption, but also continued
global warming due to carbon dioxide emissions.
Within recent years there has been considerable research in the area of
alternative fuels
that provide a`green' approach to the development of electricity. Clearly the
benefit of such an
approach, besides combating global warming and lessening the world's
dependence on fossil fuels, is
that the energy provided by the alternative source can then be used to power a
host of conventional
electrically powered devices without requiring any device modification.
Unfortunately, until such an
alternative source is accepted and tied in to the existing power grid, there
is little for the end consumer to
do to lessen their contribution to the world's dependence on fossil fuels
other than to simply lessen their
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overall power consumption. To date, such an approach has had limited success
with most people
refusing to limit their power consumption.
Accordingly, what is needed is a means of helping end users to lower their
power
consumption without requiring actual sacrifice. The present invention, by
providing a high efficiency
on-demand water heater utilizing an alternative heat source, provides such a
system.
SUMMARY OF THE INVENTION
The present invention provides an on-demand water heater and a method of
operating
the same, the water heater including an electrolytic heating subsystem. The
electrolytic heating
subsystem is a pulsed electrolysis system that heats a heat transfer medium
contained within a circulation
conduit. As the heat transfer medium is circulated through the conduit, it
heats an integrated heating
element. When water passes through the on-demand water heater, in response to
user demand, the water
passes through a heat exchange conduit integrated within the water pipe and
positioned in close
proximity to the heating element. As the water passes through the heat
exchange conduit, it becomes
heated. In at least one embodiment, the system is configured to allow cold
water to be mixed with the
hot water, thus providing an additional level of temperature control.
In one embodiment of the invention, the on-demand water heater includes an
electrolytic
heating subsystem comprised of an electrolysis tank, a membrane separating the
electrolysis tank into
two regions, at least one pair of low voltage electrodes, at least one pair of
high voltage electrodes, a low
voltage source, a high voltage source, and means for simultaneously pulsing
both the low voltage source
and the high voltage source. The system is further comprised of a circulation
conduit, a portion of which
is in thermal communication with the electrolytic heating subsystem, a heating
element integrated within
the conduit, and a circulation pump coupled to the circulation conduit. In
close proximity to the heating
element is a heat exchange conduit that is integrated into a hot water supply
pipe. As water passes
through the hot water supply pipe, in response to user demand, the water
becomes heated as it passes
through the heat exchange conduit. The water heater can also include a system
controller that can be
coupled to one or more temperature monitors, the low and high voltage sources,
the pulse generator, the
circulation pump, a water level monitor, flow valves and/or a pH or
resistivity monitor. The water heater
can also include a thermally insulated housing, the housing preferably
surrounding at least the heating
element and the heat exchange conduit. The water heater can also include
means, such as a variable flow
valve, for mixing cold water into the heated water in order to achieve the
desired water temperature. The
water heater can further be comprised of at least one electromagnetic coil
capable of generating a
magnetic field within a portion of the electrolysis tank. The water heater can
further be comprised of at
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least one permanent magnet capable of generating a magnetic field within a
portion of the electrolysis
tank.
In another embodiment of the invention, the on-demand water heater includes an
electrolytic heating subsystem comprised of an electrolysis tank, a membrane
separating the electrolysis
tank into two regions, at least one pair of high voltage electrodes, a
plurality of metal members contained
within the electrolysis tank and interposed between the high voltage
electrodes and the membrane, a high
voltage source, and means for pulsing the high voltage source. The system is
further comprised of a
circulation conduit, a portion of which is in thermal communication with the
electrolytic heating
subsystem, a heating element integrated within the conduit, and a circulation
pump coupled to the
circulation conduit. In close proximity to the heating element is a heat
exchange conduit that is
integrated into a hot water supply pipe. As water passes through the hot water
supply pipe, in response
to user demand, the water becomes heated as it passes through the heat
exchange conduit. The water
heater can also include a system controller that can be coupled to one or more
temperature monitors, the
high voltage source, the pulse generator, the circulation pump, a water level
monitor, flow valves and/or
a pH or resistivity monitor. The water heater can also include a thermally
insulated housing, the housing
preferably surrounding at least the heating element and the heat exchange
conduit. The water heater can
also include means, such as a variable flow valve, for mixing cold water into
the heated water in order to
achieve the desired water temperature. The water heater can further be
comprised of at least one
electromagnetic coil capable of generating a magnetic field within a portion
of the electrolysis tank. The
water heater can further be comprised of at least one permanent magnet capable
of generating a magnetic
field within a portion of the electrolysis tank.
In another aspect of the invention, a method of operating an on-demand water
heater is
provided, the method comprising the steps of heating a heat transfer medium
contained within a
circulation conduit using an electrolytic heating subsystem, circulating the
heated heat transfer medium
through the circulation conduit and a heating element integrated within the
circulation conduit, passing
water through a heat exchange conduit integrated within a water pipe in
response to a demand for hot
water, wherein the heat exchange conduit is proximate the heating element,
heating the water as it passes
through the heat exchange conduit, and suspending the step of passing water
through the heat exchange
conduit when the demand for hot water is terminated. In at least one
embodiment, the method further
comprises the steps of measuring the temperature of the water after it has
passed through the heat
exchange conduit, comparing the measured temperature to a preset temperature,
and mixing cold water
with the hot water if the measured temperature is above the preset
temperature. In at least one other
embodiment, the method further comprises the steps of periodically measuring
the temperature of the
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CA 02613780 2007-12-07
~
electrolysis liquid and/or the heat transfer medium, comparing the measured
temperature with a preset
temperature or temperature range, and modifying at least one process parameter
of the electrolytic
heating subsystem if the measured temperature is outside (lower or higher) of
the preset temperature or
temperature range. In at least one embodiment, the step of heating the heat
transfer medium contained
within the circulation conduit using an electrolytic heating subsystem further
comprises the steps of
applying a low voltage to at least one pair of low voltage electrodes
contained within the electrolysis
tank of the electrolytic heating subsystem and applying a high voltage to at
least one pair of high voltage
electrodes contained within the electrolysis tank, wherein the low voltage and
the high voltage are
simultaneously pulsed. In at least one embodiment, the step of heating the
heat transfer medium
contained within the circulation conduit using an electrolytic heating
subsystem further comprises the
steps of applying a high voltage to at least one pair of high voltage
electrodes contained within the
electrolysis tank, the high voltage applying step further comprising the step
of pulsing said high voltage,
wherein at least one metal member is positioned between the high voltage
anode(s) and the tank
membrane and at least one other metal member is positioned between the high
voltage cathode(s) and the
tank membrane. In at least one embodiment, the method further comprises the
step of generating a
magnetic field within a portion of the electrolysis tank, wherein the magnetic
field affects a heating rate
corresponding to the liquid heating step.
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 providing
additional
control of the output water temperature via cold water mixing;
Fig. 3 illustrates an exemplary embodiment in which the heat transfer medium
contained
within a circulation conduit, a portion of which is in thermal communication
with an electrolytic heating
subsystem, is circulated through the heating element of the on-demand water
heater;
Fig. 4 is a detailed view of an embodiment of the electrolytic heating
subsystem;
Fig. 5 is a detailed view of an alternate embodiment of the electrolytic
heating subsystem
shown in Fig. 4;
Fig. 6 is a detailed view of an alternate embodiment of the electrolytic
heating subsystem
shown in Fig. 4 utilizing an electromagnetic rate controller;
Fig. 7 is a detailed view of an alternate embodiment of the electrolytic
heating subsystem
shown in Fig. 5 utilizing an electromagnetic rate controller as shown in Fig.
6;
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Fig. 8 is a detailed view of an alternate embodiment of the electrolytic
heating subsystem
shown in Fig. 6 utilizing a permanent magnet rate controller;
Fig. 9 is a detailed view of an alternate embodiment of the electrolytic
heating subsystem
shown in Fig. 7 utilizing a permanent magnet rate controller;
Fig. 10 illustrates one method of operating the on-demand water heater of the
invention;
Fig. 11 illustrates an alternate method of system operation;
Fig. 12 illustrates another alternate method of system operation;
Fig. 13 illustrates another alternate method of system operation; and
Fig. 14 illustrates another alternate method of system operation.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
Fig. 1 is an illustration of an exemplary system 100 in accordance with the
invention.
System 100 is comprised of two primary subsystems; on-demand water heater 101
and a pulsed
electrolytic heating subsystem 103. As will be described in detail, there are
numerous configurations of
electrolytic heating subsystem 103 applicable to the invention.
In operation, electrolytic heating subsystem 103 maintains the fluid within
heating
element 107 at a relatively high temperature, typically on the order of at
least 40 - 50 C, more
preferably on the order of 60 - 75 C, and still more preferably on the order
of 75 - 95 C. It some
embodiments, even higher temperatures are used, for example on the order of
100 - 150 C, or on the
order of 150 - 250 C, or on the order of 250 - 350 C. Depending upon the
desired operating
temperature, the fluid selected as the heat transfer medium contained within
heating element 107 and the
coupling conduits, and upon the characteristics (e.g., boiling point) of the
selected medium, subsystem
103, heating element 107 and the coupling conduits may all be designed to
operate at high pressures,
typically at least high enough to prevent medium boiling.
In use, when a demand is placed on the system to supply hot water, for example
when
the end-user turns on a hot water tap, cold water enters through pipe 109,
passes through heat exchange
conduit 111, and exits via pipe 113. Although there are a variety of designs
that can be used both for
heating element 107 and heat exchange conduit 111, in general the intent is to
maximize heat transfer
from element 107, which contains the heated medium, to the water contained
within conduit 111.
Accordingly, heat exchange conduit 1 l 1 and heating element 107 are
preferably positioned in close
proximity to one another, for example intertwined together, and may also
include protrusions (e.g.,
interleaved fins) to augment heat transfer.
In a preferred embodiment of the invention, a system controller 115 controls
the
performance of the system, preferably by varying one or more operating
parameters (i.e., process
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parameters) of electrolytic heating subsystem 103 to which it is attached.
Varying operating parameters
of subsystem 103, for example cycling the subsystem on and off or varying
other operational parameters
as described further below, allows the steady state temperature of the
subsystem and heating element 107
to be maintained at the desired temperature. A temperature monitor 117,
coupled to the heating element
107, allows controller to obtain feedback from the system as the operational
parameters are varied.
Preferably a second temperature monitor 119, coupled to water pipe 113,
monitors the temperature of the
output water to insure that the system is operating as desired. Note that in
the illustrated configuration
in which the heat transfer medium is circulated through conduits 121 by
circulation pump 123, conduits
121 coupling the electrolytic heating subsystem 103 to the heating element
107, preferably pump 123 is
also connected to controller 115.
In at least one embodiment of the invention, heating element 107 and heat
exchange
conduit 111 are contained within a housing 125. In order to maximize system
efficiency while
minimizing the risks (e.g., fire hazard) associated with incorporating the
system into a commercial or
residential structure, preferably electrolytic heating subsystem 103, housing
125, and conduits 121, are
all thermally insulated. In effect, thermally insulated housing 125 creates a
high temperature oven
through which the water pipe, and in particular heat exchange conduit 111,
run.
Although system 100 can be operated as a fixed-capacity system, i.e., a system
which
imparts the same amount of heat to the water flowing through the system
regardless of the volume of
water, preferably it operates as a variable-capacity system. Such a variable-
capacity system can be
achieved by varying the output of electrolytic heating subsystem 103 via
control of its operating
parameters and/or by controlling the flow of the heat transfer medium flowing
through conduits 121 and
heating element 107 (i.e., by utilizing a flow valve or regulating the output
of circulation pump 123).
Alternately and as illustrated in Fig. 2, the invention can be implemented as
a variable-
capacity system by coupling a cold water pipe 201 to hot water output pipe
113. By regulating the
amount of cold water entering hot water pipe 113, the temperature of the hot
water exiting the overall
system can be controlled even though the flow rate, driven by user demand, is
varying. Preferably in
such an embodiment the temperature of the water is monitored both before
(e.g., monitor 119) and after
(e.g., monitor 203) the point at which cold water pipe 201 is coupled to hot
water pipe 113. A variable
flow valve 205 or other means is used to control the flow of cold water into
hot water pipe 113, flow
valve 205 preferably under the control of system controller 115. In at least
one embodiment of the
invention, output water temperature control is achieved by a combination of
controlling the output of the
electrolytic heating subsystem and/or the flow of heat transfer medium through
heating element 107
and/or the amount of cold water mixed into the hot water through secondary
water input pipe 201.
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Fig. 3 illustrates the preferred means used to remove heat from electrolytic
heating
subsystem 103 in order to heat the water that passes from cold water inlet 109
to hot water outlet 113. It
should be understood that although these features are illustrated relative to
system 200, they are equally
applicable to system 100.
In the embodiment illustrated in Fig. 3, portion 301 of conduit 121 is
contained within
the electrolysis tank, or mounted around the electrolysis tank, or integrated
within the walls of the
electrolysis tank. It will be appreciated that conduit portion 301 can either
be a separate conduit that is
coupled to conduit 121, or simply a portion of conduit 121. The primary
considerations for the location
of portion 301 of conduit 121 are (i) the efficiency of the thermal
communication between the
electrolytic heating subsystem and the conduit (and heat transfer medium
contained therein) and (ii)
minimization of conduit erosion. As most materials used for the electrolysis
tank are poor thermal
conductors, typically conduit 301 is either contained within the tank or
integrated within the tank walls.
During electrolysis, the heat generated by the process heats the heat transfer
medium contained within
conduit portion 301 which is then passed, via conduit 121, to heating element
107. Heating element 107
then, in turn, heats the water passing through pipes 109/113 and, in
particular, the water passing through
heat exchange conduit I 11.
Particulars of the electrolytic heating subsystem will now be provided. Fig. 4
is an
illustration of a preferred embodiment of an electrolytic heating subsystem
400. Note that in Figs. 4-9
only a portion of conduit 301 is shown (conduit 617 in Figs. 6-9), thus
allowing a better view of the
underlying electrolytic subsystem. Additionally, for illustration clarity, the
portions of conduit 301 (or
conduit 617) that are included are shown mounted to the exterior surface of
the electrolysis tank even
though as previously noted, conduit 301 is typically integrated within the
tank walls or mounted within
the tank, thereby improving on the transfer of heat from the electrolytic
subsystem to the heat transfer
medium contained within the conduit.
Tank 401 is comprised of a non-conductive material. The size of tank 401 is
primarily
selected on the basis of desired system output, i.e., the level of desired
heat, which at least in part is
based on the expected flow rates for the on-demand heater 101. Although tank
401 is shown as having a
rectangular shape, it will be appreciated that the invention is not so limited
and that tank 401 can utilize
other shapes, for example cylindrical, square, irregularly-shaped, etc. Tank
401 is substantially filled
with medium 403. In at least one preferred embodiment, liquid 403 is comprised
of water, or more
preferably water with an electrolyte, the electrolyte being an acid
electrolyte, a base electrolyte, or a
combination of an acid electrolyte and a base electrolyte. Exemplary
electrolytes include potassium
hydroxide and sodium hydroxide. The term "water" as used herein refers to
water (H20), deuterated
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water (deuterium oxide or D20), tritiated water (tritium oxide or T20),
semiheavy water (HDO), heavy
oxygen water (HZ180 or H2 170) 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. Subsystem 103,
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 401 into two regions is a membrane 405. Membrane 405 permits
ion/electron exchange between the two regions of tank 401. Assuming medium 403
is water, as
preferred, small amounts of hydrogen and oxygen are produced during operation.
Accordingly
membrane 405 also keeps the oxygen and hydrogen bubbles produced during
electrolysis separate, thus
minimizing the risk of inadvertent recombination of the two gases. Exemplary
materials for membrane
405 include, but are not limited to, polypropylene, tetrafluoroethylene,
asbestos, etc. Preferably tank 401
also includes a pair of gas outlets 407 and 409, corresponding to the two
regions of tank 401. The
volume of gases produced by the process can either be released, through
outlets 407 and 409, into the
atmosphere in a controlled manner or they can be collected and used for other
purposes.
As the electrolytic heating subsystem is designed to reach relatively high
temperatures,
the materials comprising tank 401, membrane 405 and other subsystem components
are selected on the
basis of their ability to withstand the expected temperatures and pressures.
As previously noted, the
subsystem can be designed to operate at temperatures ranging from 40 C to 350
C or higher.
Additionally, at elevated temperatures higher pressures are typically required
to prevent boiling of liquid
403. Accordingly, it will be understood that the choice of materials for the
subsystem components and
the design of the subsystem (e.g., tank wall thicknesses, fittings, etc.) will
vary, depending upon the
intended subsystem operational parameters, primarily temperature and pressure.
Replenishment of medium 405 can be through one or more dedicated lines. Fig. 4
shows
a portion of two such conduits, conduit 411 and 413, one coupled to each of
the regions of tank 401.
Alternately, a replenishment conduit can be coupled to only one region of tank
401. Although medium
replenishment can be performed manually, preferably replenishment is performed
automatically, for
example using system controller 115 and flow valve 415 within line 411 and
valve 417 within line 413.
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Replenishment can be performed periodically or continually at a very low flow
rate. If periodic
replenishment is used, it can either be based on the period of system
operation, for example replenishing
the system with a predetermined volume of medium after a preset number of
hours of operation, or based
on the volume of medium within tank 401, the volume being provided to
controller 115 using a level
monitor 419 within the tank or other means. In at least one preferred
embodiment system controller 115
is also coupled to a monitor 421, monitor 421 providing either the pH or the
resistivity of liquid 403
within the electrolysis tank, thereby providing means for determining when
additional electrolyte needs
to be added. In at least one preferred embodiment system controller 115 is
also coupled to a temperature
monitor 423, monitor 423 providing the temperature of the electrolysis medium.
In at least one embodiment of the electrolytic heating subsystem, two types of
electrodes
are used, each type of electrode being comprised of one or more electrode
pairs with each electrode pair
including at least one cathode (i.e., a cathode coupled electrode) and at
least one anode (i.e., an anode
coupled electrode). All cathodes, regardless of the type, are kept in one
region of tank 401 while all
anodes, regardless of the type, are kept in the other tank region, the two
tank regions separated by
membrane 405. In the embodiment illustrated in Fig. 4, each type of electrode
includes a single pair of
electrodes.
The first type of electrodes, electrodes 425/427, are coupled to a low voltage
source 429.
The second type of electrodes, electrodes 431/433, are coupled to a high
voltage source 435. In the
illustrations and as used herein, voltage source 429 is labeled as a`low'
voltage source not because of the
absolute voltage produced by the source, but because the output of voltage
source 429 is maintained at a
lower output voltage than the output of voltage source 435. Preferably and as
shown, the individual
electrodes of each pair of electrodes are parallel to one another; i.e., the
face of electrode 425 is parallel
to the face of electrode 427 and the face of electrode 431 is parallel to the
face of electrode 433. It
should be appreciated, however, that such an electrode orientation is not
required.
In one preferred embodiment, electrodes 425/427 and electrodes 431/433 are
comprised
of titanium. In another preferred embodiment, electrodes 425/427 and
electrodes 431/433 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 low and high voltage
electrodes. Additionally, the same
material does not have to be used for both the anode(s) and the cathode(s) of
the low voltage electrodes,
nor does the same material have to be used for both the anode(s) and the
cathode(s) of the high voltage
electrodes. In addition to titanium and stainless steel, other exemplary
materials that can be used for the
low voltage and high voltage electrodes include, but are not limited to,
copper, iron, steel, cobalt,
manganese, zinc, nickel, platinum, palladium, aluminum, lithium, magnesium,
boron, carbon, graphite,
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carbon-graphite, metal hydrides and alloys of these materials. Preferably the
surface area of the faces of
the low voltage electrodes (e.g., electrode 425 and electrode 427) cover a
large percentage of the cross-
sectional area of tank 401, typically on the order of at least 40 percent of
the cross-sectional area of tank
401, and more typically between approximately 70 percent and 90 percent of the
cross-sectional area of
tank 401. Preferably the separation between the low voltage electrodes (e.g.,
electrodes 425 and 427) is
between 0.1 millimeters and 15 centimeters. In at least one embodiment the
separation between the low
voltage electrodes is between 0.1 millimeters and 1 millimeter. In at least
one other embodiment the
separation between the low voltage electrodes is between 1 millimeter and 5
millimeters. In at least one
other embodiment the separation between the low voltage electrodes is between
5 millimeters and 2
centimeters. In at least one other embodiment the separation between the low
voltage electrodes is
between 5 centimeters and 8 centimeters. In at least one other embodiment the
separation between the
low voltage electrodes is between 10 centimeters and 12 centimeters.
In the illustrated embodiment, electrodes 431/433 are positioned outside of
the planes
containing electrodes 425/427. In other words, the separation distance between
electrodes 431 and 433
is greater than the separation distance between electrodes 425 and 427 and
both low voltage electrodes
are positioned between the planes containing the high voltage electrodes. The
high voltage electrodes
may be larger, smaller or the same size as the low voltage electrodes.
As previously noted, the voltage applied to the high voltage electrodes is
greater than
that applied to the low voltage electrodes. Preferably the ratio of the high
voltage to the low voltage
applied to the high voltage and low voltage electrodes, respectively, is at
least 5:1, more preferably the
ratio is between 5:1 and 100:1, still more preferably the ratio is between 5:1
and 33:1, and even still more
preferably the ratio is between 5:1 and 20:1. Preferably the high voltage
generated by source 435 is
within the range of 50 volts to 50 kilovolts, more preferably within the range
of 100 volts to 5 kilovolts,
and still more preferably within the range of 500 volts to 2.5 kilovolts.
Preferably the low voltage
generated by source 429 is within the range of 3 volts to 1500 volts, more
preferably within the range of
12 volts to 750 volts, still more preferably within the range of 24 volts to
500 volts, and yet still more
preferably within the range of 48 volts to 250 volts.
Rather than continually apply voltage to the electrodes, sources 429 and 435
are pulsed,
preferably at a frequency of between 50 Hz and 1 MHz, more preferably at a
frequency of between 100
Hz and 10 kHz, and still more preferably at a frequency of between 150 Hz and
7 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 0.1 and 50 percent of the time period
defined by the frequency,
and still more preferably between 0.1 and 25 percent of the time period
defined by the frequency. Thus,
CA 02613780 2007-12-07
for example, for a frequency of 150 Hz, the pulse duration is preferably in
the range of 0.67
microseconds to 5 milliseconds, more preferably in the range of 6.67
microseconds to 3.3 milliseconds,
and still more preferably in the range of 6.67 microseconds to 1.7
milliseconds. Alternately, for
example, for a frequency of I kHz, the pulse duration is preferably in the
range of 0.1 microseconds to
0.75 milliseconds, more preferably in the range of I microsecond to 0.5
milliseconds, and still more
preferably in the range of 1 microsecond to 0.25 milliseconds. Additionally,
the voltage pulses are
applied simultaneously to the high voltage and low voltage electrodes via
sources 429 and 435,
respectively. In other words, the voltage pulses applied to high voltage
electrodes 431/433 coincide with
the pulses applied to low voltage electrodes 425/427. Although voltage sources
429 and 435 can include
internal means for pulsing the respective outputs from each source, preferably
an external pulse generator
437 controls a pair of switches, i.e., low voltage switch 439 and high voltage
switch 441 which, in tum,
control the output of voltage sources 429 and 435 as shown, and as described
above.
In at least one preferred embodiment, the frequency and/or pulse duration
and/or low
voltage and/or high voltage can be changed by system controller 115 during
system operation, thus
allowing the operation of the electrolytic heating subsystem to be controlled.
For example, in the
configuration shown in Fig. 4, low voltage power supply 429, high voltage
power supply 435 and pulse
generator 437 are all connected to system controller 115, thus allowing
controller 115 to control the
amount of heat generated by the electrolytic heating subsystem. It will be
appreciated that both power
supplies and the pulse generator do not have to be connected to system
controller 115 to provide heat
generation control. For example, only one of the power supplies and/or the
pulse generator can be
connected to controller 115.
As will be appreciated by those of skill in the art, there are numerous minor
variations of
the electrolytic heating subsystem described above and shown in Fig. 4 that
can be used with the
invention. For example, and as previously noted, altemate configurations can
utilize tanks of different
size and/or shape, different electrolytic solutions, and a variety of
different electrode configurations and
materials. Exemplary alternate electrode configurations include, but are not
limited to, multiple low
voltage cathodes, multiple low voltage anodes, multiple high voltage cathodes,
multiple high voltage
anodes, multiple low voltage electrode pairs combined with multiple high
voltage electrode pairs,
electrodes of varying size or shape (e.g., cylindrical, curved, etc.), and
electrode pairs of varying
orientation (e.g., non-parallel faces, pairs in which individual electrodes
are not positioned directly across
from one another, etc.). Additionally, alternate configurations can utilize a
variety of input powers, pulse
frequencies and pulse durations as previously noted.
11
CA 02613780 2007-12-07
In an exemplary embodiment of the electrolytic heating subsystem, a
cylindrical
chamber measuring 125 centimeters long with an inside diameter of 44
centimeters and an outside
diameter of 50 centimeters was used. The tank contained 175 liters of water,
the water including a
potassium hydroxide (KOH) electrolyte at a concentration of 0.1 % by weight.
The low voltage
electrodes were 75 centimeters by 30 centimeters by 0.5 centimeters and had a
separation distance of
approximately 10 centimeters. The high voltage electrodes were 3 centimeters
by 2.5 centimeters by 0.5
centimeters and had a separation distance of approximately 32 centimeters.
Both sets of electrodes were
comprised of titanium. The pulse frequency was maintained at 150 Hz and the
pulse duration was
initially set to 260 microseconds and gradually lowered to 180 microseconds
during the course of a 4
hour run. The low voltage supply was set to 50 volts, drawing a current of
between 5.5 and 7.65 amps,
and the high voltage supply was set to 910 volts, drawing a current of between
2.15 and 2.48 amps. The
initial temperature was 28 C and monitored continuously with a pair of
thermocouples, one in each side
of the tank. After conclusion of the 4 hour run, the temperature of the tank
fluid had increased to 67 C.
Illustrating the correlation between electrode size and heat production
efficiency, the
high voltage electrodes of the previous test were replaced with larger
electrodes, the larger electrodes
measuring 9.5 centimeters by 5 centimeters by 0.5 centimeters, thus providing
approximately 6.3 times
the surface area of the previous high voltage electrodes. The larger
electrodes, still operating at a voltage
of 910 volts, drew a current of between 1.73 and 1.9 amps. The low voltage
supply was again set at 50
volts, in this run the low voltage electrodes drawing between 0.6 and 1.25
amps. Although the pulse
frequency was still maintained at 150 Hz, the pulse duration was lowered from
an initial setting of 60
microseconds to 15 microseconds. All other operating parameters were the same
as in the previous test.
In this test, during the course of a 5 hour run, the temperature of the tank
fluid increased from 28 C to
69 C. Given the shorter pulses and the lower current, this test with the
larger high voltage electrodes
exhibited a heat production efficiency approximately 8 times that exhibited in
the previous test.
Fig. 5 is an illustration of a second exemplary embodiment of the electrolytic
heating
subsystem, this embodiment using a single type of electrodes. Subsystem 500 is
basically the same as
subsystem 400 shown in Fig. 4 with the exception that low voltage electrodes
425/427 have been
replaced with a pair of metal members 501/503; metal member 501 interposed
between high voltage
electrode 431 and membrane 405 and metal member 503 interposed between high
voltage electrode 433
and membrane 405. The materials comprising metal members 501/503 are the same
as those of the low
voltage electrodes. Preferably the surface area of the faces of members 501
and 503 is a large percentage
of the cross-sectional area of tank 401, typically on the order of at least 40
percent, and often between
approximately 70 percent and 90 percent of the cross-sectional area of tank
401. Preferably the
12
CA 02613780 2007-12-07
separation between members 501 and 503 is between 0.1 millimeters and 15
centimeters. In at least one
embodiment the separation between the metal members is between 0.1 millimeters
and 1 millimeter. In
at least one other embodiment the separation between the metal members is
between I millimeter and 5
millimeters. In at least one other embodiment the separation between the metal
members is between 5
millimeters and 2 centimeters. In at least one other embodiment the separation
between the metal
members is between 5 centimeters and 8 centimeters. In at least one other
embodiment the separation
between the metal members is between 10 centimeters and 12 centimeters. The
preferred ranges for the
size of the high voltage electrodes as well as the high voltage power, pulse
frequency and pulse duration
are the same as in the exemplary subsystem shown in Fig. 4 and described
above.
In a test of the exemplary embodiment of the electrolytic heating subsystem
using metal
members in place of low voltage electrodes, the same cylindrical chamber and
electrolyte-containing
water was used as in the previous test. The metal members were 75 centimeters
by 30 centimeters by 0.5
centimeters and had a separation distance of approximately 10 centimeters. The
high voltage electrodes
were 3 centimeters by 2.5 centimeters by 0.5 centimeters and had a separation
distance of approximately
32 centimeters. The high voltage electrodes and the metal members were
fabricated from stainless steel.
The pulse frequency was maintained at 150 Hz and the pulse duration was
initially set to 250
microseconds and gradually lowered to 200 microseconds during the course of a
2 hour run. The high
voltage supply was set to 910 volts, drawing a current of between 2.21 and
2.45 amps. The initial
temperature was 30 C and monitored continuously with a pair of thermocouples,
one in each side of the
tank. After conclusion of the 2 hour run, the temperature of the tank fluid
had increased to 60 C.
As with the previously described set of tests, the correlation between
electrode size and
heat production efficiency was demonstrated by replacing the high voltage
electrodes with larger
electrodes measuring 9.5 centimeters by 5 centimeters by 0.5 centimeters. The
larger electrodes, still
operating at a voltage of 910 volts, drew a current of between 1.6 and 1.94
amps. The pulse frequency
was still maintained at 150 Hz, however, the pulse duration was lowered from
an initial setting of 90
microseconds to 25 microseconds. All other operating parameters were the same
as in the previous test.
In this test during the course of a 6 hour run, the temperature of the tank
fluid increased from 23 C to
68 C, providing an increase in heat production efficiency of approximately 3
times over that exhibited in
the previous test.
As with the previous exemplary embodiment, it will be appreciated that there
are
numerous minor variations of the electrolytic heating subsystem described
above and shown in Fig. 5
that can be used with the invention. For example, and as previously noted,
altecnate configurations can
utilize tanks of different size and/or shape, different electrolytic
solutions, and a variety of different
13
CA 02613780 2007-12-07
electrode/metal member configurations and materials. Exemplary alternate
electrode/metal member
configurations include, but are not limited to, multiple sets of metal
members, multiple high voltage
cathodes, multiple high voltage anodes, multiple sets of metal members
combined with multiple high
voltage cathodes and anodes, electrodes/metal members of varying size or shape
(e.g., cylindrical,
curved, etc.), and electrodes/metal members of varying orientation (e.g., non-
parallel faces, pairs in
which individual electrodes are not positioned directly across from one
another, etc.). Additionally,
alternate configurations can utilize a variety of input powers, pulse
frequencies and pulse durations.
In at least one preferred embodiment of the invention, the electrolytic
heating subsystem
uses a reaction rate controller to help achieve optimal performance of the
heating subsystem relative to
the water heater. The rate controller operates by generating a magnetic field
within the electrolysis tank,
either within the region between the high voltage cathode(s) and the low
voltage cathode(s) or metal
member(s), or within the region between the high voltage anode(s) and the low
voltage anode(s) or metal
member(s), or both regions. The magnetic field can either be generated with an
electromagnetic coil or
coils, or with one or more permanent magnets. The benefit of using
electromagnetic coils is that the
intensity of the magnetic field generated by the coil or coils can be varied
by controlling the current
supplied to the coil(s), thus providing a convenient method of controlling the
reaction rate.
Fig. 6 provides an exemplary embodiment of an electrolytic heating subsystem
600 that
includes an electromagnetic rate controller. It should be understood that the
electromagnetic rate
controller shown in Figs. 6 and 7, or the rate controller using permanent
magnets shown in Figs. 8 and 9,
is not limited to a specific tank/electrode configuration. For example,
electrolysis tank 601 of system
600 is cylindrically-shaped although the tank could utilize other shapes such
as the rectangular shape of
tank 401. As in the previous embodiments, the electrolytic heating subsystem
includes a membrane
(e.g., membrane 603) separating the tank into two regions, a pair of gas
outlets (e.g., outlets 605/607),
medium replenishment conduits 609 and 611 (one per region in the exemplary
embodiment illustrated in
Fig. 6), flow control valves (e.g., valves 613 and 615) coupled to the system
controller, and heat removal
conduits (e.g., conduits 617 which are functional equivalents to conduits
301). As in the embodiments
shown in Figs. 4 and 5, only a portion of the conduits are shown, thus
providing a better view of the
underlying system. Preferably the system also includes a water level monitor
(e.g., monitor 619), a pH
or resistivity monitor (e.g., monitor 621), and a temperature monitor 623.
This embodiment, similar to
the one shown in Fig. 4, utilizes both low voltage and high voltage
electrodes. Specifically, subsystem
600 includes a pair of low voltage electrodes 625/627 and a pair of high
voltage electrodes 629/631.
In the electrolytic heating subsystem illustrated in Fig. 6, a magnetic field
of controllable
intensity is generated between the low voltage and high voltage electrodes
within each region of tank
14
CA 02613780 2007-12-07
601. Although a single electromagnetic coil can generate fields within both
tank regions, in the
illustrated embodiment the desired magnetic fields are generated by a pair of
electromagnetic coils
633/635. As shown, electromagnetic coi1633 generates a magnetic field between
the planes containing
low voltage electrode 625 and high voltage electrode 629 and electromagnetic
coil 635 generates a
magnetic field between the planes containing low voltage electrode 627 and
high voltage electrode 631.
Electromagnetic coils 633/635 are coupled to a controller 637 which is used to
vary the current through
coils 633/635, thus allowing the strength of the magnetic field generated by
the electromagnetic coils to
be varied as desired. As a result, the rate of the reaction driven by the
electrolysis system, and thus the
amount of heat generated by the subsystem, can be controlled. In particular,
increasing the magnetic
field generated by coils 633/635 decreases the reaction rate. Accordingly, a
maximum reaction rate is
achieved with no magnetic field while the minimum reaction rate is achieved by
imposing the maximum
magnetic field. It will be appreciated that the exact relationship between the
magnetic field and the
reaction rate depends on a variety of factors including reaction strength,
electrode composition and
configuration, voltage/pulse frequency/pulse duration applied to the
electrodes, electrolyte concentration,
and achievable magnetic field, the last parameter dependent primarily upon the
composition of the coils,
the number of coil turns, and the current available from controller 637.
Although the subsystem embodiment shown in Fig. 6 utilizes coils that are
interposed
between the low voltage electrode and the high voltage electrode planes, it
will be appreciated that the
critical parameter is to configure the system such that there is a magnetic
field, preferably of controllable
intensity, between the low voltage and high voltage electrode planes. Thus,
for example, if the coils
extend beyond either, or both, the plane containing the low voltage
electrode(s) and the plane controlling
the high voltage electrode(s), the system will still work as the field
generated by the coils includes the
regions between the low voltage and high voltage electrodes. Additionally it
will be appreciated that
although the embodiment shown in Fig. 6 utilizes a single controller 637
coupled to both coils, the
system can also utilize separate controllers for each coil (not shown).
Similarly, while the illustrated
subsystem utilizes dual coils, the invention can also use a single coil to
generate a single field which
affects both tank regions, or primarily affects a single tank region.
Additionally it will be appreciated
that the electromagnetic coils do not have to be mounted to the exterior
surface of the tank as shown in
Fig. 6. For example, the electromagnetic coils can be integrated within the
walls of the tank, or mounted
within the tank. By mounting the electromagnetic coils within, or outside, of
the tank walls, coil
deterioration from electrolytic erosion is minimized.
The magnetic field rate controller is not limited to use with electrolytic
heating
subsystems employing both low and high voltage electrodes. For example, the
electromagnetic rate
CA 02613780 2007-12-07
controller subsystem can be used with embodiments using high voltage
electrodes and metal members as
described above and shown in the exemplary embodiment of Fig. 5. Fig. 7 is an
illustration of an
exemplary embodiment based on the embodiment shown in Fig. 6, replacing low
voltage electrodes
625/627 with metal members 701/703, respectively. As with the electromagnetic
rate controller used
with the dual voltage system, it will be appreciated that configurations using
high voltage electrodes and
metal members can utilize intemal electromagnetic coils, electromagnetic coils
mounted within the tank
walls, and electromagnetic coils mounted outside of the tank walls.
Additionally, and as previously
noted, the electromagnetic rate controller is not limited to a specific tank
and/or electrode configuration.
As previously noted, although electromagnetic coils provide a convenient means
for
controlling the intensity of the magnetic field applied to the reactor,
permanent magnets can also be used
with the electrolytic heating subsystem of the invention, for example when the
magnetic field does not
need to be variable. Figs. 8 and 9 illustrate embodiments based on the
configurations shown in Figs. 6
and 7, but replacing coils 633 and 635 with permanent magnets 801 and 803,
respectively. Note that in
the view of Fig. 8, only a portion of electrode 625 is visible while none of
electrode 631 is visible.
Similarly in the view of Fig. 9, only a portion of metal member 701 is visible
while none of electrode
631 is visible.
As previously described, the water heating system of the invention can be
operated in a
variety of ways, depending primarily upon the desired level of system control.
Further detail regarding
the primary and preferred methodologies will now be provided.
In the simplest method of use, electrolytic heating subsystem 103 is operated
on a
continuous basis (step 1001 of Fig. 10). In a configuration such as that shown
in Fig. 3, pumping of the
heat transfer fluid is also preferably continuous (step 1003). When the user
requires hot water (step
1005), as evidenced by turning on a hot water tap, water flows through the
water pipe (e.g., pipe 109)
and through the heat exchange conduit 111 (step 1007). As the water passes
through the heat exchange
conduit it becomes heated due to the proximity of the heat exchange conduit to
the heating element, e.g.,
element 107 (step 1009). Hot water is then supplied to the end user (step
1011) until the demand for hot
water ends (step 1013), at which time water flow through the water pipe and
the heat exchange conduit is
suspended (step 1015).
Fig. 11 illustrates an alternate method similar to that shown in Fig. 10 with
the exception
of the continuous pumping step (step 1003). As shown, in this method the heat
transfer medium is not
pumped continuously, rather it is only pumped after there has been a hot water
demand placed on the
system (step 1005). Accordingly, after the hot water demand, the heat transfer
medium is pumped
through the heating element (step 1101). Once again, as the water passes
through the heat exchange
16
CA 02613780 2007-12-07
conduit it becomes heated due to the proximity of the heat exchange conduit to
the heating element (step
1009). Hot water is then supplied to the end user (step 1011) until the demand
for hot water ends (step
1013), at which time water flow through the water pipe and the heat exchange
conduit is suspended (step
1015) as is pumping of the heat transfer medium (step 1103).
Fig. 12 illustrates an alternate method providing further control over the
temperature of
the hot water as described above relative to Fig. 2. In general, the steps are
the same as shown in Fig. 10
except for the inclusion of additional steps to monitor and adjust the
temperature of the hot water
supplied by the system. More specifically, after the water is heated (step
1009), the temperature of the
water exiting the on-demand heater is determined (step 1201), for example
using temperature monitor
119. This temperature is compared by the system controller to a preset
temperature (step 1203), the pre-
set temperature preferably set by the end user using a thermostat coupled to
the system controller. If the
temperature is acceptable (step 1205), hot water is supplied (step 1011) until
the hot water demand is
terminated (step 1013), causing water flow through pipe 109 and heat exchange
conduit 111 to be
suspended (step 1015). If the temperature is too hot (step 1207), cold water
is mixed with the hot water
(step 1209). The temperature of the water leaving this mixing region is then
determined (step 1211), for
example using temperature monitor 203. The post-mix water temperature is then
compared to the preset
temperature (step 1213). If the temperature is acceptable (step 1215), hot
water is supplied (step 1011)
until the hot water demand is terminated (step 1013), causing water flow
through pipe 109 and heat
exchange conduit 111 to be suspended (step 1015). If the temperature of the
post-mix water is still not
acceptable (step 1217), further adjustment of the ratio of cold water to hot
water is made (step 1209) until
the temperature becomes acceptable (step 1215).
Fig. 13 illustrates the methodology shown in Fig. 12 combined with the heat
transfer
medium pumping regimen of Fig. 11.
As previously described, if desired the system can be configured to adjust the
operating
parameters of the electrolytic heating subsystem during operation, for example
based on the temperature
of heating element 107. This type of control can be used, for example, to
insure that the temperature of
heating element 107 does not exceed a preset temperature or that the
temperature of heating element 107
remains within a preset range, even if the system output varies with age.
Typically this type of process
modification occurs periodically; for example the system can be configured to
execute a system
performance self-check every 30 minutes or at some other time interval. As
process modification is used
to optimize the system, it will be appreciated that it is done in addition to,
not as a replacement for, the
processes described relative to Figs. 10-13.
17
CA 02613780 2007-12-07
Fig. 14 illustrates a preferred method of modifying the output of the
electrolytic heating
subsystem. In this aspect of operation, periodically the system undergoes self-
checking and self-
modification (step 1401). In the first step, the temperature of heating
element 107 or another
representative region of the system is determined (step 1403). The measured
temperature is then
compared to a preset temperature (step 1405), the preset temperature set by
the end-user, the installer, or
the manufacturer. If the temperature is within the preset temperature range
(step 1407), the system
simply goes back to standard operation until the system determines that it is
time for another system
check. If the measured temperature falls outside of the preset range (step
1409), the electrolysis process
is modified (step 1411). During the electrolysis process modification step,
i.e., step 1411, one or more
process parameters are varied. Exemplary process parameters include pulse
duration, pulse frequency,
system power cycling, electrode voltage, and, if the system includes an
electromagnetic rate control
system, the intensity of the magnetic field. Preferably during the
electrolysis modification step, the
system controller modifies the process in accordance with a series of pre-
programmed changes, for
example altering the pulse duration in 10 microsecond steps until the desired
temperature is reached.
Since varying the electrolysis process does not have an immediate affect on
the monitored temperature,
preferably after making a system change a period of time is allowed to pass
(step 1413), thus allowing
the system to reach equilibrium, or close to equilibrium, before determining
if further process
modification is required. During this process, the system controller continues
to monitor the temperature
of the heating element or another temperature associated with the electrolytic
heating subsystem as
previously disclosed (step 1415) while determining if further system
modification is required (step 1417)
by continuing to compare the monitored temperature with the preset
temperature. Once the temperature
reaches an acceptable level (step 1419), the system goes back to standard
operation.
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.
18
