Note: Descriptions are shown in the official language in which they were submitted.
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Title: SOLAR ENERGY WATER HEATING SYSTEM, NETWORK AND
METHOD
FIELD OF THE INVENTION
[0001] The present invention relates to a solar energy water heating
system, network and method, particularly to a solar energy water heating
system that heats water using a combination of solar energy and a non-solar
heating system, and more particularly to a solar energy water heating system
that heats water using a combination of solar energy and an electric heating
system.
BACKGROUND OF THE INVENTION
[0002] In homes, other residential buildings, commercial buildings and
industrial buildings, a hot water tank is typically provided so that hot water
is
readily available for use by a user for a variety of purposes. A heating
system
that may be powered by electricity, natural gas, oil, propane or by some other
means is provided for heating water in the tank. The heating system, however,
can be expensive to operate due to the cost of electricity or fuel. Some
systems have been proposed that incorporate solar energy collectors for the
purposes of heating water in the hot water tank. Such systems, however, may
include a non-solar heating system, such as an electric heating system, but
may lack control over the non-solar heating system, and may also lack the
ability to determine the savings achieved by the use of the solar energy
collector.
[0003] It would be advantageous to provide a solar energy water heating
system that overcomes one or more of the problems described above.
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SUMMARY OF THE INVENTION
[0004] In one aspect, the invention is directed to a solar energy water
heating system for heating water in a water storage tank. In one particular
embodiment, the system includes a controller, a solar energy collector whose
energy contribution to water in the tank is controlled by the controller, and
a
non-solar heating system that is not controlled by the controller. Water in
the
tank may be heated by one or both of the non-solar heating system and energy
from the solar energy collector. The controller can determine the amount of
energy contributed by solar energy to the water in the tank. In another
embodiment, the solar energy water heating system incorporates a controller
that controls both the operation of the pump and the operation of the non-
solar
heating system. In another embodiment, a network of solar energy water
heating systems is provided.
[0005] In a first embodiment, the invention is directed to a solar energy
water heating system comprising a water storage tank, a non-solar heating
system configured to heat water in the water storage tank, a thermostat
positioned to sense the temperature indicative of the temperature of water in
the water storage tank, a solar energy collector, a heat exchanger, a first
fluid
circuit between the solar energy collector and the heat exchanger, a pump
configured to pump fluid through the first fluid circuit, a second fluid
circuit
between the water storage tank and the heat exchanger, and a controller. The
second fluid circuit is fluidically connectable to a water source. The heat
exchanger is configured to transfer heat from fluid in the first fluid circuit
to
water in the second fluid circuit. The thermostat is operatively connected to
the
non-solar heating system. The controller is configured to control the
operation
of the pump. The controller is further configured to receive non-solar heating
system state signals indicative of whether the non-solar heating system is on
and is configured to determine the amount of energy transferred from the solar
energy collector to water in the water storage tank based at least in part on
the
non-solar heating system state signals.
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[0006] In a second embodiment, the invention is directed to a solar
energy water heating system comprising a water storage tank, a non-solar
heating system configured to heat water in the water storage tank, a solar
energy collector, a heat exchanger, a first fluid circuit between the solar
energy
collector and the heat exchanger, a pump configured to pump fluid through the
first fluid circuit, a second fluid circuit between the water storage tank and
the
heat exchanger, a storage tank water temperature sensor, and a controller.
The second fluid circuit is fluidically connectable to a water source. The
heat
exchanger is configured to transfer heat from fluid in the first fluid circuit
to
water in the second fluid circuit. The controller is configured to receive
signals
from the storage tank water temperature sensor indicative of the temperature
of
water in the water storage tank. The controller is configured to prevent
operation of the pump if the signals from the storage tank water temperature
sensor indicate the temperature of water in the water storage tank exceeds a
predetermined high storage tank water temperature.
[0007] In a third embodiment, the invention is directed to a solar energy
water heating system comprising a water storage tank, a solar energy
collector,
a heat exchanger, a first fluid circuit between the solar energy collector and
the
heat exchanger, a pump configured to pump fluid through the first fluid
circuit, a
second fluid circuit between the water storage tank and the heat exchanger, a
solar energy collector temperature sensor positioned to sense temperature
indicative of the temperature of the solar energy collector, a source water
temperature sensor positioned to sense temperature indicative of the
temperature of water from the water source and a controller. The second fluid
circuit is fluidically connectable to a water source. The heat exchanger is
configured to transfer heat from fluid in the first fluid circuit to water in
the
second fluid circuit. The controller is configured to receive solar energy
collector temperature sensor signals from the solar energy collector
temperature sensor and source water temperature sensor signals from the
source water temperature sensor. The controller is further configured to
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prevent operation of the pump if either the solar energy collector temperature
sensor signals indicate a solar energy collector temperature that is below a
predetermined low solar energy collector temperature or if the source water
temperature sensor signals indicate a source water temperature that is below a
predetermined low source water temperature.
[0008] In a fourth embodiment, the invention is directed to a solar energy
water heating system comprising a water storage tank, a non-solar heating
system configured to heat water from the water storage tank, a solar energy
collector, a heat exchanger, a first fluid circuit between the solar energy
collector and the heat exchanger, a pump configured to pump fluid through the
first fluid circuit, a second fluid circuit between the water storage tank and
the
heat exchanger, and a controller configured to control the operation of the
pump and the non-solar heating system. The heat exchanger is configured to
transfer heat from fluid in the first fluid circuit to water in the second
fluid circuit.
The second fluid circuit is fluidically connectable to a water source.
[0009] In a fifth embodiment, the invention is directed to a solar energy
water heating system for operation with a first water storage tank and a non-
solar heating system configured to heat water from the first water storage
tank.
The system comprises a second water storage tank having a second water
storage tank consumption outlet that is fluidically connectable to an inlet on
the
first water storage tank, a solar energy collector, a heat exchanger, a first
fluid
circuit between the solar energy collector and the heat exchanger, a pump
configured to pump fluid through the first fluid circuit, a second fluid
circuit
between the second water storage tank and the heat exchanger, and a
controller configured to control the operation of the pump and the non-solar
heating system. The heat exchanger is configured to transfer heat from fluid
in
the first fluid circuit to water in the second fluid circuit. The second fluid
circuit
is fluidically connectable to a water source.
[0010] In a sixth embodiment, the invention is directed to a method of
heating water in a water storage tank, comprising:
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a) selecting at least one heating means from a group of heating means
including a non-solar heating system and a solar energy collector; and
b) heating water in the water storage tank using the selected heating
means based at least in part on the temperature of water in the water storage
tank.
[0011] In a seventh embodiment, the invention is directed to a network of
solar energy water heating systems, comprising a central control system, and a
plurality of solar energy water heating systems. Each system includes a water
storage tank, a non-solar heating system configured to heat water from the
water storage tank, a solar energy collector, a heat exchanger, a first fluid
circuit between the solar energy collector and the heat exchanger, a pump
configured to pump fluid through the first fluid circuit, a second fluid
circuit
between the water storage tank and the heat exchanger, and a local controller
configured to control the operation of the pump and the non-solar heating
system. The heat exchanger is configured to transfer heat from fluid in the
first
fluid circuit to water in the second fluid circuit. The second fluid circuit
is
fluidically connectable to a water source. The central control system is
configured to control the operation of the local controllers.
[0012] In an eighth embodiment, the invention is directed to a method of
heating water from a plurality of water storage tanks, comprising:
a) providing a local controller in association with each water storage tank
wherein the local controller is operatively connected to a non-solar heating
system for the associated water storage tank and a solar energy collector
system for the associated water storage tank;
b) providing a central control system that is in communication with the local
controllers;
c) selecting for each water storage tank at least one heating means from a
group of heating means including a non-solar heating system and a solar
energy collector;
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d) heating water in each water storage tank using the selected heating
means; and
e) sending signals from one of the group consisting of the central control
system and at least one local controller to the other of the group consisting
of
the central control system and at least one local controller, wherein the
signals
relate to the operation of the at least one local controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present invention will now be described by way of example
only with reference to the attached drawings, in which:
[0014] Figure 1 is a schematic illustration of a single-tank solar energy
water heating system in accordance with an embodiment of the present
invention;
[0015] Figure 2 is a schematic illustration of a controller used with the
solar energy water heating system shown in Figure 1;
[0016] Figure 3 is a schematic illustration of another single-tank solar
energy water heating system in accordance with another embodiment of the
present invention
[0017] Figure 4 is a schematic illustration of a controller used with the
solar energy water heating system shown in Figure 3;
[0018] Figure 5 is a schematic illustration of a dual-tank solar energy
water heating system in accordance with another embodiment of the present
invention;
[0019] Figure 6 is a flow diagram illustrating a method of heating water in
a water storage tank;
[0020] Figure 7 is a schematic illustration of a network of solar energy
water heating systems in accordance with another embodiment of the present
invention; and
i . .. . . . . . . ..
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[0021] Figure 8 is a flow diagram illustrating a method of heating water in
a plurality of water storage tanks.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Reference is made to Figure 1, which shows a solar energy water
heating system 10 in accordance with an embodiment of the present invention.
The solar energy water heating system 10 is used to heat water in a water
storage tank 11 using a combination of solar energy and using a non-solar
heating system 12. Using the solar energy water heating system 10 to heat the
water in the water storage tank 11 can reduce the energy costs associated with
heating the water relative to some prior art systems that utilizes a non-solar
heating system only.
[0023] The solar energy water heating system 10 may reside in a home,
a multi-unit residential building, a commercial building, an industrial
building or
any other structure where hot water is used.
[0024] The solar energy water heating system 10 includes the water
storage tank 11, the non-solar heating system 12, a solar energy collector 14,
a
heat exchanger 16, a first fluid circuit 18 between the solar energy collector
14
and the heat exchanger 16, a pump 20 configured to pump fluid through the
first fluid circuit 18, a second fluid circuit 22 between the water storage
tank 11
and the heat exchanger 16, and a controller 24.
[0025] The water storage tank 11 includes a first storage tank port 26,
which may be a consumption outlet through which hot water is drawn for use by
a user. The water storage tank 11 includes a second storage tank port 30 and
a third storage tank port 30, which connect the water storage tank 11 to the
second fluid circuit 22. The second storage tank port 30 may be positioned
approximately 2/3 of the way up the water storage tank 11. The third storage
tank port 30 may be positioned proximate the bottom of the water storage tank
11.
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[0026] The non-solar heating system 12 may be any suitable type of
heating system, such as, for example, an electric heating system.
Alternatively,
the non-solar heating system 12 may operate using oil, natural gas, propane or
some other means. The non-solar heating system 12 may include a single
heating element 32 which may be positioned approximately 2/3 of the way up
the water storage tank 11, preferably slightly above the height of the second
storage tank port 30. The positioning of the heating element 32 is discussed
further below.
[0027] In the embodiment shown in Figure 1, a thermostat 33 is
operatively connected to the non-solar heating element 12 and controls the
operation of the heating element 12 based on the temperature of water in the
water storage tank 11.
[0028] The solar energy collector 14 may be any suitable type of solar
energy collector. The solar energy collector 14 may be positioned on the roof,
of the structure, or in some other suitable position, such as on a wall that
is
oriented for exposure to the sun.
[0029] The heat exchanger 16 may be any suitable type of heat
exchanger, such as a brazed plate heat exchanger. The heat exchanger 16
includes a primary side 34, having a primary side inlet 36 and a primary side
outlet 38, and a secondary side 39 having a secondary side inlet 40 and a
secondary side outlet 42.
[0030] A heat transfer fluid is pumped by the pump 20 through the first
fluid circuit 18. More particularly, the heat transfer fluid is pumped by the
pump
20 from an expansion tank 44 to the solar energy collector 14 for heating
thereby, after which the heat transfer fluid flows through the primary side 34
of
the heat exchanger 16 and back to the expansion tank 44. The heat transfer
fluid may be any suitable type of fluid, such as a solution of propylene
glycol
and water to resist freezing during exposure to cold weather. The solution may
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comprise about 50 wt% propylene glycol and about 50 wt% water, or may have
some other ratio or composition altogether.
[0031] Water may flow by any suitable means through the second fluid
circuit 22, such as by means of a temperature differential that may be present
across the second side 39 of the heat exchanger 16. As a result of the
positioning of the heating element 32, the second storage tank port 30, and
the
third storage tank port 30, a temperature gradient can be introduced in the
water in the water storage tank 11 where the coldest water is at the bottom of
the tank 11, and hotter water is in the top portion of the tank 11.
[0032] Thus, circulation of water through the second fluid circuit 22 may
be induced passively (ie. without inducing water flow using a pump). The water
may flow from the water storage tank 11 through the third storage tank port 30
into the second fluid circuit 22, upwards through the secondary side 39 of the
heat exchanger 16 and then upwards to the second storage tank port 30 where
the water reenters the water storage tank 11. The heating element 32 may
heat water in the top portion of the tank 11 to be hotter than the water
entering
the water storage tank 11 through the second storage tank port 30.
[0033] A source water conduit 46 may be connected to a source water
inlet 48 into the second fluid circuit 22, which may be positioned between the
heat exchanger 16 and the second storage tank port 30. The source water
conduit 46 may be connected to any suitable water source (not shown) such as
a city water connection or a well. A source water flow control valve 50 may be
provided on the source water conduit 46 to control the introduction of source
water into the second fluid circuit 22 as needed based on the consumption of
water from the water storage tank 11 through the consumption outlet 26. The
operation of the source water flow control valve 50 may be controlled by any
suitable means, such as by a storage tank water level sensor (not shown).
Alternatively it is possible for the controller 24 to control the operation of
the
source water flow control valve 50.
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[0034] The heat exchanger 16 is configured to transfer heat from the
heat transfer fluid in the first fluid circuit 18 to water in the second fluid
circuit
22.
[0035] The controller 24 controls the operation of the solar energy water
heating system 10. Referring to Figure 2, the controller 24 may include a
processor 51, a memory 52, one or more inputs 53 for receiving signals from
one or more sensors, and one or more outputs 54 through with the controller 24
sends output signals (eg. to control a system component). The one or more
sensors that may be connected to the inputs 53 may include, for example, a
storage tank water exit temperature sensor 55 (Figure 2), a source water
temperature sensor 56, a heat exchanger secondary inlet water temperature
sensor 58, a solar energy collector temperature sensor 60, a source water flow
meter 62, and a non-solar heating element state sensor 64. The temperature
sensors 55, 56, 58 and 60 may be any suitable types of temperature sensor,
such as, for example, thermistors.
[0036] The storage tank water exit temperature sensor 55 is positioned
at a suitable position to sense temperature and to send to the controller 24
storage tank water temperature sensor signals that are indicative of the
temperature of hot water leaving the water storage tank 11. The storage tank
water temperature sensor signals may be sent to the controller 24 any suitable
way, such as along an electrical conduit 66 or, for example, via a wireless
connection.
[0037] The storage tank water exit temperature sensor 55 is positioned
at a suitable position to sense temperature and to send to the controller 24
storage tank water temperature sensor signals that are indicative of the
temperature of the hottest water in the water storage tank 11 and indicative
of
the temperature of the water leaving the water storage tank 11. Thus the
storage tank water temperature sensor signals from the storage tank water exit
temperature sensor 55 may be referred to as hot storage tank water
temperature sensor signals, or storage tank exit water temperature sensor
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signals. These signals may be sent to the controller 24 any suitable way, such
as along an electrical conduit 66 or, for example, via a wireless connection.
[0038] The source water temperature sensor 56 and source water flow
meter 62 are positioned at a suitable position to sense temperature and flow
respectively and to send to the controller 24 source water temperature sensor
signals and source water flow rate signals respectively that are indicative of
the
temperature and flow rate of any source water entering the second fluid
circuit
22. The source water temperature sensor signals and source water flow rate
signals may be communicated to the controller 24 by any suitable means, such
as along electrical conduits 68 and 70 or, for example, wirelessly.
[0039] The non-solar heating element state sensor 64 is positioned at a
suitable position to sense whether the non-solar heating element 12 is on or
off
and is configured to send to the controller 24 non-solar heating element state
sensor signals that are indicative of the of the state of the non-solar
heating
element 10. The structure of the non-solar heating element state sensor 64
may depend on the structure of the heating element 32. For example, if the
heating element 32 is electric, then the non-solar heating element state
sensor
64 may be configured to determine if there is current flow in the electrical
conduit connecting the heating element 32 to an electrical power source.
[0040] The controller 24 may be configured to operate in one or more
ways. For example, the controller 24 may be configured to determine the
amount of energy transferred over a given time period from the solar energy
collector 14 to water in the water storage tank 11. This may be determined by
any suitable method. For example, it may be determined using energy input
including: the temperature history of water in the water storage tank 11 over
the
time period, the volume of water in the water storage tank 11, the flow
history
and temperature history of any water introduced to the second fluid circuit 22
from the water source, the amount of time the non-solar heating system was on
over the given time period, and the power (eg. the wattage) of the non-solar
heating system 12.
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[0041] The difference between the current temperature of the water in
the water storage tank 11 and the temperature at the beginning of the time
period can be used to determine the total energy change in the water in the
tank 11. These two temperatures can be obtained by any suitable means, eg.
using the storage tank water exit temperature sensor 55.
[0042] The flow history and temperature history of the water introduced
into the second fluid circuit 22 from the water source (not shown) combined
with the temperature history of the water in the water storage tank 11 may be
used to determine the amount of energy lost from the water in the water
storage tank 11 as a result of water consumption from the tank 11 and
replenishment from the water source (not shown).
[0043] The amount of time the non-solar heating system 12 was on over
the given time period and the power (eg. the wattage) of the non-solar heating
system 12 can be used to determine the amount of energy introduced by it into
the water in the water storage tank 11.
[0044] The total energy change of the water in the water storage tank 11,
the amount of energy lost as a result of water consumption and replenishment
from the water source, and the amount of energy introduced by the non-solar
heating system 12 into the water in the tank 11 can be used to determine the
amount of energy introduced into the water from the tank 11 by the solar
energy collector 14, which may be referred to as Esolar. It will be understood
that the above is but an exemplary way of determining the value of Esolar
using
the aforementioned sensor data. It is possible for the controller 24 to
determine
the value of Esolar using the aforementioned energy input information without
specifically calculating the individual energy contributions made by the
source
water and non-solar heating element but instead to perform a single large
calculation. It is alternatively possible, for example, for the controller 24
to
determine the value of Esolar without calculation at all, but instead to use
the
values from the sensors as input values for a lookup table, or by some other
method that is different than using lookup tables or calculations. As yet
another
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alternative, the controller 24 may use a combination of methods, such as using
both lookup tables and calculations, to determine the value of Esolar.
[0045] As an example of a different but related approach to determining
the value of Esolar, the controller 24 may compare the expected storage tank
water exit temperature with the actual storage tank water exit temperature.
The
difference between the aforementioned expected and actual temperatures may
be attributed to the energy input from the solar energy collector 14.
[0046] It is possible for the controller 24 to obtain the aforementioned
energy input information using sensor data that is stored in the memory 52. It
is alternatively possible for the controller 24 to obtain at least some of the
energy input information without use of sensors. For example, the power of the
non-solar heating system 11 may be obtained without using any sensors. It
may, for example, simply be a value that is stored in the memory 52 based on
the model and type of water storage tank 11. As another example, the source
water temperature sensor 56 may be omitted and the controller 24 may instead
use an estimate of the temperature of the source water in its determination of
Esolar. As yet another example, the source water flow meter 62 may be
omitted and the controller 24 may instead use an estimate for the flow rate of
the source water into the second fluid circuit 22.
[0047] Information relating to the energy input from the solar energy
collector 14 may be displayed on a display 74 that may be provided as part of
the controller 24. The information displayed on the display 74 may include,
for
example, the energy saved, the amount of carbon saved, and/or the money
saved by using the solar energy water heating system 22. The display 74 may
be positioned with the other components of the controller 24 or may be
remotely positioned for convenient viewing by a user of the solar energy water
heating system 22. For example, the display 74 may be in a main floor hallway
of a house, and may communicate wirelessly (or by electrical conduit) with the
rest of the controller 24 which may be positioned proximate the pump 20 and
water storage tank 11 in a furnace room on a basement level of the house.
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[0048] The controller 24 may include an output 54 through which it
controls the operation of the pump 20 based on signals from one or more of the
sensors. For example, the controller 24 may be configured to start the pump
20 if the temperature of the water leaving the water storage tank 11 is less
than
a predetermined low storage tank water exit temperature. Starting the pump 20
initiates flow in the first fluid circuit 18, which generates heat transfer
from the
solar energy collector 14 into the heat transfer fluid, which in turn
generates
heat transfer from the first fluid circuit 18 to the water in the second fluid
circuit
22 through the heat exchanger 16. In embodiments wherein the thermostat 33
is operational and is operatively connected to the non-solar heating element
32,
the predetermined low storage tank water exit temperature is higher than the
temperature at which the thermostat 33 activates the non-solar heating element
32.
[0049] The controller 24 may check for one or more of a plurality of
conditions when determining whether or not to turn on or turn off the pump 20.
For example, if the controller 24 receives signals from the solar energy
collector
temperature sensor 60 and the heat exchanger secondary inlet water
temperature sensor 58 and determines that the temperature difference
therebetween is less than a predetermined threshold temperature difference,
the controller 24 may prevent operation of the pump 20. Because the operation
of the pump 20 itself consumes energy, the amount of energy saved by heating
the storage tank water using the solar energy collector 14 only offsets the
energy consumed by the pump 20 if the temperature difference is sufficiently
large between the heat transfer fluid and the water. The predetermined
threshold temperature difference may be any suitable amount, such as, for
example, about 10 degrees Celsius.
[0050] As another example, if the controller 24 receives signals from the
storage tank water exit temperature sensor 55 indicating that the water
leaving
the water storage tank 11 exceeds a predetermined high storage tank water
exit temperature, the controller 24 is configured to prevent operation of the
, _ _ _ _
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pump 20to inhibit any further heating of the water by the solar energy
collector.
The predetermined high storage tank water exit temperature may be about 85
degrees Celsius.
[0051] As another example, if the controller 24 receives signals from the
solar energy collector temperature sensor 60 indicating that the solar energy
collector 14 is less than a predetermined low solar energy collector
temperature, or if the controller 24 receives signals from the source water
temperature sensor 56 indicating that the source water is less than a
predetermined low source water temperature, then the controller 24 may
prevent operation of the pump 20 to inhibit exposure of the solar energy
collector 14 an the heat exchanger 16 respectively to freezing conditions. The
predetermined low solar energy collector temperature may be any suitabie
temperature, such as, for example, about 4 degrees Celsius. Below this
temperature, there is a risk of the heat transfer fluid thickening in
consistency
(becoming gel-like) and becoming difficult to pump using the pump 20. In a
thickened state, the heat transfer fluid could possibly cause damage to the
pump 20 if an attempt were made by the pump 20 to pump it.
[0052] The predetermined low source water temperature may be any
suitable temperature, such as, for example, about 4 degrees Celsius.
[0053] Optionally, a suitable flow cut-off valve 78 may be provided
between the source water inlet 48 and the second storage tank port 30.
Periodically, the flow cut-off valve 78 may be closed and the source water
flow
control valve 50 may be opened to direct source water to flow through the heat
exchanger 16 an into the water storage tank 11 through the third port 20, to
flush the heat exchanger 16 of deposits of minerals and the like, such as
calcium carbonate, that can build up therein. The flow cut-off valve 78 may be
closed whenever the source water flow control valve 50 is opened, and the
operation of the flow cut-off valve 78 may be related to the operation of the
source water flow control valve 50, such that when the valve 50 opens, the
valve 78 closes and when the valve 50 closes the valve 78 opens. The flow
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cut-off valve 78 may be controlled by any suitable means. For example, the
cut-off valve 78 may be electrically connected to the source water flow
control
valve 50 so that when the valve 50 is open, the electrical connection is
configured to close the valve 78 and when the valve 50 is closed, the
electrical
connection is configured to open the valve 78. The structure, control and
operation of the flow cut-off valve 78 may be as described in US Patent No.
6,827,091 (Harrison). It is optionally possible for the controller 24 to
include an
output 54 (Figure 2) through which it controls the operation of the flow cut-
off
valve 78.
[0054] Reference is made to Figure 3, which shows a solar energy water
heating system 100 in accordance with another embodiment of the present
invention. The solar energy water heating system 100 may be similar to the
solar energy water heating system 10 (Figure 1) except that the solar energy
water heating system 100 includes a controller 102 instead of the controller
24
(Figure 1), which controls the operation of both the pump 20 and the non-solar
heating system shown at 104. The non-solar heating system 104 includes a
non-solar heating element 106 that may be similar to the non-solar heating
element 32 (Figure 1).
[0055] There are many features that can be provided to the solar energy
water heating system 100 as a result of controlling both the pump 20 and the
non-solar heating system 104 with the controller 102, in addition to having
the
features described with respect to the controller 24 of Figure 2. For example,
the controller 102 may be configured to control the first non-solar heating
system 104 and the pump 20 based on signals from the storage tank water exit
temperature sensor 55. As an example of how this control of both heating
means (ie. of both the pump 20 and the non-solar heating system 104) could
be carried out, if the storage tank water exit temperature sensor 55 senses a
temperature that is lower than a first predetermined low storage tank water
exit
temperature, then the controller 102 may start the pump 20. If the storage
tank
water exit temperature sensor 55 senses a temperature that is lower than a
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second predetermined low storage tank water exit temperature that is lower
than the first predetermined low storage tank water exit temperature, then the
controller 102 may turn on the non-solar heating system 104.
[0056] The controller 102 may select which of the heating means (ie.
which of the pump 20 and the non-solar heating system 104) to use to heat
water in the water storage tank 11 based on one or more conditions. One such
condition is the amount of time to heat the water in the water storage tank
11.
For example, the controller 102 may be configured to determine the expected
length of time required to heat up water in the water storage tank 11 from a
current temperature to a target temperature using only energy from the solar
energy collector 14. If the expected length of time is not more than a
predetermined maximum acceptable length of time, then the controller 102 may
start the pump 20 and heat the water in the water storage tank 11 using only
energy from the solar energy collector 14. If, however, the expected length of
time exceeds the predetermined maximum acceptable length of time, then the
controller 102 may heat the water using the non-solar heating system 104 and
optionally also using energy from the solar energy collector 14.
[0057] The controller 102 may be configured to control the operation of
the pump 20 and the first non-solar heating system 104 differently at
different
times of the day. For example, during daytime hours the electrical demands on
a utility company may be higher than the demands at night. The hours during
which demand is higher may be referred to as peak hours. During these peak
hours, energy may be more expensive and there is therefore incentive to
reduce energy consumption during peak hours. During these peak hours, the
maximum acceptable length of time may be increased to increase the range of
situations in which the controller 102 will opt to heat the water in the water
storage tank 11 solely with energy from the solar energy collector 14. During
off-peak hours, the maximum acceptable length of time may be reduced to
accelerate the heating of the water in the water storage tank 11 without
incurring excessive energy costs. Even in jurisdictions wherein a local
utility
CA 02639764 2008-09-25
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company does not charge higher rates for energy during peak hours, the
controller 102 may still increase the maximum acceptable length of time during
at least some daytime hours, since in a typical home the rate of consumption
of
hot water may be low relative to the rate of consumption during the early
morning and during the evening.
[0058] The controller 102 may be configured to operate on a rate basis.
For example, the controller 102 may compare the rate at which hot water is
being drawn from the water storage tank 11 with the rate at which water in the
water storage tank 11 can be heated to a target temperature solely using
energy from the solar energy collector 14. If the result of the comparison
indicates that the water in the water storage tank 11 would increase in
temperature at an acceptable rate over time, then the controller 102 may heat
the water in the water storage tank 11 solely using energy from the solar
energy collector 14. Conversely, if the result of the comparison indicates
that
the temperature of water in the first water storage tank 112 would decrease
over time or would not increase sufficiently quickly, then the controller 102
may
activate the non-solar heating system 104, and may optionally also activate
the
pump 20.
[0059] The controller 102 may be configured to heat the water in the first
water storage tank 112 using a control algorithm. For example, the controller
102 may be configured to heat the water using a PID-based (ie. a proportional-
integral-derivative-based) control algorithm, a PI-based (le. a proportional-
integral-based) control algorithm, a P-based (ie. a proportional-based)
control
algorithm, fuzzy logic or any other suitable algorithm.
[0060] Reference is made to Figure 4, which shows a schematic
illustration of the controller 102. The controller 102 may be similar to the
controller 24 (Figure 2), except that the input 53 (Figure 2) that is
connected to
a non-solar heating system state sensor 64 is replaced by an output 54 that is
connected to the non-solar heating system 104.
. . . . . . . . . . .
CA 02639764 2008-09-25
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[0061] Reference is made to Figure 5, which shows a solar energy water
heating system 110 in accordance with another embodiment of the present
invention. The solar energy water heating system 110 may be similar to the
solar energy water heating system 10 except that the solar energy water
heating system 110 includes a water storage tank 112 with no non-solar
heating system associated therewith, upstream from a pre-existing, second
water storage tank 114.
[0062] The solar energy water heating system 110 includes the water
storage tank 112, which may be referred to as a first water storage tank 112,
the solar energy collector 14, the heat exchanger 16, the first fluid circuit
18
between the solar energy collector 14 and the heat exchanger 16, the pump 20,
a second fluid circuit 116 between the first water storage tank 112 and the
heat
exchanger 16, and a controller 117.
[0063] The pre-existing, second water storage tank 114 may be a typical
water storage tank and may have a consumption outlet 118, a second storage
tank port 120 and a third storage tank port 122. Water in the pre-existing
water
storage tank 114 may be heated by a non-solar heating system 124, which may
include a first non-solar heating element 126 and a second non-solar heating
element 128. The first and second non-solar heating elements 126 and 128
may be controlled by a thermostat 130.
[0064] The first water storage tank 112 includes a consumption port 132,
a second storage tank port 134 and a third storage tank port 136. A
consumption fluid conduit 138 may connect the consumption port 132 to either
the second storage tank port 120 or the third storage tank port 122 on the pre-
existing, second water storage tank 114. The temperature sensor 55 may be
positioned on the consumption fluid conduit 138, preferably proximate the
consumption port 118.
[0065] The second fluid circuit 116 may be similar to the second fluid
circuit 22 in Figure 1. The second storage tank port 134 may be positioned on
, _ _
CA 02639764 2008-09-25
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the top of the first water storage tank 112 instead of being about 2/3 of the
way
up. The third storage tank port 136 may be positioned proximate the bottom of
the tank 112. As a result of the positions of the second and third storage
ports
134 and 136, a temperature gradient is set up throughout the entire height of
the tank 112 to drive the flow of water through the second fluid circuit 116.
[0066] The controller 117 may be similar to the controller 24 (Figure 1).
The solar energy water heating system 110 may lack a non-solar heating
system sensor however. Thus, it is possible that the controller 117 may not
receive information regarding the state of the non-solar heating system 124.
The controller 117 may nonetheless be capable of determining the energy
contributed to the water stored in the first water storage tank 112 since
there is
no non-solar heating system associated with that tank.
[0067] The controller 117 may include several of the features associated
with the controller 24 (Figure 1). For example, the controller 117 may be
configured to prevent operation of the pump 20 if the temperatures sensed by
the solar energy collector temperature sensor 60 and by the source water
temperature sensor 56 are less than a predetermined low solar energy collector
temperature and a predetermined low source water temperature respectively,
both of which may be any suitable value, such as about 4 degrees Celsius.
[0068] It is optionally possible to provide a system similar to the system
110 wherein the thermostat 130 is disabled and the pre-existing non-solar
heating system 124 is controlled by the controller 117.
[0069] Reference is made to Figure 6, which illustrates a method 200 of
heating water in a water storage tank in accordance with another embodiment
of the present invention, which can be carried out using the system 100 shown
in Figure 3, or which may alternatively be carried out by any other suitable
system.
[0070] The method 200 includes a step 202 wherein at least one heating
means is selected from a group of heating means including a non-solar heating
CA 02639764 2008-09-25
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system and a solar energy collector, and a step 204 which includes heating
water in the water storage tank using the selected heating means based at
least in part on the temperature of water in the water storage tank.
[0071] At step 206, the expected length of time for water in the water
storage tank to be heated using only energy from the solar energy collector to
a
target temperature is determined. If the expected length of time exceeds a
predetermined maximum acceptable length of time then the water from the
water storage tank may be heated using the non-solar heating element.
[0072] As noted with respect to the exemplary system 100 shown in
Figure 3, the at least one heating means selected in step 204 may be selected
based on the time of day. For example, if the time of day falls within a first
portion of the day, then at least the non-solar heating element is selected if
the
expected length of time determined in step 206 exceeds the predetermined
maximum acceptable length of time. If the time of day falls within a second
portion of the day, which may, for example, correspond to peak hours of energy
demand, then at least the solar energy collector is selected regardless of the
expected length of time assuming that other conditions do not preclude the
operation of the pump, such as the temperature of the solar energy collector.
[0073] Prior to step 202, the method 200 may include a step 208 of
determining the rate of consumption of hot water from the water storage tank
and determining whether the solar energy collector is capable of heating the
water in the water storage tank sufficiently quickly to compensate for the
flow of
source water into the water storage tank. The method 200 may further entail
heating water in the water storage tank according to a control algorithm. The
control algorithm may be any suitable type of control algorithm, such as a PID
control algorithm.
[0074] Reference is made to Figure 7, which shows a network of solar
energy water heating systems 300 in accordance with another embodiment of
the present invention. The network of solar energy water heating systems 300
CA 02639764 2008-09-25
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includes a central control system 302, and a plurality of solar energy water
heating systems 304. Each solar energy water heating system 304 may be
similar to the solar energy water heating system 100 (Figure 3), and includes
the solar energy collector 14, the heat exchanger 16, the first fluid circuit
18
between the solar energy collector 14 and the heat exchanger 16, the pump 20,
a second fluid circuit 22 between the heat exchanger 16 and the first water
storage tank 11. Each solar energy water heating system 304 further includes
a local controller 308 which is configured to control at least the operation
of the
pump 20 and the non-solar heating system 104 and which is configured to be
controlled by the central control system 302. The communication between the
central control system 302 and the local controllers 308 may be one-way
communication from the local controllers 308 to the central control system
302,
one-way communication from the central control system 302 to the local
controllers 308, or may be two-way communication between the local
controllers 308 and the central control system 302. For example, the central
control system 302 may be configured to determine the availability of solar
energy in the vicinity of the local controllers 308 and may be configured to
act
on that information. This information may be passed to users of the solar
energy water heating systems 304 so that, for example, if the information
indicates that little or no solar energy will be available the affected users
can
reduce their energy consumption or modify their energy consumption to skew it
towards off-peak hours. This information may be passed on automatically by
the central control system 302 to the affected local controllers 308 for
communication to associated users. For example, the information may be
displayed on a display associated with each local controller 308.
Alternatively
this information may be passed on manually, eg. by email, by a person who
receives it from the central control system 302 to users of the affected solar
energy water heating systems 304.
[0075] Another function that could be carried out by the central control
system 302 is to inform the utility company in situations where there is
likely to
CA 02639764 2008-09-25
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be an increased demand for electric power due to low availability of solar
energy. The central control system 302 may be configured to send control
signals to the local controllers 308 to adjust the usage of the non-solar
heating
systems 104 according to the availability of solar energy.
[0076] The central control system 302 may be configured to receive
information from the local controllers 308 regarding the amount of energy
saved as a result of solar energy water heating activity and/or the amount of
energy consumed by use of the non-solar heating element and may be
configured to cooperate with a billing system to reward and/or penalize
individual users based on their activity. Optionally the feature of rewarding
and/or penalizing users may take into account the availability of solar energy
during the time period being considered. Optionally, the central control
system
302 can control the operation of the local controllers 308 based on the time
of
day, for example, to shift usage of non-solar heating elements to off-peak
portions of the day. Instead of controlling the local controllers 308 based on
the
time of day, the central control system 302 could additionally or
alternatively
monitor the actual energy demand being place on the utility company in real
time and can adjust the usage of non-solar heating elements 104 as a way of
controlling the energy demand on the utility company.
[0077] Reference is made to Figure 8, which illustrates a method 400 of
heating water from a plurality of water storage tanks, in accordance with
another embodiment of the present invention. The method 400 may be carried
out using the network 300 shown in Figure 7, or may alternatively be carried
out by any other suitable means.
[0078] The method 400 includes a step 402 wherein a local controller is
provided in association with each water storage tank. The local controllers
are
each operatively connected to a non-solar heating system for the associated
water storage tank and to a solar energy collector system for the associated
water storage tank. At step 404 a central control system is provided. At step
406, a selection is made of at least one heating means from a group of heating
CA 02639764 2008-09-25
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means including the non-solar heating system and the solar energy collector.
Step 408 includes heating water in each water storage tank using the selected
heating means. At step 410, signals are sent at least one way between the
central control system and one or more local controllers, relating to the
operation of the at least one local controller. These signals may be sent
before, after or during the water in the water storage tanks is heated, or a
combination thereof.
[0079] The signals may, for example, be instructions from the central
control system to the local controllers and may be based at least in part on
the
availability of solar energy. The signals may, for example, be instructions
from
the central control system to the local controllers and may be based at least
in
part on time of day.
[0080] The signals may, for example, may be from one or more local
controllers to the central control system and may relate to one or more data
related to the group consisting of: energy consumed by the non-solar heating
system, and energy saved resulting from use of the solar energy collector.
[0081] In any of the embodiments descried herein, in the event that
excess solar energy is available and is not needed for heating, structure may
be provided to divert the heat transfer fluid to another load, such as another
heat exchanger associated with a heating system for a swimming pool, for
example. The structure may include suitable valves which may be controlled
by the controller 24 or 102 or which may be controlled by some other means,
conduits to convey the heat transfer fluid to the other load and appropriate
sensors.
[0082] In the embodiments described herein, the storage tank water exit
temperature sensor has been described as being used to indicate the
temperature of water in the water storage tank. In at least some embodiments
however, it may be possible to use a different temperature sensor to obtain a
suitable measurement. For example, when determining the amount of energy
CA 02639764 2008-09-25
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change that takes place in the water in the water storage tank, it may be
possible to use the temperature history of the heat exchanger secondary inlet
temperature sensor. It will be noted however, that this sensor may at certain
times sense the temperature of water from the water source that is being sent
to the water storage tank through the third storage tank port, which could
affect
the temperature history.
[0083] While the above description constitutes a plurality of
embodiments of the present invention, it will be appreciated that the present
invention is susceptible to further modification and change without departing
from the fair meaning of the accompanying claims.
_I _
