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| TEG-Solar Hybrid Power System Single Line Diagram |
Each system
consists of:
-
Thermoelectric Generators
(TEGs)
-
Hazardous area rated solar panels
-
Hazardous area rated battery system
-
Charge Controller Unit
(CCU)
-
Isolation Switch Box and TEG Control Panel
-
Solar Charge Controller
-
DC-DC Converter Module (application dependent)
-
Fuel Conditioning System (application dependent)
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| 5 Units of 100W Thermoelectric Generators |
The TEGs are connected together in
a parallel configuration to produce the desired 24 VDC electrical
output at 20ºC.
The electrical
output from the generators
is routed through an Isolation
Switch
Box
to a Class 1
Division 2-rated Charge Controller Unit. Connected
in parallel is a battery bank designed
to provide the necessary autonomy for the customer’s DC loads.
24 V solar panels are wired to the Charge Controller Unit (CCU),
and connect in parallel through
a solar charge controller in the
CCU, to the TEGs and battery bank.
The fuel supply for the thermoelectric generators flows
through a Fuel Conditioning System (FCS).
The FCS removes
solids and liquids from the
fuel stream that
could affect
the performance of the TEG.
Included on each TEG are two 4-20
mA signal conditioners that
report the voltage and
current output from each TEG unit
to a SCADA monitoring system supplied
by
the customer.
Isolation Switch Box and TEG Control Panel
The TEG Isolation Switch Box and
TEG Control Panel
is used to house the interconnection of
the thermoelectric
generator power and signal outputs to the remainder of the system. The Isolation
Switch
box contains isolation breakers
and an Output Breaker. The
TEG Isolation Breakers allow
each of the TEGs
to be electrically isolated from each other and
the system. The
Output Breaker controls
the power of the parallel-connected TEGs to the Charge Controller
Unit.
The Ignition Power Isolation
Breaker is included in the
Isolation Switch Junction
Box.
This breaker acts as the
main circuit interrupter for the external
24 VDC power supplied from the
CCU to the spark
ignition
circuit within each
of the five TEGs. Secondary
circuit
protection for each TEG spark
ignition
circuit is provided by the five 2-amp Ex-d rated fuses
in the Isolation Switch
Junction
Box.
The TEG Control Panel provides interconnection
terminals to connect
the voltage and current
readings
and status alarm
signal from
each of the
TEGs to the SCADA system.
24 VDC Charge Controller Unit
The Charge Controller Unit serves as
the main connection
and distribution point for the TEG
system power, solar system
power, battery system power and customer loads.
All circuits are housed in
an enclosure certified for use within a hazardous area environment and have the necessary Ex and IP
ratings.
The TEG Power Isolation Breaker protects
the power circuit
from over current and
allows the TEG system
to be disconnected. When the TEG system is disconnected,
the customer load
is powered by the battery or solar power sources
and TEG ignition and
monitoring circuits are powered from the
System Bus.
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| Solar Panels |
The Solar Charger Controller provides power on demand
if solar power from
the solar panel
array is present.
During the time of sufficient solar radiation,
it is able to supply both customer load
and battery charge current.
The Solar Charger Controller automatically adjusts
output voltage and current
depending on
available power, load
power demand
and
battery charge condition.
The charging
voltage and current
set points are adjustable.
The battery system is intended to be
a back up source of power in case of failure or unavailability
of TEG or solar sources. For that reason the
battery is being continuously charged when TEG
or solar sources of power are available. For the normal working condition of the system, the
TEG system is acting in
float
charging mode providing power for customer load and
continuously charging the battery.
To provide that
charging mode, the
TEG system is set at a pre-set V output voltage, which is the
Battery manufacturer’s
recommended float charge voltage.
The
solar system acts in two charging modes: boost charge and
float
charge.
The controller chooses the charging mode
automatically,
depending
on battery charge state.
DC-DC Converter Module
Depending on project specifications, the power system output voltage is sometimes required to at the 24.0 V ± 5% range.
The DC-DC Converter modules
are used
between the
System Bus
and the System Output to comply with the output voltage range requirement. The DC-DC Converter
Array has been
designed to
supply the nominal output
power and consists of integrated
DC-DC converter base modules,
in an N+1
configuration
with an interface board
that
includes noise and voltage suppression circuits
on it. The converter acts as voltage regulator
providing stable output voltage with wide
range of input voltage from 24 V
to 32 V.
The output voltage of the converter is adjustable and
is factory preset. The
output voltage is adjusted using
the 10-turn potentiometer located
on the module board. The
converter array also includes a common
alarm function with a single dry contact terminal
that indicates
a malfunction of
any of the modules.
This signal is available in the SCADA
terminal bank.
The Charge Controller Unit includes the
following indicators and
meters:
-
Analog voltmeter indicating Power System
output voltage
-
Analog meter indicating battery charge/discharge current
-
Green LED indicator indicating the power system status
-
Green and red LED
indicators indicating the availability and
condition of the battery Power Source
-
Green and red LED
indicators indicating the availability and
condition of the system
Output Power
SCADA signals for system
control and monitoring consist of digital
(dry contact) signals, and
analog signals.
The digital signals are described in the
following table.
Signal
|
Open is:
|
Indicates:
|
Battery voltage low
|
Active
|
Battery voltage has reached the Low
Voltage Disconnect (LVD) point
|
Battery disconnect
|
Active
|
Battery power source is disconnected
|
Load disconnected
|
Active
|
Power to customer load is disconnected
|
Volt reg. alarm
|
Fault
|
Common DC to DC converter group alarm
|
The analog signals
(4 – 20 mA) are described
in the following table.
Signal
|
Indicates and is proportional to:
|
Battery voltage
|
Battery voltage
|
Battery current
|
Battery current
4 to12 mA signal indicates
discharging
12 to 20
mA signal indicates charging
|
Load current
|
Output current
|
Load voltage
|
Output voltage
|
Signal Conditioners
The signal conditioners sense the required
voltage or mV signals at the
specified terminals or shunts in the Charge Controller Unit.
The signal conditioner then converts the signal reading into a
4 to 20 mA current output. The signal conditioners
have been setup and
calibrated
according to the
specified signal input
range.
24 VDC Battery Bank
A battery bank is included in the
system to provide
backup power in
the event the thermoelectric power system
is off line or unable to
supply the power demand. This battery is
sized
and tested to provide
a load, connected to the
output of the Charge Controller Unit at
24 volts for the desired autonomy.
The battery bank consists
of batteries connected
in series to provide a nominal
V. Each cell is rated
to be discharge to the
appropriate end cell
voltage
The cells are housed
in a
Ex rated enclosure.
Fuel Conditioning System (FCS)
Depending on fuel gas
quality the FCS components can vary.
Where fuel gas needs more intensive filtration an (FCS) can
consist of a particulate filter, a coalescing filter, a CO2 filter and
knock-out vessel
to remove solids and liquids from the
fuel stream.
A 316 stainless steel
particulate filter is employed to
remove solids from the gas
stream using a
20-micron rated filter element.
From the particulate filter, the
gas flows into the liquid
knock out vessel that removes any free
liquids from the gas stream. The auto-drain
trap
controls
the liquid level in the knock out vessel with a
high liquid level
switch
that provides an alarm
signal in the
event that
the liquid level rises
in the knock-out vessel.
From the knockout vessel
the fuel gas flows to a Finite coalescing filter with auto-drain.
This filter is equipped
with a 0.01-micron rated filter element and
is designed to catch
any liquid that may be carried
over from the knock
vessel. Connected to the
drain header,
the auto-drain ensures stripped liquids do not collect in the coalescing filter.
The final element in fuel conditioning system is the
CO2 filter.
This polyimide membrane filter
separates
the CO2 gas component from
the fuel gas
stream ensuring a constant energy value of
the gas being supplied to the
thermoelectric generator. Varying energy values
will affect the performance of the TEG and could
result in damage to
the power unit. A stainless housing protects the replaceable filter element.
Reference: Global Thermoelectric, Canada
