SOLAR POWERED HEAT TRACE SYSTEM

SYSTEME SOLAIRE A CABLES CHAUFFANTS

English Abstract

A solar powered heat trace system includes a heat trace system and a photovoltaic panel. The heat trace system is rated for use with alternating current at a specified alternating current voltage with a specified watts per foot of heat output. The photovoltaic panel is capable of converting sunlight into direct current electric power. Direct current is supplied from the photovoltaic panel to the heat trace system at a direct current voltage which is substantially equivalent to the specified alternative current voltage and produces heat within the specified watts per foot heat output for which the heat trace system is rated.

French Abstract

Un système de traçage thermique à énergie solaire comprend un système de traçage thermique et un panneau photovoltaïque. Le système de traçage thermique est conçu pour être alimenté par un courant alternatif à une tension de courant alternatif spécifiée avec une puissance calorifique en watts par pied spécifiée. Le panneau photovoltaïque est en mesure de convertir la lumière du soleil en un courant électrique continu. Le courant continu est fourni par le panneau photovoltaïque au système de traçage thermique à une tension de courant direct qui est essentiellement équivalente à la tension de courant alternatif spécifiée et produit de la chaleur en fonction de la puissance calorifique en watts par pied spécifiée pour laquelle le système de traçage thermique est conçu.

Claims

5
What is Claimed is:

1. A solar powered heat trace system, comprising:
a heat trace system rated for use with alternating current at a specified
alternating
current voltage with a specified watts per foot of heat output;
a photovoltaic panel capable of converting sunlight into direct current
electric power;
and
a battery that is charged by the photovoltaic panel and that supplies direct
current to
the heat trace system at a direct current voltage which is substantially
equivalent to the
specified alternative current voltage and produces heat within the specified
watts per foot heat
output for which the heat trace system is rated.
2. The solar powered heat trace system as defined in Claim 1, wherein the heat
trace system
is rated for 120 volts alternating current with a heat output of 20 watts per
foot and the
equivalent direct current voltage is approximately 48 volts, producing about 7
watts per foot.
3. A method comprising the steps of:
providing a battery that is charged by a photovoltaic panel; and
using the battery to provide direct current to a heat trace system rated for
use with
alternating current at a specified alternating current voltage with a
specified watts per foot of
heat output, the direct current being supplied at a direct current voltage
which is substantially
equivalent to the specified alternative current voltage and produces heat
within the specified
watts per foot heat output for which the heat trace system is rated.

Description

CA 02497375 2005-02-17
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TITLE OF THE INVENTION:
Solar Powered Heat Trace System
FIELD OF THE INVENTION
The present invention relates to a solar powered heat trace system.
BACKGROUND OF THE INVENTION
There is a need for heat trace systems at remote locations, such as well
sites, to
prevent pipes from freezing. Heat trace systems are made for use with
alternating current.
Solar power generating systems produce direct current. In order to use heat
trace systems
with solar power, the direct current produced must be converted to alternating
current.
Unfortunately, the use of inverters which change direct current to alternating
current produce
unacceptable losses.
SUMMARY OF THE INVENTION
According to the present invention there is provided a solar powered heat
trace system
which includes a heat trace system and a photovoltaic panel. The heat trace
system is rated
for use with alternating current at a specified alternating current voltage
with a specified watts
per foot of heat output. The photovoltaic panel is capable of converting
sunlight into direct
2 0 current electric power. Direct current is supplied from the photovoltaic
panel to the heat trace
system at a direct current voltage, which is substantially equivalent to the
specified alternative
current voltage and produces heat within the specified watts per foot heat
output for which the
heat trace system is rated.
2 5 BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the
following description in which reference is made to the appended drawings, the
drawings are
for the purpose of illustration only and are not intended to in any way limit
the scope of the
invention to the particular embodiment or embodiments shown, wherein:
30 FIG. 1 is a side elevation view of a solar powered heat trace system
constructed in
accordance with the teachings of the present invention.
FIG. 2 is a schematic diagram of the solar powered heat trace system
illustrated in


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FIG.1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment, a solar powered heat trace system generally
identified by
reference numeral 10, will now be described with reference to FIG.1 and FIG.
2.
Structure and Relationship of Parts:
Referring to FIG. 1, there is shown solar powered heat trace system 10
including a
heat trace system indicated generally by reference numeral 12 rated for use
with alternating
1 o current at a specified alternating current voltage with a specified watts
per foot of heat output.
For example, heat trace system 12 may be rated for 120 volts alternating
current (VAC) with
a heat output of 20 watts per foot. Heat trace system 12 is powered by a
photovoltaic panels
14 capable of converting sunlight into direct current electric power. As
shown, a bank of four
photovoltaic panels 14 are shown connected in series, and are used to charge a
bank of four
batteries 16 connected in series, such as 120 Amp/Hour batteries. Batteries 16
are charged
via a charge regulator 18. Direct current is then supplied from photovoltaic
panel 14 to heat
trace system 12 at a direct current voltage (VDC) that is substantially
equivalent to the
specified alternative current voltage and produces heat within the specifted
watts per foot heat
output for which the heat trace system is rated. In the example heat trace
system 12 described
2 0 above, the equivalent direct current voltage would be approximately 48
VDC. This is done
using a multi-function timing relay 20, such as a 48 VDC timing relay, that
will oscillate the
load to maintain a fifty percent duty cycle. The 48 VDC is then carried to
heat trace system
12 by conductor 22, such as a # 14 gauge, 2 conductor teck cable. Conductors
22 are
connected to the power connection kit 32 of heat trace system 12 by connectors
30 that
2 5 provide a grounded, dust-free and water-tight connection. A water-tight
foam and foil
insulated enclosure 24 is used to guarantee a secure atmosphere for the
components within.
Enclosure 24 and photovoltaic panels 14 are supported by a stand 26, which
includes stakes
28 to stabilize the unit against adverse conditions such as wind.
3 0 Heat trace system 12 includes power connection kit 32 and a heat trace 34.
An
example is a 120 VAC 20 watts/foot heat trace that produces approximately 7
watts/foot of
heat when connected to 48 VDC without insulation. In addition, there is a
terminal end kit 36


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that insulates heat trace 34 from ground and the weather. As depicted, there
are two heat
traces 32, two power connection kits 32, and another conductor 22 connecting
power
connection kits 32 via connectors 30.
Referring to FIG. 2, there is shown a sample circuit diagram of solar powered
heat
trace system 10. Other components, such as fuses 33 may be included.
Using the example specifications given above, it has been found that the
maximum
heat trace that can be connected is a 5' length, or two separate lengths that
equal 5'. Loading
beyond this limit causes the system to fail after about 14 short, cold winter
days. It will be
understood that larger systems may be constructed to support greater loads as
necessary,
however, it is believed that the apparatus described above is adequate for
common uses.
Operation:
The use and operation of solar powered heat trace system 10 will now be
discussed
with reference to FIGS. 1 and 2. The various parts are arranged as shown in
FIG. 1 and
connected as shown in FIG. 2. Referring now to FIG. 1, photovoltaic panels 14
are used to
charge batteries 16 via charge regulator 18. Timing relay 20 oscillates the
load to maintain a
fifty percent duty cycle, and conductor 22 carries the current to heat trace
system 12.
2 0 Connectors 30 are used to connect conductors 22 to power connection kit
32. Heat trace 34 is
used to prevent freezing of gas field components 38, such as valves located
just below the
flowline.
There has been reference in the description to a duty cycle. It will be
apparent to one
2 5 skilled in the art that the use of a duty cycle is not required. It could
be run 24 hours a day on
direct current. The use of a duty cycle reduces the size requirements for the
battery pack and
the solar panel. For a heat tracing application, 24 hour operation would far
exceed the needs
for the application. The duty cycle selected can vary. Beneficial results have
been obtained
with a duty cycle that involves one hour on and one hour off. It will be
appreciated that this
3 0 duty cycle has been arbitrarily selected and that the time interval can be
either increased or
shortened.


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In this patent document, the word "comprising" is used in its non-limiting
sense to
mean that items following the word are included, but items not specifically
mentioned are not
excluded. A reference to an element by the indefinite article "a" does not
exclude the
possibility that more than one of the element is present, unless the context
clearly requires that
there be one and only one of the elements.
It will be apparent to one skilled in the art that modifications may be made
to the
illustrated embodiment without departing from the spirit and scope of the
invention as
hereinafter defined in the Claims.

Representative Drawing