Pipeline thermoelectric generator assembly

A thermoelectric generator assembly. The thermoelectric generator assembly comprises a thermoelectric generator. The thermoelectric generator has a hot junction flange, a cold junction flange and a thermoelectric power output. The thermoelectric generator assembly generates electrical power from heat differentials for use in powering field devices in industrial process monitoring and control systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to co-pending application Ser. No. 11/070,860, filed Mar. 2, 2005, titled “PROCESS DEVICE WITH IMPROVED POWER GENERATION,” the content of which is hereby incorporated by reference in its entirety; and reference is also made to related co-pending U.S. patent application Ser. No. 11/529,767 entitled “THERMOELECTRIC GENERATOR ASSEMBLY FOR FIELD PROCESS DEVICES,” filed Sep. 28, 2006, the contents of which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to industrial process control or monitoring systems. More specifically, the present invention relates to thermoelectric power generation for such systems.

Field instruments are typically widely distributed throughout a process plant and are connected by process control loops to a control system. Field instruments typically require a supply of electrical power for operation. The electrical power can be provided by the control loops themselves or by separate power wiring to the instruments. The amount of power required by each field instrument is usually quite small, and is typically on the order of about 50 milliwatts or less.

When wiring is used for control loops, the wiring is typically enclosed in electrical wiring conduits which require mechanical mounting for support on the framework of process equipment over long distances. Often, the cost of wiring a field instrument over long distances exceeds the cost of the field instrument itself.

When a wireless communication loop is used to communicate with a field instrument, the wireless communication loop does not provide a power supply to the field instrument, and separate power supply wiring is needed.

While the power required for a typical field instrument is extremely low, field instruments are often located in very hot, dangerous or inaccessible locations in the process plant. In such locations, it may be impractical to use a chemical battery as a source of low power in a field instrument. The environments in such locations are often dirty or shielded from sunlight, making use of solar cells for power supply impractical. Solar cells and batteries, in the plant environment, require too much maintenance to be usable for power supply in many field instrument applications.

Process equipment in plants typically include boilers, steam piping, heated tanks and other equipment that are heated or cooled to a temperature that different than ambient air temperature in the process plant. Large temperature differentials are present, and waste heat flows between the ambient air and the process equipment. The amount of energy lost due to a waste heat flow often greatly exceeds the amount of electrical power required by a field instrument.

SUMMARY OF THE INVENTION

Disclosed is a thermoelectric generator assembly. The thermoelectric generator assembly comprises a thermoelectric generator. The thermoelectric generator has a hot junction flange, a cold junction flange and a thermoelectric power output. The thermoelectric generator assembly generates electrical power from heat differentials for use in powering field devices in industrial process monitoring and control systems.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the embodiments described below, a thermoelectric generator assembly utilizes waste heat that flows from heated (or cooled) process fluid in a to an ambient temperature in an industrial process environment. The thermoelectric generator assembly includes a thermoelectric generator device that has a hot junction flange that is spaced apart from a cold junction flange.

The hot junction flange is maintained at a temperature that is near the process fluid temperature by mounting it to a process heat pickup that is coupled to a process heat source. The heat pickup has a shape that adapts to a shape of the process heat source and can take a variety of forms such as a pipeline adapter with a concave arc surface to mate with a corresponding convex arc surface of a process vessel, a combustion heat pickup, a steam line heat sink, or other heat exchange device. The heat pickup is preferably formed of aluminum or copper, and provides low thermal resistance between the hot junction flange and the process heat source. Various types of clamps can be used to hold the process heat pickup in close thermal contact with the process heat source. These clamps can also serve to mechanically mount the thermoelectric generator assembly to the process heat source.

The cold junction flange is maintained at a temperature that is near the ambient temperature. The heat sink can take a variety of forms as described below in portions ofFIGS. 1-8D. The heat sink provides low thermal resistance between the cold junction flange and the ambient temperature in the industrial process environment.

Through the use of a combination of process heat pickups or heat sinks, a large temperature differential is maintained between the hot junction flange and the cold junction flange. A power output of the thermoelectric generator is enhanced by the large temperature differential to provide adequate power to utilization circuitry.

In one embodiment, circuitry coupled to the thermoelectric power output includes a regulator circuit and an energy storage circuit that stores energy in a capacitance. The energy storage circuit senses when the power output exceeds the use requirement and couples excess power to the capacitance. The energy storage circuit senses when the power output does not meet the use requirement and provides makeup power from the capacitance to the regulator circuit. In another embodiment, the utilization circuitry can be put in either a low power shutdown mode or a cold startup mode by command from a wireless link.

The technology has wide applicability to industrial process environments, such as oil and gas, petroleum refineries, chemical processing, food and beverage processing, HVAC, metals and metallurgical processing, mining, textiles, heavy machinery and other industrial process environments.

FIG. 1illustrates a portion of an industrial process plant100. A process pipe102passes through the industrial process plant100carrying a process fluid104. The process fluid104can be steam, hot gas/liquid mixtures, natural gas, oil or chemicals. The process fluid104is heated during at least one part of a process cycle to a temperature that is significantly above ambient air temperature in the process plant100. A temperature difference between the process fluid104and the ambient temperature is typically in the range of 50-100 degrees centigrade during at least one portion of a process cycle for the process plant. During other portions of the process plant cycle, particularly during a plant shutdown and startup, the process fluid is at a lower temperature, and the temperature difference can be less than 50 degrees centigrade.

A first field device106comprises a flow transmitter that senses flow of the process fluid104. The first field device106connects via a loop108to an electronics assembly110. A second field device112comprises a pressure transmitter that senses pressure of the process fluid104. The second field device112connects via a second loop114to the electronics assembly110. A third field device116comprises a temperature transmitter that senses temperature of the process fluid104. The third field device116connects via a loop118to electronics assembly110. The field devices106,112, and116are exemplary field devices and other types of known field devices can be used with the electronic assembly110. The loops108,114,118can comprise two wire controlled current 4-20 mA wire loops, wireless loops, two wire controlled current multidrop wired loops, field busses and other known types of process device loops. In one embodiment, the loops108,114,118are wired loops, and the local storage and transmission apparatus110provides power to the wired loops108,114,118.

A first antenna122(also called transponder122) couples along line124to a transceiver126that is in the electronics assembly110. A second antenna130couples along a line132to a central control computer134. The second antenna130and the central control computer134are remote from the first antenna122. A wireless communication link136is established between the second antenna130and the first antenna122. The wireless communication link136carries process data and command communications between the central control computer134and the field devices106,112,116. In one embodiment, the first and second antennas122,130are directional antennas as illustrated. The wireless communication link136can operate at any suitable band including HF, VHF, UHF, microwave bands, infrared bands and optical bands. Transponders (antennas)122,130can include radio antennas, waveguides or optoelectronic components, depending on the carrier wavelength selected for a particular application.

The electronics assembly110stores process data and utilizes the wireless communication link136for communicating process data between the central control computer134and the field devices106,112,116. With the use of the electronics assembly110, there is no need for communication wiring running long distances between the field devices106,112,116and the central control computer134.

A thermoelectric source140provides a power output142to the electronics assembly110. The thermoelectric source140has a hot junction with a concave arc-shaped pipeline adapter thermally coupled to the pipeline102. The thermoelectric source140has a cold junction with a heat sink that includes spaced-apart protrusions such as pins or fins. The thermoelectric source140is described in more detail below by way of an example illustrated inFIGS. 2-3. A regulator circuit144receives the power output142and provides a regulated power output146.

In this embodiment, utilization circuitry includes the transceiver126and the field instrument interface148which are coupled together by a data bus156. The utilization circuitry126,148receives and is energized by the regulated output146. The utilization circuitry126,148has a use requirement for power in order to provide energization currents to the field devices106,112,116, to power the field instrument interface148and to power the transceiver126. In some embodiments, the antenna122includes active transponder components, and is included in the utilization circuitry that is energized by the regulated output146. In one embodiment, the field instrument interface148includes a control function and provides a process control output160to a field control device. In another embodiment, the field control device comprises a current-to-pressure converter162that provides a control pressure to a control valve164that controls flow of industrial process fluid. The process control output can use a conventional industrial communication protocol such as a two wire 4-20 mA process control current loop, Hart, or other known industrial communication protocol. The control function of the field instrument interface148can be a function of industrial process data received from field instruments106,112,116or can be a function of industrial process data received wirelessly from central control computer134or both.

An energy storage circuit150receives the power output142and couples power from the power output142to a capacitance152at those times when the energy storage circuit senses that the power output142exceeds the use requirement. The energy storage circuit150provides makeup power154from the capacitance152to the regulator144at times when the energy storage circuit150senses that the power output142does not meet the use requirement. The energy storage circuit150selectively couples power to the capacitance152only when the capacitance152drops below a full charge level. The energy storage circuit150couples to the data bus156to sense data that indicates whether the use requirement is being met. The data bus156couples to the regulator circuit144, the transceiver126and the field instrument interface148for obtaining data concerning the use requirement and the power output from the thermoelectric source140. In one embodiment, the data bus156also carries mode change commands from wireless link136and transceiver126.

The field instrument interface148is connected to one or more field instruments106,112,140,162to energize the field instruments106,112,140,162and to communicate data and commands. The power provided to the field instruments106,112,140,162is thermoelectric power.

In one embodiment, the utilization circuitry126,148can be put in a shutdown mode by a shutdown command from the wireless link136. The shutdown command leaves the energy storage circuit150functioning to provide power to the capacitance, such that stored energy is available to the utilization circuitry126,128during a cold startup mode following the shutdown mode. In this embodiment, the utilization circuitry126operates in a low power mode during the shutdown mode and during the cold startup mode. In one embodiment, the capacitance152comprises one or more supercapacitors to provide large energy storage without the use of batteries.

The electronic assembly110, which is typically implemented using microprocessor circuitry, can store and transmit data using thermoelectric power. Data storage can be done locally in electronics assembly110or can be transmitted instantaneously to the central control room. Data transmission can be done in a group or through individual transmission.

FIG. 2illustrates a front sectional view andFIG. 3illustrates a side sectional view of a thermoelectric generator assembly200mounted to a pipeline202. The pipeline202is filled with a hot process fluid204that is flowing in a direction indicated by arrow206. The pipe202is optionally enclosed in a layer of thermal pipeline insulation208to reduce waste heat loss.

The thermoelectric generator assembly200comprises a thermoelectric generator210having a hot junction flange212and a cold junction flange214and a thermoelectric power output216(FIG. 2).

The thermoelectric generator assembly200comprises a heat sink220. The heat sink220has multiple protrusions222that are thermally coupled to the cold junction flange214. Air flow spaces224are provided between the protrusions222. In various embodiments, the protrusions222are generally cylindrical pins, as illustrated, fins or other shapes that provide a large surface area for coupling heat to air in air flow spaces. Other types of heat sinks can be used as well, for example heats sinks as described below in connection withFIGS. 7-8D.

The thermoelectric generator assembly200comprises a pipeline adapter226. The pipeline adapter226has a concave, generally cylindrical, arc surface228that is thermally coupled to the hot junction flange212. The concave arc surface228has a shape and a size to mate with a corresponding convex arc surface230of the pipeline202.

In one embodiment, the concave arc surface228extends over an arc of no more than 180 degrees. In this embodiment, the concave arc surface228is mateable with the convex arc surface230without sliding over an open end of the pipeline202.

A clamp232mechanically couples to the pipeline adapter226by bolts234,236. The bolts234,236are tightened, and the clamp232urges the concave arc surface228toward the convex outer surface230of the pipeline202.

A clamp232mechanically couples to the pipeline adapter226by bolts234,236. The bolts234,236are mounted at an acute angle260with respect to one another as illustrated inFIG. 2. The bolts234,236are tightened, and the clamp232urges the concave arc surface228toward the convex outer surface230of the pipeline202. When the concave arc surface228has a diameter that is larger than a diameter of the pipeline202, outer ends262,264of the concave arc surface228are drawn toward the convex outer surface230as the bolts234,236(which are at the acute angle260) are tightened.

In one embodiment, the concave arc surface228can have a diameter that is larger than a diameter of the pipeline202. In this embodiment, tightening the clamp232compresses the concave arc surface228to fit the pipeline202. In another embodiment, the concave arc surface228has a diameter that is smaller than a diameter of the pipeline202. In this embodiment, tightening the clamp232expands the concave arc surface to fit the pipeline202.

It is thus possible to manufacture a pipeline adapter226that fits a particular nominal pipeline size (such as a nominal 4″ pipe), but that can be fit to pipes with slightly different diameters (different wall thicknesses or pipe schedule size) by compressing or expanding the diameter of the concave arc surface228by tightening the clamp232.

In one embodiment the pipeline adapter226comprises a massive, solid metal body with a large cross-section transverse to a direction of major heat flow, providing low thermal resistance. Aluminum and copper are preferred metals for the pipeline adapter226.

In one embodiment, a layer of thermal insulation material240is disposed between peripheral rims of the hot junction flange212and the cold junction flange214. The thermal insulation material240extends outwardly from thermoelectric generator210. In one embodiment, the thermal insulation material240comprises refractory ceramic material.

The pipeline adapter226is mounted completely externally to the pipeline202. The mounting is completed without cutting a hole in the pipeline202. The use of a thermowell is avoided.

In one embodiment, a thermally conductive coating (not illustrated) that is deformable is provided between the concave surface228and the convex surface230. The thermally conductive coating extrudes out during tightening of the clamp232and leaves a thin layer of coating that fill gaps between the concave arc surface228and the pipeline202. The thin layer reduces thermal resistance between the surfaces228,230. In one embodiment, the thermally conductive coating comprises conventional heat sink grease.

Besides a pipeline adapter or process vessel adapter, other types of process heat source adapters can be uses as well, for example a combustion chamber adapter described below in connection withFIG. 7. Other heat source adapters can be fabricated to fit specific shapes of the heat source without breaching pressurized process fluid vessels.

In one embodiment a temperature sensor250is mounted on the hot junction flange212adjacent to the pipeline adapter226for sensing process fluid temperature. Leads252from the temperature sensor250couple to a temperature transmitter (such as temperature transmitter116inFIG. 1). The use of a thermowell for the temperature sensor250is avoided by placing the temperature sensor250on the hot junction flange212adjacent to the pipeline adapter226. Important process temperature information is obtained without the use of a thermowell. The temperature sensor250is preferably a resistor temperature detector (RTD). Thermal insulation (such as thermal insulation208and240) reduces heat loss from the pipeline adapter226and minimizes any temperature difference between the process204and the temperature sensor250.

The temperature sensor250can provide important diagnostic information concerning the process fluid. If there is leak in the pipe that is carrying a gaseous fluid, then pressure in the pipeline will drop instantaneously which, in turn will decrease the temperature sensed by the temperature sensor250. If the sensed temperature drops below its noise value, an alarm can be communicated to check for a leak. In another situation, if the line pressure increases due to plugged line or other reason where the flow has got choked downstream, temperature of flowing liquid or gas will increase, and another type of alarm can be communicated.

Hence, by measuring the temperature of the pipe line, information about the leak and the plugged line can be detected instantaneously. This is very useful information for the process industries where pipe line is stretched miles after miles. This is true for in-plant piping as well.

As illustrated inFIG. 4, a clamp400can include a spring402that is energized when the clamp400is tightened by tightening bolts404,406. The clamp400is exemplary, and various types of clamps can be used, with or without springs. When springs are included, the springs can be compression springs or extension springs. Springs can be formed in any known shape including coil springs, leaf springs and torsional springs. The use of springs is preferred in order to provide a relatively constant clamping force as the pipeline changes dimension due to thermal expansion. Hose clamps with metal straps that encircle a pipeline and the pipeline adapter can also be used for clamping.

FIG. 5is an illustration of a thermoelectric generator assembly500that emphasizes thermal aspects according to a simplified thermal model. The thermoelectric generator assembly500, which is illustrated thermally, is comparable to the thermoelectric generator assembly200, which is illustrated mechanically. The thermoelectric generator assembly500comprises a thermoelectric generator502that has a hot junction flange504and a cold junction flange506and a thermoelectric power output connector508. The thermoelectric generator assembly500has a heat sink510with protrusions512that are thermally coupled to the cold junction flange506. There are air flow spaces514between the protrusions512. Air flow516(indicated by solid arrows) passes through the air flow spaces514. A pipeline adapter520has a cylindrical concave arc surface522that is thermally coupled to the hot junction flange504. The concave arc surface522has a shape and size to mate with a corresponding convex arc surface524of a pipeline526.

The thermoelectric generator502has a thermal resistance530between the hot junction flange504(at a temperature Th) and the cold junction flange506(at a temperature Tc). The pipeline adapter520and the pipeline526have a thermal resistance532to flowing fluid534in the pipeline526. The heat sink510has a thermal resistance534between the cold junction flange506and the flowing ambient air516. A major heat flow (indicated by open arrows540,542,544,546,548flows through the thermal resistances532,530,534from the flowing fluid534to the flowing air516. Due to the major heat flow, a temperature difference (Th−Tc) is established between the hot junction flange504and the cold junction flange506. The thermoelectric power output508depends upon this temperature difference for generating power. There is an objective to maintain the hot junction flange temperature Th as near as possible to a temperature Tf of the fluid, and there is also an objective to maintain the cold junction flange temperature Tc as close as possible to the ambient air temperature Ta.

The heat sink510has the advantage that the protrusions512provide a large surface area for airflow516to carry heat away to the ambient environment. Because of the large surface area of the protrusions512, the thermal resistance534is reduced, and the cold junction flange temperature Tc is kept close to the ambient temperature Ta. In one embodiment, insulation material (such as insulation material240inFIGS. 2-3) can be added to reduce thermal exposure of the heat sink to the pipeline.

The pipeline adapter520has the advantage of a large mating surface area contact between the concave arc surface522and the convex surface524of the pipeline. Because of the large surface area of the concave arc surface522, the thermal resistance532is reduced, and the hot junction flange temperature Th is kept close to the flowing process fluid temperature Tf.

Since both the hot and cold junction flanges are cooled by flowing fluids, there is an optimized heat flow544through the thermal resistance530. The optimized heat flow is optimized relative to leakage heat flows which are blocked by spacing and insulation. A large available power output508is available.

In one embodiment the thermoelectric generator assembly500includes electronic circuitry such as that shown inFIG. 1. Since the energy storage circuit stores power in a capacitance only when it is needed, only a portion of the power output that is available to meet the power use requirement is actually taken from the power output. Current flow is reduced and the amount of power output used is reduced, and hot and cold junction currents are correspondingly reduced, limiting undesired heating of the cold junction flange506. Semiconductor thermoelectric piles are preferred as thermoelectric sources because of their high efficiencies.

Thermoelectric generator (TEG) technology provides conversion of heat flow directly into electrical power. TEG technology is renewable, has a very long operating lifetime (15 years or more), and is environmentally friendly. The efficiency of TEG depends on the thermoelectric figure of merit which is a function of electrical conductivity, Seebeck coefficient, and thermal conductivity.

As illustrated inFIG. 6, thermoelectric generator technology is capable of converting heat available in a process plant to electrical power which is then sufficient to feed to the microprocessor circuitry in electronic assemblies (such as electronics assembly110inFIG. 1) where power requirements are in the range of 50 to 150 mW for data storage and transmission.

FIG. 7illustrates a plan view of a thermoelectric generator assembly700. The thermoelectric generator assembly700comprises a thermoelectric generator710having a hot junction flange712, a cold junction flange714and a thermoelectric power output716.

The thermoelectric generator assembly700comprises a heat sink720. The heat sink720comprises a plant air inlet722and a plant air outlet724. The plant air inlet722is connected to a plant air line726that receives pressurized air from a plant air source728.

The plant air source728typically comprises an air compressor, pressurized air storage tank, pressure regulators, air filters, air dryers and a heat exchanger which cools compressed air down to near the ambient temperature of the industrial process environment. The plant air source728can be of conventional design and also provided pressurized plant air to plant air utilization devices730such as air actuated valves, bubblers, air motors and other process devices.

The plant air outlet724carries pressurized air away from the heat sink720after the pressurized air has passed through an internal passageway732in the heat sink720. The heat sink720can comprise a block of metal (aluminum or copper, for example) and the internal passageway732can be straight or follow a serpentine path through the heat sink720. Heat flows from the cold junction flange714to the moving air in the internal passageway732. Heat is thereby expelled to the industrial process environment, and the cold junction flange714is cooled by plant air. The plant air that passes through the heat sink720can be either passed on to another plant air utilization device before it is exhausted to the ambient air, or it can exhausted directly from plant air outlet724.

The thermoelectric generator assembly700comprises a combustion chamber adapter740. A door742on a combustion chamber744is provided with a throughhole746. The combustion chamber adapter740passes through the through hole746. In one embodiment, the combustion chamber adapter740mounts to the door742. The combustion chamber adapter740has a heat transfer plate748that is coupled to the hot junction flange712. A shaft750extends from the heat transfer plate748through the throughhole746to a heat pickup752in the combustion chamber744. The heat pickup is shaped to scavenge an appropriate amount of heat from a flame-heated region754in combustion chamber744while not interfering with gas flow in the combustion chamber744. Shapes of the heat pickup752may include a flat plate as illustrated, a grille or other shapes that are compatible with the hot gas flow regime in the combustion chamber744.

In one embodiment, the combustion chamber adapter adapter740is mounted to the door742so that the door742can be swung open for inspection of the interior of combustion chamber744.

In one embodiment, one or more movable shutters756are provided in the combustion chamber744to vary shielding of the heat pickup752from the flame heated region754to provide thermostatic control. The shutters756include spiral bimetallic elements that rotate the positions of the shutters to vary shielding of the heat pickup752to avoid overheating the thermoelectric generator assembly700when there is high heat output in the combustion chamber744.

FIGS. 8A-8Dillustrate exemplary embodiments of the heat sink720.

FIG. 8Aillustrates an embodiment of a heat sink800in which the plant air passes from a plant air inlet802through a passageway804to a plant air outlet806with little restriction or pressure drop. The plant air outlet806is piped to a utilization device808(such as a current-to-pressure converter (I/P) or valve) that maintains sufficient air flow for cooling the heat sink800. A length of pipe810between the plant air outlet806and the utilization device808allow for cooling of plant air before it reaches the utilization device808. In one embodiment, the passageway804is a serpentine passageway to increase surface area for heat exchange with the plant air.

FIG. 8Billustrates an embodiment of a heat sink820in which plant air passes from a plant air inlet822through a passageway824to a plant air outlet826. Plant air is vented to the atmosphere from the plant air outlet826. The passageway824is restricted to limit consumption of plant air by the heat sink820. In one embodiment the restriction comprises a long, narrow serpentine shape for the passageway824. In another embodiment, the restriction comprises an orifice plate825in the passageway. In one embodiment, the orifice plate is positioned near the plant air inlet822, providing additional cooling of the heat sink due to expansion of the plant air passing through the orifice plate. The orifice plate can comprise any know type of orifice or orifices that are suitably sized for the desired consumption of plant air.

FIG. 8Cillustrates an embodiment of a heat sink840in which plant air passes from an plant air inlet842through a valve844and a passageway846to a plant air outlet848. Plant air is vented from the plant air outlet848. The valve844is manually adjustable to set a desired consumption of plant air. In one embodiment the valve848is placed close to the plant air inlet842, providing additional cooling of the heat sink840due to expansion of the plant air in the heat sink.

FIG. 8Dillustrates an embodiment of a heat sink860in which plant air passes through a plant air inlet862, a thermostatically controlled valve864, a passageway866and a plant air outlet868. Plant air is vented from the plant air outlet868. The thermostatically controlled valve864includes a gas-filled temperature sensing bulb870that is thermally coupled to a selected location on the thermoelectric generator assembly for temperature sensing. In one embodiment, the selected location is the cold junction flange714. In another embodiment, the selected location is the hot junction flange712. In another embodiment, the selected location is on the heat sink860near the plant air outlet868. Other selected locations can be used as well. The gas-filled temperature sensing bulb870is pressure coupled via a capillary tube872to a diaphragm874. the diaphragm874deflects as a function of temperature to actuate a needle valve876that regulates flow of plant air.

Combinations of selected features of the embodiments described above are also contemplated. Changes can be made to fit the needs of a particular application. In one embodiment, a hot side combustion chamber adapter is used along with a cold side finned heat sink. In another embodiment, an arced hot side adapter is used with a plant air heat sink on the cold side. In another embodiment, heat sinks are used on both the hot side and cold side of the thermoelectric generator, with the cold side heat sink cooled by plant air and the hot side heat sink heated by steam from a steam line, or heated liquid from a heated process line.

While the embodiments described above show use on a heated pipeline, it will be understood that the embodiments can also be used on pipelines that are cooled below ambient temperature such that the temperature differential is reversed. The pipeline and hot junction flange can be colder than the cold junction flange and ambient, and the thermoelectric generator will function normally. The polarity of connections to the thermoelectric power are reversed in such an installation on a chilled pipeline.