Offshore Technology Conference Houston May 6-9 2002
speonline.spe.org ... exhibitors
GLE thermoelectric generator background information ...
December 2001 Nickle Development Institute Report
1960's Technology Plays Essential Role Today
Low-maintenance units, designed to generate electricity in remote locations, rely on nickel alloys and stainless steels
Nickel magazine, Dec. 01 -- Supplying electricity to 68 corrosion-monitoring stations along a 1,200-kilometre-long liquefied petroleum gas pipeline in India are 68 low-maintenance electric generators.
Built by Global Thermoelectric Inc. of Calgary, Alberta, Canada, the units produce low voltages (typically supplying a few hundred watts or a couple of kilowatts) and are ideally suited to run remote monitoring stations or communications systems.
The generators use technology developed for the Apollo space program, whereby a temperature differential is used to produce a flow of electrons. A burner, fuelled from a propane tank or directly off a gas pipeline, heats a thermopile made of lead-tin telluride, maintaining a temperature of about 540°C on one side, 140°C on the relatively cool side.
"The key to the technology is that there are no moving parts nothing rubbing, nothing wearing out," says Bernie LeSage, vice president of Global's generator division. "You can stick [a generator] on a mountaintop or on a remote pipeline site, and if you can get out there once a year to spend an hour on it, that's great. And if you can't, no harm done."
The high temperatures -- up to 800°C where the burner produces flame -- require the toughness of nickel alloys. Internal fittings employ a variety of nickel alloys such as N06600, N06601, N06625 and N07718 while other nickel alloys are used to custom-build some electrodes. "They're there to take the heat and still provide sufficient strength," says LeSage. "We need high temperature. We need long life."
Global Thermoelectric builds these low-power generators to operate for 20 years in some of the most remote and inhospitable places on the planet. The firm wants to ensure that buyers never find a rusty casing when they check out the merchandise.
"A guy can go back in the field after ten years and look at our product, and it looks as a good as new," LeSage says. "And that's pretty important, because the internals are working as good as new, so you don't want the external packaging to lower the perception of the quality."
To preserve that appearance of quality, Global uses S30400 stainless steel for the cabinets that house its generators, and S31600 stainless if the power pack is destined for a marine environment, such as an offshore gas production platform.
Global is the world leader in building thermoelectric generators, accounting for 99% of the market, LeSage estimates. The firm, founded in 1975, has customers in 46 countries and builds more than 1,500 units each year, with annual sales of up to Cdn$20 million.
nidi.org ... original report with cool pictures supplied by Global Thermoelectric
History of thermoelectric generators ... (excerpts from 1988 report)
THERMOELECTRIC POWER THE ROAD BEHIND AND AHEAD ...William C. Hall
TELEDYNE ENERGY SYSTEMS ii0 West Timonium Road Timonium, Maryland 21093
SUMMARY
Despite its birth in Germany over 150 years ago, it was not until the mid-twentieth century that thermoelectric power technology achieved other than laboratory reference. The requirements for power for space missions encouraged the development of practical conversion of heat to power, using both radioisotope and fossil-fueled fuel sources. Originally narrowly configured for the space missions, thermoelectric power finds employment not only in space, but in terrestrial and marine applications worldwide. Driven by competition from other power sources, and dis\-covering its own peculiar advantages and attributes, the industry continues to seek out new markets and methods.
BACKGROUND
The first line of the original abstract for this paper starts with: "The past fifteen years..." The history of thermoelectrics goes back further than that. So that we can start at the same point, let's note that the German physicist Thomas Seebeck dis\-covered the phenomenon in 1821. He joined two wires of dissimilar metals to form a continuous loop, and found that if the two junctions were kept at different tem\-peratures, an electrical current is generated. The voltage is directly proportional to the temperature differential, and is also influenced by the physical characteristics of the materials. In its simplest form we have the thermocouple, the basis for most tempera\-ture measurements today.
Not much significant use for power production was made of the phenomenon outside the laboratory until the 1950's. Researchers had found that the efficiency was sensitive to the thermal conductivity and the electrical resistance of the thermoelectric materials. The practical production of useful power by thermo\-electric devices awaited the emergence of the semi\-conductor materials, which could provide simultaneous minimal thermal conductivity and electrical resist\-ance. Additionally, it wasn't until the postwar period that situations arose where high reliability and low power requirements combined to create a demand. The space programs provided the technological ? impetus and the financial support to develop systems with low energy demands and the need for long-term reliable power. Even before the launch of Sputnik in 1957, the prospect of extended space missions had initiated research and develop~nent of auxiliary power sources which would complement existing devices such as batteries, fuel cells and photovoltaics.
RADIOISOTOPE THERMOELECTRIC GENERATORS
The basic radioisotope thermoelectric generator comprises an isotopic heat source, a heat sink, and a thermoelectric device to convert some portion of the heat to electricity. Maximum independence is achieved by a self-contained heat source and a static conver\-ter. Since power conversion efficiencies of thermo\-electric devices are low (4 to 8%), the heat source has to have a high thermal density to be useful in an environment demanding minimal launch weight. All these considerations spurred an extensive development program.
The first proof-of-principle application of thermoelectrics for space power was demonstrated to President Eisenhower in early 1959 with the grapefruit-sized SNAP-3, fueled with polonium-210, having a half-life of 138 days. Subsequent fuel development resulted in the selection of plutonium-238, which combined an extended half-life of 87.7 years with alpha radiation, requiring minimum shielding. Since that time, all RTG's launched into space have been fueled with some form of plutonium.
The SNAP-3RTG is shown to President Eisenhower
Jo.ua~ 16,1959
Following the SNAP-3 development, 1961 saw the successful launch of the TRANSIT 4A and 4B satellites, each with a SNAP-3A plutonium-fueled generator. The SNAP-3A was superseded in 1963 by the SNAP-9A, with a power capability of almost 27 watts, ten times that of the SNAP-3A. Shortly after came the development of the SNAP-19 and SNAP-27 series. The SNAP-27, at 63 watts, found its primary usage on board APOLLO-II and its successors, while the SNAP-19 started its career with NIMBUS III, and went on to greater heights aboard PIONEER I0 and ii in 1972 and 1973. We still hear from these wanderers, although one has left the solar system, and the other is about to exit.
During 1972, the U.S. Navy launched the TRIAD navigational satellite with the TRANSIT RTG, whose 36 watts augmented the batteries. After that, the SNAP-19 was modified to withstand the requirements of the VIKING missions and made possible two successful landings on Mars in 1975. The higher power require\-ments of LES-8 and 9 dictated the development of the highly versatile MHW (Multi-Hundred-Watt) RTG, which ultimately made possible the spectacular VOYAGER missions to Jupiter and Saturn, continuing to Uranus, and now approaching Neptune.
...
FOSSIL FUELS
This brings us to the conventional commercial thermoelectric generator, fueled with LPG or natural gas, with some promise of liquid fuels, such as JP, diesel or kerosene. These developed in the 1960's, and by the start of the seventies, the major domestic producers were General Instrument Corporation and Minnesota Mining and Manufacturing Company (G.I. and 3M). G.I.'s product line was acquired by Teledyne in 1970, and in 1976, 3M sold its technology to a number of its employees. This group moved to Bassano, Alberta, Canada, and has established itself as Global Thermoelectric Co.,Ltd. There have been a couple of others who have entered the fossil-fueled TEG market, such as Gulf General Atomics and Energy Conversion Devices, but these efforts have been discontinued. At the present time, over ten thousand gas-fueled thermo\-electric generators have been deployed worldwide, mostly produced by Teledyne and Global.
So much for history. Now for the current applica\-tions of gas-fueled units. The most obvious possible user is the communications industry: radio, tele\-vision, microwave and telephone. Radionavigation is a significant application, where a temporary or perma\-nent TEG installation can power a fixed transponder, locating a ship or vehicle to within a few feet. This is most often used in dredging, minelaying or mine\-sweeping operations. The dismantling of the Suez Canal and Haiphong Harbor minefields involved this program.
In the mountains of the United States and Canada, there are a number of television relay stations using TEG power to operate mountaintop translators, relaying television signals to receivers in the topographical shadows. TEG-powered geophysical stations keep an eye on Mt. St. Helena' activity visually and electronical\-ly, while other TEG-powered seismic instruments watch for Southern California to head north. There are also snow-depth measuring devices and water level monitors, all requiring remote power, and contributing signifi\-cantly to water management.
Temporary transponder station for Arctic petroleum exploration
The above uses are all low-power; probably less than i00 watts per site, and are fueled by LPG, pro\-pane or propane-butane mixtures. In the petroleum industry, the presence of natural gas in pipelines and wellheads makes the TEG quite attractive by negating the largest drawback: fuel availability. By tapping into the gas source, the TEG operator can use genera\-tors at power levels which would be prohibitively expensive if one had to transport fuel to the site. We have seen Algerian thermoelectric power installations as high as 3 kilowatts for cathodic protection of natural gas pipelines, although a level of 3(X)-600 watts is more usual.
Amidst the turmoil of the Middle Fast, TEG power protects pipelines and provides power for instrumen\-tation in Iran, Iraq, Turkey, Saudi Arabia and the UAE. Fifty-five offshore platforms in Abu Dhabi's upper Zakum gas field are outfitted with 300-watt TEG installations for SCADA power supplies. Similar gener\-ators are also aboard a number of platforms further east in the Bon*bay High field, replacing battery and photovoltaic arrays. The generators in some of these installations have a regulatory agency's approval for operation in the hazardous atmospheres characteristic of gas wellhead situations.
Louisiano gas metering station powered by TEG using transport natural gas
The TEG's competitors are batteries, photo-voltaics, wind power, diesels and closed-cycle vapor turbine generators. Some of these, however, have co~aplementary roles with TEGs. Batteries find use as power buffers, where they accommodate power spikes and are recharged by the TEG during quiescent periods. Wind and PV units are finding the TEG a useful com\-panion to reduce capital cost and provide a reliable backup if the supply of natural energy is lost.
This latter partnership is a relatively new devel\-opment. Owing to its thermal inertia, constant power output and conventional flame-ignited start, the TEG has been a continuously operating device. On occasion, a remotely-actuated electric start had been incor\-porated, activated by a transmitted signal or by a detected deficiency in system condition. Meanwhile, the use of renewable power devices had expanded, with the accumulation of some reliability experience. Un\-foreseen lack of wind or sun for extended periods necessitated compensation by increasing the size of the PV or wind system, especially in the battery bank. This at times resulted in excessively large, heavy and expensive installations.
The advent of the microprocessor, plus a systems approach to specific situations has given birth to the hybrid, combining PV and/or wind power with TEG. The advantage to this acc(xsmodation has been an optimiza\-tion of life cycle cost as a function of capital and operating cost. Not only that, but one of the products of thermoelectric conversion is waste heat, a com\-modity in demand in high latitudes where low solar availability is a characteristic of the winter season. Therefore, one can obtain a power backup and warmth at the same time, activating a TEG with either a low systems voltage or low environment temperature para\-meter. As designers learn to shed conditioned pre\-judices, and perform objective evaluations, the hybrid will find more and more employment in the remote power field.
Fuel cost has always been a problem with thermo\-electric generators, except along the gas pipelines. The propane, butane, or mixtures are contained in pressurized tanks or cylinders, where the metal weight frequently exceeds 40 percent of the gross weight. The cost of shipment therefore frequently exceeds the cost of the fuel. By reducing fuel consumption, the hybrid designs reduce the relative disadvantage of this factor, but the problem remains. For years, the utili\-zation of liquid fuels has been discussed, but we have for so long trumpeted the reliability of "no moving parts", that it takes a leap of faith to incorporate a fuel pump and atomizer into a situation demanding high reliability.
The crux of the problem is undoubtedly familiar to designers: development cost. Without a defined market, companies are reluctant to invest in leaps of faith. However, the Department of Defense has been active in sponsoring this technology, to the point where proto\-type thermoelectric generators using diesel, methanol, kerosene, or JP-series fuel now exist. Unfortunately, the military specifications are such that the design exceeds the normal requirements for a "commercial" unit, to the point that small quantity prices are prohibitive. Some reflection on this dilemma is cur\-rently underway, with the aim of using the basic concepts as developed to produce a useful liquid-fueled generator at a realistic price.
The advantages of such a unit, especially in a military application, are obvious. Silence, reli\-ability, portability, and a low IR signature come to mind. Even discounting the silence and IR character\-istics, the availability of a 100-watt generator weighing less than 50 pounds with a volume less than two cubic feet has a lot of attraction for tacticians, especially if the fuel can be carried in jerry-cans instead of 200-pound cylinders.
OTHER APPLICATIONS
There are some other uses of thermoelectric de\-vices which are not immediately obvious. These include the use of thermoelectrics to provide self-generated power for space heaters, stoves, and the like. The principle is to operate a heat source for one of these uses, and to divert some of the heat through a thermo\-electric array. The power generated is enough to operate a fan, blower, controller, or such for support of the device's required function.
The opposite to the Seebeck effect is the Peltier effect, discovered in 1834. Electrical current passed through a thermoelectric assembly generates heat on one side and cools the other. We have seen this used in some commercial products such as thermoelectric food coolers and warmers. Not immediately obvious is the development of an industry providing devices which use the Peltier effect to cool critical electrical and electronic components. Among these components are resistors and various transistors installed in sensi\-tive equipment and installations.
In a relatively short period of time, more and more people have become aware of the capabilities of thermoelectrics. Systems designers of the more ad\-vanced countries, searching for solutions, have initiated large-scale generator projects. Frequently, the ultimate user is located in one of the less-developed countries, with a limited electrical power infrastructure. Some of these countries also have natural resources, such as petroleum products, which are marketable and useful if available. Thermoelectric power, properly applied, contributes to improving conditions by facilitating internal communications and transport. By examining the current applications, techniques and possibilities, we can predict further worldwide expansion of these.
In summary, the thermoelectric community can look back on a history of achievements not otherwise attainable, a status of useful employment, and a future increasingly varied. The orbital and explor\-atory space programs are not complete, there is a continuing conventional need for remote unattended reliable power, and one can foresee an expansion in applications as our challenges and ingenuity combine to increase our technical capability and our confidence.
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