Possible New solution to convert waste heat into energy
Perseverance, NASA’s 2020 Mars rover, is powered by something very desirable here on Earth: a thermoelectric device, which converts heat to useful electricity.
On Mars, the heat source is the radioactive decay of plutonium, and the device‘s conversion efficiency is 4-5 percent. That’s good enough to power Perseverance and its operations but not quite good enough for applications on Earth.
A team of scientists from Northwestern University and Seoul National University in Korea now has demonstrated a high-performing thermoelectric material in a practical form that can be used in device development. The material—purified tin selenide in polycrystalline form—outperforms the single-crystal form in converting heat to electricity, making it the most efficient thermoelectric system on record. The researchers were able to achieve the high conversion rate after identifying and removing an oxidation problem that had degraded performance in earlier studies.
The polycrystalline tin selenide could be developed for use in solid-state thermoelectric devices in a variety of industries, with potentially enormous energy savings. A key application target is capturing industrial waste heat—such as from power plants, the automobile industry and glass- and brick-making factories—and converting it to electricity. More than 65 percent of the energy produced globally from fossil fuels is lost as waste heat.
“Thermoelectric devices are in use, but only in niche applications, such as in the Mars rover,” said Northwestern’s Mercouri Kanatzidis, a chemist who specializes in the design of new materials. “These devices have not caught on like solar cells, and there are significant challenges to making good ones. We are focusing on developing a material that would be low cost and high performance and propel thermoelectric devices into more widespread application.”
Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, is a co-corresponding author of the study. He has a joint appointment with the Argonne National Laboratory.
Details of the thermoelectric material and its record-high performance will be published in August in the journal Nature Materials.
In Chung of Seoul National University is the paper’s other co-corresponding author. Vinayak Dravid,the Abraham Harris Professor of Materials Science and Engineering at Northwestern’s McCormick School of Engineering,is one of the study’s senior authors. Dravid is a long-time collaborator of Kanatzidis’.
Thermoelectric devices are already well defined, says Kanatzidis, but what makes them work well or not is the thermoelectric material inside. One side of the device is hot and the other side cold. The thermoelectric material lies in the middle. Heat flows through the material, and some of the heat is converted to electricity, which leaves the device via wires.
The material needs to have extremely low thermal conductivity while still retaining good electrical conductivity to be efficient at waste heat conversion. And because the heat source could be as high as 400-500 degrees Celsius, the material needs to be stable at very high temperatures. These challenges and others make thermoelectric devices more difficult to produce than solar cells.
‘Something diabolical was happening’
In 2014, Kanatzidis and his team reported the discovery of a surprising material that was the best in the world at converting waste heat to useful electricity: the crystal form of the chemical compound tin selenide. While an important discovery, the single-crystal form is impractical for mass production because of its fragility and tendency to flake.
Tin selenide in polycrystalline form, which is stronger and can be cut and shaped for applications, was needed, so the researchers turned to studying the material in that form. In an unpleasant surprise, they found the material’s thermal conductivity was high, not the desirable low level found in the single-crystal form.
“We realized something diabolical was happening,” Kanatzidis said. “The expectation was that tin selenide in polycrystalline form would not have high thermal conductivity, but it did. We had a problem.”
Upon closer examination, the researchers discovered a skin of oxidized tin on the material. Heat flowed through the conductive skin, increasing the thermal conductivity, which is undesirable in a thermoelectric device.
A solution is found, opening doors
After learning that the oxidation came from both the process itself and the starting materials, the Korean team found a way to remove the oxygen. The researchers then could produce tin selenide pellets with no oxygen, which they then tested.
The true thermal conductivity of the polycrystalline form was measured and found to be lower, as originally expected. Its performance as a thermoelectric device, converting heat to electricity, exceeded that of the single crystal form, making it the most efficient on record.
The efficiency of waste heat conversion in thermoelectrics is reflected by its “figure of merit,” a number called ZT. The higher the number, the better the conversion rate. The ZT of single-crystal tin selenide earlier was found to be approximately 2.2 to 2.6 at 913 Kelvin. In this new study, the researchers found the purified tin selenide in polycrystalline form had a ZT of approximately 3.1 at 783 Kelvin. Its thermal conductivity was ultralow, lower than the single-crystals.
“This opens the door for new devices to be built from polycrystalline tin selenide pellets and their applications explored,” Kanatzidis said.
Northwestern owns the intellectual property for the tin selenide material. Potential areas of application for the thermoelectric material include the automobile industry (a significant amount of gasoline’s potential energy goes out of a vehicle’s tailpipe), heavy manufacturing industries (such as glass and brick making, refineries, coal- and gas-fired power plants) and places where large combustion engines operate continuously (such as in large ships and tankers).
The title of the paper is “Polycrystalline SnSe with a thermoelectric figure of merit greater than the single-crystal.”
See more here: phys.org
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Howdy
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So It’s a peltier on steroids?
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Jerry Krause
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Hi PSI Readers,
“The material needs to have extremely low thermal conductivity while still retaining good electrical conductivity to be efficient at waste heat conversion.”
As a chemist who studies matter and its properties, I know that a good electrical conductor has always been observed to be a GOOD THERMAL Conductor and a METAL.
I could be wrong but it is the responsibility of the author of this article to identify any matter that even begins to contradict that which I have just generally stated.
Have a good day, Jerry
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Jerry Krause
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Hi PSI Readers,
It is a fact that I had not read beyond the statement I quoted. So reading further I find: “More than 65 percent of the energy produced globally from fossil fuels is lost as waste heat.”
And ask: Doesn’t this have something to do with the often stated 2nd Law of Thermodynamics??? What is waste heat??? Waste heat is ENERGY that is incapable of producing PRACTICAL WORK.
But, of course, I could be wrong! However, I ask: Could these SCIENTISTS be WRONG???
Have a good day, Jerry
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Howdy
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Hmm. Waste heat is only waste if It can’t be utilized after the initial process, so “waste heat” from an internal combustion engine is used as passenger compartment heating, thus not completely wasted.
Early steam engines were single cylinder, but later developed into “triple expansion”, so less heat was wasted compared to the single cylinder. The steam went through 3 cylinders of differing pressures. The Titanic used these engines.
https://ingeniumcanada.org/scitech/artifact/canadian-vickers-ltd-triple-expansion-steam-engine
If you want to see such an engine in operation: https://youtu.be/KhlJp1VZMB8?t=335
Steam engines are marvelous machines, and steam locos, especially so.
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Jerry Krause
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Hi Howdy and PSI Readers,
The headline of the article is: “Possible New Solution To Convert Waste Heat Into Energy”. My first instinct was to point out the accepted fact that heat is energy. However, in the first sentence of the article I read: “a thermoelectric device, which converts heat to useful electricity.” From which I understood that the topic of the article was the possible conversion of heat into electrical energy capable of doing work.
Your comments are about the early development of MORE EFFICIENT STEAM ENGINES deals with trying to achieve the maximum possible work, as defined by the 2nd Law of Thermodynamics, for any real HEAT ENGINE. Which has been concluded to be not possible because any heat engine must have moving parts and moving parts means FRICTION. And FRICTION produces HEAT.
Have a good day, Jerry
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Jerry Krause
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Hi Howdy and PSI Readers,
The headline of the article is: “Possible New Solution To Convert Waste Heat Into Energy”. My first instinct was to point out the accepted fact that heat is energy. However, in the first sentence of the article I read: “a thermoelectric device, which converts heat to useful electricity.” From which I understood that the topic of the article was the possible conversion of heat into electrical energy capable of doing work.
Your comments are about the early development of MORE EFFICIENT STEAM ENGINES deals with trying to achieve the maximum possible work, as defined by the 2nd Law of Thermodynamics, for any real HEAT ENGINE. Which has been concluded to be not possible because any heat engine must have moving parts and moving parts means FRICTION. And FRICTION produces HEAT.
Have a good day, Jerry
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Jerry Krause
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I have no idea how my comment was posted twice. Hopefully, someone can tell me how to avoid this because it has happened before to my comments and even those of others.
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Howdy
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“Waste heat is ENERGY that is incapable of producing PRACTICAL WORK”
So a triple expansion increases output over a single cylinder which expelled everything It couldn’t use, by reusing the waste product two more times. On the Titanic the output from the engines, which is normally wasted, was further employed to drive a turbine. Thus that waste steam was converted into work.
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Howdy
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Or are you saying anything left over that is to all intents and purposes incapable of doing anything further is waste? If it can still be used for heating it’s not waste.
“concluded”
Then the truth is still out there since conclusion is not fact.
Howdy
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Best leave the thermodynamics Jerry, or my head will be done in.
I’ll keep using my version, where fx, I can use gases previously exhausted into the atmosphere from my boiler, thus wasted, to warm a second water tank using a bit of copper pipe. Simpler to understand, and cuts down on waste. That works for me on the practical side.
Howdy
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The comment system has a few problems Jerry.
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dnomsed
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Current Peltier coolers/heaters tend to have a very low COP, and small temperature lift.
I’ll look into these new one to see if I can get them to do what I researched a few years ago.
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Jerry Krause
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Hi Howdy,
I have not accurately defining what I have been writing about the 2nd Law and thereby created your confusion. This topic is fundamentally important so I will try to correct my mistakes for you and other PSI Readers whom I might also confused. But it will take a while for while Einstein stated “If you can’t explain it simply, you don’t understand it well enough.”, he also stated: “Make everything as simple as possible, but not simpler.” So, I conclude one of my mistakes was that I was trying to make the topic of the 2nd Law simpler than possible.
Have a good day, Jerry
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Jerry Krause
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Hi Howdy and PSI Readers,
This comment is long relative to most comments, however short relative to most articles.
I first studied the 2nd Law of Thermodynamics from ‘Physical Chemistry 2nd Ed’ written by Daniels and Alberty. So I will quote extensively from what they wrote in their textbook. Capitalizing that which I consider most important.
“Although various forms of work can be converted completely into heat and ideally may be transformed completely into one another, it is found that ONLY A FRACTION OF A QUANTITY OF HEAT MAYBE CONVERTED INTO WORK IN A CYCLIC PROCESS.” PP 83
“Work may be expressed as the product of two factors—an intensity factor and a capacity factor.” In the case of Mechanical Work the intensity factor is FORCE and the capacity factor is CHANGE IN DISTANCE. PP 35
“The second law of thermodynamics provides a means for CALCULATING THE MAXIMUM VALUE THAT THIS FRACTION MAY HAVE and is directly concerned with the question of whether or not a given change is SPONTANEOUS.” PP 83
“Spontaneous and Nonspontaneous Changes. We are familiar with the fact that many changes occur spontaneously; that is when systems are simply left to themselves. Water runs downhill; gases expand from regions of high pressure to regions of low pressure; chemical reactions proceed to equilibrium; and heat flows from hotter bodices to cooler bodies. For any spontaneous change it is possible to devise, in principle at least, a means of getting useful work. …. Since work can be obtained from a spontaneous change, it is evident that in the occurrence of spontaneous change the system loses capacity to do useful work.” PP 83-84
“The term NONSPONTANEOUS CHANGES is applied to the reverse of a SPONTANEOUS CHANGE, for example, water flowing uphill. NONSPONTANEOUS CHANGES can be made TO OCCUR only by SUPPLYING ENERGY from outside the system. PP 84
Spontaneous changes may be carried out either REVERSIBLY or IRREVERSIBLY. … In order to carry out a spontaneous change REVERSIBLY, it is necessary to oppose it in such a way that the change is carried out very slowly and, in fact, can be REVERSED at any time by making an INFINITESIMAL change in the opposing force. … When a change is carried out REVERSIBLY, the MAXIMUM AMOUNT OF WORK is obtained. Actually, it is not possible to obtain the maximum amount of work from any system with a REAL MACHINE because of losses due to friction and the fact that a truly reversible process must be carried out infinitely slowly. Thus actual processes are always IRREVERSIBLE to a certain extent, and the work obtained is LESS THAN THE THEORETICAL AMOUNT. “ PP 84
“CARNOT CYCLE. Heat can be partially transformed into work if there are available TWO HEAT RESERVOIRS at DIFFERENT TEMPERATURES T(1) AND T(2). … The FRACTION of the heat absorbed at the higher temperature which is converted into work is called the EFFICIENCY of the heat engine.” PP 86
Which EFFICIENCY FRACTION = [T(2) – T(1)] / T(2) PP 87
However, there is a BIG PROBLEM which, I suspect, is not common knowledge to a NON-PHYSICAL SCIENTIST!!! The temperatures of this simple fraction must be Kelvin Temperatures. “T(K) = 273 + T(C)” PP 10
FOR THERE IS NO SUCH THING AS A NEGATIVE TEMPERATURE.
Have a good day, Jerry
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Howdy
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Hi Jerry,
I’ll leave the intricacies to the people best qualified to apply them. Thank you for taking the time to explain.
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Jerry Krause
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Hi Howdy,
Thank you!!! Thank you!!! For I now know that at least one person read what I quoted.
Have a good day, Jerry
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Jerry Krause
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Hi Howdy,
Because I cannot remember your name from the past, I bring to your attention a sequence of articles that have been posted on PSI. (https://principia-scientific.com/the-corvallis-or-uscrn-site-a-natural-laboratory-part-two/)
I encourage you to go the RAWS site and look at the daily temperature oscillations which have been occurring there during the past few days. As well as the data of the USCRN weather station in this natural setting.
For DATA is what SCIENCE is all about.
Have a good day, Jerry
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Howdy
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“For DATA is what SCIENCE is all about.”
I don’t work with graphs, or data as such Jerry. I proceed with something I’m wishing to validate and keep It all in my head. Every time I repeat the validation, things will generally go as expected, but if any oddities arise, I will keep a close eye on any differences occurring and mentally note them. I will never know the true answer so I can definitively state that the process will work the same in every case. Too many variables. I just learn from It.
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Jerry Krause
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Hi Howdy and PSI Readers,
I have reviewed a brief paragraph of a public address, The Value of Science, to National Academy of Sciences at their 1955 by the Nobel Prize Winning Physicist, Richard Feynman. Which address was published in “What Do You Care What Other People Think?” after Feynman had died of cancer in 1988.
But I will begin by quoting Feynman’s preface which explains the purpose of the much earlier address. “When I was younger, I thought science would make good things for everybody. It was obviously useful; it was good. During the war I worked on the atomic bomb. This result of science was obviously a very serious matter: it represented the destruction of people.
“After the war I was very worried about the bomb. I didn’t know what the future was going to look like, and I certainly wasn’t anywhere near sure that we would last until now. Therefore one question was–is there some evil involved in science?
“Put another way–what is the value of the science I had dedicated myself–the thing that I loved–when I saw what terrible things it could do? It was a question I had to answer.
“”The Value of Science” is a kind of report, if you will, on many of the thoughts that came to me when I tried to answer that question.” Richard Feynman
The Brief Paragraph: “I would like to turn to a this value that science has. It is a little less direct, but not much. The scientist has a lot of experience with ignorance and doubt and uncertainty, and this experience is of very great importance, I think. When a scientist doesn’t know the answer to a problem, he is ignorant. When he has a hunch as to what the result is, he is uncertain. And when he is pretty darn sure of what the result is going to be, he is stallion some doubt. We have found it of paramount importance that in order to progress we must recognize our ignorance and leave room for doubt. Scientific knowledge is a body of statements of varying degrees of certainty–some most unsure, some nearly sure, but none ABSOLUTELY certain.”
Howdy, you use different WORDS. “Every time I repeat the validation, things will generally go as expected,” Reproducible Observations (Data). “if any oddities [NEW DATA] arise, I will keep a close eye on any differences occurring [MORE NEW DATA] occurring and mentally note them.”
“I will never know the true answer so I can definitively state that the process will work the same in every case.” You are NEVER CERTAIN as a GOOD SCIENTIST SHOULD BE!!!
Thank you so much for having this conversation with me!!! Other PSI, I very much would like to have conversations with you. For as Feynman stated: Science is a very serious matter.
Have a good day, Jerry
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Howdy
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Hi Jerry,
Richard Feynman and myself, “same difference” I guess. I just didn’t see It like that. Good quote!
I guess the arena of science is another test of “good v evil”. Though just as “evil science”, depending how It’s used, possibly has implications for good sometimes, the opposite, or “good science” used as bad, seems to win more often. Like most things now, corrupted, and helped along the way by further corruption so the true are rarely heard. Is there evil in science? Eye of the beholder I think.
Ditto regarding the convo. Any time.
Take care.
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Jerry Krause
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Hi Howdy and PSI Readers,
As a science student nobody ever suggested I should read Henry Crew & Alfonso de Salvio English translation (1914) of Galileo’s FAMOUS book titled ‘Dialogues Concerning Two New Sciences’. So as a teacher of physical science for more than 20 years I had never suggested, until I finally read it myself, that any of my students should at least read its first paragraph (actually only one sentence).
Which is: “The constant activity which you Venetians display in your famous arsenal suggests to the studious mind a large field for investigation, especially that part of the work which involves mechanics; for in this department all types of instruments and machines are constantly being constructed by many artisans, among whom there must be many who, partly by inherited experience and partly by their own observations, have become highly expert and clever in explanation.”
Having read this, can you explain how it was that Galileo demanded that his book be published in the Italian language in which he wrote it and not in Latin as Newton wrote and had his famous book, ‘The Principlia’, published?
And yes PSI READERS (I do not forget READERS this time) I would welcome any of your comments.
Have a good day, Jerry
Have a good day, Jerry
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