Waste Heat to Electricity? 330
Darwin_Frog writes: "Recent advances in thermionics at MIT lets waste heat generate electricity, thus pushing entropy one step further down the chain. These devices work at a temperature around 250 deg. C, instead of around 1000, so cars can augment the alternator by using the waste heat in the exhaust system to produce power for onboard electronics and A/C."
Matrix style (Score:4, Funny)
Re:Okay, this pisses me off [offtopic] (Score:2, Insightful)
Nah, it must be a conspiracy.
Jesus, get over it.
Isn't everyone bored of comments complaining about moderation or suggestion moderation?
Everything that says "mod this up/down" or "why did this get modded up/down?" should get modded into oblivion as a matter of course. (He said breaking his own rule, please mod me down
Hmmm... (Score:4, Interesting)
less power required= less pollution
Re:Hmmm... - might ruin smokestack effect (Score:5, Informative)
The goal of a smokestack is to get the harmful exhaust away from the ground long enough that it disperses sufficiently before touching down.
This is done with convection. The hot gas in the tall stack creates the draw that powers it and blows the plume up after it leaves the stack, the hot plume continues to lift itself until it bleeds off too much heat, then it starts coming back down, but presumably dispersed enough to not be too noxious.
The smoke stack was designed with a known gas temperature and dispersal requirement and a desire to minimize masonry. If you take away heat from the gas you will reduce your plume altitude and cause it to come down in a more concentrated region.
I doubt you can use the thermo-generated electricty to run blowers to compensate. The `no free lunch' law of thermodynamics will probably forbid that. (Unless blowers are much more efficient than convection.)
Now, if you are just bleeding off waste steam then it would work, but most of the energy in steam is the expansion from water to steam, there is relatively little left in the puffy clouds.
Mostly unrelated note: I used to live in Pittsburg in a community where all the houses were required to have slate roofs, stone or brick exteriors and no wood trim. Even the window frames were metal. It was a fire-proof community from the days when the steel mills spewed lots of solids including hot cinders. The plume was powerful enough to carry those large distances fast enough that they were still hot enough to start a fire.
Re:Hmmm... - might ruin smokestack effect (Score:2, Funny)
But not long enough to learn how to spell the name of the city, apparently.
Re:Hmmm... - might ruin smokestack effect (Score:2)
To some extent, the purpose of a smokestack is to get the junk that comes out of it to disperse widely, over lot of people far away who can't do much about it, rather than locally, over the people close enough to it to be able to do something about it politically.
Re:Hmmm... (Score:3, Interesting)
Agreed!
Now, for all the naysayers and trolls out there who can't see how this could possibly work I want you to stop and think for a second!!.. You're not going to glue these things onto the outside of your stock exhaust system. You're going to design a new exhaust system that incorporates this technology AND hopefully optimizes the waste heat recovery without increasing the accoustic and chemical emmissions or reducing performance. How would that be done?
Well you want to begin by increasing the surface roughness on the inside of the exhaust piping to increase the surface area and thin the boundary layer which will increase the convective heat transfer coefficient. Okay, so now we have a heat exchanger that should remove heat from the exhaust stream at a greater rate than previously, however, the penalty for this is an increased pressure drop and a non-optimal inlet temperature for the catalytic converter. So, you reduce the length of the piping prior to the catalytic converter and possible increase the diameter of the piping.. Better yet, because the typical catalytic converter sold by Corning produces a huge pressure drop, why not design a nice smooth diffuser with some internal fins that trades the separation induced pressure drop developed within Corning's catalytic converter for one that results in improved heat recovery.. The point to all this is that there are a lot of design changes that will probably need to be made, but there's no reason why recoverying waste heat to improve efficiency should be considered impossible or even difficult.. Given a particular TEG, the design optimization problem is something a senior mechanical engineering student should be able to sort out in a week or two..
Re:Hmmm... (Score:2)
These thermo-electric generators in space probes are driven from heat generated by decay of radioactive elements or small solid state fission cores and are all a few tens to a few hundred kW in size. compare that to a nuclear station which is 500,000 to 1,250,000 kW (electric output). A rather big diff.
Re:Hmmm... (Score:2)
By careful selection of materials, ENECO scientists are creating highly efficient, solid state conversion devices, called "thermal diodes," that will operate from 200 to 450 Celsius -- typical temperatures for waste heat and for concentrated solar radiation.
This is exactly what the article says. This quote doesn't specifically say that the "waste heat" in question can be waste from nuclear and fossil-fuel burning plants. I would guess that most of the heat generated in either of these plants is used to boil water to turn a steam turbine (the part where electricity is actually generated), so leeching off that heat before that would be kind of pointless. However, I did a web search, and I noticed in this PDF [www.sujb.cz] that the steam entering the steam turbine at this power plant is at 256C. It doesn't say what the temperature is afterwards. Perhaps there is enough excess heat when the steam leaves to get some extra power using this technology?
As a side note, the article specifically mentions "concentrated solar radiation". Perhaps solar power plants (the kind which use mirrors to concentrate light on a water tower, I suspect) might get over 200C, yet waste a lot of that energy.
Introducing... (Score:5, Funny)
Re:Introducing... (Score:5, Funny)
Warning - Blatant Karma Whoring follows (Score:2)
Re:Introducing... (Score:2)
Overclocker Creates Rift in Space-Time Continuum [bbspot.com]
Nice but not the end of entropy (Score:5, Interesting)
According to the article, this "breakthrough" is a reverse Peltier junction with about twice the efficiency of current semiconductor thermoconverters. Nice, but nothing revolutionary.
I think it's quite excessive to claim this will reduce entropy. Although I agree that if it's economically deployed in, say, cars, it will supplement the alternator.
Could this new junction actually replace the alternator for producing electricity in a car? Let's see: assume a car has a 100 HP internal combustion engine. That's 75 kW. Two third of this is wasted in heat. Typically, the radiator gets about half of this heat (the other half is dissipated away in radiant heat or through the exhaust. Assume further that 20 percent of this can be recovered and converted to electricity (for a really efficient semicon pile). That's 75 * 2/3 * 0.50 * 0.20, or 5 kW. That's more than a good SUV alternator. So this could actually work, provided it's reliable and not too expensive.
You'll need a battery for the short runs, though.
Re:Nice but not the end of entropy (Score:2)
I think they meant reduce the delta of entropy.
Re:Nice but not the end of entropy (Score:5, Insightful)
Re:Nice but not the end of entropy (Score:4, Informative)
Also, there was no mention of replacing the battery. In fact, I believe it was: You'll need a battery for the short runs, though.
Maybe read the post a little harder next time before responding in a such a know-it-all tone?
You forget, it runs on waste heat (Score:4, Insightful)
A hybrid vehicle would probably shut down the engine at idle and eliminate that waste-heat stream, so the thermal converter would be more useful as a way to increase the general efficiency level of the powertrain. If you can get an extra 10% off the 40% of the heat which is rejected through the exhaust, that's 4% of your fuel value; added to a 30% engine thermal efficiency, you've gained 13%. That's nothing to sneeze at.
Is that right? (Score:2, Insightful)
Doesn't a 100HP (75kW) internal combustion engine actually consume 300HP of chemical energy to make its 100HP of mechanical energy if it's 33% efficient? So the waste heat would be 200HP or 150kW.
Re:Nice but not the end of entropy (Score:2)
It's not by any means an end of entropy *fright*, but it is a solid-state heatpump (alternately, to some degree, heat->electrical transducer) with an efficiency rivalling that more efficient mechanical systems.
An earlier
While that's still not very efficient, it is good enough to use on 'recycling' waste heat. Do something economical and plate car-radiators with this material, bleeding off the heat to give back electricity and you've already won a tiny battle.
Mostly, however, it seems likely that this material will be used as a pretty efficient way to turn electricity into cold. Not as cool perhaps as recycling waste heat, but still pretty chilly....
Re:Nice but not the end of entropy (Score:2)
I was thinking about something like this the other day. Couldn't you just claim that the heat produced by the engine is an intended effect ("I meant to do that") and declare that you have created an engine with 100% efficiency.
Re:Nice but not the end of entropy (Score:2, Insightful)
True, but only by a limited percentage. It is tremendously easier to keep an engine block cooled to 250C than is to keep cold side of the generator cooled to say 75C. Heat radiates at the 4th power of temperature. It takes several times the radiative area to maintain 75C than 250C.
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Re:Engine heat (Score:2)
That goes way up if you ditch the radiator, but it's kinda short-lived afterwards.
That depends on the engine. I have an uncle that's worked around some ceramic based diesels that do not have radiators. They are very efficient, but it takes quite a while for them to cool down in order to do any sort of work on them. He's said that it's not uncommon for them to be glowing at the end of the day when they turn off the shop lights.
Re:Engine heat (Score:2)
Portable devices (Score:2, Interesting)
Use on Hybrid cars? (Score:5, Interesting)
Another thing is how do these "thermal diodes" compare to a Peltier Element in heat conversion to electricity?
Re:Use on Hybrid cars? (Score:2)
Re:Use on Hybrid cars? (Score:2, Informative)
Re:Use on Hybrid cars? (Score:3, Informative)
It doesn't do this by converting the heat into electricity however. What it does is effectively act as an alternator, converting the kinetic energy into electricity. The loss of kinetic energy slows the vehicle to a stop while charging a series of batteries. Thus, no heat from brake pads in the first place.
Relevant quote from that article on techtv [techtv.com]:
Thermal diode := Peltier Element (Score:4, Informative)
Anyonw know how much they cost. (Score:5, Insightful)
It'd be great if we could use this for cheap solar cells. Regular solar cells are pretty expensive. (I'm almost convinced that other industries are screwing with the market to make them cost so much). Anyhow, does anyone know how much this new stuff would cost? PS: nuclear's my favorite, but it's too easy for the govt to regulate.
Huh? (Score:2)
oops (Score:2)
Re:Huh? (Score:2)
Honestly, didn't you ever burn your name into leaves with a magnifying glass? Concentrating solar energy is pretty easy...just use a curved mirror or a lens. 480 degrees would be no problem at all.
thermodynamics, and entropy, and all that (Score:5, Funny)
- You can't win.
- You can't break even.
- You have no choice about playing.
Any closed system ends up in the state of most disorder, and all systems are closed if you look at the boundaries carefully. No matter how hard you try, no matter what ingenous things you do, in the end, the dealer wins and everything is dust. Cold dust, at that. The more energy you expend enforcing order, the more chaos you cause. There are no wins in technology, only a prolonging of the inevitable loss. So while I'm sure this new doohickey is neat, somewhere, Carnot is laughing and his cycle is tapping you on the shoulder snickering to itself.Re:thermodynamics, and entropy, and all that (Score:3, Insightful)
What this does do is allow us to design more efficient processes than before. That's a cost savings, a resources savings, and quite allowed by Carnot.
Re:thermodynamics, and entropy, and all that (Score:2, Interesting)
You don't need an expert for this one, you just need to think about it for a minute.
The way we use heat to generate electricity is by converting linear motion into rotational motion in a generator. We don't create the linear motion, really... You make water hot and give it only one place to go, and when it expands it goes there. Same deal with geothermal energy, even wind energy (though heat isn't involved in creating the linear motion, there).
So, if you want to just randomly generate electricity from a warm room, all you have to do is provide one exit for the warm air from the room, and have it lead to a colder room. You put a turbine in that passage, and you'll be able to convert the linear motion of the warm air moving into the cold room into rotational motion and turn a generator.
Problem is, you have to come up with a "cold room" that does not enter equilibrium with the warm room, and even if you come up with one of those, you're really not going to see particularly fast linear motion, unless the temperature difference is very great.
On the other hand, I really sucked at physics in school, so I could be wrong. :)
Re:thermodynamics, and entropy, and all that (Score:2)
Agreed, but is this *necessarily* so inefficient as to be impractical? I.e. is it that it can't work, or have we just not figured out how to do it?
anyway, it still wouldn't answer my question. What I'm confused about is the following:
We can convert electricity directly to heat, without having to "cool something else down" in the process. Why doesn't it work in reverse?
Re:thermodynamics, and entropy, and all that (Score:2)
Re:thermodynamics, and entropy, and all that (Score:2)
Re:thermodynamics, and entropy, and all that (Score:2)
The fact that it's a logarithm makes me wonder how it can have units (namely joules per kelvin, the units of heat capacity). Then again, as I said, I'm no expert.
Re:thermodynamics, and entropy, and all that (Score:2)
IAAP (I Am A Physicist)
S = k log (Omega / C)
Omega's the phase space volume of a given macroscopic state. C is a constant with the same dimensions (whose value, and incidentally its dimensions and those of Omega, depend on how many particles are in the system). log (Omega / C) is indeed dimensionless. But Boltzmann's constant k isn't. :-)=
It would be possible to measure energy and temperature in the same units, in which case Boltzmann's constant would be unity and entropy would be dimensionless. But it's usually more convenient to use ergs (or joules or eV) for energy and Kelvin for temperature.
[TMB]
Re:thermodynamics, and entropy, and all that (Score:5, Informative)
At a fundemental level, entropy is a measure of the number of accesible states of a system for a given energy distribution. Presumably you know that temperature is really just a statistical measure of average kinetic energy in a substance. In the simple case of a uniform temperature gas, it's possible to compute the entropy directly, by (a process analogous to) counting the possible ways to arrange the molecules and distribute their kinetic energy such that you still have the same temperature. (Okay it's not really counting cause there is [usually] a continuum of positions and energy values, but the idea is there, only with more integrals.)
Roughly speaking a system is "ordered" or "disordered" based on how much freedom it has in distributing the energy in it's heat. For instance, in highly complicated and stable configurations (e.g. DNA) you can infer that the heat gets distributed only in ways that don't break down the basic structure. Of course with enough heat it will no longer be stable, but that's a different case.
While the number of accesible internal configurations for the heat energy is the basis for entropy, very few people actually use this. What is actually used is a set of laws mathematically derived from this which can be directly applied to macroscopicly measurable quantities. Chemists know more about these areas than I do, but I'll cover a few of the basics.
The most important is known as the Second Law of Thermodynamics, stated simply "Entropy always increases (or stays the same)." Whenever you do anything that moves energy (such as heat) around, the net entropy will increase (except in those rare cases when it stays the same). It is possible to locally decrease the entropy of one system, but you are guaranteed to increase the entropy of everything else by at least the difference.
There is another important trick about entropy. It tells you that it's impossible to transfer energy from heat to any other form with 100% efficiency. Not only that but you can't even do it with arbitrarily close of 100% efficiency unless you have something who's initial temprature is arbitrarily close to 0 degrees Kelvin. Heat engines, any device that changes heat into other forms of energy, depend on having a difference in temperatures available (for instance, cool river water versus hot steam pipe). If you just have a box sitting at room temperature, it can't work.
There is an interesting caveat here. The Second "Law" and most of how we typically apply entropy are based upon something called the Fundemental Assumption of Thermodynamics. Roughly stated: "All possible energy configurations are equally likely". As it turns out this is rarely ever exactly true, but it is so nearly true in almost every concievable macroscopic situation that it makes no difference. Entropy always increases is a mathematically certain law derived from the fundemental assumption and mathematical definitions of temperature, etc, but it is still concievable that their might be systems where the fundemental assumption doesn't apply and entropy might decrease. Over the years there have been a few suggestions for how to build such a thing (mostly at a quantum mechanical level), but no one has ever succeeded.
If someone does build a box that sits on a desk and converts ambient heat into energy output, then they are almost certainly guaranteed a Nobel prize. On the other hand there may be something better than the fundemental assumption, which is exactly true and excludes all possibility of such a wonderful, energy giving black box.
Re:thermodynamics, and entropy, and all that (Score:3, Insightful)
There is energy in everything that has heat. To extract that energy you have to do one of two things: make it colder or decrease it's entropy.
Thermodynamics and conservation of energy guarantee that any mechanical process that makes it colder will cost more energy to perform than the difference between the energy contents in the cold and hot states. Thus you can't have any net gain of energy through a mechanical cooling.
What you can do is bring it into contact with something cooler. Heat energy is transfered from the hot thing to the cool one and in the process you can extract some energy. This is what the devices in the original story do. In fact, ultimately this is what all thermal power sources do, though the details may be obscured by changes in pressure, volume, etc. If you have a convenient hot source, such as "waste" heat, or geothermal power then you can bring it into contact with ambient temperatures and extract power while it cools.
You want to extract heat from the air. Doing it this way, and supposing there is (optimistically) an average differance of 3 degrees C between the ground and the air above it, you could get at most 1% of the energy transfered between the two. This is the thermodynamic ideal. No system will ever do better over so scant a temp difference near room temperature. Air doesn't have that much energy, nor is it a very good conductor of heat, so it doesn't seem like this would ever be worthwhile.
So, yes, you could get energy from the air that way, but that doesn't seem to be what you want. As I said, no mechanical process will give you positive energy gain, and you don't have a cool spot to compare it to, so what else. The other option is to decrease entropy. I don't know how to break the Second Law, so I want to take the entropy and shove it somewhere else. I decrease the entropy of my stuff, which means I get energy out. Unfortunately I increased the entropy of that other stuff, which means I had to put energy in! Thermodynamics tells us that the only time you win in this situation is if that other stuff was colder than the stuff you started with. Yet again you need to have a temperature difference to get any benefit.
So no, you can't extract energy from the room all by itself. You need a temperature difference if you hope to have a net output of energy. Unless of course you know how to build the magic black boxes that lead to a net decrease in the entropy of the universe, in which your Nobel prize and billions await.
Re:thermodynamics, and entropy, and all that (Score:2)
Excellent explanation, dragons_flight, thanks.
I will now grudgingly accept the known laws of physics, and find another field in which to seek my Nobel prize.
Re:thermodynamics, and entropy, and all that (Score:2)
Sorry, I was a little snippy because entropy is one of few concepts in physics that I've ever had trouble accepting.
Anyway, I actually learned something on
Hmmm... (Score:4, Offtopic)
I'm all in favor of government-sponsored research. They have the resources to investigate stuff with great benefits but staggering R&D costs. I'm all in favor of universities conducting the sponsored research. Grad students are cheap (I know, I was one for many years) and the brainpower is not less than one finds in industry. However, when the government pays a university to do something new, the university's benefits should be the equipment bought for the research and the prestige that comes from doing it first/best/cheapest.
Re:Hmmm... (Score:2)
Giving the private-sector sponsors some real incentive to keep it up only makes sense.
Chances are that you won't be paying licensing fees through those commercial implementors, because their funding of research at MIT has gained them access to the license already.
Re:Hmmm... (Score:4, Informative)
DARPA essentially funds research laboratories to perform research projects that will further advance technology related to DARPA interests. In my case, the research was unclassified, and our group was able to colloborate with other groups and colleages, present our research at conferences, as well as publish our methods/systems/data in scientific journals.
The laboratories that DARPA funds are either university laboratories, FFRDCs (Federally-Funded Research and Development Centers), and commercial laboratories (ie, IBM or Motorola research labs, for instance). It is usually standard practice for employees of all the above labs, upon the beginning of employment, to sign contracts handing over patent rights to the employer (ie, the FFRDC or the company). Actually, I'm not sure about students, as I haven't signed any patent forms yet. But did when I was an employee of MIT. So did Richard Feynman when he worked for Los Alamos (FFRDC).
So, essentially, DARPA has certain technological goals it wants to achieve, and funds a variety of sources to help achieve them. Usually for each specific project, DARPA funds a variety of research labs, and has them compete for further funding. The research labs in turn present their results at least annually for funding renewal. Eventually, DARPA gets it's results (or lack of them), and gets what it needs in terms of advanced technology, and then cna use that technology within more advanced systems.
I do not know specifically what kind of strings come attached with DARPA funding. However, I would imagine that most likely the research labs themselves get some significant percentage of patent rights as a bonus for conducting DARPA research. Otherwise there is no incentive for, say, Boeing to research a new type of stealth aerofoil if DARPA holds on to all patent rights. I know my boss at MIT had his share of patents, but of course, MIT essentially owns said patents.
Note that DARPA's ultimate purpose is to get better technology into Defense-related projects. They advocate using COTS (Commercial Off-The-Shelf) hardware/devices whenever possible. That is, don't waste $$$ designing your own op-amp if Analog-Devices has one that's within your specifications. Of course, you must roll your own if the COTS op-amps don't meet your bandwidth/linearity/bias/power/etc requirements. So, DARPA doesn't care about who gets the patent rights for that op-amp, they want the research that makes use the op-amp. So, in this example, your tax dollars are already going to Analog Devices and helping their own patent processes.
Your concerns about tax dollars funding university patents are either too narrow or too broad. Realize DARPA funds commercial entities as well as FFRDS too, which have similar patent processes. However, DARPA's fundamental purpose is to fund advanced research projects to further American defense interests. That's what it does, and it will support commercial, government, or university research labs to achieve this goal. It's a government agency, so obviously it is funded with tax dollars. I don't think DARPA cares about patents, as long as it can utilize the fruits of the research.
Re:Hmmm... (Score:2)
Some defense guys somewhere in the US government decide that, after running into many difficulties trying to find hidden Taliban hideouts, that the armed forces need better heat-vision technology. Specifically, higher sensitivity and resolution are required.
DARPA comes forward with the Super-Cool-Heat-Vision (SCHV) program to fund research specifically aimed to advance heat-vision technology. The SCHV program is allocated $20 million dollars annually, for 4 years.
DARPA puts out Announcement of Opportunity describing the SCHV program, and invites research labs to participate. The research labs, in turn, submit proposals describing how their specific laboratory can further the technology, and gives specific goals that they believe they can achieve within the allotted time frame.
DARPA chooses the best programs, based on attempted goals as well as quality of research (ie, if the goals are grand but, as is often the case, depend on "magical non-existent devices" it's basically ignored).
DARPA allocates the $20 million to the different projects. Annually, DARPA checks each group's status to determine the next year's funding to that group. Sometimes groups are not funded the next year due to lack of beneficial results.
Eventually, the SCHV program is finished. Some groups have come up with useful heat-vision devices and prototypes.
Here I'm not sure of the details regarding patents and IP issues. I don't know if Company XYZ has to pay licensing fees to the research groups if it uses the technology. But eventually, company XYZ offers commercially-available heat-vision goggles that are far more useful than the previously-availably heat-vision devices. The US Army will then order 100,000 units from company XYZ. Company XYZ makes $$$.
DARPA's purpose was to further the progression from concept to obtainable entity.
is it more efficient than turbines? (Score:5, Interesting)
If this can be more efficient than a turbine, we can have solid-state power plants. Nukes are nothing more than a complex method of boiling water to push a turbine: if we can replace the water, we have an order of magnitude less waste! Not to mention that the core stuff is much easier to deal with than heavy water. Plus, with no pumps or pipes to break, it becomes even safer than it already is.
Or other things, say laptops? PDAs? Naturally all these kinds of applications are XYZ years off, but just imagine what would happen when we get the effiency of these things up? I'd bet that boiling water to turn a turbine is real low efficiency: if we cut out the turbine step alone, that should increase effiency by a whole lot.
This is truly cool shit.
Re:is it more efficient than turbines? (Score:2, Informative)
1. In a light water reactor you got two circuits. The water of the inner circuit comes into contact with radioactive material and can get slightly radioactive itself. The inner circuit is completely closed.
The outer circuit is coupled to the inner one via a heat exchanger. It drives the turbine and is closed, too.
Then after the turbine, the water of the outer circuit is further cooled down with an heat exchanger and river water.
So where is the waste produced? Even the water of the inner circuit becomes only slightly radioactive and is not replaced.
2. Graphite core reactors do not use water as a moderator. But it is still used for cooling. If there is an emergency, something like a peltier element will not be able to reduce the heat fast enough.
It would be more interesting to use the new system with something like MRTs (hope that's the word - those thingies used in sattelites).
Re:is it more efficient than turbines? (Score:2, Insightful)
or so I've heard.
Re:is it more efficient than turbines? (Score:2, Interesting)
That depends on a lot of factors.
How hot is the water being discharged? How big and how fast is the river receiving the discharge? And what ecosystem is already present?
Raising a stream temperature two degrees farenheit won't make a huge difference. Maybe a slight increase in plant productivity and a slight decrease in dissolved oxygen. That increases biological oxygen demand and at the same time decreases the available oxygen to meet that demand. I know what you're saying-increased plant productivity should increase dO2, but the oxygen tends to outgas once the water is saturated or close to it. And gases are less soluble in warmer water than cold. That's why trout don't live in warm water.
Anyway, two degrees isn't likely to be a huge whammy. Ten degrees would probably be very significant.
FWIW, a slight increase can often improve fisheries. Wolf Creek Reservoir in Kansas is the cooling pond for a nuclear power plant. The slight warming effect from the plant has done wonders for the fishery present. And then the stories are legion about prime fisheries being destroyed by warmer water-pacific anchovies, for instance. You really can't generalize too much when it comes to ecology.
And yes, I am a fisheries biologist/acquatic ecologist. Either I have some experience or I've managed to fool a lot of professors and the hiring officer at the state DNR :-)
Re:is it more efficient than turbines? (Score:4, Informative)
The waste comes from the approximately 65% of the original heat pumped into the primary circuit being lost to the river. You have to condense the steam coming out of the turbine so you can pump it. It takes a *lot* of energy to condense this steam back to water. You may not be raising a particular gallon of river(or ocean) water by more than a few degrees (usually less than 5-8F) but you are moving a whole pisspot full of cooling water through your condenser. So the total energy rejected to the environment is quite large. Real world example, the plant where I work is 34.2% efficient, which is actually pretty good for a large steam cycle power plant. The reactor core pumps about 3400MW of heat into the primary circuit and we get about 1175MW of electricity out of the turbine generator, the vast majority of the rest (2225MW) is transferred to the 1,000,000 GPM of ocean water used to cool that pesky steam back into water so it can be pumped.
Now if you could design an economical steam pump (or better yet a two phase pump - steam in and water at higher pressure out) your billions of $'s would be waiting for you. You would be able to knock the stuffing out of the Rankine Cycle and increase plant efficiency into the 50-60% range overnight.
Re:is it more efficient than turbines? (Score:2)
Reversing entropy (Score:2, Funny)
And it came to pass that AC learned how to reverse the direction of entropy.
But there was no one to whom AC might give the answer of the last question. No matter. The answer---by demonstration---would take care of that, too.
For another timeless interval, AC thought how best to do this. Carefully, AC organized the program.
The consciousness of AC encompassed all of what had once been a Universe and brooded over what was now Chaos. Step by step, it must be done.
And AC said, "Let there be light!"
And there was light---
Isaac Asimov, The Last Question
use waste heat as -- heat (Score:3, Insightful)
It's nice when people come up with better technology, but the inefficient use of energy in the US right now is not a technological problem, it's a political problem. Let's hope that we'll eventually be doing well enough that it will really become a technological problem.
Re:use waste heat as -- heat (Score:2)
Re:use waste heat as -- heat (Score:2)
There are other ways to use waste heat. (Score:2, Interesting)
The next is the poor overall efficiency. MIT says they get 2X times the efficiency. From Photonpower.com [photonpower.com] I remember a 5% efficiency, so lets be generous and claim 15% efficiency.
Yet, with the use of stirling engine technology A $90 750Watt engine [omachron.com] or the mystical Ginger [dekaresearch.com] or IT [jedstar.com] you can use waste heat and get power. Stirlings will move with as little as a 2C temprature difference. 90% as a CHP is possible [whipsergen.com]
If you want to get excited about the idea of heat/electricity, then go take a look at some Naval research [sciencedaily.com] that could provide room grade AC w/o state change presently used.
But this technology? Not that exciting, and that is ONLY because of the high temprature.
Meteor? (Score:2, Offtopic)
Re:Meteor? (Score:3, Funny)
Four smaller ones? Imagine reclaiming the heat from a cluster of these...
CPU heat == inefficiencies (Score:2, Interesting)
Re:CPU heat == inefficiencies - not all of it (Score:2)
It turns out that because you need to represent state in a stable mechanism, and you can't change the stable state without using energy that there is a lower bound on the energy required to perform a given calculation.
I have forgetten everything else, and I suspect it is many orders of magnitude smaller than current cpu power usage, but it is enough to break the '==' operator on the parent's title.
Not enough information yet (Score:5, Insightful)
You down with Entropy? (Score:2, Funny)
Yeah, you know me!
For the unintiated, MC Hawking [mchawking.com] lyrics follow.
MC Hawking is Stephen Hawking, physicist and gangsta rapper. Despite three critically acclaimed albums and nearly ten years on the mic, Stephen Hawking remains virtually unknown as a musician. mchawking.com [mchawking.com] is devoted to Stephen Hawking's career as a lyrical terrorist [ampcast.com].
Harm me with harmony.
Doomsday, drop a load on 'em.
Entropy, how can I explain it? I'll take it frame by frame it,
to have you all jumping, shouting saying it.
Let's just say that it's a measure of disorder,
in a system that is closed, like with a border.
It's sorta, like a, well a measurement of randomness,
proposed in 1850 by a German, but wait I digress.
"What the fuck is entropy?", I here the people still exclaiming,
it seems I gotta start the explaining.
You ever drop an egg and on the floor you see it break?
You go and get a mop so you can clean up your mistake.
But did you ever stop to ponder why we know it's true,
if you drop a broken egg you will not get an egg that's new.
That's entropy or E-N-T-R-O to the P to the Y,
the reason why the sun will one day all burn out and die.
Order from disorder is a scientific rarity,
allow me to explain it with a little bit more clarity.
Did I say rarity? I meant impossibility,
at least in a closed system there will always be more entropy.
That's entropy and I hope that you're all down with it,
if you are here's your membership.
Chorus
You down with entropy?
Yeah, you know me! (x3)
Who's down with entropy?
Every last homey!
Defining entropy as disorder's not complete,
'cause disorder as a definition doesn't cover heat.
So my first definition I would now like to withdraw,
and offer one that fits thermodynamics second law.
First we need to understand that entropy is energy,
energy that can't be used to state it more specifically.
In a closed system entropy always goes up,
that's the second law, now you know what's up.
You can't win, you can't break even, you can't leave the game,
'cause entropy will take it all 'though it seems a shame.
The second law, as we now know, is quite clear to state,
that entropy must increase and not dissipate.
Creationists always try to use the second law,
to disprove evolution, but their theory has a flaw.
The second law is quite precise about where it applies,
only in a closed system must the entropy count rise.
The earth's not a closed system' it's powered by the sun,
so fuck the damn creationists, Doomsday get my gun!
That, in a nutshell, is what entropy's about,
you're now down with a discount.
Chorus
Hit it!
Doomsday, kick it in!
Cold Fusion Redux (Score:4, Flamebait)
Peter L. Hagelstein (Re:Cold Fusion Redux) (Score:2, Interesting)
I thought that name was familiar! Gary Taubes' excellent book on the genesis of "Cold Fusion", Bad Science [amazon.com], gives a thorough and not particularly kind account of Prof. Hagelstein's role in those events.
You'll still have a net loss... (Score:3, Interesting)
Example: You put a heat-based gizzmo on your car's exhaust pipe. The temerature (and thus pressure) in the exhaust system goes up, making the engine less efficient and making you use more fuel to go the same distance.
Example: You put one on your CPU. Same deal, except your cooling system now has to work harder to keep it at a reasonable temperature, and thus uses more power.
Example: You wear a swatch. It takes a little bit more energy each time you move your arm. If you want to power a computer the same way, you'll soon be too tired to type.
The key point is in every case you will have to put more energy in than you get back out. That's why perpetual motion machines do not and can not work.
-- MarkusQ
Re:You'll still have a net loss... (Score:2)
It's not perpetual motion, but an attempt to retain energy that is now simply radiated away.
Re:You'll still have a net loss... (Score:2, Interesting)
But heat isn't free energy (free in the physics sense, not in the open source sense). True, you can get energy from a difference in temperature, but only by slowing the flow of heat that would have otherwise taken place (just like damming a river) and thus raising the entropy (in this case, temperature). Now, doing so will make your engine run hotter, and thus less efficient, and you have a net loss.
Suppose you do something to cool the heat sink to make up for this. Then you have two cases to consider: either 1) you are using energy to do this, or 2) you have a passive way to do it. In case 1 you are still at a net loss, but in case 2 you might well be doing better than the original system. But you've then changed the base case--if you used the passive cooling trick (a heat sink or whatever) on the original system, you would have gotten a greater gain, so your gizzmo is still costing you.
-- MarkusQ
Re:You'll still have a net loss... (Score:3, Interesting)
Um, the catalytic convert is already there, and it gets rather hot. Bolting a few of these gadgets there, and on the engine block and in the radiator, won't make the temperature go up any, nor will it impede the flow of exhaust.
Mind you, I doubt it'd fully replace an alternator, but it'd help. The alternator robs horsepower, too, and if these gadgets are "free" (as in do not take more work to run), the net effect should be to increase fuel economy.
This says nothing about the cost and complexity, however. I'm not sure that making these cheap, robust and able to run along with an alternator will be a trivial exercise.
Re:You'll still have a net loss... (Score:2)
Your thinking here is slightly askew. Consider your CPU example. The device is converting heat energy into electrical potential. That means there is LESS heat energy in the CPU. That means the cooling system needs to work LESS to keep the CPU at a reasonable temperature. Your first example is similarly broken: removing energy from the system cannot possibly increase the temperature. Placement of the device might influence exhaust flow, but only if you place the device in a stupid place.
The cost or mass of the device might be important, but your arguments about the device creating more heat in the system seem to be missing the entire point of what the device does. I suspect you're thinking along the lines of "the gizmo must contact the hot surface, therefore the cooling systems have less contact, therefore it's like a constricted pipe holding back the flow of heat, therefore the cooling system has to work harder". This isn't how it works. You can make the surface area as large as you like (think of radiators).
Thermodynamic efficiency limits (Score:5, Informative)
- (T1 - T2)/T2
where T1 is the temperature at the hot side, and T2 is the temperature at the cold side. Both of these temperatures are measured from absolute zero.This is why extracting energy from something that's just a little warmer than its environment is very inefficient. With the hot side at 100C and the cold side at 20C, you're limited to about 20% efficiency in theory, and will be lucky to get half that. Power plants generate steam at upwards of 600C, not just above the boiling point, for exactly this reason. Gas turbines run even hotter. Solar plants for power production typically focus enough energy on a target to reach the 600C level, as Solar Two in Mojave does.
You just can't extract much power from things that are merely warm. They have to be really hot.
Fallacy alert! (Score:2)
For instance, what about a Stirling engine? It has a low "efficiency" according to your definition--but it uses literally any heat source at extremely low temperature differentials. Which engine is more efficient in a practical sense, the one that uses barrel after barrel of precious oil or the one that produces household current from sunshine and snow?
Cars are great... but that's not all !!! (Score:2, Insightful)
Quite nearly every home contains dozens of devices that let off lots of energy while in use. Think of your oven, dryer, toaster, refrigerator, furnace... dare I say woodstove?!? Lining these heat-driven devices with such a product could prove valuable.
Consider the open flame of a gas range literally belching heat, much of which escapes into the air or is absorbed by the metal around it. What if the oven and catch-plates below each burner were lined with a hard-coated version of the device? Maybe in the common home this would prove impractical, but surely in commercial kitchens where ovens and stoves are perpetually fired such an implementation would drastically cut down on the total electricity used.
In older homes where radiators are the norm, this might even provide an economical way to prevent burns from leaning up against those pesky pipes!!!
.
This really isn't new (Score:2, Interesting)
http://www.adsx.com/images/Generator1.html
But the really interesting part is how this company plans to use it. They want to use it along side their digital angel product. Wireless biomonitoring that never runs out of batteries!
Cheaper and more efficient solar power? (Score:3, Interesting)
The very best commercial solar cells today are about 18-20% efficient. The best (research) cell on record, was 32% efficient. It's really too bad they don't give any more specifics on this semi-conductor based device, because it wouldn't be too hard to figure a rough solar cell efficiency equivalent (based on the area of a concentrating lens or mirror)
Now perhaps a more interesting use of such a device would be to increase the efficiency of fuel cells, which themselves are not so efficient and produce lots of waste heat. In a residential setting, this heat can be used for hot water and during winter months. But in a vehicle, I can't think of much use otherwise. Powering headlights, A/C, etc. would be great. Especially if they were white LED headlights of course.. (-;
For your reading pleasure:
http://www.nrel.gov/hot-stuff/press/5399world.h
http://acre.murdoch.edu.au/refiles/pv/text.html
So what they're really trying to say is... (Score:2)
*groan*
Replacing or augmenting cooling towers (Score:3, Interesting)
I've always been struck with how much energy is thrown away in cooling towers at turbine-based electric generating plants.
Just a little background for people who don't understand the function of a cooling tower. A turbine plant turns it's turbines by converting a liquid (typically water) to a gas (steam). Once you have the steam, you have to cool it down if you want to use it again or if you want to efficiently discard it. Some plants are designed to cool it down to the point where very little additional heat will boil it again, but this can be tricky. Some plants have been designed such that the waste steam is cooled in heating buildings through steam radiators, but it can be problematic finding customers for this steam, especially year round.
If we have an efficient way to convert this steam to energy as we cool it, then the efficiency of these plants could go way up.
On a related note, I wish the politicians were seriously working towards about energy efficiency, alternate fuels and new oil exploration now. I only hear half measures and partisan wrangling. It's like the politicians seem to believe that we can't have BOTH more energy efficiency and new energy sources. I'd like to be less dependent on some of the foreign oil now. Some of those areas just aren't looking too stable these days.
Wind Generators (Score:2, Interesting)
"... and A/C" (Score:2, Insightful)
Except the air conditioning cooling system in a car runs directly off the drive system, and not on electricity. The heater runs directly off of heat in the car's cooling system. Consequently, this development really has no impact on vehicle air conditioning or internal environment, with the exception of running a couple relays and a control circuit.
A good thing for gas turbine supporters? (Score:2, Interesting)
And could this be used to augment power used with gas turbine generators at hospitals, on ships and oil platforms or even APU's in airplanes?
Ethan
Re:Neat Idea, but not terribly useful... (Score:2, Insightful)
Personally I'd put more stock in a vehicle powered by hydrogen.
Re:Neat Idea, but not terribly useful... (Score:2)
Wouldn't it have been easier to say "40 degrees"?
-Legion
Re:Neat Idea, but not terribly useful... (Score:2)
Coincidence no doubt.
Re:Neat Idea, but not terribly useful... (Score:2, Informative)
Granted that people talk about how combustion engines waste heat, but no one ever seems to adress how that very heat is neccesary for many parts of the world. I suppose with vehicles, electic cars are a good idea for those in cities that mainly would just need to drive across town, but lets face it; many people use vehicles like an SUV just to drive across town.
Re:Neat Idea, but not terribly useful... (Score:3, Interesting)
IANAS, but I believe that today's newest and most efficient coal, oil, and even nuclear power plants can at some point be looked at as a simple heat -> steam -> turbine system, the same concept that's powered locomotives for over one-hundred years! As you'd imagine, such a system is terribly inefficient.
Thermionics, as I understand it, eliminates the "middleman" of the equation by translating heat directly to electricity. It certainly will be interesting to see how this develops on a commerical and thus much larger scale.
EXTREMELY Useful (Score:3, Informative)
To date, combustion based systems have the highest energy density of any portable energy source (barring fission reactions). Therefore, there will always be a use for it.
Perhaps automobiles won't necessarily need them - we can afford to carry additional weight - the fuel/weight ratio for automobiles is evidence of this - you can carry a LOT with a small amount of fuel for a car - and you can then drive for a long time.
But what about flying vehicles? Fuel/weight ratio is EXTREMELY important. The more efficiency that we can get the better. The best part about this is that it might remove the need for an alternator, which drains the power and adds weight to any flying device (which is significant for the small vehicles, such as the automonous surveyor helicopters used by the U.S. military). Improvements in fuel usage can mean a big deal for the aircraft industry.
Of course that's not the only industry that will benefit. Heat-differential technology is used as a power source for some areas...have you heard of geothermal and solar power plants? Know how those work? What if they could double their output? That would be significant.
Re:Neat Idea, but not terribly useful... (Score:2, Interesting)
Chrysler has a diesel hybrid in development, a prototype called the ESX3, that currently is getting around 72 mpg. The main problem for them is *cost*. As time passes, this will go down. I don't know if they reclaim engine heat, but I doubt it.
Ford *does* have an all electric prototype but it, and any early all-electric cars would be primarily designed for the folks who want a strictly "in-town" car. This notion is already catching on in the form of NEV's (Neighborhood Electric Vehicles).
But, yes, this sort of technology will be probably be pointless within 20 years, at least for automobiles. May have some other uses, however.
More info (Score:3, Informative)
Re:More info (Score:4, Informative)
Probably not (Score:2)
Who knows, maybe with better materials it might someday be practical for use in PCs, but not for a while.
Re:Thermionics? Environmentally friendly?! (Score:2, Informative)
Re:Heatsinks for Power (Score:3, Informative)
You *might* extend battery life for a small length of time (measured in tens of minutes at the most) by recycling some of the waste heat, but entropy still rules. You cannot recycle all of the waste heat, so you will be unable to run your device for anything close to indefinitely.
-Legion
sorta missing the point (Score:2)
I couldn't care less what gets done with that energy... put a nice fluorescent light inside the case or something.
Re:sorta missing the point (Score:2)
*foreheadslap*
And I even just made another post [slashdot.org] explaining this to someone. I really shouldn't try to think right after a nap.
Re:Desert? (Score:3, Informative)
Using something like this requires a temperature GRADIANT... i.e., you could be in a desert that is 5000 degrees, and could NOT use that temperature (i.e. ambient air energy) to generate energy with a junction like this without some form of lower temperature location.
You must have two areas with a temp. gradiate difference bewtween the two that you can place this device across... in this case, the gradient can be lower (250 degrees) and is more efficient. This gradient comes from the difference in termperature between the exhaust and the surronding air.
It's all based upon the tech of peltier junctions.
Re:This would be useless in automotive.. (Score:4, Interesting)
If the heat is being converted to electricity then there will be less heat. Lower heat in the exhaust alone means lower engine temperatures because the exhaust sytem radiates the most heat near the engine at the headers (the part where the exhaust comes off of each cylinder for you non-car types). Since thats where the exhaust is hottest thats where the devices would be mounted. A lower exhaust temperature means a lower overall engine temperature.
Secondly, the big step is going from 1000 degrees down to 250 degrees. Taking that 250 down to 180 or 160 would likely allow these devices to draw heat from the engine itself. Having these devices draw energy would reduce the work a typical liquid cooling system needs to do, allowing it to be reduced in size.
Newer cars and performance cars are replacing belt driven components with ones powered electrically, most notably fans and water/coolant pumps. Elimiating belts allows the engine to put more power to the wheels rather than turning an accesory. The catch is that these devices need more power from the battery and alternator. Alternators are presently limited to about 150-200 amps, enough for a stripped race machine to run its accesories, but not enough for a street driven car with lights, music systems, and long continuous driving. These thermocouples would add more electrical power to the system and use more of the energy produced by the combustion.
The automotive example is a bit advanced for the time, but in todays science community a potential commercial use is the best way to get money for new ideas.
Sorry if that went on too long, or was too automotive for you slashdot geeks.