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Creating Power From Wasted Heat
Roland Piquepaille writes "Today, about 90 percent of the world's electricity is created through an indirect and inefficient conversion of heat. It is estimated that two thirds of the heat used by thermoelectric converters are wasted and released. But now, researchers from the University of California at Berkeley have found a new way to convert this wasted heat into electricity by trapping organic molecules between metal nanoparticles. So far, this method of creating electricity creation is in its very early stage, but if it can scale up to mass production it may lead to a new and inexpensive source of energy."
How is this "a new source of power" ? it's just improving efficiency by reducing loss.
So now instead of yelling at my kids for leaving the fridge door open I'll have to get them to leave it open every now and then in order to keep the electricity bill down.
I could really dig have a lower electricty bill in the summer rather than a higher one. When can I build a house with this stuff?
we've seen a lot of "new energy" stories on /. today, and there's been a lot of talk in the media lately, too. but NO ONE is talking about conserving energy. of course, this is an american perspective, and self-constraint is unamerican as it gets.
who cares if we figure out, say, how to meet 10% of our energy needs with new tech when our consumption rises 10% (or more).
a lot of "new energy" isn't really energy. as others have pointed out, hydrogen, is really just a way to transport energy.
it occurred to me recently, that, collectively, humans are like any other organism. we cannot control ourselves from the inside (something to do with goedels theorem maybe), and thus we will overrun the planet until we choke on ourselves -- or run out of energy. so i don't worry about it too much.
oh. whoops. depressing cold day here in st louis today.
mr c
"Physics is like sex. Sure, it may give some practical results, but that's not why we do it." - R. Feynman
Well, there's no mention of current per unit (each, mol, dozen, etc) of each organic oreo, so the voltages are essentially meaningless.
110100 1101000 1101000 1100110 0 1101111 1101000 1100011 1
I hope no one here will forget about the 2nd law of thermodynamics...
http://en.wikipedia.org/wiki/Thermoelectric_Effect
Invented almost 200 years ago. I have a huge box full of Peltier "chips" sitting in my store room..
It's pretty easy to generate electricity from heat. I have a pottery kiln and one method of monitoring temperature is to use a thermocouple hooked up to a "pyrometer". A thermocouple is just two different kinds of metals connected. Somehow, when you apply heat, a voltage develops (I won't pretend to understand how). Now, I'm a cheapskate and because a pyrometer is nothing but voltmeter scaled for temperature, I just use a couple digital multimeters to monitor kiln temps (in the type of firing I do, the measured temperature isn't really relevant -- I'm more concerned with whether the temperature is rising or falling). I typically get 35 - 40 millivolts at my peak temperature (somewhere in excess of 2400 degrees F if I'm doing things right). The cheapo type-K thermocouples I use lose their accuracy as I approach peak temps, but no way am I spending over $200 each for platinum thermocouples.
Anyway, my point, after reading TFA, it became pretty obvious that this stuff would work like a thermocouple, but you could fit many of them over a large area. It's isn't so much "nano-magic", as it would be a miniaturization of an idea that sees daily application. It sure would be cool if they get it functional.
What changed under Obama? Nothing Good
So this means global warming is a good thing. With all the electricity we'll be able to make, it's no problem to just run enough air conditions to solve the problem.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
Computers still are, and probably always will be, a fairly small fraction of electrical consumption. Yeah, data centers are all the way up to 1%... But 1% is 1%. Not a big component... Hell, I'd be more concerned about this - if we replace fossil fuel cars with electric in the next fifty years, electric power used to recharge vehicles will probably become one of the biggest fractions of the total load.
Have you been touched by his noodly appendage?
I think the 3rd law is more appropriate here, since they are basically talking about using the waste heat of an earlier process, and converting part of it to usable energy.
The 2nd law just basically states that any energy conversion process cannot be 100% efficient, AKA "entropy".
In effect, this is adding a secondary process to the first (or possibly list of processes), of which we already know some amount of energy will escape due the 2nd law.
This additional process just makes the overall process more efficient, and does not really add to it above the original process's input energy. However, the 3rd law just states you can't achieve 0 entropy in a process with a finite number of steps. Basically, you can never have a process that is 100% energy conversion efficient.
Probably the more important question is does the increase of enthalopy merit the proposed decrease in entropy? AKA, does the cost of implementing this solution outway the benefit.
Cogeneration only wastes about 1/3 of the energy. That's not too far off from
the Carnot efficiency of 86% for a combustion temperature of 2000 centigrade.
And even the reamining "waste" heat could be used if better planning happened:
district steam, drying and other industrial uses.
Were that I say, pancakes?
...water pollution. Nothing. Zero. It took serious government regulations in a lot of directions at the federal, state and local level and mass civil indignation to do that, because the "market" ALL found it cheaper-better for their "shareholder value and bottom line"- to just dump their toxic waste wherever they felt like it and to transfer health care costs to -anyplace else, downstream usually.
Ya, maybe if we had waited say a few hundred years it might have "corrected", as the remaining few non mutants rose up finally and bumped off the remaining few mass polluters who were left, but for some reason society decided to step in with some stricter laws before it got that bad.
I could name numerous other examples but that is an easily seen one.
Sometimes you just can't wait for the "this quarter's profits" mentality boys to do the right thing. Some things might need to be addressed now, once they are clearly understood to either be a problem now or soon will be, as opposed to waiting around for a long time in an economic and social experiment to see what might happen. And believe it or nuts, there are more important things on this Earth than some corporation's bank balance.
That is not to say that government can't be hugely overbearing and infested with generic mass stoopidity itself,of course it is,I speak out about government abuses all the time, but "the market" is no better really, neither extreme -leave it all to the market (caveat-emptor brand corporatism would be the extreme there) or all to the government(cult of the personality one leader-one party-mass bureaucracy and no one even wants to work any longer except under the whip"- ism government would be the extreme that other way)- is the end all or be all of "solutions". I think what we have more or less constructed- at least semi-regulated markets and at least an attempt at a semi-regulated society via this government thing-is probably the best humans can do at our (barely out of the medieval level intellectually or psychologically) evolutionary stage.
Of the two extremes and the middle, the middle is what we mostly have and falls under the lesser of the three big evils choices. It is imperfect, absolutely no doubt there, but the best we can do right now. What we can do is to keep chipping away at the imperfections on a case by case basis.
Also, from what I read this technology still functions at very low differentials, ie 30 degrees celsius, as opposed to the hundreds that just using two metals requires.
They don't have to be efficient. The wasted heat is used in the building so there is effectively no waste. Any electricity generated is just an added bonus.
Large thermoelectric plants are ~40% efficient. A burner heats water, the steam passes over a turbine (connected to a generator), the steam is then condensed (where all the energy is lost) and pumped back into the water tank so it can be heated again.
My suggested idea would, most likely, use an internal combustion engine at ~25% efficiency. But even at a lower efficiency it is still more efficient then just burning gas at 0%. (Note that the efficiency ratings are for electricity production.)
Willy
"But the common man doesn't understand 'efficiency gains' as something significant."
Yeah, they insulate their houses to save on energy bills just 'cause.
Good to see that some professors can both do research and teach without lacking in one or the other. Professor Majumdar's a nice guy, his heat transfer class was very well taught, really helped get me interested in heat transfer as something to elaborate on for MechE.
Unfortunately, thermoelectric converters based on the Seebeck effect are not going to help with efficiency by a large amount.
Firstly, there is a theoretical limit (Carnot Cycle) to the efficiency of any pure heat engine based on the Second Law of Thermodynamics.
If a quantity of heat Q is taken from a high-temperature reservoir at temperature T2, partially converted into useful work W, and the remainder (Q - W) is deposited into a low-temperature reservoir at temperature T1, then the net increase in entropy is at least
\delta S = (Q-W)/T1 - Q/T2 >= 0.
So the efficiency (useful work generated per unit energy input)
e = W/Q < (T2 - T1)/T2
The waste heat is ultimately deposited into the environment, so T1 can't be much smaller than say 300K.
In a steam engine T2 has to be greater than the boiling point of water (at whatever pressure it is operated), but it is limited by what the materials of which it is composed can withstand. Temperatures of order 1000K are typical. That gives a maximum theoretical efficiency of around 70%. The best steam engines barely reach about half that efficiency.
However, modern power plants (which are not pure heat engines) use a Combined Cycle that can do better by first generating electricity from their fuel with a combustion turbine and then using the waste heat from the combustion turbine to make steam to generate additional electricity via a steam turbine. Their efficiency can reach about 60% of the net calorific value of the fuel.
So you can see that one might be able to shave a few more percentage points off the waste, but it will not at all be the godsend we really need...
IMHO only nuclear power can fulfill that role today.
The "wasted" heat that thermal power plants reject to the surroundings is rejected at a temperature only slightly above ambient. A steam turbine generator has an exhaust steam condenser which operates at a vacuum, where the steam condenses at only a few degrees Fahrenheit above the ambient temperature. There is no significant temperature difference available for the new device to operate with. While thermal power plants do reject over half the fuel energy consumed to the surroundings, it is a myth that this rejected heat can be effectively used. The rejected heat is available at a low temperature, only slightly above ambient, therefore little effective use can be made of it. This is the penalty that the laws of thermodynamics impose on the conversion of heat into work.
What's your sample to say what "oh environmentalists" are concerned with? Consider Portland, OR, where environmentalists put in zoning to pack housing into the center of town and prohibit it from sprawling farther out. (True, the anti-environmentalists lately threw a wrench into that with a misleading statewide referendum.) Or on the other side of the country, environmentalists in Vermont are also encouraging more housing in and close to traditional town centers rather than sprawling across the countryside. What is your sample set of "environmentalists" who prefer that we'd all live in suburbs in giant houses? I'd suggest that whoever you can find fitting that description just flies a flag of convenience - the evil often cloak themselves in the names of the good.
"with their freedom lost all virtue lose" - Milton
I think he means there is a difference between understanding it's a waste when the heat you are paying for is going out the window, there is a very direct cost. It's less likely for people to think that the heat coming out of the back of their vacuum cleaner is also wasted energy. Electrical appliances get hot when they run, right? Nothing unusual about that.
We hope your rules and wisdom choke you / Now we are one in everlasting peace
I haven't seen anyone point out the efficency of an carnot engine (car, your fridge, etc) depends on the output end being hot (the temperature difference).
If you cool the radiator to gain energy using this device, then you'll decrease the efficiency of the primary device.
e.g. if you connect this to the radiator at the back of your fridge, then your fridge will be less efficient.
I don't know whether the net gain is positive or negative though.
...is that our buddy Roland Piquepaille finally posted a story that directly summarizes and links to the information instead of telling us to come to his blog for the real story.
Remember, there were no nuclear weapons before women were allowed to vote.