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A Flexible Way To Convert Waste Heat To Electricity (asianscientist.com)
A research group in Japan has developed an inexpensive, large-scale and flexible thermoelectric generator (FlexTEG) that has high mechanical reliability and can convert heat into electricity efficiently. The findings are published in the journal Advanced Materials Technologies.
From a report: Thermoelectric conversion is one of the most attractive techniques for converting low-temperature (150C or lower) waste heat into electric power. However, widespread adoption of this technology has been hampered by a lack of suitable packaging techniques for thermoelectric generation modules that can operate in the 100-150C range. In addition, the production cost of modules for generating power at room temperature was prohibitive.
In the present study, scientists at Osaka University, Japan, have developed a method to manufacture thermoelectric generation modules in a cost-efficient manner while preserving the conversion efficiency of the modules. They mounted small thermoelectric semiconductor chips on a flexible substrate and were able to achieve reliable and stable adhesion of the electrical contacts between the chips and the flexible substrate. They called their invention FlexTEG.
In the present study, scientists at Osaka University, Japan, have developed a method to manufacture thermoelectric generation modules in a cost-efficient manner while preserving the conversion efficiency of the modules. They mounted small thermoelectric semiconductor chips on a flexible substrate and were able to achieve reliable and stable adhesion of the electrical contacts between the chips and the flexible substrate. They called their invention FlexTEG.
The industries I can see adopting this quickly:
Automotive industry: There is a continuing push to improve overall mileage of a car. If waste heat can be captured as electrical power, It will get adopted.
Power industry: These guys are already trying to up their efficiency and the competition is stiff. If the power industry can implement this it will get implemented real fast.
Industrial processes: These guys vent so much waste heat it isn't funny. But they do have space normally. I can see them intentionally re-tuning their discharge temperatures to take advantage of this. Many of these industries are (also) very competitive. If they can shave a couple tenths of a percent of their costs, they will do it.
I expect most people in the industries I mentioned will not immediately notice it. But one of those industries will see it and get it implemented. And then Ford or Chevy or Subaru will come out with a car that doesn't have an alternator in it. All of the electrical power is generated from a rebuilt radiator and exhaust system that recycles the power from the heat. A lot of alternators on a car can draw 1-2 hp. So that is now either top end power or additional MPG. Either way everyone else in the industry is now saying "how do we do that?"
I expect the same thing to occur in industrial process, only the average consumer will never hear of it. In metal refining their price per ton will drop by a penny or two consistently and everyone else will start asking how they managed to shave that much cost off without reducing anymore many power.
In either case, once this gets adopted in a particular industry, everyone in that industry will stampede to adopt it so they can stay competitive.
Architectural plans are like computer source code with a couple of differences: You only compile once.
> A lot of alternators on a car can draw 1-2 hp. So that is now either top end power or additional MPG.
You're correct there. The alternator needs to be able to produce about 1 HP of electricity. At 1.8% conversion efficiency, a TEG would need 56 horsepower (42,000 watts) of heat in order to generate enough electricity, in the lab. Do you think your engine wastes 56 HP as tailpipe heat while cruising around? Even at full throttle?
The car uses about 20 HP to maintain cruising speed. Is it wasting three times that amount as heat? Probably not. Let's say it's wasting 5 HP as tailpipe heat.
Obviously blowing the exhaust through "radiator" (heat exchanger) isn't going to make the exhaust cold. It'll be out almost as hot as it went in. Perhaps we can recover 1HP, on a brand new vehicle in the lab. We need 56HP, we only got 1HP. Oops.
Now go look in your tailpipe. See the soot? Notice all the rust and everything on the bottom of the car after a few years of driving? That'll probably cut efficiency in had again, so we end up getting about 1% of the power we need.
Thanks though.
Another way, perhaps simpler than the math and making assumptions about waste heat, is to try this simple experiment:
Walk by your tailpipe with the car running. Does it feel like a 42,000 watt heater to you? In other words, did you get cooked when you walked by?
why would you try to sequester waist heat at the coolest part of the exhaust system on a ICE vehicle?
the exhaust manifold even at idle can reach hundreds of degrees F. Go down the pipe a little further and you have a heat mill called a catalytic converter
The average light off temperature at which the catalytic converter begins to function ranges from 400 to 600 degrees F. The normal operating temperature can range up to 1,200 to 1,600 degrees F. But as the amount of pollutants in the exhaust go up, so does the converter's operating temperature.
Seems to me to a pretty good place to put some of these to me.
1600F would be about 3033 kelvin/watt [K/W].
the exhaust manifold usually in the 700 to 1000 degree range depending on the load on the engine.
now you have another 1895 kelvin/watt [K/W]
so that's almost 5 K/W of wast heat that can be tapped for free.
just saying that you're just looking at the wrong places to look.
Too bad their efficiency sucks. I've worked a lot with them, they've gotten quite cheap in the last few years. The first one I bought to experiment with was $22. Now you can get ten for about that. You can thank the public for dropping the price on them with their demand for those 12v portable coolers that plug into cigarette lighters.
What a lot of people didn't realize though is the little buggers draw about 2 amps of power (at 12vdc) to create a ~ 30 degree temperature gradient. Which isn't really that much, and it generates 25 watts of heat (plus whatever heat it's moved out of the cooler) on the external heat sink, so it really tends to warm up its surroundings.
Only VERY recently have I seen much in the way of reverse-use. You can buy cell phone chargers now that you sit by the campfire when you're out on a camping trip, to charge your cel phone with the power of the camp fire. Not all that efficient, but in that setting, efficiency isn't important, as you're sitting next to a stupidly large wasted heat source (where cooling isn't an issue) anyway.
I'd like to see this tech evolve more than finding new packaging for old technology. They need to find something besides the peltier. Efficient waste heat energy recovery and universal material recyclers are the TWO technologies that can change the world in the way the transistor did. So I'm not sure if I'm happy or sad to see this - yes it's better than what we've got now, but you're just rehashing old tech rather than finding better tech. This is the "acorn tube / nuvistor" of its time. We don't need better tubes, we need something better than tubes.
I work for the Department of Redundancy Department.