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Thermal Activated Cooling System  (Source: Oregon State University)
Device may eventually be used on a car exhaust for cooling and power

Today, about half the energy produced by cars, factories, and power plants is wasted as heat that escapes into the atmosphere.

Engineers from Oregon State University have made a major step towards addressing one of the most common wastes of energy today by recapturing some of the heat generated by a motor and using that energy to produce power. The engineers have successfully completed a prototype machine that can be attached to the exhaust pipe of automobiles, diesel generators, factory, and utility machinery that produces waste heat. The prototype system is being perfected at the university right now.

"This could become a very important new energy source and way to improve energy efficiency," said Hailei Wang, a research associate in the School of Mechanical, Industrial and Manufacturing Engineering at OSU. "The prototype shows that these systems work as well as we expected they would."

The researcher says that over half the heat generated by industrial activities is currently wasted. Even the most efficient plants according to Wang only convert about 40% of the energy produced into electricity. Combustion engines inside vehicles are even less efficient converting only 25-40% of the energy they produce.

The system that the team in Oregon has produced is called the thermally activated cooling system. The system is able to combine a vapor compression cycle with an organic Rankine cycle, which is an existing conversion technology. Using the prototype, the team at the university was able to turn 80% of every kilowatt of waste heat into a kilowatt of cooling capability. However, the efficiency wouldn't be as high at about 15-20% efficiency if the goal was to produce electricity.

"This technology would be especially useful if there's a need to have cooling systems where heat is being wasted," Wang said. "That's one reason the research has been supported by the Department of Defense, because they see it being used to provide needed air conditioning for electronics and other purposes when they are using generators in the field."

The team is looking at the system to power air conditioning systems in a hybrid auto and recharge the batteries at the same time. German scientists have previously developed a system that is able to generate power from wasted heat that can be turned into electricity. Researchers at the ORNL have also worked on a system that captures the water that is in the exhaust from diesel engines to provide drinking water for soldiers in the field.

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Would be good if this works
By FITCamaro on 6/14/2011 12:43:47 PM , Rating: 1
Would at least make systems a little more feasible. Or maybe replace alternators. Just need to it to be light enough.

RE: Would be good if this works
By nafhan on 6/14/2011 1:01:08 PM , Rating: 3
Don't forget cost and size. Those need to be reasonable as well.

RE: Would be good if this works
By mdk77777 on 6/14/2011 1:27:13 PM , Rating: 3
Yeah, you have a natural gas generator using $500 per month of energy. How much are you going to spend to recapture 10% of waste heat? $600 per year is the break even right? Take you awhile to pay off even a $10,000 investment. Technology is seldom the bottle neck. Economics are the stumbling block.

RE: Would be good if this works
By dsx724 on 6/14/2011 1:56:14 PM , Rating: 1
The technology doesn't even make sense. In order to capture the heat, they need to increase the surface area exposed to the heat which increases the restriction on the exhaust and in turn causes the engine to be less efficient to begin with. Its the same concept with turbochargers except this is far from practical because of its weight.

RE: Would be good if this works
By Natch on 6/15/2011 10:54:59 AM , Rating: 4
If it needs a large surface area to be efficient, maybe we could have one built over top of Washington DC.....which could, with all the hot air coming from Congress, effectively power the entire country! ;)

By superstition on 6/17/2011 6:09:05 PM , Rating: 2
Along with talk radio broadcast booths.

RE: Would be good if this works
By zixin on 6/14/2011 3:50:32 PM , Rating: 2
The device captures 80% of waste heat as a cooling source. Besides, all energy investments take time to recoup be it a hybrid car or solar pannel on your roof.

RE: Would be good if this works
By ViroMan on 6/14/2011 1:27:15 PM , Rating: 3
you forget this one...

However, the efficiency wouldn't be as high at about 15-20% efficiency if the goal was to produce electricity.

I don't know how much gas/energy is used to run a car but, I don't think recapturing 15% of its wasted energy is very much.

RE: Would be good if this works
By Samus on 6/14/2011 2:00:18 PM , Rating: 2
Absolutely. I'm surprised it's efficiency is so low...15%? I mean something is better than nothing, but honestly, this shouldn't be marketable until its at least near 50%.

RE: Would be good if this works
By Souka on 6/14/2011 7:06:59 PM , Rating: 2
I have a wind powered generator on the roof of my car.
As I drive it captures the energy of the wind and powers my car's electrics.

(In the voice of Homer)
I'm soo smart! S M R T , I mean S M A R T...

RE: Would be good if this works
By blackened160 on 6/14/2011 8:35:55 PM , Rating: 1
First law of thermodynamics would say otherwise.

RE: Would be good if this works
By Siki on 6/14/2011 11:04:44 PM , Rating: 1
Oh, no shit?

RE: Would be good if this works
By Alexvrb on 6/14/2011 11:43:56 PM , Rating: 1
Blackened, you and whoever downrated Souka missed the fact that he was being sarcastic. To me, it was pretty obvious - especially with the Homer reference.

It just isn't that efficient as a generator, not at 15-20%. If they can make it light, small, and reliable (like a modern turbo) then we'll see.

By JKflipflop98 on 6/15/2011 4:42:23 AM , Rating: 2
Lisa! Get in here. In this house, we follow the laws of thermodynamics!

By delphinus100 on 6/14/2011 7:16:50 PM , Rating: 2
Two words: Incandescent Bulb.

RE: Would be good if this works
By AnnihilatorX on 6/15/2011 5:24:20 AM , Rating: 2
Absolutely. I'm surprised it's efficiency is so low...15%? I mean something is better than nothing, but honestly, this shouldn't be marketable until its at least near 50%.

You need to read up on the law of thermal dynamics
Absolute maximum efficiency = 1-Tout/Tin
where Tout and Tin denote temperature of sink and source in Kelvins respectively, for a device which converts thermal energy to other form of energy (heat engine).

If exhaust temperature is 60 degrees Celsius (333K), outside temperature is 22 degrees Celsius (295K), the maximum efficiency for any energy conversion system, regardless of sophistication is 1-295/333 = 11.5%
So that's about 15% depending on what they take as temperatures.

You can achieve better on a cooling system however, since that's not strictly an energy conversion system.

RE: Would be good if this works
By FishTankX on 6/15/2011 8:21:28 AM , Rating: 2
Exhaust temperatures if I'm not misinformed actually exhaust at arouund 200C. Maybe much higher.

This article ( says around 700 degrees. That's PLENTY of difference to work with to get 15% energy out of the system.

RE: Would be good if this works
By AnnihilatorX on 6/16/2011 3:32:37 AM , Rating: 2
Well you also need to consider a efficient heat pathway from your heat source to environment, along with inevitable efficiency loss during conversion. The thermal efficiency law I quoted is theoretical maximum, real device may get 40% out of that.

So if we take 200deg C, That gives about 40% theoretical max.
Then you are lucky if your energy converter itself achieve 50% of that. That gives 20% efficiency overall.

By AnnihilatorX on 6/16/2011 3:38:06 AM , Rating: 2
As for the 700 deg C, it must be a big truck! After reading the article, I believe that it says the exhaust pipe can reach 700 deg C, but if you start extracting energy from it, my guess is that it won't sustain the temperature. 200 is a better guess.

RE: Would be good if this works
By FishTankX on 6/14/2011 6:32:43 PM , Rating: 2
You might be surprised. About 30% of all heat created by combustion in a car is exhausted. This is roughly equal to the power used to move the vehicle. If you use this in a hybrid situation, it would stand to logic that if the proportions of exhaust heat energy and captured energy (by the engine) are equal, than using this recovery system to feed back into the battery would end up in an increase in fuel economy of about 15%. For example, on a prius this might boost city mileage from 58 to 64. This isn't an inconsequential boost over the life of the vehicle.

If you take your average SUV which is probably burning $2500 worth of gas a year, and slash that by 15% over the life of the vehicle, you'd probably 'recover' around $6000 over a 15 year life of the vehicle. $8000 if it was 20%.

Note: This assumes that the system lasts for the life of the vehicle, and it's a hybrid SUV.

Basically any hybrid system could stand to gain 15%-20% in fuel economy if it's fuel economy was low enough that you could recover enough dollars worth of motive power to recoup the cost of the system.

Another critical part of this tech is, if it CAN actually do give that much of an increase, it'll be a vital tool to increase fuel economy to meet CAFE regulations. Mostly at the bottom end i'm guessing. A technology that could boost fuel economy 15-20% doesn't come along very often.

RE: Would be good if this works
By AnnihilatorX on 6/15/2011 5:17:14 AM , Rating: 2
I think you misunderstood. If the goal is to reuse waste heat to generate electricity, the efficiency is 15% of the wasted energy. That means if 40% of initial fuel of the automobile is wasted heat, such recovery system will only recover 15% of 40% = 6% recovered energy.

I do not think they can get much better than that. The evil law of thermal dynamics makes it a vicious circle of diminishing returns if you compound thermal based energy systems since the temperature gradient decays rapidly, it's not even a linear decay.

RE: Would be good if this works
By FishTankX on 6/15/2011 8:24:59 AM , Rating: 2
However, Annihilator X, I think you misunderstood my numbers.

Let's say the engine converts 30% of the energy in gasoline into useful motion.

10KWH of gasoline would result in 3.5KWH of motive power. Let's say 4KWH is exhausted as waste heat.

If you recover 15% of that waste heat, that turns out to be 600WH.

If you add that 600WH of energy back into the 3.5KWH of motive power, you get 4.1KWH

4.1KWH is 15% higher than the original 3.5KWH of motive power generated by the engine. THUS motive power is increased by 15%, and so is fuel economy because you got 4.1KWH of motive power out of the engine systems rather than 3.5

Do you see why i'm saying that you can boost fuel economy by 15% with this system?

RE: Would be good if this works
By FishTankX on 6/15/2011 8:26:35 AM , Rating: 2
Oops, that should be 3KWH of motive power, increased to 3.6KWH of motive power by exhaust recovery.

RE: Would be good if this works
By mars2k on 6/15/2011 11:25:28 AM , Rating: 2
Capturing this downstream heat could be a huge boost for co-generation efforts. Imagine any large building, a hi rise office building, a mall, a sports arena anything of any size that requires air conditioning and electric power. How many Walmarts are there out there?
Hook up a natural gas source a few generators (maybe fuel cells) and some of these systems along with good management software to balance output and you’d have something major.
How does this compare with standard absorption cooling systems? Is this more or less efficient?

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