DailyTech - New Coolant Could Help Improve Driving Range of Electric Cars

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Auto New Coolant Could Help Improve Driving Range of Electric Cars
Shane McGlaun (Blog) - July 12, 2012 11:29 AM

23 comment(s) - last by Dr. Kenneth No.. on Jul 21 at 11:01 AM

Paraffin laced battery coolant, not tasty frosting (Source: Fraunhofer-Gesellschaft)

New EV coolant uses paraffin to increase battery life

One of the things that can have a significant impact on the battery performance of electric vehicle is the temperature of the environment. Electric vehicles generally have a shorter driving range in a warm climate (think Texas summers) than it would in more temperate areas such as California due to effects of heat on the battery cells.

However, a group of scientists in Germany has developed a new coolant for electric vehicles that promises improved cooling performance.

Most vehicle battery packs are currently cooled by standard antifreeze and water, just as a gas engine would be cooled. The new coolant the German researchers have developed is a dispersion that mixes water and paraffin along with stabilizing surfactants and glycol. The developers say that the new coolant functions better than existing air or water-cooling methods for batteries.

"With the melting and solidifying of the paraffin, great amounts of heat will be absorbed and emitted," explains developer Tobias Kappels of the Fraunhofer Institute for Environmental, Safety and Energy Technology in Oberhausen, Germany. "The heat capacity of the fluid is twice to triple as high as the heat capacity of water in a temperature interval of 10°C."

The coolant uses a principle called latent heat. As the battery packs heat up, the solid paraffin particles and the coolant melt, absorbing heat from the battery pack in the process. As the coolant cools, the paraffin droplets resolidify allowing the process to begin again the next time the battery heats up.

Keeping the battery packs cool can have a huge impact on how well the battery pack inside an electric vehicle performs. A German battery researcher from RWTH Aaachen University in Germany named Dirk Uwe Sauer says, "A 10°C temperature increase can reduce the battery lifetime by a factor of two."

If this coolant turned out to be stable and works as promised, it could have significant implications for electric vehicles on the current market such as the Nissan Leaf, Tesla offerings, and the Chevrolet Volt.

Source: RSC.org

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So...

By Motoman on 7/12/2012 12:02:12 PM , Rating: 3

...why would we not use it for ICE engines and other cooling applications too? Does it require specialized radiators or anything?

RE: So...

By Colin1497 on 7/12/2012 12:20:42 PM , Rating: 2

My guess is the temperatures. Paraffin probably has issues with the high local temps and isn't chemically stable in the environment. Again, just a guess.

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RE: So...

By Samus on 7/12/2012 12:47:59 PM , Rating: 5

Internal combustion engines ideally operate at a block temperature around 200f, depending on materials, performance and design specifications. Since this temperature extreme doesn't exist anywhere people live and drive (unless your James May driving into a volcano) advanced coolant isn't important. Current coolant solutions absorbe heat almost as effectively as water, while preventing metalix oxidation, lubricating the water pump, and providing freeze protection and boil-over protection better than water. Basically we don't need any improvement on cooling ICE's. The the introdution of ethelyn glycol and electronic cooling fans, we've had adequate ICE cooling solutions since the 70's.

The problem with electric vehicles is we're using the same cooling solutions we use on ICE's to cool them, when it's an entirely different beat. The ideal operating temperature is much lower and requires much less fluctuation.

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RE: So...

By Souka on 7/12/2012 2:43:32 PM , Rating: 2

and viscosity is an issue.

From the picutre, there's no way a ICE water pump could handle this stuff.

Also, oxidation is probably not an issue for cooling packs.

One thing this article is missing, is how currrent battery packs are actually cooled (diagram) and how this stuff would be used.

Just a few thoughts.

Also... you can leave coolant untouced in a car for years...10+.... and car will run. (yes this is a really bad idea, but people do this often).

With this parafin coolant....how often does it need to be replaced?

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RE: So...

By Samus on 7/12/2012 11:43:05 PM , Rating: 1

I'm also curious what environmental impact parafin has when it isn't recycled properly because we all know every backyard mechanic dumps coolant down the drain.

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RE: So...

By othercents on 7/13/2012 8:46:40 AM , Rating: 2

From the article it sounds like the stuff becomes a solid then liquifies when heated. Because of this you would probably place the stuff into static chambers. They probably would also still use the normal antifreeze/water combination to pull the heat from the system for even more cooling effect.

Probably the best way to use this stuff would be to build it into the battery packs and add parafin recycling into the process of recycling the battery pack.

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RE: So...

By Kurz on 7/12/2012 12:26:13 PM , Rating: 1

I have a feeling it won't withstand the high temperatures of an engine. Water has some of the highest high capacity of any naturally occuring substance, plus its easier to maintain a stable high temperature with water that isn't going through any sort of phase changing.

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RE: So...

By bobsmith1492 on 7/12/2012 12:42:36 PM , Rating: 1

Water can do the same thing as this but at a different temperature. The key is the temperature of the phase change of the material since a phase change absorbs lots of thermal energy.

In an engine, water can vaporize to steam locally (at hot spots) and absorb high amounts of energy, just like the parafin in this compound. It can re-condense back at the radiator. I don't think this actually happens much, though, because if the water vaporized it would increase the pressure, forcing it to stay liquid.

Parafin simply melts (changes phase) at an appropriate temperature such that it can solidify at the radiator and melt at the hot spot (electronics).

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RE: So...

By Iketh on 7/12/2012 1:32:10 PM , Rating: 3

Pressure increases by only a few lbs. The radiator cap will prevent build-up beyond ~5-15 lbs by releasing excess into the reservoir.

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RE: So...

By FITCamaro on 7/12/2012 1:40:17 PM , Rating: 2

Probably because the coolant looks far to thick to be circulated through engines.

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What after it is melted

By ax on 7/12/2012 12:09:41 PM , Rating: 2

So, after few minutes it is melted and then what? Amount of heat it can absorb is not infinite. Heat needs to be transferred out like with any other coolant. Will this thing need more energy for pump to circulate because is thicker?

RE: What after it is melted

By Motoman on 7/12/2012 12:15:30 PM , Rating: 2

That's kind of my question - I'm guessing it needs specialized radiators to account for the higher viscosity and the re-solidifying of the paraffin particles.

The paraffin particles make the fluid overall able to absorb a lot more heat due to it's phase change - but it needs to be able to shed that heat and re-solidify to complete the process.

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RE: What after it is melted

By Colin1497 on 7/12/2012 12:17:18 PM , Rating: 2

No, it obviously re-solidifies in the radiator. They have figured out how it can re-solidify in a radiator and stay in suspension rather than just cake up in the radiator. That's the key. This is a phase change cooling loop just like a vapor cycle loop is. The difference is that the phase change is solid/liquid instead of liquid/gas.

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RE: What after it is melted

By FaaR on 7/12/2012 1:00:17 PM , Rating: 3

That would be the surfactants' job, keeping the paraffin in solution in both liquid and solid states. One question remains as to longevity, as over time larger blobs might still form, like in the pump for instance, but I would think the scientists/developers behind this project have all thought of that already and taken neccessary steps to prevent any gradual build-up...

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Who's hot?

By bh192012 on 7/12/2012 1:16:10 PM , Rating: 2

Is it really hotter in Texas than California? I'm asking as someone from the central valley of California, where today it's going to be around 104.

RE: Who's hot?

By fic2 on 7/12/2012 4:13:59 PM , Rating: 2

Last year Dallas had 71 days over 100.

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RE: Who's hot?

By Dr. Kenneth Noisewater on 7/21/2012 11:01:29 AM , Rating: 2

Yes. 100F days are pretty typical all summer, and that's measured at weather stations, not on black asphalt. It's hotter still in Arizona.

Glad my Volt has active liquid thermal management, which will come on automatically when needed.

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This is Old Tech

By Guimar on 7/12/2012 2:13:11 PM , Rating: 2

The Lunar Rover used state change wax cooling in the 1970's.

RE: This is Old Tech

By johnsmith9875 on 7/12/2012 4:57:36 PM , Rating: 2

Makes sense, you can't air cool anything on the moon.

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Who needs batteries anyway

By AntiM on 7/12/2012 4:53:15 PM , Rating: 2

I keep hoping someone will invent a method for converting the energy in gasoline directly into electricity, eliminating the need for batteries. Surely it's possible. Just think how much more efficient an electric motor is than an ICE.

RE: Who needs batteries anyway

By johnsmith9875 on 7/12/2012 4:58:39 PM , Rating: 2

Well you can, with fuel cells. The problem is fuel cells are horribly expensive and most likely will never become cheap unless a 2nd Roswell crash happens.

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