BMW Trialing New Heat Energy Management Technologies

BMW Project Heat insulation on the engine
BMW Project Heat insulation on the engine

Hot stuff

BMW has given us a sneak peek at several new heat-related technologies, which aim to reduce emissions and improve fuel efficiency.

The first system under development could virtually eliminate cold starts by fully encapsulating the engine with materials typically used to insulate a vehicle's underfloor. This allows a warm engine to "cool down much more slowly after being switched off and still has a temperature of approximately 40 degrees Celsius after 12 hours. Each degree Celsius above the ambient temperature reduces fuel consumption by 0.2%."

The second system is literally from the space age, albeit the 1960s. Using an electricity-generating principle similar to the one used on vintage space probes, BMW is working on integrating a thermoelectric generator (TEG) into the exhaust gas recirculation (EGR) cooler. The generator would use "the effect of the temperature gradient in thermoelectric semi-conductor elements generating electrical voltage (the Seebeck Effect). The bigger the difference in temperature, the higher the voltage generated." While interesting and boring at the same time, the system would reduce fuel consumption and CO2 emissions by up to 2%.

The final system, dubbed the exhaust gas heat exchanger, would warm the drivetrain to reduce friction in components such as the gearbox. It would work by conveying heat from the exhaust to the oil in the automatic transmission. In a similar fashion, BMW is also considering a system that uses a heat exchanger to power the electric heater that is equipped on many diesel-powered vehicles.

Ok, sounds good, but why does all this techno-wizardry matter? According to BMW, "Even a highly efficient engine can only convert about one-third of the energy contained in fuel to actually propel a car. Two-thirds is lost as waste heat via the car's exhaust and radiator."

Most of the systems are currently in a prototype stage, so it'll likely be several years before we can expect to see them on production vehicles. Regardless, BMW says their engineers are carefully considering which objectives can be best reached with available technology.

Source: BMW

BMW Engineers Trial Hot New Technologies

For years, engineers have avoided heat in cars to protect components from overheating.

Now, this goal is being turned on its head as car makers attempt to harness previously wasted energy for practical purposes such as improving fuel consumption and reducing CO2 emissions.

Even a highly efficient engine can only convert about one-third of the energy contained in fuel to actually propel a car. Two-thirds is lost as waste heat via the car's exhaust and radiator.

Engineers at BMW are currently working on a number of promising projects that make use of heat normally lost. The first idea may banish cold starts forever to reduce emissions. The second approach can convert the heat from a car's exhaust into electricity, using a similar principle to space probes of the 1960s. The third idea uses waste heat to heat the interior of a car.

"We want cars to warm up as quickly as possible, since higher temperatures mean less friction, less friction means less fuel consumption and, therefore, less CO2," says Dr Andreas Eder, Head of Heat Management Pre-Development Projects at BMW Group.

No more cold starts

BMW engineers are working all-out on largely avoiding cold start conditions by fully encapsulating engines. Improved heat insulation of engines would prevent them from cooling down quickly and retain as much residual heat as possible for the next start.

In addition to the air flaps already on some production its production models, a BMW prototype already developed is completely surrounded by fully clad walls and panels using proven materials that are normally used in the car's underfloor for insulation.

Since the cooling system on new cars is so effective, there is no risk of overheating. Instead, components in the engine compartment which previously had to be cooled at a great effort are now protected better from engine heat.

Thanks to this approach, the engine cools down much more slowly after being switched off and still has a temperature of approximately 40 degrees Celsius after 12 hours. Each degree Celsius above the ambient temperature reduces fuel consumption by 0.2 per cent.

A by product is that materials previously used to dampen noise in the engine compartment are no longer required. Apart from saving fuel, the second customer benefit is a quicker warm up of the interior, which would be appreciated by customers when it is cold outside.

Electric power from waste heat

Another option for reducing CO2 and fuel consumption - by up to two per cent - is a system which generates electricity from the heat of exhaust gases.

Since presenting the principle of a thermoelectric generator last year, the company is now presenting the next level of development in the form of an integrated component in the exhaust gas recirculation cooler. With the latest development, up to 250 W of energy are produced under typical driving conditions - equal to about half the on-board electricity consumption in a BMW 5 Series.

Between three and eight per cent of the total fuel consumed by modern cars is due to the rising number of electricity-dependent features. To provide this energy without additional consumption, BMW engineers have adapted the idea which first powered space probes in the 1960s.

The thermoelectric generator uses the effect of the temperature gradient in thermoelectric semi-conductor elements generating electrical voltage (the Seebeck Effect). The bigger the difference in temperature, the higher the voltage generated. Exhaust gas temperatures, which are usually between 300 and 900 degrees Celsius, are on the hot side of the generator, and engine coolant is used for the cold side.

Whilst still a prototype, the current solution gives engineers more information on the operating principles as well as obstacles yet to be overcome. This know-how may then be applied in implementing an underfloor solution.

Heating with waste heat

BMW engineers are also working on an exhaust gas heat exchanger. With petrol engines, it would be very effective in warming up the drivetrain more quickly to the right temperature, avoiding friction in, say, the gearbox. Such an exchanger conveys heat, or thermal energy, from one flow to another, in this case the heat of the exhaust gas to the oil in the automatic transmission, with additional heat being pumped in consistently from the start

Diesel engines are now so efficient that the excess heat generated by the engine is usually insufficient to heat the interior of the car alone. It has become quite normal to fit cars with an additional electric heater, which can add up to 1 litre per 100 kilometres. To avoid this extra fuel consumption, hot exhaust emissions may be used by means of a heat exchanger close to the catalytic converter to provide an additional source of heat for the interior. Such a system may avoid the need for electrical heating modules which consume additional fuel.

Given that not every technology is equally sensible for each type of engine, BMW engineers carefully consider which objective can be reached best with which technology and in which context such as size and power of the engine and the car's main use.


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Comments (24)

trekkerbin trekkerbin
How to combine all these fuel saving technologies into actual production without sacrificing the driving pleasure, maintenance complexity...etc are quite challenging. But gp for it, BMW! You have my full support.
Oct 21st, 2009 3:42pm
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carbonsigma carbonsigma
So what happens when the engine gets too hot?
Oct 21st, 2009 2:22pm
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scratchy996 scratchy996
it doesn't because heat gets converted to electricity.
Oct 22nd, 2009 12:45am
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carbonsigma carbonsigma
Aha, good one.
Oct 22nd, 2009 7:50am
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Lennox.... Lennox....
This is why BMW is BMW they go outside the box! the insulator idea pretty nifty! i believe there gonna come out with with the insulator and the thermoelectric generator but i love there ideas really Long Live BMW!
Oct 21st, 2009 1:21pm
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rxlonline rxlonline
big deal :p, The new Prius already have a system with this purpose: reduce emissions. it keep exaust temperature warm longer after a ride , so at the restart the nocive gases that apear higher at low temps dosent't get out in greater number than ate low temps.
Oct 21st, 2009 9:34am
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Edison Edison
As far as I know, the Prius doesn't convert heat energy to electricity...
Oct 21st, 2009 1:29pm
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CDspeed CDspeed
I guess this is how the future will play out. We'll use less and less gas until it's replaced all together. I vote for electric cars, the fuel is not flammable and chargers can be installed as easily as a light fixture. Although I'm sure there will be quite a few people that will stick their hands in the portion of their electric drivetrain marked DO NOT TOUCH receiving the jolt of their lives.
Oct 21st, 2009 7:44am
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scratchy996 scratchy996
"integrating a thermoelectric generator (TEG) into the exhaust gas recirculation (EGR) cooler" - for some reason i got aroused by that phrase...yes, i am an engineer.
Oct 21st, 2009 5:50am
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eeoikari eeoikari
For sure there's some way to regulate the engine temperature after the engine has warmed up - I'm sure BMW have thought about that. Hopefully these will find their way to production. These would be appericiated in the cold temperature, especially the drivetrain heating and engine insulation.
Oct 21st, 2009 3:57am
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mn07 mn07
Won't this all cause a cooling problem after the engines warmed up?
Oct 21st, 2009 3:48am
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NewGit NewGit
They're going to have to tread a fine line in using insulation, too much and they'll need more cooling, don't forget temperature differences between countries. I'd propose looking at storing the heat in a special liquid (see ionic liquids) that are then kept in circulation using something like a Sterling engine attached to the main motor.
Oct 21st, 2009 3:02am
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termigni termigni
public relations stunt
Oct 21st, 2009 3:00am
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pole_mccoy pole_mccoy
Who said the internal combustion engine is dead? Long live to combustion :)
Oct 21st, 2009 2:59am
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Prince_Ash Prince_Ash
I tip my hat off to BMW, always discovering new ways to improve things.
Oct 21st, 2009 2:42am
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orlandocroccia orlandocroccia
that's why i like BMW . . . they explore fields that we don't see other brands exploring.
Oct 21st, 2009 2:35am
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jerry05cod4 jerry05cod4
agreed... they are leaders in innovation no doubt
Oct 21st, 2009 2:43am
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ispano6 ispano6
This is nothing new. BMW and Honda have been researching these approaches since 2006, and the idea of converting waste heat into usable energy has existed since 1914. Honda had also been working on a hybridized STREAM project(since 2006) that converts waste exhaust heat into electric power using the Rankine cycle(converting heat into work). Honda presented the overview and results of the project in 2008 to the SAE Hybrid Vehicle Technology Symposium. While innovative, these systems simply try to make use of otherwise wasted energy to power auxiliary systems.
Oct 22nd, 2009 4:01am
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tejasruke tejasruke
i hope it comes into production soon...
Oct 21st, 2009 2:20am
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sub39h sub39h
a lot of this tech is very very clever. would be interesting to see it's effect on production models
Oct 21st, 2009 2:12am
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astroturf777 astroturf777
yeah - but you'll pay a huge premium for the 'exciting' technology - to save 2% at the pump?? want to make the same difference? stop carting rubbish around. use a spacesaver tyre, dont take passengers, rip out the back seats, replace your electric powered, heated, cooled, vibrating massage seats with side, back and buttock air bags from the front and install carbon momos instead... my australian made family car from 1997 has a 3.6 v6 engine, carries 5 and weighs less than 1300kg - end result is real world fuel figures of less than 9 l/100km - with 260,000km on the clock... all this wonderful safety technology, engine revisions etc just make cars heavy - if a car is 25% fatter, you need 25% more power to push it... the 2009 model of my car is over 350kg heavier
Oct 21st, 2009 3:00pm
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sub39h sub39h
i don't think there's anything wrong with having your cake and eating it. i want big tyres - it improves handling. i want my family to have airbags in every possible location. i have friends - i want to take them places. and i have a spine - i want to keep it, so no momos. BMW allows you to have luxury and performance and convenience, but allows you to replain environmentally conscious at the same time. no doubt they'll charge a premium for it, but the tech is bound to trickle into more mainstream cars and from there it will become the norm
Oct 22nd, 2009 7:16am
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fusion01 fusion01
'but you'll pay a huge premium for the 'exciting' technology - to save 2% at the pump??'. Hardly, they'll only be implemented if cost-effective I'd presume. The 2% also only relates to the TEG and not all technologies implemented together.
Oct 26th, 2009 1:24am
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