Researchers to improve fuel efficiency by harnessing exhaust heat

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By Tim Beissmann | November 25th, 2010

A group of US researchers is about to start work on a system that uses heat from a vehicle’s exhaust to generate electricity and reduce fuel consumption.

The engineering team from Indiana’s Purdue University was granted $US1.4 million ($1.42 million) over three years by the US Department of Energy and the National Science Foundation to develop a prototype of the system, which will use thermoelectric generator (TEG) technology.

Purdue professor of mechanical engineering and electrical and computer engineering, Xianfan Xu, is leading the research and development, which will be conducted in collaboration with General Motors.

The concept is an advanced one, but one with great potential for increasing the efficiency of internal combustion engines.

The TEGs will be inserted into the exhaust system behind the catalytic converter, where temperatures reach up to 700 degrees Celsius. They generate electricity when there is a temperature difference between one face and the other. Therefore, the goal is to develop materials that are poor heat conductors and will not allow the rapid transfer of heat.

Currently, TEG technology is not capable of withstanding such excessive temperatures. The researchers are looking to use a combination of rare-earth elements – including erbium, neodymium, cesium and lanthanum – and skutterudite, as well as developing less-expensive alloys known as “mischmetals”.

Mr Xu said the goal for the first prototype was to improve fuel efficiency by five percent, and said future systems operating at higher temperatures could potentially lead to efficiency gains of up to 10 percent. He said optimisation of heat capturing was the key.

The potential of the system is clearly far wider reaching than just cars, and if successful, could also contribute to improving the efficiency of other sources that create waste heat, such as homes and power plants.

The project will begin on January 1, 2011.

davie

The advancements in engine efficiency in the last 10 or so years really are impressive. It seems that technology really is the future, even if we can’t actually fix our cars ourself anymore.

in the early 90′s steel block carby pushrod engines were still around in numbers, now they are history.

things I can think of which have made a difference:
multi valve engines
EFI
direct injection
dry clutch DSG’s
6 speed transmissions
hybrids
common rail diesel
multi air
regenerative brakes

Al Juraj

Add the start-stop technology to your list. Cylinder shut-off, in theory, saves fuel, but it only works on a highway cruise. And cars like the Accord V6 and Commodore AFM, which use this technology, are still beaten by their rivals on efficiency.

Shak

So its going to use the energy created from the TEG to operate like a mild hybrid. Im assuming it would like a hybrid be most efficient in stop start traffic as you would be producing much hotter exhaust just by standing there.

J

Peltier Effect – so long as there’s a diff in temp, you get current flow. Could be sufficient energy to replace the alternator if done right.

Chucky

I think the fact that you need rare earth minerals to create an efficiency gain of 10% will be their downfall.

Shak

They did say the company is working on smelting some type of pseudo-metals called mischmetals

Hung Low

Modern engines are almost at the levels of 99% efficiency from every drop of fuel used. The real issue is thermal efficiency (25% – 35% for an internal combustion engine. Improving thermal efficiency means better utilising the energy(heat) created via the combustion process. Unless there are innovate design changes to the regular Piston engines that improve inherent drivetrain losses, such as camless engines or the use of insulating coatings on internals. Rule of thumb is that larger engines have better thermal efficiency such as 2 stroke diesel engines used in ships.
Adding H2(hydrogen) will also increase thermal efficiency.
Obviously I am not proposing one of those dodgy internet kits, but a proper ecu metered flow rate controller and injector giving an ideal mixture of H2 vs fuel. The result would be better brake thermal efficiency, better emissions from better combustion.
The problem is the packaging and implementation of such a device, and the energy used in producing the H2 in the first place needs to be considered unless heat losses are recycled to generate electrolysis of H20 into H2+O?

Nath746

99% efficiency my a**. The amount of stored energy in a Petrol Molecule is heaps. Considering that there are many billions of molecules in a tank of petrol, we should be getting huge amounts of power and very high fuel efficiency. maybe 70% tops, but i think about 50% efficiency. Engines still have a long way to come.

Hung Low

Sorry typo, the figure is closer to 60% with a high tech modern engine.

http://electric-vehicles-cars-bikes.blogspot.com/ Paul

thermoelectric generator are around 1-2% energy efficient so don’t expect more than a couple 100 watts out of these devices.