Exhaust energy recovery
Transport systems support economic prosperity; however our transport systems
contribute 22% of total UK greenhouse gas emissions. The majority of this comes
from our cars. The internal combustion (IC) engine remains the most cost effective
and efficient device for converting liquid fuels to useful work. There is now
significant effort being applied to increase the fuel economy of IC engines.
Loughborough University is leading a project with partners from Cardiff and Herriot-Watt to demonstrate
the benefit of exhaust energy recovery. The key to the successful operation of the IC engine is a reliable
flow of fresh air into the engine to support the combustion process. To ensure a reliable flow of air into
the engine, exhaust gas must be removed quickly thereby creating a hot exhaust gas stream which has
the potential for generating additional useful energy.
Thermo-electric (TE) devices use the so called Seebeck effect where a structure consisting of materials of
differing conduction properties and subject to a temperature difference will generate a potential
difference. In an engine that temperature difference will be created between the exhaust gases and the
external air temperature. This is a large temperature difference and offers the potential for efficient
energy conversion. Theoretical considerations suggest that with a passenger car engine producing 50kW,
there is the potential to regenerate useful energy of between 9-12 kW. A TE generator equipped with
the best of modern thermo-electric materials will deliver about 1 kW and this is already enough to
consider, for example, replacing the vehicle alternator . A thermo-electric device is solid state, with no
moving parts and is likely to be more durable than other power generation methods.
The primary challenge for the successful application of TE methods is the quality of TE materials. At
present, bulk TE materials can only deliver a low efficiency. Newer materials and methods of combining
those materials in a single TE device offer a great deal of potential. Putting numbers on that potential
and showing what can be realised in practice is a research issue and will be addressed in the current
project.
The aim of this project is to demonstrate the best thermo-electric performance using the class of
materials known as Skutterudites. Properly understood and assembled into modules, these materials will
help produce TE performance competitive with a vehicle alternator. The modules will be tested, then
computer based models will be used in real time alongside a practical engine to predict the fuel economy
of a whole engine system.
The proposed work will use a technique known as component-in-the-loop that is being increasingly used
at Loughborough in the investigation of engine system concepts. The engine is operated in the laboratory
as in a real application. At the same time the TE device is simulated in real time on a fast computer that is
connected to both engine instrumentation and actuators. The model output is fed back to the engine
system to represent the electrical power produced by the TE generator.
For further information about this project please contact Prof Richard Stobart E: [email protected]
For further information about the Midlands Energy Consortium please contact Dr Helen Turner E: [email protected]