the key to class 8 hybrid truck success --- exhaust energy ...tett+-+bowman+po… · the key to...
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The key to Class 8 hybrid truck success ---
Exhaust Energy Recovery
28th Sept 2011
Dick Tett Commercial Director
Bowman Power Group Ltd. Southampton, UK.
E: [email protected] T: +44 (2380) 236700 Automotive World Commercial Vehicle Innovation Summit Sep 2011
Introduction to Bowman
Bowman is a privately owned technology company, based in Southampton, UK . The company has world class expertise and experience in 3 key technology areas:
compact, reliable, efficient, turbomachinery high speed, high efficiency electrical machines software controlled power electronics
Our core belief: by integrating high speed electrical machines with turbomachinery, significant reciprocating engine performance enhancements can be achieved.
Introduction to Bowman
Our focus is the heavy engine industry (not passenger cars or light commercial) in the power range 150-2000kW. Bowman is a recognised leader in the design, development and application of exhaust energy recovery hardware for many of the world’s leading engine OEMs:
Heavy vehicles, on- and off-road Stationary power generation Fuels: Diesel, plant oils, gas fuels
in variety of hardware configurations:
Turbogenerator (exhaust power turbine with integrated e-machine) e-Turbo (e-machine integrated with turbocharger) ORC turbine-generators and systems wastegate flow energy recovery EV range extenders
10 October, 2011
Contents
• Challenges for heavy vehicle
OEMs – Emission legislation – Fuel cost and CO2 legislation – Enabling technologies – Why exhaust energy recovery?
• Energy recovery technologies – Mechanical turbocompounding – Electric turbocompounding – E-Turbo – Organic rankine cycle – Thermo-electric
• Comparison of Technologies
– Pro’s and cons – Status of development
• Conclusions
4
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OEM Challenges Clean air emissions
In previous decades, Governments across the world have legislated for dramatically cleaner engines, The Truck industry has continuously met that challenge with effective, innovative and reliable technology…
European Emission Limits for NOx and PM
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OEM Challenges - GHG emissions
US Diesel Pump Prices (1994-2011, $)
The new Industry challenge: CO2 legislation
=GHG emission standards = fuel economy improvement
…and its time to do it again !!
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Operator costs
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Enabling Technologies for engine performance improvement
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Turbocharging
4-Valve engines
High pressure fuel injection
Heat recovery
Time
Spec
ific
Fuel
Con
sum
ptio
n
Normally aspirated, 2 valve
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Exhaust energy recovery
22.4%
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Exhaust energy recovery /2
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Heat recovery technologies - Mechanical turbocompounding
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• Adds a power turbine after the turbocharger
• Pressure difference across the power turbine is used to extract further heat energy from the exhaust gas
• This energy is converted to shaft power and fed back into the engine via a high ratio transmission
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Charge air cooler
Turbocharger
Engine High ratio transmission
Power turbine
How it works…
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Heat recovery technologies - Electric turbocompounding
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• Adds a power turbine after the turbocharger
• Pressure difference across the power turbine is used to extract heat from the exhaust gas
• This heat is converted to electric power,
• The power can be used on the vehicle, or fed back into the drivetrain via an electric motor
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Charge air cooler
Turbocharger
Engine High ratio transmission
Turbine generator
How it works…
~
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Heat recovery technologies - E-Turbo
• E-Turbo places an electrical machine onto the same shaft as the turbocharger.
• The exhaust turbine can be designed to recover more power than the compressor consumes; the net power is used to generate electricity
• Also has the advantage that the shaft can be motored to increase boost and improve transient performance
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Engine
Charge air cooler
E-Turbo
Power
How it works…
~
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Heat recovery technologies - Organic rankine cycle
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How it works…
• Addition of a separate, closed, fluid cycle to the diesel engine
• The fluid is: • pressurised • heated by exhaust energy/ • expanded to generate shaft power • condensed and returned
• Steam or organic fluids
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Heat recovery technologies - Thermo-electric
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How it works… • By selecting materials with appropriate
semiconducting properties, heat photons are collected and converted to phonons (vibration energy).
• These phonons then release electrons in the lattice that flow in a circuit
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Comparison of options - Mechanical turbocompounding
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Long History Available on some large modern HCV engines
• Scania (1991), Volvo, Daimler, Iveco
Development status
Pros and Cons + Average BSFC improvement ~3%
- Negative impact on BSFC at some points
- Complex, not easily additive to existing engine platforms
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Comparison of options - Electric turbocompounding
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Turbogenerator mounted on-engine for truck application
Turbogenerator on power generating set
Turbogenerator mounted off-engine for truck application
Development Status
Pros and Cons
In series production for base load powergen 250-1000kW
48% shaft efficiency demonstrated (gas fuel)
OEM development testing in progress on a variety of HCV test engines and vehicles
+ High BSFC improvement ~7%
+ Turbine is decoupled from engine – effective over broad range of speed and power
+ No negative impact on BSFC at any point
+ more easily added to existing platforms
- Requires a motor to return power to drive train
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Comparison of options - E-Turbo
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Several companies have had only limited development success Main challenges surround rotor cooling and turbine efficiency map Bowman has developed new concept with high efficiency E-Machine, high efficiency turbine and novel layout
Development Status
Pros and Cons
Can run up and down engine speed line to change boost pressure
+ Shaft can be motored to control boost and improve transient response
+ can recover excess exhaust energy – but need a motor
- Lower energy recovery possible - need to control to compressor needs
- High exhaust temps a challenge for the e-machine
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Comparison of options - Organic rankine cycle
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Development status
Pros and Cons
Available commercially for powergen applications at sizes 100kW to 2000kW
Under development by OEMs for truck applications
Maxtecc ORC for a powergen application
+ can extract heat from a non-pressured source (eg exhaust cooler)
+ potentially interesting fuel savings
- Complex system – cost, reliability, packaging
- Exotic fluids needed for best performance
- Need a motor to return power to drivetrain
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Comparison of options - Thermo-electric
• Proven technology • Development focus is limited power
applications (eg pass car A/C) • Path to commercial vehicle use (many
tens of kWs) very challenging
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Development Status
Pros and Cons
+ may be additive to other exhaust energy recovery technologies
- Exotic materials = prohibiitive cost unless material breakthroughs occur
- Currently only sub-kW scale
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Conclusions
• GHG legislation is good legislation – technology investment is offset by fuel savings
• Mechanical turbocompounding is an available solution to recover exhaust energy - but is application specific and has modest gains
• Due to independent turbine speed control, electric turbocompounding gives a notably higher benefit across the operating range
• This, like other emerging energy reduction technologies (E-Turbo/ ORC/Thermo-electric)’s all bring a new dimension – electric power
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Class 8 hybrids
Present hybrids are mainly lighter commercial vehicles for city driving – drive cycle dominated by stop / start and brake energy recovery (which need batteries). Brake energy recovery demands expensive batteries - generates power when there is no demand for it, so have to store. Exhaust energy recovery only generates power when you need it – no need for storage.
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Class 8 hybrids -take the KISS challenge
For class 8 hybrid , battery systems represent a significant cost and technology risk which are slowing take up of energy recovery technologies For success in heavy duty applications, consider instead to go to mild hybrid with small or no energy stores (recovered energy used at the time of recovery). Open your minds to faster and wider use of HV power for ancilliaries –flexible and switchable.
Thank You