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Low-cost mild hybrid architecture development
Controlled Power Technologies (CPT) is entering the final development stages of its 48V mild hybrid architecture, which is said to offer all the benefits of a full hybrid powertrain but with improved packaging and associated costs
Following almost three years of intensive testing, development and validation of advanced mild hybrid technologies with 48V ‘intelligent electrification’ applied to a Ford Focus project demonstrator, the ADEPT (advanced diesel-electric powertrain) consortium partners have announced that the project is on course to meet the stringent air quality and ultra-low emission requirements expected of near term next generation vehicles.
The ADEPT project is led by Ricardo in a research partnership including the Advanced Lead Acid Battery Consortium (ALABC), Controlled Power Technologies (CPT), Faurecia Emissions Control Technologies UK Ltd, Ford Motor Company and the University of Nottingham. The consortium aims to demonstrate the advanced 48V mild hybrid powertrain architecture, capable of delivering near full hybrid-scale diesel fuel efficiency and reduced CO2 emissions, through a highly cost-effective package, without compromising increasingly stringent European exhaust emission regulations, which currently require cars to meet Euro 6b air quality standards in terms of NOx, PM and CO.
In addition, the integration of hybrid and emissions control systems has the potential to deliver up to a 10 to 12% reduction in fuel consumption, equivalent to sub-80g/km of CO2 emissions (NEDC). Crucially, the technology can be delivered at lower costs than a more traditional approach of optimizing each system separately. Initial analysis shows that costs (based on Ricardo’s estimation) of less than €80 (US$88) per gram of CO2 reduction for every kilometre travelled is feasible through ADEPT technology. Ricardo believes the above package is very competitive with other fuel economy solutions such as full hybridisation.
The concept of intelligent electrification enables highly aggressive engine downsizing and down-speeding beyond what might normally be possible other than through more expensive hybridisation approaches. This is achieved through the use of torque assist from electrically harvested energy, temporarily stored in a 48V advanced lead-carbon battery with a high rate partial state-of-charge capability similar to a supercapacitor, in combination with 48V electrified ancillaries.
With sophisticated electronic control of the powertrain systems, torque assist can be used to ensure that performance is maintained – or improved upon – throughout the duty cycle while also reducing fuel consumption. By basing the system on 48V electrical architecture, the ADEPT project aims to achieve a highly optimal cost and performance trade-off, including ultra-low emissions, while also delivering significant fuel savings.
ADEPT powertrain architecture
The baseline vehicle for the ADEPT research and development programme is based on an already downsized and competitively fuel-efficient diesel Ford Focus ECOnetic 1.5TDCi, homologated with carbon dioxide emissions of 88g/km.
Key features of the vehicle systems include CPT’s water-cooled SpeedStart switched reluctance belt starter generator (BSG), capable of delivering in excess of 12kW of regenerative braking, as well as near instantaneous and near continuous torque assist levels of over 7kW – sufficient to enable significant engine down-speeding in addition to a highly capable start-stop functionality.
Further energy recovery is achieved from CPT’s exhaust mounted 48V turbine integrated exhaust gas energy recovery system known as TIGERS. Rated at 2.4kW, TIGERS is capable of providing further power recuperated from the exhaust downstream of the turbocharger. The exhaust gas is diverted to the TIGERS unit via two bespoke emissions control valves developed by Faurecia Emissions Controls technologies for the ADEPT project. Again, the recovered energy is stored in the advanced lead-carbon battery pack, providing a high power, high endurance, easily recyclable, lithium-free energy storage solution at a competitive cost.
The ADEPT powertrain includes a range of electrical ancillaries powered from the 48V system rather than directly from the engine, including for example, the vehicle air conditioning compressor. In addition to powering these ancillaries and facilitating a significantly improved start-stop functionality, ADEPT’s 48V architecture also provides significant levels of torque assist from the BSG to offset fuelling to the engine for improved fuel economy, and to increase overall powertrain torque capability for enhanced vehicle performance.
The control strategies deployed have been developed based on extensive vehicle systems simulation work. This has enabled the core powertrain and aftertreatment system, as well as the 48V BSG, ancillaries, battery pack and exhaust energy recovery system, to be operated in a seamless manner, while also providing a valuable computer-aided engineering (CAE) capability to explore further potential avenues of development and optimization opened up through intelligent 48V electrification.
Completion of development – testing ongoing
Following the announcement of the ADEPT project in September 2013, initial integration and development tests were carried out by the ADEPT team on an early ‘functional integration’ prototype, which was revealed late-2014. This enabled the project to carry out de-risking of components and systems, and also provided a platform for evaluating control concepts.
The final ADEPT demonstrator vehicle, which has now been completed, provides the fullest implementation of systems to be carried out by the team.
“We are really pleased to have achieved this important milestone of completion of the ADEPT demonstrator prototype,” commented Ricardo Innovations MD Thomas Gutwald. “While much development attention is currently focused on full hybrids and battery electric vehicles – including by Ricardo and its customers – I firmly believe that the concept of ‘intelligent electrification’ will have an extremely high level of mass market appeal, providing arguably a greater overall fuel and carbon emissions saving in the near to medium term due to its highly cost-effective focus on the combination of near-market, available technologies.”
The ADEPT research project is jointly funded by the UK Government’s Office for Low Emission Vehicles (OLEV) implemented through the UK innovation agency, Innovate UK, with matching contributions from the participating partners.
29 June 2016