The UK-based low carbon engine technology specialist Controlled Power Technologies (CPT) says that the new 48V standard proposed by various automotive OEMs provides an ideal compromise for performance and cost in the development of a new generation of affordable super fuel-efficient cars.
“The convergence of global standards for fuel economy and CO2 emissions means that the auto industry will need to embrace exhaust gas energy recuperation as well as kinetic energy recovery by electro-mechanical means as the next major step for CO2 reduction,” commented Nick Pascoe, Chief Executive and Chief Technology Officer at Controlled Power Technologies, speaking on the eve of the Engine Expo international trade fair at Novi, Michigan. “Energy recuperation is the key to ground-breaking solutions that the motorist can afford and this has caused the industry to re-visit the previously mooted higher than 12 volts, but less than 60 volts, electrical architecture. Mild electrification deploying a proposed 48 volt standard will be a major factor for enabling the required motor-generator efficiency and power levels.”
Pascoe says the industry has reckoned the additional cost to the motorist to achieve the required 30% reduction in CO2 emissions is estimated at US$1,500 for a mid-size sedan, significantly less than the US$7,500 US federal subsidy for electric vehicles.
CPT sold its VTES electric supercharger business in December 2011 to Valeo for £30m (US$48m), after a team of engineers, originally established in the UK by Ford, then Visteon, had worked on the technology for over 10 years. Their switched-reluctance motor-generator technology was developed from the outset to be scalable to higher voltages.
CPT is now focused on bringing its closely related Cobra, SpeedStart and TIGERS technology to market readiness. Cobra is a water-cooled electric supercharger for commercial vehicle and off highway applications. SpeedStart is a water-cooled starter-motor and generator, and TIGERS is a water-cooled turbine integrated gas energy recovery system.
At 48V SpeedStart is able to provide torque assist to the engine for acceleration, reduce fuel consumption during cruise conditions, and harvest kinetic energy during braking. Brake energy alone is worth more than 60kJ/km accumulated over the New European Drive Cycle. Already developed for 12V, the CPT SpeedStart system is a belt-driven starter-motor and generator with its control and power electronics fully integrated into the liquid-cooled device. It’s also claimed to be the world’s first liquid-cooled switched reluctance motor-generator developed for automotive stop-start, eliminating the rare earth materials used in permanent magnet motors which currently predominate for alternators, conventional starter motors and first generation stop-start systems.
CPT anticipates having a 48V SpeedStart technology demonstrator running in 2013. Bench testing has indicated an increase in transient performance to 10kW of generation power, depending upon system specification. And the motoring power through direct torque assist to the engine has similarly increased, though duration becomes a critical parameter. The engine breakaway torque at zero rpm can also be increased to 95Nm – enough to start even large automotive engines.
CPT says it will also next year secure the first vehicle installation of its turbine integrated gas energy recovery system known as TIGERS in a UK government Technology Strategy Board (TSB) co-funded project. The VIPER ‘Vehicle Integrated Powertrain Energy Recovery’ project will build on CPT’s involvement in the Ricardo-led ‘HyBoost’ programme, which was similarly part-funded by the TSB. The VIPER project aims to develop more thermally efficient engines and technologies for thermal energy recovery, and is being led by Jaguar Land Rover. Other consortium members include Ford, IAV, BP, Dana, the University of Nottingham and Imperial College London. CPT is already running TIGERS on a dynamometer at 650 degrees Centigrade, which is close to the engine exhaust temperature of 800 degrees in a running vehicle. The TIGERS system has a generating efficiency of more than 70% and a maximum operating speed of 63,000rpm. The liquid-cooled generator is targeted to recover 2-4kW from an engine’s exhaust gases, equivalent to SpeedStart recuperating 40-75% of the braking energy generated during an NEDC test.
The VIPER programme will compare the TIGERS installation with thermo-electric generators (TEGs)where power levels and system cost remain major issues. The TIGERS-V platform will also be used in the programme to develop a sensing system; a stator and rotor design for continuous steady state operation; low pressure ratio high efficiency turbine optimisation; and bypass system design and development.
