More 48 volt news comes from the UK as we learn Controlled Power Technologies (CPT) will demonstrate its 48-volt hybrid vehicle technology at the annual Low Carbon Vehicle conference and exhibition at Millbrook Proving Ground this week.
CPT said its unique proposition for a new class of affordable low voltage electric hybrid vehicles is its highly controllable switched reluctance (SR) motor-generators.
“SR machines avoid the use of expensive permanent magnets, so they give you an immediate cost as well as environmental benefit by avoiding pricey rare earth metals,” says CPT’s chief executive Nick Pascoe. “Effectively, it’s a simple stepper motor, in which you induce a non-permanent magnetic field. And since there’s no permanent magnetism, you can switch the electromagnetic coils very rapidly using electronic switching to rotate the stator field. This means that SR machines are very controllable. They do exactly what you program them to do. They’re also efficient across a wide speed range.”
The company explained in practice, this “simplicity” has taken more than a decade to turn into an electrical machine, able to control a hybrid vehicle in such a manner that it enables the design, development and test engineers to squeeze as much performance, drivability and fuel efficiency out of the powertrain as possible.
Just like a Formula 1 car, it means that within thousandths of a second the vehicle can be either recuperating kinetic energy under braking or harvesting thermal energy from energetic exhaust gases; or providing power and torque assist indirectly through electric supercharging or directly to the crankshaft by replacing a conventional alternator with a powerful switched reluctance machine, added CPT.
CPT will showcase its 48-volt technology with the latest iteration of its LC Super Hybrid program, being developed in partnership with the European Advanced Lead-Acid Battery Consortium (EALABC), which is supplying the lead-carbon batteries able to meet the requirements for high rate partial state-of-charge cycling of thousands of joules of energy constantly flowing in and out of the battery.
On top of its involvement in the ADEPT program, CPT said it has been focused on an important aspect of 48V hybridization in the third year of its LC Super Hybrid program by fine tuning its activation strategy for advanced implementation of regenerative braking and motoring assist; in layman’s terms, determining whether the SR motor-generator is going to assist the engine with more torque, or whether it’s going to choose to recuperate energy, and the optimum conditions for doing so.
“Analysis of our data so far suggests a promising 17 percent fuel economy improvement compared with 7 percent for the otherwise identical 12 volts LC Super Hybrid demonstrator, both compared with the 1.4 liter VW Passat baseline,” said Pascoe. “This means we’ll have broken through the 5 liter/100 kilometers barrier and getting close to our target CO2 emissions of 115g/km – and importantly we’ve achieved this in a large family sedan with a small gasoline engine. It’s a real triumph, particularly as we have at the same time achieved the driveability and performance of a 2-liter class car. Yet the cost is only one-tenth the premium for high voltage plug-in hybrid and battery electric vehicles.”
The fuel economy currently being measured by CPT over the New European Drive Cycle is 4.9 liter per 100 kilometers (57mpg imperial and 47mpg US), said the company. EU legislators meanwhile are seeking to double the fuel-efficiency of new cars and halve their CO2 emissions by 2025. This means improving the automotive sector’s fuel economy, averaged over all vehicles in the fleet from the smallest to the largest, to 3 liters per 100kilometers (94mpg imperial and 78mpg US), up from the current standard of 6 liters per 100 kilometers (47mpg imperial and 39mpg US).
In the ADEPT program, CPT said 48V “intelligent electrification” is being applied to a diesel powertrain in a smaller car based on a Ford Focus.
“We’re midway through the ADEPT project announced at the LCV event last year,” says Pascoe. “The consortium was keen to show the progress we’re making, so it agreed at this year’s event to showcase a ‘pull ahead’ demonstrator with as much 48V functionality as possible applied to the 1.5-liter diesel engine. With more than half of new cars being registered in Europe with diesel engines, and given their inherent fuel economy advantage, and hence global predominance and the powertrain of choice in trucks and buses, it’s an important research and development program supported by the UK’s innovation agency, the Technology Strategy Board.”
CPT explained its 10-kilowatt SpeedStart belt-integrated motor-generator incorporated into the ADEPT demonstrator to provide motoring assist and regenerative braking kinetic energy recovery will soon be uprated to 12.5 kilowatt. CPT added its Tigers turbine integrated generator has been similarly integrated into the exhaust system to harvest thermal energy from fast flowing exhaust gases. Both machines are water cooled with the power and control electronic systems fully integrated, and hence fully temperature controlled for robustness and durability. Both applications of CPT’s switched reluctance machines, developed over the past decade, are at a high level of production readiness, with the SpeedStart system having been validated for 2.5 million stop-starts as well as the additional functionality available at 48 volts.
“An important objective for the ADEPT program is using 48V hybridization to reduce the load on the exhaust after treatment, which is increasingly a major additional cost on a diesel engine; when you can pay £2,000 or more than in a car fuelled by gasoline,” says Pascoe. “This is because you need additional particulate filters and catalysts. Hybridization can be used to reduce the base emissions, and hence lowers the cost of expensive after treatment.”
The third application of CPT’s advanced switched-reluctance machines is electric supercharging, stated the company. Already commercialized for car applications through the sale of its VTES business to Valeo in December 2011, CPT is now focused on applying its COBRA (COntrolled Boosting for Rapid response Applications) heavy duty switched reluctance electric supercharger to buses and commercial vehicles – again with the focus on reducing the cost of expensive after treatment currently required for diesel engines and as an enabler of engine downsizing and higher gear ratios without loss of performance and drivability.
“One of the problems with large diesel engines is transient response and their turbochargers being unable keep up with the fuel injection system,” says Pascoe. “If you’ve got an engine that is working hard, the black smoke you sometimes see is because of incomplete combustion. If you add an electric supercharger – and we’re in the process of retrofitting a number of transport fleets – you can provide air much earlier in the combustion process. It’s much more responsive than turbocharging alone. And as the automotive supply chain begins to fill up the parts bin with 48V components and achieves significant economies of scale, particularly for the electronic components, so it becomes increasingly attractive for truck and bus manufacturers to embrace switched reluctance motor-generator technology and apply the same principle of ‘intelligent electrification’ to their larger powertrains.”
CPT added they see and believe a 48 volt electrical architecture is currently the most cost-effective technology for achieving a significant reduction of all tailpipe emissions, as well as for improving fuel economy in the automotive and transportation sector, hence meeting future global legislation, while maintaining the drivability and performance of all manner of vehicles.
“In effect, we’re hybridizing a conventional powertrain with smaller low voltage electrical machines, rather than applying the power and torque from a single and much larger high voltage traction motor directly to the wheels,” added Pascoe.
CPT finalized its statement by stating it anticipates that the first vehicles to feature this smart hybridization of the powertrain, which transforms a downsized internal combustion engine into a highly efficient high performance power unit, will make their showroom debut from 2016 model year onwards.