World’s first affordable diesel hybrid powertrain

Zytek has already proven its knowledge of powertrains and electric vehicle many times over, on and off the racetrack. Now, in collaboration with a UK Government initiative, the British engineering consultancy has developed a novel diesel hybrid powertrain that will be affordable in the most popular market segments. The new technology will allow vehicle owners to drive across London’s extended congestion charge zone for just four pence. The low-cost, high-efficiency hybrid-electric drivetrain offers a realistic alternative to expensive proprietary systems and can be quickly implemented within the packaging constraints of compact European passenger cars. A demonstration vehicle, built within the UK Government’s Ultra Low Carbon Car Challenge (ULCCC), has exceeded all targets set for the programme, delivering an exceptional 85g of CO2 per km compared with 121g/km for the already exceptionally efficient standard vehicle.

“Hybrid technology is now well established as a route to low emissions and outstanding fuel consumption, but so far it has carried a substantial price premium,” explains Zytek sales and marketing director Steve Tremble. “We wanted to develop a drivetrain that would make the many benefits of hybrid drive affordable within the most popular class of vehicle. We are delighted that the ULCCC, managed by the Energy Saving Trust, has supported this programme and allowed us to demonstrate the viability of our technology.”

Introducing the new technology at an event in London on December 5, Minister of State for Transport Dr Stephen Ladyman said: "If we are going to cut carbon emissions from road transport we need innovative new technologies. This launch shows that there is the potential to dramatically reduce emissions from cars, which is why the UK Government provides £5 million a year in a grant funding programme for investment in innovative low carbon road transport technologies."

The Ultra-Low Carbon Car Challenge is a two year, Government-supported programme to develop an affordable, five door vehicle with well-to-wheel CO2 emissions of less than 100g/km. To be eligible, the resulting vehicle must retain the space, features and safety of a conventional car in this class, whilst simultaneously delivering adequate performance. It must also be capable of reaching production within four to eight years at a commercially feasible price.

“The easy solution is to develop a premium vehicle that will be affordable when produced in volumes of hundreds of thousands a year,” says Tremble. “We wanted to develop something that breaks the mould, which can be accessible to many more people and therefore have a substantial impact on total road-car carbon emissions. To achieve this we took a fresh look at the available technologies and came up with a new, elegant yet very simple engineering solution.”

Another issue with today’s production hybrid drivetrains is that most rely on licensing agreements with the global leader in hybrid vehicles. “We wanted to develop a true alternative that gives vehicle manufacturers new opportunities in this fast-growing market,” says Tremble.

A novel dual-mode solution

Today’s passenger car production hybrids are either parallel or dual mode systems. Pure series hybrids offer high efficiency at low speeds but this greatly reduces as speed increases, and hence this drivetrain only finds application in low speed, stop start vehicles such as inner city buses. Parallel hybrids have the internal combustion engine permanently coupled to the wheels so are more efficient at high speeds, but offer less flexibility to optimise the drive for low speed duty cycles.

A new generation of dual mode transmissions offer the ability to operate in series or parallel mode so the drive can be optimised for each operating condition, but they are generally more complex and therefore larger and more expensive. There are also inevitable compromises in today’s production dual-mode designs.

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