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ProPulse: The viable hybrid
Page 16
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by Colin Barnett Hybrid diesel-electric trucks could be commercially viable within three to five years, according to US military and municipal vehicle specialist Oshkosh.
Its ProPulse technology, a spin-off from military vehicle research, is based around the use of capacitors for energy storage, unlike Allison's battery-based EP Electric Drive system, revealed at the recent CV Show. The Oshkosh view of competing technologies is that batteries have reached the end of their development, while the perfection of hydrogen fuel cells is still too far away.
In simple terms, the ProPulse system uses a diesel-powered electrical generator to maintain a charge in the power pack which contains an array of ultra-capacitors. The energy is then used to power wheel or chassis-mounted drive motors.
The use of smaller diesel engines, operating at higher efficiency within a narrower speed range, will ensure greatly Improved emissions. The drive motors also utilise regenerative braking to create energy during deceleration. Oshkosh claims a fuel economy Improvement of up to 40%. During the development of ProPulse, Oshkosh used the Toyota Prius hybrid car, now a mainstream production model in the UK, as the baseline for an operator-ready installation.
By Oshkosh's definition, commercial viability will be achieved when ProPulse can match conventional diesel/mechanical drivelines in terms of performance, packaging and cost. The first criterion Is already met, with a fully-operational prototype currently In the UK for defence evaluation.
The second is improving all the time, as the capacitor cells are rapidly being reduced in size. Today, they are about the size of a beer can, with 200-500 cells needed per vehicle, dependent on the application. Oshkosh admits the thirdcost—will come down, but only with the economies of scale offered by full commercial production.
Principal ProPulse applications within the civilian world would include refuse collection vehicles, where near-silent and low-emission running of both tractive and compacting functions in urban environ merits would be welcome. As the Oshkosh operation incorporates the Liantrisantbuiit Ceesink Norba RCV product range, it's easy to see the potential in that area.
Another key target market is fire appliances. The nature of the ProPulse system is such that the engine could be located anywhere, not just at the front under the cab.
Crew accommodation and equipment layout could be arranged in the most efficient way without current compromises. The system's energy reserves could also be used to power lighting and equipment at an incident scene.
The 400kW prototype has already been demonstrated providing the entire energy needs of an airfield near to its Wisconsin headquarters.