Un camión hibrido para el 2009?

ArvinMeritor (AM) announced this week that it had delivered a prototype diesel-electric hybrid heavy-truck for an 11-month evaluation by the world's largest retailer Wal-Mart. The plan is for Wal-Mart to put the Cummins-engined class 8 International chassis into regular 'linehaul', ie trunking, service at one of its big distribution centres.

Carsten Reinhardt, president of AM's commercial vehicle systems business, says that while most of today's hybrid systems are "best suited for stop-start applications," the powertrain of the vehicle supplied to Wal-Mart is specifically designed for linehaul trucks.

At speeds up to 77kph, in AM's words, 'vehicle propulsion is delivered entirely through an electric motor with power from lithium-ion batteries.' Above that speed threshold, approaching freeway cruise conditions, 'the drivetrain phases to a diesel-powered system, with the electric motor providing power only as required.'

Many truck powertrain engineers would question AM's implied assertion that a hybrid of any configuration could, at steady cruising speeds, deliver percentage fuel savings - with commensurate emission reductions - comparable to those achievable during urban stop-start running.

Unless Wal-Mart's evaluation truck spends a significant part of its operating time, typically at either end of its trunking runs, in urban areas where there are legislated emission restrictions, it is difficult to envisage the formidable initial on-cost of a hybrid being recouped in fuel bill reductions.