Irizar i4H: A coach for tomorrow’s cities, today
The innovative Irizar i4H hybrid coach uses a parallel hybrid drivetrain, which combines a tried-and-tested Cummins ISBe 6.7 litre 300 hp diesel engine with an advanced Eaton PHP hybrid transmission, incorporating an electric inverter and traction motor-generator, together with a conventional six-speed automated manual gearbox.
Combined electrical and internal combustion power, together with energy recovered using the electric motor/generator as a retarder, helps to reduce fuel consumption by over 20 per cent in mixed ‘real-life’ conditions, where relatively high-speed running on major roads is interspersed with stop-start urban traffic. An automated stop-start system also shuts down the diesel engine (if temperatures and battery condition allows) when the parking brake is applied, further reducing unnecessary exhaust emissions. The engine restarts automatically when the brake is released.
On a 13-metre length, the Irizar i4H can typically seat 57 people, or 53 with additional spaces for a wheelchair user and luggage stowage.
At low speeds, the Irizar i4H is propelled by electricity only (although the diesel engine still idles to power auxiliary systems such as air-conditioning), taking advantage of the low-speed torque provided by the three-phase 346V motor/generator. If the coach is accelerating or cruising, then the diesel engine revs up to combine with the electric motor to provide the optimum blend of power for the conditions. When the Irizar i4H slows, the diesel engine disengages and returns to idle, while the vehicle’s momentum turns the motor/generator to replenish the batteries. An added bonus is reduced load on the coach’s foundation brakes, which aids safety, reduces wear, and cuts particulate emissions as the motor/generator acts as a retarder.
Unlike some hybrids, care has been taken to make the Irizar i4H as safe and simple to work on as possible: there are only five cables carrying high-voltage current, and they are all within the engine bay. The engine bay itself is the same size as that of a conventional coach, and full luggage capacity is retained
An advanced temperature-management system segregates air-conditioning, and engine and battery cooling functions, with separate radiators independently cooled by dedicated electric fans which only operate as required. The fans can reverse to remove air-borne debris that might otherwise clog the system. Drive for the saloon air-conditioning system is taken directly from the diesel engine: utilising the power take-off that would normally drive the engine cooling fan; reducing parasitic losses.
The Cummins ISBe 6.7-litre, 300-hp diesel engine has genuine multi-fuel capability. It can run, without modification, on the renewable synthetic diesel fuel HVO which is made from bio-waste, conventional diesel, or any blend of the two fuels. Use of pure HVO will reduce engine CO2 output by up to 90 per cent.
An Irizar spokesperson said: “Companies are under increasing pressure to reduce their carbon footprints, and the Irizar i4H offers an opportunity to reduce CO2 output from passenger transport by 20 per cent without compromising comfort, convenience or safety. Much larger savings will be possible once HVO can be sourced to replace conventional ‘fossil’ diesel.
“Furthermore, with urban air quality and diesel emissions coming under increasing scrutiny, the Irizar i4H offers operators a ‘green’ card to play when it comes to maintaining unfettered access to sensitive city centres.
“While we are confident that coaches with conventional diesel drivelines will continue to dominate the long-haul and touring markets for many years to come, we also believe that operators of suburban – city-centre commuter services and inter-urban routes will increasingly demand innovative solutions to concerns raised over fossil-fuel consumption and urban air quality. The Irizar i4H gives these operators a means to offer clients and passengers a clean, safe and green travel experience.”