Volvo hybrids launched in London
The vehicles use a parallel drive system in which both the diesel engine and the electric motor can be run simultaneously or independently. Unlike most other hybrid systems which have been developed specifically for urban bus operation, Volvo’s I-SAM system is also intended for use in trucks and construction equipment. Although the vehicles have been in trial service prior to their formal handover, Volvo declines to comment on fuel consumption figures at this stage, saying only that the hybrids offer an improvement of at least 30 per cent over conventional diesels. Rival maker Alexander Dennis is claiming a fuel saving of 40 per cent for its 12 London hybrids.
The Volvo I-SAM system comprises a combined starter motor, electric motor, generator and electronic control unit. It is linked to a 5-litre Volvo diesel engine and an I-Shift automated transmission. A lithium-ion battery stores energy generated from the braking system.
Volvo Buses Europe president Stefan Nordström said this week: “We are delighted to formally hand over our first six hybrid double-deck buses to Arriva London. The advanced parallel hybrid technology on these vehicles, unique to the Volvo Group, has the potential to offer significant fuel savings and resultant CO2 reductions, as well as significant air quality and noise benefits for other road users.
“The continuing trend in ever higher fuel prices means that the payback period on the incremental capital cost of this technology is being further reduced, making investment in hybrid vehicles a viable option for an ever increasing number of cities in Europe and beyond.”
Arriva London is running the Volvos alongside hybrids from Wrightbus which use a series hybrid drive, with both types operating on route 141 from Wood Green to London Bridge. Arriva London managing director Mark Yexley adds: “There’s no getting away from the fact that oil is running out and we are under pressure to reduce emissions. Hybrid technology looks the most practical and easy-to-live-with game in town.”
In service, the engine on the B5L switches off when the bus stops. Moving off from rest it can cover up to 600 metres on battery power before the engine kicks in again; alternatively the engine restarts when the vehicle reaches a speed of between 15 and 20 km/hr. For passengers the small Volvo engine is noisy and is running most of the time.
The Wrightbus-bodied B5Ls weigh 12,200kg unladen and have 60 seats plus room for up to 28 standees. This is 286kg lighter than the Wrightbus Gemini 2 hybrids operated by Arriva London.
Benefits claimed by Volvo for its I-SAM parallel drive are that on less intensive operations than in London it should provide better fuel economy than a series drive, although the immediate interest will centre on how it compares in London with the Wrightbus vehicles running on the same route. This will settle – one way or the other – concerns that a system developed by Volvo for a range of applications might prove to be a compromise when fitted to a bus.