Alexander Dennis and BAE Systems are prepared for ULEB with its new Enviro400H. It drops batteries in favour of ultracapcitors and also looks towards zero-emission with an optional 10km of engine-off range
Alexander Dennis (ADL) last week became the first manufacturer to unveil a certified double-decker Ultra-Low Emission Bus (ULEB) in the form of its third-generation Enviro400H hybrid double-decker.
Certification makes the model eligible for the DfT’s £48m funding scheme of the same name. Work has been carried out in partnership with propulsion package supplier BAE Systems, and the two parties say that the E400H is best in class in terms of CO2 and NOx emissions.
But ULEB certification is not all. The E400H now has tank-to-wheel CO2 equivalent emissions that are 37% below those of a Euro 6 diesel, and fuel consumption that is 6% better than its hybrid predecessor. The former exceeds the baseline for qualification by 7%.
The deadline for ULEB scheme bids is 30 June. That puts submissions involving the latest-generation E400H in a favourable position, says ADL Head of Advanced Engineering Stuart Cottrell.
“Bids involving other double-decker types will use predicted figures. We have a signed certificate of compliance for the E400H. Our numbers are proven, and we are the only manufacturer that can say that.”
Goodbye batteries
The headline change to the updated E400H is the replacement of batteries with ultracapacitors as the energy storage medium. That greatly reduces the total cost of ownership by removing the need for mid-life battery replacement – a thorn in the existing E400H’s side. ADL and BAE Systems predict that the use of ultracapacitors will cut the cost of parts and consumables by 53% over a 10-year period.
Battery replacement, says Richard Harrington, Engineering Director of launch customer Go-Ahead London, has proved to be a “massive burden” for operators of earlier E400Hs, which illustrates how significant the change to ultracapacitors is.
There is one more major trick up the revamped E400H’s sleeve. Instead of the ultracapacitors, buyers can optionally specify a new lithium-ion energy storage system with a 32kWh capacity. That gives the E400H a ground-breaking zero-emission (ZE) range of up to 10km without the need for charging infrastructure. It can be geofenced, taking the bus into EV territory.
Advancing technology
BAE Systems will warrant the ultracapacitors for up to 10 years, and it says that they will last for the entirety of a typical 12-year London life. They are part of its third-generation hybrid driveline, the Series-E, which includes other refinements. The ultracapacitor unit is sealed and air-cooled. Previously, batteries had forced-air ventilation, which could lead to debris being drawn in.
Electricity generation is still by a Cummins ISB4.5 engine, but the traction motor is direct-drive and no longer has a gearbox attached. That, says BAE Systems Business Development Manager Matthew Lawrence, results in fewer moving parts, less weight, and better reliability.
The motor oil pump is now mechanically-driven, removing the issues that had been seen on the previous electrically-powered pump.
In an unusual development, the ultracapacitors have a significantly lower energy capacity than the batteries they replace. They store no more than 1kWh, against 12kWh in the batteries.
“Energy storage is much less, but it can be added and removed a lot more rapidly than before without compromising the ultracapacitors’ life,” adds Mr Lawrence.
Because of that, the ultracapacitor-equipped E400H remains able to run in engine-off mode on approach to and departure from bus stops. That was demonstrated by one of the first batch of 39 for Go-Ahead London.
Viable ZE ‘decker
The optional lithium-ion energy storage unit in the Series-ER package that gives a 10km ZE range is the same size as the ultracapacitor. That means that one variant of the new E400H could be repurposed as the other if required.
With the advent of Series-ER, focus has been removed from inductive charging as a means of delivering extended ZE range. The five such buses built will continue to be supported, but the concept forms no part of current plans unless worthwhile buyer interest is received.
“Things have moved on,” says ADL CEO Colin Robertson. “There is a reticence towards infrastructure to accommodate opportunity charging and the commercial and financial landscapes have changed.” Engine-off is relevant to the ULEB scheme. Buses able to run in ZE mode are eligible for support of up to 75% of the price uplift over a standard Euro 6 diesel; for those that can’t, the maximum is 50%.
ADL and BAE Systems believe that they have reset the bar with the next-generation E400H. If it does everything that they say it will, that assertion is very difficult to argue with.
routeone comment
There is no doubt that the most important aspect of the new E400H from a buyer’s perspective is the removal of the financially stressful call for mid-life battery change that has come to symbolise the existing model.
But ADL and BAE Systems – on their customers’ behalf – also have an eye on the future. If the 10km engine-off capability delivers, it is potentially one of the most notable developments in recent bus history.
A ZE zone has already been suggested in at least one city, and the new lithium-ion storage unit gives solid emission-free scope with no impact on overall range.
With no change to pricing, the E400H still attracts a premium over a standard diesel. But if local and national government is serious about tackling urban air quality, this is a bus that it should be looking to support as a bridge to full ZE.
