Gareth Evans reports on the latest generation of BAE Systems’ hybrid technology, which has hit the streets with the launch of 39 ADL Enviro400Hs at Go-Ahead London [wlm_nonmember][…]
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Alexander Dennis Limited (ADL) and BAE Systems launched the first 39 Enviro400H double-deck buses with the latest Series-E hybrid technology with Go-Ahead London on Thursday (May 10).
The inaugural batch of buses to boast the new system which is set to slash the lifetime cost of the hybrids, are now entering service at New Cross Gate garage’s route 36 (New Cross Gate – Peckham – Camberwell – Victoria – Paddington – Maida Hill – Queens Park). A further 26 examples are on order for Stockwell garage’s routes 77 (Tooting Station – Clapham Junction – Vauxhall – Waterloo) and 87 (Aldwych – Trafalgar Square – Vauxhall – Clapham Junction – Wandsworth).
The system explained
Using ultra-capacitor energy storage to further reduce life cycle costs, this next generation hybrid bus has achieved Ultra Low Emission Bus (ULEB) certification with 37% lower greenhouse gas emissions than conventional diesel buses.
Series-E maintains the series hybrid system architecture – proven in over 1,300 existing Enviro400H hybrid buses – in which the diesel engine only acts as generator to produce energy for the electric drive. This now utilises a lighter and more compact direct drive permanent magnet traction motor, which no longer requires a speed reducing gearbox, thereby increasing efficiency and minimising wear. An ultra-capacitor energy storage system replaces the previous generation’s batteries. Designed to last the lifetime of the bus, this ultra-capacitor storage will reduce total cost of ownership by not requiring mid-life replacement. Due to this and other improvements, a 53% reduction in the cost of parts and consumables is predicted over a 10-year period.
Through its increased efficiency, the Enviro400H with Series-E hybrid technology has demonstrated best-in-class fuel economy in the LowCVP’s UK Bus test cycle, with fuel consumption 6% lower than its predecessor. Tank-to-wheel CO2 equivalent emissions of 684.9g/km are 37% lower than those of a conventional Euro VI diesel bus, making the Enviro400H with Series-E technology an Ultra Low Emission Bus and qualifying it for funding from the Department for Transport’s ongoing £48m ULEB scheme.
Stuart Cottrell, Head of Advanced Engineering at ADL took up the story: “The development of low carbon bus technology has been supported by Government grant aid. The competition has recently been opened for the £48m available in the 2018 ULEB scheme – the deadline for which is the end of June.
“Some of those bids will have to be submitted with predicted numbers, but ours is the first bus in the UK to have been certified as a ULEB, which should hopefully de-risk a lot of that bidding process for operators and local authorities. It also qualifies for higher BSOG (Bus Service Operators Grant) rates in England (outside London) and Scotland.
“A key point to consider is that with the Series-E hybrid, a 37% reduction in greenhouse gas emissions can be achieved quickly without the need for any costly infrastructure or changes to duty cycles.”
Stuart added that compared to Euro III, Euro VI emits 12 times less NOx and 10 times less particulate matter.
Matthew Lawrence, Business Development Manager at BAE Systems provided a more in-depth explanation in the developments of the Series-E: “The big change is that instead of a lithium-ion (li-on) storage system, we have a capacitor-based system – a key advantage of which is that no mid-life battery refresh is required. That focussed down on the Total Cost of Ownership (TCO) of the vehicles – we’re looking at a 53% saving over 10 years.
“The batteries on the previous system used li-ion cylindrical cells – the same type found in power tools. There was roughly 12 kWh of energy storage, with forced air cooling. We learned that actually, pulling in air from the outside also brings with it dust, so from a maintenance perspective, we’ve now moved over to fully sealed energy storage. It’s still air cooled, but the modules inside are sealed.
“With the capacitors however, the storage is a lot less – under 1 kWh. Because it’s used in a different way, energy can be pulled in and out a lot quicker without lifeing them. It’s an entirely different type of energy storage system.
“The ultra capacitor storage system is designed to last the lifetime of the bus. In London, that would be 12 years. When it reaches year 13, we don’t expect them to fall off a cliff. It’s difficult to project that far into the future. The ultra capacitors can be replaced.”
Matthew highlighted other improvements too: “As well as the battery, we’ve developed a new direct drive permanent magnet traction motor, which is designed to provide maximum efficiency. Our older version of the traction motor had a speed reducing gearbox, but that’s now been designed out, resulting in fewer parts and greater reliability. The power you can get from a permanent magnet is amazing these days. It’s lighter – weight being a key issue for efficiency.
“It has a mechanically-driven oil pump too – the electrically-driven pump fitted to previous generations caused issues in the field. The new pump is lighter, more compact and should aid reliability.”
Matthew was, however, keen to stress that the Series-E system is not radically different from its predecessor – and that users will be familiar with the features: “It’s the same core of the driveline that’s now been in service for years. There is no change for drivers either as the new system matches its predecessor’s performance. Passengers continue to enjoy smooth acceleration and braking, while pedestrians and local residents continue to benefit from the arrive-and-go mode which turns off the Euro VI diesel engine at low speed and when stationary at bus stops, cutting out noise and emissions.
“Neither is there a significant change to the maintenance regime, with the annual cleaning or change of a new filter on the energy storage system offset by reduced dirt ingress to a relocated hybrid unit cooler pack.”
Asked about warranty options, Matthew replied: “We’re offering a range of options – up to 10 years. If a customer wants it, we’ll offer it.”
In terms of cost, he said the product is “attractively priced.”
Echoing Stuart, Matthew concluded: “The Series-E not only suits London operators, but gives bus companies around the country the opportunity to apply for DfT 2018 ULEB scheme with a proven solution supported by existing infrastructure.”
Operator reaction
A third of Go-Ahead London’s 1,250-bus fleet are hybrids from Volvo and BAE Systems/ADL. The operator took five of the original TB-08s back in 2008.
Richard Harrington, Go-Ahead London’s Engineering Director, said: “With 245 Enviro400H already in our fleet, we know ADL and BAE Systems’ Enviro400H is a reliable bus that helps us improve London’s air quality. This experience gave us the confidence to place a volume order for the new Series-E version, and we look forward to recognising its improved fuel economy and lower cost of ownership.
“Realistically, we’re not going to go electric overnight – there is room for clean technology such as Euro VI diesel and especially Euro VI hybrids. 53% our fleet is currently Euro VI, but with the help of TfL, it will go to 100% in the coming years. It can be hard when you’re in a competitive tendering industry to keep pushing the boundaries.”
Asked what made him choose to be the first operator of the latest Series-E hybrids, Richard replied: “You’ve got to keep a competitive advantage and as soon as you do, other operators follow or another technology emerges.
“Clearly, we don’t want too many variances in the fleet but we do want to see what’s out there. With this product, the additional fuel economy was an advantage, but the TCO – taking away that massive burden of dealing with the battery pack half way through the vehicle’s life was the key driving force.”
Future
With fully electric power transmission, the modular architecture of BAE Systems’ technology opens up the future possibility of offering the extended range Series-ER hybrid system if there is sufficient demand for this solution – according to Matthew.
“We recognise some operators want to have more EV performance. This particular technology offers up to 10km of zero-emission range for a double-decker bus with geofencing – and there is still no need for a plug-in infrastructure,” he said.
Enviro 400 Hybrid advancements
ADL and BAE Systems have been working in partnership since 2008 and together have brought over 1,300 Enviro400H hybrid buses to the streets of London and the provinces. Here’s a brief outline of the evolution from Euro IV to Euro VI:
Enviro400H Euro IV with TB-08 Hybrid System
- Manufactured 2008-2010
- Series hybrid architecture
- Li-ion energy storage
- No electrical accessories – a basic hybrid driveline
- No engine stop-start
Enviro400H Euro V & VI with HDS100 Hybrid System
- Manufactured 2010-2018
- Series hybrid architecture
- Li-ion energy storage
- Electric used for accessories, incl. power steering and engine cooling (Euro VI)
- Arrive-and-go (engine switches off – electric mode around stops)
Enviro400H Euro VI with Series-E Hybrid System
- Launched 2018
- Series hybrid architecture
- Ultra-capacitor energy storage (Li-ion option)
- Electric used for accessories, incl. power steering and engine cooling (Euro VI)
- Arrive-and-go (engine switches off – electric mode around stops)
- No battery refresh at mid-life with ultra-capacitor