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Mayor of London Introduces Hybrid Double-Deck Bus

Mayor Livingstone looks out the rear window of the new series hybrid double-decker. Click to enlarge.

The Mayor of London, Ken Livingstone, today unveiled the first hybrid double-deck bus in the world and announced plans for a hybrid bus fleet for London. (Earlier post.)

Built by Wrightbus, the double-decker is a series hybrid with a 660-volt lithium-ion battery pack powering two 85kW electric motors. A 1.9-liter Euro-4 diesel engine is the genset. By contrast, a conventional double-deck bus uses a 7-liter engine. The hybrid bus is expected to cut emissions by up to 40%.

Hybrid vehicles can make a real contribution to a cleaner, greener public transport network for the capital. Bus manufacturers and operators now need to rise to this challenge to make this economically and financially feasible.

Creating a low-carbon bus fleet is an important part of our work to cut the emissions which are causing climate change. It is an important step towards my vision that London becomes one of the world's most sustainable cities.

—Mayor of London Ken Livingstone

The adoption of hybrid buses is a key part of a range of measures being developed by the Mayor and Transport for London to meet London’s contribution to tackling climate change. The measures include:

  • Continuing modal shift from private car usage to public transport, cycling and walking;

  • Greater energy efficiency across all Transport for London businesses and modes of transport;

  • The adoption of more energy from renewable sources and innovative technology to recycle energy;

  • Support for the continued research and development of low carbon fuels;

  • Strategies and support for organisations and individuals to travel in more environmentally friendly ways through Travel Demand Management schemes, including in the London Borough of Sutton the largest of its kind in the UK; and

  • A new £25m climate change fund, to mitigate transport related emissions.

Transport for London currently has six single-deck hybrid buses operating on route 360 in London, from Elephant & Castle to Kensington and is actively pursuing the development and increased deployment of hybrid buses on London’s bus network. The single-deck Wrightbus Electrocity hybrids use an Enova 120kW series-hybrid drive coupled to Enova’s 60kW genset driven by a 1.9-liter Euro-4 common-rail diesel engine (Earlier post.)

The London Bus fleet includes 8,000 buses on 700 routes, carrying more than 6 million passengers per day. All buses in the London fleet meet at least Euro II emissions standards and have particulate traps, 60% meet Euro III standards and are also fitted with particulate traps, and buses meeting Euro IV standards are now being introduced.



I wonder if this guy would mind running for PM of Canada? The joker we have (Harper) is less than useless when it comes to the environment.

Sid Hoffman

You never know, maybe the UK will see it as a trade. North America gave Al Gore to the UK, maybe the UK can give this guy to North America (Canada)? In the end everyone goes home happy.. sort of. Almost makes you wonder if Gore could have had sweeping victory if he ran for office in Canada instead of the USA.


Gore lost at the margins because GW came across as a regular guy while Al Gore seemed like a nerd. (Even so, Gore didn't actually 'lose' the vote...but let bygones be bygones.) If more people were rational enough to vote for their own long term self-interests this would indeed be a different world.


Hehe, nice one gents.
_Seriously, hybrid buses (with Euro5 or Tier2Bin5 diesels) are a big boon for cities. If you can add more fast charge energy storage to make it plugin, you can recharge the bus at the end/beginning of the line at the terminals. Here in NYC, buses often sit at their terminals waiting to depart for up to half an hour. With 5-10 min periods of being parked at the curb, they can replenish 25-50% of their charge. The diesel can ensure that they will not stall if the batteries run out of charge. Routes are not too long, hence a 60-200 mi electric range should do.


At the terminals, the streets would need to be retrofitted with metered secure, safe, robust, and rugged electrical connections.


Enova Systems seems like they may be making there mark in the Hybrid Market. Better get in now. Looks like a good buy.


The defintion of "hybird" is a bit blurred here. Is this an electric hybird bus (series?) with a 1.9L charge-sustaining genset or is this a hybird similar to a Toyota Prius only it also has a dedicated 1.9L genset?

Max Reid

A 7 liter engine cut down to 1.9 liter genset - Thats great. Buses are very ideal for the Hybrid usage followed by Postal / Garbage trucks and then the Taxis.

Let London set the standard.

Dave Zeller

Does anyone know what the fuel economy is for these buses? Curiously, very few advocates of hybrid buses or the municipal operators seem willing or able to make many statements concerning this regard, and I wonder if this case is any different


A bus like this could be a plug-in hybrid using something like AltairNano's cells (zero to 80% charge in 60 seconds, anyone?).  Charging could be done through overhead contacts at stops, which would allow 100% replacement of motor fuel with a relatively modest battery pack.

Climate control in the winter might be an issue without an engine to provide waste heat, but the fuel, noise and CO2 reductions would be about as good as you could get.


How would the battery performance be affected by extreme conditions, say 10 deg F outside ambient temp?

George K


Found this pdf from a report regarding the ZEV Technology Symposium of October 17, 06. Page down to Session VI, and click on Status of Lithium Ion Batteries…

There is a lot of info, but about ½ way down, they talk about temperature testing. One chart shows voltage at room temperature and –30C to be about 90% similar. Other charts on charging look just as promising at low and high temperatures!

A bus like this could be a plug-in hybrid using something like AltairNano's cells (zero to 80% charge in 60 seconds, anyone?).

They have such a battery available for sale at a reasonable price?

Thomas Pedersen


The one-deck version uses 40% less fuel compared to its pure-diesel counterpart. Its emissions are much lower as well, not to mention the fact that noise levels are 4 dB lower.

You can read more from these links:

Seeing how *every* diesel vehicle emits a cloud of black smoke during heavy acceleration, I would suspect that real-world reduction in particulate emission is quite significant, since the buses are run solely by the electric motors - there is no mechanical link between the diesel engine and the wheels. Therefore, the engine does not have to be revved high during acceleration.


Thomas P., not every diesel puts out any black smoke on acceleration. This has largely gone away in the US for diesels made since 2000 or so, which have better fuel injection systems that don't go rich and don't lead to smoke. Obviously smoke (particulate matter) is nasty pollution. You will also see smoke disappear completely with 2007+ diesels in the US, which will all have particulate traps that collect PM and burn it off. Modern european diesels have the same technology though I don't know the year in which it was or will be implemented.

Rafael Seidl

JJ -

these buses are series hybrids with gensets running at constant, optimal speed and load.

Dave Zeller -

conventional city buses get about 3-5 MPG. TfL has claims a 40% improvement due to hybridization.

Zach -

wall-flow DPFs have actually been around since the 1980s but only recently has engine control hardware and software advanced to the point where these devices actually last for the lifetime of the vehicle. Peugeot was the first manufacturer to offer DPFs in series production diesel cars.

Several German manufacturers actually managed to meet EU 4 emissions without a particulate filter, but consumers are demanding them anyhow because they don't want their cars emitting embarassing puffs of smoke. Also, vehicles with wall-flow DPFs have higher resale value.

Note that the visible portion of diesel smoke fouls building facades and windows but actually does the least harm in medical terms because it is caught in the upper reaches of the respiratory system. More serious is the very fine invisible PM below ~7 microns in diameter, because it can pass through the alveolae into the bloodstream and accumulate in the liver.

Sulfur in the fuel substantially increases the harm done by particulate matter, which represents a large aggregate surface area for the sulfuric acid to catalyze chemical reactions. Therefore, ULSD and EU2010 diesel grades contribute to mitigating the health problems caused by PM.

Current PM measurements systems for vehicle certification are based on weighing a filter plate before and after, under precisely controlled humidity conditions. These measurements are difficult and the filter plates limit accuracy to 10 microns (PM10). Unfortunately, the more harmful ultra-fine particles contribute very little to total PM mass.

Newer, much more expensive, equipment can measure PM2.5 levels optically. Precise experiments have suggested that wall-flow DPFs do not substantially affect the size distribution of particulate matter in diesel exhaust gas. Rather, they reduce particle counts across the board by up to 98%.


Biodiesel added to Euro market diesel (to make B5) will make it a bit easier to meet Euro5 PM standards. It may give the automakers the leeway, to tweak their engines to favor NOX reduction a bit, to meet the emission standard. The lubricity will help a little too.

Rafael Seidl

Allen -

B5 is in line with the objectives of the EU "20 by 20" program for 2010. Here in Austria, the timeline has been more aggressive to placate farm interest. All of our on-road diesel is already B5 today.

Wrt meeting Euro 5, though, carmakers are not counting on the fuel. DPFs are widely expected to become quasi-mandatory. An interesting development published in the past two months related to homogenous diesel combustion, something we'll be hearing a lot more of in coming years.

Turns out that by using so-called split combustion at elevated loads, i.e. combusting part of the fuel homogenously and the rest conventionally, it is already possible to achieve Euro 5 levels in NEDC tests without expensive aftertreatment systems. The snag is that at the current, early stage of this research, the fuel consumption goes up by an unacceptable 5-10% relative to conventional combustion. More fine-tuning of the thermodynamics is required.;/site=a4e/lng=en/do=show/alloc=3/id=5726;/site=a4e/lng=en/do=show/alloc=3/id=5793


It is indeed great the concept of two stage bus fleet that reduces CO2 emmisions by 30%. Rest also can be reduced drastically by planting trees on all hills and hillocks all over the world. The trees can absorb CO2 and release Oxygen. This in turn helps climate change to safe levels.


Well, pizmo, let's assume we could get such a battery pack at $1000/kWh (about 2.5 times today's conventional Li-ion price at wholesale).

If the batteries will cycle 16,000 times (number chosen for convenience), that's 6.25¢/kWh for the energy put through the batteries.  If I'm using them on board a bus which would achieve 4 MPG @ 25% drivetrain efficiency in stop-and-go service (allowing for torque converter inefficiencies), that's about 10 kWh of fuel per mile converted to 2.5 kWh of work.  If I recharge the batteries every 3 miles or less, I need maybe 10 kWh of cells.  Call it 20 kWh just in case, so the capital cost is $20,000.

Cost of diesel fuel @ 4 MPG is about 60¢/mile, perhaps 70-75¢ in the near future.  The batteries let me replace that with perhaps 3.5 kWh/mile of juice from the grid, 35¢/mile @ 10¢/kWh.  If the bus covers 100 miles/day the energy savings come to $25/day at the low end, $50/day at the high end.  At $25/day the annual savings are about $9100; at $50/day, $18250.  Those batteries would pay off mighty fast, wouldn't they?  And at 17 cycles/day (for the 20 kWh model), you'd get about 2.4 years of use before battery capacity dropped as low as 85% of new.  You could probably use them for some time beyond that.

If the lithium titanium spinel chemistry can be made competitive with conventional lithium-ion, the battery cost comes to about $8000-$10000.  It pays off in about a year at today's fuel prices even before you factor in the reduced maintenance costs of electric drive.

So yeah, I see these things taking off just as soon as some smart cookie finds a way to integrate a hands-off fast-charging system with a covered bus stop.


So the short answer is that, no, they aren't actually available.

Cheryl Ho

There are developments in DME in China today:
We see great potential for DME as a clean alternative fuel . The present diesel oil is a major source of air pollution from diesel engine of trucks and busses in large city like Tokyo. The potential market of diesel oil substitute is larger than LPG. DME is one of ideal fuel for diesel engine. DME vehicles were demonstratively manufactured in Japan, China and Korea and their driving test already started. Practical durability fleet test of a DME truck is under going in Japan.

We are pleased to organise a conference on China taking the lead in the DME market in production from coal and Japan and Korea activities.

If you would like to know more on COAL to Syngas to DME developments, join us at upcoming North Asia DME / Methanol conference in Beijing, 27-28 June 2007, St Regis Hotel. The conference covers key areas which include:

DME productivity can be much higher especially if
country energy policies makes an effort comparable to
that invested in increasing supply.
National Development Reform Commission NDRC
Ministry of Energy for Mongolia

Production of DME/ Methanol through biomass
gasification could potentially be commercialized
Shandong University completed Pilot plant in Jinan and
will be sharing their experience.

Advances in conversion technologies are readily
available and offer exciting potential of DME as a
chemical feedstock
By: Kogas, Lurgi and Haldor Topsoe

Available project finance supports the investments
that DME/ Methanol can play a large energy supply role
By: International Finance Corporation

For more information:

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