Celebrating 800 hybrids in UK

Last week I had the opportunity to visit London. Hybrid Double Decker buses dominate the bus traffic in the centre of London.

Volvo B5LH Hybrid double decker bus in UK

One of the now more than 800 Volvo B5LH Hybrid buses in the UK, a 10.5 meter double decker with a body from Wrights.

Early 2009 the first 6 Volvo hybrid double decker buses (B5LH) were put into service in London. It did not take long until the first reports came. The Volvo double decker’s became top performers in reliability and fuel consumption. Since then, more than 800 hybrid buses have been put into service in the United Kingdom. Most of them are running in London.

I have collected some data from the last six years experience:

Average total yearly speed* of the UK selection: 18.5 km/h

90th percentile: 13 km/h (i.e. 90% of the buses run faster than 13 km/h)

10th percentile: 26 km/h (i.e. 10% of the buses run faster than 26 km/h)

Average yearly distance 58 000 km

*the speed includes all operation in service ant out of service (the criteria for accumulating fuel consumption data is that the key is turned to the “ON” position. In this way also “electric idle of hybrid buses is also included”


The fuel consumption of the average bus (running at 18.5 km/h) is: 34.9 liter / 100 km

The fuel consumption of the 90th percentile (running at 13 km/h) is: 41.2 liter / 100 km

The fuel consumption of the 10th percentile (running at 26 km/h) is: 28.6 liter / 100 km


Volvo has three recent technologies for Double Decker buses in UK.


Below we compare the fuel consumption performance for the gross number of buses in the UK. It should be noted that the buses run at different operators and in different types of service. The yearly average speed alone does not full describe the bus service. However gives a strong indication for which fuel consumption can be expected for different operation.

Table Fuel Economy, yearly average of the population here compared at an average speed of 15 km/h. The fuel saving is calculated as how much less fuel is required for the Hybrid to achieve bus service of the same distance as the diesel buses that it is compared to.


At lower speed the idle time increase and the fuel consumption increases for all buses.

Table Fuel Economy, yearly average of the population here compared at an average speed of 12.5 km/h. (there were too few B5TL buses running at the lower speed therefore significant data could not be extracted for comparing to the B5TL model at the low speed)

12.5 km/h miles / Gallon (UK) Liter / 100 km Saving to B9TL
B5LH 6.6 43 30%
B9TL 4.6 61 0%

In the same way the fuel consumption decreases when the total yearly speed is increased. speed the idle time increase and the fuel consumption increases for all buses.

Table Fuel Economy, yearly average of the population here compared at an average speed of 18 km/h.


When the fuel consumption is plotted to the average speed the following graph is obtained:

Volvo hybrid double decker in UK

As a final conclusion the following “back-of-an-envelope” calculation illustrate the impact of the hybrids in UK:

Number of Volvo Hybrid buses 800 fleet
Average fuel saving 14.88 liter per 100 km
Yearly distance 58 000 km
Total fleet yearly saving 6 904 m3
Fleet life-time fuel saving (12 years) 82 852 m3
Fleet daily fuel saving (365 days per year) 19 m3
Fleet cost saving (£1.15 per litre) 21 753 £ per day
Fleet CO2 saving (2.63 kg CO2 per litre) 50 tonnes per day

Table: Impact of hybrid bus fleet on fuel and CO2, the average bus having a speed of 18 km/h, and a fuel consumption 32.5 liter per 100 km. The average diesel bus (mix of all) has a fuel consumption of 48 liter per 100 km.

Now over to something completely different: Yesterday I visited the lake of Hornborgasjön close to the Volvo Engine factory in Skövde Sweden.

hornborgasjön1 ???????????????????????????????

The dance of the Crane birds is a spectacular event that gathers about 15 000 specimens of the Cranes (Grus Grus) and some thousands of the Homo sapiens specimen. Swans, ducks and other animals seem to be attracted to the event as well.

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What if all buses and coaches were electric?

If all Swedish buses and coaches were to be electrified, the total energy use would decrease and the shift from diesel and gas fuels to electricity would lead to an increase of the electric energy use by 1.2% compared to the total energy use today.

About to charge, at the inaguaration of line 109 in Hamburg.

About to charge, at the inaguaration of line 109 in Hamburg.

We know that the energy efficiency increase a lot when buses and coaches becomes electrified. This is the case both when “tank-to-wheel” and when “well-to-wheel” is studied. The reason is that buses and coaches have big engines to cope with their duty cycle that involves a lot of starts and stops. For example, a typical bus engine for a standard 12m bus has about 250 hp (horse power maximum output) while the average power outtake in a city duty cycle is about 50 hp. The average power-load is hence only 20% of the maximum power. The low average load leads to low efficiency. Or, to make a long story short, the average efficiency of the diesel engine in a bus duty cycle is about 20-30%. An average load below 30% is hence the case even when the efficiency in the most efficient load point can go beyond 45%.

Before proceeding to the impact on the electricity production and distribution I therefore want to firmly underline that the total energy use will in almost every real world situation lead to a decrease in total energy use.

In reality, since the life-time of a bus is more than 10 years, the paradigm shift will take place during a decade and there will be a lot of time to adapt the electricity production and the distribution chain to the new needs.

Nevertheless, as an example I have below looked-up some key data for my home country, Sweden, to answer the question:

What would the impact on the electric production and grid be if all buses and coaches in Sweden were to become plug-in or electric over-night?

Would the electric production capacity be sufficient?

Would the electric grid be capable of dealing with the increased power requirement?

To start I want to understand the relationships in terms of how many households does an electric bus correspond to? According to the Swedish Institute Elforsk, a household uses between 4 000 and 25 000 kWh electricity per year, depending on weather it is an average apartment or a private house with electric heating. In order to make a comparison I have assumed a yearly mileage of 55 000 km for a city bus with an average power use of 1.6 kWh per km. This number accounts for higher energy use at winter conditions but assumes that a biofuel is used for heating the bus compartment; else the energy use will be higher.

The charging station can provide 150 kW. The pantgraph is mounted on the stationary mast on a hight safe for other types of traffic.

The charging station can provide 150 kW. The pantgraph is mounted on the stationary mast on a hight safe for other types of traffic.

For the charging station I have assumed a high utilization of about 60%. This would be a worst case to relate to. One bus uses the same amount of electricity as between 4 and 22 households, depending on which type of household we compare to. Buses mostly give service to between 500 and 5 000 persons per day. One charging station will be able to serve several buses. It will transfer the same amount of electricity as used by between 15 and 100 households. It seems that the ball-park figures are reasonable.

Next, I want to understand the total energy use for buses, if they were to be electrified. The total number of registered buses and coaches were 14 203 (2012). This number includes all buses from 3.6 ton minibuses, to 40 ton 24m tall bi-articulated buses. Most buses in Sweden are between 12 and 14.5 meters. I have not found any reliable data for the average mileage. I have therefore used some rough assumptions to put us in the right ball park. Some school buses and spare buses are barely used while some few long distance coaches may travel more than 300 000 km / year. A guestimate gave me 70 000 km per year as an average for all buses and coaches. Since we now deal with all buses and coaches I also added some margin to the electricity use. An educated guess gives us: 2 kWh/km as a rough number to cover all sorts of traffic. This number does not include electricity for heating the compartment in the winter. This is for practical reasons assumed to be done with a biofuel.

The calculated energy use for all buses and coaches was about 2 109 kWh per year. As this number has no meaning for an old chemical engineer as myself. I want to relate it to the daily use of the citizens in Sweden. Again, I end up with a lot of numbers. The buses and coaches will use a fraction of the electricity used today in Sweden; 1.2% to be precise. Note that the production and use does not ad-up, since Sweden export electricity, in recent years.

In Sweden households use 23% of the electricity that is produced. Most of the electricity is used by industry (35%) and 24% is used by “Society services” (railway, street lights, hospitals etc). Buses are used mostly where people live (households) and where people work (Industry and at offices). It seems that theoretically, if there is a limitation in the electric distribution chain it would be close to the households. The relative increase of electricity use, if all electricity for the buses would be pulled from the part of the grid supporting households only, would increase the load on the grid by in average 5.3%. Provided that peak loads can be secured not to overlap in time for households and buses, we can conclude that the electric grid will not become a limitation in the distribution chain. This statement is only valid on a “city level”. Certainly, there may be local effects but in general it seems that the electric grid in Sweden will not pose a limitation for the electrification of the buses.

Next question: Is the production capacity of electricity a limitation to supply energy to electric buses and coaches?

There are of course several complex questions about spare capacity and peak capacity and the availability over time. For this a much more detailed analysis is required. Still some relations to the maximum capacity may give some indication for weather we are close to the production capacity limit or not. Again stressing that the analysis is an over simplification it is concluded that the electrification of all buses and coaches in Sweden will “eat” about 1.2% of the spare production capacity (it is a coincidence that both relative increase of electricity use and the relative use of spare capacity ends up at the same 1.2%).

Which conclusions can be drawn for Sweden?

1, On the national level there is sufficient production capacity of electricity to supply all buses and coaches with electricity, this as a yearly average.

2, On the city level (this is however not possible to claim on street or block level), the electric grid does not pose a limitation to distribute electricity to the buses.

3, Locally and time analysis requires a more detail data and analysis.

References: references

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Mexico City

On Wednesday the 20th of January Mexico City signed a memorandum of understanding with Volvo. The partners will cooperate to share information with the objective to realize environmentally sane public transports.

Mexico City has 9 million inhabitants and the region/urban area has 21 million inhabitants.
Like all megacities Mexico City has several urgent transport challenges:
-The car ridership is gradually increasing and the traffic is becoming increasingly congested.
-A large number of old micro and midi buses have negative impact on the air quality.
-Heavy transports contribute to road wear, noise and vibrations.
-Growth of the population  increase the demand for transport capacity and insufficient number of efficient alternatives give long transport times and high costs for citizens. This cost is both reflected in higher prices for the transports and in less time with friends and family.
-High interest rates and long lead times delay the required infra-structure investments.
-The synthesis of all the challenges give raise to a negative helix where energy use and emissions of greenhouse gases are increasing and not decreasing, as the urbanization should have potential for.

I have been involved in analyzing the potential of implementing clean and energy efficient bus systems. As in most of the cities where Volvo is involved in implementing the new technology (e.g. Hamburg) the new energy efficient bus systems can address all challenges for the person transports simultaneously. In congested traffic cars are mostly the main contributors to the congestion and buses can mostly provide efficient alternatives for many of the car users. The beauty of the new hybrid and electric bus systems is that they can meet all the environmental challenges by utilizing the existing road infrastructure. When given exclusivity the buses are getting faster and the car users are attracted to the public transports. The modern design and silent drive ads further to the attractiveness. With marginal additional investments in road infrastructure for fly-over congested crossing or dive-under waterways the new bus systems can raise the capacity with further advantage in environmental performance.

Volvo Mexico City MoU signature

The Memorandum of Understanding between Volvo Bus and Mexico City was signed by Rufino Leon Továr (Minister of Transports) for Mexico City and by Håkan Agnevall (Chief Executive Officer Volvo Bus) for Volvo Bus and it was witnessed by Tanya Muller (Mexico City Minister of Environment), Guillermo Calderon (Director Metrobus), Rafael Kiesel (Volvo, Ralph Acs (General Manager Volvo Bus Americas), Ileana Almazan (Director RTP), Jörgen Persson (Ambassador of Sweden in Mexico).


7900 Articulated Hybrid and my Self at the Plaza de la Constitution in Mexico City.

7900 Articulated Hybrid and my self at the Plaza de la Constitution in Mexico City.


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Hamburg inauguration Line 109

Last week the Innovation Line 109 was inaugurated in Hamburg. Volvo 7900 Electric Hybrid / Plug-in was in pole position (see video).

The event was hosted by Hamburg Mayor Olaf Scholz who is strongly driving the implementation of sustainable Public Transports in Hamburg.

Volvo Bus
Günther Elste (Chairman Hamburg Hochbahn), Olaf Sholz (Mayor Hamburg),  Olof Persson (President/CEO Volvo Group), Håkan Agnevall (Volvo Bus CEO) and Håkan Karlsson (EVP Volvo Group Busines Areas)


Volvo Bus

Håkan Agnevall (Volvo Bus CEO), Peter Schrauwen (Volvo Bus Hamburg Project Lead)  Håkan Karlsson (EVP Volvo Group Busines Areas) , Olof Persson (President/CEO Volvo Group), Tommy Hjelle (Volvo Electric/Hybrid Drive Specialist), Mats Franzen (Project Leader Electromobility visible in the back)

The city of Hamburg has established the target: from 2020, only emission-free buses should be acquired by the city. Volvo is determined to offer buses that meets the requirements of Hamburg.

I claim that the 7900 Electric Hybrid bus is the most versatile bus on the market Electric for emission free drive and hybrid where work-horse performance is required.

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On fuel price and tender requirements

In 1987 the Brundtland commission presented its report on defining sustainability.

The conclusions were summarized like this:
“Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs”.

Energy use often have a high impact in life cycle analysis of transports. In particular public transports, that frequently have very high utilization, rely heavily on the choice of energy. So from a plain environmental standpoint the choice would be easy. Low energy use should have very high priority in the design of public transport systems.

However, for many, energy price is equally important. I have studied a large number of bus tenders all around the world and found that surprisingly low emphasis is put on the fuel consumption.

I have divided the principles into four groups:
1: No requirement is put on fuel consumption of the bus and the cost for fuel is subsidized or fuel expenses refunded using an index
2: No requirement is put on fuel consumption of the bus, but the bus operator covers the cost for the fuel
3: The tender has a minimum requirement for fuel consumption to be met
4: Fuel consumption is a competitive part of the tender
I have found no case where the full life cycle cost of the fuel consumption is at stake.

If the true cost for fuel is to be considered the future price would be an important part.
So what would the expected price development for fuel be?

For the study below I have used data from the US Federal Reserve Div. Economic Data.

First we can conclude that the consumer price index historically has not varied much year by year. There has been a constant linear increase year by year. Today the consumer price index increase by ~3% with a linear increase. Even if fuel is a part of the price index it is not “heavy” enough to fully capture the pace of change.

fuel price 1

For fuel it is a completely different story. Historically and fundamentally there have been two major trends: before and after the oil crisis in the 1970s. After the oil crisis the fuel price was very unstable and easily impacted by international crisis development. The risk for a disturbance of the transports in the Hormuz Straits has led to increased prices. Even if the price increase has been mainly instable a fit with an exponential increase seems not too wrong.

If we study the last 14 years the trend is similar but a bit more accentuated.

fuel price2

We can hence conclude that the fuel price index has historically increased by 8% annually.

Consumer Price Index and Fuel Price Index Change from January 2000 to September 2014:

Consumer price index increase yearly linear by 2.5%
Fuel price index has an exponential increase yearly by 8%

How does this help in calculating the Life Cycle Cost for a bus?
If the life time of the bus is 12 years the first tank will start at the index of 100 and after one year the cost will be 108. After 12 years the cost will be 152% higher than today.The average fuel tank during the life time of the bus will cost 65% more than the price today.

Based on the observation that the fuel price has increased by 8% per year since year 2000:

During the full life time of the bus purchased in year 2000 the average fuel tank cost 65% more than the first tank.

Forecasting is always a matter of guessing. In particular instable data, such as the fuel price, is hard. Guessing the future based on the past is mostly better than doing nothing. The best we can do today is use the most precise information we have.
For this study I used US data from the Federal Reserve. For any other part of the world local data may change the picture.

I therefore conclude that: Any city or operator that is concerned about their future cost of fuel the future fuel price should be taken into the equation already when the bus is purchased. It will actually make a hugh difference in technology choice in the favour of lower energy use.

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Volvo Sustainable Mobility Award 2014

The Volvo Sustainable Mobility Award was has already come to its fourth year. The award ceremony was, as all years so far, held in Bangalore India. I had once more the honor to be a member of the jury.
Participation in the award has become a loved tradition among researchers, institutes and many different types of organizations that work for sustainable mobility. The spirit of the award is truly wide and contributions deal with all sorts of sustainability micro level material science to mobility planning from a global perspective.

The award shall encourage and both theoretical progress as well as practical implementation. This years award winner dealt with a wide range of aspects of sustainability: from methodology development, sensitiving government officials, communication to citizens and awareness sharing with media, implementation and follow-up.

The award winners limit their claims to promotion of biking and walking by a new road network. But, I would be prepared to go even further. The rigorous and detailed planning; meter-by-meter has not only enabled safe travel for cyclists (pedal bikes) and walkers. It has improved the safety also for two wheelers (motorcycles) three wheelers and cars as well.

The Centre for Green Mobility Ahmedabad was presented with the Volvo Sustainable Mobility Award in 2014. The team: Mr. Anuj Malhotra, Ms. Arunika Karmakar, Ms. Ruchita Shah, Mr. Prerit Kaji and Mr. Akshan Bhide have taken an idea all the way from the drawing board to the roads of Diu. The on their journey they have step-by-step done what was required to gain trust support and approval from citizens, press and governmental bodies in order to realize a successful implementation. I personally appreciated the wide range of “elements” that were used to achieve exactly the right property at every crossing and every part of the road. It is very far from a one-size-fits-all solution. On the contrary, in some parts the beautiful view of the beach and the sea becomes important to attract the cyclists, in another part the safety for pedestrians to cross the road is in focus. Every part of the road has its own characteristics and needs.

I want to whish the team and the Centre for Green Mobility all success in the continued implementation of the plans for Diu. And, I hope and trust that more parts of Ahmedabad and other cities can learn that benefit from the progress in Diu. This is certainly a project that we all can learn a lot from.

India sustainable mobility award

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Electric Hybrid Launch

In year 1800 Volta discovered the electrochemical cell, the battery. During the first 200 years of battery development many small steps were taken but it was not until recently that Lithium was curbed into a useful combination of metal, ion and electrolyte that allowed a sustainable rechargeable battery.

The energy electrochemical potential is almost 3 volts and the Lithium element is the lightest metal with a mass of 7 grams per mole. This makes Lithium particularly suitable as battery for vehicles.

In 2009 Volvo launched the 7700 Hybrid Bus. It was probably the first vehicle in serial production using the new battery technology. It has become a big success.


The Volvo Hybrid bus range now come in several versions:

7900 Euro VI Hybrid

7900 Euro VI Articulated Hybrid

B5LH (chassis for double decker’s)

B5RLEH (or Euro V Global Hybrid) for international markets

The Hybrid Buses offers superior cost efficiency over the life time in combination with outstanding environmental performance.

The 31st of December 2013 Volvo became the first Bus manufacturer to make hybrid buses the base line for European low floor city buses. This means that the hybrid drive is no longer optional.

Once the hybrid drive is on-board, for buses in city operation it makes sense to charge from the electric grid when you get the opportunity (so called opportunity charging).

In October at IAA, Volvo launched the Volvo 7900 Electric Hybrid. We are immensely proud to once more be first out with a completely new and ground breaking technology. It combines the best of two worlds “it is an electric bus where noise free and clean drive is required and a hybrid bus where performance is demanded”.


The new bus is delivered in a package containing much more than “just” a bus. We already have assignments from a number of cities to deliver complete systems. We are certain that this once more will become a sucess and we are prepared to share a risk. We therefore offer solutions that makes it easy for the users to realize the implementation.

A typical delivery contains:

~20 Electric Hybrid Buses for one or two city bus routes (by availability or rent per km)

~4-6 opportunity charging stations for terminals

20 low power connections to the electric grid for the depot

Service and support for workshop, parts, battery, fleet and vehicle management systems

Zone management for zero emissions or safety

Project support or lead for implementation

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