Towards electromobility Gothenburg’s plug-in hybrid experience and beyond
Battery contracts
Per Bengtsson, Technical Project Manager
Battery life is a major concern for operators considering going down the electric hybrid, plug-in or full electric route and Volvo has answered this and provided predictability by offering battery contracts with performance assurance at a fixed monthly cost based on geographical area, topography, road conditions and operating cycle. Each battery is looked after by the control software which handles current control, the optimisation of power output, cell management and temperature control. In addition, each cell is remotely monitored continuously using Volvo’s fleet management system and should any need replacing, they will be replaced. Per Bengtsson, Project Manager for the field test at Volvo Buses, told me that battery life had been calculated on the basis of six years.
Explaining more about the batteries used, he said ’One of the goals was that we should increase usable energy from the battery by 500%. To achieve that we put in more batteries, double the battery weight, and used a different kind of cell technology with a longer window of usable energy. The output is roughly 8kW/h compared with the 1-2kW/h of the original hybrids.’
Results
Asked how the buses had performed so far, Per said that the buses had run surprisingly well. One issue that had been highlighted was the need to keep the batteries warm, necessitating heating them at night to ensure performance. They need to be at at least 20-degrees to deliver their full performance, a higher temperature than required by the units on a standard Euro5 hybrid. If the batteries are cold they will not work at all so they are kept heated at the depot overnight using a 230V system. Per found it ’a bit frustrating’ that with all the new elements of the project there should be problems with something so straightforward, but added, ’with new batteries and a new charging system we expected some problems.’
Before the trials began, Volvo had talked in terms of hoping to achieve a 65% fuel saving compared with a Euro5 bus. In practice, this has been exceeded. In a press release issued by Volvo, Johan Hellsing, former Project Manager for the field test at Volvo Buses, commented, ‘Our performance results are even slightly better than we had anticipated. The plug-in hybrid consumes less than 11 litres of fuel for every 100 kilometres. That’s 81% less fuel than the equivalent diesel bus consumes.’ Eleven litres per 100km, equates to 25.68mpg! The bus against which comparisons are made is a Euro5 powered Volvo B9L.
It also found that the figures for overall energy consumption, including both diesel and electricity, exceeded the target they had aimed for, achieving a 61% energy saving compared to an equivalent Euro5 diesel bus.
Electricity provides up to 70 per cent of the power required along the route.
Not only are the consumption figures good, the noise emission levels that are a key element for the region are also impressive. Volvo claims that in electric mode noise reduction from the plug-in hybrids is around 20 dBA.
There have been some small issues with the charging system, most of them ones attributed to the hardware working in a vehicle environment. There has also been an issue with earthing for the charger communications system which now has a four point connector. This did impact on vehicle availability during November and early December.
On the road
Internally the Plug-In hybrids look just like any other Swedish bus. The seats are blue, the handrails are yellow and everything else is light grey. There is a rack containing leaflets mounted on the offside front wheelarch and it was surprising how many people took one, referred to it and then put it back, a sign of a country that takes recycling and eco objectives seriously. Ironically, when in electric mode, the vibration of the leaflet rack was often the loudest noise you could hear on the bus.
I was impressed with the performance in electric mode, it is exceptionally quiet. I was told that up to 70% of the journey is made in electric mode but it felt like over 80%, with the diesel only cutting in on hills. In diesel mode there is still quite considerable vibration from the Euro5 engine, something that Volvo have worked hard on and massively improved with the Euro6 package, so should not be an issue on future Plug-In hybrids. It should be pointed out that the hills encountered are very steep ones.
The three Plug-In hybrids are all named. This one is Elena
An advantage of the design is that the maintenance required is less than a standard diesel, and with so much of the operation in electric mode Per said it had the potential to be considerably less.
Reactions
GS Buss driver, Christer Ryden, thinks the buses are ’fantastic’
Perhaps the most telling endorsement of the plug-in hybrids came from three of the driving team, enountered at the Redbergsplatsen terminus. Christer Rydén has been driving buses since 1985 and thinks the vehicles are ’fantastic’. Speaking to me while the vehicle recharged he said, ’I like it very much, it’s the silence. It’s more fun to drive than other buses because it is so quiet. There’s not anything you have to worry about with it’.
His colleague, Johan Strom, completely agreed. ’At the risk of sounding like I’m working for Volvo, which I don’t. It’s amazing, it’s fantastic.’ Explaining why, he said that compared with the Euro5 7900H hybrids, ’it is so much improved. It is quieter, there’s no shake and the gearbox doesn’t jump about and smash the gears in at times. I really like it.’
Dag Almroth was equally enthusiastic, saying, ’It’s nice and quiet. You don’t have all the vibrations. It’s quite comfortable and the environment is very nice. I reckon we use electricity 75-80% of the time, the diesel only comes in when going up hill. It’s quite a step forward from the hybrid. I enjoy it immensely and I’d like to keep driving them.’
Christer added that, ’passengers love it too. It depends when you are driving whether people comment, but off peak a lot of people mention it. I think my colleagues like it very much too.’ The only fault he could mention was that there was sometimes a charging problem with a poor contact because sometimes the charger arm did not come down as it should. He said it was also more difficult to charge when it was raining a lot. ’They are working in it to find a solution,’ he added.
After our conversations I took a short ride in service on one bus and another over the full length of the 60 route and saw at first hand that the bus only utilises diesel power when climbing steep hills. The whole of the central section of the route was covered in electric mode, when the bus is extremely quiet, the loudest noise on one of them being the rattle of a brochure rack. When the diesel cuts in and out it does so very smoothly, though as the vibration damping from the engine in the Euro5 7900H is disappointing you do still get noise and vibration through the rear seats when in diesel mode. I anticipate that this will not be the case with the Euro6 version because attention to the engine mounting system has resolved the issue.
Further feedback came from a passenger survey carried out by two Volvo interns on both the hyrbids and plug in hybrids operating on the 60 in early July 2013. This found that of 54 urban travellers, 69% considered the plug-in buses to be quieter than conventional buses. No traveller considered the plug-ins to be louder though 9% of 166 hybrid travellers had thought they were noisier and 36% that they were quieter. The overall opinion about both the hybrid and plug-in hybrid buses was positive.
A further and much more detailed passenger and driver survey is to be carried out by Västtrafik this spring. It will also cover people living on the route.
Next steps
At the end of the Hyper Bus project in July 2014 the three plug-in hybrids will be converted to Euro5 hybrids and sold for further use as future Volvo development will be based on Euro6 buses. I was unable to ascertain what will happen to the two charging stations.
In 2014 a batch of seven or eight plug in hybrids based on the Euro6 platform will go into service in Stockholm on a route that has yet to be finalised. Unlike Gothenburg, where the buses were additional on a route, in Stockholm they will provide the full service. They will also run on 100% biodiesel, whereas in Gothenburg they use 7% biodiesel. Their batteries will have the same energy content as the Gothenburg buses. These will be B-Status buses, meaning that they will be the first examples built in series production, though will still be prototypes. Full commercial production should commence towards the end of 2015. I was told that it was too early to say what the cost premium over a hybrid would be.
In the Hyper project, Volvo has not chosen to control in which areas of the route the buses run in electric mode (geofencing), it simply brings in the diesel engine when the electrical system needs assistance. In practice, the diesel cuts in when the incline reaches between 4-5%. I was told that the electrical system would be able to handle inclines but it would use a lot of energy and limit the vehicle’s range. More control of this aspect would be an advantage on a longer route and this will be incorporated on the Stockholm test buses.
ElectriCity
Johan Larsson, Product Manager Electromobility at Volvo Bus
Johan Larsson is Product Manager Electromobility at Volvo Bus and has been working on electromobility projects for the past five years. He explained that Volvo and Gothenburg share a common vision of creating a city and a region that is creative and forward thinking in matters of sustainable mobility that will attract investment, competence and companies in the field to locate there. They plan to create an arena for testing new public transport products and services that will be a source of inspiration and motivation for future urban development and the home of a world class automotive industry.
The terminus at Masthugget showing the charging station and bus stop during the recharging procedure
During 2015, Volvo Bus plans to have its first full electric bus with no diesel engine running in service. This vehicle along with Euro6 based plug-in hybrids will operate on a new service between the Johanneberg Science Park and the Lindholmen Science Park in Gothenburg as the demonstration aspect of a new initiative between AB Volvo, Region Vastra Gotaland, the City of Gothenburg, the Swedish Energy Agency and the two Science Parks called ElectriCity. The twin aims of this scheme are: firstly to create an innovative electrified bus system that forms part of the public transport system in the City of Gothenburg in order to develop and test new services and products that contribute to a more attractive public transport system and, secondly, to develop, through the ElectriCity partnership, working methods for demonstration projects between public and private parties, and to introduce new business models for sustainable mobility in the city that can be scaled up outside the demonstration arena.
As well as advanced buses, the scheme would see new bus stop solutions, intelligent transport solutions, new safety concepts, new energy solutions and possibly a green depot.
Both plug-in hybrids and electric buses will operate on the route, which will take in the city centre and part of the BRT lanes to the north of the city on which the bi-articulated Volvo buses currently operate, sharing the same recharging infrastructure. Johan said that the electrics would not need longer to charge but they would need more power – up to 300kW. They will have a more limited range compared with the diesel equipped buses and because of this their use would need careful traffic planning.
Johan believes the benefits of developing buses that create less or no noise and less or zero tailpipe emissions is that they can be integrated more closely with people and their environments. Buses with such high levels of environmental acceptability would enable a city to be more dense, with buses running closer to where we live and work. For instance, it will be possible to have indoor bus stops. He said this would be an advantage when it was particularly hot or cold, rainy or snowy.
ElectriCity was launched on 17 June in Gothenburg with one of the plug-in hybrids in ElectriCity livery inside the vast Nordstan Shopping Mall, in order to stress the kind of close relationship between public transport and its users that the project is striving to encourage.
He did not see fully electric buses becoming the only option that would produce; he believed that the future would see a mix of propulsion types including electric, hybrid, plug–in hybrid.
Summing up, he saw the ElectriCity project as ’a visionary partnership that brings us close to the goal of sustainable public transport and profiles a progressive city’.
Last word
The bus system I saw was very impressive, as are Volvo’s future plans and one imagines there are many cities that will aspire to be part of such a step forward in the way that buses could interact with passengers. Given Volvo’s long standing relationship with UK bus operators and the high take up of the company’s hybrid technology it would be surprising if some of them are not in the UK.
I would like to thank everyone involved in the project for their assistance, especially Hanna Bjork and Roger Vahnberg of Vasttrafik; Per Bengtsson, Johan Larsson, Marie Carlsson and Helena Lind of Volvo Bus; and Dan Paulström along with the driving team at GS Buss.