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Volvo plug-in hybrid bus with Bůsbaar rapid charging to begin field testing in Gothenburg; 75-80% reduction in fuel consumption and CO2

7900 Volvo Plugin Hybrid Charging at Redbergsplatsen in Gothenburg. Click to enlarge.

Volvo Buses’ new plug-in hybrid buses will begin field tests in Gothenburg, Sweden this month. Volvo Buses has already sold more than 1,000 of its conventional hybrid units; the plug-in version will facilitate the reduction of fuel consumption and carbon dioxide by 75 to 80%, compared with current diesel buses, the company said.

The plug-in hybrids are based on the Volvo 7900 Hybrid, Volvo Buses’ second series-produced hybrid bus model. The plug-in hybrids have been further developed, and enable rapid recharging from electricity grids via the Opbrid Bůsbaar pantograph on the roof (earlier post).

Volvo’s I-SAM conventional parallel-hybrid system for buses. The plug-in adds a larger battery pack, charging electronics and control module. Click to enlarge.

An electronic control module regulates engagement and disengagement of electric and diesel power, as well as gear-changing modes and recharging of the Li-ion battery. The close-ratio Volvo I-Shift automated transmission has software that is optimized for city and commuter traffic.

The 4-cylinder, 5-liter Volvo D5F diesel engine produces 215 bhp and is installed vertically in the left rear corner. The conventional hybrid offers up to 37% fuel savings compared to a diesel version and 40-50% lower exhaust emissions.

The plug-in versions have a larger battery pack, making it possible to drive up to 7 km using electricity only—about 70% of the route distance. The batteries are charged at the bus terminus via the Bůsbaar for between six and ten minutes.

The purpose of the field test is to study and verify the anticipated reductions in energy consumption and emissions, as well as to compile information from drivers, passengers and surrounding residents about their views on the properties of the bus.

Volvo Buses expect to be able to reduce emissions of carbon dioxide by up to 90% by using biodiesel instead of standard, fossil diesel oil in the combustion engine.

Volvo Buses expects to commence commercial manufacturing of plug-in hybrids in a couple of years, and the technology is now to be tested in the three buses that will be put into service in Gothenburg. A demonstration project has also been planned for 2014 involving eight plug-in hybrids in Stockholm.

In recent years, sales of Volvo Buses’ hybrid buses have tripled for each year and we believe the market for electromobility will continue to expand rapidly. Accordingly, the Volvo Group is investing in this area, making it possible for cities to realize their visions of more eco-friendly and attractive transportation.

—Håkan Karlsson, President of Volvo Bus Corporation



Volvo is actively working on HEV, PHEV and BEV buses to suit the needs of demanding customers worldwide.

The HEV version is already selling over 1000 units and expanding.

The PHEV version, with its higher efficiency, should sell even better by 2015/2016.

The BEV version will also be road tested soon and should be available for normal service by 2017/2018 in many cities. It will compete with BYD's and others.


"7 km using electricity only—about 70% of the route distance"

Is that a typical route distance for a city bus in Europe? 7 km isn't much in North American urban sprawl.


Our very wide spread North American city operates 1773 buses on 219 different routes. The average route length is only 8.4 KM but the longest route (No. 356) is 74.1 KM.

Many short bus routes bring passengers to the nearest subway station and/or in the city core.

I agree with you that 7 km is not enough for all routes but may be enough to run on electricity for close to 50% of all current bus routes. For the other 50% you would need more batteries or run on the ICE or FC range extender.


Even six minutes recharge time at the end of a run seems like a long delay to me.  Maybe these buses should be using flywheels instead of batteries, to get the power up and recharge time down.  I'd love to see substantial recharges in a single stop, say 20% in the time it takes to pick up or drop off a couple of passengers.


With current low performance batteries, a few extra short charges, at major regular bus stops (every 2 Km or so) would help, specially on longer routes.

Some 300 sq.ft. of roof top mounted high efficiency solar panels could help to supply energy for e-ancillaries.

Our drivers take a 10 minutes coffee & donut rest-break at the end of their route. Charging would take place at the same time?

Eventually, e-range will multiply with improved future batteries.

Thomas Pedersen


The poor bus driver need a break (and perhaps to go to the bathroom) every now and then. Bus driving is a lot more demanding than car and truck driving, I think. To operate a slow vehicle with many stops, and standing passengers inside, requires a lot of anticipation and thus mental resources.

The end-of-route break is also slack in the route planing that can be used to catch up in case of delays. So it is important that the hybrid bus can operate without the charge!


City bus e-range will improve, every year or so, either with more batteries or higher performance storage units. The on board range extender will get less and less usage and will be progressively reduced in size.

Who knows, in another 10 years or so, the on board range extender may become an 'emergency' mini (20 Kw or so) power unit to operate the on board HVAC and other e-ancillaries during main batteries failure.


Very moderate battery pack. It is 2 times smaller than Volvo V60 or 3 fold smaller than Chevy Volt's. I just curious what is preventing make it little bigger and sutable for bus not compact car.

Roger Pham

I believe that the battery pack is primarily sized to provide the power to the E-motor for adequate braking energy recuperation. A bus has far more energy to recuperate during braking than a car. The plugged-in capacity is a secondary advantage only, but since the CO2 reduction is 75-80% c/w a diesel bus, who can complain? This is incredible performance for a small-size battery pack that will allow more buses to be thus equipped without straining the battery supply.

The Volve Flywheel KERS technology is also great for this application. Even better is a bi-hybrid design using a flywheel with imbedded permanent magnets and the casing with stator coils to replace the E-motor. Thus, energy for acceleration and from braking will go directly from and to the flywheel. The flywheel can be upsized to deliver 200-300 kW instead of the 120 kW size of the E-motor, hence significantly improve acceleration and regenerative braking performance. The battery pack can be smaller and will last a lot longer due to less frequent use. The cost saving of not having a 120-kW E-motor and a smaller battery pack with less frequent replacement will apply toward the cost of the flywheel unit, and thus the bi-hybrid can be cost-neutral c/w current PHEV design, while having higher performance.

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