Electric Buses

Electric buses can be classified as follows:

  • Trolleybus powered by overhead powerlines
  • Wireless, from an underground power line by induction, over a gap.
  • Online Electric Vehicle (OLEV)  propelled by an underground high frequency cable 
  • Battery powered bus
  • Capabus with electricity stored in a capacitor
  • Gyrobus has a battery and a gyroscope

Trolleybus

Power comes from two overhead lines with 600 V DC. The bus connects to these through two spring loaded poles.

An electric tram uses the steel rails as a return, but a rubber tired bus on a road cannot do this.

Are several advantages, electric motors are better than diesel or starting and hill climbing. They produce less pollution. Rubber tyres grip the road better than steel wheels on steel rails.

They are used where there are not enough passengers to justify the expense of building  tram tracks.

Trolleybuses are cheaper than trams.  Since they operate on rubber tyres, they are quieter.  They’re safer too, able to brake much more quickly in an emergency and steer around stray pedestrians. They carry a battery for when not connected to the grid.

In any public transportation system, reliability is very important.  When an entire city depends upon that system, reliability is absolutely crucial.  And it is here where the trolleybus really scores over the tram.  If equipped with an auxiliary battery, the bus is free to leave the overhead lines to circumvent obstacles, whether they be broken-down vehicles or road works.  Trams just can’t do this, and any such problems would have a large impact on service.

With medium sized cities the higher capacity of trams makes them more or less essential, but the best choice for small cities is the trolleybus.

Harvey D.Dibble's patented trolley bus of 1889 Source

Induction powered

Power can come across a gap from an underground powerline. It is transferred by electomagnetic induction, as it is in a transformer. This means the bus can have a battery only 20% of the normal size, or a capacitor. Also only 20% of the bus route needs to be supplied with underground power, Normally acceleration areas, hills, crossroads, bus stops, and parking areas. The gap between the power receiver on the bus, and the road is 20 cm. Efficiency is 75%. This system was first patented by Tesla and developed by a Korean company KAIST as OLEV (OnLine Electric Vehicle).

Britain is testing the system.

The tracks could supply all the electric cars on the road. However will be very expensive.

Promotion video

Battery buses

A bus with a 500 kWh battery can drive about 400 KM and with a one hour charge about 350 KM. So they can be charged at bus stops and keep going all day. Using induction from under the road they can charge at 100-200 kW. The battery is around 500 kWh.

In Los Angeles they are trying to make it possible to hook all the buses up to the grid so they can act as a huge emergency power supply to run the city. BYD buses

Wireless charging at a bus stop

Rapid charging batteries

In Geneva, Switzerland, the TOSA (Trolleybus Optimisation Système Alimentation) pilot project is testing electric buses with an unusual method for keeping charged up. The articulated bus has a battery pack on top of the vehicle. When it pulls into certain stations, it connects through a robotic arm to what is essentially an electric bus dock. A 15-second rapid flash charge at each stop keeps the buses running all day.

Capacitor bus - Capabus

Capacitors can only hold about 20% of the energy of a lithium battery, but they can be charged far faster. So a bus with a capacitor (super or ultracapacitor) can power the bus about 5 KM, and charge quickly at every few bus stops.

Fast charger: The buses can only travel three to 8 KM between charges, but the ultracapacitors allow for fast recharging at designated bus stops.  Wikipedia

buses use 40 percent less electricity compared to an electric trolley bus, mainly because they’re lighter and have the regenerative braking benefits. They’re also competitive with conventional buses based on fuel savings over the vehicle’s 12-year life, based on current oil and electricity prices. Sinautec estimates that one of its buses has one-tenth the energy cost of a diesel bus and can achieve lifetime fuel savings of $200,000.

“The ultracapacitor bus is 40% cheaper than lithium-ion battery buses, with a far superior reliability rating." Source

 A bus that runs entirely on ultracapacitors charges up at a bus stop in Shanghai.  

Video

Flywheel bus - Gyrobus

in the 1950s the Swiss developed flywheel buses, called gyrobuses.

They used a flywheel to store energy as batteries were not up to the job.

At stops along the route, the bu connected to overhead wires, and the 70 HP electric motor spun the 5 ft flywheel up to 3,000 RPM. When acceleration was required the flywheel became a generator that ran the motor. Braking was regenerative so it sped up the flywheel and recycled the energy.

The flywheel had enough energy to power the bus for 6 KM at 50-60 KM/h.

This big flywheel was mounted horizontally in the middle of the bus, and the spinning gyro effects made handling quite different. It did give a nice, level ride.

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 Wikimedia