Electric buses - ideal for our cities

BYD K9 electric bus in London

The Bangalore Metropolitan Transport Corporation has recently started trial runs of Electric Buses for its vast public transportation network. Electric Buses are slowly gaining acceptance and have been adopted in few cities around the world. The most popular of these buses is the E9 – manufactured by BYD – a popular Hong Kong based battery and automobile company. Electric buses are commercially in use at various places in China. They are in trial at Utah, Chile, London, South Korea.

The batteries that BYD uses are Lithium Iron Phosphate, developed in-house. These give a range of 250km per charge, which is quite respectable for a day’s intra-city route. They can be charged in 6 hours at normal rate and 3 hours for a quick charge. Ideally electric city buses can be fully charged overnight or given short bursts of high speed charging during terminal stops. Another possibility is wireless induction charging. Read more about that here. It consumes 100 kWh in an hour and that translates to just Rs.4 per km, as compared to Rs.20 per km in diesel buses. The battery is expected to last 6000 recharging cycles or 1.5 million kms, thereby capable of saving nearly a crore of rupees before a battery swap. This is considering the fact that there are hardly any maintenance costs in electric vehicles. Unlike petroleum operated vehicles, they do not have filters, oil changes, turbochargers, etc. These expenses are a lot in heavy vehicles like buses, and the time taken to service also accounts for revenue loss. In fact there is only one moving part in the electric motor.   

Electric buses are an ideal choice for cities with dense traffic and otherwise too. They are very silent. A V8 roar may be appreciable in a sports car, but an old bus noisily accelerating and blowing soot on your face is never charming.  Apart from that, electric buses have regenerative braking. This is a technology that helps vehicles recover the kinetic energy of motion that is otherwise lost during braking. What happens is when the foot is left off the accelerator, the motor acts in reverse as a generator using the motion to top up the excess energy into the batteries. This also reduces the need of brakes in predictable situations (Bus routes = more predictable), thereby elongating the life of brake pads and shoes by a huge margin. This technique is very useful in stop-start situations which are very high in dense city traffic. Going downhill, a Mahindra Reva e2o (an electric car from India) has been able to recover 20% more range on the return journey on a particular trip to hilly region.  

Then there is the usual electric advantage of not wasting fuel at traffic stops – they use energy when the accelerator is pressed. Hence there is no wastage of energy like internal combustion engines which have to kept on during idling and consume fuel in that process. This is particularly beneficial in dense cities and typically for buses as they stop for loading and unloading of people. This frequent dis-acceleration also helps in regenerative braking. Also electric motors produce 100% torque at 0 rpm. This high torque nature is more suited to heavy vehicles like buses and trucks.

With rising costs of polluting petroleum, the operating cost difference will widen further for sure. Electric buses at present scenario are able to recover the initial investment fast too. A proper charging infrastructure is highly necessary. The grid needs to get greener. Dirty coal needs to be replaced with renewable sources like hydro, solar and wind energies. Karnataka produces a fair share of green electricity. These low floored, air conditioned electric buses will go head-on with the red Volvo city buses and are expected to be even more comfortable than them. They will also make the Bangalore air more breathable. We hope this model is a success and it is replicated in more cities throughout the country.