Hybrid buses are coming to London...

Battery technology may well be advancing in leaps and bounds, but the majority of the rolling stock on the world's roads are traditionally powered vehicles. So what can we do while those vehicles are still in service? One solution could be to go half way - an electric motor that's powered by diesel - in other words, a hybrid. Alex Schey is the CEO and co-founder of Vantage Power - a company retrofitting buses with hybrid diesel engines that dramatically reduce emissions. Charis Lestrange went to hear how...

Alex - From the exterior, nothing is different about this bus. It is a double-decker bus. It's when you get under the skin that things have changed quite substantially. What used to be a big diesel engine and a big gear box, and lots of chunky metal, all of that has been removed and our hybrid power train has been retrofitted into where the engine used to be. So, it is a diesel bus converted to hybrid power.

Charis - Could you explain a bit about what you've done under the hood I suppose?

Alex - If you look in the back of a normal bus, you typically see a big engine, 6.9 to 9 litres for the techies among you, and that's mated to a gear box which in itself weighs about half a ton. And you have a lot of other components around that: cooling packs, auxiliary components, things of that nature. Every single part of that has been removed and by the end of that, you end up with a big, empty engine bay and big discernible features such as engine mounting points. We have a self-contained hybrid so it's fully pre-assembled. The bus gets lifted in the air on some bus lifts and dropped down over the hybrid system and that hybrid system bolts into all the existing engine mounting points and all of the systems in the bus that we don't touch, so pneumatics for your breaking and suspension, hydraulics for your power steering, and alternators for your electrical load.

Charis - One of the main problems with electric vehicles tends to be the batteries that are used, they tend to die as we're driving them and so on. How does this hybrid overcome that problem?

Alex - So, a hybrid typically merges an internal combustion engine, which uses fuel as its energy source, with an electric system of some kind. Our system is what's called a series hybrid system, which essentially is an electric bus. It works much like you might have an electric remote control car. You have a big battery and it feeds an electric motor and off it drives. But that battery is only sufficient to drive the bus for somewhere between 4 and 10 kilometres which is not sufficient for normal use. And this is when we bring in the internal combustion side. Our engine is completely disconnected from the wheels. It can go at any speed even when the bus is stationary or it could be off when the bus is going fast. And that engine just serves to generate electricity to recharge the battery pack. What that allows us to do is it allows us to run the engine at its most efficient point so we can save fuel in that way and improve the emissions. It also allows us to turn off the engine when we're sitting in traffic or moving very slowly. And that means that we're not producing idle emissions. We're not having the engine idling for no reason as you would have in a normal vehicle.

Charis - These buses still need diesel to work then I suppose. Is it much less than what you would use normally?

Alex - Absolutely. So, we are typically taking buses that are between 6 and 12 years old and putting in a hybrid system. We've seen consistently 40 per cent or better improvement in the fuel consumption. Whereas before, this exact bus sitting in front of us driving around London would've been about 4.5 miles to the gallon in terms of fuel consumption, we're regularly seeing better than 8 miles to go which is a massive improvement. Depending on how many miles you do per year that could save the bus operator up to 20,000 pounds worth of fuel per bus per year.

Charis - Are these the future of public transport?

Alex - Hybrid is the future I would say for at least the next 5 to 10 years. We will have increasing numbers of electric buses on the road during that time, but I don't think we can see a large scale proliferation until we have substantial swathes of the city covered by a standard charging infrastructure. And we're not even close to formulating that. Electric vehicles, electric buses are the future. I think the industry is quite united in that fact, but it's a long way off still.