Lexus: The hybrid debate blog

If the UK’s vehicle fleet continues to develop on the same trajectory then, within a few dozen years, hybrid cars will likely outnumber conventional petrol and diesel cars. But what energy environment will they inhabit?

We know from the Intergovernmental Panel on Climate Change (IPCC) that we have to control carbon dioxide to less than 450 parts per million if global warming is not to become unstoppable. But is this really the balanced view of the scientific community or a lowest-common-denominator consensus that 99.9% can support, designed to be bullet-proof in the face of attacks from those with vested interests in the oil economy?

If the real situation is more serious - and many scientists believe that it is - then Britain should be aiming for a cut in emissions of not just 60% but up to 80%. Having lulled ourselves into a false sense of security, we will be forced to ration carbon, and probably on an individual basis. It is easy to imagine a situation in which our national identity cards will store information about our carbon consumption, and will need to be presented whenever we buy fuel, board a plane or pay our electricity bill. Once our annual carbon quota is exhausted, so will be our ability to travel, other than at ruinous cost, linked to our ability to pay fines.

In this energy-scarce future, luxury sports utility vehicles with three-litre engines will exist only in museums, alongside video clips of Jeremy Clarkson. Cars will now be used mainly for trips between city suburbs and smaller towns, where mass-transit lines or electric tramways do not reach. Long commutes into town from converted barns in the countryside will be distant memories as people are forced to work locally and to network electronically, rather than face-to-face.

Moreover, hybrid cars will be different to those in use today. Instead of the electric drive being a load-levelling device for a petrol engine, hybrids will basically be electric vehicles - charged at night from a wall socket - with a small internal-combustion engine for longer trips. Performance will not be important as few speed limits will exceed 60 km/h and, for longer trips, people will use lightweight, high-capacity electric trains supplied by a new generation of nuclear power stations. Moreover, these next-generation hybrids will not need the same heavy structures as their predecessors, because they will have active accident-prevention systems and will not share 130km/h motorways with 44-tonne goods vehicles. They will have the potential to be lighter and more airy than the cars of today.

At the same time, the mass-proliferation of hybrids will create unprecedented problems. Today’s conventional power-trains provide many kilowatts of heating and defrosting power on cold, wet days, by using the waste heat produced by their petrol or diesel engines. The electric drive systems used by the hybrids of tomorrow in urban environments will have an efficiency of 90%, compared with less than 25% for a petrol engine in a similar duty cycle, so there will no longer be enough waste heat to maintain cars at "shirt sleeve" temperatures in winter.

Having said this, in the new, low-energy economy, where awareness of sustainability of issues will be greater, there will be a cultural shift towards dressing appropriately for the weather - sweaters in winter, shorts in summer. It will no longer be affordable to modify the local environment to match a particular sense of fashion.