As the UK's recent panic buying of petrol at the first hint of a short term fuel shortage showed, we are still very reliant on the supply of gasoline for almost all our transport needs. So what does this tell us about the longer term when the access to gasoline from fossil sources will become increasingly restricted, with the accompanying increases in costs, and challenges to our security of fuel supply? How will demand for transport evolve in the future, and what can we do to kick our addiction to gasoline?
Well, unfortunately, the first thing to say is that the number of vehicles will only increase over the coming years. Today the global road transport fleet stands at around 1 billion vehicles. By 2030 it is forecast to grow to 1.6 billion vehicles (BP World Energy Outlook 2012), almost all of that growth coming in the rapidly developing economies such as China, India, and Brazil. This will place growing pressure on global gasoline supplies.
Secondly, pressures related to the environmental emissions associated with road transport, be that carbon dioxide, oxides of nitrogen, or particulates, are only likely to increase, as they are associated with issues such a local air quality in our cities, and concerns over climate change.
Against this backcloth, manufacturers will continue to improve the fuel efficiency of current vehicles, both by reducing weight, but also by increasing levels of hybridization of internal combustion engines with batteries. This will undoubtedly help improve fuel economy, but in itself will not be sufficient to deliver us a secure and sufficiently low carbon transport system in the longer term. In the UK for example we need to be operating at an average vehicle road transport fleet emissions of some 20 – 30 g CO2/km by 2050, if road transport is to take its share in enabling the UK to meet its commitment of an 80 % cut in CO2 emissions by 2050. This can be compared to a fleet average of some 160 g CO2/km for new vehicles sold in the UK today, and a required EU fleet average target of 95 g CO2/km by 2020 – a target which will mostly be met by increasing sales of hybrid petrol and diesel fuelled vehicles.
So what are the fuel and drive train options in a future with more expensive and scarce fossil reserves, and one where we wish to significantly lower our carbon emissions? Well, one option is to move to bio-fuels, and it is clear that bio-resources will play an ever important role as a valuable source of carbon in a fossil constrained world. But it is also clear that we will need to use these bio-resources for the production of chemicals and polymers, and other carbon rich materials. So it may well not be the best use of these scarce resources to burn them in engines in our cars and other light duty vehicles such as vans – rather using them as energy dense fuels for long distance transport – such as long haul trucks, and air transport.
So that leaves us with two choices for our cars, vans, and other light duty road vehicles, both based around electric drive trains. One is the use of hydrogen fuel cell electric vehicles, the other battery based electric vehicles. The good news here is that both these options take advantage of the greater efficiency of electric drive trains compared to internal combustion engines, typically 3 to 4 times more efficient in real world driving conditions. The challenge of course relates to delivering vehicles that meet customer requirements in terms of price, reliability and range. And putting in place the electric charging and/or hydrogen fuelling infrastructures needed to realize the potential benefits of these technologies.
Manufacturers are bringing out increasing numbers of battery electric vehicles (such as the Nissan Leaf) and plug in hybrid vehicles (such as the Vauxhall Ampera) which can run on electricity. But operating in the UK on today's electricity mix, these cars have emissions of around 70 – 80 g CO2/km, not much better than a modern gasoline based hybrid such as the Toyota Prius, and well above our longer term targets. But this is because today, UK electricity is not that clean – indeed per kWh its carbon content is twice that of diesel! The same cars driven today in France, with its reliance on nuclear electricity, would have carbon emissions of less than 20 g CO2/km – in other words they would meet the UK's 2050 target for low carbon transport. This is because French electricity has a much lower carbon content that the UK equivalent. So, as the UK continues to decarbonize its electricity supply through increasing levels of renewable and/or nuclear generation, then the environmental benefits of electric vehicles will clearly increase.
The same debate of course applies to hydrogen fuelled vehicles. Today we make hydrogen from natural gas – when this hydrogen is used as a fuel in a typical fuel cell electric road car then carbon emissions are around 70 – 80 g CO2/km, similar to a UK electric vehicle today. This tells us that we need to pay attention to producing hydrogen from low carbon sources – for example from renewable electricity, from nuclear energy, and/or as part of carbon capture and storage schemes, where hydrogen is often produced as an intermediate step.
So it is clear that road transport technologies are increasingly becoming available that will allow us to break our petrol pump habit. Certainly drivers of battery electric vehicles will have the right to remain smug when the next petrol shortage hits. As will drivers of the new hydrogen fuel cell vehicles promised for commercial launch in 2015 by major manufacturers such as Toyota and Daimler. It is simply a matter of when, rather than if, we will be buying and driving battery electric and fuel cell electric cars.