Are electric vehicles really best option for greener driving?
Jaguar Land Rover has become the latest car manufacturer to announce its entry into the world's first fully electric racing series – the FIA Formula E World Championship. It is reported that the racing series will serve as a platform for the development of an electric-powered road car – perhaps an SUV to rival Tesla's Model X.
As the nations of the world pledge action on climate change, the automotive industry will face renewed pressure to come up with alternative energy solutions. Consumer demand for passenger cars which reduce harmful emissions without sacrificing performance will be on the rise – more so in the wake of the VW scandal.
Against this backdrop, the potential of both hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) certainly needs to be considered. But they are not our only clean energy alternative.
The electric options
The internal combustion engines of both petrol and diesel-fuelled cars can be hybridised by adding electric components – such as motor-generators – together with a small amount of energy storage. Hybridisation offers an excellent opportunity to optimise the way we use the internal combustion engine. It enables the engine to operate at a higher average level of efficiency, and gives cars a way to recover the kinetic energy produced by braking, which is otherwise wasted.
It's reasonable to expect that a majority of vehicles will be hybridised to some extent in the not-so-distant future, since these small modifications can yield big returns in terms of energy use.
The BEV is a much more challenging proposition as it requires large, expensive, resource-intensive batteries to deliver the kind of power that drivers expect. By contrast, combustion-powered cars are affordable because they are built from cheap materials using cost-effective processes and have a very inexpensive energy storage system – a liquid fuel tank. As a result, the extra costs associated with BEVs will be a major turn off for manufacturers.
What's more, BEVs only offer a marginal reduction with regard to in-use and life-cycle CO₂ emissions, compared with their combustion-powered competitors. This is because – in Europe at least – almost half of our electricity is generated by burning fossil fuels. Of course, we'll need to re-evaluate this assessment as our electrical grids become less carbon intensive. And one of the best arguments for EVs is that they help us to develop our infrastructure and technology, in anticipation of a time when renewable electricity becomes commonplace.
Even so, there are a number of competing technologies in the passenger car space – and it's critical that we research all possible routes to clean, sustainable transport.
Electrofuels – which are fuels manufactured using renewable electricity – offer one plausible alternative to BEVs and HEVs. The idea of using hydrogen gas (H₂) made with renewable electricity to power cars has been around for a long time. The attraction is that releasing energy from H₂ produces only water as a by-product, making it a very clean fuel. But unfortunately, it presents some serious challenges around distribution and storage.
It's currently thought that H₂ will have to be stored at a very high pressure to get a reasonable amount of energy on board a vehicle – and even then, its density is only comparable to styrofoam. To be sure that H₂ storage tanks are crash- and fire-proof, they have to be extremely thick, carefully-made composite structures. For comparison: to contain the same amount of energy as a 10 US gallon liquid fuel tank, a hydrogen storage tank would have to weigh about 170kg to 180kg. This inevitably drives up costs, and that's not even considering the problem that H₂ – being the smallest molecule – has a tendency to leak out of tanks and storage systems, and can cause steels to become brittle.
Arguably, a more exciting and practical alternative is to use this technique in power plants. The H₂ generated using renewable energy can then be combined with waste CO₂, in order to synthesise methane. The methane is then injected into the national gas grid, to be used by compressed natural gas (CNG) powered cars.
The ultimate goal for this approach is to use CO₂ extracted from the atmosphere. If this can be done, the approach would yield a truly renewable fuel which takes out as much carbon from the atmosphere as it puts in. This process points the way to a sustainable future which retains the low-cost, high-utility internal combustion engine.
Futuristic, but affordable
It is also possible to produce liquid fuels in a similar way, by using H₂ and CO₂ to synthesise methanol – an alcohol related to methane, which is the simplest liquid energy carrier. While liquid fuels take more energy to produce, they also tend to have a higher energy density than most gas fuels.
Importantly, methanol can also be blended with gasoline and ethanol, and synthesised into pure hydrocarbon fuels, which can act as substitutes for gasoline, diesel and kerosene. Creating these types of high energy density fuels will be the only practical way to decarbonise aviation, for instance. What's more, methanol can also be made into plastics and other petrochemicals, allowing many different industries to harness excess CO₂.
There's one sticking point, though: currently, the extraction of CO₂ from the atmosphere on an industrial scale remains a futuristic goal. Still, it is a known, practical process which would enable the mass use of renewable energy in some of the poorest nations on earth, while providing a supply of liquid energy to meet the world's transportation requirements. It also permits mass uptake of wind and solar power within existing economies, since fuel production provides a means of converting and storing renewable energy, which the electricity grid currently lacks.
At the present time, it makes more sense to use renewable electricity in fixed applications which do not need storage batteries and to reserve fossil fuels for mobile applications, where their energy density is of most use. Because electrofuels can be blended with the fossil fuels we already use, they don't require us to radically change our energy infrastructure and they don't decrease utility for drivers.
Both approaches need funding, but electrofuels represent the minimum change to the status quo. They will also require no investment in infrastructure from governments, while yielding the same amount of tax revenue. For all these reasons, electrofuels seem a much more probable route to cleaner driving than BEVs.
This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives).