Chemical Guide

Electric cars are making steady progress as the transportation method of the future with auto manufacturers continuing to announce new concepts and production vehicles. However, doubts remain about the sheer scale of investment that would be required to make electric cars a mainstream success – with battery prices needing to fall, fears over range needing to be addressed, and a completely new charging infrastructure needing to be introduced.

With that in mind, many critics still hope that an alternative to petroleum can be found that will allow us to continue to fuel our vehicles in the traditional manner. Though ethanol has emerged as an alternative due to its energy density and ease of handling, a recent white paper by Leslie Bromberg of MIT’s Plasma Science and Fusion Centre and Wai K Cheng of the Sloan Automotive Laboratory suggests methanol has been overlooked as a viable alternative fuelling method for transportation.

Why methanol could be a success

Methanol has yet to emerge as a major transportation fuel despite the fact that it is regularly used for large industrial scale projects. Large scale production from natural gas and coal is well-developed and has a track record for being economical, particularly when using thermo-chemical processes.

There are many attributes that make methanol attractive for use in transportation. For example, it is a liquid fuel that can be easily blended with petrol and ethanol and used in existing vehicle technology with minimum additional cost.

As a high octane fuel it has the combustion characteristics that allow engines specifically designed for methanol fuel to offer the same efficiencies as the leading diesel engines while matching them for environmental performance. It is also comparatively safe as it biodegrades quickly and its toxicity is comparable to petroleum.

Above all however, methanol is a much greener option than petrol when it is produced from renewable biomass. In the meantime, an option is to use methanol that is derived from natural gas as its carbon dioxide intensity would be no worse than that of conventional fuels and greenhouse gas emission reductions may be achieved during the methanol generation process. According to Bromberg and Cheng, methanol could be created from natural gas in a straightforward manner so that large scale domestic production, infrastructure and vehicle use could be developed – this system could then be transitioned to renewable methanol.

How methanol could be used in modern day vehicles

Studies suggest that vehicles that run on 85 per cent methanol blends, as well as petrol, actually have performance capabilities that equal or surpass vehicles running on petrol alone.

However, in their report, Bromberg and Cheng suggest that more can be done to optimise the combustion processes of methanol, which they describe as ‘excellent’.

One possibility is to use a direct injection alcohol boosted (DIAB) two-tank system with direct injection of methanol when the engine is prone to knock. This allows a very high specific torque output to be used while maintaining emissions at low levels. It also makes it possible for a spark-ignited petrol engine to operate at a high compression ratio while producing a torque output that is equal to that of highly turbocharged clean diesel engines.

Similarly, methanol could provide efficiencies that are comparable or higher than diesel with applications in a dedicated alcohol engine. The blends would need to be high – typically in the region of 85 per cent methanol – with cooled EGR used to lower the output of nitrogen oxides and reduce the need for intake throttling.

Methanol could also be featured as an alternative to directly injected spark ignited heavy duty engines. A small, four-litre high power spark ignition engine fuelled by methanol or mixed alcohol could effectively replace a diesel engine with a displacement as high as 11 litres.

Our verdict – Methanol is worth more investigation

The research paper from Bromberg and Cheng is not the first time that methanol has been outlined as a potential transportation fuel. It first emerged as a serious alternative following the oil crisis of 1973 with several programs set up in California to investigate its use. At that point, methanol was introduced during a period of falling petrol prices and there was no real economic incentive to continue the programs. It has also fallen behind crop-based ethanol in terms of promotion and incentives from governments.

However, now the economic and environmental situation means that the pressure to find alternative fuelling methods is more urgent. In this regard, methanol has the potential to substantially decrease energy dependence and to lower the environmental footprint of the transportation sector.

Nevertheless, substantial obstacles exist that prevent it being employed on a large scale. For example, there is simply not enough biomass in the US to displace all of its transportation fuels with renewable methanol. However, methanol can be used directly in fuel cells meaning it could play a more significant role should this technology achieve commercialisation over the next two decades.

For now, more investigation is needed to see how methanol can be used in the present conditions. It is not a solution that is better than all other options, but it is attractive and could be a vital part of a combination of alternative fuels that ultimately solves the transportation fuel emissions problem.

Source: thegreencarwebsite.co.uk