Fuel for thought

I read with interest your articles on the many measures being instigated to resolve the problems of road vehicles being reliant upon fossil fuels to provide the energy to generate motive power .


I read with interest your articles on the many measures being instigated to resolve the problems of road vehicles being reliant upon fossil fuels to provide the energy to generate motive power (News, 11 December, 2006).


In the case of using bio-ethanol with what, at first, appears to be an excellent solution to the problem, there was one missing factor from the argument — the energy transfer efficiency of internal combustion engines. Modern cars, in particular, are about 30 per cent efficient when using petrol, indicating that 70 per cent of the fuel energy is wasted.


Diesel engines are better at approximately 40 per cent but it still means that 60 per cent of the energy is wasted. Remove the silencers from the exhaust system, block the cooling system and the energy wastage becomes all too apparent. Clearly, the use of bio-fuels will do nothing to resolve this problem.


I have a 1986 VW Golf GTI, which has neither a catalytic converter nor an electronic engine management system. In fact, the fuel injectors are pure mechanical devices driven by mechanically-controlled pressure and flow rates. A 1.8 litre petrol engine, using standard 95 RON unleaded petrol provides 53 mpg to and from work in summer, slightly less in winter.


As to exhaust emissions, the levels are extremely low and CO2 is significantly lower than the same model today, even with a catalytic converter fitted.


Nearly 21 years after my car was first registered, it breezes through the MOT with exhaust emissions that are so low they can only just be detected. This means, in many cases, that it is a clear-burn vehicle compared with modern equivalents — even those fitted with sophisticated electronic engine management systems.
Moving on to the idea of electrically-powered cars, the problem is generating electricity cleanly. Currently the highest carbon dioxide pollution source in the UK emanates from fossil fuel-based electricity power stations. This means that we are in danger of simply shifting the problem rather than solving it.


The use of bio-fuels is simply another stop-gap measure in the same way the catalytic converter was supposed to be 30 years ago. In other words, it is a short-term fix where, just like the converter approach, it may be many decades before the underlying problem is really solved. Even when thinking that electrically-powered cars are the answer, this has a questionable element since this will only work once clean electricity generation is the dominant source of power.


Andrew Porter, Hitchin, Herts


The bio-ethanol that Shell is hoping to produce in the plant mentioned in the article would only ever be used as a blend with conventional petrol.
Full-scale replacement of fossil fuels could be possible with bio-diesel, which might also be made from agricultural wastes; research for these processes is at an earlier stage. During 2007, the Engineer ‘Year of Energy’, we will cover technologies for hybrid cars and clean electricity generation which could go some way to solving the problems Mr Porter mentions — editor.