TRANSPORT

ENGINES FOR TOMORROW'S ROAD TRANSPORT

Introduced by Don Lovell, Convener, on 9 March 1999

Tomorrow's road transport will need to be provided with well-designed and well-maintained roads and road signs, with an efficient traffic control system involving both in-vehicle devices, like radar collision-avoidance systems, and external systems like Urban Traffic Management Control, and perhaps, automatic road charging. But it will also need engines which are quiet, clean (low polluting) and energy efficient.

There are many interesting ideas being worked on at present. There are three requirements _ less emissions of carbon dixide (CO2) to reduce global warming and of nitrogen oxides (NOx) and particulates to reduce air pollution, together with lower fuel consumption for economy.

Let us look at a range of fuels.

PETROL
The present car has a petrol consumption of around 7 litres / 100 km, 40 mpg.

 

Petrol Fuel l /100km8.1 - 5.7 Range km 450-700

CNG Fuel l /100km8.1 - 5.7 Range km 250 -300

Diesel Fuel l /100km6.1 -4.7 Range km 650 - 850

The manufacturer's aim is to reduce this to 3 l/ 100km and the new small cars achieves 5.8

They do this with `lean burn' direct injection (which requires low sulphur petrol, but gives 15% lessCO2), combined with automatic gearboxes which select neutral when stationary and power steering, which together reduce consumption by 8%; and improved cold-start catalysers.

DIESEL
The latest car diesel engine design, common rail direct injection, achieves 5.5 l /100km now in a Citroen Xantia, and the VW Lupo claims 3 in a smaller vehicle. Both use low-sulphur fuel and have particulate filters.

DUAL FUEL
Next year, petrol / compressed natural gas (CNG) engines, which you may have seen advertised already by Vauxhall, will be available. CNG gives 20% less CO2, 40% less CO and 80% less NOx than petrol, is almost as fuel efficient and 30 - 40% cheaper.

(LPG (liquified petroleum gas), the alternative to CNG, is mostly butane, which is heavier than air and is thus not as safe as CNG, which is mostly methane and lighter than air).

ELECTRICITY
The first World Speed record, 65 mph, was gained by an electric car in 1899, so they have a respectable history.

Batteries At present, electric cars use large, heavy Ni / Cd batteries which give them an 80 km range and require 8 hours to recharge. This makes them impracticable for most uses. But a plastic sheet battery is under development. There was a talk on BBC Radio Four on 7 January describing work in progress on such batteries. These are flexible and can be moulded to the shape of, for example, a lap-top computer case and are light _ which is the important property for vehicle batteries.

There are ways of mixing IC engines with electric drives. `Parallel' systems use an IC engine (CNG or diesel) with a battery-powered electric motor to assist it, either providing extra power for hills or replacing the IC engine for in-town sections. `Series' systems use the battery-powered electric motor all the time and a small IC engine keeps the batteries charged by running a generator.

Both these hybrid engines are cleaner because the IC engine is smaller and runs under optimum conditions. It is also possible to include a flywheel or a super-capacitor as a short-time storage device for mechanical or electrical energy to improve vehicle performance further.

Fuel Cells There are 5 types but only the PEM (Proton Exchange Membrane or Solid Polymer) type is of interest for vehicles. The optimum fuel for use in fuel cells is hydrogen gas. The ultimate environmental system is hydrogen, generated by solar power from water, then burnt in the engine back to water with air.

The problem with hydrogen is how to store it on the vehicle. It can be compressed or liquified (at extremely low temperature) but the vessel to hold it is bulky and potentially dangerous (but perhaps no more dangerous than a petrol tank).

At present the fuel cell is being developed primarily for buses which have the space to store the hydrogen fuel in cylinders on the roof. For cars, which are being developed by all the major manufacturers, the fuel may be methanol or petrol, which can be distributed as liquids, but these two fuels introduce some CO2 to the exhaust, whereas hydrogen burns to pure water.

There appears to be a solution to the problem of storing hydrogen by absorbing it onto very fine filaments of carbon. This method is claimed to be able to provide enough fuel for an 8000 km (!) range for a car. ( The Coventry experimental cars have an 80 km range.)

So in 2025 perhaps

- you will hire an ECOCAR by the hour to collect shopping in town, running on a `conventional' but plastic battery

- for other journeys you will take an electric bus or a tram _ if you don't walk or cycle

- for long journeys a train or, if you insist on going by car, it will be CNG fuelled or electric, battery or fuel-cell; it will have `intelligent' cruise control with a radar lane-following, collision-preventing system; a constant speed engine with continuously variable transmission and a flywheel — and you will still pass on the motorway, on which you pay a toll, the 44- tonne diesel-engined lorries, although they will have low emission engines with particulate filters.

AND THE AIR WILL BE CLEANER EVERYWHERE.

Don Lovell