From: Gerry Bates
Spring Hill, Sheffield S10
The promoters of electric and hybrid vehicles seem to believe that the laws of physics don’t apply to them.
Energy out always equals energy in and a bus operating within a given performance envelope will require the same amount of energy whether it is a simple diesel or a hybrid vehicle.
Most of the energy goes in rolling resistance but with a stop-start service and the city’s many hills, some advantage can be gained by recovering the energy normally lost as heat in the brakes.
Unfortunately, this advantage is gained at the expense of more complex and costly systems, leading to more expensive maintenance regimes and possible reliability issues.
The recovered energy has to be stored and we all know the sorts of problems surrounding batteries in terms of effectiveness, overall life and cost. The larger the battery the greater the saving but batteries are heavy, have a short life and their output becomes limited very quickly.
An external power source for a passenger vehicle - i.e. a trolley bus - eliminates most of these issues.
Maintenance costs are low compared even with a diesel vehicle, no batteries are necessary as the recovered energy can be fed back into the power supply and used by other vehicles on the system and the lower weight leads to a reduced energy requirement for a given performance.
A further benefit is the use of carbon-zero energy sources but the UK’s current balance of 81% of generation from carbon sources (oil, gas and coal - mostly imported) compares unfavourably with France’s less than 10%.
However, much of the energy loss is due to rolling resistance and occurs at the interface between the wheels and the road surface.
We have technology to reduce this - steel wheel on steel rail. For a given vehicle weight a tram suffers only a fraction of the rolling resistance caused by rubber on tarmac and is the most carbon dioxide efficient form of urban transport. The advantages of the light rail vehicle, characterised by the tram, can be extended to inter-urban journeys in the form of the tram-train and it is a great pity that some doubt now hangs over the experiment to be conducted between Sheffield and Rotherham,
The short-termism inherent in this country baulks at the high initial cost of a tram system but ignores the huge full-life savings. Compare this country with the rest of Europe.
A prime example is Kassel in Germany where the use of tram-trains has seen revenue on the previous heavy-rail system increase by about 300% with costs roughly halved.
Diesel tram-trains are also used but, compared with a bus, they generate around 75% less carbon dioxide.
The proportion of electrified main-line railways in this country compares unfavourably with Europe as well. Electric trains can also effectively recover braking energy and distribute it to other trains on the system.
The Manchester-Sheffield-Wath electrics were doing this trick in the 1950s, with power from freight trains braking constantly on the steep descents from Woodhead powering the trains climbing the gradients.
Come on Britain! A little short-term pain can lead to immense long-term gain.