Re: china high speed rail

Dear Irv,

           Modern electric trains like the shinkansen use regenerative braking to return current into the catenary while they brake. This method results in significant energy savings, where-as diesel locomotives (in use on unelectrified railway networks) typically dispose of the energy generated by dynamic braking as heat into the ambient air. And wrt to the data available-

Cars use around 32-36.6 MJ/Lit-capacity 4

Airlines use around 1.4 MJ/passenger-km capacity 49

HSR use around 0.15 MJ/ passenger-km capacity ard 300-400

 

Difference is quite visible !!

 

Regards.

 

On Fri, Oct 29, 2010 at 11:53 AM, IRV FRUCHTMAN <ifaeng@yahoo.com> wrote:

Fellow Engineers, High speed trains are wonderful engineering feats, but I don't believe saving energy is one of them. As I recall from my school days: drag force is proportional to speed squared and power (read energy) is proportional to speed cubed. Therefore a train moving at 300 mph, compared to a train at 100 mph,  uses (300/100)^3 = 27 times as much energy.  If the requirement for the number of trains is reduced by 1/3 – to move the same number of people - then the increased energy use is 27/3 = 9. Therefore, 9 times as much energy is required to move the same people/ load with a high speed train as compared to "low" speed train.  Given a choice, I'll take an airplane. Irv

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Avi Sharma
Student
Department of Civil Engineering
SRKNEC, Nagpur ,India