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# Re: china high speed rail

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• To: seaint(--nospam--at)seaint.org
• Subject: Re: china high speed rail
• From: Avi Sharma <leisuresoul.avi(--nospam--at)gmail.com>
• Date: Fri, 29 Oct 2010 12:50:41 +0530

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 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