[LINK] Electric vehicles and generation

Antony Barry tony at tony-barry.emu.id.au
Sun Jul 23 13:30:06 AEST 2006

On 23/07/2006, at 11:05 AM, rchirgwin at ozemail.com.au wrote:

> Power and range are eventually going to run into physics.

The physics involves weight
> The limit is ultimately how far a body X kg can travel using Y kW  
> of power, how much you can carry in the batteries, and electricity  
> distribution practicalities (how many houses can be fitted with 70- 
> amp circuits).

Remember the weight of the vehicle. A car weighs 1000kg and is  
usually only shifting a payload of less that 100kg. Only 10% of the  
energy that actually gets to move the vehicle is being useful. The  
vehicle is only so heavy because we want to go fast and have to make  
it strong enough for the passenger to sometimes survive a crash.

And because we want to go fast and have high acceleration the engine  
is usually not operating at an optimal speed. 80% of the energy just  
heats the air and tarmac. Only 20% moves the vehicle. Add it all  
together and you are lucky to get 1% efficiency overall.

If we went at half the speed I suspect we could make the vehicle a  
quarter of the weight. The Rocky Mountains Institute has done a lot  
of work on this - http://www.rmi.org/sitepages/pid386.php

My recumbent tricycle weighs 19kg and the trailer another 10kg. It  
will carry me (93kg) and 50kg of cargo at an average speed of 15kmph  
_without_ a motor. That's over distance with hills. Over a short  
distance on the flat I can zip along at 25kmph. Now if I was still  
young and fit instead of being 65 ....


phone : 02 6241 7659 | mailto:me at Tony-Barry.emu.id.au
mobile: 04 1242 0397 | mailto:tony.barry at alianet.alia.org.au

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