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Jesse Tufts
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Well this bus has a bit under 4 times the battery capacity of a Model S but I'm sure it weighs more than 4 times the amount and isn't nearly as aerodynamic. I doubt a model S could do 250km in the type of stop and go driving that a bus has to do. I built and drive my own electric vehicle (a converted Japanese mini truck) and those consumption figures seem completely reasonable for a vehicle of that size. I can easily see 250wh/km in aggressive stop and go driving. Regenerative braking helps but you only recover a small portion of the energy you used to accelerate in real life and that's all a bus does all day long. Now the heater, say they're using 80% of their 324kwh pack, 259kwh, over 8 hours that's an average draw of 32.4kw from the battery. If their motor and controller are 90% efficient then you have 3240w of waste heat available continuously over that time period. Even if you could effectively capture 80% of that (likely impossible unless you insulated the motor so it didn't radiate that heat to atmosphere under the bus) that's only ~2600W of heat. I have a 1600w heater in a very small insulated cab and it's not even close to being enough when it's -20 C outside and I tend to keep the doors closed when I'm stopped. The 31 people will put out more than 2600 watts and that's not enough to keep the bus warm otherwise a heater wouldn't be needed at all. The 2600w might keep the front window clear. With something that has that many windows and that much surface area with a continuous windchill from moving through the air you need a lot of heat to keep it comfortable inside when it's -20 C or colder. The diesel heater will burn much cleaner than the diesel engine due to more complete combustion. I'm impressed, I think it's great progress and in Quebec where 96% of the electricity is hydro this is a huge reduction in GHGs and other emissions compared to a diesel bus. Not to mention vastly reduced noise, vibration and maintenance.
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Jan 30, 2014