The New York Times has an opinion article titled Plugging in the Postal Service where Ruth Goldway expounds on the virtues of converting all the US postal delivery truck to electricity. It turns out that the US Postal Service has already looked into this in 2005. They had asked a Dutch company, E-Traction, that specializes in in-wheel electric motors and did a study on exactly that. Here is the text:
At the beginning of 2005 we were approached by the U.S. Postal Service to power their small delivery vans. Our calculations showed that with relatively minor modifications an e-Traction powered version could comfortably:
1. operate a U.S.P.S. delivery van,
2. with a single direct drive SM350/1AL unit with a side mounted differential,
3. using on average 3.1 kW per hour,
4. with only eight 100 Ah Lithium-Ion batteries,
5. for an entire workday,
6. with an average speed (when in motion) of 20 MPH,
7. with a maximum speed of 55 MPH,
8. at a total distance covered of 80 miles,
9. and an overall vehicle weight of 3,334 lbs*,
10. including one driver of 200 lbs,
11. and including 250 lbs of mail.
* Based on an empty vehicle weight of 3,050 lbs. Estimated weight loss in conversion: traction motor 270 lbs, transmission 175 lbs, and differential 175 lbs. Estimated weight gain in conversion: SM350/1AL 187 lbs, batteries 220 lbs, and onboard charger 22 lbs.
The cost of recharging these batteries with cheap electricity from the power grid can hardly be compared to the ever rising cost of fossil fuel. Our SM350/1AL has been designed for 600,000 miles between overhauls. The Lithium-Ion batteries will last at least 2,000 complete cycles or roughly 8 years.
Neither article answers the question of whether our power grid could handle charging up all these electric vehicles although Goldway suggests putting solar panels on the buildings to charge up these vans and other electric vehicles that happen drop in. It's also not clear how fast these vehicles could be converted or how fast batteries could be created, seeing that Toyota is also struggling to get enough for their own vehicles.
But, it is a nice idea. I like the idea of in-wheel electric motors, as they avoid most of the inefficiencies that a traditional power train has due to friction in the gears. With the motor in the wheel, the power is transferred directly onto the pavement. The trick is in the controlling electronics which I am sure is hard to get right.
It would be interesting to find out what the US Postal Service did with the full report from E-Traction. This would be a nice little job for a budding journalist.