Saturday, November 8, 2014

Day 5: Rocky Mountain High

The title refers to the elevation—we’re up above 5000 feet for the next couple days, where the sun is stronger and the air is thinner.  (This last piece of information will become more relevant later in this post.)

We woke up with a fantastic view of the Flatirons out our hotel window.  LJ got the Tesla and we headed into Boulder for lunch with Dave (grad school friend) and his family.  Driving into Boulder, I was astonished at how much has changed since I moved away in 2005 and even since I last visited in 2012 for Dave’s wedding.  Sadly, it seems Boulder has started to lose the uniqueness that I fondly remember.  I’m sure that the Pearl Street mall still has locally owned, quirky shops but the part of Boulder we were in was chock full of chain stores.  Traffic also seems to have gotten worse since I left.  The natural environment still makes it a beautiful place to live but I don’t think it’s the same place I spent my 6 years of grad school.

After lunch, we were off to a short afternoon stop in Golden to see Jen (another grad school friend).  Clear blue skies and 65 degrees made for a great day to walk into the center of Golden for ice cream.  We still had many miles to go so by 3 pm we were on the way.  From Golden, we took US-6 through the mountain and then picked up I-70 headed west. Instead of the faster but boring Eisenhower tunnel, we crossed the Continental Divide over Loveland Pass.  There had clearly been some snow this season but the road was dry and clear.  
Highest point of the trip


On the downhill from the pass is where we encountered negative energy usage. No, we did not break the laws of physics and destroy energy.  But the Tesla regen system is so efficient on a steep downhill that we put more energy back into the battery than we took out.  Over the course of the trip, it has not been surprising to see a few data points for the average energy drop below zero, but this was the first time that we saw a 15 mi trendline for the value end up that low.  (Below is an example of this graph.)  Post-pass, we charged up enough at Silverthorne to get us to the next charger at Glenwood Springs.

Negative energy!!!

Once we left Silverthorne, the evtripplanner calculations for western Colorado were wildly off, by 50% or more.  The energy calculations were on the high side, meaning that we didn’t have to worry about getting stranded.  These calculations had been quite accurate early in the trip even with the elevation changes in the mountains of the eastern US. 

Western Colorado is where we learned about the importance of air density to the Tesla’s energy usage.   The air density is a key factor in the density altitude, which can be thought of as the air density as a function of elevation.  The pilots and air travel nerds out there will know what I mean as this is critical to how a plane operates.

Evtripplanner does include a number of variables, from the specific car model and tires to the internal and external temperatures and the net elevation gain.  A more accurate calculation would include air density/density altitude.  Not only would that take into account the stiff headwinds of the plains states, it would also cover the significantly thinner air at Rocky Mountain high elevations.


Once we established that the energy calculations were on the low side, we made really good time.  We only needed a couple stops in western Colorodo (Glenwood Springs and a dinner stop in Grand Junction) to get us into Moab about 10:30 pm. 

Day 6 of #TeslaElectricStartupSuperTrip is planned as our other main National Parks day, with trips to Arches National Park and Canyonlands National Park.  Stay tuned!  Only a couple more days until the adventure is over.

Day 5 stats:
395.5 miles in 11.5 hours with one overnight charge and 3 SuperCharger stops:
·         Overnight at the Superior Town Hall
·         Silverthorne, CO
·         Glenwood Springs, CO
·         Grand Junction, CO (dinner)

Overall trip stats: 2861.5 miles in 5 days having used a total 1021.5 kWh

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