12 Jan. 2011
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PriUPS Project

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I'd as Leaf Not Buy a Volt

Vehicular Proliferation

It's been a while since I've posted any words about the inspiration for this web site, the Toyota Prius and its electrical charisma.  I'm prompted to mention it now by a number of recent events in car-land.  They are, in no particular order,

  • The introduction of a wagon-like member of the Prius "brand"
  • The availability of a true electric car, the Nissan Leaf
  • The Chevrolet Volt, finally "shipping" after years of speculation and some tiny glitches at the General Motors Corporation
  • The imminent arrival of the Prius plug-in hybrid
  • The notion that it might just might be time to think about possibly getting a new car.

I've been following the saga of the Volt and the Leaf for a few years.  And from the day six years ago that I bought my Prius I was keen on getting the plug-in version.  Considering just the "drive train," each has its attraction for me, if not necessarily for the PriUPS concept.  I thought it might be worthwhile to compare the utility of each against my transportation needs as well as my desire to keep the furnace and the well running during electrical outages.  (And, of course, the desire to prevent ice-cream meltage.)  I'll try not to ruin the suspense, although just the title of this blogitem takes us part of the way to resolution.

The Plug-In Hybrid Prius

The last to be available (which should be next year), but the first to be announced or at least rumored, I had long coveted one of these.  What's not to like?  Drive on electricity for however many miles, have a greater capacity lithium battery to run the house, and possibly get better gasoline mileage as well.  Great dream but flawed vehicle.  Since it isn't actually shipping, some of these "facts" may be incorrect.

The first problem seems to be that the actual increased electric mileage is very limited.  12 to 18 miles is fine if your commute is 5 miles or less, or twice that if you can plug in at work.  So this will be a worthwhile improvement for some, and of little value for others.  I'm one of the others.  The second problem is Toyota's decision to stick with NiMH batteries.  Lithium is lighter and has greater energy storage per kilogram.  Even worse, Toyota seems to have decided to make the plug-in hybrid with three NiMH battery packs similar to the ones now in the standard Prius.  Even more worse, only one of them gets charged by the engine and the other two, once their charge from the grid is used up, sit there slug-like, and reduce the car's mileage due to the parasitic weight.  In other words, depending on your driving habits, you might actually suffer slightly reduced mileage with the plug-in Prius.  It will presumably cost somewhat more due to the price of the extra battery packs, but will only be a benefit for frequent short trips. 

As far as the PriUPS project is concerned, it would seem that there would be no difference between the standard Prius and the plug-in.  Presumably once the three traction batteries reach the lowest allowed state of charge, two of them disconnect and, at least as a PriUPS, all remains as it is now. The gasoline engine will charge a single traction battery, which then supplies power to the house. 

The Nissan Leaf

Mentioned more for completeness than as a serious source of house power, the Leaf is a true electric car with a range of 100 miles.  Or 60 miles.  Or 80 miles.  Or somewhere in there.  Of course, it gets "infinite" miles per gallon since there's no place to put the gallons anyway.  It's an attractive alternative for transportation, if for some reason you buy a car for that.  But since it has no internal combustion engine (ICE), once its capacious batteries are depleted, your ice cream melts just as fast as it would if you had no emergency power at all.  The Leaf battery pack stores 24kWh, compared to 1.4 for the Prius, so one could reasonably expect 15-20 times as much backup time as the Prius battery alone can provide.  Is this enough?  Maybe.  If your total load is only 1kW, it might suffice for a full day.  A more typical household load of 2-3kW would last for proportionally less time. 

The non-PriUPS problem with the Leaf is the much ballyhooed* "range anxiety."  Even with a 100 mile (or whatever) range, comfortably more than I normally drive, I worry about traffic jams.  All you have to do is whisper "Cross Bronx Expressway" in the presence of the Leaf and it reacts like Robby when told to shoot the Id Monster.  I would so dread being stranded in the very rare traffic jam I encounter that all enjoyment of my gasoline-free existence would be obviated. 

The Chevy Volt

The long-awaited Volt would seem to be everything that the plug-in Prius isn't quite.  The big lithium battery with a 40 mile (or whatever) electric range is enough for my commute.  The generosity of our government would partially overcome my parsimony when confronted with the $43k price tag.  And it's kind of cute and has lots of gadgetry.  For transportation, it would cut my fuel usage down to almost nothing.  What's not to like?  Software!

I found a copy of the Volt manual on line.  It's 516 pages long, and I read as much of it as I could bear to do.  As far as I can tell, the Volt is useless as a home generator.  Despite having the specifications, the hardware, and the apparent capability of being one, it seems that the operating software doesn't allow the ICE to charge the battery when the vehicle is stationary.  I was hopeful for a few pages as I was reading about "mountain mode" which seems to allow the engine to pre-charge the battery before the car is asked to attack future steep grades.  But there's no reason to expect this to work when the car is in the garage.  If anyone knows different, please tell me, since the Volt seems otherwise ideal.  As the software is written, however, it appears that the only use you can get from the Volt is travel.  What a shocking waste.

New Car Gas Mileage

Which brings me to the final item:  A new car.  My Prius is getting close to the 100,000 mile mark.  It's still in good shape and still is the ugly champagne color which was all that was available when I got it almost six years ago.  I would love to replace it with something blue, but given the array of non-choices above, I shall wait.  2012 will probably bring us a new assortment of cars to consider.  Meanwhile, with the Prius, I have cut my gas consumption in half, and to duplicate that saving with a non-electric vehicle, I'd have to invest in one that is driven by moonbeams.  Although a small increment in mileage potentially achieved by improvements in later Prius models is desirable, it will never match the initial bonanza of substituting the Prius for a standard car.  Likewise, the monetary saving achieved by the exercise of patience is unlikely to be duplicated by gas savings or tax credits.  So mote it be, at least for another year or two.

*The first asterisk of 2011.  In all my blogs, I've never used the word "ballyhoo."  I wanted to see if it would come out right.

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