How Plug-in Hybrid Cars Reduce Dependence on Fossil Energy – Some Real Data – Part I

New Plates

1.0 Introduction.

Getting a different car means new license plates.  I dislike taking a number and waiting in line at the DMV.  Fortunately I remembered to take a good book to read and the new vehicle registration took just over an hour on a Thursday afternoon.     Because of the example set by my daughter-in-law when she bought plates for her Smart car, and the encouragement of my partner Gail, we now have “special plates” on the Chevrolet Volt – my first non-standard license plate in 54 years of owning cars.  The license plate says “Advancing Clean Energy.”   Seems somewhat appropriate, but “Advancing Clean Transportation” or “Reducing Dependence on Oil” would be better.

2.0 How does the Plug-in Hybrid work?   So how does an electric vehicle or a plug-in hybrid vehicle “advance” clean transportation?  Does an electric vehicle or plug-in hybrid reduce our dependence on oil?  On fossil energy?

There are several all-electric and plug-in hybrid (electric plus gasoline) cars available to American buyers today.  The plug-in hybrid uses a combination of two types of energy for propulsion: 1) electrical energy stored in a battery,  and 2) chemical energy stored in gasoline.    The plug-in hybrid is designed to conserve gasoline and can be driven in a pure electric mode.  Let’s assume you start out with a fully charged battery and a full tank of gasoline.  Initially the plug-in hybrid car is powered only by its electric motor.   When driving in this mode, there is no combustion and hence the car has zero emissions.  In this electric mode, no fossil energy is being burned and no CO2 is being dumped into the atmosphere.   This mode of operation of the plug-in hybrid does indeed provide clean transportation just like an all-electric car.

With the plug-in hybrid Volt for example, one can drive 40-45 miles using electric stored in its Lithium-ion battery before the gasoline engine automatically starts up and allows you to drive an additional 325 miles using gasoline.   When the Volt’s gasoline engine is running, there is combustion within the engine and its emissions are like any modern gasoline-powered car that gets 37-40 mpg.    Obviously with the Volt, if you just drive across town and back home and the total trip is less than 40 miles, the gas engine will never start up and you will not burn any gasoline.

3.0 Some Real Data – Observation of a Plug-in Hybrid for the past month (as of 6/17/2012)

In our specific case, most of our driving during the past month involved trips that were less than 40-50 miles, so we used very little gasoline (0.7 gallons to be specific) as illustrated in the table below.      The instrument panel on the Volt provides information about the electrical usage as well as the gasoline usage of the car.   We simply recorded the Volt’s energy usage data for the past month in the table below (see column 2 “NOW”).

Prior to getting the Volt, we were driving a standard gasoline-powered car (a Chrysler Town and Country van that gets about 21 miles per gallon on the highway).   For comparison we have included Column 3 – the “BEFORE” scenario that assumes we had driven the same number of miles using our standard gasoline car.

3.1  Scenario #1   Local everyday driving.  

Over the past month, we made multiple trips around the metro area.  Most of these trips were less than 40-50 miles round trip (e.g. to grocery store, to dentist, to eye doctor, to hardware store, to church, to teach-ins, to restaurants, to downtown Denver,  etc.).   Several trips were longer than 50 miles (to Woodbine Ecology center in Sedalia, to Falcon Park in the foothills, etc.).  None of these “local” trips exceeded 60 miles, the total of all these daily trips was 788 miles.   Energy usage (electrical power, gasoline) is provided in the table below:
To summarize Scenario #1, this past month we drove the plug-in hybrid a total of 788 miles for local trips.  760 miles were powered with free energy we generated by harvesting sunlight using solar panels.   Solar photovoltaic  (PV) panels on the garage roof generated the 214 kWh of electrical power needed to drive those 760 miles.   As a result, 96% of our local transportation miles traveled last month could be considered sustainable.  The remaining 4% of our transportation was not sustainable.   On some trips we used up all the stored electrical energy in the Volt’s battery and the gasoline engine started automatically to finish these trips – fortunately the gas engine of the Volt (@40 mpg) is more efficient than our Town & Country van’s engine (@21 mpg).    With this gas mode of operation, we drove a total of 28 miles and burned 0.7 gallons of gasoline that we did have to buy ( $2.60).  Had we driven the standard gasoline powered vehicle (Town & Country), we would have burned 37.5 gallons of gasoline and paid $140.

The plug-in hybrid reduced our gasoline (petroleum) dependence by 98% for local transportation.    

And in our case no coal was burned to provide the electrical power for the plug-in hybrid because the Sun provided this energy via photovoltaic panels located on the garage roof.       

3.2  Scenario #2   Longer trip into the mountains. 

In addition to the many local trips described in Scenario #1, we also drove into the nearby mountains for some hiking this past month.   The itinerary began in Centennial to US 285 to  I70 to Guanella Pass to Silver Dollar Lake Trail Head where we took a short hike to capture some pictures of wild flowers – specifically our state flower, the Columbine.    Although we were a month earlier than a similar hike last year,  the terrain was significantly drier this year, the lake was 3-5 feet lower, and much of the grass was already brown.  The color of the Columbine, although still quite beautiful, seemed to be less vibrant, more muted possibly because of the lack of rain this year.

But we will not attempt to connect any dots because everyone knows that climate is weather averaged over 30 years.  The fact that we are breaking  50-100 year-old records for weather extremes such as heat, drought, tornados, high winds, etc. and there are massive unprecedented fires burning in Colorado, Arizona, Utah, and New Mexico before summer has even yet begun is insufficient to even suggest there is any climate change – at least that is what some say.   You get to decide if the current behavior of 7 billion humans on this planet is having any effect on the global ecosystem; I’ve already decided.

From Silver Dollar Lake, we headed to Grant then to Bailey and back to Centennial for a total round trip of 135 miles.

The car performed well and exhibited plenty of power going uphill (full tank of gas, driver and one passenger).   The uphill portion of the trip consumed the stored electrical energy within 30 miles (on level terrain there is adequate stored electrical power to drive 40-45 miles).   We consumed all of the electrical energy original stored in the battery plus 2.1 gallons of gasoline.   The gas mileage of the plug-in hybrid was 64 miles per gallon (mpg) for this mountain trip and the energy usage is provided in the table below:.
To summarize Scenario #2, we drove the plug-in hybrid into the mountains and over Guanella Pass (elevation 11669 feet) for a total of 135 miles round trip.  The round trip consumed 2.1 gallons of gasoline ($7.88) resulting in 64 mpg.   Had we driven our Town and Country van, we would have consumed around 7.5 gallons of gas ($28.12), so the plug-in hybrid provided a 72% reduction in dependence on oil for this specific trip.   We saved $20.24 on that one trip.

The plug-in hybrid reduced our gasoline (petroleum) dependence by 72% for this specific trip into the mountains.  

From this information we can project how the plug-in hybrid will perform on a much longer non-stop trip – say several thousand miles – a trip we plan to take later this summer to visit family back east.   On long trips, the car will operate almost completely in the gas mode.  The Volt gas mileage is advertized to be around 40 mpg highway; we will be evaluating this long distance highway driving next month.

The plug-in hybrid should reduce our gasoline (petroleum) dependence by 50% for extended non-stop long distance trips of 500 miles or more.   


4.0  Conclusions

There is no question the plug-in hybrid can and does reduce our dependency on foreign and domestic oil.

For the majority of our personal transportation needs, by driving a plug-in hybrid, we can reduce our dependence on oil by 72%-98%.

Because we are using solar PV panels to harvest current sunlight and generate our own electrical power for the plug-in hybrid vehicle, we can also say that we have reduced our consumption of fossil fuel, the burning of hydrocarbons and the introduction of CO2 into the atmosphere by 72%- 98% from the previous month when we were driving our standard gasoline burning car (Chrysler Town and Country van).

But “reduce” is the key word.   Our new method of transportation is still not sustainable.    To live sustainably, we must do more than “reduce” our consumption of gasoline/petroleum by 72%-98%.  We must eliminate our consumption of oil completely.   And it appears possible.  But that’s another story for Part II

Explanation of Notes in Tables

(1) We define “sustainable driving” as transportation that uses renewable energy (solar, wind, solar generated electric, wind generated electric, etc.)    We define “unsustainable driving” as transportation that uses/consumes/burns finite resources such as oil, coal, tar sands, natural gas, etc.

(2) The electrical power used to charge the Volt’s battery was generated using solar photovoltaic panels mounted on the garage roof so there was no additional cost for this electrical power since the Sun has not yet been privatized by a “for-profit” corporation.    If you have to buy your electrical power, the cost of commercial coal-generated electric is about $0.11 / kWh.   You would have to pay your utility company $23.50 to charge the battery for those 788 miles.    Or we could have paid the oil and gas industry $140 for gasoline if we had driven a standard internal combustion engine car those same 788 miles.


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