“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

Saturday, January 05, 2013

Energy - what can be done (Part 2)

In my first post in this series, I discussed possible primary energy savings in the area of commuting to work. In the second post in the series, I want to address what might be saved in terms of personal/passenger transportation other than commuting. Such things include vacations, shopping, miscellaneous non-commuting trips, etc. Such transportation can utilize light vehicles (cars, light trucks, SUVs), airlines, etc. I will include work-related travel other than commuting in this category (e.g., my trips to Houston or Washington D.C. for conferences). Again, I'll be relying on the Transportation Energy Data Book. For light vehicles, I'll use data from Chapter 8, for air travel, it will be Chapter 9.

In the previous post in this series, I had five bullet points for possible methods to reduce energy use in commuting. A similar list would apply here:
  • "Trip combining"
  •  Use of public transportation
  • Utilizing more fuel efficient vehicles
  • Driving more slowly (and other efficient driving techniques)

For household vehicle use, the latest data that can be used for these calculations is 2009. From Table 8.1 we find that ~2.957*10^{12}~ (almost 3 trillion) miles were travelled. From Table 8.9 we determine that 71.3% of these miles, or ~2.108*10^{12}~ (about 2.1 trillion) of those miles were NOT commuting to and from work. I'll need to engage in a bit of interpretation to determine the average fuel economy of the household vehicles travelling these miles. I'm using the Transportation Energy Data Book Quick Facts to infer that the average light vehicle fuel economy is 20.45 (calculated from the weighted average of cars and light trucks). I'm also working on the assumption that the figures represent EPA estimates. So we can estimate that ~2.108*10^{12}/20.45=1.031*10^{11}~ (103.1 billion) gallons that come from ~5.425*10^{9}~ (5.425 billion) barrels of oil.

Trip combining saves fuel in a couple of ways. First, a warm engine uses less fuel than a cold one. Second, multiple out and backs from home can be minimized. So going to the store, then from there to the cleaners, to the nail shop, to the mall, etc. rather than out and back to each saves a significant amount of fuel. It's hard to get a quantitative handle on this since it will be different for each household, each driver, and each day so I'll arbitrarily speculate that this type of trip planning will affect the 33.3% of vehicle miles travelled for "shopping" and "other family/personal business" in Table 8.9 (link is above). Further, I'll speculate that 10% of this fuel consumption can be saved. So the potential fuel and oil savings are ~0.333*0.1*1.031*10^{11}=3.433*10^{9}~ (3.433 billion) gallons from ~1.810*10^{8}~ (181 million) barrels of oil. This is enough oil for a bit under 10 days of consumption in the U.S.

As I mentioned in part 1 of this series, use of public transportation may or may not save fuel and I'll dedicate a post to my thoughts on this at a later time.

The calculations I used in the part 1 for utilizing more fuel efficient vehicles and changing driving methods can be used here as well. First, we'll use an increase from 20.45 to 30 (in this case) m.p.g. (noting that there is a large number of vehicles that do much better than this). This would reduce the 103.1 billion gallons used in non-commuting personal transportation to ~2.108*10^{12}/30=7.027*10^{10}~ (70.27 billion) gallons, a savings of 32.8 billion gallons that come from 1.73 billion barrels of oil. In the U.S., we consume this amount of oil in about 92 days. We are now officially getting someplace!

As to more efficient driving, so as to be conservative, I'll assume these more efficient drivers are driving the more efficient vehicles from the previous paragraph. I'll then assume that we can convince/incentivize/coerce 25% of them to drive in such a way as to exceed the EPA estimates (on which the previous calculations in this post have been based) be 10%, i.e., to achieve 33 m.p.g. (noting that I exceed the EPA estimate by 22% without using the more extreme hypermiling techniques such as pulse and glide, extreme drafting, etc.). In that case, the 70.27 billion gallons would be reduced to ~2.108*10^{12}/33=6.388*10^{10}~ (63.88 billion) gallons, a further savings of 6.39 billion gallons of gasoline that come from 336 million barrels of oil - 18 days worth.

As previously, let's arbitrarily reduce the savings by 25%. We can then estimate that about 1.7 billion (dropping a bunch of significant figures) barrels of oil per year. This represents about 25% of our consumption.

And not burning these 1.7 billion barrels would result in not emitting 605 billion pounds or 303 million tons of carbon dioxide.

Combined with the 9% from commuting, it's reasonably possible, without massive technology boosts, lifestyle changes, etc. to save over a third of the oil we consume just by adjusting the way our households utilize personal vehicles.

Next up: Freight

1 comment:

Dr. George W. Oprisko said...

This is all well and good.. . .

However, the savings you discuss are trivial. To reduce consumption >60% requires a new paradigm, evinced by the
current transport system of France.

In France, one can travel by electrified rail to virtually every city and hamlet in the country. From there, one can rent a bicycle at the train station for the remaining distance to one's destination, or
one can walk.

It seems to me that we need a transport system in the US analogus to the one we had during WWII. At that time >95% of all freight went by rail, rail pass service was the mode used by the average joe, or the bus, and interurbans served most cities and towns.
Were such a system driven by renewable electricity, it would consume no petroleum whatever.

It also appears that we must complete such a system via bicycles/walking.