“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)

Sunday, December 30, 2012

Energy - what can be done?

I want to spend a few posts looking into what can be done. Unlike many of the excellent blogs to which I try to direct attention in my "blog roll," I'm not going to analyze what resources are available, what technological breakthroughs may be on the horizon, etc. I'm going to look at the amount of energy we (in the United States) can save using currently available technology and by changing currently ingrained habits. I'll first look at ground transportation, then shipping, then air transportation, then savings in the built environment. This last will include insulating, windows, lighting, motors (in industrial facilities), and HVAC (heating, ventilating, and air conditioning).

As I wander through this, please bear in mind that I'm assuming evolutionary progress in technology, not revolutionary breakthroughs (fusion, methane clathrates, etc.). In fact, in this series of posts I won't be addressing harvesting and generation at all. In other words, these benchmarks can be achieved in the near to intermediate future without dramatic scientific or societal changes (albeit using my personal definition of what would not constitute a dramatic societal change - yours may be very different).

For transportation, one of the main sources of information will be the "RITA" (Research and Innovative Technology Administration - Bureau of Transportation Statistics) site. Chapter 4 of the linked site is entitled "Transportation, Energy, and the Envionment" and it contains a cornucopia of statistics on the use of transportation fuels in the U.S. I'll start here.

For personal, non-commercial transportation (including work commutes), there are several strategies:

  1. Carpooling
  2. Telecommuting
  3. Using more public transportation (arguably and conditionally  - see here for example)
  4. Driving more efficient vehicles
  5. Driving more slowly
Let's start with commuting to work. Of the listed possibilities, telecommuting offers, basically, a one for one reduction in energy expenditure. If I work from home for a day, that's 62 miles not driven and 1.2 gallons of fuel not burned. Carpooling may come close or even do better. If two people who drive, say, 25 m.p.g. vehicles carpool, the total fuel burn is halved. However, suppose I carpool with someone whose vehicle gets 25 m.p.g. (and who lives next door to me or a close approximation thereof). When each of us drives, 3.7 gallons are burned. If I drive, 1.2 gallons are burned, reducing the fuel burn by 2.5 gallons or about 68%. However, when he or she drives, 2.5 gallons are burned and the reduction is only 1.2 gallons or a bit more than 32%. That's still pretty significant.

Here we find statistics on annual commuting miles, the most recent my google-fu could uncover. The document is based on data derived from the National Household Travel Survey. According to the survey, in 2009 we (in the U.S.) commuted to work for a total distance of ~6.235*10^{11}~ (623.5 billion) miles. And according to this table, the average light vehicle fleet fuel economy that year was 22.4 m.p.g. Thus, we can estimate that we burned ~2.783*10^{10}~ (27.83 billion) gallons of gasoline and diesel fuel in this endeavor. Based on the economy in 2009, I'd expect that figures determined from that year would be conservative with respect to potential fuel savings in absolute terms, but that the percentages would be representative.

For telecommuting, let's hypothesize that 5% of the workforce could move from commuting to telecommuting and could do so for 25% of their workdays (one day per week for three weeks, two days on the fourth). That would be an annual reduction of 1.25% in the commuter miles driven and a reduction of ~3.479*10^{8}~ (347.9 million) gallons of fuel. Since a barrel of oil produces about 19 gallons of gasoline, the resulting savings would be ~1.831*10^{7}~ (18.31 million) barrels - about one days worth at current U.S. rate of consumption. Clearly, this isn't THE answer!

As to carpooling, I'd be surprised if we could coax 20% of the single occupant vehicle commuters into carpools or vanpools. On the other hand, coaxing six people into a vanpool will save something like 75% of the fuel that would otherwise be burned. I'll compromise and estimate using the following assumptions: 20% of the workforce can be incentivized, cajoled, coerced, etc. into carpooling with one other commuter; each drives a vehicle with the average fuel economy of 22.4 m.p.g.; they carpool 60% of the time because, for one reason or another, schedules won't allow it two of the five typical weekly workdays. This would mean that we'd take 10% of the commuting work force out of their own vehicles 60% of the time, thus reducing commuting miles by 6% and saving (using the numbers from the previous paragraph) ~1.670*10^{9}~ (1.67 billion) gallons of fuel distilled from ~8.790*10^{7}~ (87.9 million) barrels of oil annually.

Succeeding in accomplishing both of these (difficult but not impossible, in my opinion) measures would yield an annual savings of ~1.062*10^{8}~ (106.2 million) barrels. Here we find that, in 2009, the U.S. consumed 18.69 million barrels of oil per day, so had we accomplished the steps above that year, we'd have saved sufficient oil for 5 days and 16 hours. Let's call it 1.6%.

Okay, neither of these will get us to the promised land. Let's skip strategy 3 for the time being since the ambiguities surrounding this deserve a post all their own. Strategy 4 holds significant promise. My Lexus CT200h, driven as I drive it, achieves better than 51 m.p.g. Its EPA estimate is 42 m.p.g. combined city and highway. There are several vehicles with EPA estimates in excess of 40 m.p.g., and a few in excess of 50. At their present market penetration, I won't include the Nissan Leaf, Chevy Volt, Honda Fit, Coda, etc.

Let's assume that, in a period of a very few years, we can raise (again, through incentives as mentioned above) the average commuter m.p.g. from 22.4 m.p.g. to 35 m.p.g. In such a case, the ~2.783*10^{10}~ gallons of fuel burned would annually would be reduced to ~1.781*10^{10}~ gallons, saving ~1.002*10^{10}~ (call it 10 billion) gallons of fuel, that would otherwise have come from ~5.271*10^{8}~ (527.1 million) barrels of oil. That's enough oil for 28 days and 5 hours at the daily consumption rate from 2009. Let's call it 7.7%.

Finally, what about driving more slowly (and other non-extreme fuel efficient driving methods)? I do about 21% better than the EPA estimate, but let's assume that traffic laws, incentives, etc. can cause the average commuter to exceed EPA estimates by 10%. Calculating as above, I determine that, annually, we'd save ~2.526*10^{9 }~ (2.526 billion) gallons that came from ~1.329*10^{8}~ (132.9 million) barrels of oil. This represents about 1.9% of our consumption.

We can't simply sum these numbers since that would double count some undetermined amount of people who, for example, carpooled, got more efficient vehicles, and drove more efficiently. Cars that aren't on the road due to carpooling can't be driven more efficiently!

So let's arbitrarily take 25% off of the total. We can thus conclude (very roughly indeed) that these (relatively) painless steps could save us something like 590 million barrels of oil per year. This amounts to a bit under 9% of our annual consumption. This is really not so bad, considering that it's only one component of the efficiency possibilities at our disposal.

Update: The 590 million barrels of oil saved by not burning 11.2 billion gallons of gasoline and kerosene would result in NOT emitting about 210 billion pounds or 105 million tons of carbon dioxide.


Gabriel Grosskopf said...

I agree with your analysis, and in addition we can reduce oil usage a lot by switching more vehicles from using gasoline to Natural Gas

King of the Road said...

Yes, this is a topic I'm currently looking into. Thanks!

Bryan Lawrence said...

Telecommuting may be even worse than you calculate. Heating/cooling a house to support the telecommuter may be worse than the travel in some circumstances.

Rob Ryan said...


True enough in this day and age of two income children in day care/school families. I suspect though that, given the number of households that have someone there all day and adding those households where the programmable thermostats aren't used, there's still a significant net savings for telecommuting.

And, of course, the more efficient the house (in terms of passive heating and cooling, etc.) the less the loss from the telecommuter being at home.

Well worth evaluating though, thanks.