Zombie Journalism and Electric Cars

Apparently my blog isn't the only thing that has risen from the dead. FastCompany ran an article a month ago about the downfall of one of the companies I worked for: Better Place. The company had folded over a year ago; I'm not entirely sure why now would be a relevant time to discuss them, but I'm glad Better Place is getting talked about again. I had a lot of respect for what they were trying to do, which was to make EVs financially attractive.

Electric cars are remarkable. The powertrain is 80-90% efficient, compared to a gasoline car's 10-20% efficient engine and transmission. This makes a huge difference in operating costs. If you put $20 worth of gas in a 22mpg gasoline car, you'd get 120 miles before the tank runs out [1] at today's gas prices of $3.70/gal [2]. If you put $20 worth of electricity in something like a Tesla Model S, you'd get 670 miles before you run out of juice [3]. Electric vehicles are so economical to run because 1) the powertrain is so efficient, 2) the electricity to run them is so cheap. The problem is the battery is pricy, so even though an EV is less expensive to run, people won't buy them because their upfront costs are too high (consumer discount rates w.r.t. energy efficient appliances, EVs included, is a fascinating energy economics post for another time).

Let's do what Shai Agassi likely did when he decided to found Better Place and look at the economics of EVs relative to gasoline cars. We already did the math saying EVs are about 6x cheaper/mile to run. If we take Tesla's quoted cost of the replacement battery of $10K, how far would we have to drive to make up that cost difference? With $3.71/gal gasoline, $0.10/kWh electricity, a 22mpg gas car vs. a 3mi/kWh EV, it comes out to be about 70K miles: less than the standard lifetime mileage of a car, but not much less. There's a business case to be made, but not much of one given the slim margins.

What about Shai's home country of Israel? Turns out they pay about the same electricity prices as we do, but pay far more than we do for gasoline: $8/gal [4] [5]. That means $20 would only get us half as far: 55 miles in Israel instead of 120 in the US. Taking this into account, we would only have to drive 30K miles to make up the additional cost of the battery. Everything after that would be savings to the customer, or profit to a company. This is a far more promising business case, and indeed it was the case that Better Place was founded on.

The math here is greatly simplified. We simply talk about the marginal cost of the battery pack, when in fact there's other cost differences that bring EVs more in-line with gas car costs. We also neglect infrastructure costs, which might matter if you're trying to build something expensive like battery swap stations like Better Place or superchargers like Tesla. The lessons learned from the exercise don't change though; EVs make sense now, and Better Place wasn't founded on some idealist's whimsical fantasy.

Dead ideas like amateur blogging or voyeuristic post-mortem news articles might keep coming back long after we thought we buried them, but live ideas with a spark in them, like electric cars, will always stay alive and kicking.

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[1] Idaho National Lab vehicle energy cost comparison: http://avt.inl.gov/pdf/fsev/costs.pdf
[2] EIA gasoline costs table: http://www.eia.gov/dnav/pet/pet_pri_gnd_dcus_nus_w.htm
[3] Tesla Model S powertrain specs: http://en.wikipedia.org/wiki/Tesla_Model_S#Powertrain
[4] Israel electricity prices: http://www.eia.gov/countries/prices/electricity_households.cfm
[5] Israel gas prices (surprisingly hard to find): http://www.timesofisrael.com/gasoline-prices-to-drop-slightly-saturday-night/

The Fascinating World of Air Conditioner Efficiency

I was inspired to write about the oh-so-sexy topic of air conditioner efficiency and consumer behavior patters after reading an innocuous article in Slate today (article here). The author, Brian Palmer, did a thorough job of summarizing pros and cons, however (and here's where I think he opened up his article to vehement commentary) concluded that it's difficult to say which method of cooling is more energy efficient.  In fact, window ACs use less energy than central ACs despite lower SEER ratings, but rather than narrowing our focus on trying to criticize a single article, let's open up the discussion a bit, because, surprisingly, we use a great deal of energy just to keep ourselves comfortable.


According to the DOE's Energy Information Administration (probably my favorite reference), Americans used 24.5% of their electricity to keep themselves cool at home [1]. Looking at the US, this accounts for 7% of ALL electricity usage [2]. And the major contributor to AC energy use is central AC systems at 3745 kWh/year vs. 1259 kWh/year for window AC systems. Now, these are just household-level numbers, which don't take into account any confounding variables. One study, by a David Rapson of UC Berkley's Department of Economics, points out that households with central ACs are larger and are in climates with more cooling degree days (see Table 2) [3]. Even factoring that in, window ACs use less energy on a per cooling degree day and per square footage basis by a factor of 1.75. So there you have it: window ACs are better at cooling a space efficiently than central ACs.


But why? Why should window ACs, which have a lower SEER rating, use less energy than central ACs? Murphy's law provides a bit of insight here. Central AC systems are more than just the air handler and compressor that comprises the window AC unit. There's dozens of linear feet of air ducting, an automatic control system, and the whole system has to be engineered and installed by some contractor.  A quick survey of central AC units in Austin, TX by a few University of Texas, Austin engineering students revealed blowers to circulate cooled air were operating too high, unsealed ducts leaking cooled air to the environment, control systems extending operating times, and systems being oversized from specification [4]. The result is a high efficiency compressor but low efficiency ducting and control systems. 


But that only covers energy efficiency. What about consumer behavior? After all, this is a blog about behavior change. Well, the brilliant minds at the EIA have that covered; a section of their RECS questionnaire was about thermostats and usage. Of the 64 million central AC systems, 40 million consumers reported running them all summer, while 11 of the 27 million households that use window AC units report using them "only a few times when needed." And while fewer window AC units had programmable thermostats (only 15%), users simply turned them off or on when necessary. Conversely, 39% of central AC units had programmable thermostats, but 64% of users actually use the programmable thermostats as indicated. 


The bottom line seems to be that households with window air conditioners use them more consciously (and conscientiously) to cool smaller areas within the home, while households with central AC allow their units to run continuously and cool the entire home, whether it's necessary or not. Hence the factor 1.75 lower energy consumption per household for homes that use window AC units vs. central AC units. 


ACs represent an interesting home appliance where improvements in consumer usage behavior can be just as important as improvements in unit energy efficiency. Now it's just a matter of encouraging the right behavior...


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[1] http://www.eia.gov/emeu/recs/recs2005/c&e/airconditioning/pdf/alltables1-11.pdf
[2] http://www.eia.doe.gov/cneaf/electricity/epm/table5_1.html
[3] http://www.econ.ucdavis.edu/faculty/dsrapson/Rapson_LR_electricity.pdf
[4] http://bit.ly/msvo1j (unfortunately, I don't have the full article on this one, just the abstract)

New Building Occupant Behavior Opportunities

An interesting bit of news on the Boston behavior change front: the Boston Redevelopment Authority is interested in pursuing behavior change technologies in two new college dormitories being built in Boston. Berklee College of Music and Boston College are both building new dorms to accommodate their burgeoning student bodies, and Gerald Autler, urban planner and senior project manager at the Boston Redevelopment Authority, wants to design the dormitories with occupant feedback systems in mind from the onset.


I have to applaud his approach. At MIT we were limited in the sense that we had to work with the building infrastructure we were stuck with, but if you can work in occupant feedback systems from the onset, you can make a significantly greater impact. My primary idea was to submeter the electrical systems keeping in mind the way students would socialize, so that any energy monitoring hardware added afterward would reflect the energy usage of a given social unit, rather than an arbitrary group of students. Typically electrical submetering is done just as a matter of convenience: a 3-story building with 2 wings may be submetered at the wings, grouping all three floors together. This isn't ideal, as it's more likely that students would socialize with the other students who share their hallway, rather than those directly above or below them. Submetering to the level of social aggregation makes conservation messaging a lot more effective. 


If I can pull through on the MIT-NSTAR Efficiency Forward campaign's behavior change program, it may be interesting to do some intercollegiate behavior change competitions between MIT, BU, and MIT.