Baby, It's Cold Outside

Haven't updated on the Leaf recently. Sparkii continues to plug along, doing duty as our primary vehicle. He takes my wife to work, my son to school, all of us to the store. Power consumption is beginning to climb as the temperature begins to drop. Here's a chart showing how driving range has varied with temperature over the past 11 months:

So what's going on? Is the cold affecting the battery? Are EVs a failure in freezing temperatures? Not really. Thinking outside the box just a bit, cold storage facilities use electric forklifts. And it gets a lot colder inside a meat locker (-35C) than it does around here. So what is it? It's the heater:

Internal combustion engines are notoriously inefficient. Only 20-25% of the energy from gasoline goes into moving the car forward. The rest is turned into heat. As I'm fond of saying, "gas engines are an 80% efficient furnace that provide locomotion as a by-product".

Not so with electric motors, I'm afraid. On the plus side, a typical electric motor converts 90% of input energy into motion. On the minus side, there is almost no waste heat to keep us comfortable on frosty mornings. So we have to dip into our precious stored electrical energy to heat the car. You can see from the chart above that as the temperature has dropped, our accessory (non-motor) consumption has climbed from the low single-digits to nearly 25% of the total.

Still, I prefer having an efficient electric motor and being in control of our energy/comfort trade-off. We can always follow President Carter's advice and put on a sweater.

August Leaf update

	Odometer	Miles	Kwh	Mi/KWh	Cost	Per mile	MPGe	Temp(F)
March 2011	2118	650	208	3.1	$24.13	$0.037	105.3	45.1
April 2011	2958	840	272	3.1	$31.55	$0.038	104.1	45.5
May 2011	3570	612	185	3.3	$21.46	$0.035	111.5	52.3
June 2011	4259	689	177	3.9	$20.53	$0.030	131.2	59.4
July 2011	4911	652	173	3.8	$20.07	$0.031	127.0	64.2
August 2011	5664	753	194	3.9	$22.50	$0.030	130.8	66.0

This will probably be the last Leaf-focused update for a while. Owning the first mass-market electric vehicle has been far less dramatic than anticipated. Another month gone by without stalling out on the highway, exploding in flames, or blacking out the neighborhood. I keep looking for an excuse to visit the dealership, just to say "Hi". But our first scheduled service isn't for another 5 months, and that's to rotate the tires and change the cabin air filter.

So, is the Leaf the perfect car? Any vehicle is a compromise. We're limited to 100 miles before a lengthy recharge, we can't tow a boat, or haul 20 bags of compost home from the nursery. But we can do pretty much all of our everyday driving without burning fossil fuels. Think about that as information about the Keystone pipeline and the Alberta tar sands begins to hit the mainstream media. Do you want to continue to be part of the problem, or do you want to be part of the solution?

Range Anxiety

Photo by: Chandra Ramkumar

Another uneventful month of EV driving. Total mileage was down slightly to 650. Electric consumption was also down, to 173 Kwh, for an average of 3.8 miles per Kwh. I think we crossed the line from heating to cooling, and running the A/C a few times has increased our e- consumption slightly.

Did have one episode of range anxiety this month. No, not in the Leaf. It was in my daughter's Toyota, driving back from Arizona. Getting on towards nightfall, running low on fuel. That's when I realized we were on a stretch of freeway without any services. How many miles of range did I have left? How far to the nearest gas station? Oh, if only I had a telematics system that could tell me these things. Then maybe I wouldn't feel so anxious.

The story has a happy ending, but just barely. We found the only gas station in a 110-mile stretch. It was still open. We filled the tank, and they promptly shut down for the night.

June recap

	Odometer	Miles	Kwh	Mi/KWh	Cost	Per mile	MPGe	Temp(F)
March 2011	2118	650	208	3.1	$24.13	$0.037	105.3	45.1
April 2011	2958	840	272	3.1	$31.55	$0.038	104.1	45.5
May 2011	3570	612	185	3.3	$21.46	$0.035	111.5	52.3
June 2011	4259	689	177	3.9	$20.53	$0.030	131.2	59.4

Well, it's definitely heating up around here. Average temperatures have nearly broken the 60-degree barrier. Time to break out the cargo shorts. Just over 4000 miles on the Leaf and no issues to report. Deliveries of the Leaf are starting to heat up as well.

So why have I made three references to temperature? Look at the right-hand column in the table. I started tracking mean monthly temperature. With only four data points, it's not statistically rigorous, but there appears to be an linear relationship between MPGe and temperature, with a coefficient of 2.25 (ie Multiply temperature by 2.25 to get MPGe). Check back here in July and August to see if it holds.

May Leaf Update

Nearly another month of driving with electrons. May's not quite over yet, but I have time to post this morning so here goes. In the first 27 days of May, we've put 568 miles on the odometer and 172 KWh on the emeter, for an average of 3.3 miles/KWh. Up slightly from March and April, when we averaged 3.1 miles/KWh. It's getting a bit warmer, so we're using the heater less.

I also started tracking MPGe, the EPA's fuel efficiency metric for EVs. According to the EPA, a gallon of gasoline contains the equivalent of 33.7 KWh of energy. If you disregard how each is produced (more on that later), it gives a like-for-like comparison between gas-powered vehicles and EVs. For March and April, we averaged right around 105 MPGe. With the arrival of (slightly) warmer weather, we're now up to 111 MPGe. Using that same 33.7 ratio, our fuel cost us the equivalent of $3.90 per gallon, or about 3.5 cents/mile.

Something I've blogged about before, but bears repeating: lack of volatility in fuel prices for EVs. Electric rates are typically controlled by a public utility commission. They go up (and down), but on a timescale of months or years, not days. Since we got the Leaf, our fuel price has not changed. In that same time, gasoline has gone from $3.20 to $4.10, and is now back down to $4.00

What good is an electric vehicle if all it does is move CO2 emissions upstream to a coal-fired power plant?

Answer: It doesn't. Let's start with "base load". Coal, nuclear, and hydroelectric are all base load sources of electricity. Utilities use base load power to service the typical needs of their customers. Utilities keep base load plants running 24x7 whether they need the electricity or not, because they can't be started or stopped quickly.

So what type of power is used to recharge EVs? Most EV owners plug their cars in at night, when overall demand for electricity is low. They make use of capacity that would otherwise go to waste. Remember, base load plants run 24x7, producing CO2 whether or not they're generating electricity. EVs are an option for turning the waste CO2 into something useful.

Finally, sources of electricity will get cleaner over time. Wind, solar, geothermal, tidal are all means of generating electricity without producing CO2. Gasoline will just get dirtier. Deep-water wells, tar sands, oil shale, and coal oil are all methods for squeezing out the last drops of fossil fuel, but at an ever-increasing cost to the wallet and the environment.