Man Bites EV Will EV Bite Back? Do the Math

5 Апр 2014 | Author: | Комментарии к записи Man Bites EV Will EV Bite Back? Do the Math отключены
BAIC E150 EV Electric Cars

Man Bites EV: Will EV Bite Back?

Electric Car: They Might Be Giants

Some time ago, the Chevy Volt attracted my attention. I think the plug-in hybrid concept hits the sweet spot for American drivers, and the Volt s 35–40 mile electric-only range seemed to be the perfect number. A pure electric vehicle (EV) would not permit my wife s periodic work-related jaunt to Pasadena, so any battery-powered solution for us must be of the plug-in hybrid electric vehicle (PHEV) variety. The problem, ultimately, was the high price tag (and the hump in the middle of the back seat occupied by the battery).

Although I don t self-identify as being in the upper class, our income edges us into the top quintile in the U.S. So for us to decide that the Volt costs too much—despite genuine enthusiasm—seemed to spell trouble (indeed, the average income of Volt owners was claimed to be $175,000 ). My conclusion was that electric/plug-in cars are out of reach, and could well remain so.

In April of this year, I became aware of the Ford plug-in, called the C-Max Energi (yes, with an i at the end!). The C-Max Energi has a 21 mile electric-only range, and gets an EPA rating of 43 miles per gallon (2.3 gal/100 mi; or 5.4 L/100 km). The price tag is approximately $6k cheaper than the Volt, and the back seat passed my wife s approval.

Nonetheless, after carefully considering the C-Max Energi as a replacement for our increasingly ailing car, we decided against springing for one: still too expensive. I was all set to write a Do the Math post to the tune of Almost bit on a PHEV again.

But the fact remained that our 11-year old 28 MPG car (bought used) has been costing us a fair bit in maintenance, its reliability increasingly dubious. Replacement loomed. Motivated by an upcoming long-haul road trip, we explored options again, looking at hybrids and the C-Max Energi.

In the end—aided by a federal tax credit, a California rebate, and an unfathomably good offer that together knocked $9k off the MSRP—we drove an Energi off the lot under battery power.

It turns out that:

the lifetime cost for the PHEV is still higher than other options we considered, but not prohibitively so given credits, rebates, and discounts;

the CO 2 emissions are cut in half in electric mode (considering upstream electricity production in our region);

batteries still stink compared to liquid fuel, and likely always will.

EV Pro or Con? Decide, Dammit!

I remain skeptical that EVs or PHEVs will capture a large fraction of the U.S. market share. Yet I just voted with my own dollars to get one. Does this make me a hypocrite?

A double-talking, contrarian, dirty hippy? Not in my view, naturally. I m a very unusual consumer: hyper energy-conscious, generally frugal despite a relatively high-income, but all the same prone to take on energy-related hobbies that may not be a win in the strict financial sense. In this case, $3750 of federal tax credit, $1500 from California, and $4000 off the MSRP (corresponding to a shocking $2000 below invoice price) conspired to make the choice attractive and affordable. But these three discounts do not speak to the steady state fate of EV cars.

The first two will expire at some point, and the deep price drop likely signals a panic from Ford responding to disappointing sales numbers that could portend doom and lost investment for the C-Max Energi line. These cars won t be sold indefinitely at a loss. So I bought the car under highly unsustainable pretenses.

Optimistically, maybe the incentives provide a necessary kick start while EVs become cheaper. Time will tell.

So far I am very pleased with the car: no cut corners, as far as I can judge. Around town, we basically have a pure electric car, but also have executed a very enjoyable 3,000 mile roadtrip. I m swimming in interesting data, and appreciating transportation through new eyes.

But the fact that I now own a PHEV is not enough to transform me into an unabashed supporter, as often happens to early adopters. EVs are not the cheapest option: even just on the fuel front. With $4/gal gasoline and $0.15/kWh electricity, a half-and-half electricity/gasoline mix is neck and neck with a Toyota Prius getting 50 MPG.

Add the initial battery cost and we more than wipe out the marginal savings in the cost of propulsion. I came under serious fire from Volt owners for once suggesting that the financial savings were a wash, or even—heaven forbid—negative. I get it: the emotional investment is large, and it s hard to remain objective after spending $40,000.

I will personally strive to steer clear of the attachment bias, and remain objective about the merits of electric cars.

I should also point out that making estimates of propulsion costs over the next 10–15 years is very difficult, because it is not clear whether gasoline costs increase or decrease over that timeline. Long term, they are almost certain to rise. But a spurt of fracking-produced oil—even if a limited-time offer—may hold prices down for a while.

Meanwhile, slowly transitioning our electricity infrastructure to less carbon-intense forms, which I am all for, may drive electricity costs up.

Still, as I often find, applying a strict dollars-and-cents assessment imposes a terribly narrow window on the world. There are plenty of other reasons that I was attracted to a plug-in, even if it winds up costing me more money in the long term. Why do I have an off-grid photovoltaic system (with expensive, disappointing batteries)?

Or a whole-house energy monitor. Or a 600 gallon (2300 L) rain catchment system? Or three chickens in the backyard? None of these choices are primarily financial in nature.

The enjoyment I get out of quietly tooling around town, logging charge and mileage data like a madman, and developing the capability to self-charge off my own roof (even if the grid is down) offer recompense. Part hobby; part practical; part hedge against an uncertain future.

We ll get back to some basic EV math in a bit. First, we ll take a detour into environmental factors.

CO 2 Emissions

While climate change is not a primary motivator for me (resource depletion, growth reliance, and fossil-fuel dependence in general are my main concerns), I do take it seriously. If I m unjustified in worrying about a resource crunch on a shorter timescale, and we therefore continue profligate consumption of fossil fuels, then climate change is there to make sure we get bitten either way.

So on that count, I am happy to report that driving the C-Max on electricity (in California) produces less than half the CO 2 that driving the same vehicle in hybrid (gasoline) mode. In fact, California analyzed different fuel sources for light-duty vehicles, finding that gasoline produces 96 units of CO 2 to the electricity mix value of 41.

From California Transportation Study. Don t expect many cars to run on forest waste or landfill gas: electric drive is the best scalable option on the graph.

If I use the window sticker values for the C-Max, driving 100 miles consumes 2.3 gallons of gas, or 34 kWh of electricity (from the wall outlet). Gasoline—including refinement costs—produces 12.6 kg of CO 2 per gallon (96 g/MJ), while the California mix of electricity comes in at 0.446 kg/kWh of delivered energy (about a pound per kWh: numbers from here ). So 100 miles of driving the C-Max on gasoline emits 2.3×12.6, or 29 kg of CO 2 . while the electric option yields 34×0.446, or 15 kg.

Another triangulation comes from a handy EPA site that lets you determine your local electricity mix (by zip code), along with a figure for carbon intensity. The national average electricity is 44.5% coal, 23.3% natural gas, 20.2% nuclear, 6.8% hydro, 3.6% non-hydro renewables, and 1.1% oil. That amounts to about 70% from fossil fuels.

For California, it s 7.3% coal, 53% natural gas, 14.9% nuclear, 12.7% hydro, 10.1% non-hydro renewables, and 1.4% oil, totaling 61.7% fossil fuel (dominated by less carbon-intense natural gas).

San Diego electricity sources compared to national average (EPA site ).

San Diego s electricity cost in emissions, compared to national average (EPA site ).

The site puts the CO 2 intensity at 1216 pounds/MWh nationally, and 659 lb/MWh in California. I was also interested to see that despite a 46.5% hydroelectric contribution, Washington State has a CO 2 intensity of 819 lb/MWh: larger than California, owing to a 30% coal dependency.

At the EPA rating of 34 kWh/100 mi, 1 MWh would propel the C-Max Energi 2940 miles. The same car gets 43 MPG on gasoline, so that this trek would require 68 gallons of gas, producing 860 kg of CO 2 by our previous conversion, or 1900 pounds. This suggests the amount of CO 2 produced by gasoline is 2.9 times higher than by electricity in the same car.

The disparity between the two estimates stems from the fact that the California government puts the CO 2 intensity of its electricity at 124 g/MJ, translating to 980 lb/MWh—50% higher than the EPA number.

BAIC E150 EV Electric Cars

In either case, it is clear that driving a car on electric propulsion can offer a net savings in CO 2 emissions—especially in California. Picking on my home state of Tennessee, obtaining 59% of its electricity from coal (and only 9% from hydro, despite the Tennessee Valley Authority system of dams) puts its carbon intensity at a little more than double that of California. In such places, it s questionable whether electric drive produces a net CO 2 benefit.

In places like Wyoming, Kansas, and Missouri, it is decidedly worse to tool around in an EV powered by utility electricity, from a carbon standpoint. The national average carbon intensity is 1.84 times the California value, according to the EPA. Here, too, the question of net benefit becomes mushy.

One lesson is that it may be wiser to drive toward low-carbon sources before driving the country on electric cars.

Other Pollutants

While power plants do nothing to capture CO 2 emissions at present, they do tend to be proficient at scrubbing other pollutants, like nitrous oxides (NO x ) and sulfur dioxide (SO 2 ) from the exhaust stream. Catalytic converters in cars achieve some reductions (on NO x ), but we can t expect a compact, lightweight, mobile device to perform as well as a giant piece of fixed infrastructure. The EPA site also presents intensities of these two pollutants stemming from regional electricity production (in graph above). Here, California shines again: for NO x . the national average is 1.12 pounds per MWh, while San Diego gets 0.42 pounds per MWh.

For SO 2 . it s even better: 0.18 lbs/MWh in California vs. a national average of 3.08.

On the flip side, the manufacture of EVs and PHEVs incur greater energy costs than do conventional cars, and also employ rare earth elements in the motors and involve caustic chemicals in battery production. A recent article in IEEE Spectrum surveys studies that put the net environmental impact of EVs slightly worse than that of conventional cars—despite achieving CO 2 reductions in propelling the vehicles. I have not personally delved into the numbers and analysis, but the result is credible. Assuming the conclusion applies to the national average electricity mix, the fact that California undercuts the national average CO 2 emissions by nearly a factor of two (and even better on other pollutants) means that EVs in California are very likely still a net environmental win—although not dramatically so.

This again illustrates the importance of switching our electricity supply before (or at least in tandem with) large scale adoption of electric transportation.

Batteries Stink

I have warned before that electric vehicles are not obviously going to provide a viable large-scale path away from fossil fuels. In a connected vein, I have also expressed disappointment in batteries in general. Have I softened my stance on batteries?

Am I endorsing EVs as the right way to mitigate our future challenges? Mostly, my answer is no.

I don t hold out tremendous hope that electrified transport can smoothly replace our fossil fuel dependence. The energy density of batteries remains disappointing; most people are priced out (incentives help, but are temporary); recharging is slow and often inconvenient. What follows is some basic EV math exposing some of the hurdles.

EV Math

To illustrate some of the challenges facing electric cars, let s consider parameters that most Americans would find to be acceptable as an equivalent trade. We ll imagine a car that can drive a range of 300 miles (480 km): comparable to typical gasoline car ranges. Impatient Americans would like to recharge in five minutes or less.

Let s impose some hardship and say it ll take a whole ten minutes to charge and then evaluate some of the fallout from these choices.

Charge Power and Thermal Limitations

Firstly, a person filling a gasoline tank at a rate of 0.1 gal/sec (topping off a typical tank in about two minutes) is delivering energy to the car at a rate of about 13 MW . Think about this. That s 2,000 homes running air conditioners. Two people filling up at a gas station reaches parity with the UCSD campus electrical power demand.

Right away you see the problem with transferring electrical energy to a car at similar rates.

But let s get back to numbers more relevant to EVs. A 300 mile range will require approximately 80 kWh of on-board battery storage. This is based on typical EV performance demanding about 33 kWh from the wall to propel the car 100 miles (characteristic of Tesla, Leaf, Volt, C-Max, Prius; see table below . and post on EV energy efficiency ), so that 300 miles demands 100 kWh from the wall outlet. At 80% charge efficiency, the battery holds onto (has a capacity of) 80 kWh. Delivering 100 kWh in 10 minutes (one sixth of an hour) demands a charge rate of 600 kW.

That s serious. We re talking about a 2500 amp breaker at 240 VAC. Not in my house! Upscale neighborhoods beware of Tesla-induced brownouts

BAIC E150 EV Electric Cars
BAIC E150 EV Electric Cars

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