Monday, December 08, 2008

Electric Cars vs. Oil in Hawaii

Ever since last week's announcement of a deal to roll out Project Better Place's model for recharging electric cars in Hawaii, I've been curious about how it would work out, if the supplies of new renewable electricity needed to wean the Islands' million or so cars and light trucks off of oil were not forthcoming, or at least didn't materialize as quickly as the company and state hope. If I've done my sums right this morning, it appears that electrifying Hawaii's passenger cars would still save large quantities of oil and reduce greenhouse gas emissions significantly, even if every kilowatt-hour (kWh) to run them was generated from the state's oil-fired power plants.

Since the late 1990s, I've been convinced that in the long run, the majority of cars would be some form of electric vehicle (EV), whether in the form of hybrids, with power generated onboard from engines or fuel cells, or battery EVs tapping external sources of power. The rate at which this transformation takes place, however, remains highly uncertain, with conventional, Prius-type hybrids still accounting for less than 3% of the US car market, and battery EVs other than golf carts as rare as hen's teeth. I've followed the plans of Better Place with great interest, since their mobility-based business model could provide a key ingredient for accelerating the electrification of personal transportation, even while the high cost of batteries makes EVs more expensive to purchase than their gasoline-based competitors.

As Better Place founder Shai Agassi noted in an interview published in Sunday's Washington Post, Hawaii looks ideally suited to be an early adopter of this technology. With no indigenous production, all of Hawaii's oil, including that from which its gasoline needs are refined, must be imported. In that context, the benefits of the Better Place plan look obvious, until you realize that powering a million cars on renewable electricity would require on the order of 3 billion kWh of electricity per year, the equivalent output of more than 400 wind turbines of 2.5 MW each. Ignoring issues of transmission and intermittency, that's about 16 times the state's currently-installed wind power base. Year-to-date through August, 75% of the state's electric power was generated from oil, and less than 7% from various renewables. So at least for now, if this model is going to work in Hawaii, it has to make sense assuming that most of the incremental power for electric cars would be generated from oil.

That sounds counter-intuitive, until you consider the relative efficiencies of centralized power generation versus the gasoline engine under the hood of your car, combined with the inherent efficiencies of electric drive. Comparing the fuel consumed by Hawaii's oil-fired power plants to the power they generated, I found that each gallon of fuel oil yielded roughly 15 kWh of electricity. If the typical electric cars that will be sold in Hawaii travel 3-4 miles per kWh, that equates to an average effective fuel consumption of around 47 miles per gallon, after allowing for 10% transmission losses. That's 43% lower than the 26.8 mpg of the 2008 model year average for the US new-car fleet, and it would reduce greenhouse gas emissions by roughly the same proportion. Although that's no better than the fuel economy of a Toyota Prius, that comparison would improve, as renewable power gradually displaced oil-fired power.

So at least from an oil-consumption and importation perspective, this idea appears to make sense in Hawaii. I can't speak to its economics, or to how practical it is today for regions such as California's Bay Area, where in recent years increasing numbers of workers have been driving in from communities such as Modesto, Tracy and Stockton--commutes that would have seemed unthinkable 25 years ago--in order to beat the high cost of housing near the coast. I wish Better Place well, and I would certainly appreciate having the choice of an attractive, economical electric car, when it comes time to replace my current sedan in a few years.

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