Thursday, July 26, 2012

12 August 2011 – Charged up


The Ontario government announced this week that it would invest $80M in charging stations for electric cars.  Around about the same time I came across a few articles on electric vehicles that caught my eye, and that engendered a little arithmetic.

According to the NRCAN 2007 Canadian Vehicle Survey, in 2007 there were 19,003,427 “light vehicles” (cars and trucks) on Canada’s roads (more than one third - 6,957,086 - in Ontario alone); 392,608 medium trucks; and 314,877 heavy trucks.  A “light vehicle”, by the way, is defined as any vehicle with a gross weight of less than 4.5 tonnes.  The vast majority of light vehicles (18.3M) are gasoline powered; most of the rest are diesel-powered, and a small percentage (64,587, or 0.35% of the total) use “other” fuels, principally propane.

In 2007, Canada’s light vehicles travelled 300,203,000,000 km (300 billion kilometres).  To do so, they burned 31,305,000,000 litres of gasoline and 1,291,000,000 litres of diesel, racking up average fuel consumption rates of 10.8 litres of gasoline, or 12.3 litres of diesel, per 100 km travelled.  Gasoline contains 34 Mj/litre, so on average, light vehicles in Canada used 34 x 10.8 / 100 or 3.672 Mj per km travelled.

The Chevy Volt has a 200-kg lithium-ion battery that according to GM literature gives the vehicle an electric-only range of 25-50 miles “depending on terrain, driving techniques and temperature”.  The battery holds a maximum energy charge of 16 kWh, or 57.6 Mj.  At maximal charge-to-power performance, this means that the Volt uses 0.720 Mj/km; and at minimal charge-to-power performance, twice that, or 1.44 Mj/km - in other words, somewhere between one-quarter and one-half the energy required by light vehicles powered by internal combustion engines.  Clearly, EVs are more energy-efficient than IC vehicles.  No surprise there; electric motors have always been more efficient at turning input into output.*

Of course, the Volt figures are theoretical numbers provided by the company that makes them, while the NRCAN figures are actual statistical numbers gathered from huge amounts of empirical data.  Moreover, the “light vehicles” category includes many vehicles that the Volt cannot compete with - e.g., SUVs, pickup trucks, minivans, larger vans, construction trucks, cube vans, and other vehicles with significant passenger and/or cargo storage space.  In terms of size and passenger capacity, the Volt is more comparable to, say, a Nissan Sentra, which according to the manufacturer gets 34 mpg or 6.96 litres per 100 km (which translates to 2.36 Mj/km).  So in other words, the Nissan Sentra uses somewhere between 1.6 and 3.2 times the energy per unit of distance travelled as the Volt does. 

Of course, with a 55-litre tank the Sentra has an unrefuelled maximum range of 788 km, which is ten times the Volt’s maximum 80 km range.  In order to manage the same range as the Sentra on battery power alone, the Volt would need 2000 kg of batteries instead of just 200 kg, which would degrade vehicular performance and take up a lot more space - more space, in fact, than the vehicle has.

It would also have an impact on charging time.  According to company literature, the Volt takes 10-12 hours to fully charge from a 120-Volt charging station (the charging time can be compressed to “about 4 hours” by using a special-purpose 240-Volt charging station).  Assuming zero losses (unrealistic, I realize, but we’re modelling here, not measuring), taking 10 hours to put 16 kWh into a battery pack means that you’re adding 1.6 kW to your household current load for that entire period.  That’s about the same draw as running an electric kettle, a curling iron, or a 3-ton air conditioner for 10 hours straight.

That’s not the way to look at it, though.  Returning to the NRCAN data, if there are 19M light vehicles driving 300B vehicle-km, then that’s an average of 15,789 km per light vehicle per year.  That’s 57,977 Mj in gasoline, at the 10.8 litres/100 km cited above for light vehicles (not at the lower Nissan Sentra rate).  If those vehicles were all Volts, that 15,789 km per vehicle would translate to an absolute minimum (assuming perfect performance, no losses, no overcharges, and no deleterious effects to performance from “terrain, driving techniques or temperature”) of 197.36 full 16 kWh charges.  That equates to 197.36 charges per vehicle x 16 kWh per charge x 3.6 Mj per kWh = 11,368 Mj per vehicle.  In theory, therefore, swapping out all the light vehicles in Canada for Volts and running the volts solely on electric power would result in an energy savings of something like 80%.

There are, of course, a couple of problems with these calculations.  Among them are the fact that Volts aren’t trucks; that without burning fuel, they can’t go further than a maximum of 80 km unrefuelled; that their total cargo capacity is 200 litres (about one-fifth of your average SUV, to say nothing of pickup trucks); and that their performance (especially battery performance) in Canadian weather conditions is, shall we say, somewhat less than the company claims.  But put all that aside for a moment and consider only the question of electric power. 

Suppose Ontario’s fleet of 7M light vehicles consisted of all-electric vehicles like the Nissan Leaf. The Leaf has a battery capacity of 24 kWh and a claimed range of 160 km.  Because each light vehicle in Canada drives an average of about 16,000 km/year, assuming perfect performance and no losses, each Leaf would require 100 full charges, or 2400 kWh, or 2.4 MWh per year.  Charging those vehicles would consume 16,800,000 MWh, or 16,800 GWh, or 16.8 TWh.

Ontario Power Generation, which generates about 70% of Ontario’s electricity, produced 88 TWh in 2010.  The total output of all of its hydroelectric generating stations last year was about 30 TWh; and the total output of all of its nuclear plants was about 45 TWh.  What’s most interesting, though, is that the total output of OPG’s thermal generating stations in 2010 was 12.2 TWh - which is about two-thirds of the amount of power necessary to support a province-wide switch to electric vehicles.  It’s also the generating capacity that the Ontario government plans to close by 2014.  Not to put too fine a point on it, but it’s a little odd to be simultaneously spending money to build electric car charging stations at the same time you’re reducing the amount of the electrical generating capacity you need to charge them with.

Lest you think I’m pounding unduly on Ontario, the situation in the US is far, far worse.  The EPA has issued MACT - Maximum Achievable Control Technology - regulations that come into effect on 1 January 2012, and that will essentially price coal-fired generation out of the market, leading to colossal underproduction of electricity and the loss of hundreds of thousands if not millions of jobs, especially in places like Indiana, which obtains 95% of its electricity from coal.  Not to put too fine a point on it, but perhaps folks should have listened when Obama promised during the campaign that he would bankrupt coal-fired generating stations.  He intended to do it through carbon trading, of course; but since his legislative efforts in that direction failed in Congress, his EPA is doing it through regulatory action.  The US government is of course still subsidizing purchases of hybrids and EVs; it’s just not clear what folks are going to use to charge them.

The bottom line is this: electric vehicles are the future, because they are at a minimum twice as energy-efficient as IC engines, and because we have 8000 years’ worth of uranium (and a virtually infinite supply of fuel for thorium-based reactors).  But the future isn’t here yet.  It took over 40 years to get the internal combustion engine-powered private automobile from a curiosity to a useful consumer product, and 80 more to turn it into the reliable, low-cost, fuel-efficient piece of awesomeness that it is today.  Electric vehicles are actually older as a concept than IC-powered cars, but due to slow advances in battery technology, they haven’t benefitted from more than 100 years of market-driven innovation.  Also, the infrastructure to support EVs simply does not exist, and creating it will take decades and literally hundreds of billions of dollars.  The IC automobile was not a government project, and its replacement by EVs cannot be imposed by government fiat - it’s as simple as that.  The market - which is to say, consumers - will decide when it’s time to switch, and the switch will take decades.  Attempts by governments to accelerate the process, either through punitive taxation on conventional vehicles (did governments impose a punitive tax on horses in the 1890s and 1900s to force people to switch to cars?) or by using taxpayer money to build infrastructure that the market has no incentive to create, will be a waste of money at best, and will impede the process at worst.

Okay, enough of that.  Two more interesting and related points.  The first is that electric and hybrid vehicles respond very differently from conventional internal combustion engines when they run out of fuel / battery power.  These two articles make interesting reading for anyone who’s ever poked around under the hood of a car.

As the author of the articles makes clear, advertised charge times and operating ranges are a little squishy, and when your EV flatlines on the highway, you can’t just catch a lift to the nearest charging station for a one-gallon jerrycan of electrons.  As for California’s solar-powered EV charging stations, it’s worth recalling where the Sun usually is when you have the time to park your car for a 10-hour charging cycle.

Second, here’s a link to a paper that warns about what might happen to electricity grids under real-time pricing:

Don’t bother with the equations; just flip to the conclusion, which states that “As the penetration of new demand response technologies and distributed storage within the power grid increases, so does the price-elasticity of demand, and this is likely to increase volatility and possibly destabilize the system under current market and system operation practices.”  In other words, once you can set all of your appliances to operate after the rates go down, the demand during “cheap time” will increase, necessitating altering the generation schedules and, therefore, increasing prices during the new demand time.  And just imagine what happens when a significant fraction of the population comes home from work at 1800 hrs and plugs their 4-wheeled, 2400-Watt EVs into the wall, all at the same time.  Or, alternatively, when everyone sets the charging to begin exactly at 1900 hrs, just as the rates go down. 

EVs that will offer a genuine, comparable, cost-effective alternative to conventional IC-engine vehicles are coming.  They’re just not here yet.



*The calculus changes if you factor in the cost of burning fuel to generate electricity to charge an EV’s batteries.  I’ll save that discussion for another day, though.