Thursday, December 31, 2009

Cold Discomfort

Forgive the clumsy channeling of the bard but to many it appears that the petrol fueled vehicle's candles are burnt out and the jocund electric car stands tiptoe on the misty mountain top. Yeah well to some of us the pure electric vehicle siren song is one that sings so out of tune, straining harsh discords and unpleasing sharps. The heck with nightingales, I hear only larks.

Outside my window is the salient reason for this grumbling where it is about 10 degrees Fahrenheit and headed to a morning low of about zero. Five hundred miles north of here lows will be closer to minus 10 or 15. In that northern reach January morning lows can easily crack 30 below which sounds even colder in Celsius (-34). In fact the entire northern half of the U.S. can see zero degree F. temps in a given year to say nothing of the entirety of Canada. In Europe just about any place north of the Côte d'Azur can experience winter climes of comparable frigidity.

Here's a statement of surprise to absolutely no one. Batteries hate being cold. They hate it because they produce their energy by means of chemical reactions and virtually every chemical reaction known to science slows down as temperature drops. The more complex the chemistry the greater the effect in general and to make matters worse the more exotic the chemistry the more the range of temperatures over which the reactions are most efficient is narrowed.

The typical conventional lead-acid battery used in vehicles for the last century is normally rated in something called "cold cranking amps" which is the amount of current it will deliver at a temperature of, if memory serves, zero degrees Fahrenheit and at a voltage of 7.2. Most 12 volt automotive batteries used are rated in the range of 600-800 cold cranking amps which sounds like a lot of juice and it is but is necessary because engines are harder to start in cold conditions. Consequently automobiles use a battery which has far more energy than needed to start an engine at mild temps but this is ameliorated by the fact that even large high capacity lead-acid batteries are simple devices and cost, at most, a couple of hundred dollars and their service life is from about three to five years.

The batteries used in hybrids, metal-nickle hydride, and in most upcoming pure electrics, lithium ion/polymer, are not simple devices, at least not chemically, respond poorly to extremes of temperature and contain high fractions of extremely expensive materials. Their percentage loss of capacity in cold conditions can drastically exceed that of lead-acid types and at elevated temps they are quite susceptible to overheating damage. What is not economically practical is to upsize lithium main vehicle drive batteries to account for extreme cold. They are crazy expensive to begin with so whereas increasing the capacity of a lead-acid starting battery is a matter of spending a few tens of dollars more, using the same tactic with lithium main drive batteries would cause costs and weights to soar smartly above their already absurd price levels which are in the ten to fifteen thousand dollar range.

Large lithium main drive battery packs, which perform well at 40-90 degrees Fahrenheit, can lose as much as 75 percent of their capacity at 0 degrees which converts a fair weather range of 100 miles to a frustrating 25 or 30 miles or even less. Most likely less because an internal combustion powered vehicle can use the waste heat of its engine to warm its occupants whereas the only source of heating energy in a pure electric vehicle is its main battery. And heating a cabin at sub-zero temps takes a lot of energy. It may well take as much energy to heat the cabin as it does to push the vehicle down the road making a poor situation pathetically worse. When temps approach or sink past 20 below, common in the upper plains, a pure electric vehicle might not get you out of the driveway let alone to work 10 or 20 miles away.

If the vehicle is parked overnight in a heated garage then the picture changes somewhat but if heated parking is not available at your workplace then your chances of getting home are slim unless you can plug in at work. Even then if your commute is much above 20 miles and the temps are not above zero you will be in trouble. A way around this is to have battery heating systems that operate concurrently with charging but in bone-chilling climes this will use large amounts of juice the cost of which will leave you, and your employer, rather less than thrilled.

Conventional liquid fuel powered vehicles also lose efficiency in very cold temps but only to the tune of a few percent so your range will be far less affected than will be the case with electrics. All in all pure electric vehicles will simply be unusable in very cold climates essentially ruling out sales above, (north) and below (south) about 35 degrees latitude right around the earth. That's one heck of a market slice to be unable to service and the long term viability of a vehicle only useful in very temperate climes is seriously questionable. Electric vehicle sales and usage will be a Sunbelt phenomenon, if even that. Even in San Francisco which has a climate operationally and politically friendly to electrics an owner will be essentially confined to the western edge of the Sierra Nevada only a hundred miles away.

A blue sky solution to some of these problems is promised by the advent of devices known as ultra-capacitors which are units that store electrical energy in a non chemical manner and are thus less subject to the vicissitudes of climate. They are as yet significantly less energy dense than lithium batteries so significant weight penalties are incurred in trying to match lithium storage capacities. They are consequently more expensive than lithium cells on a capacity basis but they do have the advantages of very rapid recharging and significantly better performance in cold weather. Ultra-capacitors can be utilized very effectively in energy recovery and acceleration boost scenarios, thus working satifactorily in some hybrid designs, but in terms of primary energy storage they are to date not a viable alternative.

All putative pure electric drive systems, of whatever capacity or capability, all suffer from having only the main battery pack to power not only its drive motors but to also provide power to the increasingly long list of electronic gizmos that clutter the dashboards of modern cars. They all take energy although usually not nearly the large amounts that heating and air conditioning do. Speaking of which AC will require not merely energy from the main battery but an additional electric motor in the range of three to five horsepower will be needed to power the compressor. Lithium cells tend to get very hot in heavy use so most vehicles, the Chevy Volt for example, will have onboard systems to cool the batteries in hot weather/heavy use modes lest the packs drastically overheat and catch fire. Those factors will be the Sunbelt bugaboos analogous to the Snowbelt blues.

The much ballyhooed Volt is not a pure electric vehicle. It's design template utilizes, requires really, an internal combustion engine to take up where the largish battery pack leaves off and by all reports it does this seamlessly with little or no driver input. It really should be thought of as the first "strong" hybrid design from a major manufacturer as opposed to "weak" or parallel designs from Toyota, Honda, Ford, etc. GM's biggest problem with the Volt may well be brisk sales for even with the absurd government subsidies they will not for a goodish while be able to make a profit on the vehicle. Even Toyota found profits elusive with sales of its Prius for several years, due its pre-recession overall profitability, but GM is hardly in a position to do likewise.

Do not look for battery prices to come down by very much. They will continue to increase in capacity at a given weight over time but since this will require ever more advanced technology being applied to them cost reductions are unlikely. Not impossible understand just extremely unlikely. Big advances and large cost reductions have been "just around the corner" for over a hundred years so don't expect quick results however impressive the vast heaps of cash flung at the problem by the government.

And no a putative "Manhattan Project" style approach will not really help. The Manhattan project was not about figuring out how to build a bomb, that was already largely in hand. It was primarily about quickly ramping up the huge industrial infrastructure to manufacture the large amount of fissile material needed in the construction of the weapons. This is not the case with battery technology. We don't already know how to build batteries with capacities that would allow electric vehicles to match conventional vehicle ranges and to charge as rapidly as filling a fuel tank from a pump, in any climate, and to not weigh a bloody ton or cost a stinkin' fortune.

We don't know yet what tech, if any, will allow this to happen and if it somehow does then the manufacturing infrastructure will doubtless take years to put in place. Remember that the Manhattan Project was very nearly a cost-no-object enterprise undertaken in response to an enormously threatening global conflict prosecuted by fanatically led industrialized nations. Sorry to break the news but a fecklessly quixotic "Saving the Planet" project simply does not qualify as a crisis in remotely the same sense that imminent national annihilation does.

So knock yourself out bud. Spend that 30 or 40 gees on that seductively subsidized electric icon worshiped by the grand universal eco-church but don't call me for a ride when the blizzards howl or old Sol bids fair to melt the pavement. Your mocking laughter when you pass the saps at the gas pump in clement weather will ring most hollow then old man. Oh what sweet schadenfreude it will be to me and to thee will be old Will's richly deserved "cold comfort".


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