Keeping Electric Cars Moving Even When It’s Cold Out

Battery options, solar roofs, and reimagined interior climate control are all being reviewed as a means to increase the efficiency of electric vehicles in cold temperature environments.
By: 
June 13, 2017

There are many good reasons to build cars that replace a tankful of gasoline with a trunkful of batteries. But as we endeavor to do so, we keep confronting the important differences between the two. Gasoline is energy-dense, concentrated and essentially indifferent to climatic conditions. It can provide a flow of power that is fast or slow. Like a perfect servant, it’s personal characteristics and quirks rarely, if ever, get in the way of doing its job. If only it didn’t give off all those emissions when burned.

Batteries are heavy. They don’t contain nearly as much energy per pound as gasoline does. They lose performance in cold weather. Depending on their chemical characteristics, they can either provide deep energy reserves or short bursts of power, but never both without some compromise.

These are some of the challenges that face Tesla and other companies hoping to fill our highways with electric vehicles. Replacing the millions of gasoline-powered cars with electrics, is going to require a great many batteries.

Tesla ChargingTesla claims they’ve got that part covered. They will support their projected production increase from 104,000 cars in 2015 to 500,000 cars in 2018, with the construction of their Gigafactory. This facility, which is touted to be the largest building in the world, will eventually produce more than 100 Gigawatts (100 million kilowatts) of battery capacity per year.

However, a Tesla Model S, with a range of 206 miles in San Diego on a 70-degree day, will only go 170 miles on a near-zero day in Duluth. This idea of range variability, which is more pronounced in EVs is another aspect of the conversion to EVs that consumers must grapple with.

Clearly the heater drains the battery more than the A/C does, another difference from internal combustion engines. With all of their inefficiency, they produce copious amounts of heat at no extra charge.

What options do carmakers have to address these concerns? Toyota recently announced the addition of a solar roof to their Prius Prime plug-in . While this could be helpful at times, under normal conditions, it will only add a few miles to the vehicle’s range.
 
This NREL study , which found a 20-30% loss of range on a 20-degree day while maintaining a 70-degree interior, evaluated a number of strategies to minimize the impact of vehicle climate control on vehicle range. They found that a combination of heated surfaces (floors and seats) along with zonal air flow were most effective. Their best configuration improved vehicle range by 28.5%.

Another approach described by SAE involves the use of a thermal battery to store heat . A research team from MIT, the University of California at Berkeley, the University of Texas at Austin, worked with engineers at Ford to design and package the system which is said to be capable of 2.5 kWh of cooling and 4.5 kWh of heating.

While called a thermal battery, inside it behaves more like an adsorption heat pump where a working fluid a pumped across a combined condenser-evaporator, giving off or absorbing heat as it

Comments

Battery powered electric vehicles will replace combustion technology when charge while driving highways become available. If there were a charging lane on major interstates that allowed batteries to replenish while on the move then range becomes a non issue. Battery power would only be required for secondary roads ands short haul trips. The beauty is such technology could be rolled out in phases then more segments added over time.

"This facility, which is touted to be the largest building in the world, will eventually produce more than 100 Gigawatts (100 million kilowatts) of battery capacity per year." Watts are a unit of power. A more interesting stat would be the ENERGY capacity produced per year (i.e. joules).

RP, the data for range must be old. Used the calcualtor on the Tesla site and 205 mile range for least expensive Models S was at 65MPH, Zero degrees F, heater on. I would love to see more battery energy density improvements. Faster charging not as important for me. What are the most promising new battery technologies?

More close to the truth but mostly miss information. Based on old data and thinking in the past. Ice cars are on the way out because of the pollution and high cost of ownership. With an ev charging station in every home that the car spends each night. Even a lowly 110volt plug. With hundreds o thousands of charging stations all around the world. The number is growing daily. Ice manufacturers will tell you there are not. And complicate the process by having multiple standards of plug styles.

“Gasoline is… indifferent to climatic conditions. … Like a perfect servant, it’s (sic) personal characteristics and quirks rarely, if ever, get in the way of doing its job.” Who wrote that for you, an oil company lobbyist? A burnable gasoline / air mixture for an engine – especially one that is attempting to operate efficiently – is very affected by temperature and humidity. Why do you think that engine fuel delivery has evolved into the computer-controlled systems we have today?

Have you never tried to start a simple snow blower engine on a cold day when it has been sitting outside long enough to reach ambient temperature? Yes I fully admit that today’s battery technologies lose capacity at low temperatures. But that’s no excuse for exaggerating the virtues of its competitors. Possibly batteries would be better too if they had enjoyed a hundred years of continual engineering development like ICE has.

We developed our infrastructure based on the availability of a high-energy-density fuel with unlimited range. Had we known that ICEs would become immoral, nearly illegal, "buggy-whip" antiquated, perhaps we'd have done it differently. I applaud Tesla in their apparent ability to create a market, create a need, and then build a giga-factory to fulfill that need. Seems a lot of expense for what might be a short-term solution though.

The solution, here, is the diesel-electric system, which is one in which the diesel motor is used solely to operate a dynamo (alternator), which supplies electric energy, and the electrochemical battery is used for taking energy during dynamic braking and delivering it during acceleration. This provides efficiency, range, and independence from a costly special infrastructure. Diesel motors can be extremely clean when operated at optimum conditions, as would be the case, here.

Well okay - diesel electric is a full hybrid system and we know that hybrid vehicles have better fuel economy though still not as good as the MPGe of electrics. Oddly, you and the original author neglected to point out that diesel fuel has higher energy density than gasoline. However, the raw energy density analysis doesn't take into account conversion efficiency; the author chooses to present the low efficiency as a virtue: all that wasted energy be used to heat the interior.

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