Harsh winter weather can diminish the range of battery-powered vehicles. Likewise, the performance of a plug-in hybrid like the Chevrolet Volt can suffer as the mercury dips. However, when General Motors' designed the Volt, the automaker wanted to develop a plug-in that could effectively tackle grueling winter weather without a noticeable degradation in performance. Volvo dealt with this issue by adding a small ethanol heater.
Though In the winter, the Volt's battery pack is often tasked with powering a resistive heater to warm the vehicle's cabin and, as Susan Stevenson, GM's benchmarking engineer for heating, ventilation and air conditioning systems explains, "It requires as much energy to heat the interior of a car on a cold day as it does to drive at a constant speed."
Therefore, GM designed the Volt's HVAC system to minimize battery drain while still allowing it to pump out ample heat to keep occupants comfortable. In sub-freezing temps, the Volt's engine kicks in periodically to heat the coolant, creating thermal energy to warm the cabin. Andrew Farah, vehicle chief engineer for the Volt, explains the functionality of the Volt's unique HVAC system like this:
However, even with its energy-optimizing HVAC system in place, the Volt, like all other automobiles, is affected by the mechanical factors (i.e. increased rolling resistance of snow-covered roads and higher viscosity fluids) that are often associated with driving in cold climates and will likely suffer some degradation in fuel economy and electric-only range as temperatures drop.Volt drivers in Southern California will likely never experience this in their day-to-day commute, but if they pack up their gear and head into the mountains for some skiing, they will appreciate the enhanced cabin comfort made possible by this unique powertrain.
[Source: General Motors]
Chevy Volt Electrically Equipped for Winter Driving
Detroit - When the first Chevrolet Volts purchased by retail customers rolled off the delivery trucks in New Jersey recently, they were met with the season's first major blast of winter weather. The new owners quickly found out the world's first extended-range electric vehicle came fully winterized.
One of the goals in developing the Volt was to create a plug-in electric vehicle suitable for everyday use regardless of weather. Typical northern winters take an even bigger toll on battery-powered vehicles than on traditional internal combustion-powered cars and trucks.
Engines produce plenty of waste heat that can be used to warm the air in the cabin and keep things comfortable. The inherently greater efficiency of an electric powertrain means less wasted energy, but it also means that the battery has to be used to power a resistive heater to produce that warm air - electrical energy could otherwise be used to propel the vehicle, which is one of the reasons why electric vehicles have a significantly shorter driving range in cold weather.
"It requires as much energy to heat the interior of a car on a cold day as it does to drive at a constant speed," said Susan Stevenson, General Motors benchmarking engineer for heating, ventilation and air conditioning systems.
The Volt has several features designed to minimize the drain on the lithium ion battery while still affording occupant comfort. The exclusive OnStar MyLink smartphone app or the MyVolt.com website can remotely start the Volt and warm the cabin while it is still plugged in and drawing power from the grid, leaving the battery with a full charge to maximize the electric driving range.
"The coldest weather I've experienced so far with my Volt was 18 degrees during a drive to the Poconos and I've had no complaints," said Jeffrey Kaffee, the first retail customer to take delivery of a Volt in mid-December. "Most of the time I just use the Eco mode instead of the Comfort mode and it's been no trouble whatsoever."
Less energy is consumed maintaining the cabin temperature than heating it up, but even on the road the Volt has more to contribute. Heated seats available on the Volt require less energy to keep passengers warm and comfy than it does to heat the full volume of air in the car.
The Volt also can use the engine to generate some extra heat and electrical energy in sub-freezing temperatures. In sub-freezing temperatures, the engine will periodically cycle on and off, heating the coolant to create a reservoir of thermal energy that is then used to warm the cabin air.
Using engine heat this way enables faster window defrosting and rear seat heating than taking energy from the battery. Under light driving loads, the engine and generator also can put some electrical energy back into the battery during these heating cycles to extend the electric driving range.
"Volt drivers in Southern California will likely never experience this in their day-to-day commute, but if they pack up their gear and head into the mountains for some skiing, they will appreciate the enhanced cabin comfort made possible by this unique powertrain" said Andrew Farah, vehicle chief engineer for the Volt.
Even with all of the energy optimizations, the same mechanical factors that lower fuel mileage for traditional vehicles contribute to a shorter electric driving range in winter. Cold temperatures increase the viscosity and resistance of lubricants in transmissions and axles while roads covered in snow or slush increase rolling resistance causing the powertrain to work harder and drain the battery.
But the Volt's engine generator dramatically reduces the fear of being stranded. When the lithium ion battery is depleted, the industry-first extended range capability allows the car to continue on for up to 340 additional miles.
"Volt engineers spent many frigid weeks in places like Kapuskasing, Ontario and Fairbanks, Alaska testing and calibrating the climate control system to make sure that drivers and passengers remain comfortable while still enjoying plenty of gasoline-free electric driving even in the harshest winter weather" said Farah.
Founded in Detroit in 1911, Chevrolet celebrates its centennial in 2011 as a global automotive brand with annual sales of about 3.5 million vehicles in more than 130 countries. In the U.S., the Chevrolet portfolio includes: iconic performance cars, such as Corvette and Camaro; dependable, long lasting pickups and SUVs, such as Silverado and Suburban; and award-winning passenger cars and crossovers, such as Malibu, Equinox and Traverse. Chevrolet also offers "gas-friendly" solutions, such as Chevrolet Cruze Eco with an EPA-estimated 42 miles per gallon highway, and the Chevrolet Volt offering 35 miles of electric driving and an additional 344 miles of extended gasoline range, according to EPA estimates. Most new Chevrolet models offer OnStar safety, security, and convenience technologies including OnStar Hands-Free Calling, Automatic Crash Response, and Stolen Vehicle Slowdown. More information regarding Chevrolet models, fuel solutions, and OnStar availability can be found at www.chevrolet.com.