When the car IS the battery

VOLVO has replaced the metal trunk lid of this experimental S80 with a carbon fiber panel that doubles as a storage battery.

There’s no denying that electric cars represent the future of the automobile. Whether powered by hydrogen fuel cells or on-board chemical batteries, cars that are propelled by electric motors are more efficient and cleaner than their internal-combustion engine counterparts. One study reported that a switch to plug-in hybrids can cut greenhouse gas emissions by 27 percent and carbon monoxide emissions by 98 percent. Countries that get a high proportion of their electricity from renewable sources can benefit the most. The Philippines is certainly a candidate for electrification of road transport, with 29 percent of our energy coming from renewable sources.

Where electric cars are falling short right now is  in the energy-storage department. To achieve a range of about 400 kilometers, gasoline or diesel-powered cars carry about 50 kilogram of fuel. That translates to about 4 percent of the vehicle’s curb weight. The Tesla S, which uses one of the highest energy-dense types of battery, lithium ion, has a 85 kilowatt-hour battery pack that is estimated to weigh 550 kg. This is 26 percent of the car’s curb weight. A lot of the efficiency of the electric car is being negated by the weight of the batteries

SUPERCAPACITORS are embedded in molded carbon fiber body panels to enable them to store energy.

To make cars with heavy battery packs handle better, electric carmakers locate the packs closer to the vehicle’s floor. With a lower center of gravity, the cars handle better. This is not without its own set of risks, such as when a Tesla S sedan’s battery pack caught fire after a piece of metal road debris hit the car and punctured the battery. Combined with some analysts’ pronouncements, this led to a decline in the company’s stock to the tune of $600 million. (Much of this has been regained. Of course, conventional cars also carry around large quantities of highly flammable gasoline.)

Volvo Car Group may have one possible solution. The Swedish car company announced last week that it has developed a concept for using a car’s structural parts and body panels as the batteries. The process involves molding the part or body panel out of carbon fiber. A polymer resin, called a nano battery, and supercapacitors are sandwiched by the carbon fiber part. The carbon fiber laminate is layered and shaped, then cured in an oven—the usual way  carbon fiber car parts are fabricated. Supercapacitors are then integrated within this component skin.

The capacitors can be recharged by brake energy recapture or by plugging the system into the electrical grid. The body panels can discharge the energy as needed during driving. What is novel about the approach is that the carbon fiber nano battery can replace conventional body parts.

THE S80’S plenum is now a carbon fiber panel with integrated energy storage. It is rigid enough to act as the strut tower bar, while supplying energy for the start/stop and electrical systems.

In Volvo’s S80 experimental car, the trunk lid and engine plenum cover have been replaced with the nano batteries. The trunk lid is lighter than a standard metal lid, saving both volume and weight. Volvo says that the plenum cover also replaces the car’s strut bar and the start/stop battery. The strut bar is necessarily a very rigid structural piece that ties the car’s suspension towers and increases stability. The claimed weight savings is 50 percent, with the battery able to supply energy to the car’s 12-volt system.

The BMW i3 electric vehicle is molded from carbon fiber composites, as are hybrid supercars like the LaFerrari, McLaren P1 and Porsche 918. Potentially, these are the types of cars that can most easily integrate this new kind of battery into their body structures. The project that developed the new body-panel batteries was funded by the European Union, with Volvo Car Group as the only car manufacturer. Volvo sees the potential for increasing the energy storage capacity of electric and hybrid vehicles while also saving in weight and increasing efficiency. With its high appetite for risk and a competitive edge, Formula One is also a candidate for this type of technology. The day may come when the car itself—its chassis and body panels—is the battery.