Examining Flow Cell Cars


By Bill Tressler

Photo courtesy of Wikimedia Commons.

In recent years, the world has become increasingly focused on alternative energies. Solar cells, ethanol, hydrogen, biodiesel: All of these fuel sources have proven to be drastically better for the environment, yet none have become the industry standard that some may have hoped.

One of the latest alternative fuel concepts to shake up the auto industry is the flow cell, introduced by the Liechtenstein-based company nanoFlowcell AG. The company did not create the flow cell, but they are the first to integrate the flow cell into an automobile. Flow cells are an up-and-coming technology, but they’re already utilized by power companies within electrical grids.

At the 2014 Geneva Motor Show, the fledgling company unveiled their QUANT e-Sportlimousine, an ultra-sleek sports car that will supposedly possess 912 horsepower, a 300 mile range, a top speed of 236 mph, and the ability to go from 0-62 mph in just 2.8 seconds. For comparison, the Tesla Model S Performance, with its lauded lithium ion battery, achieves 416 hp, a range of 265 miles, a top speed of 130 mph, and is capable of going from 0-60 mph in 4.2 seconds.

It’s no wonder, then, that nanoFlowcell AG has shaken things up with their recent unveiling; their prototype is claiming numbers that put the Tesla Model S, the industry gold standard in electric cars, to shame. With their flow cell technology, the company claims to double the hp output of a Tesla, as well as increase the top speed by over 100 mph and cut its 0-60 mph time by over a second.

BTR reached out to Dr. Stephen Granade, the current Principal Research Analyst at Dynetics Inc. Dr. Granade is a physicist who received his PhD from Duke University and specializes in robotics and quantum optics. While hopeful that flow cells could become the eco-friendly standard in the auto industry, he remains skeptical of nanoFlowcell AG’s claims, and for good reason.

Flow cells utilize electrolytes to produce energy; the cell contains an aqueous solution (which isn’t water) that incorporates metal salts (which aren’t your typical table salts) stored in two tanks. These electrolytes flow through a membrane separating the tanks, producing energy. NanoFlowcell AG’s flow cell uses an as-yet-unspecified mixture, referred to only as “metallic salts in an aqueous solution.” In fact, much of how the technology works is unspecified. The company has released very little information on how the cell system works and they’ve yet to patent the technology, all under the guise of secrecy and protecting their methods.

Dr. Granade finds the benefits of a flow cell car promising. “The big benefit of flow batteries is that when you use up the charge in your electrolyte, you pump it out and put in [a] freshly-charged electrolyte,” he explains. “First, you put a nozzle into your battery’s two tanks and suck out the used up fluid. Then you pump new electrolytes into the battery. After that, you can drive away while the station recharges your used electrolyte for the next customer.”

Continuing, Dr. Granade compares the system to gas, except that the fuel is recyclable, which should keep the pricing relatively low. It’s likely due to these benefits that the flow cell concept has gotten auto enthusiasts and environmentalists alike chomping at the bit. The catch, however, is that the numbers simply don’t add up.

The problem with flow cells, as they currently stand, is that they aren’t capable of producing as much energy as other kinds of batteries, namely lithium ion cells. According to Dr. Granade, there’s 100 times less energy in a pound of rechargeable batteries then there is in a pound of gasoline, and flow cell’s contain even less energy density than that.

Due to their low energy density, in order to achieve the energy necessary to produce the numbers nanoFlowcell AG is claiming, you’d have to greatly increase the size of the battery in the car.

“The best flow batteries have energy densities that are one-fifth to one-tenth that of lithium ion batteries,” says Dr. Granade. So, in order to achieve the same energy output as a lithium ion battery, one would need flow cells that are five times heavier.

Dr. Grande illustrates this problem vividly, “The lithium ion batteries in a Tesla Model S weigh about 1,200 pounds. If you replaced those with flow batteries, they’d weigh more than 6,000 pounds! That’s as much as a Hummer H2!” That weight would, understandably, crush any hope of a 300 mile range or hitting 62 mph in 2.8 seconds.

It seems that flow cell technology, in its current state, is simply not advanced enough to provide the range, top speed, and horsepower that nanoFlowcell AG claims the QUANT E can achieve, at least not at a manageable weight. The Tesla Model S weighs in at 4,950 pounds, with 1,200 pounds of that weight coming from the batteries. In order to obtain the dazzling numbers that they claimed in Geneva, nanoFlowcell AG’s QUANT E would require more than 6,000 pounds of battery, with the rest of the car weighing upwards of 3,000 pounds. The QUANT E would ostensibly have to weigh 9,000-10,000 pounds, while still achieving 0-62 mph in 2.8 seconds.

To top it off, some experts believe that the current models being shown around would cost as much as $1.7 million. Simply put, it seems that the QUANT series is just too good to be true. Compared to the Tesla models, which range from $70,000-$90,000, that’s about as unattainable as it gets.

According to Dr. Granade, lithium ion cells have been increasing in efficiency roughly 9 percent each year since the 1990s. Flow cells still have quite a bit of ground to make up and they don’t appear to be on the brink of overtaking lithium ion cells anytime soon.

While he believes that the world is a ways off from seeing flow cells become the standard in electric cars, Dr. Granade is still hopeful. He says, “Researchers are improving their energy densities and there’s a lot of benefit to being able to recharge your battery in five minutes by swapping out fluid instead of having to plug your car in for hours.”