The change has been so gradual you'd hardly notice. Rather than huge multi-cylinder or turbocharged engines, the average wild concept car shown at the Geneva Motor Show is typically powered by fuel cells or batteries, these days.

Making its debut at the show this year is La Vecchia's Quant e-Sportlimousine, whose power system is somewhere in between the two--using a technology known as flow cells.

It features a powertrain developed by nanoFLOWCELL, a German company with technical ties to Bosch.

Breaking it down to simple characteristics, flow cells are like batteries, but share aspects of electrochemical accumulator cells with those of fuel cells.

Liquid electrolytes are stored in two tanks, and circulated through the cells. A membrane separates the two electrolytic solutions, as it does in a fuel cell, and as electrical charge passes from one cell to the other, it produces power for the drivetrain.

All the usual benefits are described here: High charge density, high performance density, light weight. It's also said to contain no harmful substances--ticking a rather important and hotly-debated box--has no moving parts, and is energy-efficient.

MORE: 'Flow Cells' May Let Electric Cars Recharge With Liquid Refills

The upshot is five times greater performance-by-weight than current lithium-ion cells, which in turn means five times greater range than a regular battery of the same weight.

Storage capacity is said to be around 120 kWh, which is a significant chunk more than the 85 kWh Tesla Model S. A claimed 372-mile driving range is the result, and while not explicitly stated the flow cell is sure to be lighter than the Model S battery, which weighs several hundred pounds.

The great unknown is how people may charge the e-Sportlimousine. When we've looked at flow cells previously, their great attraction has been battery-like characteristics with fuel-like filling capabilities. Unfortunately, La Vecchia provides no details here.

The company calls the e-Sportlimousine "neither a show car, nor a concept car". It's clearly both, but to its credit La Vecchia says it intends to build four prototypes for real-world testing.

They're unlikely to feature the e-Sportlimousine's stunning show-car styling with its gull-wing doors, but this is one auto show concept where the technology under the skin is far more interesting than the body clothing it.

For more Geneva news and images, head over to our dedicated Geneva Motor Show page.