Plug-in electric vehicles. Hydrogen fuel cell cars. Hybrids. Plug-in hybrids. All have come to the fore over the years, and we’ve noted their unique impact on the automotive landscape. While these technologies share similarities in that they all employ different ways of managing electricity to power electric motors, it’s been pretty easy to draw lines between them. But what if those lines were blurred in the interest of creating a new and possibly better answer, like maybe…a plug-in hydrogen hybrid?
Actually, that question was on the minds of creative souls at Ford some 15 years ago. Back then, the automaker explored new paths with its Ford Edge HySeries, a drivable demonstration vehicle unveiled at the Washington, D.C. Auto Show.
This Hydrogen SUV Plugs In
The HySeries combined power from the grid by plugging into an electrical outlet, just like an electric car or plug-in hybrid. It used a hydrogen-powered fuel cell to provide electricity, just like other fuel cell vehicles. And it managed its two power supplies via on-board battery storage, just like hybrid and plug-in hybrid cars do today.
Central to the HySeries Drive, both figuratively and physically, was a 336-volt lithium-ion battery pack that powered the electric motors at all times. Electricity from the grid and the fuel cell didn’t get to the wheels without first going through this battery pack. In this single-path flow of power, the power unit – the fuel cell – and the batteries were designed to act in series.
Series Versus Parallel Hybrid
With the notable exception of a few models like the Chevrolet Volt, in most hybrids the batteries and engine operate in parallel. That is, the engine can still directly send power to the wheels with the battery stepping in to provide boost or take over as necessary. These hybrids do periodically act like a series configuration by using the engine to charge the batteries back up, for instance. The difference is that the HySeries Drive runs exclusively in series mode…thus, the name.
What’s the advantage? In a word, simplicity, according to Ford at the HySeries’ auto show debut. Operating in series streamlined the process by eliminating the extra hardware – and complex management software – of two propulsion systems in favor of a single power flow. By the same token, this made the HySeries Drive remarkably versatile.
In the Ford Edge prototype presented here, the fuel cell acted as a range extender, providing electrical power when the batteries ran low on their grid-sourced charge. But that range extender could just as well have been an engine powered by gasoline or some other alternative fuel. The thinking was that any new fuel or propulsion technology could be swapped in as it became available, with the underlying architecture of the HySeries Drive the same in any case.
The Ford Edge with HySeries Drive was designed to demonstrate the logic of this approach. According to Ford, the size, weight, cost, and complexity of this particular drivetrain was reduced by more than 50 percent compared to conventional fuel cell systems at the time. By relying more on the battery pack and the grid-sourced electricity, the demands on the fuel cell system were reduced as well. This meant the Ballard-supplied fuel cell would last longer and less hydrogen would need to be stored on-board.
Hydrogen Hybrid Operation
Out on the road, the Edge was designed to drive 25 miles on battery power alone. When the battery pack was depleted to 40 percent charge, the fuel cell turned on and began generating electricity to replenish the batteries. The 4.5 kg of hydrogen stored in a 5,000 psi tank was enough to extend the range another 200 miles, for a total of 225 miles. Ford pointed out that range was highly dependent on driving conditions. In fact, it was also said that careful driving could potentially squeeze more than 400 miles from the fuel supply. Given that on-board hydrogen is now typically stored in 10,000 psi cylinders rather than the earlier 5,000 psi variants of the HySeries’ time, that driving range had the potential to be significantly greater.
Actual fuel economy would depend on the length of a trip. For those driving less than 50 miles a day, the Edge with HySeries Drive would be expected to return a miles-per-gallon equivalent of 80 mpg. Longer drives tapping further into the hydrogen supply would bring combined city/highway equivalent fuel economy down to 41 mpg, still respectable for a crossover SUV. Of course, while the fuel economy rating may have had a gasoline equivalent, the emissions did not. That is, there weren’t any emissions at all…at least not from the vehicle itself.
As innovative as Ford’s HySeries Drive was, it was not totally unique. Also in 2007, Chevrolet showcased its Volta concept using GM’s E-Flex System, which later evolved into the Chevrolet Volt powertrain. Both Ford and GM approaches relied on a large lithium-ion battery pack operating in series with a separate power source that charged batteries when they ran low. Notably, both systems offered plug-in capability. While the HySeries incorporated advanced hydrogen fuel cell power, the Chevy Volta did not, though GM did share this was a future possibility. Rather, the Volta, like the production Chevrolet Volt to come, used a 1.0-liter gasoline engine as its range-extender,
Birth of the Plug-In Hybrid
What we saw in the Ford Edge with HySeries, the Chevrolet Volta, and other concepts to follow was the underlying development of a drivetrain showcasing a new propulsion category carving its place into the mainstream – the plug-in hybrid vehicle. At the same time, both GM and Ford seemed eager to link their conception of the plug-in hybrid to the trek toward hydrogen-based transportation, which at the time was the official long-term goal of these two major automakers and others. In this sense, the plug-in hybrid would conceptually follow the conventional hybrid as another intermediary step on the path to hydrogen power.
Of course, to expect such a simple, linear progression – gasoline, hybrid, plug-in hybrid, hydrogen – is, and was, naïve. But that’s the core challenge with predicting the future of any industry, or of life in general, for that matter. Emergent and divergent technologies, parallel paths, and new alternatives are guaranteed along the automobile’s evolutionary path. In particular, we have seen that in recent years with the breakout of all-electric vehicles into the automotive mainstream, in numbers that were not envisioned by most at the time the HySeries was revealed.
With the HySeries-equipped Edge, Ford presented a surprisingly realistic look at how HySeries Drive – or something like it – could one day take to the road. It sat on the cutting edge of a broad trend away from petroleum-burning internal combustion and toward electrically-powered transportation, a trend that is accelerating today.