Hydrogen fuel cells
There is something of an ongoing debate in the world of e-mobility as to hydrogen’s place in the energy ecosystem (writes Lawrence Butcher).
While manufacturers such as Toyota are throwing their weight behind the fuel, and actively marketing fuel cell electric vehicles (FCEVs), others such as Mercedes-Benz are hedging their bets by investing in battery EVs and developing FCEVs (with a focus on the commercial sector).
There are plenty of arguments for and against hydrogen, not least those surrounding the establishment of a hydrogen supply infrastructure, and the efficiency of using electricity to convert water to hydrogen, then using the hydrogen to generate electricity.
The technology to create fuel cells that can provide a truly practical solution for roadcar use is still developing. However, the efforts of Swiss company Green GT for example are yielding some impressive results.
Jean-Francois Weber, managing director and head of r&d at the company, explained at the end of 2018 that the powertrain of its latest concept (developed in conjunction with Pininfarina), the H2 Speed, was almost entirely new compared to that in its previous car, the Green GT H2.
“The fuel cell we used in the first car had 18 stacks, and was based on roadcar technology,” he said. “Working with our suppliers, we now have a system with a more active surface chemistry on the fuel cell membrane, and our new fuel cell only has four stacks. But those four stacks can develop 250 kW net.”
The previous cell Green GT used was more powerful, developing 320 kW, but significantly its weight was 400 kg. The new cell is just 133 kg, with the design delivering a huge increase in power density.
Despite development being ongoing for the automotive market, it should be remembered that FCEVs are not a new idea. GM was one of the first on the scene back in the 1960s (although Allis-Chalmers did develop a fuel cell tractor at the end of the ’50s).
GM’s effort was the Electrovan, which was truly cutting-edge by the standards of the time. Drawing on expertise garnered from NASA’s Gemini space programme, the Electrovan was fitted with a fuel cell from Union Carbide, which used a combination of liquid hydrogen and liquid oxygen.
The 5 kW cell was developed by a team led by engineers Karl Kodesch and Carl Grulke, who envisioned that the cells would be used for vehicle applications. The cell was what is known as an Alkaline Fuel Cell (AFC), also known as a Bacon fuel cell after its inventor, Francis Thomas Bacon.
This type of cell is still in use in some applications; it uses positive and negative electrodes separated by a porous matrix and an aqueous alkaline solution. The cells have to operate on pure oxygen, rather than air, as introducing CO2 into the mix leads to the creation of potassium carbonate.
AFCs have a higher efficiency than other types of cell, such as proton exchange membrane units, the downside being a need for a liquid oxygen supply.
The Electrovan’s performance was quite impressive. It could run at 63-70 mph and had a maximum range of around 120 miles. However, it was a temperamental beast and the fuel cell filled most of the interior space.
GM shelved the project as there was little call for electric vehicles of any sort in the US in the mid-60s, but it marked the start of an enduring interest in automotive fuel cell technology.
Fast forward to the present day, and GM is one of the manufacturers looking to take a stake in any future FCEV market, specifically for military applications.
In 2017, it unveiled its SURUS autonomous support vehicle, then in 2018 a fuel cell truck equipped with a 25 kW cell. It also invested in a company called Quantum, which produces high-pressure (about 10,000 psi) tanks for storing hydrogen.
Fuel cells are clearly an intriguing alternative to battery EVs, but whether they are just a stopgap until battery energy density improves or a longterm solution, only time will tell.