Unlike its rivals Toyota and Honda, Japanese automaker Nissan has to date steered clear of hydrogen fuel cell technology. Citing concerns over economic viability, technical challenges such as power density and carbon-intensive way in which most commercial hydrogen is produced today, Nissan has instead focused on battery electric vehicles in the form of its Nissan LEAF electric hatchback and e-NV200 electric minivan.
To date, that policy has paid off: the Nissan LEAF is still the world’s best-selling electric car and Nissan, working alongside its alliance partner Renault have sold more than 200,000 electric vehicles around the world to date. Together, the two firms have also invested millions of dollars in public charging infrastructure worldwide, making it easier than ever before to make long-distance trips in any short-range but rapid charging-capable electric car.
Given its massive multi-billion dollar investment in electric vehicles and electric vehicle infrastructure, Nissan isn’t about to dump the electric car any time soon and has massive electric vehicle plans stretching more than a decade into the future which include both fully autonomous vehicle technologies and advanced, wirelessly-charging long-range electric cars.
But this morning it also announced a new research and development program in which it intends to commercialize a Solid Oxide Fuel Cell (SOFC) for use as an alternative power source for zero emission vehicles. Unlike hydrogen fuel cell vehicles which require compressed hydrogen to operate, Nissan’s new SOFC fuel cell can be powered by either natural gas or bioethanol. While the former is neither renewable nor carbon neutral, the latter can be produced in a carbon neutral way.
In a conventional hydrogen fuel cell vehicle stack, hydrogen is fed into the anode side of the fuel cell stack and passed over a platinum-rich proton-exchange membrane while at the same time, oxygen is fed into the other (cathode) side of the proton-exchange membrane. The platinum in the proton-exchange membrane acts as a catalyst, encouraging the positively charged hydrogen ions and negatively charged electrons in the hydrogen gas to separate. The electrons travel to the cathode, via whatever circuit you use (in fuel cell vehicles, via the motor). This, then, is the electrical current between the anode and cathode. The hydrogen protons themselves migrate through the exchange membrane and the electrolyte to combine with the oxygen and the returning electrons from the electrical circuit on the other side of the fuel cell, producing water (and heat) as the only byproduct of the process.
Inside Nissan’s SOFC, things are a little different. While hydrogen is still fed into the fuel cell on the anode side, it’s actually the oxygen entering into the fuel cell on the cathode side which passes through the fuel cell exchange membrane and through the electrolyte to the other side of the fuel cell. The oxygen combines with the hydrogen to produce water, electricity and heat.
Unlike proton exchange membrane (PEM) hydrogen fuel cells, which use high-cost platinum on both sides of the fuel cell, Nissan’s SOFC doesn’t require such expensive or rare materials to function, lowering build costs. And while Nissan hasn’t confirmed efficiency of its SOFC, SOFC technology is generally around ten to fifteen percent more efficient than a comparable PEM fuel cell.
Sadly there’s a setback: temperature. An SOFC operates at a far higher temperature (around 1,000 degrees Celsius) than a PEM fuel cell (80 degrees Celsius), meaning more heat is produced as a byproduct. But that, says Nissan, is one of the reasons it can use bioethanol as the fuel source.
With so much heat on tap, Nissan’s SOFC technology includes a steam reformer upstream of the fuel cell which combines the heat from the fuel cell exhaust with water to steam reform the bioethanol into carbon dioxide and hydrogen. The hydrogen is then used to directly power the fuel cell.
Nissan says the water needed to carry out steam reforming of the bioethanol (or natural gas) can either come from the fuel cell exhaust, combining inside the reformer with 100 percent bioethanol, or by using ethanol mixed with water as the fuel source.
Since Nissan’s SOFC technology doesn’t require hydrogen to be stored on the vehicle in either liquid or gaseous form, it has some major advantages over PEM fuel cell technology. For a start, bioethanol is far easier and safer to store, dispense, and use. Secondly, since SOFC systems are more efficient than PEM fuel cells, a car using an SOFC should demonstrate longer range than a PEM counterpart.
Finally, there’s the claim of better emissions. Unlike a hydrogen fuel cell car using compressed hydrogen, Nissan’s system does have tailpipe emissions in the form of carbon dioxide given off as part of the steam reforming process. However, since growing crops for biofuel captures carbon dioxide, Nissan claims these emissions are offset, making its technology carbon neutral.
Nissan says it plans to perfect its SOFC technology and bring it to market at some point in the future, but for now, the technology is still very much in a research and development phase.
Does this mean Nissan is switching its attention away from electric cars? No. For the foreseeable future, electricity appears to be Nissan’s number one future fuel source. But while electric cars can satisfy the needs of large swathes of the population, Nissan’s SOFC technology could find a home powering its larger commercial vehicles and full-size pickups. Like the Mercedes-Benz GLC F-Class plug-in hybrid fuel cell SUV we covered yesterday, Nissan’s SOFC technology could become a viable range-extending alternative to an internal combustion engine.
But there’s one fly in the ointment: biofuels. While biofuels have been touted for many years as a viable, lower-carbon alternative to fossil fuels, producing them requires a significant amount of land to be set aside, land which then cannot be used for food.
To date, the lure of biofuels has caused many hundreds of thousands of square miles of rainforests to be illegally felled, not only threatening the natural habitat of thousands of species of flora and fauna but also commandeering precious water supplies.
In a world where food and water supplies are becoming increasingly strained as the effects of climate change and population growth are felt, setting aside crops for biofuel rather than food is not sustainable. And while there are ways to produce bioethanol and biofuels from the byproducts of food production (the stuff you wouldn’t want to eat), or via developing algae based systems, we suspect it’s going to take some time before bioethanol fuel cells and bioethanol mass production reaches market readiness.
Do you think Nissan’s new investment in Solid Oxide Fuel Cells is a smart move? Or does it distract from Nissan’s already extensive work with electric cars?
Leave your thoughts in the Comments below.
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