Daihatsu Kei concepts bet on hydrazine as future fuel
By Vincent Rice
April 1, 2012
It has been a tough couple of years for the Japanese motor car industry, not least for Daihatsu. On top of natural and man-made disasters, Japan’s oldest car manufacturer, now part-owned by Toyota, has struggled to sell its super-compact “Kei” class vehicles outside of the home market. The company clearly feels however that the future will come to it, predicting demand for compact, zero-emission, hybrid powered vehicles, and has been developing a unique fuel-cell power source for just such a future since 2007. Leading the company's typically cute concept car range is the FC ShoCase - a vehicle suitable for the new fuel-cell.
Here's a brief re-cap of the Daihatsu concept vehicles shown late last year in Tokyo. The D-X (“d-cross”) is a sporty two-seater, the appearance of which can be changed by swapping out the resin body-panels. Power comes from an extremely efficient but conventional two-cylinder turbo. The PICO is a tandem two-seater car/bike crossover designed for the local delivery function so prevalent in Japan and indeed the whole of Asia. Motivation is provided by a plug-in electric battery/motor combination.
The most interesting vehicle on show was the FC ShoCase, designed specifically to show-off the possibilities of the fuel-cell power plant. With the cell and motor under the flat floor, clever stowage of the seats allows for an extremely versatile interior; including, one suspects, use as a mobile “love hotel” by young privacy-starved Japanese couples! This is a great looking concept. Please build this Daihatsu.
Of course, fuel cells have been touted as a potential power source for charging batteries and/or driving electric motors for many years. There are serious problems however - the fuel can be dangerous, a large amount of platinum catalyst is required, and power output density (the amount of power produced for a given size of cell) is limited. The Daihatsu cell addresses these concerns in an innovative manner.
Since conventional fuel cells (proton-exchange type) use strongly acidic electrolyte membranes, platinum, which possesses excellent corrosion resistance, is the only material that can be used as the electrode catalyst. By reversing this conventional model and utilizing an alkaline anion exchange fuel cell Daihatsu succeeded in eliminating platinum from the electrode catalyst, replacing it with an inexpensive metal (cobalt, nickel, etc.), which could not be used before due to low corrosion resistance.
By using hydrazine hydrate, which consists of only hydrogen and nitrogen, as the fuel, and developing new materials for the electrode catalyst, Daihatsu achieved both an output density of 0.50 W/cm2, which is comparable to the output of a hydrogen fuel cell, and zero emissions, with water and nitrogen being the only substances emitted.
Hydrazine hydrate is a liquid fuel, easy to handle during filling and its energy density is high. Furthermore, as an environmentally friendly synthetic fuel, hydrazine hydrate results in no CO2 emissions at all. At the same time, high-concentration hydrazine hydrate is designated as a poisonous substance (over 30% concentration) and it must be handled under the same safety standards applicable to gasoline and most industrial chemicals.
With the objective of ensuring safe use, Daihatsu developed a technology that fixes the hydrazine hydrate inside the fuel tank through the use of a polymer, minimizing the adverse effects that any dispersed fuel could have on humans or the environment should the fuel tank be damaged during a collision, for example, but that makes the required amount of liquid hydrazine hydrate available in a timely manner for electricity generation in the fuel cell.
Concept cars don’t often translate into real-world production and that’s likely the case here. The Daihatsu fuel cell development however is very real. Clearly the company is showcasing the technology in a bid to attract further R&D; partnerships and get a unit into volume production. Let’s hope it succeeds.