Toshiba of Japan has been a leader in fuel cells and last October quietly put a methanol fuel cell on the market.   Japan is well known for introducing leading technologies into their home market, so this isn’t s shock.  But it certainly is a shot across the bow of every other fuel cell market ‘want to be.’

Toshiba Methanol Fuel Cell. Click image for more info.

At a price of about $320US the cell is still a cautious design.  And at that price its bait – Koji Kariatsumari and Hideyoshi Kume of Nikkei Electronics Asia with some consultants and help from Toshiba tore one down for their article.  Keep in mind that mass production, should it follow the latest trend seen in Blu-Ray DVD players, would take the price to under $50US.

The design seems extra safe.  There is extensive use of metal parts such as stainless steel and aluminum alloy.   Called the “Dynario” Toshiba let loose only 3000 units, in the midst of a recession, much to the surprise of engineers worldwide that are working in the field.
The Dynario seems quite mature in that comments center about the design, which stabilizes the incoming air humidity, there is no methanol smell, and it warms when running only to about the temperature of hot bath water.

The Dynario is a direct methanol fuel cell (DMFC) with a USB connector that allows it to charge mobile equipment such as cell phones and mpg players. The maximum output, together with the internal Li-ion rechargeable battery, is 2 W (5 V, 400 mA). The fuel cell is fueled with 14 mL of methanol, which, according to Toshiba, “is enough to charge a piece of mobile equipment about two times.” Kariatsumari and Kume used an LED lamp with a power consumption of 1 W to verify that it generated enough output for about 11 Wh.

Toshiba Methanol Fuel Cell Parts View. Click image for more info.

Kariatsumari and Kume say they were surprised at how many parts were inside.  The Toshiba people explain, “There are a number of custom components that just pushed the price up.”  In addition to the actual fuel cell, there was an ultra-miniature pump and valve, as well as micro-controllers, control ICs, control boards, and other circuit components. The case was so sturdy it almost seemed like overkill.  It’s built with a metal exterior including reinforcing members. Most of the people who looked inside, including mobile equipment and fuel cell engineers, agreed that it was almost certainly impossible to sell it for only 30,000 yen, considering components, manufacturing and other costs.

The Dynario has two key generating units mounted in the center of the case, one in front and another in back. The center of the case also holds a cylindrical Li-ion rechargeable battery manufactured by Sanyo Electric Co., Ltd., and two control boards mounting the power switch and input/output (I/O) pins, with the rest of the parts attached to the center case frame.

The fuel tank is located on the end of the center case frame. The case itself has aluminum alloy front and back, with plastic on top and bottom. An engineer in the fuel cell industry commented Toshiba seems to have used a lot of metal parts to maximize durability, strength and other characteristics, given that this is the first volume production model.

The generating unit positions the power cells between a stainless steel lattice and a plastic holder that acts as the fuel supply plate. The stainless lattice and plastic holder are riveted together, making it impossible to remove the generating cell without destroying the power cells. The stainless steel lattice also acts as the air inlet for the power cells, while the generating unit control board, fuel pump, fuel valve, and other components are mounted on the fuel supply plate side. The control board holds the ICs controlling the fuel pump, fuel valve, an 8-bit micro-controller, and more.

Toshiba Methanol Fuel Cell Control Board. Click image for more info.

Toshiba Methanol Fuel Cell Fuel System. Click image for more info.

The fuel valve and fuel pump can be seen mounted on the generating unit. Both components are electro mechanically driven, so key design goals must have been minimizing power consumption and ensuring durability. Additionally, use for mobile equipment imposes strong demands for small size, thinness, etc, leading one fuel cell engineer to suggest this is where manufacturers have the toughest problems.

Kariatsumari and Kume think Toshiba had a tough time designing the fuel valve, as it protrudes 6 mm beyond the other components. The fuel pump and control board have all been thinned down, but the fuel pump seems to have had insufficient development time. Thus, it has been positioned off-center and the two power cells positioned to make room for it, keeping case thickness to a minimum.

Murata Manufacturing Co., Ltd manufactured the fuel pump in the unit Kariatsumari and Kume disassembled.  It uses a piezoelectric device, and is quite thin measuring 24 mm × 33 mm × 1.325 mm. The pump discharge rate is thought to be 0.001 mL/s, with a pressure of 35 kPa.
The fuel path is from the tank to the fuel valve and into the plastic fuel supply plate.  The fuel pump then pressurizes the fuel into the fuel supply plate.

Toshiba Methanol Fuel Cell Membrane Electrode Assembly. Click image for more info.

The power cells are membrane electrode assemblies (MEA) measuring 81 mm × 52 mm, and a collector. Each MEA uses four single cells, each measuring 81 mm × 9 mm. As each cell probably has an electromotive force of about 0.3 V that means the generating unit would generate over 1 V. The step-up circuit on the generating unit control board then boosts output to about 5 V.

Kariatsumari and Kume are calculating cell output density to about 25 mW/cm2, leading a consulting fuel cell engineer to theorize it was deliberately kept low to control heating issues. Toshiba has said that it developed fluorine- and hydrocarbon-based solid polymer films, but it is unclear which was used in this product. Several of the consulting fuel cell experts commented that the Dynario is most likely the fluorine-based design.

The Dynario’s Li-ion rechargeable battery supplies electricity for the operating load until output from the generating unit stabilizes at start-up, as well as pass through powering the generating unit control circuit and other components.  The Li-ion rechargeable battery and generating unit are controlled by the 8-bit micro-controller with 2 Mbits of internal flash memory on the control board that also holds the power switch and some I/O pins.

Toshiba gave top priority to assuring safety. On the list is an auto-stop when the unit gets too hot.  Kariatsumari and Kume’s tests showed that the auto-stop function triggers when the surface temperature reaches about 45°C.  A temperature sensor at the generating unit air inlet ensures that surface temperature does not exceed a preset maximum The fuel cell is said to incorporate other functions as well, such as disabling operation at temperatures of 100°C or higher, and breaking high input currents through the I/O pins.  All in all, it’s a commercially viable design.

The obvious questions are about scaling up the output.  What we can interpret from the Kariatsumari and Kume tear down is that ‘cool’ running methanol fueled fuel cells are practical even in a seemingly high cost design.  Production in volume can greatly reduce the costs, and at over a volt per membrane electrode assembly the power output can add up with the attendant gear only needed once per unit.  Costs could plummet if sales volume grows.

Other questions are in the design that Kariatsumari and Kume didn’t report.  Just how is Toshiba keeping the humidity out?  There is something very clever in the design not discussed.  Nor did they cover the fueling process itself; is there a design to handle the methanol handily and safely by the masses? And just how efficient is it?

Even with the omissions aside, Toshiba has a breakthrough sales claim.  Fuel cells using renewable fuels such as methanol and ethanol should have a great future.  A hybrid automobile with an ethanol fuel cell would be vastly more efficient than an internal combustion engine and could offer chassis sizes and performance that American’s crave.  If you don’t like the idea of a mini sized car, fuel cell power is certainly going to be one route to salvation.


2 Comments so far

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