Nissan will begin in-vehicle testing of the new fuel cell stack to further improve its overall performance and reliability.

(1) Fuel cell stack

A fuel cell stack is the power unit of an FCV. Fuel cells generate electricity through a chemical reaction between hydrogen and oxygen. Because they only emit water as a by-product, FCVs are considered to be the most environmentally friendly vehicles.

Compact design with high power output
Nissan's fuel cell stack adopts a newly developed thin separator*1 that narrows the cell pitch*2 by 40% compared with Nissan’s previous stack which was provided by an outside supplier. At the same time, the plumbing components inside the stack case have been integrated, and the peripheral control devices have been built into the case to achieve a substantial reduction of size and improvement of performance. As a result, Nissan has succeeded in increasing power output while achieving a more compact design than the previous stack. Nissan's new stack can be reduced in volume to approximately 60% of the previous stack while providing the same level of power.

Long service life
Improvements made to the electrode materials more than double the service life of the new stack compared with Nissan's previous stack.

Expanded operating condition
The operating condition such as temperature range of the stack for producing electricity has been expanded by improving the electrolyte membrane*3 and other principal components, as well as by optimizing the flow of hydrogen and air that contains oxygen inside the stack, among other improvements.

*1This component separates the hydrogen and oxygen gases supplied to the individual cells and transfers the electricity produced to the next cell.
*2Pitch refers to the spacing between adjacent cells that are connected in series. A stack for vehicle application normally uses several hundred cells connected in series to obtain the necessary electrical voltage.
*3This ion-exchange membrane made of a polymer material allows hydrogen ions (protons) produced in the cells to pass through the membrane to the other side.

(2) 70 MPa high-pressure hydrogen storage system
This newly developed 70 MPa high-pressure hydrogen storage cylinder increases an FCV’s hydrogen storage capacity by approximately 30% compared with the previous 35 MPa high-pressure hydrogen storage cylinder without any change to the cylinder’s dimensions. This increased storage capacity can dramatically extend the driving range of FCVs.

The storage system has been certified by the High Pressure Gas Safety Institute of Japan (KHK) as a 70 MPa high-pressure hydrogen storage cylinder.

The new high-pressure hydrogen storage cylinder is made of an inner aluminum liner and an outer shell of several wound layers of a high-strength, high-elasticity carbon fiber. The winding pattern of the sting-like carbon fiber has been optimally designed to achieve high strength for withstanding 70 MPa of pressure.

Nissan is engaged in wide-ranging research and development activities aimed at popularizing the use of FCVs and has been conducting public-road driving tests in Japan since 2002 using prototype FCVs approved by the Minister of Land, Infrastructure and Transport. Nissan began leasing its X-TRAIL FCV to a limited number of customers, starting with oil refiner Cosmo Oil Co. in March 2004.