Dynamic response and long-term stability of a small direct methanol fuel cell stack

This study examines the operating characteristics and durability of a small direct methanol fuel cell (DMFC) stack (volume: 39.6 cm(3)). To investigate the operating characteristics in a real multi-user operating mode, various load cycles (such as gradual acceleration and deceleration), two operating modes (current mode or voltage mode) and four interrupted operating methods (load on-off, load-methanol on-off, load-air on-off, and load-methanol-air on-off) are used. The durability of the DMFC stack is examined at a constant voltage of 2.4V (0.4V per cell) by using the load-methanol-air on-off mode for more than 2000 h. In these tests, the DMFC stack exhibits a rapid, stable and dynamic response regardless of the load cycle and operating mode, though the stack performance and response behaviour vary with the interrupted operating modes. Among the operating modes, the air-interruption modes exhibit better stability and higher performance. Moreover, the load-methanol-air on-off mode provides the stack with good durability and a high performance in a long-term test of 2045 h. (C) 2010 Elsevier B.V. All rights reserved.