Water Recovery Schemes and Effects on the Water/Thermal Balances for a 100 kW PEMFC System

Proton exchange membrane fuel cell (PEMFC) systems have been investigated as alternative power sources for the stationary and automotive applications. However, they do not appear on the market yet. One of the main reasons is the difficulty of the water/thermal management in the system. Several water recovery schemes have been proposed to overcome this difficulty and to simplify the system configuration. In this paper, the influence of the water recovery schemes on the water/thermal balances in the PEMFC system is investigated. One is a scheme without water phase change at the condenser and the humidifier. The other is a scheme with water phase change. As a result, at low operating pressure, the scheme with water phase change has a large heat dissipation from the system. This is because large water recovery is required in the condenser. With increasing operating pressure, the influence of the difference in the water recovery scheme is diminished from the thermal balance point of view. This is because the requirement of the water recovery becomes small. In the favorable operating range for the stack, the water/thermal balances in the system with water phase change is quite difficult because the heat loads in the intercooler and condenser are very large. However, the water recovery scheme without phase change can solve this difficulty. This scheme makes the component design simpler in this operating range.