A model based investigation of evaporative cooling for polymer electrolyte fuel cells – Stack level analysis

Abstract

Potentials and limits of evaporative cooling for PEFC are analyzed.• A zero-dimensional fuel cell stack model is developed.• Optimal operating conditions for evaporative cooling are quantified.• An operating window for evaporative cooling is proposed.• The high mass, volume and cost saving potential of evaporative cooling is proven.

Evaporative cooling for polymer electrolyte fuel cells - An operando analysis at technical single cell level

“…At lower gas speed the evaporation rate is limited by the saturation of the gas stream, whereas it is limited by the diffusive transport of water vapor at higher velocities. This fact is relevant for future modelling work, since previous studies [13,36] assumed a linear correlation of evaporation rate and gas speed. The operating window for evaporative cooling that we proposed in our previous work, however, is not affected by this fact, since an operation at low pressure, high temperature and low to medium stoichiometry has been proposed [13,39].…”

“…These include but are not limited to: operational stability, inhomogeneous temperature and humidity distribution, freeze start capability, amount and quality of recovered water from the exhaust gas as well as the potential risk of enhanced cell degradation due to the increased relative humidity and temperature. Observed limitations of the evaporative cooling approach are discussed in detail in section 3.4 as well as in our previous work [13].…”

“…Evaporative cooling is a promising cooling and humidification concept for PEFCs. It shows the theoretical potential to reduce system mass and volume by up to 30% by eliminating the complex, multi-layered structure of bipolar plates as well as the need for external humidification [13,14]. This, in turn, contributes to significant volume savings and cost reductions.…”

“…Several numerical studies [13,[34][35][36][37][38][39] presented in literature have analyzed evaporative cooling on material, cell, stack and system level. These studies coherently highlight the advantages and the high theoretical potentials of evaporative cooling for polymer electrolyte fuel cells.…”

“…These include an improved humidification of the membrane, eliminating the need for an external humidifier, simplifying the structure of the bipolar plates and thus significant mass, volume, and cost saving potentials, respectively. A detailed literature study on numerical investigations of evaporative cooling can be found in our previous work [13,39].…”