Fuel Cell Thermal Management with MicroCoolers 2002-01-1913
Thermoelectric generators (TEGs) are unique solid-state components that can be used as a cooling device when supplied with electric power. These microgenerator coolers (MICs) can be built in many configurations for unusual applications where parasitic thermal energy must be managed. Such an application is in Proton Exchange Membrane (PEM) fuel cells where waste heat is generated during electrical energy production. This heat generation reduces fuel cell performance, can damage cell components and increases system operating costs.
A thermal model is developed to utilize the bipolar plate in a PEM fuel cell to double as the cold junction plate of a MIC. The bipolar plate is in full electrical (thus thermal) contact with the Membrane Exchange Assembly (MEA), where the majority of heat is generated.
The waste heat in the cell membrane is modelled as a uniform flux on the bipolar plate's surface. This flux is manifested as a generation term to develop a two-dimensional, steady-state heat conduction model in the bipolar (cold junction) plate, thus predicting the MIC's cooling effect on the bipolar plate, and in adjacent MEAs.
This model provides the temperature distribution in the selected design of the cold junction plate, hence throughout the bipolar plate, and can be used to predict the temperature field in the MEA region, as well as the temperature gradient in the fuel cell.
The preliminary, one-dimensional study presented here utilizes this thermal management scheme inside the fuel cell to show that the interior centerline temperature of the b10c0ar plate can be maintained at 60C or less throughout the full power range of the cell, eliminating the need for external humidification. And at maximum fuel cell power output (440mW/cm2), the MIC required approximately 12% of the cell output to maintain this bipolar plate centerline temperature.
Thus the model shows that the improved heat management capability inside the fuel cell with MICs will provide a better performing cell that can meet the severe operating conditions required for the automotive industry.