Fuel Cell Based Air Conditioning for Passenger Transport Systems

Abstract

A hydrogen based energy supply with fuel cells gains importance as today fuel cell vehicles and fuel cell trains are commercial products. Having stored hydrogen available in such an application of an air conditioning system based on a low temperature PEM fuel cell appears promising, as a fuel cell provides all necessary products. Those are heat, humidity and electric power. The calculations show which heating and cooling loads occur in an aircraft cabin at varying ambient temperatures. The determined thermal loads are provided by a fuel cell system, whereby cooling loads are applied by an electrically driven heat pump in a chiller unit. For an 18-person aircraft cabin, it shows that heat of 1.3 kW must be supplied at -40 °C and that heat of 2.4 kW must be removed at +40 °C in order to achieve a constant cabin temperature of 21 °C. The air volume flow into the cabin is determined by the Pettenkofer scale so that the CO2 concentration caused by the passengers does not exceed the limit value of 1500 ppm. In the case of heating (-40 °C ambient temperature), 9.6 kW of the fuel cell waste heat must be transferred to the supply air in order to maintain the cabin temperature at 21 °C. The supply air must be humidified with 2.8 kg/h of water in order to achieve a cabin humidity of 48 %. In cooling mode (+40 °C ambient temperature), the electrical power of the fuel cell system is used to drive the electric motor of a heat pump in order to dehumidify and cool the supply air. For this purpose, 8.3 kW of thermal power must be provided at the air cooler. With a coefficient of power equals 3 and an electrical efficiency of 0.7, 5.1 kW of electrical power is required from the fuel cell. A fuel cell system designed for this scenario requires 600 g hydrogen per hour for the heating and 240 g hydrogen per hour for cooling.