Recycling fuel cell waste heat to the thermoelectric cooler for enhanced combined heat, power and water production

Abstract

The energy efficiency of fuel cell-based cogeneration systems is limited by the stack’s natural characteristics, and fuel cell water recovery is an energy-consuming process. Here, an alternative system concept is proposed, which recycles the fuel cell’s waste heat to the thermoelectric heater’s cold side to increase its temperature. Hence, the temperature difference across the thermoelectric cooler drops to increases the coefficient of performance for water heating. Furthermore, by cooling the fuel cell’s flue gas, by-product liquid water recovery is achieved. A system-level mathematical model is developed to combine the 1 kW fuel cell stack and thermoelectric cooler/heater model, which analyzes the hybrid system’s performance for efficiently generating power, heat, and drinking water. During the analysis, the hot side temperature, thermoelectric cooler size, and humification rate have been parametrically swept. Results show that adopting thermoelectric modules of 12 or more and lowering the airflow rate to 0.02 kg/s enabled energy efficiencies of up to 1.1 under an ambient 283.15 K and reference 323.15 K temperature heat transfer conditions. Also, up to 1.5 kg/h of liquid water could be recovered if the water-heating temperature is changed to 308.15 K.