Thermoelectric Heat Recovery From a Tankless Water Heating System

Thermoelectric cogeneration promises to recover waste heat energy from a variety of combustion systems. There is a need for computationally efficient simulations of practical systems that allow optimization and illustrate the impact of key material and system parameters. Previous research investigated thermoelectric material enhancement and thermoelectric system integration separately. This work connects material parameters and system integration. We develop a thermal simulation for a 15kW tankless, methane-fueled water heater with thermoelectric modules embedded within a cross-flow heat exchanger. The simulation employs a finite volume method for the two fluids. It links external convection with a surface efficiency of 85%, internal convection for laminar flow, and conduction through the system in order to determine power generation within the thermoelectric. For a single pipe in the water heater system, 126 W of electrical power can be generated, and a typical system could yield 370 W. Realization of effective cogeneration systems hinges on investigating the impact of thermoelectric material parameters coupled with system parameters, so the impact of varying flow rate, convection coefficient, TEM thermal conductivity, Seebeck coefficient, and thermal interface materials are investigated. While varying parameters can improve thermoelectric output by over 50%, thermal interface materials can severely limit cogeneration system power output.