Wan Ahmad Najmi Wan Mohamed

In the sustainable energy agenda, thermoelectric generators (TEG) can be a central technology for low-cost combined heat and power (CHP) systems. TEG module (TEM) is the combination of TEG cells, heat pipes, heat sinks and copper blocks that produce electrical power and thermal energy for low temperature heating simultaneously. Two TEG cells were used in each TEM for CHP in a bakery factory with a reference waste heat temperature of 250°C. Different designs of TEM affect the heat transfer mechanics through the components. However, actual testing of each design requires high cost and time consuming. Identifying the principal parameters affecting the desired output is indeed important before investing in actual design fabrication. One-dimensional model is developed in this manuscript to evaluate the fundamental interactions between each component. Parametric variation for nine main parameters characterized the steady-state response of each parameter under four novel heat sink configurations. The parameter sweeps approach benefits in designing a novel TEM for optimum system output. An improved TEM with 6 TEG cells was designed and it increased the heat recovery ratio from an initial 14% to 38%. The Reynolds number of streams are the major operating parameter as it influences the heat sink effectiveness. Large heat exchanger frontal area and copper block housing surface area are also significant parameters. Identification of these principle parameters would assist in effective designs of TEM systems for industrial CHP.

A thermoelectric generator (TEG) cell is a solid-state semi-conductor capable of converting thermal energy directly into electrical energy. Studies on specific designs for TEG modules are needed for an effective industrial waste heat recovery. Typical TEG systems apply direct heating or cooling without being assisted by heat transfer devices which makes it difficult to maintain high temperature difference between TEG cells surfaces for higher electrical power generation. To suit the TEG system with the industrial condition, a waste heat recovery (WHR) module was developed consisting of a Bismuth Telluride TEG cell and another module consisting of two TEG cells in a stacked configuration. The TEG cells were sandwiched between two copper blocks and connected to two plate-finned heat sinks and eight heat pipes. The two modules were tested on a dedicated test bench to study its performance based on an industrial WHR setup. The hot stream waste heat temperature was constant at 80 ℃ while the cooling air streams were set based on ambient conditions between 22 ℃ to 30 °C. The maximum power performance (MPP) varied from 10 mW to 153 mW where the effect of cooling is very significant on the power outputs. Under forced cooling condition, the MPP generated from the double stacking TEG configuration is significantly higher compared to single cell configuration, by approximately 250%.