Electricity generation from an exhaust heat recovery system utilising thermoelectric cells and heat pipes

• Car exhaust heat recovery design.
• Unique design that utilises heat pipes and thermoelectric cells.
• System is solid state and passive.
• The electrical power produced was 6.03 W.
• The resultant efficiency of the system was 1.43%.

The internal combustion engine used in majority of cars at the present time do not use their fuel input very efficiently. A majority of this energy is dissipated as heat in the exhaust. The related problems of global warming and dwindling fossil fuel supplies has led to improving the efficiency of the internal combustion engine being a priority. One method to improve the efficiency is to develop methods to utilise heat in car exhausts that is usually wasted. Two promising technologies that were found to be useful for this purpose were thermoelectric cells (TECs) and heat pipes. Therefore this project involved making a bench type, proof of concept model of power production by thermoelectric cells using heat pipes and hot engine exhaust gases. 8 cells were used and managed to produce 6.03 W when charging the battery. The system operated with a heat to electricity conversion efficiency of 1.43%. The discrepancy between the actual efficiency and the predicted efficiency of 2.31% is most likely due to the cells not operating at their optimum voltage. The predicted efficiency is approximately 1/9 of the Carnot efficiency and the actual efficiency is approximately 1/15 of the Carnot efficiency.