Experimental Examination of Recovery by a Thermoelectric Generator of Heat Energy Lost to Engine Coolant in a SI Engine

Abstract

In this study, the recovery of heat energy lost to the engine coolant (Ec) in a liquid-cooled, gas-fueled (propane), spark ignition (SI) engine using a thermoelectric generator (TEG) is experimentally researched. A two-layer rectangular geometry TEG is designed, consisting of a propane heat exchanger (P_hex) located on the surface of an engine coolant heat exchanger (Ec_hex). 20 items of thermoelectric modules (TEMs), each 30x30 mm in dimensions, are placed between the Ec_hex and P_hex. In the TEG design, engine cooling fluid is used on the hot surface of the TEMs, and propane gas fed to the engine is used on the cold surface. In addition, with the use of the designed TEG, there is no need to use an additional evaporator for propane gas. Experiments are carried out with the designed TEG at 8 engine speeds ranging from 1500 to 5000 rpm. As a result, TEG produces 1.25–3.01 W of DC electrical power in the engine's 1500–5000 rpm range, while TEG efficiency fluctuates between 2.7 and 3.1%. However, the maximum TEG_power is 3.01 W at 5000 rpm, while the maximum TEG_efficiency is 3.1% at 1500 rpm. On the other hand, the electrical power of TEG between 1500 – 5000 rpm of the engine is approximately 1.1–1.26% of the engine charging system power. However, TEG's contribution to the charging system again decreases with the engine speed.