Estimation of harvestable energy from vehicle waste heat

This paper presents modeling, simulation, and experimental estimation of harvestable green energy from the vehicle´s waste heat. Waste heat-flow through liquid-coolant and the exhaust gas are considered. We have developed two models, written in Matlab, to estimate energy in real-time from the coolant and exhaust. Heat power in kW is estimated as a function of mass flow rate, specific heat capacity, and temperature. Instantaneous heat power integrated over a drive cycle resulted in the estimated energy in kWh. We have obtained mass-flow rates and the coolant temperature from the recordings of the vehicle´s onboard diagnostic data (OBD). We measured exhaust-gas temperature wirelessly, in parallel with OBD data recording, using an infrared-temperature sensor and an Arduino-Uno microcontroller with Xbee-wireless-data-interface. The dynamic specific heat capacities of the exhaust gas and the coolant are estimated as the 5th-order polynomial functions of corresponding temperatures. We have found that the harvestable energy per hour of driving from the coolant is about 8.44 kWh in a city drive-cycle; and it is about 16.77 kWh of energy in a highway drive cycle. It is expected that about equal amount energy can be extracted from the exhaust gas.