“…Regardless of the driving cycles, most of the time for a HEV system, the internal combustion engine (ICE) operating points are controlled as close as possible to the optimal operating points (OOP) or emissions at a particular engine speed known as the optimal torque region (Wirasingha and Emadi, 2011;Hu et al, 2013;Gökce and Ozdemir, 2014;Hou et al, 2014;Wu et al, 2016). In ICE, the fuel efficiency is not more than 30% where 60-70% of the energy is wasted in form of heat making development of waste heat energy recovery technologies like thermoelectric generators, six-stroke cycle ICE, turbochargers, and Rankine Cycle attractive and promising (Horrein et al, 2015;Zhou et al, 2017).…”