Diesel engines used to drive transport refrigeration equipment, typically have a thermal efficiency of 40%. Assuming a heating value for diesel of 43.2 MJ/kg and a density of 820 kg/m3, the amount of energy rejected in the form of hot exhaust gases and thermal energy dissipated by the radiator for each litre of fuel that is used is 21.25 MJ/l or, 5.9 kWh/l. Recovering only a small portion of this “free” wasted energy to operate a thermally driven refrigeration system, would be more than enough to cover the refrigeration requirements of a semi-trailer.