Some embodiments provide a waste heat recovery apparatus including an exhaust tube having a cylindrical outer shell configured to contain a flow of exhaust fluid; a first heat exchanger extending through a first region of the exhaust tube, the first heat exchanger in thermal communication with the cylindrical outer shell; a second region of the exhaust tube extending through the exhaust tube, the second region having a low exhaust fluid pressure drop; an exhaust valve operatively disposed within the second region and configured to allow exhaust fluid to flow through the second region only when a flow rate of the exhaust fluid becomes great enough to result in back pressure beyond an allowable limit; and a plurality of thermoelectric elements in thermal communication with an outer surface of the outer shell.