US Patent 7426910 Engine system having improved efficiency

A propulsion system for a vehicle, comprising of an internal combustion engine, a thermoelectric device in thermal communication with the engine, and a control system for controlling the engine and the thermoelectric device during a first mode, supply electrical energy to the thermoelectric device to cause the thermoelectric device to produce at least some heat, and during a second mode, operate the engine to produce at least some heat, where the thermoelectric device is operated to convert a temperature gradient at the thermoelectric device to electrical energy.