Taking advantage of several of the most modern research and development achievements in combustion technology, material science, control engineering, together with some unconventional thoughts on thermodynamics, a novel concept of a steam engine is presented, which is especially suitable for automotive engine applications. The paper starts by describing the general concept of the so-called Zero Emission Steam Engine, which includes supercritical thermodynamic states and high-pressure steam injection, and further focuses on the porous burner technology as the actual heat source of the process. Following a brief description of the principle of operation, the unique advantages of this novel heat source for the steam engine are outlined. These advantages include a wide, infinite variable power turndown ratio of about 1:20, which is roughly a factor of 5 greater than the modulation range of competitive burner technologies. Additionally, the porous burner excels by very low combustion emissions that are independent of the actual thermal load of the burner and are -at any state of operation -clearly below the most stringent Super Ultra Low Emission Vehicle (SULEV) standards. Another advantage of immense importance in mobile applications is the compactness of the porous burner units. Using superior heat transport properties, the porous burner allows power densities of about 3.000 kW/m², which is about a factor of 10 greater than the value of other premixed, low emission burner technologies, resulting in very small burner units. Finally, the porous burner technology allows complex combustion chamber geometries to be realized, which may be of special interest in applications where space is limited. Using these advantages, several porous burners for different concepts of ZEE-engines have been developed and are currently undergoing testing from which the results are presented in this paper. Although the presented prototypes are far from being mass-produced, the experimental results obtained from the prototypes clearly indicate that porous medium burners together with a modern steam engine concept can indeed be successfully applied to car engines and offer significant advantages compared to conventional state-of-the-art engines.