The paper presents a new concept of applying a rotary vane engine working as the hybrid system including both a combustion engine and a pneumatic motor, which were working simultaneously. In the beginning, review on both unconventional piston engine designs and similar like solutions on rotary vane engines were conducted. Next, description of the conceptual engine was presented. The concept was realized in practice. The prototype engine was built and it was preliminary investigated focusing on problems with cold start and misfiring events which occurred. The engine was tested on LPG and gasoline, however, its main target is to feed it with natural gas. This approach is justified as far as the engine finally might work in natural gas reduction stations and would provide electricity of 1kW power for station’s own demands.