Abstract: There is provided a compact turbine-compressor assembly 25. The turbine-compressor assembly 25 includes a turbine wheel 39 with one or more turbine blades 41 and a compressor wheel 47 that includes one or more compressor blades 49. The compressor wheel 47 is concentric with the turbine wheel 39. Furthermore, the compressor wheel 47 and the turbine wheel 39 are not located at opposite ends of a common axle with a medial portion of the axle distancing them apart, as is the case with prior art turbine-compressor assemblies that are known. In contrast, the turbine wheel 39 and the compressor wheel 47 are located adjacent to each other and in one embodiment they axially overlap each other so that one nests within the other to thereby provide a compact arrangement. The turbine-compressor assembly 25 includes a first fluid path 67 which is configured to convey fluid, which will typically be air, through the turbine blades 41.