There are fundamental thermodynamical limits to certain processes involving energy transfer, conversion etc. Heat transfer comes to mind. Those cannot be engine

There are fundamental thermodynamical limits to certain processes involving energy transfer, conversion etc. Heat transfer comes to mind. Those cannot be engineered away. For simple mechanical systems, yes, inefficiencies can be removed, but it's more like externalizing them. How is the vacuum created and maintained? That requires a compressor, an inherently not lossless machine.