The basic Sterling engine concept has been around since the late 19th century; SOMEDAY, someone is going to get it right. I'm 55, I'm NOT hoding my breath. I've seen the rotary piston (Wankel), the free piston, the gas turbine, the hydrogen-cycle engine, the fuel-cell, and on and on; they were all going to be THE answer to replacing the 4-cycle reciprocating piston engine; guess what we're still using.