A Vuilleumier cryocooler with a projected cooling capacity of 100 W at 77 K has been developed at the University of Canterbury in New Zealand. While most cryocoolers use mechanical compressors with associated vibration, leakage and lubrication problems, the Vuilleumier concept employs a thermal compressor with only a marginal mechanical work input requirement. This paper highlights its significant design advantages and presents results from a computer model that justifies this approach, despite the apparent disadvantage of the Carnot limitation arising twice.