Joel's post about a 'Rovorx' or something like that sounded to me like 
a Wankel type compressor - especially the note about the seal life.

Dont know if this is right or not ???

Its a little sad when you realise there is no marketability for solutions
that require a yearly seal change, or the like, compared to more
expensive solutions that are intervention free (the whole industry
reflects this). Basically there arent many of us willing to 'put up' with
a car that needs tickling twice a year....oh well lets not go that
thread again ...