Some stoves like the HARMEN (direct vent), will bring fresh air in and exhaust it out the same pipe. Pipe within a pipe.
Most other stoves, use ROOM air for the combustion blower, it sucks the air from the combustion blower from the same room and ONLY exhaust it out thru the Exhaust pipe/chimney pipe.
If you don't have the room for a chimney, you can either use a "POWER VENT", Mounted on the outside that PULLS the fumes out of the stove or a "DIRECT VENT", that mounts on the STOVE and PUSHES the fumes out the pipe (Pressurized pipe and needs sealed). (Keystoker stoves typically use this). Do a search on here for Power Vent vs. Direct Vent. Might explain better. Direct vent vs Power vent...
Why are you sayin a power is you last option, if you don't have the room or height for a standard chimney, you only have 2 options. Power vent or Direct Vent. Which basically do the same thing.