Foam or plywood window insert this method uses the window vent insert that comes with the portable air conditioner coupled with a piece of rigid foam or plywood to block the rest of the window.
Casement window portable air conditioner vent.
Gulrear portable air conditioner window vent kit window slide kit plate for portable air conditioner adjustable length portable ac vent kit for exhuast hose of 13cm 5 1 inch 4 3 out of 5 stars 445 39 96 39.
Although most portable air conditioners come with a traditional window kit you can absolutely fabricate an insert to fit into the casement window allowing you to vent your portable air conditioner.
It works by taking in air from a room cooling it and directing it back into the room venting warm air outside through an exhaust hose.
This would also work if you want to install an air conditioner in a sliding window as well.
A portable a c unit also known as a stand up air conditioner is a versatile alternative to central air conditioners and window units.
You can see how one homeowner did it in the video below.