You might try buying two CPU coolers with fans and connect them together via their heat sinks with the fans pointing in opposite directions. Then build a housi

You might try buying two CPU coolers with fans and connect them together via their heat sinks with the fans pointing in opposite directions. Then build a housing for it to match your window. That should transfer some of the heat/cool from the outgoing air to the incoming air. Put a filter on it to keep bugs and pollen out of the house (including the outgoing fan because you might turn it off sometimes. It needs at least a no-see-um size mesh screen.)