I currently live in an old farmhouse with an unfinished basement in northern wisconsin.  I was wondering if you could installl an air airsource heat pump in the basement?  My thoughts being that it is fairly large and horribly drafty (double trap doors going outside and loose single pane windows) but the temp rarely drops below 50f.  I am not very familiar with the air volume these units need but I don't think you could suck air out fast enough to create any vacuum.  Geothermal is out of the question because of our soil depth.

It would really cool down your basement and I would think quickly get it below the point where and air source would make sense temp wise (below freezing). Also if it did cool your basement to 30F or colder I would think it would cool the main floor of the home down as well, unless there is some major insulation in there. I know here at work we have a 5 ton unit in the basement (strictly cooling), but the basement is over 15,000 sq feet

When you say geo is out of the question due to soil depth is that a guess or is that what geo contractors told you?
J

It's a guess. The frost line hits bedrock on most of our property.

Estimates are free, let's start there.
j

My recollection from posts on here is bedrock is breakable by drilling if you go vertical. It could stop you from doing a cheaper horizontal install. Still - cheaper is relative. Either install method should cost you less than propane if you're going for a temperature that keeps you comfortable.