Can I use a refrigerator that's been disconnected for a year?
If you empty out a fridge and unplug it, you will return to find a massive mold colony inside the fridge.  It is very important when taking a fridge out of service to block the door open and leave it that way for at least a month or two.  

This allows the interior (and nooks and crannies and insulation which might be wet behind the interior plastic liner) to thoroughly dry out.  Assuming himidity is reasonably low at that point, you can then close the door and should be able to store it door closed.