Something else you can try is to dry (dehydrate really) them in a frost free freezer. I have not done this with sweet potato but I have with cheddar cheese and bits of meat. I am guessing that with sweet potato you might wan to cut them fairly thinly but all other preliminary preparation is the same. Also use mesh screen so air can circulate.
It will take even longer but if there is unused space in your frost free freezer they can just sit there for weeks or months till you want them and no extra energy cost, or not much.