Warmer means faster maturation, colder means slower. At 45F you aren't going to get much microoxidation or concentration since little liquid is evaporating through the pores of the wood. It will pick up some wood tannins though, I don't see that slowing because of cold temps.
I think it might be better done at 55-60F. Thats optimal for wine. Of course this is for a 50gal barrel, the small barrels have larger surface/volume ratios and everything happens faster so you might be OK slowing things down with refrigeration.