Perhaps get ahold of some d2o. It freezes at 38.8°F so (I think) a 50-50 mixture of d2o & h2o would have it's phase change right in the middle @ 35°F. That's an

Perhaps get ahold of some d2o. It freezes at 38.8°F so (I think) a 50-50 mixture of d2o & h2o would have it's phase change right in the middle @ 35°F. That's an ideal point for refrigeration, and a phase change thermal mass battery has a lot more capacity.