In colder climates winter storage crops have been stored in passive root cellars for centuries. Although modern refrigeration systems are generally used for large scale, longer-term storage of these crops some enterprises seek lower cost and high energy efficiency options. Outside air exchange systems use an exchange fan to draw colder outside air into a storage room to maintain a depressed temperature.
Tool Started 4-18-14. Last Updated 4-19-14 Apologies. This post is in progress. I can't find where to hide it while being developed, so I thought I would rush and add some content over the next few days.
Make note that the Arduino screw shield is not required. An electric imp however is required. Without the Arduino screw shield, you can make this complete circuit and start harvesting temperatures wherever you have internet access.