We’ve been dreaming about building a root cellar for years now. Ever since we heard about a passive freezer that was built using thousands of soda bottles, we’ve been thinking about how we could incorporate ice into a root cellar design to make the useful cooling period last throughout the year. I’m happy to say that we are now on our way to making that dream reality, but we can use your help! We’ve just launched a crowd funding campaign on Indiegogo to support our Passive Cooler project.
We don’t currently have a cooler or a root cellar, but make do with a combination of storage in an extra fridge, a friend’s root cellar, and cold spots in our house. We’d like to be able to have enough winter storage space to offer a CSA share over the winter months, comprised of: storage veggies, sprouts, hardy greens from the hoop house, and possibly some of our other products such as teas, syrups, and dried mushrooms. As our business grows and the fruits we have planted mature, we are also in need of a cool space over the summer months. With the help of our friends David Maynard and David Ludt we’ve come up with a plan for a year round cool storage space without the use of electricity and without hauling in tons of ice or thousands of soda bottles.
The root cellar will be a 16x16x8 foot poured cement foundation dug into a side hill. The root cellar’s cooling time period will be expanded beyond the winter months with the addition of tanks of water inside the cellar that will freeze from the inside out when outside air temperatures are 31ºF or below, utilizing a passive heat exchange system of copper pipes filled with butane. The frozen tanks will slowly melt during the warmer months, cooling an enclosed space within the cellar that can be used as a walk in cooler. Once built, the passive cooler should continue to operate without the need for a power source, saving emissions and dollars.
Here’s How it Works
Butane boils at 31ºF. When the copper pipes containing butane are in contact with air or water that is above 31ºF, the butane will boil and become a gas that will rise to the top of the sealed pipe which is outside the root cellar. If the temperature outside is below 31ºF the butane gas will condense back into a liquid and drop down to the bottom of the pipe array inside the water tank. If the water in the tank is above 31ºF the butane will once again boil and condense, starting a cycle that will continue as long as the water temperature is above 31ºF and the outside air temperature below 31ºF. Each time the butane is boiled by the water tank temperature, heat is transferred from the water, cooling, and eventually freezing the whole tank starting from the inside out.
We Can Use Your Help!
If you haven’t already, please go to our Indiegogo Campaign page and make a donation if you are willing and able. Also, please help us spread the word by sharing the link through your social media and email contacts. We think the passive cooler concept is an idea that could serve a lot of small farms and the planet well. Your support of this research will help us to share it!