Anyone else feel like July is trying to kill us with the heat? Even ice cream stores have to figure out cooling problems from time to time! And for Sub Zero, science is a way of life! So what do our Sub Zero Scientists do when faced with a hot store front? Well, for a temporary solution, they cranked up the AC in the back to try to get it flowing to the front, but Sub Zero is about innovation and creativity! So once again, they put their minds to work figuring out a better way.
Jerry Hancock, the original Sub Zero Scientist, with his knowledge of geothermal heat pumps, considered the possibility of using a similar construction for cooling. As he was looking for solutions, he realized that in all the geothermal set-ups, they have a constantly running water source, like a stream. He realized the store, too, has a constantly running water source—the city water running in from the street that feeds all of the water fixtures in the store. It’s somewhat hard to calculate how much water a system might need, and Jerry was unsure the water running into the building would be enough to make a difference, but in true Sub Zero fashion, he figured it was worth the experiment.
Water is 600 times more condensed than air and is therefore much more efficient than air in transferring temperature, hot or cold. A water to air heat exchanger, then, is basically piping made of a conductive metal to run the water through, and lots of surface area so that when air moves across the cool piping, the air cools too. You’d feel a similar sensation if you were to put your hand on one side of some ice cubes and then blow across them toward your hand. The air hitting your hand would feel cold.
He researched on YouTube where other people had done similar things for cooling a garage, etc., and devised his plan. He got a water to air heat exchanger off of Ebay for $125, then used scrap wood he had lying around to craft a nice box to go over it. A box fan that had been used inefficiently to move cooler air toward the store’s front was turned into the blower. He turned the water off, cut into the water intake, routed the water through the exchanger, and then routed the water right back to its normal path. With the water turned back on and the repurposed box fan to blow the cooled air out, the contraption was completed. Now to see if the experiment would work.
The store front immediately began cooling down. There was no change in the water input, and it requires no electricity but the box fan they had already been running. They were able to save the energy from three other fans they unplugged which had been used to move air to the front. The back office AC didn’t have to work so hard to keep everything cool, so they were able to raise the thermostat setting three degrees. Talk about a step in the green direction! All utilizing a resource they already had flowing in, their city water, combined with some ingenuity, research, and pure science.
The differential is essentially free minus the upfront costs of the heat exchanger and the minimal electricity use of the box fan, but the savings are in the higher thermostat setting, which means less electricity usage from it turning on less often, fewer fans, and knowing this solution will last as it needs little maintenance.
Whoever said DIY had to be limited to home? Another win for the Sub Zero Scientists!
For the record, a contraption like this isn’t new. Large buildings like event centers and high schools often use geothermal heating/cooling systems. It’s because the earth, depending on latitude, has a nearly constant temperature of between 50–60°F once you get to about 20 ft down underground. This means that it can be used for cooling in the summer and heating in the winter. The trouble is that these systems usually use massive amounts of pipe in the ground for the water running through to settle at that comfortable temperature. This is where the city water helps so much. Ground water is 55°F, and so the city water flowing is 55°F. The city has basically already done the piping for us, therefore we were able to skip that step.
The hidden bonus of this system is that it provides cooling without any significant heat waste. That’s a lot more than traditional AC can say. Air conditioning uses the air outside and compression. Taking the hot air outside and cooling it takes a lot of energy. Usually freon is used, which as a liquid is really cold. Air blows over the pipes holding it to cool the air in a building. The evaporation of the freon is what makes it feel cold. But then the freon is in gas form and needs to be compressed back into a liquid. The compression makes it really cold again, but it has a lot of heat waste which is released outside.
So, with no significant heat waste, little energy usage, and a long-term solution, Sub Zero can feel good about their green step forward while appreciating the cooler environment and relishing ice cream out of the heat. Science for the win!