Homemade thermal battery system keeps the shop cool with Arduino
When trying to cool off a space, most people reach for an air conditioning unit that uses a pump, compressor, refrigerant, and a radiator to move heat from inside a room to the outside air. But in a break from this typical model, YouTuber Curtis in Seattle came up with a system that pumps water between a series of radiators/box fans and a set of five 55-gallon drums to move heat away from a room during the day.
Curtis employed an Arduino Uno to calculate temperatures via input from four DS18B20 sensors, activate relays, log data, and display the indoor, outdoor, battery, and ground measurements on an LCD module. The components are all housed in a vintage movie projector.
His setup, more commonly referred to as a thermal battery, works by first storing a large amount of sub-ambient water in a tank, or in this case, a series of daisy-chained drums buried about a foot underground and a couple of feet away from the wall. Then during the day when his shop begins to heat up, the cool water flows from the tanks and through a radiator, which uses a fan to draw warm air from inside the room and transfer its heat into the passing water. Over time, this can keep the room’s temperature at around 71 degrees Fahrenheit even when the outside temperature is several degrees above that. Owing to the name “thermal battery,” this system can then recharge overnight by releasing the heat within the barrels to the outside air using another radiator/fan.