# Shine7.com

## DIY Aquarium Chiller

This aquarium chiller uses a 15V 15A peltier to cool my 20 liter fish tank. In my setup, I set the input voltage to 11V, so that the peltier generate less heat and operate at higher efficiency. There is a very useful peltier calculator that could help you to determine the optimum peltier operation point :

My design goal is to lower 6 degree of water temperature. To use the peltier calculator, there are several parameters that I need to determine : Input Voltage, Heat load and the peltier hot side temperature.

Input Voltage - I tried 12V and 11V on the calculator to see the difference between the heat generated, and found using 11V should be able to cool the aquarium while less heat is generated.

Heat load - This would means the engergy gained by the aquarium water from the ambient temperature. To find this out, I did a measurement of how much time is required to heat up the 20 liters tank water by 0.1 degree. First I used a fan to cool down the water temperature to 2 degree below ambient and then stop then fan. After 6 minutes the water temperature rised 0.1 degree.

# Heat Load = Energy / Time = 8360 / 360 = 23W

So for a 2 degree temperature difference equals to 23W from the ambient, I estimate for a 6 degree difference, the ambient heat load will be 69W.

Hot side temperature - This would equals to ambient temperature + heatsink efficiency * total heatsink load. I assume the ambient temperature to be 32 degree, the total heatsink load from the calculator to be about 200W. Now to find out the heatsink efficiency, I refer to this CPU cooler review link for the Thermalright Ultra-120 cpu cooler, which is the previous version of the Venomous X: http://www.frostytech.com/articleview.cfm?articleid=2001&page=5 . From the test results, the test load gained 12.4 degree for 125W of heat. That means the heatsink's thermal resistance is 0.1 degree per watt. The calculated hot side temperature will be 32 + 0.1 * 200 = 52 degree.

The TEC calculator shows that with the above parameters, the peltier cold side temperature is at 18 degree, which verify this design is good for a drop of 6 degree. If I try the above calculations again for an 8 degree drop, the calculated peltier cold side temperature will be at 31 degree, which means the design won't work for a 8 degree drop.

This calculation also showed that the importance of using a good heatsink, if a heatsink with 0.3 degree per watt thermal resistance is used, the temperature drop will only be good for about 3-4 degree.