Introduction: Quad Heat Pump Peltier Cooler!

Picture of Quad Heat Pump Peltier Cooler!

This diy electric cooler originally used a single 60watt, 12volt Peltier. It was very convenient for storing cold groceries and vegetables until I reached home. I however wanted a more efficient version. I achieved this by undervolting the Peltiers to 3v each to reduce waste heat.

Read on for how I made an improved Peltier cooler using 4 Peltiers wired in series. This new version has a higher coefficient of performance and uses only 15watts!

Step 1: The Multi Heat Pump Modules.

Picture of The Multi Heat Pump Modules.

I have two heat pumps each having 2 Peltiers. I tested each Peltier at 1volt to ensure they were good. These pull 0.5amp at that test voltage. Only one Peltier from the box pulled less than that value so I couldn't use it in this project.

It is very important to test the Peltier prior to installing.

Step 2: Mounting the Heat Pumps.

Picture of Mounting the Heat Pumps.

Using the existing opening on the lid of my electric cooler, I fitted the two heat pumps and secured them. On the inside of the lid are the cold side heatsinks.

Step 3: Agitator Fan.

Picture of Agitator Fan.

This tiny low powered fan is used to stir up the air inside the cooler to accelerate cooling. It uses less than 1 watt which is good since any higher will introduce too much waste heat.

Step 4: Cooling Fan.

Picture of Cooling Fan.

I used an axial fan to blow ambient air over the hot side heatsinks.

Step 5: Insulation.

Picture of Insulation.

I used strips of foam to insulate the cold side heatsinks. I wanted no voids between those heatsinks and the lid.

Step 6: Temperature Sensor.

Picture of Temperature Sensor.

The digital thermometer on the lid takes measurements via this sensor I secured under the lid. Mind you, the temperature that will be read will be a worst case since warmer air stays near the top.

Step 7: Performance.

Picture of Performance.

At 12 volts, the consumption is approximately 15watts. The lowest temperature achievable is 21C which is very good at an ambient of 29C. Peltier coolers cannot freeze such an empty void but if previously chilled food is placed in it, it will keep the food cold in hot weather.

As a little safety feature, I powered the cooler via 20 second delay ON timer relay so the car won't power this while it is trying to start.

Comments

GordonS6 (author)2017-09-14

The temperature differential is very modest with your setup, but the energy savings is substantial! A Peltier module should be capable of up to 40 degrees F differential at full power. I suggest that stacking these four modules would produce close to that differential and use the same amount of power (15 watts), but would probably take a little longer to achieve maximum differential. Nice work!

lourens01 (author)GordonS62017-09-14

Can you please elaborate on the "stacking"? My understanding is putting one on top of the other, but I cannot work out how that would work physically and in terms of the interaction between the two. So I am probably wrong in my assumption that stacking refers to one on top of the other.

GordonS6 (author)lourens012017-09-15

Indeed, stacking means to place one directly on top of another with thermal conductive grease between. I don't know how many could be successfully stacked, but I'm pretty sure that four would provide a much greater temperature differential. But the total number of calories transferred would remain about the same. Given sufficient time, the stacked modules should make the interior of the insulated box much colder! I think the limiting factor would be how much temperature the modules could withstand and still function properly. The top one in a stack would be pumping from the rather warm one beneath it. This method is used in some thermoelectric coolers for astronomy cameras to reduce temperature generated noise in the camera sensor.

Mjtrinihobby (author)GordonS62017-09-14

Thanks.

grayl (author)2017-09-13

You might also try mounting the fan motor outside the cooler, with the circulating fan inside. That may save a few degrees.

Mjtrinihobby (author)grayl2017-09-13

Good idea.

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