DIY Peltier based Mini Refrigerator

How to build a peltier based mini fridge

Have you ever wondered if there is a portable mini fridge to cool water, drinks and juices during your summer outings?


Air conditioner cooling is the most common method of cooling in a refrigerator or room. But this is a tedious process that requires a great deal of electrical power and bulky electrical appliances to do the job.

Fortunately, it is possible to make a refrigerator that keeps food cold using a portable DC battery and something called the Peltier effect.


What is the Peltier effect?

Thermoelectric coolers or Peltier effect devices are relatively small devices used for cooling or heating. Peltier appliances use DC (direct current) for cooling, unlike traditional refrigerators or air conditioners that use AC current. The Peltier effect is a process in which, if direct current is passed through a circuit with two conductors of different materials, heat is removed from one junction, making it cold, and the other junction absorbs heat, making it hot.

It can also be seen that if the polarity of the current is reversed, the junction that was previously cold becomes hot; While the junction that was hot before the current polarity was reversed, becomes cold.

Use Peltier thermocouples to control the temperature

The above phenomenon creates an opportunity to design a device that can extract and remove heat. If you place the cooler junction on the hot surface or device from which the heat needs to be extracted, and the hotter junction goes to heat sink-You can keep the surface or device cool. Not only that, but you can maintain a continuous optimum temperature for good performance.

How to build a DC mini fridge

DIY Peltier refrigerator components

We will use the above concept to design a DC refrigerator. The mini fridge is the target design, however, and can be scaled down to a medium sized fridge using several Peltier effect appliances using the same technology.

What you will need

The required equipment is as follows:-

  • Peltier module (TEC1-12706) with connecting wires.
  • Two heat sinks.
  • 12V DC battery or DC power supply.
  • A box (the inner part must be a non-thermally conductive material such as wood, cardboard, or styrofoam)
  • Two Delta Electronics FFB0412HN fans on forced convection heat sink fins
  • thermal paste
  • Electrical wires

The Peltier thermoelectric cooler that we are using here is a DC driver with an ideal operating voltage of 12VDC and a current draw of approximately 6A (72W). The operating voltage should not exceed 15V DC. Do not operate the Peltier device without a heat sink. If used even momentarily, it may exceed the maximum operating temperature of the device link and lead to performance degradation or complete failure of the device.

Step 1: Prepare the box

Now take an empty box of insulating material. For this demo, we used cardboard. Make a hole or cavity according to the dimensions of the Peltier TEC1-12706 (i.e. 40 mm x 40 mm) for the design of the mini fridge. Place the Peltier device directly over the cavity you created in the box

Step 2: Place the heat sinks on the Peltier device

Now place the heat sinks over the junctions of the peltier device. Each junction of a peltier device is connected to a heat sink Using high conductivity thermal paste. Thermal paste ensures smooth heat flow between each peltier junction and the heat sink base plate, while not allowing the hot junction to get too hot and the cold junction to get too cold to damage any of the connections.

The heat sink increases the efficiency of the Peltier device by keeping the air flowing evenly. This is due to the increased heat exchange between the surrounding air and the Peltier device due to the large surface area provided by the heat sink to extract heat from the inner junction and remove heat through the outer junction. For a good design, heat sinks with larger fins and a larger surface area are recommended.

Step Three: Attach the Propellers

Attach now Your choice of fan On each heat sink fin. The forced convection provided by the fan increases the speed of airflow through the heat sink fins, allowing more heat to be extracted.

Mounting the mount on the box

The fans used in this project are 12V DC brushless (Delta Electronics FFB0412HN) with airflow of 10.6 CFM. Each fan consumes less than 1 watt of battery power. However, one can use a fan with a larger airflow for better performance.

Attach a heat sink fan

Be careful not to connect the junctions of the device through a metal interface such as the screw on the heat sinks, to avoid short circuit in the thermal connections. This can greatly degrade the performance of the peltier appliance refrigerator, as the heat flow may get the shortest path through the metal screw, etc.

In the event that the screws cannot be fixed due to a thermal short circuit between two heat sinks, you can use glue to attach the heat sinks to the box. However, it is necessary to use heat sink paste between the heat sink and the peltier device.

Step 4: Turn on the power using 12V DC

Now connect the jumpers of the Peltier device and the propellers wires to the 12 VDC battery. The battery must have the current capacity to provide 7A DC current. A 10Ah battery or more will suffice for this single Peltier fanned unit. Adjust the voltage polarity of the device’s connections so that the inner side of the box becomes cooler and the outer side becomes hot, ducting heat out of the box for cooling.

Now connect the wires to the battery to allow the device to take current. Closely monitor the current drawn from the battery. It must be within the limits specified by the Peltier device manufacturer. Allow the system to take current for some time and monitor voltage and current to safe limits.

After a few moments, you will feel the coolness of the air inside the box. You can add bottled water and juices to keep them cool. Now cover the box to use it as a mini fridge. For a reliable operation, you can Add a temperature controller To protect the Peltier device from exceeding operating limits.

You made your own mini fridge

Now you can build your own mini fridge using Peltier devices and a few other simple components. Peltier effect units can also be used to control temperature for applications such as cooling in electronic devices, circuits and systems that require a low budget and lightweight cooling system.

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