Hi community, I would like to share a my experience with using an old food/drink cooler I found in my garage:
I was not afraid to destroy it in case the test failed, as nobody used it for ages. I was about to cook for 24 hours at 85°C. I was not sure that the plastic would not deform when exposed to such temperature
for that long. On the other hand, I also wanted to save some energy and reduce evaporation.
The cooler’s body actually consists of two containers of different sizes with the gap filled by polystyrene foam.
First I had to test the water levels:
As you can see, the container is pretty deep and the min/max levels were acceptable even when I used the clamp. I did want to use the lid though and I used a hole saw of a diameter of cooker for a good fit. Make sure that the hole is tight, so the cooker does not fall through. It is an electrical device, so make sure you test the fit when unplugged.
Here comes a catch: the lid also consists of two pieces of plastic, but unlike the container part, the space between the two parts is not filled with any material. That actually caused that the first layer I drilled/cut through cracked and later, wen cooking, the space around the hole got a bit deformed, as if collapsing, as there is literally nothing stiffening the lid’s layers around the hole:
The image also depicts the solution in operation. So whatever cooler you would use, make sure the lid is not hollow.
This is what the container looked like after being exposed to 85°C for 24 hrs:
Resume: I cannot judge or estimate the energy I saved over those 24 hrs. But once I turned the cooker off, it took about 6 hours to the water to lose half of its temperature. I will add some extra insulation/stiffening to the lid. I will use any suitable mounting foam in a spray to do it. It does not have to be food safe, as it does not get in contact with the food. I use vacuumed bags.
the container holds up to 21 liters of water, which makes it great when preparing larger or multiple pieces of food. I also appreciated that I can put the cooler (now a cooker) to a place where it did not interfere with other works in the kitchen.
the only downside is you do not see the food and, the more important is that before opening it, the cooker must be switched off and removed. The water temperature does not change that dramatically within a minute before you drop your bags inside. No stress (that’s what i love about sous-vide).
Hope this helps or serves anybody for inspiration or guidance. If you have any questions I did not cover, I will be happy to answer.