Instructables
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Summer or winter, some lunches taste better when they're cool and fresh, other when they're hot.
To be able to heat/cool your lunch wherever you are, I made a solar heated/cooled lunch box.
The solar panels charge the batteries, hidden below it.
Half an hour before lunch starts, you press the switch, either to heat or to cool.
The power of the batteries heats up or cools down the Peltier element at the bottom of the lunch box.

Components:

-Solar panel and batteries (taken from a IKEA SUNNAN lamp)
-Peltier element (taken from a camping cooler)
-Lunch box
-Switch with 3 positions (has to be able to switch polarity)
-2 metal plates (cut out of a biscuit box)
-2 polystyrene sheets (material of a CD jewel case)
-Soldering iron
-Glue
 
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Step 1: Placing the solar panels

Picture of Placing the solar panels
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Draw the contour of the solar panels on the upper side of the lunch box.
Remove the inside of the contour with a cutter.
Place the solar panels.
Fix the panels to the top with glue (I prefer a glue gun).

Step 2: Placing the switch

Picture of Placing the switch
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Draw the contour of the switch on the upper side of the lunch box.
Remove the inside of the contour with a cutter.
Place the switch.

Step 3: Placing the Peltier element

Picture of Placing the Peltier element
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Draw the contour of the Peltier element on the bottom of the lunch box.
Remove the inside of the contour with a cutter.
Glue the first metal plate on the bottom.
Glue the Peltier element inside the removed contour onto the first metal plate.
Cut out a sheet of insulation and place it around the Peltier element.
On top of the Peltier element, place the second metal plate. (These plates conduct the heat and spread it)
When everything is in place, make sure the wiring is correct and the Peltier element works (both heating and cooling).

Step 4: Placing the polystyrene sheets

Picture of Placing the polystyrene sheets
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Glue a sheet of polystyrene (or any other plastic that is safe to be in contact with food) on top of the second metal plate and seal up the sides by melting it with an old soldering iron.
Repeat the previous step for the top of the lunch box.

Please give me a diagram!!

mscookieninja2 months ago

So how much did this cost to make? And could I just buy a eBay solar panel instead of the Sunnan solar panel? But I guess I would have to buy the rechargeable batteries then too if I got it off eBay. How did you hook up the wires? Like which wires go where? lol. Could you do this on a bigger cooler? Would you have to have a bigger solar panel than? Sorry for all the questions but I really have no clue when it comes to wires and making things haah. I just wanted to make this for my bf who does road construction and needs cold drinks on really hot days without the use of electricity. Plus I don't have a soldering iron... do I really need one? What could I do instead? Thanks!(:

simonvp (author)  mscookieninja2 months ago

It didn't cost me anything, as I took all the components of scrap parts and used a regular lunchbox I had lying around. You can just buy a solar panel on eBay, just make sure it isn't too big and can charge your batteries. The problem with buying a regular solar panel is that you still need the components that charge your batteries (in the Sunnan solar panel they're already built in..) It's hard to explain wiring via text. Best thing is to ask it to someone you know, who knows something of electronics.. A soldering iron is strongly recommended. You kan also try to wrap the wires around each other and the components if that works out!

simonvp (author)  mscookieninja2 months ago

It didn't cost me anything, as I took all the components of scrap parts and used a regular lunchbox I had lying around. You can just buy a solar panel on eBay, just make sure it isn't too big and can charge your batteries. The problem with buying a regular solar panel is that you still need the components that charge your batteries (in the Sunnan solar panel they're already built in..) It's hard to explain wiring via text. Best thing is to ask it to someone you know, who knows something of electronics.. A soldering iron is strongly recommended. You kan also try to wrap the wires around each other and the components if that works out!

acuchetto1 year ago
I can't tell how the heating element is prevented from melting the plastic and/or insulation.
simonvp (author)  acuchetto1 year ago
Hi! The Peltier element heats up to about 70° celsius. Polystyrene has a glass transition temperature of 95° celsius so no melting problems here!