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.
-Solar panel and batteries (taken from a IKEA SUNNAN lamp)
-Peltier element (taken from a camping cooler)
-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)
Step 1: Placing the solar panels
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).