Feasibility of IoT technology was evaluated by,
Learning Python to program an ESP32 kit (M5stickC)
Creating a closed-loop system with a temperature sensor
Linking to an app for remote control
Testing the Peltier module for designing a lunchbox with compartments for cold and warm meals.
It was disregarded due to its energy inefficiency.
Effective battery choice
(size vs weight)
Power requirements of the self-heating lunch-box were estimated by calculating the energy needed to heat up 850mL water from 5°C to 70°C. i.e. 66.6Wh with a 100W heating element powered for 40min.
Since 70Wh energy is available in 21700 x 4 cells or 18650 x 6 cells, either combination can be used.