When we think of a battery, lithium and lead automatically come to mind, but the essential purpose of a battery is to store energy… and it doesn't necessarily have to be electrical. That brings us to the concept of a thermal battery, and to a very effective design like the sand battery. All you need is an electricity source and a heating element to heat the sand, which can reach 600 degrees Celsius under optimal conditions.
Our mobile devices devour batteries like candy, and deep down, we know the situation is getting worse. However, once we escape the limitations of formats, we discover that the possibilities for batteries are much broader and more interesting. For example, electrical energy is not the only thing we can store in them. Sometimes it's more useful to store heat, and that's how we arrive at the sand battery.
Anyone who has burned their feet on the beach knows that sand reaches an impressive temperature. If its container is properly insulated, in commercial designs it can even exceed 600 degrees Celsius. In practice, the temperature limit is not set by the medium, but by the building materials used. And speaking of building… would you like to make a sand battery?
How to Build a Basic Sand Battery
Robert Murray-Smith explains the process on his channel. In addition to the sand itself, all you need is a heating element (Robert extracts it from a water kettle), and a bit of electricity. The great advantage of the sand battery is that it doesn't have very high demands, and Robert uses a source set to 12V and 0.5A. With just six watts and a bit of patience, the sand reached 200 degrees Celsius, demanding extra protection in the form of gloves.
Now, how do we harness that energy? Robert recommends a copper coil to circulate and heat water inside it, but there is also the option of a Peltier module (which, by the way, is not that efficient), or why not, a Stirling engine. Adding a temperature switch or a thermostat controller to the setup is a very good idea, and they are not very expensive extras (between 5 and 10 euros).
