Heat-triggered high-performance thermocells enable a self-powered forest fire alarm

Harvesting heat from fire itself to power wireless sensor networks has the potential to realize effective detection and alarm for forest fires. Thermocells based on the thermogalvanic effect offer an inexpensive and scalable way for heat-to-electricity conversion but challenged by their low performance. We demonstrate a boosted thermogalvanic effect by introducing concentration gradients into a thermocell, achieving a one order magnitude enhancement of output up to 45.9 W m−2. Using a heat-triggered membrane as the start switch, a thermocell which can hibernate in peacetime and awaken when fire occurs, is further obtained. A proof-of-concept device integrated from five units successfully detects precombustion and open fire to synchronously generate a high voltage of ∼2 V for driving an alarm. This system shows promise for combating the globally increasing forest fires.